阅读说明：本技术 一种伺服机压力位置控制方法、装置及伺服控制器 (Servo machine pressure position control method and device and servo controller ) 是由 高建波 李庆卓 李洪超 张博 贾中青 成巍 于 2019-11-22 设计创作，主要内容包括：本发明实施例公开了一种伺服机压力位置控制方法、装置及伺服控制器,方法包括根据冲压工艺确定冲压过程中的关键点及关键点处的参数值；根据参数值区分位置控制模式和压力位置控制模式,形成以时间为参变量的位置设定曲线和压力设定曲线；在位置控制模式下,通过位置设置曲线控制滑块的运动状态；在压力位置控制模式下,根据实际压力与设定压力的关系,选取滑块运动的控制模式。本发明对关键点参数值进行离线优化,将所有关键点作为一个整体进行处理,解决了现有技术中将每个伺服命令相互隔离,不能进行位置控制模式和压力位置控制模式在运动中切换的问题,使滑块能够在两种控制模式下平滑的切换,不必停止,满足冲压工艺需求,提高生产效率。(The embodiment of the invention discloses a method, a device and a servo controller for controlling the pressure position of a servo machine, wherein the method comprises the steps of determining key points and parameter values at the key points in the stamping process according to a stamping process; distinguishing a position control mode and a pressure position control mode according to the parameter values to form a position setting curve and a pressure setting curve which take time as a parameter; in the position control mode, the motion state of the sliding block is controlled through a position setting curve; and under the pressure position control mode, selecting a control mode of the movement of the sliding block according to the relation between the actual pressure and the set pressure. The invention carries out off-line optimization on the key point parameter values, treats all the key points as a whole, solves the problem that each servo command is isolated from each other and the position control mode and the pressure position control mode can not be switched during movement in the prior art, ensures that the sliding block can be smoothly switched under the two control modes without stopping, meets the requirement of a stamping process and improves the production efficiency.)

1. A pressure position control method of a servo is characterized by comprising the following steps:

determining a plurality of key points in the stamping process according to the stamping process, determining parameter values at each key point, and inputting the parameter values into a servo controller, wherein the parameter values comprise pressure and position;

the servo controller distinguishes a position control mode and a pressure position control mode according to the pressure of the key point, and determines a switching point and a transition area of the two modes;

respectively forming a position setting curve and a pressure setting curve by taking time as a parameter according to the parameter values;

in the position control mode, the motion state of the sliding block is controlled through a position setting curve, and the actual pressure is monitored; in the pressure position control mode, if the actual pressure does not exceed the set pressure at the current time, the motion state of the slide block is controlled according to the position setting curve, and if the actual pressure exceeds the set pressure at the current time, the motion state of the slide block is controlled according to the pressure setting curve.

2. The servo pressure position control method according to claim 1, wherein the switching point includes a first switching point and a second switching point; the first switching point is a switching point from a position control mode to a pressure position control mode, and a first transition area is formed between the first switching point and an adjacent previous key point of the first switching point; the second switching point is a switching point from the pressure position control mode to the position control mode, and a second transition area is formed between the second switching point and the next key point adjacent to the second switching point.

3. The servo pressure position control method according to claim 1, wherein the pressure setting curve is determined by a linear difference method, specifically:

the pressure between the kth keypoint and the (k +1) th keypoint is determined by

4. The servo pressure position control method according to claim 1, wherein in the position control mode, an actual pressure is monitored, and when the actual pressure exceeds a pressure of a pressure setting curve at a current time, an abnormality warning signal is issued.

5. The servo pressure position control method according to claim 1, wherein in the pressure position control mode, the specific control process for controlling the motion state of the slider according to the position setting curve is:

acquiring a position corresponding to the position setting curve at the current time, comparing the position with a motor position feedback value, and determining a position control speed;

the speed selector gates the position control speed, compares the position control speed with a motor speed feedback value, and controls the running speed of the motor through the speed controller so as to control the motion state of the sliding block.

