阅读说明：本技术 遥控水下机器人rov的直流降压变换装置及其控制方法 (Direct-current voltage reduction conversion device of remote control underwater robot ROV and control method thereof ) 是由 彭勃 张定华 刘可安 尚敬 刘浩平 张向阳 杨鸣远 徐绍龙 陈智豪 肖伟 廖津余 于 2020-10-30 设计创作，主要内容包括：本发明提供了一种遥控水下机器人ROV的直流降压变换装置,包括多个并联的直流变换模块,该多个直流变换模块彼此通信地连接,每个直流变换模块平均负担负载电流为ROV供电,该直流变换模块包括预定数目p个串联的Buck单元以及均流均压控制器,其中每一个该直流变换模块的该均流均压控制器配置用于基于所有直流变换模块的输出电流值和当前直流变换模块的电压输出值确定均流控制量,基于当前直流变换模块的自低压端至高压端的p-1个Buck单元的飞跨电容的电压值与对应的目标参考值确定p个均压控制调节量,以及基于该均流控制量和该p个均压控制调节量对当前直流变换模块执行均流控制和均压控制。(The invention provides a direct current voltage reduction conversion device for remotely controlling an ROV (remote operated vehicle) of an underwater robot, which comprises a plurality of direct current conversion modules connected in parallel, the plurality of DC conversion modules are communicatively connected to each other, each DC conversion module is configured to averagely carry a load current to power the ROV, the DC conversion module comprises p Buck units in series connection with a preset number and a current-sharing and voltage-sharing controller, wherein the current-equalizing and voltage-equalizing controller of each DC conversion module is configured to determine current-equalizing control quantities based on output current values of all DC conversion modules and a current voltage output value of the DC conversion module, determine p voltage-equalizing control adjustment quantities based on voltage values of flying capacitors of p-1 Buck units from a low-voltage end to a high-voltage end of the current DC conversion module and corresponding target reference values, and executing current-sharing control and voltage-sharing control on the current direct current conversion module based on the current-sharing control quantity and the p voltage-sharing control regulating quantities.)

1. A dc step-down converter for remotely controlling an ROV of an underwater robot adapted to be connected to an above-water high voltage dc power supply through a cable and to supply power to the ROV, the dc step-down converter comprising:

a plurality of parallel DC conversion modules communicatively connected to each other, each DC conversion module evenly burdening a load current to power the ROV, the DC conversion modules including a predetermined number p of Buck units connected in series and a current-equalizing and voltage-equalizing controller,

wherein the current-sharing and voltage-sharing controller of each of the DC conversion modules is configured to:

the method comprises the steps of determining current-sharing control quantity based on output current values of all direct current conversion modules and voltage output values of the current direct current conversion modules, determining p voltage-sharing control adjustment quantities based on voltage values of flying capacitors of p-1 Buck units from a low-voltage end to a high-voltage end of the current direct current conversion modules and corresponding target reference values, and executing current-sharing control and voltage-sharing control on the current direct current conversion modules based on the current-sharing control quantity and the p voltage-sharing control adjustment quantities.

2. The dc buck converter according to claim 1, wherein the current-share sharing controller is further configured to:

subtracting the current output current value of the direct current conversion module from the average value of the output current values of all the direct current conversion modules to determine a first current error value, and performing current sharing regulation on the basis of the first current error value to output a voltage regulation quantity;

subtracting the current output voltage value of the direct current conversion module from the output voltage reference value and adding the voltage adjustment amount to determine a first voltage error value, and performing voltage adjustment based on the first voltage error value to output a direct current reference value; and

and subtracting the current output current value of the direct current conversion module from the direct current reference value to determine a second current error value, and executing current regulation based on the second current error value to obtain the current sharing control quantity.

3. The dc down converter of claim 2, wherein the current sharing regulation and the current regulation comprise current-based PI control, and the voltage regulation comprises voltage-based PI control.

4. The dc buck converter according to claim 1, wherein the current-share sharing controller is further configured to:

subtracting respective voltage values from respective target reference values of flying capacitors of the p-1 Buck cells to determine p-1 second voltage deviation values, and performing voltage regulation based on the p-1 second voltage deviation values to obtain an error signal vector u ═ u₁,u₁,…,u_p-1]^T；

For the error signal vector u ═ u₁,u₁,…,u_p-1]^TPerforming a decoupling operation to obtain a voltage sharing control adjustment amount delta d for the 1 st to P-1 st flying capacitors_iI-1, 2, …, p-1; and

calculating the voltage-sharing control adjustment quantity of the pth flying capacitor

5. The DC buck converter apparatus according to claim 4,

6. the DC Buck converter according to claim 4, wherein the voltage regulation includes voltage-based PI control, and the voltage-sharing control regulation amount and the current-sharing control amount include duty cycle signals for switching transistors of the p Buck units.

7. The dc Buck converter according to claim 1, wherein the current-share sharing controller is further configured to add the p sharing control adjustment amounts to the current-share control amount to obtain an integrated control amount for the p Buck units.

8. The dc buck converter according to claim 1, wherein the plurality of dc converter modules communicate via an EtherCAT communication bus.

9. The dc buck converter according to claim 1, wherein each of the plurality of dc conversion modules is connected to the high-voltage dc input and the low-voltage dc bus via a respective input and output switch, and each dc conversion module is de-energized in the event of a failure of the dc conversion module.

10. The dc down converter as recited in claim 1, wherein each dc conversion module employs a multi-level Buck series topology with input and output common to ground.

11. The dc buck converter apparatus of claim 1, further comprising:

the filter is used for filtering higher harmonics of the output voltages of the p Buck units; and

and the protection circuit is used for overvoltage protection.

