阅读说明：本技术 一种伺服压力机下死点偏差反馈补偿方法 (Servo press bottom dead center deviation feedback compensation method ) 是由 高建波 李琦 王启武 范宏伟 张国强 贾中青 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下死点偏差反馈补偿方法,在一个冲压过程中,电机按照补偿后的曲线运行。第一个冲压过程补偿量为零。每个冲压过程中滑块经过下死点后的回程过程中,控制软件根据偏差反馈补偿算法计算补偿量,并计算新的补偿后曲线,最后按照新的补偿后曲线控制伺服电机旋转。能够在每个冲压过程中对滑块下死点实际值与期望值之间的误差进行测量,并利用反馈控制原理对伺服电机位置曲线进行自动补偿,经过几次冲压周期以后,能够将滑块下限误差减小到零,并且在外界条件发生变化导致误差增大时,随时进行曲线补偿,确保滑块下死点等于期望值。(The invention discloses a servo press bottom dead center deviation feedback compensation method. The first press run offset is zero. In the return stroke process after the sliding block passes through the lower dead point in each stamping process, the control software calculates the compensation amount according to the deviation feedback compensation algorithm, calculates a new curve after compensation, and finally controls the servo motor to rotate according to the new curve after compensation. The method has the advantages that the error between the actual value and the expected value of the bottom dead center of the sliding block can be measured in each punching process, the position curve of the servo motor is automatically compensated by using the feedback control principle, the lower limit error of the sliding block can be reduced to zero after several punching cycles, and the curve compensation can be carried out at any time when the error is increased due to the change of external conditions, so that the bottom dead center of the sliding block is ensured to be equal to the expected value.)

1. A feedback compensation method for the deviation of the bottom dead center of a servo press is characterized in that,

Defining a motor position setting curve as theta_aI.e. the motor angle curve under ideal conditions;

Defining the curve of the motor after position compensation as theta_bNamely a motor position running command actually sent by a motor controller;

Defining the expected bottom dead center as h₁₂The bottom dead center actually reached by the slider is h₁₄；

The method comprises the following steps:

Step one, starting a stamping process, and detecting the actual value h of the bottom dead center of the slider at the kth time₁₄(k) calculating the k-th actual value and the expected value h₁₂(k) Deviation value h of_e(k)

h_e(k)＝h₁₂-h₁₄(k)

Step two, calculating a new motor position compensation value theta_c(k+1)

θ_c(k+1)＝θ_c(k)+G·h_e(k)

Wherein:

k is the number of stamping processes, and k is a natural number;

θ_c(k) Compensating the k-th motor position curve by using the compensation quantity, wherein when k is 1, theta_c(1)＝0；

G is the error magnification

the value range of r is 0.1-1.0,

h_dThe position deviation of the sliding block caused by the deformation of the machine body at the bottom dead center when the press is loaded and operated;

θ_dThe rotating angle of the motor corresponding to the position deviation of the sliding block at the bottom dead center;

h_dand theta_dObtained by test measurement;

Step three, obtaining the latest compensation value theta through the step two_c(k +1) is used for compensating the servo motor position curve so as to obtain a latest compensated curve theta_b(k +1), i.e.

wherein: when k is 1

h₁₄(1)＝h₁₂

θ_b(1)＝θ_a。

Technical Field

The invention relates to the technical field of servo press control, in particular to a servo press bottom dead center deviation feedback compensation method.

Background

In recent years, 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 press structure is shown in figure 5.

A user inputs expected slide block operation position parameters through a user interface, then the central controller calculates a set curve of the motor position according to the corresponding relation between the motor position and the slide block position, and sends control commands to the servo driver one by one according to the set curve value in the control process. The servo driver drives the motor to rotate and drives the sliding block to move up and down through the transmission mechanism. The most important position of the slide in the stamping production is the bottom dead center, i.e. the lowest point of each stamping. This position must be accurate to ensure the accuracy of the workpiece formation.

Because the servo motor and the sliding block are rigidly connected through the transmission mechanism, theoretically, the position of the sliding block can be accurately controlled by controlling the rotation angle of the servo motor, namely the position of the motor. However, in a practical system, it is difficult to ensure that the bottom dead center is equal to the desired value due to the mechanical elastic deformation of the transmission. Further, as the wear increases, the bottom dead center gradually deviates from the desired value.