6. The servo pressure position control method according to claim 1, wherein the specific process of controlling the moving state of the slider according to the pressure setting curve in the pressure position control mode is:

acquiring a pressure value corresponding to the pressure setting curve at the current time, comparing the pressure value with a pressure feedback value of the sliding block, and calculating the speed of the sliding block through a pressure controller;

calculating the pressure control speed of the motor by using a speed converter in combination with the position feedback value of the motor and the speed of the sliding block;

the speed selector gates the pressure control speed, compares the pressure control speed with a motor speed feedback value, and controls the running speed of the motor through the speed controller so as to control the motion state of the sliding block.

7. A servo pressure position control apparatus, comprising:

the user interface is used for inputting the key points and the corresponding parameter values by a user;

the control mode distinguishing module is used for distinguishing a position control mode and a pressure position control mode according to the pressure of the key point;

the punching curve off-line optimization module is used for respectively forming a position setting curve and a pressure setting curve which take time as a parameter according to the parameter values;

the servo control module is used for monitoring the actual pressure, judging whether the actual pressure is the corresponding set pressure at the current time or not, and selecting a control mode for controlling the running state of the stamping slide block according to the judgment result;

the control device is disposed on the servo controller.

8. The servo pressure position control device of claim 7, wherein the servo control module comprises:

the control command acquisition unit is used for acquiring the position corresponding to the position setting curve and the pressure corresponding to the pressure setting curve at the current time to form a position command and a pressure command;

the position controller calculates position control speed according to the position command and the motor position feedback value to form a position speed command and sends the command to the speed selector;

the pressure controller is used for calculating the speed of the sliding block according to the pressure command and the pressure feedback of the sliding block;

the speed converter is used for converting the slide block speed calculated by the pressure controller into the motor speed by combining the motor position feedback value to form a pressure speed command and sending the command to the speed selector;

the speed selector selects a position speed command or a pressure speed command according to a comparison result of the actual pressure and the set pressure, and sends the selection result to the speed controller;

and the speed controller determines the electrode running speed according to the selection result of the speed selector and the electrode speed feedback finger, so that the motion state of the sliding block is controlled.

9. A computer-readable storage medium having stored thereon a computer program which, when executed, performs the servo pressure position control method of any one of claims 1 to 6.

10. A servo controller, characterized in that the servo controller comprises the computer-readable storage medium of claim 9.

Technical Field

The invention relates to the technical field of presses, in particular to a method and a device for controlling the pressure position of a servo machine and a servo controller.

Background

In recent years, servo presses have been widely used in the stamping industry. As shown in fig. 1, the servo controller drives the slide block to move up and down through the crank connecting rod structure by the servo motor, and the slide block applies pressure to the workpiece to complete the material forming processing. A typical stamping process requires only precise control of the position of the slide in accordance with a target position profile. Certain processes require not only precise positional control, but also monitoring of pressure during the stamping stage, such as hot forming of high strength steel and carbon fiber sheets.

As shown in fig. 2, a press process of a servo press with pressure monitoring. One stamping process is usually to have the slide block move from the highest position (x)₀Point) start-up, first descending rapidly and then from a certain position (x)₂) The workpiece is punched at a slower speed to reach the lowest point x₃Holding for a period of time, waiting for the workpiece to form, and finally, from x₄Point begins to quickly ascend back to the highest point (x)₆Point, with x₀The points coincide). In the fast descending and fast ascending stages, the slide block does not contact the workpiece, the process does not care about pressure, but the position control is required to be relatively accurate. At x for slow pressing of workpieces₂To x₄In the process, the pressure is gradually increased. Some stamping processes require close monitoring of the pressure to prevent exceeding allowable values. The pressure needs to be monitored at this point, i.e. when the slide is moving from x₂To x₄During operation, the pressure cannot exceed p₂Warp p₃To p₄The resulting curve. If the pressure in the interval touches the limited curve, the slide block operates in a deceleration mode, and the pressure is prevented from rising continuously. In this process, the servo controller needs to control both the position and the pressure.

