Stepping motor control system and control method for reducing torque ripple

Abstract

The invention belongs to the technical field of stepping motor control, and particularly provides a stepping motor control system and control method for reducing torque ripples, and the control method comprises the steps: building a disturbance observer comprising a low-pass filter to estimate a cogging torque and other external disturbance torques in the operation of a motor; meanwhile, a dynamic cogging torque compensator comprising a high-pass filter is constructed to compensate for dynamic cogging torque generated in a high-frequency period, a speed controller is constructed, and the interference observer and the cogging torque compensator are combined to calculate compensation current to adjust the speed of the motor. Therefore, the torque ripple of the two-phase hybrid stepping motor can be effectively reduced through accurate control, the stability and efficiency of motor operation are improved, and the control precision of the stepping motor is further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of stepper motor control, and specifically designs a stepper motor control system and a control method for reducing torque fluctuation. Background Art

[0002] The two-phase hybrid stepper motor is a commonly used type of stepper motor that combines the advantages of permanent magnet and reactive stepper motors. This motor has two phase windings, and by controlling the flow of current in these windings, the rotation angle and speed of the motor can be accurately controlled. Due to its high control accuracy, it is widely used in industrial automation, precision instruments, office automation equipment and other fields.

[0003] Since the rotor of a two-phase hybrid stepper motor has multiple tooth slot structures, when the rotor is running, the change in the magnetic field will cause the rotor to jump between the tooth slots, generating a periodic torque fluctuation, namely the tooth slot torque. The tooth slot torque may cause the stepper motor to vibrate and become unstable during operation, affecting the positioning accuracy.

[0004] In the prior art, cogging torque can be effectively reduced by micro-stepping drive, but micro-stepping drive is relatively complex to implement and requires high control algorithms. In addition, micro-stepping drive usually leads to an increase in drive current, thereby increasing heat and energy consumption. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the defects in the prior art that the cogging torque of the two-phase hybrid stepper motor affects the positioning accuracy and the control method is relatively complicated, thereby providing a stepper motor control system and control method for reducing torque fluctuations.

[0006] A stepper motor control method for reducing torque fluctuations, the control method comprising the following steps: Step S1: Establishing a mathematical model of the stepper motor, including a voltage equation, a magnetic flux equation and a mechanical dynamics equation; Step S2: constructing a disturbance observer for estimating the cogging torque and other external disturbance torques of the stepper motor, which are defined as equivalent disturbance torques, wherein the disturbance observer includes a low-pass filter; Step S3: constructing a dynamic cogging torque compensator for compensating the cogging torque generated by the high-frequency period of the stepping motor, wherein the dynamic cogging torque compensator comprises a filter; Step S4: constructing a speed controller, wherein the speed controller is used to calculate a compensation current to adjust the speed of the stepper motor based on the outputs of the disturbance observer and the dynamic cogging torque compensator.

[0007] Furthermore, in step S1, the voltage equation of the stepper motor is: ; The magnetic flux equation is: ; The mechanical dynamics equation is: ; Wherein, ud and uq are the d-axis and q-axis voltages of the stepper motor, respectively; Rd and Rq are the d-axis and q-axis resistances of the stepper motor, respectively; id and iq are the d-axis and q-axis currents of the stepper motor, respectively; Ld and Lq are the d-axis and q-axis inductances of the stepper motor, respectively; t is the time; φd and φq are the magnetic fluxes of the d-axis and q-axis of the stepper motor, respectively; θ is the position angle; Represents the electromagnetic torque output by the stepper motor, is the load torque, is the cogging torque, φmax is the maximum flux value of the motor winding, ω is the motor angular velocity, P is the number of motor pole pairs, J is the total moment of inertia of the stepper motor and load, and B is the viscous friction coefficient.

[0008] Furthermore, in step S2, the transfer function of the disturbance observer is Designed with specific poles A low pass filter.

[0009] Furthermore, in step S2, the equivalent interference torque is: ; The transfer function of the disturbance observer is: ; in, is the torque constant, represents the desired q-axis current, represents the angular velocity of the stepper motor rotor, are the poles of the disturbance observer, is the inertia torque, and s is the transfer function.

[0010] Further, in step S3, the dynamic cogging torque is: ; in, is the cogging torque predicted by the mathematical model.

[0011] Furthermore, in step S4, the speed controller calculates the compensation current Determined by combining the estimate of the disturbance observer and the output of the dynamic cogging torque compensator.

