阅读说明：本技术 一种步进电机传动系统及其控制方法 (Stepping motor transmission system and control method thereof ) 是由 苏文德 朱凯 林红章 虞谦 王宇 刘若晨 冀雯宇 于 2021-08-26 设计创作，主要内容包括：本发明公开了一种步进电机传动系统及其控制方法,包括步进电机、传动机构驱、滚珠丝杠和刀架；步进电机的动力输出轴通过传动机构驱与滚珠丝杠动力连接,在滚珠丝杠上固定装有刀架,通过滚珠丝杠控制刀架的进给,实现更高的同轴度和传动精度。针对上述步进电机传动系统,针对步进电机的控制以位置环为外环,以速度环为内环,实现位置环和速度环相融合,同时能够实现位置的精确调节与实现速度的自动控制。(The invention discloses a stepping motor transmission system and a control method thereof, wherein the stepping motor transmission system comprises a stepping motor, a transmission mechanism driver, a ball screw and a tool rest; the power output shaft of the stepping motor is in power connection with the ball screw through the transmission mechanism, the ball screw is fixedly provided with the tool rest, and the feeding of the tool rest is controlled through the ball screw, so that higher coaxiality and transmission precision are realized. Aiming at the stepping motor transmission system, the position ring is used as an outer ring and the speed ring is used as an inner ring for controlling the stepping motor, so that the position ring and the speed ring are fused, and meanwhile, the accurate adjustment of the position and the automatic control of the speed can be realized.)

1. A control method of a stepping motor transmission system is characterized in that a target position is input to a position PID controller as an expected value, then an actual rotating shaft position of an encoder is input to the position PID controller as an actual value, and a position deviation is obtained by subtracting the expected value from the actual value. Inputting the position deviation into a speed PID controller to be used as a target speed which is an expected value of the speed PID controller; then, the rotating shaft speed of the encoder is input to the speed PID controller to be used as an actual value of the speed PID controller, and a speed deviation is obtained through the difference between the target speed and the actual value; inputting the speed deviation into a speed PID controller, and outputting the calculation result of the speed PID controller to a stepping motor (1); the control of the stepping motor (1) is realized.

2. The control method according to claim 1, wherein the position ring and the speed ring are fused by using the position ring as an outer ring and the speed ring as an inner ring for the control of the stepping motor.

3. The control method of claim 1, wherein the position PID controller employs an anti-integral saturation PID controller.

4. The control method of claim 3, wherein the method of constructing the anti-integral saturation PID controller is:

s1, obtaining the position deviation e of the target position S (t) and the actual rotating shaft position C (t)_s(t) according to the positional deviation e_s(t) calculating the control quantity u of the position PID controller_st，Wherein e is_s(t)＝S(t)-C(t)，K_p、T_IAnd T_DRespectively is a proportional control coefficient, an integral control coefficient and a differential control coefficient;

s2, determining and calculating the differential control quantity u at the current time t_s(t) whether the limit is exceeded;

s3, if not exceeding the limit range, the control quantity u at the current moment is adjusted_s(t) as a control quantity of the system; if u_s(t) is equal to or greater than the clipping value u of the system_smaxOnly accumulating the negative deviation, and removing the integral action from the true deviation; if u_s(t) is less than or equal to the clipping value u of the system_sminOnly the positive deviations are accumulated and the negative deviations are removed from the integration.

5. The control method of claim 1, wherein the speed PID controller employs an integral split PID controller.

6. The control method of claim 5, wherein the method of constructing an integral separation PID controller is:

s1, treating u_s(t) as a desired value for a speed PID controller; the actual spindle position C (t) is used as the actual value of the velocity PID controller, and is represented by u_s(t) and C (t) obtaining a speed deviation e_v(t)；

S2, setting integral separation threshold e_vDeviation of speed e_vAbsolute value of (t) andintegral separation threshold e_vComparing, and judging whether an integration part is needed or not;

s3, if e_v(t) has an absolute value equal to or greater than integral separation threshold e_vRemoving an integral link, and performing a proportion link and a differentiation link of the PID; if e_v(t) has an absolute value equal to or less than integral separation threshold e_vAnd reserving an integral link, and performing a proportion link, an integral link and a differential link of the PID.

