阅读说明：本技术 高速大惯量负载用无铁芯无刷直流电机控制系统及方法 (Iron-core-free brushless direct current motor control system and method for high-speed large-inertia load ) 是由 郭婷婷 缪子超 邓丽辉 金琛 魏江峰 王建飞 李璐 于 2019-07-22 设计创作，主要内容包括：本发明涉及一种高速大惯量负载用无铁芯无刷直流电机控制系统及方法,其技术特点在于：包括无铁芯无刷直流电机、控制系统及其内部的驱动电路；所述控制系统包括信号检测模块、数字控制模块和线性功率驱动模块；所述内部的驱动电路包括：直流电源、电源滤波模块、三相逆变桥、梯形波反电动势无刷直流电机、三相电感、电流检测模块和数字控制器。本发明能够为高速大惯量飞轮用的无铁芯无刷直流电机的控制提供一种减小启动电流,减小电流换相波动的控制系统,并使大惯量系统能够稳定高速运转。(the invention relates to a control system and a control method of a coreless brushless direct current motor for high-speed large-inertia load, which are technically characterized in that: the brushless direct current motor comprises a coreless brushless direct current motor, a control system and a driving circuit inside the coreless brushless direct current motor; the control system comprises a signal detection module, a digital control module and a linear power driving module; the internal driving circuit includes: the device comprises a direct current power supply, a power supply filtering module, a three-phase inverter bridge, a trapezoidal wave back electromotive force brushless direct current motor, a three-phase inductor, a current detection module and a digital controller. The invention can provide a control system for reducing starting current and current commutation fluctuation for controlling a coreless brushless direct current motor for a high-speed large-inertia flywheel, and the large-inertia system can stably run at a high speed.)

1. a high-speed big inertia load is with no iron core brushless DC motor control system which characterized in that: the brushless direct current motor comprises a coreless brushless direct current motor, a control system and a driving circuit inside the coreless brushless direct current motor; the control system comprises a signal detection module, a digital control module and a linear power driving module;

The signal detection module comprises a current detection module, a rotating speed detection module and an A/D converter, and is respectively used for detecting the three-phase current and the rotating speed of the coreless brushless direct current motor, outputting the acquired three-phase current and rotating speed data to the digital control module through the A/D converter, and providing a control basis for the digital control module; the digital control module comprises a digital controller and is used for finishing calculation on the information provided by the signal detection module according to a PI control algorithm and outputting a control quantity; the linear power driving module comprises a high-speed isolation operational amplifier module, a high-power operational amplifier module and a driving module; the output end of the digital control module is connected with the coreless brushless direct current motor sequentially through the high-speed isolation operational amplifier module, the high-power operational amplifier module and the driving module, and is used for isolating and power amplifying the analog control signal output by the digital control module from the power level signal and then converting the analog control signal into a driving signal of high voltage and high current of a motor winding.

2. The control system of the coreless brushless direct current motor for the high-speed large-inertia load according to claim 1, wherein: the internal driving circuit includes: the device comprises a direct current power supply, a power supply filtering module, a three-phase inverter bridge, a trapezoidal wave counter electromotive force brushless direct current motor, a three-phase inductor, a current detection module and a digital controller;

The direct current power supply is used for providing stable voltage for the system; the power supply filtering module is used for filtering clutter brought by a power supply and comprises a filtering inductor and a filtering capacitor; the positive electrode of the direct current power supply is connected with one end of a filter inductor, the other end of the filter inductor is respectively connected with a filter capacitor and a three-phase inverter bridge, and the other end of the filter capacitor is connected with the negative electrode of the direct current power supply; the three-phase inverter bridge comprises six bridge arms, and each bridge arm consists of a switching tube and a diode; each diode is connected in parallel at the two ends of the collector and the emitter of the corresponding switch tube in an inverted way, and the three-phase inverter bridge is used for converting the direct current into the three-phase alternating current according to the states of the six switch tubes; a three-phase inductor is connected in series between the three-phase inverter bridge and a three-phase winding of the trapezoidal wave back electromotive force brushless direct current motor and is used for increasing the equivalent inductance of the system and playing a role in buffering current at the phase conversion moment;