[0012] Furthermore, in step S4, the compensation current is: ; in, is the torque constant of the stepper motor.

[0013] A stepper motor control system for reducing torque fluctuations, which completes the control of the stepper motor through the above control method, including a proportional coefficient controller, a proportional gain, a first proportional integral controller, a second proportional integral controller, a third proportional integral controller, a disturbance observer, a dynamic cogging torque compensator, a speed controller, an inverse Park converter, a controller, and a Park converter; The Park converter obtains the feedback current and feedback angle of the stepper motor, and outputs a d-axis feedback current and a q-axis feedback current; The disturbance observer obtains the feedback speed of the stepper motor and outputs an equivalent disturbance torque; The dynamic cogging torque compensator obtains the feedback angle of the stepper motor and outputs the dynamic cogging torque; The speed controller obtains the equivalent interference torque and the dynamic cogging torque, and outputs a compensation current; The first adding point subtracts the feedback position from the given position and outputs the result to the proportional coefficient controller; The proportional gain obtains a given speed, and the second addition point adds the output of the proportional coefficient controller and the proportional gain, subtracts the feedback speed of the stepper motor, and outputs to the first proportional-integral controller; A third adding point adds the first proportional-integral controller and the compensation current; The fourth adding point subtracts the q-axis feedback current from the output of the third adding point, and outputs the result to the third proportional-integral controller, and the third proportional-integral controller outputs the q-axis current loop control amount; The fifth adding point subtracts the d-axis feedback current from the d-axis given current and outputs the result to the second proportional-integral controller, and the second proportional-integral controller outputs the d-axis current loop control amount; The inverse Park converter obtains the q-axis current loop control quantity and the d-axis current loop control quantity, and outputs the A-phase control voltage and the B-phase control voltage to the PWM controller; The PWM controller controls the stepper motor.

[0014] Furthermore, the stepper motor controlled by the control system is a two-phase hybrid stepper motor.

[0015] Beneficial effect: The present invention provides a stepper motor control system and a control method for reducing torque fluctuations. The control method estimates the cogging torque and other external interference torques in the operation of the motor by constructing an interference observer including a low-pass filter, and at the same time constructs a dynamic cogging torque compensator including a high-pass filter to compensate for the dynamic cogging torque generated by a high-frequency period, and constructs a speed controller, which combines the interference observer and the cogging torque compensator to calculate the compensation current to adjust the motor speed, thereby effectively reducing the torque pulsation of the two-phase hybrid stepper motor through precise control, improving the stability and efficiency of the motor operation, and further improving the control accuracy of the stepper motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a schematic block diagram of the method flow of the present invention; Figure 2 It is a schematic diagram of the system structure of the present invention. DETAILED DESCRIPTION

[0018] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0019] In the description of the present application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood 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 of the features. In the description of the present application, "plurality" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0020] Embodiment 1: Reference Figure 1 As shown, this embodiment provides a stepper motor control method for reducing torque fluctuation, and the control method includes the following steps: Step S1: Establishing a mathematical model of the stepper motor, including a voltage equation, a magnetic flux equation and a mechanical dynamics equation; Specifically, the voltage equation of the stepper motor is: ; The magnetic flux equation is: ; The mechanical dynamics equation is: ; Wherein, ud and uq are the d-axis and q-axis voltages of the stepper motor, respectively; Rd and Rq are the d-axis and q-axis resistances of the stepper motor, respectively; id and iq are the d-axis and q-axis currents of the stepper motor, respectively; Ld and Lq are the d-axis and q-axis inductances of the stepper motor, respectively; t is the time; φd and φq are the magnetic fluxes of the d-axis and q-axis of the stepper motor, respectively; θ is the position angle; Represents the electromagnetic torque output by the stepper motor, is the load torque, is the cogging torque, φmax is the maximum flux value of the motor winding, ω is the motor angular velocity, P is the number of motor pole pairs, J is the total moment of inertia of the stepper motor and load, and B is the viscous friction coefficient.

[0021] Step S2: constructing a disturbance observer for estimating the cogging torque and other external disturbance torques of the stepper motor, which are defined as equivalent disturbance torques, wherein the disturbance observer includes a low-pass filter; The transfer function of the disturbance observer Designed with specific poles A low pass filter.

[0022] Specifically, the equivalent interference torque is: ; The transfer function of the disturbance observer is: ; in, is the torque constant, represents the desired q-axis current, represents the angular velocity of the stepper motor rotor, are the poles of the disturbance observer, is the inertia torque, and s is the transfer function.