In order to eliminate the influence of the above factors on the bottom dead center accuracy, a commonly used compensation method at present is to finely adjust the height of the slider, that is, the height of the component a in the upper drawing is adjusted by an auxiliary motor, so as to adjust the height of the lower surface of the slider. Such fine tuning may be performed manually or automatically. The prior patent art mentions two techniques.

the patent application number 201110231330.8 discloses a servo press control method, in particular a servo press bottom dead center control method. The control method comprises a bottom dead point reading and judging module, a comparing module and a threshold value module: the bottom dead point reading and judging module judges continuous signals in each working cycle period detected by the slide block displacement sensor and reads a bottom dead point position value in the current cycle period; the comparison module compares the read current bottom dead center position value with a system set value and calculates the offset of the bottom dead center; the threshold value module is responsible for comparing the offset of the bottom dead center of the current slide block with a set threshold value, and if the offset of the bottom dead center is larger than the set threshold value, the system starts the mold adjusting system to adjust the slide block to the instruction bottom dead center. The invention provides a servo press control method for automatically adjusting the bottom dead center of a sliding block, which meets the working requirement of precision stamping of a press.

The patent (application number: 201210066722.8) discloses a bottom dead center dynamic compensation mechanism of a high-speed precision press, which belongs to the technical field of pressure machinery and comprises a shaft arranged on a connecting rod through two cylindrical roller bearings and a shaft seat, wherein the shaft is of a middle eccentric structure, a worm and a worm gear mechanism are arranged at one end of the shaft, the worm is connected with the shaft, the worm is fixed on the connecting rod through a bearing seat and is connected with a servo motor through an elastic flexible shaft, and the servo motor is fixed on a press body. The servo motor dynamic compensation device has the advantages that through the unique shaft supporting mechanism, the friction resistance which is overcome during dynamic compensation is small, the bearing capacity is large during stamping, the assembly is convenient, the threads of the die-filling height adjustment part of the sliding block do not need to be loosened during compensation, the precision deviation of the bottom dead center of the sliding block caused by thread clearance is eliminated, the dynamic compensation of the bottom dead center is realized, the high stamping precision of a press machine is ensured, the quality of a stamping part is improved, the service life of a die is prolonged, meanwhile, the servo motor is directly fixed on the body of the press machine and is not subjected to vibration impact, and the.

In the existing patent method, mechanical parts connected with the sliding block are adjusted through an additional auxiliary motor, and the height of the sliding block is changed, so that bottom dead center compensation is realized. Because the auxiliary motor can only drive the mechanical parts to complete the compensation operation when the slide block returns to the higher position without stress, and the starting and stopping of the auxiliary motor also require time, the prior art does not have enough time to complete the bottom dead center automatic compensation operation in the continuous stamping process.

in addition, since the mechanical operation is inconvenient, the prior art attempts to reduce the number of compensation adjustments, so that the compensation is performed only when the bottom dead center deviation exceeds a certain threshold. This results in that the bottom dead center deviation tends to approach the set threshold value, and thus high accuracy cannot be achieved.

disclosure of Invention

the invention aims to solve the defects in the prior art, and provides a servo press bottom dead center deviation feedback compensation method which can measure the error between the actual value and the expected value of the bottom dead center of a slide block in each stamping process and automatically compensate the position curve of a servo motor by using a feedback control principle. The compensation process is completed in software inside the controller, and can be completed quickly without additional mechanical equipment. In addition, the compensation amplitude of the software to the control command can be very fine, so that the method can lead the deviation of the bottom dead center to be infinitely reduced, thereby greatly improving the precision of the bottom dead center.

After a plurality of stamping cycles, the lower limit error of the slide block can be reduced to zero, and when the error is increased due to the change of external conditions, curve compensation is carried out at any time to ensure that the bottom dead center of the slide block is equal to a desired value.

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

a feedback compensation method for bottom dead center deviation of a servo press,

Defining a motor position setting curve as theta_ai.e. the motor angle curve under ideal conditions;

Defining the curve of the motor after position compensation as theta_bNamely a motor position running command actually sent by a motor controller;

Defining the expected bottom dead center as h₁₂The bottom dead center actually reached by the slider is h₁₄；

The method comprises the following steps:

Step one, starting a stamping process, and detecting the actual value h of the bottom dead center of the slider at the kth time₁₄(k) Calculating the k-th actual value and the expected value h₁₂(k) Deviation value h of_e(k)

h_e(k)＝h₁₂-h₁₄(k)

step two, calculating a new motor position compensation value theta_c(k+1)

θ_c(k+1)＝θ_c(k)+G·h_e(k)

Wherein:

k is the number of stamping processes, and k is a natural number;

θ_c(k) Compensating the k-th motor position curve by using the compensation quantity, wherein when k is 1, theta_c(1)＝0；

G is the error magnification

The value range of r is 0.1-1.0

h_dThe position deviation of the sliding block caused by the deformation of the machine body at the bottom dead center when the press is loaded and operated;

θ_dThe rotating angle of the motor corresponding to the position deviation of the sliding block at the bottom dead center;

h_dAnd theta_dObtained by experimental measurement.

