阅读说明：本技术 一种伺服压力机滑块位置偏差在线自动修正方法 (Online automatic correction method for position deviation of slide block of servo press ) 是由 高建波 李庆卓 李琦 贾中青 张振振 李海明 于 2019-08-29 设计创作，主要内容包括：本发明公开了一种伺服压力机滑块位置偏差在线自动修正方法,利用电子传感器检测滑块实际位置与理论位置之间的偏差,读取上一个控制周期电机原始位置命令a<Sub>n</Sub>和上一控制周期计算的最新控制补偿量c<Sub>n</Sub>；根据当前系统反馈的滑块实际位置h<Sub>n</Sub>更新电机位置命令补偿量：c<Sub>n+1</Sub>＝c<Sub>n</Sub>+a<Sub>n</Sub>-g(h<Sub>n</Sub>),h<Sub>n</Sub>为根据上一控制周期发出的补偿后位置命令而产生的滑块位置在当前控制周期内的实测值；控制器发出带补偿的位置命令b<Sub>n+1</Sub>＝a<Sub>n+1</Sub>+c<Sub>n+1</Sub>,其中a<Sub>n+1</Sub>为当前周期电机原始控制位置命令,从而能够消除或大幅度减小滑块实际位置与理论值的偏差。本方法不需要对压力机的机械结构进行改变。可应用于各种往复模式运动的压力机。(The invention discloses an on-line automatic correction method for the position deviation of a slide block of a servo press, which utilizes an electronic sensor to detect the deviation between the actual position and the theoretical position of the slide block and reads the original position command a of a motor in the previous control period n And the latest control compensation amount c calculated in the previous control period n (ii) a According to the actual position h of the slide block fed back by the current system n Updating the compensation amount of the motor position command: c. C n+1 ＝c n +a n ‑g(h n )，h n the actual measurement value of the slide block position in the current control period is generated according to the compensated position command sent by the previous control period; the controller issues a position command b with compensation n+1 ＝a n+1 +c n+1 Wherein a is n+1 The command is the original control position of the motor in the current period, so that the deviation of the actual position of the sliding block from the theoretical value can be eliminated or greatly reduced. The method does not require changes to the mechanical structure of the press. The method can be applied to various reciprocating mode moving presses.)

1. An on-line automatic correction method for the position deviation of a slide block of a servo press is characterized by comprising the following steps:

Defining the motor position, namely the rotor angle of the motor is a, the slide block stroke is s, and the relation between the two is dependent on a transmission system and is uniquely determined: s ═ f (a), the inverse function is a ═ g(s), the compensation amount is defined as c, the command after compensation is b ═ a + c, the slide position feedback value is defined as h, the last control period is defined as n, the current control period is defined as n +1, wherein n is a natural number;

Step one, starting a stamping process, initializing compensation quantity, c₁0; the original control position command of the motor is an initial position a₁The control command after compensation is b₁＝a₁+c₁＝a₁the system sends a command b to the motor controller₁enabling n to be 1, and entering a step two after the first control period is finished;

Step two, reading the original position command a of the motor in the previous control period_nAnd the latest control compensation amount c calculated in the previous control period_n；

Thirdly, according to the actual position h of the sliding block fed back by the current system_nUpdating the compensation amount of the motor position command: c. C_n+1＝c_n+a_n-g(h_n)，h_nThe actual measurement value of the slide block position in the current control period is generated according to the compensated position command sent by the previous control period;

step four, the controller sends out a position command b with compensation_n+1＝a_n+1+c_n+1wherein a is_n+1The motor original control position command is obtained in the current period;

And step five, adding 1 to n, waiting for the end of the current control period, and if the stamping stroke is not ended, executing the step two to the step four again until the stamping stroke is ended.

2. The method for on-line automatic correction of the position deviation of the slide block of the servo press as claimed in claim 1, wherein the servo press is a crank-connecting rod press, and the corresponding function f is as follows:

Where s is the slide position, a is the motor position, i.e., the rotor angle, R is the crank length, L is the link length, and R is the reduction ratio between the motor and the crankshaft.

3. The method for on-line automatic correction of the position deviation of the slide block of the servo press as claimed in claim 1, wherein the servo press is a screw servo press, and the corresponding function f is:

Where s is the slide position, a is the motor position, i.e., the rotor angle, r is the reduction ratio between the motor and the screw, and x is the screw lead.

4. The method for automatically correcting the position deviation of the slide block of the servo press as claimed in claim 1, wherein the servo press is a crank multi-link servo press.