7. A stepping motor transmission system based on the control method of claim 4 or 6, which is characterized by comprising a stepping motor (1), a transmission mechanism drive (2), a ball screw (3) and a tool rest (4); the power output shaft of the stepping motor (1) is in power connection with the ball screw (3) through the transmission mechanism drive (2), the ball screw (3) is fixedly provided with the tool rest (4), and the feeding of the tool rest (4) is controlled through the ball screw, so that higher coaxiality and transmission precision are realized.

8. A stepper motor drive system according to claim 7, wherein the transmission drive (2) is a gear drive.

9. A stepping motor transmission system according to claim 8, wherein the driving wheel is sleeved on the power output shaft of the stepping motor (1), the driven wheel is sleeved on the ball screw (3), and the driving wheel is meshed with the driven wheel to realize the transmission of the power of the stepping motor (1) to the ball screw (3).

10. A stepper motor drive system as claimed in claim 7, 8 or 9, wherein the encoder of the stepper motor 1 is mounted at the output of the spindle of the machine tool.

Technical Field

The invention belongs to the technical field of motors and control thereof, and particularly relates to a stepping motor transmission system and a control method thereof.

Background

Technological advances are changing the cost performance between stepper motors and servo motors to meet various demanding industrial automation applications. By using closed loop technology, less expensive stepper motors are entering some areas where only more expensive servo motors are considered suitable.

For open loop stepper motors, the requirement for high instantaneous torque is difficult to achieve due to the risk of losing steps. Closed-loop stepper motors can achieve fast acceleration, can operate silently, have fewer resonances than traditional stepper motors, and can operate at higher bandwidths.

In CNC machines, the cost of the servo motors is a major contributor to the overall cost of each machine. The extra number of cables required for a unitary servo encoder mounted within the cabinet extends installation time and makes maintenance more complicated. If the CNC machine tool is improved, a servo motor is not used, a closed-loop stepping motor is adopted instead, and the motion controller and the communication protocol are still unchanged. Since the stepper motor is integrated with the electronic system, fewer cables are required and maintenance work is therefore simpler. Closed-loop stepper motors can achieve fast acceleration, can operate silently, have fewer resonances than traditional stepper motors, and can operate at higher bandwidths. The electronic system of the stepping motor is integrated with the motor, so that the cable connection can be reduced, and the implementation process is simplified.

In the single loop closed loop control method of the stepping motor, although the single loop control has been good for improving the performance of the stepping motor, the single loop control still has its limitations. The rotating speed of the stepping motor is accurately controlled by using a speed ring, but the stopping position is difficult to accurately control; the use of a position ring to precisely control the angle through which the stepper motor rotates has to be manually speed limited to prevent stalling.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention provides a stepping motor transmission system and a control method thereof, which can realize accurate adjustment of a position and automatic control of speed.

The technical scheme adopted by the invention is as follows:

a control method of a stepping motor transmission system comprises the steps of inputting a target position as an expected value to a position PID controller, then inputting the actual rotating shaft position of an encoder as an actual value to the position PID controller, and obtaining a position deviation through the difference of the expected value and the actual value. Inputting the position deviation into a speed PID controller to be used as a target speed which is an expected value of the speed PID controller; then, the rotating shaft speed of the encoder is input to the speed PID controller to be used as an actual value of the speed PID controller, and a speed deviation is obtained through the difference between the target speed and the actual value; inputting the speed deviation into a speed PID controller, and outputting a calculation result of the speed PID controller to the stepping motor; and the control of the stepping motor is realized.

Further, aiming at the control of the stepping motor, the position ring is used as an outer ring, the speed ring is used as an inner ring, and the fusion of the position ring and the speed ring is realized.

Further, the position PID controller adopts an anti-integral saturation PID controller.

