阅读说明：本技术 永磁同步电机位置传感器的零位自学习方法、系统 (Zero self-learning method and system for permanent magnet synchronous motor position sensor ) 是由 蒋元广 刘兵 李占江 高超 李麟 于 2019-10-21 设计创作，主要内容包括：本发明提出了一种永磁同步电机位置传感器的零位自学习方法、系统,其中,方法包括：获取永磁同步电机三相电流中的最大值,并根据最大值和电流参考值计算得到电压幅值；分配电压幅值,以获取当前周期内各阶段所需的两相静止坐标系下的α、β轴电压(u<Sub>α</Sub>,u<Sub>β</Sub>)；根据各阶段所需的(u<Sub>α</Sub>,u<Sub>β</Sub>),采用SVPWM控制永磁同步电机,并读取永磁同步电机的位置传感器在各阶段输出的位置信号；根据位置传感器在各阶段输出的位置信号计算零位补偿角。该零位自学习方法,实现了电机电流可闭环控制且电流幅值可调整的零位自学习过程,无需手动调整电压幅值,降低了操作复杂性,同时可避免电机因过流而降低寿命的问题和电机因电流过小而无法转动的问题。(The invention provides a zero self-learning method and a zero self-learning system for a permanent magnet synchronous motor position sensor, wherein the method comprises the following steps: acquiring the maximum value of three-phase current of the permanent magnet synchronous motor, and calculating according to the maximum value and a current reference value to obtain a voltage amplitude; distributing the voltage amplitude to obtain the alpha and beta axis voltages (u) in the two-phase static coordinate system required by each stage in the current period α ，u β ) (ii) a According to the (u) required for each stage α ，u β ) Adopting SVPWM to control the permanent magnet synchronous motor and reading position signals output by a position sensor of the permanent magnet synchronous motor at each stage; and calculating a zero compensation angle according to the position signals output by the position sensor at each stage. The zero-position self-learning method realizes the zero-position self-learning process with closed-loop control of the motor current and adjustable current amplitude, does not need to manually adjust the voltage amplitude, reduces the operation complexity, and simultaneously can avoid the motor from overcurrentthereby reducing the service life and preventing the motor from rotating due to too small current.)

1. A zero self-learning method of a permanent magnet synchronous motor position sensor is characterized by comprising the following steps:

Acquiring a maximum value in three-phase current of the permanent magnet synchronous motor, and calculating according to the maximum value and a current reference value to obtain a voltage amplitude;

Distributing the voltage amplitude values to obtain alpha and beta axis voltages (u) under a two-phase static coordinate system required by each stage in the current period_α，u_β) (u) required for the stages_α，u_β) Is sequentially (0, u)_m）、（u_m，0）、（0，-u_m）、（u_m0), wherein u_mIs the voltage amplitude;

According to the (u) required for each stage_α，u_β) Adopting SVPWM to control the permanent magnet synchronous motor and reading position signals output by a position sensor of the permanent magnet synchronous motor at each stage;

Calculating a zero compensation angle from position signals output by the position sensor at each stage, the (0, u)_m）、（u_m，0）、（0，-u_m）、（u_m0) the corresponding position signals are each θ₁、θ₂、θ₃And theta₄Wherein the null compensation angle theta is calculated by the following formula_c：

θ_c=(θ₂+θ₄)/2。

2. The method of claim 1, wherein calculating a voltage amplitude from the maximum value and a current reference value comprises:

The current reference value and the maximum value are subjected to difference to obtain a current difference value;

And performing PI regulation on the current difference value to obtain the voltage amplitude.

3. The method of claim 1, wherein the initial value of the maximum value is 0, I_ref=20%I_NWherein, I_refIs the current reference value, I_NThe rated current of the permanent magnet synchronous motor.

4. A computer-readable storage medium, on which a computer program is stored, which program, when being executed by a processor, carries out a method for zero self-learning of a permanent magnet synchronous motor position sensor according to any one of claims 1-3.

5. Computer arrangement comprising a memory, a processor and a computer program stored on the memory, characterized in that the processor, when executing the computer program, implements the zero self-learning method of a permanent magnet synchronous motor position sensor according to any of claims 1-3.