Each circuit of the three-phase inductors is connected with a switch or a relay in parallel and used for switching out the three-phase inductors which are connected in series;

the current detection module comprises two Hall current sensors which are connected in series with a motor winding and used for detecting the current;

the digital controller is respectively connected with the trapezoidal wave back electromotive force brushless direct current motor and the current detection module, and is used for acquiring three-phase Hall signals HA, HB and HC of the trapezoidal wave back electromotive force brushless direct current motor, two-phase current signals ia and ib of the current detection module, a starting signal and a rotating speed reference signal, outputting six PWM wave signals to the trapezoidal wave back electromotive force brushless direct current motor 4, and controlling the on-off of six switching tubes.

3. the control method of the coreless brushless direct current motor control system for the high-speed large-inertia load according to claim 1 or 2, wherein: the method comprises the following steps:

Step 1, a starting stage: the motor is dragged to reach high speed by timing and increasing duty ratio in an open-loop control mode;

step 2, stable operation stage: and when the rotating speed is increased to the set rotating speed, switching to a closed-loop speed regulation mode, carrying out closed-loop speed regulation by adopting a PI control mode, and determining the control frequency according to the debugging result.

4. the control method of the coreless brushless direct current motor control system for the high-speed large-inertia load according to claim 3, wherein: the specific steps of the step 1 comprise:

(1) the Hall sensor detects the current position of the rotor, and the digital controller carries out phase change operation according to the rising edge, the falling edge and the current position transmitted by the Hall sensor;

(2) the digital controller collects the current of two phases which are currently conducted according to the signals of the Hall sensor, and if the current exceeds a set value, the PWM output is closed;

(3) When the rotating speed of the motor reaches 10000 revolutions and the counter electromotive force of the motor reaches half of the synchronous counter electromotive force, the three-phase inductor is switched out of the circuit through the digital controller.

5. The control method of the coreless brushless direct current motor control system for the high-speed large-inertia load according to claim 3, wherein: the specific steps of the step 2 comprise:

(1) the PI control mode is adopted, the outer ring is a rotating speed ring, the inner ring is a current ring, and the PI control mode is a comparison control mode and mainly plays a role in limiting current;

(2) The rotating speed loop PI controller obtains the output duty ratio of the controller according to the error between the current rotating speed and the reference rotating speed;

(3) the current loop detects the phase current of the motor, compares the phase current with a set maximum current value, and if the phase current is greater than a set value, the output duty ratio is reduced until the phase current is less than the set value;

(4) In the speed stabilizing stage, the rotation speed and the current of the motor are stabilized at the reference value under the combined action of the rotation speed loop and the current loop.

Technical Field

the invention belongs to the technical field of servo motor control, and relates to a coreless brushless direct current motor control system, in particular to a coreless brushless direct current motor control system and a coreless brushless direct current motor control method for high-speed large-inertia loads.

Background

the flywheel is a combination of a motor and a coaxial inertia body, changes the momentum moment of a rotor by changing the rotating speed, further generates a reaction moment proportional to the speed change rate of the rotor, and therefore the main purposes of the flywheel are storage of the rotational inertia and output of the moment to a carrier by momentum exchange with the carrier. Flywheel systems are commonly used in spacecraft attitude control and flywheel energy storage batteries. The rotating speed range and the speed control precision of the flywheel motor are greatly improved, when the rotating speed of the flywheel motor reaches ten thousand revolutions per minute, the energy storage density of the flywheel serving as a momentum storage device is even higher than that of chemical energy sources such as batteries, the energy conversion efficiency can reach 90% at most, the energy conversion efficiency is far higher than that of a traditional energy storage mode, and meanwhile, the instantaneous output power is far higher than that of the chemical energy sources.

the motor for high-speed flywheel energy storage should have the following basic performance requirements: high efficiency at rated power and low losses at no load. The high-speed flywheel energy storage system mainly comprises a flywheel rotor, a bearing, a motor, a power converter and a control unit.