In the existing general numerical control system, in order to ensure the position precision, before each punching, a position control command must be used for returning to a zero point. But in order to pressWhen pressure monitoring is performed in the process, the control mode must be switched first, and the position control mode is switched to the pressure position control mode. And after the punching is finished, returning to the position control mode. During such control mode switching, the conventional general numerical control system requires that the servo motor must be stopped, i.e., x in the upper diagram₂And x₄The rotation speed of the servo motor must be equal to zero. Although this method brings versatility, in the servo controller, it means that the slide must be stopped briefly during the lowering process, which does not meet the requirement of the stamping process and seriously affects the production efficiency.

Disclosure of Invention

The embodiment of the invention provides a servo machine pressure position control method, a servo machine pressure position control device and a servo controller, and aims to solve the problem that a servo motor is required to stop in the process of converting a numerical control system of the servo controller from a position control mode to a pressure position control mode, and the production efficiency is seriously influenced.

In order to solve the technical problem, the embodiment of the invention discloses the following technical scheme:

the invention provides a servo pressure position control method in a first aspect, which comprises the following steps:

determining a plurality of key points in the stamping process according to the stamping process, determining parameter values at each key point, and inputting the parameter values into a servo controller, wherein the parameter values comprise pressure and position;

the servo controller distinguishes a position control mode and a pressure position control mode according to the pressure of the key point, and determines a switching point and a transition area of the two modes;

respectively forming a position setting curve and a pressure setting curve by taking time as a parameter according to the parameter values;

in the position control mode, the motion state of the sliding block is controlled through a position setting curve, and the actual pressure is monitored; in the pressure position control mode, if the actual pressure does not exceed the set pressure at the current time, the motion state of the slide block is controlled according to the position setting curve, and if the actual pressure exceeds the set pressure at the current time, the motion state of the slide block is controlled according to the pressure setting curve.

Further, the switching points include a first switching point and a second switching point; the first switching point is a switching point from a position control mode to a pressure position control mode, and a first transition area is formed between the first switching point and an adjacent previous key point of the first switching point; the second switching point is a switching point from the pressure position control mode to the position control mode, and a second transition area is formed between the second switching point and the next key point adjacent to the second switching point.

Further, the pressure setting curve is determined according to a linear difference method, specifically:

the pressure between the kth keypoint and the (k +1) th keypoint is determined by

Further, in the position control mode, the actual pressure is monitored, and when the actual pressure exceeds the pressure of the current time pressure setting curve, an abnormal alarm signal is sent out.

Further, in the pressure position control mode, a specific control process of controlling the motion state of the slider according to the position setting curve is as follows:

acquiring a position corresponding to the position setting curve at the current time, comparing the position with a motor position feedback value, and determining a position control speed;

the speed selector gates the position control speed, compares the position control speed with a motor speed feedback value, and controls the running speed of the motor through the speed controller so as to control the motion state of the sliding block.

Further, in the pressure position control mode, the specific process of controlling the motion state of the slider according to the pressure setting curve is as follows:

acquiring a pressure value corresponding to the pressure setting curve at the current time, comparing the pressure value with a pressure feedback value of the sliding block, and calculating the speed of the sliding block through a pressure controller;

calculating the pressure control speed of the motor by using a speed converter in combination with the position feedback value of the motor and the speed of the sliding block;

the speed selector gates the pressure control speed, compares the pressure control speed with a motor speed feedback value, and controls the running speed of the motor through the speed controller so as to control the motion state of the sliding block.

A second aspect of the present invention provides a servo pressure position control apparatus, comprising:

the user interface is used for inputting the key points and the corresponding parameter values by a user;

the control mode distinguishing module is used for distinguishing a position control mode and a pressure position control mode according to the pressure of the key point;

the punching curve off-line optimization module is used for respectively forming a position setting curve and a pressure setting curve which take time as a parameter according to the parameter values;

the servo control module is used for monitoring the actual pressure, judging whether the actual pressure is the corresponding set pressure at the current time or not, and selecting a control mode for controlling the running state of the stamping slide block according to the judgment result;

the control device is disposed on the servo controller.