6. The zero self-learning system of the permanent magnet synchronous motor position sensor is characterized by comprising the following components:

The maximum value acquisition module is used for acquiring the maximum value of three-phase currents of the permanent magnet synchronous motor;

The voltage amplitude self-adjusting module is used for calculating to obtain a voltage amplitude according to the maximum value and the current reference value;

A distribution module for distributing the voltage amplitude to obtain the alpha and beta axis voltages (u) in the two-phase static coordinate system required by each stage in the current period_α，u_β) (u) required for the stages_α，u_β) Is sequentially (0, u)_m）、（u_m，0）、（0，-u_m）、（u_m0), wherein u_mIs the voltage amplitude;

A control module for controlling the phase according to the (u) required by each phase_α，u_β) Controlling the permanent magnet synchronous motor by adopting SVPWM;

a reading calculation module for reading the position signals output by the position sensor of the permanent magnet synchronous motor at each stage and calculating a zero compensation angle according to the position signals output by the position sensor at each stage, wherein (0, u)_m）、（u_m，0）、（0，-u_m）、（u_m0) the corresponding position signals are each θ₁、θ₂、θ₃And theta₄Wherein the calculation module calculates the zero compensation angle theta by the following formula_c：

θ_c=(θ₂+θ₄)/2。

Technical Field

The invention relates to the technical field of motor control, in particular to a zero self-learning method and a zero self-learning system for a permanent magnet synchronous motor position sensor.

Background

The permanent magnet synchronous motor is widely applied to the fields of industrial manufacturing, new energy automobiles and the like by virtue of the characteristics of high efficiency, excellent control performance and the like. Accurate position detection is a precondition for obtaining superior control performance of the permanent magnet synchronous motor, and is usually obtained by a mechanical position sensor. Due to the installation error, the position signal output by the mechanical position sensor has a deviation from the actual position, and needs to be compensated.

The approximate procedure for zero compensation angle acquisition is: and injecting voltage into the stator winding of the motor, forcibly dragging the rotor to a position overlapped with the axis of the A-phase winding, and reading a position signal output by the position sensor to serve as a zero compensation angle. The selection of the injection voltage amplitude has an important influence on the service life of the motor and the zero compensation angle precision, and if the injection voltage amplitude is too large, the winding current is too large, the service life of the motor can be reduced, and even the motor can be directly burnt; if the amplitude of the injection voltage is too small, the formed current is too small, and then enough torque cannot be generated to drag the motor rotor to rotate to a specified position, so that the accuracy of the zero compensation angle is influenced.

In order to solve the problems, the conventional method determines a proper voltage amplitude value through a plurality of previous attempts and adjustments, and then applies the voltage amplitude value to a motor winding, so that the problem that the service life of the motor is shortened due to overlarge current is solved, and the problem that the rotor cannot be dragged due to the overlarge current is also solved. However, this way of adjusting the voltage amplitude many times increases the operation complexity of the zero compensation angle acquisition process, and when the controlled object motor is replaced and the control parameters such as the control frequency and the dead time are adjusted, the voltage amplitude needs to be adjusted again, which is very troublesome.

Disclosure of Invention

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art.

Therefore, the first objective of the present invention is to provide a zero self-learning method for a permanent magnet synchronous motor position sensor, so as to implement zero self-learning of a permanent magnet synchronous motor, reduce the operation complexity of the zero self-learning process, and simultaneously avoid the problems of life reduction of the motor due to overcurrent and incapability of rotating the motor due to too small current.

A second object of the invention is to propose a computer-readable storage medium.

A third object of the invention is to propose a computer device.

The fourth purpose of the invention is to provide a zero self-learning system of the permanent magnet synchronous motor position sensor.

In order to achieve the above object, an embodiment of a first aspect of the present invention provides a zero self-learning method for a permanent magnet synchronous motor position sensor, which includes the following steps: acquiring a maximum value in three-phase current of the permanent magnet synchronous motor, and calculating according to the maximum value and a current reference value to obtain a voltage amplitude; distributing the voltage amplitude values to obtain alpha and beta axis voltages (u) under a two-phase static coordinate system required by each stage in the current period_α，u_β) (ii) a According to the (u) required for each stage_α，u_β) Adopting SVPWM to control the permanent magnet synchronous motor and reading position signals output by a position sensor of the permanent magnet synchronous motor at each stage; and calculating a zero compensation angle according to the position signals output by the position sensor at each stage.