in order to drive the large inertia load to move at a high speed and meet the requirement of low system power consumption, the selected motor is generally a coreless motor. The stator winding of the coreless motor has small inductance and resistance and small electric time constant, so that the problems of discontinuous winding current and large torque fluctuation under a voltage type controller can be caused. Meanwhile, the mechanical time constant is large, the inductance and the resistance of the motor are very small, and the control of the system current is also difficult in the system. The control problem of the motor for the high-speed large-inertia flywheel becomes the key point of the running quality of the flywheel.

through the search of the published patent documents, a published patent document relevant to the application of the invention is found:

the patent name of the system is a low-power-consumption control system of a small armature inductance permanent magnet brushless direct current motor, the publication number is CN1710801A, the system adopts a pre-step-down chopper mode to step down direct current power supply voltage according to different rotating speeds, and a three-phase inverter is only responsible for phase change. The motor is driven and the speed is regulated in the mode. The pre-arranged step-down chopper reduces the direct current voltage of the three-phase inverter, reduces the PWM peak value, further reduces the current peak value at the phase change moment and reduces the current pulsation. The invention adopts the three-phase inductors connected in series between the three-phase inverter and the motor to reduce the current pulsation, and the three-phase inverter is not only responsible for phase change, but also responsible for voltage and speed regulation.

Through technical analysis, the applicant believes that the above-mentioned patent publications and the present application are greatly different in technical solutions, particularly in control methods and circuit structures.

disclosure of Invention

The invention aims to overcome the defects of the prior art, provides a control system and a control method of a coreless brushless direct current motor for a high-speed large-inertia load, and can provide a control system for reducing starting current and current commutation fluctuation for controlling the coreless brushless direct current motor for a high-speed large-inertia flywheel, and enable the large-inertia system to stably run at a high speed.

the technical problem to be solved by the invention is realized by adopting the following technical scheme:

A control system of a coreless brushless direct current motor for high-speed large-inertia load comprises a coreless brushless direct current motor, a control system and a drive circuit inside the control system; the control system comprises a signal detection module, a digital control module and a linear power driving module;

The signal detection module comprises a current detection module, a rotating speed detection module and an A/D converter, and is respectively used for detecting the three-phase current and the rotating speed of the coreless brushless direct current motor, outputting the acquired three-phase current and rotating speed data to the digital control module through the A/D converter, and providing a control basis for the digital control module; the digital control module comprises a digital controller and is used for finishing calculation on the information provided by the signal detection module according to a PI control algorithm and outputting a control quantity; the linear power driving module comprises a high-speed isolated operational amplifier module, a high-power operational amplifier module and a driving module; the output end of the digital control module is connected with the coreless brushless direct current motor sequentially through the high-speed isolation operational amplifier module, the high-power operational amplifier module and the driving module, and is used for isolating the analog control signal output by the digital control module from the power level signal, amplifying the power of the analog control signal and converting the analog control signal into a driving signal of high voltage and high current of a motor winding after the power amplification.

further, the internal driving circuit includes: the device comprises a direct current power supply, a power supply filtering module, a three-phase inverter bridge, a trapezoidal wave counter electromotive force brushless direct current motor, a three-phase inductor, a current detection module and a digital controller; the direct current power supply is used for providing stable voltage for the system; the power supply filtering module is used for filtering clutter brought by a power supply and comprises a filtering inductor and a filtering capacitor; the positive electrode of the direct current power supply is connected with one end of a filter inductor, the other end of the filter inductor is respectively connected with a filter capacitor and a three-phase inverter bridge, and the other end of the filter capacitor is connected with the negative electrode of the direct current power supply; the three-phase inverter bridge comprises six bridge arms, and each bridge arm consists of a switching tube and a diode; each diode is connected in parallel at the two ends of the collector and the emitter of the corresponding switch tube in an inverted way, and the three-phase inverter bridge is used for converting the direct current into the three-phase alternating current according to the states of the six switch tubes; three-phase inductors are connected in series between the three-phase inverter bridge and three-phase windings of the trapezoidal wave back electromotive force brushless direct current motor and are used for increasing the equivalent inductance of the system and buffering current between phase change transients;

Each path of the three-phase inductor is connected with a switch or a relay in parallel and used for switching out the three-phase inductors connected in series;

The current detection module comprises two Hall current sensors which are connected with a motor winding in series and used for detecting the current;

The digital controller is respectively connected with the trapezoidal wave back electromotive force brushless direct current motor and the current detection module, is used for collecting three-phase Hall signals HA, HB and HC of the trapezoidal wave back electromotive force brushless direct current motor, two-phase current signals ia and ib of the current detection module, a starting signal and a rotating speed reference signal, outputs six PWM wave signals to the trapezoidal wave back electromotive force brushless direct current motor 4, and is used for controlling the on and off of the switching tube.

