CN219068089U

CN219068089U - High-precision pulse width modulation coding system applied to stepping motor

Info

Publication number: CN219068089U
Application number: CN202221960818.4U
Authority: CN
Inventors: 黄海滨; 马辉
Original assignee: Hangzhou Sitai Microelectronics Co ltd
Current assignee: Hangzhou Sitai Microelectronics Co ltd
Priority date: 2022-07-28
Filing date: 2022-07-28
Publication date: 2023-05-23
Anticipated expiration: 2032-07-28

Abstract

The utility model relates to the technical field of stepping motor driving, in particular to a high-precision pulse width modulation coding system applied to a stepping motor, which can guarantee accurate and stable control of the operation of the stepping motor and is simple in system, and comprises an H bridge, wherein the H bridge comprises four MOS tubes and a load motor.

Description

High-precision pulse width modulation coding system applied to stepping motor

Technical Field

The utility model relates to the technical field of stepping motor driving, in particular to a high-precision pulse width modulation coding system applied to a stepping motor.

Background

In the H-bridge driving circuit, as shown in FIG. 1, four MOS transistors (101-104) form an H-bridge for driving a motor coil. The driving voltage of the H bridge (the gate voltage applied to the four MOS transistors 101-104) adopts a pulse width modulation mode (also called a chopping mode), and the driving voltage is composed of pulse width modulation periods with fixed frequency: when the H-bridge works, if the MOS tube 101 and the MOS tube 104 are conducted simultaneously, the current direction is shown by a solid arrow 107 in the figure. When the H-bridge drive reaches the required current, the

MOS transistors

101 and 104 will be turned off, and since the motor load is a winding coil, it presents an inductance characteristic, and after the drive is turned off, the coil current will continue to flow (freewheel characteristic) according to the original direction, and at this time, there are two freewheel (decay) modes:

the first is to turn off the

upper MOS transistors

101, 103 and turn on the

lower MOS transistors

102, 104, at which time the current direction is shown by the dashed arrow 106. Because of its operating characteristics, the current of this freewheel mode is smaller, so the voltage difference across the load drops more slowly, known as slow decay;

the second is to turn off the

original MOS transistors

101 and 104 and turn on the

reverse MOS transistors

102 and 103, and the current direction is shown by the dotted arrow 105. The current of this freewheel is large, so the voltage difference across the load drops faster, which is called fast decay.

The rapid attenuation and the slow attenuation have the advantages that the rapid attenuation can enable the current to be attenuated as soon as possible, so that waveform distortion caused by too rapid current waveform change is avoided, but the rapid change can show larger current fluctuation, and is unfavorable for stable low-noise operation of the motor; on the contrary, slow decay is easy to distort when the current waveform changes fast, but the slow change can show smoother current waveform and motor running state; in practical application, a fast/slow attenuation combination mode is adopted, namely: in the same pulse width modulation period, by comparing the currents flowing through the bridge arm MOS tube, a fast attenuation mode is adopted when the currents are larger, and a slow attenuation mode is adopted when the currents are smaller. Typically, the hybrid attenuation combines the advantages of both fast and slow attenuation, greatly improving the H-bridge attenuation performance. However, since the current fluctuation of the fast attenuation is larger, and each current value is controlled through feedback, the mode can introduce larger control fluctuation, and the mixed attenuation still has the defect of larger current fluctuation. Meanwhile, as the mixed attenuation needs to detect the tail current of the H bridge at the corresponding moment at high speed, the complexity of a control system is improved to a certain extent.

Disclosure of Invention

In order to solve the problems of complex control system and poor running stability of the existing stepping motor, the utility model provides a high-precision pulse width modulation coding system applied to the stepping motor, which can ensure accurate and stable control of the running of the stepping motor and has simple system.

The technical scheme is as follows: the high-precision pulse width modulation coding system applied to the stepping motor comprises an H bridge, wherein the H bridge comprises four MOS tubes and a load motor, and is characterized by further comprising a digital control module, wherein a control signal end of the digital control module is connected with the four MOS tubes, the load motor is connected with a counter electromotive force equivalent power supply, two MOS tubes of a lower bridge arm of the H bridge are respectively connected with an input end of a tail current induction resistor and an analog-to-digital converter, an output end of the analog-to-digital converter is connected with the digital control module, the digital control module comprises a current amplitude control PID module and a counter electromotive force compensation control PID module, an output end of the current amplitude control PID module is connected with an input end of a voltage driving sine wave generator, an output end of the voltage driving sine wave generator and an output end of the counter electromotive force compensation control PID module are both connected with two input ends of a correction waveform generator, an output end of the correction waveform generator is connected with an input end of the H bridge, an output end of the H bridge is connected with an input end of a sampling feedback module containing the counter electromotive force of the analog-to-digital converter, an output end of the counter electromotive force feedback module is connected with a target value of the counter electromotive force amplitude control PID module, and an output end of the counter electromotive force amplitude control PID module is connected with another output end of the counter electromotive force amplitude control PID module.

