CN104393801A - Brush-less direct current motor speed regulating device and speed regulating method - Google Patents

Abstract

The invention discloses a method for speed regulation of a brushless direct current motor. The steps are: capturing and comparing a module to output a PWM waveform; the PWM waveform is connected to an interrupt signal, the PWM waveform detects a high level and immediately enters the interrupt, and the current sampling module immediately samples and flows through the bus resistance The current obtained by the sampling is sent to the current regulator, and the current regulator outputs the duty ratio according to the given current and the current obtained by the sampling; the duty ratio is used to control the three-phase bridge inverter The upper bridge power tube is turned on and off to control the effective voltage applied to the brushless DC motor to adjust its speed. This speed regulation method can solve the existing problems of high cost and low reliability of phase current sampling and motor torque ripple of DC bus sampling. The invention also discloses a speed regulating device using the aforementioned brushless DC motor speed regulating method.

Description

A brushless DC motor speed control device and speed control method

technical field

The invention belongs to the field of speed control of brushless direct current motors, in particular to a brushless direct current motor speed regulating device and speed regulating method based on direct current bus current sampling.

Background technique

Brushless DC motor speed control system is a new type of speed control system. Its speed and current double closed-loop digital control system can be divided into hysteresis control and PI control according to different current control strategies. The current hysteresis control makes the motor work in the conduction mode. By comparing the given current value with the feedback current value in real time, the power tube is controlled to be turned on or off within one cycle to realize the regulation of the current. The current PI control makes the motor work in the 120° conduction mode, and the current regulator generates an appropriate duty cycle, and according to the position of the permanent magnet rotor, it gives the driving signals of 6 power tubes in a control cycle, and controls the power applied to the motor. effective voltage to regulate its rotational speed. There are two commonly used sampling feedback methods in brushless DC motor control systems: phase current sampling and DC bus sampling. However, phase current sampling requires two current Hall sensors, which increases the cost and significantly reduces system reliability; DC bus sampling The method detects the current i _dc flowing through it through the bus resistor R _S , which has a simple structure and low cost. However, during the off period of the power tube PWM modulation, i _dc = 0, which cannot reflect the torque current of the motor. If it is not processed, the i _dc Feedback to the current regulator will cause torque ripple in the motor.

Based on the foregoing, the existing motor speed control technology needs to be improved, and this case arises from this.

Contents of the invention

The purpose of the present invention is to provide a brushless DC motor speed control device and speed control method, which can solve the existing problems of high cost and low reliability of phase current sampling and motor torque ripple of DC bus sampling.

In order to achieve the above object, the solution of the present invention is:

A brushless DC motor speed control device, the applied brushless DC motor circuit includes a DC power supply, a bus resistor, a three-phase bridge inverter and a DC motor, wherein the positive pole of the DC power supply is connected to the three-phase bridge inverter One input terminal of the DC power supply, the negative pole of the DC power supply is connected to the other input terminal of the three-phase bridge inverter through the bus resistor, and the three output terminals of the three-phase bridge inverter are correspondingly connected to the three-phase windings of the brushless DC motor The speed regulating device includes a PWM controller, a current sampling module and a current regulator, and the current sampling module samples the current flowing through the bus resistance under the control of the PWM controller, and sends it into the current regulator, and the current The regulator outputs the duty cycle, and adjusts the duty cycle of the upper bridge power tube in the three-phase bridge inverter, so as to adjust the speed by controlling the voltage applied to the brushless DC motor.

The above-mentioned PWM controller includes a PWM timer, a capture comparison module and an interrupt module, the PWM timer is connected to the positive input of the capture comparison module, and the reverse input of the capture comparison module is used to input an internal reference signal, and the capture comparison module The output end of the interrupt module is connected to the interrupt module, and the output end of the interrupt module is connected to the current sampling module. The capture comparison module controls the interrupt module to generate an interrupt signal by outputting PWM waveforms, thereby controlling the action of the current sampling module.