A control method of a coreless brushless direct current motor for high-speed large-inertia load comprises the following steps:

Step 1, a starting stage: the motor is dragged to reach high speed by timing and increasing duty ratio in an open-loop control mode;

step 2, stable operation stage: when the rotating speed is increased to the set rotating speed, switching to a closed-loop speed regulation mode, performing closed-loop speed regulation by adopting a PI control mode, and determining the control frequency according to a debugging result;

further, the specific steps of step 1 include:

(1) The Hall sensor detects the current position of the rotor, and the digital controller carries out phase change operation according to the rising edge, the falling edge and the current position transmitted by the Hall sensor;

(2) The digital controller collects the current of two phases which are currently conducted according to the signals of the Hall sensor, and if the current exceeds a set value, the PWM output is closed;

(3) when the rotating speed of the motor reaches 10000 revolutions and the counter electromotive force of the motor reaches half of the synchronous counter electromotive force, the three-phase inductor is switched out of the circuit through the digital controller.

Further, the specific steps of step 2 include:

(1) the PI control mode is adopted, the outer ring is a rotating speed ring, the inner ring is a current ring, and the PI control mode is a comparative control and mainly plays a role in limiting current;

(2) the rotating speed loop PI controller obtains the output duty ratio of the controller according to the error between the current rotating speed and the reference rotating speed;

(3) The current loop detects the phase current of the motor, compares the phase current with a set maximum current value, and if the phase current is greater than a set value, the output duty ratio is reduced until the phase current is less than the set value;

(4) in the speed stabilizing stage, the rotation speed and the current of the motor are stabilized at the reference value under the combined action of the rotation speed loop and the current loop.

The invention has the advantages and positive effects that:

1. According to the invention, three-phase inductors are connected in series between the inverter and the motor winding, and the three inductors are respectively connected with a switch in parallel and used for cutting out the inductors from the circuit, so that the equivalent inductance of the system is increased, the current fluctuation at the phase commutation moment is inhibited, and the problem of phase commutation current distortion caused by small inductance of the motor is solved.

2. the invention adopts a 48V direct current power supply to provide stable voltage for a system, the power supply filtering module filters noise waves brought by the power supply to prevent the noise waves from damaging a hardware circuit board, and the three-phase inverter bridge converts direct current into three-phase alternating current according to control input. Three-phase inductance is connected in series between the three-phase inverter and the motor, so that the equivalent inductance of the system is increased, the current at the phase commutation moment is buffered, and the current is prevented from being distorted.

3. In the speed increasing process, the motor rotating speed is detected through the Hall sensor, and the duty ratio of the system is adjusted. When the rotating speed is close to the given rotating speed, the rotating speed is controlled in a closed loop mode, and the rotating speed can be accurately adjusted.

4. The driving mode of the invention adopts a synchronous rectification mode, can effectively reduce the switching loss of an inverter bridge operated by large current, and has larger current in operation because the resistance and the inductance of a coreless motor are very small. If the traditional three-phase six-state driving mode is adopted, during the period that the circuit is not conducted, the diode which is connected with the switch tube in an anti-parallel mode is used for follow current, and the system uses the diode which is connected with the switch tube in an anti-parallel mode to conduct follow current. The tube voltage drop of the diode is 0.2-0.6V, and current flows through the diode during the closing period of the switch tube, so that the system loss is large. The synchronous rectification mode adopts switch tube MOSFET follow current, MOSFET conduction voltage drop is small, switching loss of an inverter bridge in current operation can be effectively reduced in the operation of a large-current circuit, and the operation efficiency of the system is improved. In the whole operation process, three-phase current is detected, the current sampling frequency is equal to the PWM frequency, and invalid control strategies can be prevented from being invalid due to sampling of invalid current.