12. A control method of a dc step-down converter of a remotely controlled ROV, the dc step-down converter comprising a plurality of dc conversion modules connected in parallel, the plurality of dc conversion modules being communicatively connected to each other, each dc conversion module being configured to carry an average load current to power the ROV, the dc conversion modules comprising a predetermined number p of Buck units connected in series and a current-sharing voltage-sharing controller, the control method comprising:

determining current-sharing control quantity based on the output current values of all the direct current conversion modules and the voltage output value of the current direct current conversion module;

determining p voltage-sharing control adjustment quantities based on voltage values of flying capacitors of p-1 Buck units from a low-voltage end to a high-voltage end of a current direct-current conversion module and corresponding target reference values; and

and performing current sharing control and voltage sharing control on the current direct current conversion module based on the current sharing control quantity and the p voltage sharing control regulating quantities.

13. The control method of claim 12, wherein the determining the current share control amount comprises:

subtracting the current output current value of the direct current conversion module from the average value of the output current values of all the direct current conversion modules to determine a first current error value, and performing current sharing regulation on the basis of the first current error value to output a voltage regulation quantity;

subtracting the current output voltage value of the direct current conversion module from the output voltage reference value and adding the voltage adjustment amount to determine a first voltage error value, and performing voltage adjustment based on the first voltage error value to output a direct current reference value; and

and subtracting the current output current value of the direct current conversion module from the direct current reference value to determine a second current error value, and executing current regulation based on the second current error value to obtain the current sharing control quantity.

14. The control method of claim 13, in which the current share regulation and the current regulation comprise current-based PI control, and the voltage regulation comprises voltage-based PI control.

15. The control method of claim 12, wherein said determining p equalization control adjustments comprises:

subtracting respective voltage values from respective target reference values of flying capacitors of the p-1 Buck cells to determine p-1 second voltage deviation values, and performing voltage regulation based on the p-1 second voltage deviation values to obtain an error signal vector u ═ u₁,u₁,…,u_p-1]^T；

For the error signal vector u ═ u₁,u₁,…,u_p-1]^TPerforming a decoupling operation to obtain a voltage sharing control adjustment amount delta d for the 1 st to P-1 st flying capacitors_iI-1, 2, …, p-1; and

calculating the voltage-sharing control adjustment quantity of the pth flying capacitor

16. The control method according to claim 15,

17. the control method of claim 15, wherein the voltage regulation comprises voltage-based PI control, and the voltage-sharing control amount and the current-sharing control amount comprise duty cycle signals for switching tubes of the p Buck units.

18. The control method according to claim 12, wherein said performing flow control and voltage-sharing control on the current dc conversion module based on the current-sharing control amount and the p voltage-sharing control adjustment amounts comprises:

and adding the p voltage-sharing control adjustment amounts and the current-sharing control amount to obtain a comprehensive control amount for the p Buck units, and performing current-sharing voltage-sharing adjustment on the p Buck units.

19. A control device of a direct current step-down converter of a remote control ROV comprises:

a memory; and

a processor coupled to the memory, the processor configured to perform the control method of any of claims 12-18.

20. A computer readable medium having computer readable instructions stored thereon, which when executed by a processor implement the control method of any one of claims 12-18.

Technical Field

The invention relates to a power supply and driving technology of a remote control underwater robot, in particular to a direct current voltage reduction conversion device of a remote control underwater robot ROV and a control method thereof.

Background

Remote Operated Underwater Robots (ROVs) are powerful tools for today's mankind to explore the marine environment and to develop marine resources. Compared with the traditional hydraulic ROV, the electric ROV has more advantages, such as small weight and size of the system, and effectively reduces the power and size of the LARS system on the ship deck; the assembly is easy to be integrated into group rotation and disassembly, and is convenient to move and transport; the underwater operation system is excellent in operation performance and simple in operation, underwater working capacity is effectively improved, and maintenance labor cost is reduced; the oil stain leakage risk is small, and the environmental protection and the regulation evaluation are facilitated; the intelligent functions of navigation, control, operation and the like are easier to integrate, and the method has a technical foundation for upgrading to the AUV. In summary, the advantages of lower maintenance cost, higher reliability and efficiency, thinner and cheaper umbilical cables, and less risk of environmental pollution make the electric ROV the development direction of the next generation ROV technology.

With the continuous expansion of the application field, the ROV is also developed towards the direction of longer continuous working time, more flexible control maneuverability and larger propelling power, so that the ROV (especially working-grade ROV) has higher and higher requirements on energy and power. The power supply required by the working-grade ROV is basically and completely transmitted by the ship-side power supply device through the long-distance umbilical cable, and in order to meet the requirement of deep sea operation, the umbilical cable used for supplying power and communicating for the ROV underwater usually can be more than 3000 meters, and even can be as deep as 10000 meters and more. In order to reduce the resistance of the ROV to underwater movement, it is desirable to use as small a cable diameter as possible. The loss of the slender cable in the working process is very serious, the transmission efficiency is low, and meanwhile, the topological structure and the working mode of the ROV underwater converter are greatly influenced by the mode of transmitting electric quantity, so that the weight and the size of the underwater power converter are larger.

ROV compact structure, electric parts such as inside propeller, instrument need adopt low pressure direct current power supply, are restricted to underwater robot and maintain and maintenance cost high grade reason simultaneously, therefore need an urgent need for a volume weight, efficient, possess redundant function's underwater direct current conversion device.

Disclosure of Invention

The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

According to an aspect of the present invention, there is provided a dc step-down converter for an ROV of a remote-controlled underwater robot adapted to be connected to a high-voltage dc power supply device on water through a cable and supply power to the ROV, the dc step-down converter comprising:

a plurality of parallel DC conversion modules, the plurality of DC conversion modules are connected with each other in a communication way, each DC conversion module averagely bears load current to supply power for the ROV, the DC conversion module comprises a predetermined number p of Buck units which are connected in series and a current-equalizing and voltage-equalizing controller,

wherein the current-equalizing and voltage-equalizing controller of each of the dc conversion modules is configured to:

the method comprises the steps of determining current-sharing control quantity based on output current values of all direct current conversion modules and voltage output values of the current direct current conversion modules, determining p voltage-sharing control regulating quantities based on voltage values of flying capacitors of p-1 Buck units from a low-voltage end to a high-voltage end of the current direct current conversion modules and corresponding target reference values, and executing current-sharing control and voltage-sharing control on the current direct current conversion modules based on the current-sharing control quantity and the p voltage-sharing control regulating quantities.