A speed regulating method based on the aforementioned brushless DC motor speed regulating device, comprising the steps of:

(1) capture and compare module output PWM waveform;

(2) The PWM waveform is connected to the interrupt signal, and the PWM waveform detects a high level and immediately enters the interrupt;

(3) After entering the interruption, the current sampling module immediately samples the current flowing through the bus resistance;

(4) Send the current obtained by the sampling into the current regulator;

(5) The current regulator obtains the current output duty ratio according to the given current and the sampling;

(6) using the duty ratio to control the opening and closing of the upper bridge power tube in the three-phase bridge inverter;

(7) Control the effective voltage applied to the brushless DC motor to adjust its speed.

In the above step (1), the positive input terminal of the capture comparison module is connected to the value generated by the PWM timer, and the negative input terminal is connected to the internal reference signal, and the PWM waveform is output after comparing the two.

In the above step (5), the current regulator subtracts the given current from the current obtained by sampling, and then performs a PID operation to obtain the duty ratio.

The capture and comparison module above outputs a symmetrical equilateral triangle PWM carrier signal, and the PWM timer works in an increase-decrease mode.

After the above scheme is adopted, the present invention makes the sampling value closer to the average value of the torque current by adopting the H_PWM_L_ON modulation mode, which well solves the problems of high cost and low reliability of phase current sampling and motor torque pulsation of DC bus sampling .

Description of drawings

Fig. 1 is the application circuit connection diagram of speed regulating device of the present invention;

Fig. 2 is a structural block diagram of the speed regulating device of the present invention;

Fig. 3 is a flowchart of the speed regulating method of the present invention.

Detailed ways

The technical solutions of the present invention will be described in detail below in conjunction with the accompanying drawings.

The present invention provides a brushless DC motor speed control device, which is used to control the speed of the brushless DC motor. As shown in Figure 1, the brushless DC motor circuit includes a DC power supply, a bus resistance R _S , a three-phase Bridge inverter and DC motor, wherein the positive pole of the DC power supply is connected to one input terminal of the three-phase bridge inverter, the negative pole of the DC power supply is connected to the other input terminal of the three-phase bridge inverter through the bus resistance, and The three output ends of the three-phase bridge inverter are correspondingly connected to the three-phase windings of the brushless DC motor, which is a common connection mode of the existing brushless DC motor circuit, and will not be repeated here.

As shown in Figure 2, the speed regulating device includes a PWM controller, a current sampling module and a current regulator. Under the control of the PWM controller, the current sampling module samples the current flowing through the bus resistance and sends it to the current regulator The current regulator outputs a duty cycle to adjust the duty cycle of the power tube of the upper bridge in the three-phase bridge inverter, so as to adjust the speed by controlling the voltage applied to the brushless DC motor.

In this embodiment, the PWM controller includes a PWM timer, a capture comparison module and an interrupt module, the PWM timer is connected to the positive input terminal of the capture comparison module, and the reverse input terminal of the capture comparison module is used for input Triangular wave, as internal reference signal, after described capture comparison module compares the numerical value that aforementioned PWM timer produces with triangular wave, output square wave signal, as capture value; Capture the output end of comparison module to connect interruption module, and the output end of interruption module Connect the current sampling module, and the capture comparison module controls the interrupt module to generate an interrupt signal by outputting PWM waveforms, thereby controlling the action of the current sampling module.

In conjunction with Fig. 3, the present invention also provides a speed regulating method based on the aforementioned brushless DC motor speed regulating device, comprising the following steps:

(1) capture and compare module output PWM waveform;

(2) The PWM waveform is connected to the interrupt signal, and the PWM waveform detects a high level and immediately enters the interrupt;

(3) After entering the interruption, the current sampling module immediately samples the current i _dc flowing through the bus resistance R _S ;

(4) Send the current i _dc obtained by the sampling into the current regulator;

(5) The current regulator outputs the duty cycle according to the given current i _dc ^* and the current i _dc obtained by the sampling, specifically subtracting the two, and then performing a PID operation to obtain;

(6) using the duty ratio to control the opening and closing of the upper bridge power tube in the three-phase bridge inverter;

(7) Control the effective voltage applied to the brushless DC motor to adjust its speed.