Further, the servo control module includes:

the control command acquisition unit is used for acquiring the position corresponding to the position setting curve and the pressure corresponding to the pressure setting curve at the current time to form a position command and a pressure command;

the position controller calculates position control speed according to the position command and the motor position feedback value to form a position speed command and sends the command to the speed selector;

the pressure controller is used for calculating the speed of the sliding block according to the pressure command and the pressure feedback of the sliding block;

the speed converter is used for converting the slide block speed calculated by the pressure controller into the motor speed by combining the motor position feedback value to form a pressure speed command and sending the command to the speed selector;

the speed selector selects a position speed command or a pressure speed command according to a comparison result of the actual pressure and the set pressure, and sends the selection result to the speed controller;

and the speed controller determines the electrode running speed according to the selection result of the speed selector and the electrode speed feedback finger, so that the motion state of the sliding block is controlled.

A third aspect of the present invention is a computer-readable storage medium having stored thereon a computer program which, when executed, executes the servo pressure position control method.

A fourth aspect of the invention provides a servo controller comprising said computer readable storage medium.

Drawings

In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.

FIG. 1 is a schematic structural diagram of a slider driven by a motor;

FIG. 2 is a graph of position setting versus pressure setting versus time for a press process in a prior art servo controller with pressure monitoring;

FIG. 3 is a schematic diagram of the construction of the apparatus of the present invention;

FIG. 4 is a schematic flow diagram of the method of the present invention;

FIG. 5 is a schematic control flow diagram of the pressure position control mode of the present invention;

FIG. 6 is a schematic diagram of a position setting curve and a pressure setting curve obtained when applied to an example based on the method of the present invention;

fig. 7 is a diagram showing an actual curve of the position and the pressure in the control process based on the example of fig. 6.

Detailed Description

In order to clearly explain the technical features of the present invention, the following detailed description of the present invention is provided with reference to the accompanying drawings. The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. To simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Furthermore, the present invention may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. It should be noted that the components illustrated in the figures are not necessarily drawn to scale. Descriptions of well-known components and processing techniques and procedures are omitted so as to not unnecessarily limit the invention.

As shown in fig. 3, the servo pressure position control apparatus of the present invention includes a user interface, a control mode differentiation module, a punching curve offline optimization module and a servo control module.

The user interface is used for inputting key points and corresponding parameter values by a user; the control mode distinguishing module distinguishes a position control mode and a pressure position control mode according to the pressure of the key point; the punching curve off-line optimization module is used for respectively forming a position setting curve and a pressure setting curve which take time as a parameter according to the parameter values; the servo control module is used for monitoring the actual pressure, judging whether the actual pressure is the corresponding set pressure at the current time or not, and selecting a control mode for controlling the running state of the stamping slide block according to the judgment result; the control device is arranged on the servo controller.

The servo control module comprises a control command acquisition unit, a position controller, a pressure controller, a speed transducer, a speed selector and a speed controller.

The command acquisition unit is used for acquiring a position corresponding to the position setting curve and a pressure corresponding to the pressure setting curve at the current time to form a position command and a pressure command; the position controller calculates position control speed according to the position command and the motor position feedback value to form a position speed command and sends the command to the speed selector; the pressure controller feeds back the pressure command and the slide pressure to calculate the slide speed; the speed converter converts the slide block speed calculated by the pressure controller into the motor speed by combining the motor position feedback value to form a pressure speed command and sends the command to the speed selector; the speed selector selects a position speed command or a pressure speed command according to a comparison result of the actual pressure and the set pressure, and sends the selection result to the speed controller; and the speed controller determines the electrode running speed according to the selection result of the speed selector and the electrode speed feedback finger, so that the motion state of the sliding block is controlled.