[0023] Step S3: constructing a dynamic cogging torque compensator for compensating the cogging torque generated by the high-frequency period of the stepping motor, wherein the dynamic cogging torque compensator comprises a filter; The cut-off frequency of the high-pass filter of the dynamic cogging torque compensator is the same as the pole of the disturbance observer. Match.

[0024] Specifically, the dynamic cogging torque is: ; in, is the cogging torque predicted by the mathematical model.

[0025] Step S4: constructing a speed controller, wherein the speed controller is used to calculate a compensation current to adjust the speed of the stepper motor based on the outputs of the disturbance observer and the dynamic cogging torque compensator.

[0026] The speed controller calculates the compensation current Determined by combining the estimate of the disturbance observer and the output of the dynamic cogging torque compensator.

[0027] Specifically, the compensation current is: ; in, is the torque constant of the stepper motor.

[0028] Embodiment 2: Reference Figure 2 As shown, this embodiment provides a stepper motor control system for reducing torque fluctuations, characterized in that the control of the stepper motor is completed by the control method described in Example 1, including a proportional coefficient controller, a proportional gain, a first proportional integral controller, a second proportional integral controller, a third proportional integral controller, a disturbance observer, a dynamic cogging torque compensator, a speed controller, an inverse Park converter, a controller, and a Park converter; The Park converter obtains the feedback current and feedback angle of the stepper motor, and outputs a d-axis feedback current and a q-axis feedback current; The disturbance observer obtains the feedback speed of the stepper motor and outputs an equivalent disturbance torque; The dynamic cogging torque compensator obtains the feedback angle of the stepper motor and outputs the dynamic cogging torque; The speed controller obtains the equivalent interference torque and the dynamic cogging torque, and outputs a compensation current; The first adding point subtracts the feedback position from the given position and outputs the result to the proportional coefficient controller; The proportional gain obtains a given speed, and the second addition point adds the output of the proportional coefficient controller and the proportional gain, subtracts the feedback speed of the stepper motor, and outputs to the first proportional-integral controller; A third adding point adds the first proportional-integral controller and the compensation current; The fourth adding point subtracts the q-axis feedback current from the output of the third adding point, and outputs the result to the third proportional-integral controller, and the third proportional-integral controller outputs the q-axis current loop control amount; The fifth adding point subtracts the d-axis feedback current from the d-axis given current and outputs the result to the second proportional-integral controller, and the second proportional-integral controller outputs the d-axis current loop control amount; The inverse Park converter obtains the q-axis current loop control quantity Uq_Ctr and the d-axis current loop control quantity Ud_Ctr, and outputs the A-phase control voltage Ua and the B-phase control voltage Ub to the PWM controller; The PWM controller controls the stepper motor.

[0029] The present embodiment discloses a stepper motor control system for reducing torque fluctuation, including a first loop and a second loop.

[0030] In the first loop: Pos_ref is the given position command, Pos_fdk is the feedback position value, these two values ​​are used to control the position loop after passing through the deviation proportional controller P, and the position loop control value is output; In the second loop: Spd_ref is the given speed command, Spd_fdk is the feedback speed value, these two values ​​and the position loop control value of the first loop are output as the speed loop control value after passing through the proportional integral controller PI; Tdis is the cogging torque and other external interference torques, Tcmkpf is the cogging torque compensation value, and these two values ​​are accumulated with the speed loop control amount of the second loop to output the q-axis current control command.

[0031] Iq_fdk, Id_fdk and Id_ref are the current feedback and given values ​​of the d-axis and q-axis respectively, which perform PI control of the current loop and then generate PWM through coordinate transformation to control the rotation of the motor.

[0032] In this embodiment, the stepper motor controlled by the control system is a two-phase hybrid stepper motor.

[0033] This embodiment discloses that the torque pulsation of the two-phase hybrid stepping motor is significantly reduced and the control accuracy and operation stability of the motor are improved through precise mathematical modeling and advanced control strategies.

[0034] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0035] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A stepper motor control method for reducing torque fluctuation, characterized in that: The control method comprises the following steps: Step S1: Establishing a mathematical model of the stepper motor, including a voltage equation, a magnetic flux equation and a mechanical dynamics equation; Step S2: constructing a disturbance observer for estimating the cogging torque and other external disturbance torques of the stepper motor, which are defined as equivalent disturbance torques, wherein the disturbance observer includes a low-pass filter; Step S3: constructing a dynamic cogging torque compensator for compensating the cogging torque generated by the high-frequency period of the stepping motor, wherein the dynamic cogging torque compensator includes a filter; Step S4: constructing a speed controller, wherein the speed controller is used to calculate a compensation current to adjust the speed of the stepper motor based on the outputs of the disturbance observer and the dynamic cogging torque compensator.