According to the zero self-learning method of the permanent magnet synchronous motor position sensor, the voltage amplitude is obtained through obtaining the maximum current value and the reference current value, and the voltage amplitude is distributed to obtain the alpha-axis voltage and the beta-axis voltage (u) under the two-phase static coordinate required by each stage in the current period_α，u_β) According to the shaft voltage (u)_α，u_β) And controlling the permanent magnet synchronous motor by using SVPWM, reading position signals output by a position sensor of the permanent magnet synchronous motor at each stage, and finally calculating a zero compensation angle according to the position signals. The zero-position self-learning method realizes the zero-position self-learning process with closed-loop control of the motor current and adjustable current amplitude without manual operationThe voltage amplitude is adjusted, the operation complexity in the zero self-learning process is reduced, and meanwhile the problems that the service life of the motor is shortened due to overcurrent and the motor cannot rotate due to too small current can be avoided.

In addition, the zero self-learning method of the permanent magnet synchronous motor position sensor according to the above embodiment of the present invention may further have the following additional technical features:

According to one embodiment of the invention, the phases are required for (u)_α，u_β) Is sequentially (0, u)_m）、（u_m，0）、（0，-u_m）、（u_m0), wherein u_mis the voltage amplitude.

According to one embodiment of the present invention, (0, u)_m）、（u_m，0）、（0，-u_m）、（u_m0) the corresponding position signals are each θ₁、θ₂、θ₃And theta₄Wherein the null compensation angle theta is calculated by the following formula_c：θ_c=(θ₂+θ₄)/2。

According to an embodiment of the present invention, calculating the voltage amplitude according to the maximum value and the current reference value includes: the current reference value and the maximum value are subjected to difference to obtain a current difference value; and performing PI regulation on the current difference value to obtain the voltage amplitude.

According to one embodiment of the invention, the initial value of the maximum value is 0, I_ref=20%I_NWherein, I_refIs the current reference value, I_NThe rated current of the permanent magnet synchronous motor.

To achieve the above object, a second aspect of the present invention provides a computer-readable storage medium, on which a computer program is stored, and the computer program, when executed by a processor, implements the zero self-learning method for a permanent magnet synchronous motor position sensor according to the above embodiments.

The computer-readable storage medium of the embodiment of the invention can realize the zero self-learning method of the permanent magnet synchronous electrode position sensor of the embodiment by executing the computer program stored on the computer-readable storage medium, thereby realizing the zero self-learning process with closed-loop control of the motor current and adjustable current amplitude, avoiding the need of manually adjusting the voltage amplitude, reducing the operation complexity of the zero self-learning process, and simultaneously avoiding the problems of the motor reducing the service life due to overcurrent and the motor being incapable of rotating due to too small current.

In order to achieve the above object, a third aspect of the present invention provides a computer device, which includes a memory, a processor, and a computer program stored on the memory, wherein the processor, when executing the computer program, implements the zero self-learning method for the permanent magnet synchronous motor position sensor according to the above embodiment.

the computer device of the embodiment of the invention can realize the zero self-learning method of the permanent magnet synchronous motor position sensor of the embodiment by executing the computer program stored in the memory, thereby realizing the zero self-learning process with closed-loop control of the motor current and adjustable current amplitude, avoiding manual adjustment of the voltage amplitude, reducing the operation complexity of the zero self-learning process, and simultaneously avoiding the problems that the motor has reduced service life due to overcurrent and cannot rotate due to too small current.