Further, the method for constructing the anti-integral saturation PID controller comprises the following steps:

s1, obtaining the position deviation e of the target position S (t) and the actual rotating shaft position C (t)_s(t) according to the positional deviation e_s(t) calculating the control quantity u of the position PID controller_s(t)，Wherein e is_s(t)＝S(t)-C(t)，K_p、T_IAnd T_DRespectively is a proportional control coefficient, an integral control coefficient and a differential control coefficient;

s2, determining and calculating the differential control quantity u at the current time t_s(t) whether the limit is exceeded;

s3, if not exceeding the limit range, the control quantity u at the current moment is adjusted_s(t) as a control quantity of the system; if u_s(t) is equal to or greater than the clipping value u of the system_smaxOnly accumulating the negative deviation, and removing the integral action from the true deviation; if u_s(t) is less than or equal to the clipping value u of the system_sminOnly the positive deviations are accumulated and the negative deviations are removed from the integration.

Further, the speed PID controller adopts an integral separation PID controller.

Further, the method for constructing the integral separation PID controller comprises the following steps:

s1, treating u_s(t) as a desired value for a speed PID controller; the actual spindle position C (t) is used as the actual value of the velocity PID controller, and is represented by u_s(t) and C (t) obtaining a speed deviation e_v(t)；

S2, setting integral separation threshold e_vDeviation of speed e_vAbsolute value of (t) and integral separation threshold e_vComparing, and judging whether an integration part is needed or not;

s3, if e_v(t) has an absolute value equal to or greater than integral separation threshold e_vRemoving an integral link, and performing a proportion link and a differentiation link of the PID; if e_v(t) has an absolute value equal to or less than integral separation threshold e_vAnd reserving an integral link, and performing a proportion link, an integral link and a differential link of the PID.

A stepping motor transmission system comprises a stepping motor, a transmission mechanism drive, a ball screw and a tool rest; the power output shaft of the stepping motor is in power connection with the ball screw through the transmission mechanism, the ball screw is fixedly provided with the tool rest, and the feeding of the tool rest is controlled through the ball screw, so that higher coaxiality and transmission precision are realized.

Further, the transmission mechanism adopts gear transmission.

Furthermore, the driving wheel is sleeved on a power output shaft of the stepping motor, the driven wheel is sleeved on the ball screw, and the driving wheel is meshed with the driven wheel to realize that the power of the stepping motor is transmitted to the ball screw.

Furthermore, an encoder of the stepping motor is arranged at the output end of the main shaft of the machine tool,

the invention has the beneficial effects that:

aiming at the control of the stepping motor, the position loop is controlled by the anti-integral saturation PID controller, so that the saturation of integral control quantity can be effectively inhibited, and the overshoot of output feedback is reduced; in addition, the integral separation PID controller is adopted to control the speed loop, so that large overshoot caused by transition integral can be avoided, and the static error of the system is eliminated. The invention integrates the position ring and the speed ring control together, and the advantages of the position ring and the speed ring are respectively taken, thereby realizing the accurate adjustment of the position and the automatic control of the speed.

The technical scheme of the stepping motor transmission system designed by the invention is easy to improve on a numerical control machine tool, is easy to produce and operate, can perform fine machining on complex elements, saves a large amount of purchase cost for enterprises, and is low in cost.

Drawings

FIG. 1 is a schematic structural view of a stepper motor drive system of the present invention;

FIG. 2 is a schematic view of a control system for the stepper motor of the present invention;

in the figure, 1, a stepping motor, 2, a transmission mechanism drive, 3, a ball screw, 4 and a tool rest.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

A stepping motor transmission system as shown in fig. 1 comprises a stepping motor 1, a transmission mechanism drive 2, a ball screw 3 and a tool rest 4; step motor 1's power take off shaft drives 2 through drive mechanism and is connected with ball 3 power, specifically, drive mechanism in this application drives 2 and adopts gear drive, and the action wheel suit is on step motor 1's power take off shaft, and from the driving wheel suit on ball 3, on the action wheel realized step motor 1's power transmission to ball 3 with following the meshing. The ball screw 3 is fixedly provided with the tool rest 4, and the feeding of the tool rest 4 is controlled through the ball screw, so that higher coaxiality and transmission precision can be realized. The limit distance of the movement of the tool rest 4 is controlled by a limit switch when the tool rest moves.