In one example, the current-share voltage-sharing controller is further configured to:

subtracting the current output current value of the direct current conversion module from the average value of the output current values of all the direct current conversion modules to determine a first current error value, and performing current sharing regulation on the basis of the first current error value to output a voltage regulation quantity;

subtracting the current output voltage value of the direct current conversion module from the output voltage reference value and adding the voltage adjustment amount to determine a first voltage error value, and performing voltage adjustment based on the first voltage error value to output a direct current reference value; and

and subtracting the current output current value of the direct current conversion module from the direct current reference value to determine a second current error value, and executing current regulation based on the second current error value to obtain the current-sharing control quantity.

In one example, the current sharing regulation and the current regulation comprise current-based PI control, and the voltage regulation comprises voltage-based PI control.

In one example, the current-share voltage-sharing controller is further configured to:

subtracting the respective voltage values from the respective target reference values of the flying capacitors of the p-1 Buck cells to determine p-1 second voltage deviation values, and performing voltage regulation based on the p-1 second voltage deviation values to obtain an error signal vector u ═ u₁,u₁,…,u_p-1]^T；

For the error signal vector u ═ u₁,u₁,…,u_p-1]^TPerforming a decoupling operation to obtain a voltage sharing control adjustment amount delta d for the 1 st to P-1 st flying capacitors_iI-1, 2, …, p-1; and

calculating the voltage-sharing control adjustment quantity of the pth flying capacitor

In one example of the above-described method,

in one example, the voltage regulation includes voltage-based PI control, and the voltage-sharing control regulation amount and the current-sharing control amount include duty cycle signals for switching tubes of the p Buck units.

In one example, the current share controller is further configured to add the p share control adjustment amounts to the current share control amount to obtain an integrated control amount for the p Buck units.

In one example, the plurality of dc conversion modules communicate over an EtherCAT communication bus.

In one example, the plurality of dc conversion modules are each connected to the high voltage dc input and the low voltage dc bus by respective input and output switches, respectively, and each dc conversion module is de-energized in the event of a failure of itself.

In one example, each dc conversion module employs a multi-level Buck series topology with input and output common ground.

In one example, the device further comprises a filter for filtering out higher harmonics of the output voltages of the p Buck units; and a protection circuit for overvoltage protection.

According to another aspect of the present invention, there is provided a control method of a dc step-down converter for remotely controlling an ROV of an underwater robot, the dc step-down converter including a plurality of dc conversion modules connected in parallel, the plurality of dc conversion modules being communicatively connected to each other, each dc conversion module being configured to averagely carry a load current to power the ROV, the dc conversion module including a predetermined number p of Buck units connected in series and a current-sharing voltage-sharing controller, the control method including:

determining current-sharing control quantity based on the output current values of all the direct current conversion modules and the voltage output value of the current direct current conversion module;

determining p voltage-sharing control adjustment quantities based on voltage values of flying capacitors of p-1 Buck units from a low-voltage end to a high-voltage end of a current direct-current conversion module and corresponding target reference values; and

and performing current-sharing control and voltage-sharing control on the current direct current conversion module based on the current-sharing control quantity and the p voltage-sharing control regulating quantities.

In one example, the determining the current share control amount includes:

subtracting the current output current value of the direct current conversion module from the average value of the output current values of all the direct current conversion modules to determine a first current error value, and performing current sharing regulation on the basis of the first current error value to output a voltage regulation quantity;

subtracting the current output voltage value of the direct current conversion module from the output voltage reference value and adding the voltage adjustment amount to determine a first voltage error value, and performing voltage adjustment based on the first voltage error value to output a direct current reference value; and

and subtracting the current output current value of the direct current conversion module from the direct current reference value to determine a second current error value, and executing current regulation based on the second current error value to obtain the current-sharing control quantity.

In one example, the current sharing regulation and the current regulation comprise current-based PI control, and the voltage regulation comprises voltage-based PI control.

In one example, the determining p pressure equalization control adjustments includes:

subtracting the respective voltage values from the respective target reference values of the flying capacitors of the p-1 Buck cells to determine p-1 second voltage deviation values, and performing voltage regulation based on the p-1 second voltage deviation values to obtain an error signal vector u ═ u₁,u₁,…,u_p-1]^T；

For the error signal vector u ═ u₁,u₁,…,u_p-1]^TPerforming a decoupling operation to obtain a voltage sharing control adjustment amount delta d for the 1 st to P-1 st flying capacitors_iI-1, 2, …, p-1; and

calculating the voltage-sharing control adjustment quantity of the pth flying capacitor

In one example of the above-described method,

in one example, the voltage regulation includes voltage-based PI control, and the voltage-sharing control amount and the current-sharing control amount include duty cycle signals for switching tubes of the p Buck units.

In an example, the performing flow control and voltage sharing control on the current dc conversion module based on the current sharing control amount and the p voltage sharing control adjustment amounts includes performing current sharing voltage sharing adjustment on the p Buck units by adding the p voltage sharing control adjustment amounts to the current sharing control amount to obtain a comprehensive control amount for the p Buck units.

According to another aspect of the present invention, there is provided a control apparatus for a dc step-down converter apparatus for remotely controlling an ROV of an underwater robot, comprising a memory; and a processor coupled to the memory, the processor being configured to perform the control method.

According to yet another aspect of the present invention, there is provided a computer readable medium having stored thereon computer readable instructions which, when executed by a processor, implement the control method described above.

Drawings

The above features and advantages of the present disclosure will be better understood upon reading the detailed description of embodiments of the disclosure in conjunction with the following drawings. In the drawings, components are not necessarily drawn to scale, and components having similar relative characteristics or features may have the same or similar reference numerals.