5. the method for automatically correcting the position deviation of the slide block of the servo press as claimed in claim 1, wherein the servo press is a screw multi-link servo press.

Technical Field

The invention relates to the technical field of servo press control, in particular to an on-line automatic correction method for position deviation of a slide block of a servo press.

background

Servo presses have been widely used in the stamping industry. The servo press machine drives the sliding block to move up and down through a mechanical mechanism by a servo motor, and the material forming processing is completed by applying pressure to the workpiece. The overall structure of the servo press is shown in figure 2. The servo motor and the sliding block are rigidly connected through a mechanical mechanism. Theoretically, the position of the sliding block can be accurately controlled by controlling the operation of the servo motor. In the existing practical system, a user inputs expected slide block operation position parameters through an interface, then a central controller calculates a position command curve of a motor according to the corresponding relation between the position of the motor and the position of the slide block, sends the position commands of the motor to a servo driver one by one in the control process to control the motor, and drives the slide block to move up and down through a mechanical mechanism.

Due to the clearance between the moving parts of the mechanical mechanism and the elastic deformation of the mechanical system, the actual position and the theoretical position of the slider are often unequal, and the larger the pressure applied by the slider, the larger the error. This is shown in fig. 3, where the "motor position curve" in fig. 3 is calculated by the control system according to the user input parameters, and the dashed line "theoretical curve" in the "slide position curve" is the slide position curve calculated from the motor position curve according to the rigidity relationship of the press mechanical structure, and is also the track that the user wants the slide to run. However, the actual operating curve of the slider ("actual curve" in fig. 3) deviates from the theoretical curve due to external influences such as clearance, deformation, wear, and temperature. This deviation causes a reduction in the processing accuracy of the press. And as production time goes on, the deviation becomes larger and larger, and the calibration must be performed manually at regular intervals. This reduces the product yield, increases maintenance work, and reduces production efficiency.

The patent (No. 201220701430.2) discloses a double point open press with slide running error prevention and compensation. Can be used for servo press. The method is characterized in that a mechanical compensation mechanism is added to the press machine to compensate and correct the position deviation of the sliding block. This requires a change in the mechanical structure of the press, and the main frame of the press must be redesigned, which results in a large amount of work and high cost. In addition, for different working conditions, repeated tests are required in advance, and parameters of the compensation mechanism are set. If the working condition changes, the compensation is insufficient or excessive, and the compensation function is lost.

Disclosure of Invention

The invention aims to solve the defects in the prior art, and provides an on-line automatic correction method for the position deviation of the slide block of the servo press. The method does not require changes to the mechanical structure of the press. The press can be applied to various reciprocating mode moving presses, namely, a servo motor drives a sliding block to move downwards when rotating towards one direction and drives the sliding block to move upwards when rotating towards the other direction, and the press comprises a screw press, a screw multi-connecting-rod press and a crank-connecting-rod press.

The technical scheme adopted by the invention for solving the technical problems is as follows:

an on-line automatic correction method for the position deviation of a slide block of a servo press comprises the following steps:

Defining the motor position, namely the rotor angle of the motor is a, the slide block stroke is s, the relation between the two is dependent on the transmission system and is uniquely determined: s ═ f (a), the inverse function is a ═ g(s), the compensation amount is defined as c, the command after compensation is b ═ a + c, the slide position feedback value is defined as h, n used in the following steps is a natural number, the last control period number is defined as n, and the current control period number is n + 1;

The transmission system is a transmission conversion mechanism from a servo motor to a sliding block.

Step one, starting a stamping process, initializing compensation quantity, c₁0; make electricityThe original control position command of the machine is an initial position a₁The control command after compensation is b₁＝a₁+c₁＝a₁The system sends a command b to the motor controller₁Enabling n to be 1, and entering a step two after the first control period is finished;

step two, reading the original position command a of the motor in the previous control period_nand the latest control compensation amount c calculated in the previous control period_n；

Thirdly, according to the actual position h of the sliding block fed back by the current system_nUpdating the compensation amount of the motor position command: c. C_n+1＝c_n+a_n-g(h_n)，h_nThe actual measurement value of the slide block position in the current control period is generated according to the compensated position command sent by the previous control period;

step four, the controller sends out a position command b with compensation_n+1＝a_n+1+c_n+1Wherein a is_n+1The motor original control position command is obtained in the current period;

And step five, adding 1 to n, waiting for the end of the current control period, and if the stamping stroke is not ended, executing the step two to the step four again until the stamping stroke is ended.