The sampling feedback module is further characterized by comprising a sampling point selection module and a subsequent digital control module;

the load motor and the H bridge are one or more.

After the utility model is adopted, the digital control module is utilized to carry out PID processing on the H-bridge feedback value and the system preset value to obtain stable and reliable waveform, and the high-precision sine wave pulse width modulation code is defined from the pulse width modulation voltage, thereby achieving the purpose of precisely controlling the stepping motor and having simple system.

Drawings

FIG. 1 is a schematic diagram of a prior H-bridge circuit;

FIG. 2 is a schematic diagram of the circuit control of the present utility model;

FIG. 3 is a schematic diagram showing distortion of a conventional driving waveform;

FIG. 4 is a schematic diagram of a sample feedback module;

fig. 5 is a schematic diagram of waveform sampling.

Detailed Description

The high-precision pulse width modulation coding system applied to the stepping motor comprises an H bridge, the H bridge comprises four MOS tubes and a load motor, the high-precision pulse width modulation coding system further comprises a digital control module, a control signal end of the digital control module is connected with the four MOS tubes, the load motor is connected with a counter electromotive force equivalent power supply, two MOS tubes of a lower bridge arm of the H bridge are respectively connected with a tail current sensing resistor and an input end of an analog-to-digital converter, an output end of the analog-to-digital converter is connected with a digital control module, the digital control module comprises a current amplitude control PID module and a counter electromotive force compensation control PID module, an output end of the current amplitude control PID module is connected with an input end of a voltage driving sine wave generator, an output end of the voltage driving sine wave generator and an output end of the counter electromotive force compensation control PID module are both connected with two input ends of a counter electromotive force correction waveform generator, an output end of the counter electromotive force correction waveform generator is connected with an input end of the H bridge, an output end of the H bridge is connected with an input end of a sampling feedback module comprising the analog-to-digital converter, the sampling feedback module further comprises a sampling point selection module and a subsequent digital control module, an output end of the sampling feedback module is respectively connected with an output end of the current amplitude control PID module and an output end of the current amplitude control PID module, and a target value of the counter electromotive force compensation PID module can be connected with the counter electromotive force control element, and a counter electromotive force compensation current of the counter electromotive force compensation current compensation element can be input to the counter electromotive force compensation current compensation element of the counter electromotive force compensation element, and the counter electromotive force compensation element can be a counter electromotive force current compensation current of the counter electromotive force compensation current element, and the counter electromotive force of the counter current element can be a counter electromotive force current.

The digital control module 200 in fig. 2 converts the sine wave drive voltage (301 in fig. 3) into a PWM waveform and drives the MOS transistors 204-207 on the H-bridge. The purpose of the drive at this time is that the phase current flowing through the load on the H-bridge exhibits a sinusoidal character, i.e.: a sine wave current corresponding to the driving voltage 301. However, as the motor 208 starts to rotate, its stator coils cut magnetic lines of force causing back emf to be generated, such as: the back emf equivalent power supply shown at 209 in fig. 2 has a waveform shown as dashed waveform 302 in fig. 3. It should be noted that, along with the rotation of the magnetic force lines inside the motor, the direction of the counter electromotive force 209 is also continuously changed (302 waveform); just because of the presence of the back emf 209 (302 waveform), the voltage across the load on the H-bridge is not actually sinusoidal as shown at 301, thus resulting in a current 303 flowing through the load that does not correspond exactly to the sinusoidal current of 301, but is instead a distorted waveform affected by the back emf.

The drive waveform 301, back emf waveform 302, and current waveform 303 flowing through the load illustrated in fig. 3 have two characteristics: first, since the back emf waveform 302 always lags the drive waveform 301 in phase, its effect on the current waveform flowing through the load causes its distortion on the basis of a sinusoidal waveform, i.e., the current waveform 303 is no longer a sinusoidal waveform; second, this distortion is also reflected in the amplitude of the current waveform 303, which is no longer the amplitude defined by the simple drive waveform 301; the above two effects become more pronounced with increasing load speed or with the use of motors of different characteristics. As shown in waveforms 304 to 306 in fig. 3, which are a driving waveform, a back emf waveform, and a current waveform flowing through the load after the rotation speed is increased, it can be seen that the

current waveforms

306 and 303 flowing through the load have a great change in amplitude and shape as the back emf 305 is increased.