Fig. 1 shows a schematic diagram of a power supply system for an ROV in an operating environment;

FIG. 2 illustrates a schematic diagram of an ROV efficient power and drive system in accordance with an aspect of the present invention;

fig. 3 shows a schematic diagram of an ROV high voltage dc supply according to an aspect of the present invention;

FIG. 4 illustrates a control block diagram of the compensation of the end of umbilical voltage in accordance with an aspect of the present invention;

FIG. 5 illustrates a block topology diagram of a DC buck converter apparatus in accordance with an aspect of the present invention;

FIG. 6 illustrates a topological block diagram of a DC conversion module in accordance with an aspect of the present invention;

fig. 7 illustrates a control block diagram of a multilevel dc converter in accordance with an aspect of the present invention;

FIG. 8 illustrates a schematic structural view of a propeller according to an aspect of the present invention; and

fig. 9 illustrates a cross-sectional view of a permanent magnet synchronous motor and a magnetic gear according to an aspect of the present invention.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. It is noted that the aspects described below in connection with the figures and the specific embodiments are only exemplary and should not be construed as imposing any limitation on the scope of the present invention.

Fig. 1 shows a schematic diagram of a power supply system of an ROV in an operating environment. The power supply required by the ROV (especially the working-grade ROV) is basically transmitted by a ship-side power supply device through a long-distance umbilical cable, and in order to meet the requirement of deep sea operation, the umbilical cable used for supplying power and communicating for the ROV underwater usually can be more than 3000 meters, even more than 10000 meters at the deepest.

Fig. 2 illustrates a schematic diagram of an ROV efficient power and drive system in accordance with an aspect of the present invention. As shown in fig. 2, the ROV power and drive system of the present invention may comprise both above-water and below-water sections. The above-water part may include the high voltage dc power supply device 100, and the below-water part may mainly include the dc step-down converter 210, the energy storage unit 220, the low voltage dc microgrid and power distribution unit 230, and at least one propeller 240. The subsea portion may also include a controller 250 and a sensor 260. The dc step-down converter 210, the energy storage unit 220, the low voltage dc microgrid and power distribution unit 230, the thruster 240, the work tool 250, the controller 260 and the sensor 270 of the subsea section are typically part of an ROV.

In practice, a three-phase low-voltage ac power source of the ship is input to the high-voltage dc power supply 100, converted into a high-voltage dc voltage, and transmitted to the terminal box of the ROV through the winch photoelectric slip ring and the long-distance umbilical cable. The dc down-converter 210 on the ROV may convert the high voltage dc to a low voltage dc for powering devices (such as the ROV's propeller 240, work tool 250, controller 260, and sensors 270) that are connected to the ROV low voltage dc bus, while the energy storage unit 220 may be connected to the ROV low voltage dc bus for emergency use in the event of a cable power outage or to replace the cable power altogether. The ROV low-voltage direct-current bus supplies power to the distributed integrated propeller, the operation tool, the controller and the like at the same time.

The HVDC power supply apparatus 100 may include a power distribution unit 110,

Fig. 3 shows a schematic diagram of an ROV high voltage dc supply 100 according to an aspect of the present invention. As shown, the hvdc power supply apparatus 100 may include a power distribution unit 110, a step-up transformer 120, a rectifier 130, and a dc filtering and discharging unit 140.

The power distribution unit 110 may include an input switch 111 and a charging unit 112. The input switch 111 can be used for connecting a ship input power supply and disconnecting the input when the ROV water surface power supply and the rear end load are overloaded or short-circuited, so that serious damage to a ship power supply system is avoided. The charging unit 112 may include a charging switch KM2, a charging resistor R1, a bypass switch KM1, and the like. Before the ROV water surface power supply is powered on, the bypass switch KM1 is disconnected, the current is limited within a controllable range through the charging resistor R1 when the charging switch KM2 is switched on, and after the work is finished, the charging switch KM2 is disconnected and the bypass switch KM1 is closed, so that the system enters a normal working state.

Under normal operation, the step-up transformer 120 may perform step-up conversion on the ship voltage, and its output is rectified by the rectifier 130, and then dc-filtered by the rear-end filtering and discharging unit 140 and discharged to output a high-voltage dc voltage.

According to an aspect of the present invention, the rectifier 130 may be a multi-pulse rectifier having a plurality of rectifier modules connected in series, and the step-up transformer 120 may be a phase-shifting transformer having a plurality of secondary windings with a predetermined phase difference therebetween and corresponding to the number of rectifier modules.

In the embodiment shown in fig. 3, the primary side of the step-up transformer 120 may be connected in a delta configuration, and the secondary side may have three secondary windings connected at an angle, which are staggered by 20 ° in phase, for boosting the ship input power into 3 independent power supplies for providing input power to the 18-pulse rectifier. To meet the voltage levels of different power sources, the primary side of step-up transformer 120 may have multiple tap options of different transformation ratios.

The ROV water surface power supply power system based on the multi-pulse rectifier is high in input power factor, small in input current harmonic, friendly to a ship power supply grid, small in output direct current ripple and friendly to long-distance cables and underwater remote-controlled robots.

Correspondingly, the rectifier 130 may include a rectifier module UR1, a rectifier module UR2, and a rectifier module UR 3. The rectifier modules are respectively composed of a three-phase controllable rectifier, and the direct current outputs of the three rectifier modules are connected in series and used for converting the output alternating current of the transformer into high-voltage direct current voltage.

The direct current filtering unit can be formed by connecting three capacitors C1, C2 and C3 in series, and is used for absorbing ripples of the output voltage of the rectifier 130 and ensuring the safe operation of the rear-end long cable.

According to an aspect of the present invention, the high voltage dc power supply device 100 may further include a voltage compensation module 150 for determining a voltage drop on the cable based on the output current of the dc filtering and discharging unit 140 and performing a voltage drop compensation control on the rectifier 130 based on the voltage drop and a target set value of the ROV terminal to output a stable high voltage dc voltage.