The servo press machine is a crank connecting rod press machine, and the corresponding function f of the crank connecting rod press machine is as follows:

Where s is the slide position, a is the motor position, i.e., the rotation angle, R is the crank length, L is the link length, and R is the reduction ratio from the motor to the crankshaft.

the servo press is a screw servo press, and the corresponding function f of the screw servo press is as follows:

Where s is the slide position, a is the motor position, i.e., the rotation angle, r is the reduction ratio from the motor to the screw, and x is the screw lead.

The servo press is a crank multi-connecting-rod servo press.

The servo press is a spiral multi-connecting-rod servo press.

the invention has the beneficial effects that:

1. The slide block position compensation control method provided by the invention can update the motor servo control command in real time according to the actual motor position and the actual slide block position in the servo press slide block position control process, and the slide block moves towards the direction of reducing the error by adding compensation in the servo command, so that the slide block position error caused by a press machine mechanical system is eliminated.

2. In the prior art, a mechanical method is adopted to compensate the position deviation of a press slide block, and compensation machinery needs to be adjusted in advance for different working conditions. If the operating conditions change, the compensation amount is insufficient or excessive. The motor servo control method adopted by the method of the invention does not need to change the body of the press machine, and can realize the effect of completely eliminating the deviation.

Drawings

FIG. 1 is a control flow diagram of the present invention;

FIG. 2 is a view showing the overall structure of a conventional servo press;

FIG. 3 is a graph of the motor control curve, slider theoretical and actual position curves of the present invention;

FIG. 4 is a diagram illustrating the operation of the present invention;

FIG. 5 is a system diagram of a servo press with a slider position deviation compensation method of the present invention;

FIG. 6 is a block diagram of a control system of the control method of the present invention.

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. The terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," and the like are used in the orientation or positional relationship indicated in the drawings for convenience in describing the invention and for simplicity in description, and do not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be construed as limiting the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

As shown in fig. 5, the present invention utilizes an electronic sensor to detect the deviation between the actual position and the theoretical position of the slider, and the electronic sensor generally adopts a grating ruler. And the deviation is used for compensating the motor position control command, so that the deviation between the actual position of the sliding block and a theoretical value can be eliminated or greatly reduced. The invention does not require changes to the mechanical structure of the press.

the present invention is applicable to a variety of presses, including screw presses, screw multi-link presses, and crank-link presses. The invention requires the press to operate in a reciprocating mode, i.e. the servo motor drives the slide down when rotating in one direction and drives the slide up when rotating in the other direction. Another requirement of the present invention is that the user set lower limit of the ram pressure for the slide should be above bottom dead center by a distance greater than the deviation of the slide position due to mechanical play and deformation.

Referring to fig. 4, the working principle of the present invention is illustrated, in which a press machine using a crank multi-link mechanism is described according to the control flow shown in fig. 1: the curve at the upper right corner is the relationship between the slide travel and the motor position (i.e., the rotation angle), which is a typical transmission relationship for a crank-link press (lower right corner of the figure). The motor is connected with the crank through a mechanical speed reducing mechanism. The position of the slide block at the bottom dead center (namely the lowest point) is defined to be zero, and the position of the corresponding motor is also defined to be zero.

The motor starts rotating from position 1, via positions 2 and 3 to a minimum position 4, and then back to the initial position 5, according to the "motor position curve" in the upper left corner. Position 5 and position 1 coincide spatially. Correspondingly, the slider should ideally follow the "slider travel curve" in the lower right hand corner of the figure from the highest point 11, past points 12 and 13 to the lowest point 14, and then back to the initial position 15. Positions 15 and 11 coincide spatially.

in fact, due to mechanical play, distortion and other errors, when the servo controller controls the motor to rotate to position 3, the slide does not reach the theoretical position 13, but is in position 12 (typically 12 is higher than 13). To reduce this deviation, the motor position 2 corresponding to the slide position 12 is calculated, then the difference between the current motor actual output position command and the calculated position 2 is calculated, and the motor position control command compensation amount is updated with this difference, adding the compensation amount to the motor position original command stored in the controller. The compensated control command will exert an additional force on the slider to move it faster towards the desired position. If the compensation operation is continuously carried out in the whole control process, the actual position of the sliding block approaches to the set position, and the position deviation compensation of the sliding block is realized. Ideally, zero error can be achieved.

in actual operation, the motor control adopts a digital control method, and a position servo control algorithm is repeatedly and circularly executed at a certain period (the period is determined according to the performance of the controller, the shorter the period is, the better the period is, and the control period of the invention is about 20 ms). In each control period, the algorithm firstly reads the actual command and the latest error condition output after compensation in the last period to update the compensation amount of the control command, and compensates the original control command of the motor according to the updated compensation amount. According to fig. 4, a single control cycle is specifically executed as follows:

Defining the motor position, namely the rotor angle of the motor is a, the slide block stroke is s, the relation between the two is dependent on the transmission system and is uniquely determined: the inverse function a g(s), the compensation amount c, the command b after compensation a + c, the slider position feedback value h, n used in the following steps is a natural number, the last control cycle number is defined as n, and the current control cycle number is defined as n + 1.