The encoder of the stepping motor 1 is arranged at the output end of the main shaft of the machine tool, the program definition is carried out according to the transmission ratio relation between the output end and the main shaft, and the encoder outputs corresponding pulse signals every time the main shaft rotates one circle, and the pulse signals are processed by the main control chip and then transmitted to the stepping motor 1 to be correspondingly controlled. The technical scheme is easy to improve the numerical control machine tool, easy to produce and operate, capable of carrying out fine machining on complex elements, saving a large amount of purchase cost for enterprises and low in cost.

Based on the stepping motor transmission system provided by the application, the application also provides a control method of the stepping motor transmission system, as shown in fig. 2. A control method of fusing a position ring and a speed ring is adopted, the position ring is used as an outer ring, and the speed ring is used as an inner ring.

Firstly, inputting a target position as an expected value to a position PID controller, then inputting the actual rotating shaft position of an encoder as an actual value to the position PID controller, and obtaining a position deviation through the difference between the expected value and the actual value. Inputting the position deviation into a speed PID controller to be used as a target speed which is an expected value of the speed PID controller; then, the rotating shaft speed of the encoder is input to the speed PID controller to be used as an actual value of the speed PID controller, and a speed deviation is obtained through the difference between the target speed and the actual value; inputting the speed deviation into a speed PID controller, and outputting a calculation result of the speed PID controller to the stepping motor 1; the control of the stepping motor 1 is realized, and the accurate adjustment of the position and the automatic control of the speed can be realized.

In this embodiment, the position PID controller adopts an anti-integral saturation PID controller, which can avoid the problem of PID integral saturation, and the method for constructing the anti-integral saturation PID controller is as follows:

s1, the target position S (t), the actual positionPosition deviation e obtained from the position of the rotating shaft C (t)_s(t) according to the positional deviation e_s(t) calculating the control quantity u of the position PID controller_s(t)，Wherein e is_s(t)＝S(t)-C(t)，K_p、T_IAnd T_DRespectively a proportional control coefficient, an integral control coefficient and a differential control coefficient.

S2, determining and calculating the differential control quantity u at the current time t_s(t) is out of limit.

S3, if not exceeding the limit range, the control quantity u at the current moment is adjusted_s(t) as a control quantity of the system; if u_s(t) is equal to or greater than the clipping value u of the system_smaxOnly accumulating the negative deviation, and removing the integral action from the true deviation; if u_s(t) is less than or equal to the clipping value u of the system_sminOnly the positive deviations are accumulated and the negative deviations are removed from the integration. The anti-integral saturation PID controller can effectively inhibit the saturation of integral control quantity and reduce the overshoot of output feedback.

The speed PID controller adopts an integral separation PID controller, and the method for constructing the integral separation PID controller comprises the following steps:

s1, treating u_s(t) as a desired value for a speed PID controller; the actual spindle position C (t) is used as the actual value of the velocity PID controller, and is represented by u_s(t) and C (t) obtaining a speed deviation e_v(t)；

S2, setting integral separation threshold e_vDeviation of speed e_vAbsolute value of (t) and integral separation threshold e_vComparing, and judging whether an integration part is needed or not;

s3, if e_v(t) has an absolute value equal to or greater than integral separation threshold e_vRemoving an integral link, and performing a proportion link and a differentiation link of the PID; if e_v(t) has an absolute value equal to or less than integral separation threshold e_vAn integral link is reserved, and a proportion link, an integral link and a differential link of PID are carried out; PID changes the effect of the integral part according to the error, and can avoid the transient integral from causing comparisonLarge overshoot, and thus, the static error of the system.

According to the control method of the stepping motor transmission system, the position loop is controlled through the anti-integral saturation PID controller, so that the saturation of integral control quantity can be effectively inhibited, and the overshoot of output feedback is reduced; in addition, the integral separation PID controller is adopted to control the speed loop, so that large overshoot caused by transition integral can be avoided, and the static error of the system is eliminated. The position loop control and the speed loop control are coupled, so that the accurate adjustment of the position and the automatic control of the speed are realized.

The above embodiments are only used for illustrating the design idea and features of the present invention, and the purpose of the present invention is to enable those skilled in the art to understand the content of the present invention and implement the present invention accordingly, and the protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes and modifications made in accordance with the principles and concepts disclosed herein are intended to be included within the scope of the present invention.