As shown in fig. 4, the method for controlling the pressure position of the servo of the present invention includes the steps of:

s1, determining a plurality of key points in the stamping process according to the stamping process, determining parameter values at each key point, and inputting the parameter values into a servo controller, wherein the parameter values comprise pressure and position;

s2, the servo controller distinguishes the position control mode and the pressure position control mode according to the pressure of the key point, and determines the switching point and the transition area of the two modes;

s3, respectively forming a position setting curve and a pressure setting curve by taking time as a parameter according to the parameter values;

s4, in the position control mode, controlling the motion state of the slide block through the position setting curve and monitoring the actual pressure; in the pressure position control mode, if the actual pressure does not exceed the set pressure at the current time, the motion state of the slide block is controlled according to the position setting curve, and if the actual pressure exceeds the set pressure at the current time, the motion state of the slide block is controlled according to the pressure setting curve.

In step S1, the key point parameter values include: position x_kK is 0 … N, the number of keypoints is (N + 1); velocity v_kThe running speed of the slide block is between the current key point and the next key point; pressure p_kPressure setting of the key point.

In step S2, the switching points include a first switching point and a second switching point; the first switching point is a switching point from the position control mode to the pressure position control mode, and a first transition area is formed between the first switching point and the last key point adjacent to the first switching point; the second switching point is a switching point from the pressure position control mode to the position control mode, and a second transition area is formed between the second switching point and the next key point adjacent to the second switching point.

The pressure position control mode starts from the ith key point and ends from the jth key point (i < j), i.e. i and j are the first switching point and the second switching point respectively, then the servo controller automatically brings the (i-1) th key point and the (j +1) th key point into the range of the pressure position control mode, and replaces the key point parameters input by the user with the following data:

p_i-1＝＝Pmax；

p_j+1＝Pmax；

where Pmax is the maximum operating pressure of the press. Namely, the two control modes can be regarded as a first transition area and a second transition area between the (i-1) th point and the (j +1) th point respectively.

At the same time, the pressure setting parameters for all other key points in the position control mode are set to maximum, i.e.:

p_m＝Pmax,m＝0…N，m<i-1,m>j+1。

in step S3, a position setting curve is generated according to a conventional general-purpose curve interpolation technique. The pressure setting curve is determined according to a linear difference method, and specifically comprises the following steps:

the pressure between the kth keypoint and the (k +1) th keypoint is determined by

In step S4, the servo controller performs automatic control according to the two curves generated in step S3. Position control is performed for the ranges of k < i-1 and k > j + 1. And in the position control mode, monitoring the actual pressure, and sending an abnormal alarm signal to stop the stamping process when the actual pressure exceeds the pressure of the pressure setting curve at the current time. And automatically controlling the pressure position in the ranges of k < i > -1 and k < j +1, and in the pressure position control mode, when the pressure position control mode is operated to a transition region from the position control mode to the pressure position control mode (namely k < -1 >), if the actual pressure does not exceed the maximum pressure value of the press machine, the servo motor continues to operate according to the position setting curve without stopping, and the servo controller naturally and smoothly enters the pressure position control mode. The motor also need not be required to stop rotating when exiting the pressure position control mode; and if the actual pressure exceeds the set pressure at the current time, controlling the motion state of the slide block according to the pressure set curve.

As shown in fig. 5, the specific control process for controlling the motion state of the slider according to the position setting curve is as follows:

obtaining a position corresponding to a position setting curve at the current time to form a position instruction, comparing the position with a motor position feedback value to control the position, wherein a command output by a position controller is used for controlling the speed of a motor and determining the position control speed, and the position control speed is called as a position speed command; the position control speed is compared with the motor speed feedback after being gated by the speed selector, and the speed of the motor is controlled by the speed controller, so that the position of the motor closely tracks a position command curve. Because the rotation angle of the motor and the position of the sliding block have a one-to-one correspondence relationship through a rigid transmission system of the servo controller, the position control of the motor is actually the position control of the sliding block, and therefore the control of the motion state of the sliding block is realized.