The system basic architecture of the present utility model is shown in fig. 4, wherein 405 and 406 are respectively a current amplitude target value and a back emf interference target value, the former is a system predefined value, and the latter is 0 (i.e., the purpose of PID control is to keep the back emf interference target value 0); 401. 411 is a current amplitude control PID module and a back electromotive force compensation control PID module respectively; 402 is a voltage-driven sine wave generator, the amplitude of which can be adjusted according to the output of the current amplitude control PID module 401; 412 is a back emf correction waveform generator that adjusts the amplitude of the compensation voltage according to the output of the back emf compensation control PID module and adds the compensation waveform to the voltage drive waveform output by the voltage drive sine wave generator 402; the addition result of the voltage driving waveform and the correction waveform output by the back electromotive force correction waveform generator 412 enters the H bridge 404 after PWM modulation; the current feedback signal of the H-bridge 404 is sampled by the sampling feedback module 403, and then the values of the current amplitude signal and the counter electromotive force interference current signal are respectively sent to the current amplitude control PID module 401 and the counter electromotive force compensation control PID module 411 for feedback control.

403 in fig. 4 is a sampling feedback module, whose composition is shown in fig. 5: where 501 is the analog-to-digital converter, 502 is the sampling point selection part, 503 is the subsequent digital control part. The module samples the H-bridge phase current according to the waveform of the driving voltage 520, and the sampling points are two types: 510. 511 are respectively used by the two control loops in fig. 4, the phase current peak control loop uses 510 the current at the peak time of the driving voltage 520 waveform, and the back emf compensation control loop samples 530 phase current at the zero crossing time 511 of the driving voltage 520 waveform, which varies from positive to negative.

A digital control module provides a current amplitude target value and a back electromotive force interference target value, a current amplitude control PID module receives the current amplitude target value and a feedback value and outputs a current signal to a voltage driving sine wave generator, a back electromotive force compensation control PID module receives the back electromotive force interference target value and the feedback value, the voltage driving sine wave generator and the back electromotive force compensation control PID module output to a back electromotive force correction waveform generator to be added and PWM modulated, a modulated signal enters an H bridge, a current feedback signal of the H bridge is sampled through a sampling feedback module, and then the values of the current amplitude signal and the back electromotive force interference current signal are respectively sent to the current amplitude control PID module and the back electromotive force compensation control PID module to be feedback controlled, and a control formula is as follows:

wherein I is _peak The current target peak value of the H bridge phase is represented by x, the actual value of the phase current measured by the sampling feedback module is represented by V _Compensation Is the value of PID (z) in the formula (2); i _Compensation The back electromotive force is compensated, and the target value of the phase current is 0; z is the actual value of the phase current measured by the sampling feedback module, V _{Driving of} PWM [ V ] is the PID (x) value in formula (1)]Is a pulse width modulation and H-bridge transfer function.

The high-precision pulse width modulation coding system utilizes a simple feedback system to define high-precision sine wave pulse width modulation codes from pulse width modulation voltage, thereby achieving the purpose of precisely controlling the stepping motor. Meanwhile, the coding system only consists of a driving period and a slow attenuation period, so that the fluctuation of a current waveform is faster and the mixed attenuation is lower, and the running performance of the stepping motor with smaller noise and smoother running can be obtained. In H-bridge driving, in many applications, such as: how to obtain the running performance of a stepping motor with smaller noise and smoother running of a 3D printer, a numerical control machine tool and the like becomes a key performance in the applications.

Claims

1. The high-precision pulse width modulation coding system applied to the stepping motor comprises an H bridge, wherein the H bridge comprises four MOS tubes and a load motor, and is characterized by further comprising a digital control module, wherein a control signal end of the digital control module is connected with the four MOS tubes, the load motor is connected with a counter electromotive force equivalent power supply, two MOS tubes of a lower bridge arm of the H bridge are respectively connected with an input end of a tail current induction resistor and an analog-to-digital converter, an output end of the analog-to-digital converter is connected with the digital control module, the digital control module comprises a current amplitude control PID module and a counter electromotive force compensation control PID module, an output end of the current amplitude control PID module is connected with an input end of a voltage driving sine wave generator, an output end of the voltage driving sine wave generator and an output end of the counter electromotive force compensation control PID module are both connected with two input ends of a correction waveform generator, an output end of the correction waveform generator is connected with an input end of the H bridge, an output end of the H bridge is connected with an input end of a sampling feedback module containing the counter electromotive force of the analog-to-digital converter, an output end of the counter electromotive force feedback module is connected with a target value of the counter electromotive force amplitude control PID module, and an output end of the counter electromotive force amplitude control PID module is connected with another output end of the counter electromotive force amplitude control PID module.

2. The high-precision pulse width modulation encoding system for a stepper motor of claim 1, wherein the sampling feedback module further comprises a sampling point selection module and a subsequent digital control module.

3. A high precision pulse width modulation encoding system for a stepper motor as defined in claim 1, wherein said load motor and said H-bridge are one or more.