In order to achieve the above object, a fourth aspect of the present invention provides a zero self-learning system for a permanent magnet synchronous motor position sensor, including: the maximum value acquisition module is used for acquiring the maximum value of three-phase currents of the permanent magnet synchronous motor; the voltage amplitude self-adjusting module is used for calculating to obtain a voltage amplitude according to the maximum value and the current reference value; a distribution module for distributing the voltage amplitude to obtain the alpha and beta axis voltages (u) in the two-phase static coordinate system required by each stage in the current period_α，u_β) (ii) a A control module for controlling the phase according to the (u) required by each phase_α，u_β) Controlling the permanent magnet synchronous motor by adopting SVPWM; a reading calculation module for reading the position signals output by the position sensor of the permanent magnet synchronous motor at each stage and sensing the position signals according to the positionThe position signals output by the device at each stage calculate the zero compensation angle.

The zero self-learning system of the permanent magnet synchronous motor position sensor of the embodiment of the invention obtains the maximum value in the three-phase current of the permanent magnet synchronous motor through the maximum value obtaining module, obtains the voltage amplitude value through the voltage amplitude value self-adjusting module according to the maximum value and the current reference value, and distributes the voltage amplitude value through the distributing module to obtain the alpha and beta axis voltages (u and u) under the two-phase static coordinate system required by each stage in the current period_α，u_β) Then according to the shaft voltage (u)_α，u_β) The control module is used for controlling the permanent magnet synchronous motor by adopting SVPWM, the reading and calculating module is used for reading position signals output by a position sensor of the permanent magnet synchronous motor at each stage, and the zero compensation angle is calculated according to the position signals output by the position sensor at each stage. Therefore, the zero self-learning process with the motor current capable of being controlled in a closed loop mode and the current amplitude adjustable is achieved, the voltage amplitude does not need to be adjusted manually, the operation complexity of the zero self-learning process is reduced, and meanwhile the problems that the service life of the motor is shortened due to overcurrent and the motor cannot rotate due to too small current can be solved.

In addition, the zero self-learning system of the permanent magnet synchronous motor position sensor according to the above embodiment of the present invention may further have the following additional technical features:

According to one embodiment of the invention, the phases are required for (u)_α，u_β) Is sequentially (0, u)_m）、（u_m，0）、（0，-u_m）、（u_m0), wherein u_mIs the voltage amplitude.

According to one embodiment of the present invention, (0, u)_m）、（u_m，0）、（0，-u_m）、（u_m0) the corresponding position signals are each θ₁、θ₂、θ₃And theta₄Wherein the calculation module calculates the zero compensation angle theta by the following formula_c：θ_c=(θ₂+θ₄)/2。

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The foregoing and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a schematic flow chart of a zero self-learning method for a permanent magnet synchronous motor position sensor according to an embodiment of the present invention;

FIG. 2 is a control block diagram of a zero self-learning method for a permanent magnet synchronous motor position sensor according to a specific example of the present invention;

Fig. 3 is a block diagram of a zero self-learning system of a permanent magnet synchronous motor position sensor according to an embodiment of the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

The zero self-learning method and system of the permanent magnet synchronous motor position sensor according to the embodiment of the invention are described below with reference to the accompanying drawings.

Fig. 1 is a schematic flow chart of a zero self-learning method of a permanent magnet synchronous motor position sensor according to an embodiment of the present invention.

As shown in fig. 1, the zero self-learning method includes the following steps:

and S1, acquiring the maximum value of the three-phase current of the permanent magnet synchronous motor, and calculating to obtain the voltage amplitude according to the maximum value and the current reference value.

As an example, the current reference value I may be calculated from the rated current of the permanent magnet synchronous machine_ref，I_refIs less than the rated current I of the permanent magnet synchronous motor_NE.g. current reference value I_refTaking rated current I_N20% of (I), i.e. I_ref=20%I_NMeanwhile, maximum value I of permanent magnet synchronous motor_maxIs taken to be 0. As shown in fig. 2, the current is referenced to a value I_refAnd maximum value I_maxThe voltage amplitude can be obtained by calculation after the difference is subjected to PI adjustment, so that the complex process that a worker manually adjusts the voltage amplitude according to the synchronous controlled object motor and the control parameter is omitted.

S2, distributing the voltage amplitude to obtain the alpha and beta axis voltages (u) under the two-phase static coordinate system required by each stage in the current period_α，u_β）。

In one example of the invention, the (u) required for each stage_α，u_β) Is sequentially (0, u)_m）、（u_m，0）、（0，-u_m）、（u_m0), wherein u_mIs the voltage amplitude.

