阅读说明：本技术 一种伺服压力机滑块位置控制及估算滑块压力的方法 (Method for controlling position of slide block of servo press and estimating pressure of slide block ) 是由 李琦 李海明 袁全 张传锦 王岩 赵璨 邵光存 程慧杰 李岸然 于 2021-12-06 设计创作，主要内容包括：本发明属于伺服压力机技术领域,具体涉及到一种伺服压力机滑块位置控制及估算滑块压力的方法。本发明通过控制算法直接估算伺服压力机的滑块压力,将电机负载转矩估算值的计算加入到伺服电机控制算法中的给定值上,极大程度地改善了伺服压力机系统突然遇到大负载和工件加压时的转矩跟随情况及电机响应速度,使得成形过程中的工艺曲线跟随性能大大提高。(The invention belongs to the technical field of servo presses, and particularly relates to a method for controlling the position of a slide block of a servo press and estimating the pressure of the slide block. The invention directly estimates the slide pressure of the servo press through the control algorithm, and adds the calculation of the motor load torque estimated value to the set value in the servo motor control algorithm, thereby greatly improving the torque following condition and the motor response speed when the servo press system suddenly encounters large load and workpiece pressurization, and greatly improving the process curve following performance in the forming process.)

1. A method for controlling the position of a slide of a servo press comprises the following steps:

step S1: inputting process curve key points on a man-machine interaction interface of the servo press, and transmitting the process curve key points to a whole machine electric control system of the servo press;

step S2: generating a forming process curve which accords with the kinematics of the servo press from the key points of the input process curve according to the constraint conditions of the servo press, wherein the forming process curve comprises given crank angle, given speed and given acceleration;

step S3: step S2, inputting a given crank angle, a given speed and a given acceleration as signals of a dynamic analysis part in the servo driver; the output of the servo driver is a three-phase alternating current output signal; the output hardware of the servo driver is connected to the input of the three-phase motor; the nonlinear dynamics control of the press is realized by adopting a dynamics method for calculating torque and a proportional-derivative control method in a servo driver, so that the calculated output torque is obtained;

step S4: dividing the calculated output torque by the reduction ratio and then adding the estimated motor load torque to obtain the given torque of the motor;

step S5: the motor given torque is used as an input signal of a servo motor control algorithm, the input of the predicted torque control is the motor given torque, the output of the predicted torque control is sent to a voltage type inversion unit, and the voltage type inversion unit outputs three-phase alternating current to control the rotation of the motor;

step S6: a position sensor is arranged at the center of the shaft side of the crank, the position sensor acquires the current position of the crank, a feedback speed signal of the crank is obtained through the differentiation of a position feedback signal of the position sensor, and the feedback speed signal is fed back to a servo motor driver through a communication signal line to participate in control operation.

2. A method of controlling the position of a servo press ram as claimed in claim 1, wherein: in step S2, the forming process curve is implemented by a process curve interpolation algorithm.

3. A method of controlling the position of a servo press ram as claimed in claim 1, wherein: in step S4, the motor load torque is estimated by using a non-linear observer.

4. A method of controlling the position of a servo press ram as claimed in claim 1, wherein: in step S5, the servo motor control algorithm adopts a limited control set predicted torque control algorithm.

5. A method of estimating a ram pressure, based on the method of controlling a ram position of a servo press according to claim 1, characterized by: and step S7, obtaining the current pressure value of the slide block through table lookup according to the mechanical parameters of the transmission mechanism of the servo press, the slide block position and the current motor load torque value.

Technical Field

The invention belongs to the technical field of servo presses, and particularly relates to a method for controlling the position of a slide block of a servo press and estimating the pressure of the slide block.