To sum up, the present invention adopts H_PWM_L_ON modulation, which is to perform PWM modulation on the upper bridge power tube of the three-phase bridge inverter and keep the lower bridge power tube on. Ideal characteristics, R _S is the sampling resistance, and i _dc is the sampling current. In the H_PWM_L_ON modulation mode, the fluctuation of the phase current during the commutation process of the upper and lower bridges is equal and very small, and the torque ripple caused by the commutation is also very small.

The present invention first adopts a symmetrical equilateral triangle PWM carrier signal, which can be increased or decreased by changing the PWM timer, so that each interrupt time is in the effective period of PWM high level, which ensures that the modulated power tube is in the open state at this moment ;Secondly, the current is sampled immediately after entering the interrupt, and the current sampling time of R _S is just in the high-level effective period of the PWM cycle. At this time, the current passing through R _S is approximately the average value of the torque current of this cycle. The missampling of the torque current during the tube off period accurately reflects the actual electromagnetic torque.

The above embodiments are only to illustrate the technical ideas of the present invention, and can not limit the protection scope of the present invention with this. All technical ideas proposed in accordance with the present invention, any changes made on the basis of technical solutions, all fall within the protection scope of the present invention. Inside.

Claims (6)

1. brshless DC motor speed regulating device, the brshless DC motor circuit of its application comprises DC power supply, bus bar resistance, three-phase bridge type converter and direct current machine, wherein, the positive pole of DC power supply connects an input of three-phase bridge type converter, the negative pole of DC power supply connects another input of three-phase bridge type converter via bus bar resistance, and three of three-phase bridge type converter outputs are corresponding with the three-phase windings of brshless DC motor connects; It is characterized in that:

Described speed regulating device comprise PWM controller, current sample module and current regulator, described current sample module is under the control of PWM controller, sample streams is through the electric current of bus bar resistance, and send into current regulator, described current regulator output duty cycle, regulate the duty ratio of upper bridge power tube in three-phase bridge type converter, thus carry out adjusting rotary speed by controlling the voltage put on brshless DC motor.

2. a kind of brshless DC motor speed regulating device as claimed in claim 1, it is characterized in that: described PWM controller comprises PWM timer, capture compare module and interrupt module, described PWM timer connects the positive input of capture compare module, and the reverse input end of capture compare module is for inputting internal reference signal, the output disconnecting module of capture compare module, and the output of interrupt module connects current sample module, capture compare module produces interrupt signal by exporting PWM Waveform Control interrupt module, thus control the action of current sample module.

3., based on a speed regulating method for brshless DC motor speed regulating device as claimed in claim 2, it is characterized in that comprising the steps:

(1) capture compare module exports PWM waveform;

(2) PWM waveform connects interrupt signal, and PWM waveforms detection goes out high level and just enters interruption at once;

(3) have no progeny in entering, current sample module is sampled at once and is flow through the electric current of bus bar resistance;

(4) electric current described sampling obtained sends into current regulator;

(5) the electric current output duty cycle that obtains according to given electric current and described sampling of current regulator;

(6) open and shutoff with bridge power tube upper in described Duty ratio control three-phase bridge type converter;

(7) effective voltage controlling to put on brshless DC motor is to regulate its rotating speed.

4. a kind of method for regulating speed of brushless direct current motor as claimed in claim 3, it is characterized in that: in described step (1), the positive input of capture compare module connects the numerical value of PWM timer generation, and reverse input end connects internal reference signal, and the two is exported PWM waveform more afterwards.

5. a kind of method for regulating speed of brushless direct current motor as claimed in claim 3, is characterized in that: in described step (5), and then the current subtraction that given electric current and described sampling obtain by current regulator is carried out PID arithmetic and obtained duty ratio.

6. a kind of method for regulating speed of brushless direct current motor as claimed in claim 3, is characterized in that: described capture compare module exports symmetrical equilateral triangle PWM carrier signal, and PWM runs is in increase and decrease pattern.