2. A stepper motor control method for reducing torque fluctuation according to claim 1, characterized in that: In step S1, the voltage equation of the stepper motor is: ； The magnetic flux equation is: ； The mechanical dynamics equation is: ； Wherein, ud and uq are the d-axis and q-axis voltages of the stepper motor, respectively; Rd and Rq are the d-axis and q-axis resistances of the stepper motor, respectively; id and iq are the d-axis and q-axis currents of the stepper motor, respectively; Ld and Lq are the d-axis and q-axis inductances of the stepper motor, respectively; t is the time; φd and φq are the magnetic fluxes of the d-axis and q-axis of the stepper motor, respectively; θ is the position angle; Represents the electromagnetic torque output by the stepper motor, is the load torque, is the cogging torque, φmax is the maximum flux value of the motor winding, ω is the motor angular velocity, P is the number of motor pole pairs, J is the total moment of inertia of the stepper motor and load, and B is the viscous friction coefficient.

3. The stepper motor control method for reducing torque fluctuation according to claim 1, characterized in that: In step S2, the transfer function of the disturbance observer is Designed with specific poles A low pass filter.

4. A stepper motor control method for reducing torque fluctuation according to claim 3, characterized in that: In step S2, the equivalent interference torque is: ； The transfer function of the disturbance observer is: ； in, is the torque constant, represents the desired q-axis current, represents the angular velocity of the stepper motor rotor, are the poles of the disturbance observer, is the inertia torque, and s is the transfer function.

5. The stepper motor control method for reducing torque fluctuation according to claim 3, characterized in that: In step S3, the cutoff frequency of the high-pass filter of the dynamic cogging torque compensator is equal to the pole of the disturbance observer. Match.

6. A stepper motor control method for reducing torque fluctuation according to claim 5, characterized in that: In step S3, the dynamic cogging torque is: ； in, is the cogging torque predicted by the mathematical model.

7. A stepper motor control method for reducing torque fluctuation according to claim 5, characterized in that: In step S4, the speed controller calculates the compensation current Determined by combining the estimate of the disturbance observer and the output of the dynamic cogging torque compensator.

8. The stepper motor control method for reducing torque fluctuation according to claim 7, characterized in that: In step S4, the compensation current is: ； in, is the torque constant of the stepper motor.

9. A stepper motor control system for reducing torque fluctuations, characterized in that: The control method of any one of claims 1 to 8 is used to control the stepper motor, comprising a proportional coefficient controller, a proportional gain, a first proportional integral controller, a second proportional integral controller, a third proportional integral controller, a disturbance observer, a dynamic cogging torque compensator, a speed controller, an inverse Park converter, a controller, and a Park converter; The Park converter obtains the feedback current and feedback angle of the stepper motor, and outputs a d-axis feedback current and a q-axis feedback current; The disturbance observer obtains the feedback speed of the stepper motor and outputs an equivalent disturbance torque; The dynamic cogging torque compensator obtains the feedback angle of the stepper motor and outputs the dynamic cogging torque; The speed controller obtains the equivalent interference torque and the dynamic cogging torque, and outputs a compensation current; The first adding point subtracts the feedback position from the given position and outputs the result to the proportional coefficient controller; The proportional gain obtains a given speed, and the second addition point adds the output of the proportional coefficient controller and the proportional gain, subtracts the feedback speed of the stepper motor, and outputs to the first proportional-integral controller; A third adding point adds the first proportional-integral controller and the compensation current; The fourth adding point subtracts the q-axis feedback current from the output of the third adding point, and outputs the result to the third proportional-integral controller, and the third proportional-integral controller outputs the q-axis current loop control amount; The fifth adding point subtracts the d-axis feedback current from the d-axis given current and outputs the result to the second proportional-integral controller, and the second proportional-integral controller outputs the d-axis current loop control amount; The inverse Park converter obtains the q-axis current loop control quantity and the d-axis current loop control quantity, and outputs the A-phase control voltage and the B-phase control voltage to the PWM controller; The PWM controller controls the stepper motor.

10. A stepper motor control system for reducing torque fluctuation according to claim 9, characterized in that: The stepper motor controlled by the control system is a two-phase hybrid stepper motor.

Images