Background

In the forming process of the press machine, the following error of the motor is increased after the slide block is subjected to the reaction force of the forming of the workpiece, and the forming process of the process curve of the press machine is influenced. The publication No. CN110757882 discloses a full closed-loop control system and method based on a sensorless servo press, a dynamic model, a robust controller and a nonlinear predictive controller are utilized in a system of the servo press, full closed-loop control of the servo press is achieved, a nonlinear control method and a robust controller are adopted, system interference caused by nonlinearity due to the gap of a press transmission system and the deformation of a press body can be effectively reduced, and the motor following error in the forming process of a workpiece cannot be reduced. Application No. 2019110499184, a system and a method for detecting pressure failure of a servo press, describe a pressure detection method of a servo press, not only can actually diagnose the failure, but also can monitor the pressure value in real time, but in the application process of the scheme, at least 2 pressure sensors are required to be added in a hardware system to detect strain gauges, at least 4 pressure sensors are required to detect strain gauges in a medium-large press, each pressure sensor detects the strain gauge and corresponds to a pressure detection transmitting device, and the hardware cost of a control system is increased.

Disclosure of Invention

The invention provides a servo press slide block position control method and a method for estimating slide block pressure, aiming at solving the defects of the prior art.

The method for controlling the position of the slide block of the servo press comprises the following steps:

step S1: inputting process curve key points on a man-machine interaction interface of the servo press, and transmitting the process curve key points to a whole machine electric control system of the servo press;

step S2: generating a forming process curve which accords with the kinematics of the servo press from the key points of the input process curve according to the constraint conditions of the servo press, wherein the forming process curve comprises given crank angle, given speed and given acceleration;

step S3: step S2, inputting a given crank angle, a given speed and a given acceleration as signals of a dynamic analysis part in the servo driver; the output of the servo driver is a three-phase alternating current output signal; the output hardware of the servo driver is connected to the input of the three-phase motor; the nonlinear dynamics control of the press is realized by adopting a dynamics method for calculating torque and a proportional-derivative control method in a servo driver, so that the calculated output torque is obtained;

step S4: dividing the calculated output torque by the reduction ratio and then adding the estimated motor load torque to obtain the given torque of the motor;

step S5: the motor given torque is used as an input signal of a servo motor control algorithm, the input of the predicted torque control is the motor given torque, the output of the predicted torque control is sent to a voltage type inversion unit, and the voltage type inversion unit outputs three-phase alternating current to control the rotation of the motor;

step S6: a position sensor is arranged at the center of the shaft side of the crank, the position sensor acquires the current position of the crank, a feedback speed signal of the crank is obtained through the differentiation of a position feedback signal of the position sensor, and the feedback speed signal is fed back to a servo motor driver through a communication signal line to participate in control operation.

As a preferable scheme:

in step S2, the forming process curve is implemented by a process curve interpolation algorithm.

In step S4, the motor load torque is estimated by using a non-linear observer.

In step S5, the servo motor control algorithm adopts a limited control set predicted torque control algorithm.

The invention also comprises a method for estimating the pressure of the slide block, on the basis of the steps S1-S6, the method also comprises a step S7, and the step S7 obtains the current pressure value of the slide block through table lookup according to the mechanical parameters of the transmission mechanism of the servo press, the position of the slide block and the current motor load torque value.

The invention mainly solves the technical problem that the following error of a motor in the process of realizing a process curve is increased after a slide block is subjected to the reaction force of workpiece forming in the forming process of a servo press. The method provided by the invention can greatly reduce the following error of the motor in the forming process and improve the forming quality of the workpiece.

The method can also obtain the pressure of the servo press machine by directly deducing, calculating and looking up the table through the motor torque estimated value of the servo driver on the basis of not using a pressure strain gauge, directly saves a hardware sensor and a transmitting unit of the part and saves the hardware cost.

Under the hardware environment of the control system of the conventional servo press, the method can be realized by only changing the control method without increasing other hardware cost, and the process curve following performance in the forming process is greatly improved.

The invention directly estimates the slide pressure of the servo press through a control algorithm, can greatly reduce the hardware cost of the system and improve the reliability and the stability of the system.

The invention adds the calculation of the motor load torque estimated value to the set value in the servo motor control algorithm, greatly improves the torque following condition and the motor response speed when a servo press system suddenly meets a large load and a workpiece is pressurized, and enables the motor to feed back the crank angle, speed and acceleration set values following the process curve as far as possible.