Specifically, after the voltage amplitude is determined, the voltages required for the stages of the permanent magnet synchronous motor are respectively set to (0, u)_m）、（u_m，0）、（0，-u_m）、（u_m0), namely the voltage amplitude is distributed, so that the permanent magnet synchronous motor can conveniently and accurately make the permanent magnet synchronous motor required according to each stage (u)_α，u_β) The position signals output by the position sensor of the permanent magnet synchronous motor at each stage are obtained, and then the permanent magnet synchronous motor is driven according to the position signals output by each stage.

s3, according to the (u) required by each stage_α，u_β) The SVPWM is adopted to control the permanent magnet synchronous motor, and position signals output by a position sensor of the permanent magnet synchronous motor at each stage are read.

In particular, according to the (u) required for each stage_α，u_β) The SVPWM algorithm is adopted to generate a driving signal, so that the permanent magnet synchronous motor is driven according to the driving signal, in the process of driving the permanent magnet synchronous motor, the position signals output by the position sensor of the permanent magnet synchronous motor at each stage can be read, and the position signals at each stage of the permanent magnet synchronous motor can be used as the basis for calculating the zero compensation angle of the permanent magnet synchronous motor later.

And S4, calculating a zero compensation angle according to the position signals output by the position sensor at each stage.

as an example, (0, u)_m）、（u_m，0）、（0，-u_m）、（u_m0) the corresponding position signals are each θ₁、θ₂、θ₃And theta₄Wherein the null compensation angle theta is calculated by the following formula_c：θ_c=(θ₂+θ₄)/2。

Referring to fig. 2, the output voltage amplitude u is adjusted by the voltage amplitude self-adjusting module_msetting the alpha and beta axis voltages (u, u) required by the zero self-learning different stages through a multi-way selection switch S in the voltage distribution module_α，u_β) I.e., (0, u)_m）、（u_m，0）、（0，-u_m）、（u_m,0). Further mixing (0, u)_m）、（u_m，0）、（0，-u_m）、（u_m0) four groups of data are respectively connected to input ends of '1', '2', '3' and '4' of the multi-way switches S in the voltage distribution module, the multi-way selection switches S in the voltage distribution module are respectively arranged on the input ends of '1', '2', '3' and '4', and the position sensors respectively output position signals theta₁、θ₂、θ₃And theta₄Using the formula θ_c=(θ₂+θ₄) Calculating to obtain zero compensation angle theta_c. Of course, the zero compensation angle theta can be effectively increased by taking an average value through multiple measurements_cthe detection accuracy of (2).

Specifically, as shown in fig. 2, the three-phase current i of the permanent magnet synchronous motor is detected and obtained_A、i_BAnd i_Cand further obtaining the maximum value I in the three-phase current of the permanent magnet synchronous motor through comparison_maxperforming difference operation on the maximum value and the current reference value, performing PI regulation on the obtained difference value through a PI regulator, and outputting a voltage amplitude value, wherein a voltage distribution module distributes the voltage amplitude value to obtain alpha-axis voltage and beta-axis voltage (u) under a two-phase static coordinate system required by each stage in the current period_α，u_β). According to the (u) required for each stage_α，u_β) Generating six-path driving signal D of inverter by SVPWM algorithm, and using U as DC power supply_dcAnd the voltage supplies power to the inverter, and the inverter drives the permanent magnet synchronous motor according to the driving signal D. And reading the position signals output by the position sensor of the permanent magnet synchronous motor at each stage by using the reading and calculating module, and calculating the zero compensation angle according to the position signals output by the position sensor at each stage, so that the zero compensation is performed on the operation of the permanent magnet synchronous motor according to the zero compensation angle.

According to the zero-position self-learning method of the permanent magnet synchronous motor position sensor, provided by the embodiment of the invention, the voltage amplitude is not required to be adjusted manually by a worker, the workload of the worker can be reduced through calculation automatically, the operation complexity of the zero-position self-learning process is reduced, and the problems that the service life of the motor is reduced due to overcurrent and the motor cannot rotate due to too small current can be avoided.