The working power supply of the deep-sea working robot is transmitted by a water surface high-voltage direct-current power supply through a long-distance umbilical cable, and because the impedance of the cable, the skin effect and the proximity effect influence, the input voltage of the ROV end is greatly influenced by the length of the cable and the working condition, and the adverse effect is brought to underwater electrical equipment. Therefore, a long-distance umbilical cable mathematical model considering skin and proximity effects is established in the scheme, signals are acquired without the voltage of an ROV (remote operated vehicle) terminal, the voltage drop of the umbilical cable is estimated directly according to information such as output voltage and current of a water surface direct current power supply system, and automatic compensation is carried out to ensure the stability of the voltage of an underwater module.

FIG. 4 illustrates a control block diagram for umbilical termination voltage compensation, which may be implemented by the voltage compensation module 150, in accordance with an aspect of the present invention.

As shown in fig. 4, the voltage drop on the cable may be first calculated, and then the voltage set value at the rectifier terminal may be determined based on the target set value at the ROV terminal and the voltage drop, and the rectifier may be subjected to rectification control based on a deviation between the set value and the sampled output voltage to output a stable high voltage dc voltage.

In one embodiment, the replenishment process may include the steps of:

step S1: firstly, the output DC voltage value U of the rectifier can be collected_{rec_fdb}And a value of direct current I_{rec_fdb}。

Step S2: direct current value I based on collection_{rec_fdb}And calculating the cable voltage drop according to the cable characteristic parameters.

In one example, the calculated pressure drop Δ U — K_T·K_S·K_PL.I/(r.S), where Δ U is the umbilical drop, K_TIs the temperature coefficient of resistance of the cable, K_SIs the cable resistance skin effect coefficient, K_PIs the cable resistance proximity effect coefficient, L is the cable length, I is the output current, r is electricityThe conductivity of the cable material, S is the cable cross-sectional area.

Step S3: setting the voltage of ROV end to a value U_{rov_ref}Adding a cable voltage drop (delta U) to obtain a rectifier terminal voltage set value U_{rec_ref}。

Step S4: rectifier terminal voltage set value U_{rec_ref}And the sampled value U_{rec_fdb}The deviation is controlled and output by a rectifier regulator and is used for driving the rectifier, so that the stability of the ROV end voltage under various working conditions is ensured.

The rectifier regulator is based on U_{rec_ref}And U_{rec_fdb}The deviation between the two performs PI control based on voltage to obtain a PI control amount for driving the rectifier, i.e., a rectification control signal. The commutation control signal may be a firing angle signal or a duty cycle signal based on the type of rectifier, e.g. for a thyristor type rectifier the commutation control signal is a firing angle signal and for an IGBT type rectifier the commutation control signal is a duty cycle signal.

The water surface high-voltage direct-current power supply system with the underwater terminal voltage automatic compensation is adopted, so that the electric energy loss of deep sea remote transmission is greatly reduced, and the diameter of an expensive umbilical cable wire is reduced. Underwater tail end voltage drop automatic compensation control method based on long-distance umbilical cable mathematical model automatically compensates power supply voltage drop loss of different cable lengths and different load working conditions during long-distance ROV power supply, and ensures stability of ROV power supply voltage

The power required by the ROV is basically and completely transmitted by a water surface high-voltage direct-current power supply through a long-distance umbilical cable, the ROV is compact in structure, and each internal electrical component is supplied with low-voltage direct current, so that a direct-current voltage reduction conversion device with high power density, high reliability and high device efficiency is urgently needed. The underwater direct current voltage reduction and conversion device is used for converting a high-voltage direct current voltage into a low-voltage direct current voltage and supplying power to all electrical components in the ROV.

According to one aspect of the invention, the direct current buck conversion device adopts a multi-module parallel topology and redundancy control, and meets the requirements of large power supply power and high reliability. The module adopts a multi-level Buck topology without an isolation transformer, the cost is low, the power density is high, the efficiency is high, and meanwhile, the structure of input and output common ground simplifies the insulation monitoring and grounding protection of underwater power supply.

Fig. 5 illustrates a block topology diagram of a dc down-conversion device 210 in accordance with an aspect of the present invention.

Based on the requirements of the working-level underwater robot on large power supply and high reliability, the dc step-down converter 210 may adopt a redundant structure in which a plurality of (4 in the figure as an example) dc conversion modules 211 work in parallel. All the dc conversion modules 211 can be connected to the high voltage dc cable from the water surface through switches, and each module independently converts the high voltage into a low voltage dc voltage and is connected to the dc bus through switches to provide power for each electrical component in the ROV.

Each dc conversion module 211 can be combined to provide total power conversion or can be operated individually to provide individual power conversion. In normal operation, the plurality of dc converter modules 211 supplies power to the load in parallel, each of which is loaded with the load current on average. When one or k of the dc conversion modules 211 fails, the power supply is automatically cut off by turning off the corresponding input and output switches, and the remaining dc conversion modules 211 continue to supply current to the load, so that the ROV operates normally or de-rated according to the number of the redundant modules. In the most extreme case, when all other dc conversion modules 211 fail, the ROV can still recover the power supply through the normal 1 module.

As shown in fig. 5 and 6, the plurality of dc conversion modules 211 of the dc step-down converter 210 are communicatively connected to each other. In one example, the dc conversion modules 211 may communicate with each other via an EtherCAT communication bus.

All power modules in the parallel system respectively bear the magnitude of load current through EtherCAT communication bus transmission, when a certain module breaks down, the module can automatically exit, the current of the module is not sent to the EtherCAT communication bus, and the problem that the whole system cannot work due to the fact that the certain module breaks down and does not output current is solved. The method for controlling the current sharing based on the EtherCAT communication bus not only has the advantage of high current sharing precision, but also is suitable for a redundancy working mode.

In addition, the control method of the multi-level-to-level current buck converter based on the EtherCAT communication bus guarantees voltage-sharing performance of multiple devices in series in a module and current-sharing performance of multiple modules in parallel, and is suitable for a redundancy working mode.