5. The invention adopts a control mode of constant voltage frequency ratio at the speed-up stage, and prevents the current from sudden change caused by the change of the duty ratio at the starting stage and damaging the winding due to the exceeding of the maximum bearing current of the motor.

6. The current detection adopts the non-contact Hall current sensor, so that the current detection precision and the detection range are improved.

7. The three-phase inductor is switched out in an electronic control mode, and a microcontroller gives a signal, so that the method is simple and convenient and has high safety.

8. the operation of the invention is divided into two stages, a starting stage and a stable operation stage. The system has long starting time, the starting stage drives the motor to high speed by adopting a mode of increasing duty ratio in a timing mode in an hour unit, the three-phase inductor is switched out by giving a signal through the digital controller in the middle starting period, and then the speed is continuously increased. When the stable speed is to be reached, closed-loop control is carried out, the control scheme adopts PI control, and the control frequency is 1 Hz. And when the speed is raised and enters a speed stabilizing stage, the rotating speed of the system is controlled to be stabilized at the set rotating speed by adopting a PI (proportional integral) regulation mode.

9. the hardware circuit design of the invention fully considers the hardware design scheme of low voltage and large current.

Drawings

FIG. 1 is a block diagram of the control system of the present invention;

FIG. 2 is a schematic diagram of the control system circuit connections of the present invention;

FIG. 3 is a schematic diagram of the system operation and control flow of the present invention;

fig. 4 is a flow chart of a control method of the present invention.

Detailed Description

the embodiments of the invention will be described in further detail below with reference to the accompanying drawings:

A coreless brushless DC motor control system for high-speed large-inertia load, as shown in FIG. 1 and FIG. 2, comprises a coreless brushless DC motor, a control system and a driving circuit inside the coreless brushless DC motor;

The control system comprises a signal detection module, a digital control module and a linear power driving module;

the signal detection module comprises a current detection module, a rotating speed detection module and an A/D converter, and is respectively used for detecting the three-phase current and the rotating speed of the coreless brushless direct current motor, outputting the acquired three-phase current and rotating speed data to the digital control module through the A/D converter, and providing a control basis for the digital control module; the digital control module comprises a digital controller and is used for finishing calculation on the information provided by the signal detection module according to a PI control algorithm and outputting a control quantity; the linear power driving module comprises a high-speed isolated operational amplifier module, a high-power operational amplifier module and a driving module; the output end of the digital control module is connected with the coreless brushless direct current motor sequentially through the high-speed isolation operational amplifier module, the high-power operational amplifier module and the driving module, and is used for isolating and amplifying a control signal of an analog quantity output by the digital control module from a power level signal and converting the control signal into a driving signal of high voltage and high current of a motor winding to realize the control of the motor;

in this embodiment, the digital control module adopts STM32F103 series microcontroller of ST company, and this series of chips can produce six complementary PWM ripples, and the dominant frequency can reach 72M, and the IO mouth is abundant, has 3 AD modules of 12 bits, and the resource is abundant, and is very suitable for accomplishing the control of motor. The chip carries out PI control algorithm operation and finally outputs six PWM waves to the high-speed isolation operational amplifier module. The isolated pwm wave is sent to the operational amplifier by the high-speed isolation operational amplifier module, so that the pwm wave signal has driving capability.

In this embodiment, the power driving module adopts an IRF2110 chip, and the driving chip performs overcurrent and overvoltage protection, so that a good protection effect is provided for current overcurrent which may occur during the operation of the coreless brushless dc motor, and the overcurrent protection can achieve dual protection of hardware and software. The pwm wave of the operational amplifier is used as the input of an IRS2110 driving chip, and the chip outputs six driving signals to control the on-off of the switching tube.

in this embodiment, the signal detection module mainly detects the rotation speed and the current. The current detection module adopts a non-contact Hall current sensor, the method detects currents of two phases, the third phase current can be obtained by calculation, a non-contact current detection mode is adopted to detect currents in a wider range, the detection precision is higher, the influence of temperature is small, and the method is very suitable for detection application in large-current occasions. The input of the signal detection module is the current of the A phase and the B phase and the Hall position signal, and the output is the current magnitude and the rotating speed value of the A phase and the B phase.