Under the pressure position control mode, the specific process of controlling the motion state of the slide block according to the pressure setting curve is as follows:

and acquiring a pressure value corresponding to the pressure setting curve at the current time to form a pressure command. Comparing the pressure value with a slide block pressure feedback value, and calculating the slide block speed through a pressure controller; calculating the pressure control speed of the motor by combining the position feedback value of the motor and the speed of the sliding block and utilizing a speed converter to form a pressure speed instruction; the speed selector gates the pressure control speed, compares the pressure control speed with the motor speed feedback value, and controls the running speed of the motor through the speed controller so as to control the motion state of the sliding block.

The position controller, the pressure controller and the speed controller in the control process are all common PI controllers in the prior art.

In the speed converter, the conversion formula of the slide block speed and the motor speed is as follows:

where ω is the motor speed command, i.e. "pressure speed command" in the figure, v_sIs the speed of the slide, and,

is the differential of the slide position h to the motor angle theta, and the communication relation between the two is expressed in a functional formComprises the following steps:

h＝f(θ),

f is generally a non-linear function uniquely determined by the mechanical structure of the press drive train.

The speed selector selects such that the slide approaches the bottom dead center at a slower speed or moves away from the bottom dead center at a faster speed to control the speed of the motor.

Referring to fig. 6 and 7, the following describes a specific implementation process of the method of the present invention with reference to specific examples.

The position curve of the stamping process consists of 6 key points x₀To x₅And the velocity v between two adjacent points₀To v₅The specification is carried out. x is the number of₆And x₀The coincidence, which is actually a point in space, does not account for critical points. Suppose the process requires from time t₂To t₄The pressure position control is carried out, and the pressure value at the 3 key points is p₂、p₃And p₄And (4) defining. The above position, velocity and pressure parameters are input by the user and the time is calculated from the position and velocity.

Based on the method of the embodiment of the invention, the pressure value is also given to the key point which is not subjected to pressure position control, and the given pressure value is the maximum value which can be borne by the pressure machine. A curve as shown in fig. 6 is obtained.

Only at time t due to process requirements₂To t₄The pressure position control is performed, so that the pressure curve defined at other positions is only used for pressure monitoring, and the pressure control is not performed. If the pressure exceeds the upper limit curve, the abnormal condition is indicated, and the servo control device gives an alarm and stops the machine. This is reasonable and necessary for the stamping to produce this condition.

As shown in fig. 7, at t₀To t₁And in the stage, position control is carried out, and the actual position of the sliding block completely runs according to a position setting curve. At t₁To t₂In the transition region between the two modes, the pressure position control mode is actually operated. Generally, the actual pressure of the slide is equal to zero when the slide is not yet in contact with the workpiece. At t₂At some later time, the slider contacts the workpiece and the pressure gradually increases. Subsequently, at some point in time the actual pressure reaches the pressure set curve, at which point the slide is run at a reduced speed, and the position deviates from the set curve. From t₃At the beginning of time, the slider maintains pressure according to the pressure setting. To limit pressure overrun, the slide position does not reach the set curve. Time of arrival t₄Then at t₅Previously, in the mode switching transition region, the pressure position control is actually still performed. In this interval, the slide leaves the workpiece, travels back up, and the pressure rapidly decreases to zero, without the requirement that the motor speed must return to zero. Reaches t₅Thereafter, the slider is returned to the top dead center in the position control mode.

In summary, the invention performs comprehensive processing on the key point parameters including the position and the pressure of the slide block input by a user before performing the motor servo control through the off-line optimization of the stamping curve, and linearly expands the key point pressure parameters at the junction of the position control mode and the pressure position control mode, so as to respectively generate complete set curves for the position and the pressure to perform the motor servo control, thereby enabling the servo controller not to force the rotating speed of the servo motor to be reduced to zero in the switching process from the position control mode to the pressure position control mode, and further meeting the requirement of the continuity of the stamping process.

The foregoing is only a preferred embodiment of the present invention, and it will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the principle of the invention, and such modifications and improvements are also considered to be within the scope of the invention.