Fig. 6 shows a topological block diagram of a dc conversion module according to an aspect of the invention, and fig. 7 shows a control block diagram of a multilevel dc converter according to an aspect of the invention. The control of the dc converter 210 is described below in conjunction with fig. 6 and 7.

Each module of the dc voltage-reducing converter 210 may adopt a multi-level Buck series topology with input and output being common to ground, so as to reduce device stress, reduce filter device capacity, and greatly improve power density and module efficiency, and meanwhile, this configuration may meet the requirements of the ROV electrical system for underwater insulation monitoring and ground protection for input and output being common to ground.

As shown in fig. 6, the dc conversion module 211 may mainly include p Buck basic units, filters, protection units (such as Crowbar and Zener protection), input and output measurement units, and a controller connected in series.

Buck unit is the basic unit of converter and is composed of flying capacitor C_kAnd a switching tube Q_kAnd a diode D_kAnd the like. Switch tube Q_kAnd a diode D_kAnd conducting in a staggered and complementary way. The conducting phases of the p switching tubes have a difference of 2 pi/p in sequence, and when the duty ratios d of all the switching tubes are the same, the flying capacitor C_k(k 1,2.., p-1) the voltage above is kV_inAnd/p. When the switch tube Q_kOr a diode D_kWhen the flying capacitor is turned off, the voltage stress is the voltage V of the adjacent flying capacitor_CkThe difference of (a) to (b), namely: v_Dk＝V_Qk＝V_Ck-V_Ck-1＝V_in/p。

The filter can be composed of a filter inductor and a capacitor and is used for filtering higher harmonics of the output voltage of the multi-level Buck circuit.

The protection circuit may include a zener diode, a resistor, a thyristor, etc. When the output voltage of the DC conversion module exceeds a limit value, the voltage stabilizing diode is conducted, and when the output voltage further rises to exceed the voltage stabilizing value of the voltage stabilizing diode and the starting voltage of the thyristor, the thyristor is started to pull down the output voltage so as to protect the rear end component from overvoltage damage.

The controller and the input and output measuring part are used for controlling and protecting the DC conversion module according to input and output voltages, currents and the like.

In an actual circuit, as the switching characteristics and duty ratios of the switching tubes cannot be completely consistent, the flying capacitor voltage often deviates from a flat value, so that the converter cannot work normally. Meanwhile, a plurality of direct current buck conversion modules work in parallel, and the current of each module is unbalanced in practice. To this end, according to an aspect of the present invention, a multi-level dc buck converter control scheme with both voltage sharing and circulating current control is provided.

According to an aspect of the invention, each dc conversion module 211 may include a current-sharing voltage controller, such as the controller shown in fig. 6. The current-equalizing and voltage-equalizing controller can determine current-equalizing control quantity d based on output current values of all direct current conversion modules 211 and voltage output values of direct current conversion modules to which the current direct current conversion modules belong, and determine p voltage-equalizing control regulating quantities delta d based on voltage values of flying capacitors of 1 st to p-1 st Buck units from a low-voltage end to a high-voltage end of the current direct current conversion modules and corresponding target reference values_i(i ═ 1,2, …, p), and an adjustment amount Δ d based on the current sharing control amount d and the p voltage sharing control amounts_iAnd performing current sharing control and voltage sharing control on the current direct current conversion module.

According to the current sharing control of the invention, in one example, each parallel direct current conversion module has a unique ID number, all normally working modules send output current information to the communication bus at regular time, and each module calculates the output current average value I of all normally working modules at regular time according to the output current information received from the EtherCAT communication bus_avg. The average current value and the output current I of the module_OObtaining a current-sharing error signal by differentiating, and obtaining a voltage regulating signal V by the error signal through a current-sharing regulator_⊿. The regulating value V_⊿Correcting the error value of the output voltage to finally realizeThe output currents of the direct current conversion modules are balanced.

In one example, the process of calculating the current share control amount d may include the following steps:

step S1: the controller collects and outputs the DC voltage value V in real time_OAnd output a DC current value I_O。

Step S2: each direct current conversion module sends output current value of the direct current conversion module to the EtherCAT communication bus, and meanwhile, each direct current conversion module receives the output current values of other modules from the EtherCAT communication bus and adds the output current values to obtain the total current value I of the direct current conversion system_sumThen obtaining the average current value I output by each module according to the number of the normal working modules_avg。

Step S3: average current value I of DC conversion module_avgAnd the output current I of the module_OSubtracting to obtain a current-sharing error signal, and obtaining a voltage regulating signal V through a current-sharing regulator_⊿. In one example, the voltage regulation is a current-based PI controller, and the principles of the PI controller or PI regulator are well known to those skilled in the art and will not be described herein.

Step S4: will output a DC voltage reference value V_{O_ref}And a feedback value V_OSubtracting to obtain a voltage error signal, and adding a voltage regulation signal V output by the average current regulator_⊿Outputting a DC reference value I via a voltage regulator_{O_ref}. In one example, the voltage regulator herein is a voltage-based PI controller.

Step S5: will output a DC reference value I_{O_ref}And a feedback value I_OAnd subtracting to obtain a current error signal, obtaining a current-sharing control output signal d through a current regulator, and finally outputting the current-sharing control output signal d to the direct-current buck converter after being superposed with the voltage-sharing control signals of the switch tubes.

The voltage grading control according to the invention is in one example a voltage grading control based on capacitive voltage decoupling. The collected value V of the flying capacitor voltage shown in FIG. 7_CiWith reference value i.V_inComparing p (i is 1,2, …, p-1) and obtaining error information through a capacitance voltage regulatorNumber u_i(i-1, 2, …, p-1). Vector u ═ u₁,u₁,…,u_p-1]^TCo-decoupling matrix A₁ ^-1After multiplication, the delta d can be obtained_i(i-1, 2, …, p-1), and is prepared fromCalculating (delta d)_p. Will (delta d)_i(i is 1,2, …, p) and d are added to obtain the comprehensive control signal d of each switching tube_k(k ═ 1,2, …, p), where the integrated control quantity may be a duty cycle signal for output to the dc conversion module to control the multi-level dc conversion module to operate normally.