Further, the present invention provides a computer-readable storage medium, on which a computer program is stored, which when executed by a processor, can implement the zero self-learning method of the permanent magnet synchronous motor position sensor in the above embodiments.

when the computer program corresponding to the zero self-learning method of the permanent magnet synchronous motor position sensor stored on the computer readable storage medium is executed, the voltage amplitude can be automatically acquired, the operation complexity of the zero self-learning process can be reduced, and the problems that the service life of the motor is shortened due to overcurrent and the motor cannot rotate due to too small current can be avoided.

further, the present invention provides a computer device, which includes a memory, a processor, and a computer program stored on the memory, and when the processor executes the computer program, the zero self-learning method of the permanent magnet synchronous motor position sensor in the above embodiments is implemented.

The computer equipment provided by the embodiment of the invention is provided with the memory, the computer program stored on the memory and the processor, and when the computer program stored on the memory and corresponding to the zero self-learning method of the permanent magnet synchronous motor position sensor is executed by the processor, the permanent magnet synchronous motor can automatically acquire the voltage amplitude, the operation complexity of the zero self-learning process is reduced, and meanwhile, the problems that the service life of the motor is reduced due to overcurrent and the motor cannot rotate due to too small current can be avoided.

Fig. 3 is a block diagram of a zero self-learning system of a permanent magnet synchronous motor position sensor according to an embodiment of the present invention.

As shown in fig. 3, the zero self-learning system 100 for a permanent magnet synchronous motor position sensor includes: a maximum acquisition module 110, a voltage amplitude self-adjustment module 120, a distribution module 130, a control module 140, and a read calculation module 150.

The maximum value obtaining module 110 is configured to obtain a maximum value in three-phase currents of the permanent magnet synchronous motor; the voltage amplitude self-adjusting module 120 is configured to calculate a voltage amplitude according to the maximum value and the current reference value; the distribution module 130 is configured to distribute the voltage amplitudes to obtain α and β axis voltages (u) in the two-phase stationary coordinate system required by each stage in the current period_α，u_β) (ii) a The control module 140 is used for controlling the operation according to the (u) required by each stage_α，u_β) Controlling a permanent magnet synchronous motor by adopting SVPWM (space vector pulse width modulation); the reading calculation module 150 is configured to read position signals output by the position sensor of the permanent magnet synchronous motor at each stage, and calculate a zero compensation angle according to the position signals output by the position sensor at each stage.

In one embodiment of the invention, the (u) required for each stage_α，u_β) Is sequentially (0, u)_m）、（u_m，0）、（0，-u_m）、（u_m0), wherein u_mis the voltage amplitude.

Further, (0, u)_m）、（u_m，0）、（0，-u_m）、（u_m0) the corresponding position signals are each θ₁、θ₂、θ₃And theta₄Wherein the null compensation angle theta is calculated by the following formula_c：θ_c=(θ₂+θ₄)/2。

It should be noted that the foregoing description of the specific implementation of the zero self-learning method for the position sensor of the permanent magnet synchronous motor is also applicable to the zero self-learning system for the position sensor of the permanent magnet synchronous motor in the embodiment of the present invention, so as to reduce redundancy. And will not be described in detail.

the zero-position self-learning system of the permanent magnet synchronous motor position sensor provided by the embodiment of the invention does not need a worker to manually adjust the voltage amplitude, can automatically reduce the workload of the worker through calculation, reduces the operation complexity of the zero-position self-learning process, and can simultaneously avoid the problems that the service life of the motor is reduced due to overcurrent and the motor cannot rotate due to too small current.

It should be noted that the logic and/or steps represented in the flowcharts or otherwise described herein, such as an ordered listing of executable instructions that can be considered to implement logical functions, can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For the purposes of this description, a "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic device) having one or more wires, a portable computer diskette (magnetic device), a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via for instance optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner if necessary, and then stored in a computer memory.

It should be understood that portions of the present invention may be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, the various steps or methods may be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any one or combination of the following techniques, which are known in the art, may be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application specific integrated circuit having an appropriate combinational logic gate circuit, a Programmable Gate Array (PGA), a Field Programmable Gate Array (FPGA), or the like.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.