Detailed Description

The following embodiments of the present invention are provided, and it should be noted that the present invention is not limited to the following embodiments, and all equivalent changes based on the technical solutions of the present invention are within the protection scope of the present invention.

The technical scheme of the invention is as follows:

step S1: and inputting process curve key points on a man-machine interaction interface of the servo press, and then transmitting the input process curve key points to a complete machine electric control system of the servo press.

Step S2: and generating a forming process curve which accords with the kinematics of the servo press by using the process curve key points input by the human-computer interaction interface according to the constraint conditions of the servo press, wherein the forming process curve comprises crank angle giving, speed giving and acceleration giving.

Preferably, the forming process curve is realized in a complete machine electric control system of the servo press through a process curve interpolation algorithm.

Step S3: the crank angle setting, the velocity setting and the acceleration setting can be used as signals input into a dynamic analysis part in the servo driver. The output of the servo driver is a three-phase alternating current output signal; the output hardware of the servo driver is connected to the input of the three-phase motor; the non-linear dynamic control of the press is realized by adopting a dynamic method for calculating torque and a PD (proportional differential) control method in a servo driver, and the calculated output torque is obtained.

The lagrangian expression of kinetics is:

wherein the content of the first and second substances,，in order to ensure the kinetic energy of the transmission part of the servo press,the potential energy of a transmission part of the servo press is equal to that of the transmission part of the servo press;the angle of a crankshaft of the servo press or a selected key angle;is the calculated output torque.

Step S4: and dividing the calculated output torque by the reduction ratio and adding the estimated motor load torque to obtain the motor given torque.

The preferred method of estimating the motor load torque of the present embodiment uses a non-linear observer. The motor load torque model of the servo press can be expressed as:

wherein the content of the first and second substances,andis a variable coefficient of the servo press, and the coefficient is related to the rotational inertia, the mass and the length of a transmission mechanism rod of the servo press;is a crank angle;is the speed of the crank;is the acceleration of the crank;is the electromagnetic torque of the motor;the ideal motor load torque.

The load torque may have many meanings, including friction torque, motor load force torque, balance cylinder force torque, and other dynamic torques contained in non-models. Wherein, the motor load torque accounts for the main component.

Designing a nonlinear observer as follows:

wherein the content of the first and second substances,obtaining an estimated value of the load torque of the motor for the variable parameters of the nonlinear observer through a series of mathematical transformations and the calculation of auxiliary variables;for the actual estimated value of the motor load torque, theoreticallyAndare almost equal.

Benefits and advantages: because the calculation of the motor load torque estimated value can be added to the set value in the servo motor control algorithm, the torque following condition and the motor response speed when a servo press system suddenly encounters a large load and a workpiece is pressurized are improved to a great extent, and the motor can feed back the crank angle, speed and acceleration set values following a process curve as far as possible.

Step S5: the motor set torque is used as an input signal of a servo motor control algorithm. Preferably, the servo motor control algorithm employs a limited control set predictive torque control algorithm. The input of the predicted torque control is the given torque of the motor, the output of the predicted torque control is sent to a VSI (voltage source inverter unit), and the voltage source inverter unit outputs three-phase alternating current to control the rotation of the motor.

Step S6: the position sensor is arranged at the center of the shaft side of the crank, the current position of the crank can be acquired, the feedback speed signal of the crank can be acquired through the differentiation of the position feedback signal of the position sensor, and the feedback speed signal of the crank is fed back to the servo motor driver through a communication signal line to participate in control operation, so that the position control precision of the slide block of the servo press is improved.

Based on the control method, a method for estimating the slide pressure can be obtained, after the steps S1-S6, the method further comprises a step S7, the step S7 estimates the slide pressure of the servo press, and the current slide pressure value can be obtained through table lookup according to the mechanical parameters of the transmission mechanism of the servo press, the slide position and the current motor load torque value.

The above-described embodiment is only one of the preferred embodiments of the present invention, and general changes and substitutions by those skilled in the art within the technical scope of the present invention are included in the protection scope of the present invention.