In an example, a voltage-sharing control adjustment amount (delta d) is calculated_iMay comprise the following steps:

step S1: the controller collects the input DC voltage value V in real time_inVoltage value V of each flying capacitor_Ci(i＝1,2,…,p-1)。

Step S2: collecting value V of flying capacitor voltage_CiWith reference value i.V_inComparing p (i is 1,2, …, p-1) and obtaining error signal u through capacitance voltage regulator_i(i-1, 2, …, p-1). The voltage regulator can be a voltage-based PI controller, and regulates the voltage deviation between the voltage acquisition value of the flying capacitor and the reference value into an error signal u_iHere the error signal u_iMay be a duty cycle signal.

Step S3: dividing the error signal vector u into [ u ]₁,u₁,…,u_p-1]^TCo-decoupling matrix A₁ ^-1Multiplying to obtain the 1 st to p-1 st fly capacitor voltage-sharing control fine adjustment value delta d_i(i ═ 1,2, …, p-1), calculated in one example as follows:

step S4: from (Δ d)_i(i-1, 2, …, p-1) is represented by the formulaCalculating a fine adjustment value delta d of the p-th switching tube_p。

Step S5: respectively enabling the output value d of the current-sharing controller to be in line with the fine adjustment value delta d of the p switching tubes_i(i is 1,2, …, p) to obtain the duty ratio d of each switching tube_kAnd (k is 1,2, …, p), and outputting the k to the DC conversion module to control the multi-level DC conversion module to normally work.

As shown in fig. 2, according to an aspect of the present invention, a backup energy storage unit 220 is further provided for providing backup energy in case of a cable failure.

The working-grade ROV has large power consumption, and basically all required power is transmitted by a ship-side power supply device through a long-distance umbilical cable. Due to the complex deep sea working environment, the ROV will cause the interruption of the power supply due to the breakage of the umbilical cable, the failure of all branches of the DC buck converter and other reasons, and will bring great risk to the ROV equipment. According to the invention, the energy storage module and the direct current voltage reduction conversion module are connected in parallel to supply power in a mixed manner to form the ROV underwater direct current micro-grid, so that the requirements of distributed electric equipment are met, the energy conversion link is simplified, the energy conversion efficiency is improved, and the reliability of ROV power supply is further ensured.

When the cable is in normal operation, the high-voltage direct-current voltage on the water surface is reduced by the direct-current converter and then supplies power to all electrical loads of the ROV, meanwhile, the DC-DC converter connected to the low-voltage direct-current bus charges the battery of the energy storage unit 220, and the energy stored in the battery is used for providing emergency power supply for the ROV when the power supply of the cable is interrupted. When the power supply of the cable is interrupted, the energy storage unit 220 can provide an emergency standby power supply for the low-voltage direct-current bus through the DC-DC converter, so that the subsea robot can float to the water surface through buoyancy regulation in an emergency and at least one propeller can be ensured to work.

In one example, after the deep sea robot is upgraded to an AUV, the heavy umbilical cable can be eliminated, but its long-term energy reserve is a critical issue. At the moment, the position where the direct current voltage reduction conversion device is originally installed can be replaced by a high-capacity energy storage module, so that a power supply is provided for long-time underwater work of the AUV.

In the present case, parallelly connected hybrid power supply with energy storage module and direct current step-down transform module constitutes ROV direct current microgrid under water, satisfies distributed consumer demand, has both simplified the energy transform link and has improved energy conversion efficiency, has further guaranteed the reliability of ROV power supply again. Meanwhile, the modular structure can directly replace the direct current buck converter with a high-capacity energy storage module, so that a power supply is provided for long-time underwater work upgraded to AUV in the future.

Returning to fig. 2, the low-voltage dc voltage provided by the dc down-converter 210 is provided to various electrical components of the ROV, such as the thruster 240, the work tool 250, the controller 260, and the sensor 270, through the low-voltage dc distribution unit 230. The low-voltage dc power distribution unit 230 may include components such as switches and protection, and provide access and protection functions for devices accessing the ROV low-voltage dc microgrid.

Fig. 8 shows a schematic structural view of a propeller 800 according to an aspect of the present invention. According to an aspect of the invention, the underwater propulsion of the ROV may employ a distributed variable frequency drive scheme. As shown in fig. 8, each propeller 800 integrates a driver 810, a permanent magnet synchronous motor 820 driven by a magnetic gear 830, a propeller 840, and the like.

All components are integrated in an integrated aluminum alloy shell, and the control, the power electronic device, the motor, the propeller and the like are organically combined, so that the integration, the miniaturization and the modularization of the appearance are realized, and the electromechanical energy conversion and transmission are more effectively realized.

Fig. 9 illustrates a cross-sectional view of a permanent magnet synchronous motor and a magnetic gear according to an aspect of the present invention.

As shown in fig. 9, the permanent magnet synchronous motor with a magnetic gear combines a permanent magnet synchronous motor 820 and a magnetic gear 830. The permanent magnet synchronous motor 820 may include a motor stator 821, a permanent magnet rotor 822, and the like. The magnetic gear 830 may include a high speed rotor 831, a pole piece stator 832, an outer magnet rotor 833, etc., and the magnetic gear high speed rotor 831 may be magnetically coupled to the outer magnet rotor 833 through the pole piece stator 832. The inner drive shaft 823 may connect the rotor 822 of the permanent magnet synchronous motor 820 with the high speed rotor 831 of the magnetic gear 830, and the magnetic gear outer magnets transmit power to the propeller 840, which is coaxial with the magnetic gear outer magnet rotor 833, through the outer drive shaft 834. The magnetic gear 830 uses permanent magnets to transmit torque between the input shaft and the output shaft, and can transmit force into a hermetically sealed housing without using a leak-prone radial shaft seal, and is therefore more suitable for deep sea robot applications requiring high sealing.