As shown in fig. 3, the internal driving circuit includes: the device comprises a 48V direct-current power supply 1, a power supply filtering module 2, a three-phase inverter bridge 3, a trapezoidal wave counter electromotive force brushless direct-current motor 4, a three-phase inductor 5, a current detection module 6 and a digital controller 7;

the 48V direct current power supply 1 is used for providing stable voltage for a system;

the power supply filtering module 2 is used for filtering noise waves brought by a power supply and preventing the noise waves from damaging a hardware circuit board and comprises a filtering inductor and a filtering capacitor; the positive electrode of the 48V direct-current power supply is connected with one end of a filter inductor, the other end of the filter inductor is respectively connected with a filter capacitor and a three-phase inverter bridge, and the other end of the filter capacitor is connected with the negative electrode of the 48V direct-current power supply 1;

the three-phase inverter bridge 3 comprises six bridge arms, and each bridge arm consists of a switching tube and a diode; each diode is connected in parallel with the two ends of the collector and the emitter of the corresponding switch tube in an inverted way, and the three-phase inverter bridge 3 is used for converting the direct current into the three-phase alternating current according to the states of the six switch tubes.

And a three-phase inductor 5 is connected in series between the three-phase inverter bridge 3 and the three-phase winding of the trapezoidal wave back electromotive force brushless direct current motor 4, and is used for increasing the equivalent inductance of the system, buffering the current at the phase commutation moment and preventing the current from being distorted.

Each path of the three-phase inductor is connected with a switch or a relay in parallel and used for switching out the three-phase inductors connected in series;

in this embodiment, the series three-phase inductor is connected to the system only when the trapezoidal wave back electromotive force brushless direct current motor 4 is accelerated, and when the high rotation speed is reached, the inductor is cut off through the digital controller 7, so that the problem that the motor cannot reach the synchronous rotation speed due to too much equivalent partial pressure of the inductor under the high frequency is avoided, and the system loss is high.

the current detection module 6 comprises two Hall current sensors, the Hall current sensors are connected with a motor winding in series, a three-phase winding of the trapezoidal wave back electromotive force brushless direct current motor 4 penetrates through the Hall current sensors, and the Hall current sensors can detect the current according to the Hall effect.

the digital controller 7 is respectively connected with the trapezoidal wave back electromotive force brushless direct current motor 4 and the current detection module, and is used for acquiring three-phase hall signals HA, HB and HC of the trapezoidal wave back electromotive force brushless direct current motor 4 and two-phase current signals ia and ib of the current detection module, as well as a starting signal and a rotating speed reference signal, outputting six PWM wave signals to the trapezoidal wave back electromotive force brushless direct current motor 4, and controlling the on and off of six power switching tubes.

In this embodiment, the switch tube is a MOSFET device with a model number IRF 4110;

In this embodiment, the microprocessor of the present invention is the STM32F103 series, the model of the contactless current sensor is ACS723, and the driver chip is IRF2110.

as shown in fig. 4, a method for controlling a coreless brushless dc motor for a high-speed large-inertia load includes the following steps:

Step 1, a starting stage: the motor is dragged to reach high speed by timing and increasing duty ratio in an open-loop control mode;

The specific steps of the step 1 comprise:

(1) the Hall sensor detects the current position of the rotor, and the digital controller carries out phase change operation according to the rising edge, the falling edge and the current position transmitted by the Hall sensor;

(2) the digital controller collects the current of two phases which are currently conducted according to the signals of the Hall sensor, and if the current exceeds a set value, the PWM output is closed;

(3) when the rotating speed of the motor reaches 10000 revolutions and the counter electromotive force of the motor reaches half of the synchronous counter electromotive force, the three-phase inductor is switched out of the circuit through the digital controller.