The motor positions at points 1, 2, 3, 4, 5 in the motor position curve in fig. 4 are respectively defined as a₁，a₂，a₃，a₄，a₅(ii) a The stroke of the slide at each point 11 to 15 in the curve of the stroke of the slide is defined as s₁，…，s₅(ii) a The slide position 14 is the lower punch limit, i.e., the lowest point of slide movement required for this process curve.

Starting the stamping process, initializing the compensation quantity, c₁0; the original control position command of the motor is an initial position a₁The control command after compensation is b₁＝a₁+c₁＝a₁The system sends a command b to the motor controller₁And keeping n equal to 1, waiting for the end of the first control period, and continuing to execute the next step.

We assume that the servo controller primitive command of the previous control cycle requires the motor to rotate to position a₃And the controller actually issues the signal with the compensation quantity c₃And controlling the motor to rotate to the following positions:

b₃＝a₃+c₃

If the compensation is complete, the slide should be moved to position s₃i.e. by

s₃＝f(a₃)

But in practice the slide has only moved to a stroke s, 12 in figure 4₂(i.e. the actual position feedback value h we define₃) (ii) a This point corresponds to the motor position a₂. To compensate for the slider position error, the amount of compensation commanded by the motor needs to be updated. The updated compensation amount is:

c₄＝c₃+a₃-a₂

a₂＝g(s₂)＝g(h₃)

Namely: c. C₄＝c₃+a₃-g(h₃)

The controller then issues a position command b with compensation₄＝a₄+c₄Wherein a is₄The motor original control position command is obtained in the current period; and repeating the steps until the stamping stroke is finished, namely, the slide block detected by the grating ruler reaches the designated position.

The control method may be represented as a block diagram of the control system shown in fig. 6, where the actual slider position is subtracted from the theoretical slider position corresponding to the motor position. And the module 8 performs addition operation, and adds a compensation value to the motor position original command calculated by the central controller according to the user parameter to obtain a compensated motor position command.

The on-line automatic correction of the position deviation of the sliding block has another solution: that is, by determining the direction of the slider position deviation and accumulating a small fixed compensation value in each control cycle in the motor position command, rather than calculating the compensation value using a motor-slider position relationship curve, the slider position error can be gradually reduced, but this method requires a long time and generally cannot achieve complete compensation. The method comprises the following specific steps:

defining the motor position, namely the rotor angle of the motor is a, the slide block stroke is s, the relation between the two is dependent on the transmission system and is uniquely determined: s ═ f (a), the inverse function is a ═ g(s), the compensation amount is defined as c, the command after compensation is b ═ a + c, the slide position feedback value is defined as h, n used in the following steps is a natural number, the last control period number is defined as n, and the current control period number is n + 1;

Step one, starting a stamping process, initializing compensation quantity, c₁0; the original control position command of the motor is an initial position a₁The control command after compensation is b₁＝a₁+c₁＝a₁The system sends a command b to the motor controller₁enabling n to be 1, and entering a step two after the first control period is finished;

step two, reading the original position command a of the motor in the previous control period_nand the latest control compensation amount c calculated in the previous control period_n；

Thirdly, according to the actual position h of the sliding block fed back by the current system_nAnd the desired position s_nThe sign of the difference value updates the motor position command compensation amount:

c_n+1＝c_n+Csign(s_n-h_n)

wherein the constant C is a smaller deviation compensation value and is a positive number, the function sign () represents a sign-solving operation, if the variable in the brackets is the positive number operation result is 1, if the variable is the negative number result is-1, if the variable is zero, the result is zero;

Step four, the controller sends out a position command b with compensation_n+1＝a_n+1+c_n+1Wherein a is_n+1the motor original control position command is obtained in the current period;

And step five, adding 1 to n, waiting for the end of the current control period, and if the stamping stroke is not ended, executing the step two to the step four again until the stamping stroke is ended.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.