In one example, the thruster 800 may employ a power module based on SiC devices to convert the ROV underwater low voltage dc to a three-phase ac voltage with adjustable frequency and amplitude according to the control command of the ROV control system, so as to supply power to the stator windings of the permanent magnet synchronous motor 820. The stator 821 of the permanent magnet synchronous motor 820 is fed with three-phase alternating current, a rotating magnetic field is formed in the stator winding, the rotating magnetic field interacts with the permanent magnet rotor 822, electromagnetic torque output in the same rotating direction as the rotating magnetic field of the stator is generated, and therefore electric energy is converted into output mechanical energy.

An inner drive shaft 823 of the magnetic gear 830 mechanism may connect the rotor 822 of the permanent magnet synchronous motor 820 with a high speed rotor 831 of the magnetic gear 830, the magnetic gear outer magnets transmitting power to the propeller 840 through an outer drive shaft 834. The magnetic gear 830 transmits torque between the input shaft and the output shaft through a non-direct contact manner, the propeller 840 is directly contacted with seawater, a large amount of seawater is continuously pushed backwards by the blades in the rotation process, and forward propelling force is generated on the blades, so that the ROV is propelled to move.

The propeller 800 in the scheme replaces a mechanical gear with a magnetic coupling gear to drive a propeller, and has the advantages of high transmission efficiency, good underwater sealing performance, small mechanical abrasion and low operation noise.

According to one aspect of the invention, an underwater robot propeller allocation algorithm based on model identification and inequality constraint linear optimization on line is provided for solving the problem that thrust allocation is difficult due to the fact that an underwater robot is difficult to model, the number of propellers, the installation positions are different and the like. According to the algorithm, the underwater robot thrust distribution is completed in a self-adaptive manner through online parameter identification according to the external force and torque control requirements without knowing the underwater robot mathematical model, the number of the propellers, the mounting positions and the mounting angles of the propellers in advance.

First, online identification may be performed on the mathematical model parameters of the ROV. Because the underwater robot moves in six degrees of freedom, the underwater robot mathematical model is expressed by adopting the following six-degree of freedom nonlinear mathematical simulation:

wherein, M represents an equivalent mass and inertia matrix, C (V) represents a Coriolis force and centripetal force coefficient matrix, D (V) represents a fluid damping coefficient matrix, V represents a robot speed state vector, and U represents an external force and moment input vector. More specifically, V ═ u, V, w, p, q, r]^TU, v, w respectively represent the velocity in the direction of the axis X, Y, Z of the underwater robot, p, q, r represent the pitch angle velocity, the heading angle, and the roll angle velocity of the underwater robot, and U ═ U [ [ U ] ]₁,u₂,u₃,u₄,u₅,u₆]^TWhere U is N.T, N is a transformation matrix, U₁,u₂,u₃Representing thrust, u, in the direction of the axis of the underwater robot X, Y, Z₄,u₅,u₆Representing the pitch angle moment, course angle moment and roll angle moment of the underwater robot, wherein T is [ T [ [ T ]₁,t₂,…,t_m]^TRepresenting the propeller command vector, m representing the number of propellers.

By carrying out first-order linearization on the model, the following linearization model can be obtained, and the motion process of the underwater robot is approximately described:

V(n+1)＝A·V(n)+B·T(n)

where n is the time factor index, let:

taking the speed of the underwater robot in the X-axis direction as an example, according to the above formula, the following expression formula can be obtained:

u(n+1)＝a_1,1u(n)+a_1,2v(n)+a_1,3w(n)+a_1,4p(n)+a_1,5q(n)+a_1,6r(n)+b_1,1t(1)+…+b_1,mt(m)

defining:

the real-time parameter identification can be carried out by a recursive least square parameter identification method with forgetting factors:

P(0)＝p₀I

representing the identification parameters obtained by the above algorithm.

Similarly, the identification parameter matrix of the B matrix can be obtained by sequentially performing the real-time parameter identification on the speed in the Y, Z axial direction, the pitch angle speed, the course angle and the roll angle speedTherefore, the relation between the thrust of each propeller and the external force and torque input of the underwater robot can be obtained as follows:

wherein the content of the first and second substances,the identification values of the external force and moment vectors of the propellers.

Then based onExpected value U of external force and moment vector of each propeller_demandAnd a propeller instruction vector T ═ T for each propeller₁,t₂,…,t_m]^TPerform optimization to solve for propeller instructions:

s.t.t_j,min≤t_j(n+1)≤t_j,max,j∈[1,2,…,m]

wherein, c₁And c₂In order to be a weight parameter, the weight parameter,is the average of the current propeller outputs, t_j,minMinimum thrust of the propeller, t_j,maxIs the maximum thrust value.

In the above optimization algorithm, toExpected value U of external force and moment vector of each propeller_demandThe error between the thrusters and the sum of the weights of the variances of the thrusters are the optimization target, and the aim of maximally and averagely utilizing the performances of all the thrusters is fulfilled while the thrust distribution result of the underwater robot is as close to the expected value as possible by solving the minimized value of the error. And (4) solving the optimization problem to complete the distribution of the ROV adaptive moment. The assignment algorithm herein may be implemented by, for example, the controller 260.

In the invention, the force and the moment of the propeller acting on the underwater robot are used as optimization objects, the moment distribution problem is converted into a linear optimization problem, and the difficulty of an optimization algorithm is reduced. The method has the advantages that the variance of all moments is used as an optimization object, the problems that the output value of one propeller is too large and the output values of other propellers with similar functions are too small in the redundancy control process can be solved, and the capabilities of all the propellers are utilized averagely to the maximum extent.

Those of skill in the art would understand that information, signals, and data may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits (bits), symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The various illustrative logical modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

In one or more exemplary embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software as a computer program product, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a web site, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk (disk) and disc (disc), as used herein, includes Compact Disc (CD), laser disc, optical disc, Digital Versatile Disc (DVD), floppy disk and blu-ray disc where disks (disks) usually reproduce data magnetically, while discs (discs) reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.