step 2, stable operation stage: when the rotating speed is increased to the set rotating speed, switching to a closed-loop speed regulation mode, performing closed-loop speed regulation by adopting a PI control mode, and determining the control frequency according to a debugging result;

the specific steps of the step 2 comprise:

(1) The PI control mode is adopted, the outer ring is a rotating speed ring, the inner ring is a current ring, and the PI control mode is a comparative control and mainly plays a role in limiting current;

(2) The rotating speed loop PI controller obtains the output duty ratio of the controller according to the error between the current rotating speed and the reference rotating speed;

(3) The current loop detects the phase current of the motor, compares the phase current with a set maximum current value, and if the phase current is greater than a set value, the output duty ratio is reduced until the phase current is less than the set value;

(4) in the speed stabilizing stage, the rotation speed and the current of the motor are stabilized at the reference value under the combined action of the rotation speed loop and the current loop.

the working process of the invention is as follows:

a starting stage: the Hall sensor detects the current position of the rotor, and the digital controller carries out phase change operation according to the rising edge, the falling edge and the current position transmitted by the Hall sensor. For a large-inertia system, the starting time is long, the mechanical time constant is large, and if closed-loop control is adopted in the starting stage, the control parameter adjustment is difficult, so that poor effects are often brought. Therefore, the starting phase of the present invention adopts an open-loop method, and the motor is driven to reach a high speed by a timed and increased duty ratio. In the method, enough time is reserved for waiting for the increase of the rotating speed and the establishment of the back electromotive force of the motor every time the duty ratio is increased, and the starting current in the starting stage is reduced. The current detection frequency is equal to the PWM frequency, the PWM adopts a central alignment mode, the digital controller samples current when the PWM timer generates counting overflow, the selection of the collection phase is determined according to the current position of the Hall sensor, the two-phase current of the current conduction phase is collected, and the collection of invalid current is avoided to influence the control implementation. If the current exceeds the set value, the PWM output is turned off. When the rotating speed of the motor reaches 10000 revolutions, the counter electromotive force of the motor reaches half of the synchronous counter electromotive force, if the three-phase inductor is cut off at the moment, the current commutation pulsation is not large, and the current peak value can be inhibited. Therefore, in the invention, three switches are connected in parallel on the three-phase inductor, the on and off of the switches are controlled by the digital controller, when the rotating speed reaches 10000 revolutions, the counter electromotive force of the motor reaches half of the synchronous counter electromotive force, the level is output through an IO port of a control chip of the digital controller, the switches are closed, and the three-phase inductor is switched out of a circuit. After the series three-phase inductance is switched out of the circuit, the circuit is continuously operated in the original speed increasing mode, and when the rotating speed reaches 0.9 x set rotating speed, the circuit enters a closed-loop operation state, and closed-loop speed regulation is started. The rotating speed is regulated by PI control, and when the rotating speed is gradually increased to be close to the set rotating speed, the rotating speed is closed loop. Because the inertia of the system is large, the control frequency cannot be too high, the duty ratio is maintained for 1 second after the closed loop changes every time, and the closed loop enters the closed loop again to prevent the controller from accumulating and saturating.

And (3) a stable operation stage: and PI control is adopted in the stable operation stage, the control frequency of a large-inertia system is very low, and the control frequency is 1Hz according to the modification of a debugging result. The target rotating speed of the motor is 20000 revolutions per minute, and the operation mode is switched to closed-loop speed regulation when 19000 revolutions occur, so that the motor stably operates at the set rotating speed.

and a logic relation table exists between the Hall state and the conducted bridge arms, and the corresponding bridge arms are gated according to the detected Hall state. The advanced TIMER TIMER1 and the corresponding IO port are configured through software, the duty ratio of output pulses is adjusted according to control output, and finally the microcontroller outputs complementary PWM waves with dead zone protection. Six paths of PWM waves output by the microcontroller are amplified and isolated and output to six MOSFET switching tubes to drive the motor to operate.

It should be emphasized that the described embodiments of the present invention are illustrative rather than restrictive, and thus, the present invention is not limited to the described embodiments, but other embodiments, which are derived from the technical solutions of the present invention by those skilled in the art, also belong to the protection scope of the present invention.