Step three, obtaining the latest compensation value theta through the step two_c(k +1) is used for compensating the servo motor position curve so as to obtain a latest compensated curve theta_b(k +1), i.e.

wherein: when k is 1

h₁₄(1)＝h₁₂

θ_b(1)＝θ_a

the invention has the beneficial effects that:

1. the error between the actual value and the expected value of the bottom dead center of the sliding block can be measured in each stamping process, and the position curve of the servo motor is automatically compensated by utilizing the feedback control principle. The compensation process is completed in software inside the controller, and can be completed quickly without additional mechanical equipment. In addition, the compensation amplitude of the software to the control command can be very fine, so that the method can lead the deviation of the bottom dead center to be infinitely reduced, thereby greatly improving the precision of the bottom dead center.

After a plurality of stamping cycles, the lower limit error of the slide block can be reduced to zero, and when the error is increased due to the change of external conditions, curve compensation is carried out at any time to ensure that the bottom dead center of the slide block is equal to a desired value.

Drawings

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

FIG. 2 is a diagram illustrating the operation of a compensation according to the present invention;

FIG. 3 is a block diagram of a servo press system of the present invention;

FIG. 4 is a detailed block diagram of the feedback compensation algorithm of the present invention;

Fig. 5 is a view showing a structure of a conventional servo press system.

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. 2, a method for compensating the bottom dead center deviation feedback of the servo press,

Defining a motor position setting curve as theta_aI.e. the motor angle curve under ideal conditions;

defining the curve of the motor after position compensation as theta_bI.e. the motor position run command actually issued by the motor controller.

Wherein the dotted line formed by the points 1-2-3 is a motor position setting curve calculated under an ideal condition without considering the interference such as deformation and abrasion of the press, and the solid line formed by the points 1-4-3 is a curve after the motor position compensation, i.e., an angle curve in which the motor actually operates.

The desired curve defining the position of the slider is h_aNamely, the theoretical running track of the position of the sliding block when the motor runs according to a set curve under the ideal condition;

defining the actual curve of the slide block position as h_bnamely the actual running track of the sliding block when the motor runs according to the compensated curve.

Wherein the dotted line formed by points 11-12-13 is the desired curve of the slide operation under ideal conditions without taking into account disturbances such as press deformation and wear, corresponding to the motor setting curve, and the solid line formed by points 11-14-13 is the actual operating curve of the slide position under consideration of press deformation and wear.

Defining the expected bottom dead center as h₁₂The bottom dead center actually reached by the slider is h₁₄I.e. the expectation that point 12 in fig. 2 is the bottom dead center of the sliderposition, corresponding to point 2; point 14 is the actual position of the bottom dead center of the slide and corresponds to point 4.

as shown in fig. 1, during a stamping operation, the motor operates according to a compensated curve. The compensation amount is zero when k is 1 in the first stamping process. In the return stroke process after the sliding block passes through the lower dead point in each stamping process, the control software calculates the compensation amount according to the deviation feedback compensation algorithm, calculates a new curve after compensation, and finally controls the servo motor to rotate according to the new curve after compensation. The measuring tool adopted by the invention is a grating scale, and the specific structure of the feedback compensation algorithm is shown in figure 4.

The method comprises the following steps:

Step one, starting a stamping process, and detecting the actual value h of the bottom dead center of the slider at the kth time₁₄(k) Calculating the k-th actual value and the expected value h₁₂(k) Deviation value h of_e(k) As shown in fig. 4, this process is calculated by the subtractor 1,

h_e(k)＝h₁₂-h₁₄(k)

step two, accumulating the newly calculated bottom dead center deviation and historical data by the integrator to obtain a new motor position compensation value theta_c(k +1), i.e.

θ_c(k+1)＝θ_c(k)+G·h_e(k)

The history data is θ_c(k)

wherein:

k is the number of stamping processes, and k is a natural number;

θ_c(k) compensating the k-th motor position curve by using the compensation quantity, wherein when k is 1, theta_c(1)＝0；

wherein G is the amplification factor of the integrator, and can be set through tests and estimated through parameters of a transmission mechanism of the press. The evaluation method is briefly described here. If the press machine works according to the full load condition, the press machine is taken

The value range of r is 0.1-1.0

h_dThe position deviation of the sliding block caused by the deformation of the machine body at the bottom dead center when the press is loaded and operated;

θ_dThe rotating angle of the motor corresponding to the position deviation of the sliding block at the bottom dead center;

h_dAnd theta_dObtained by experimental measurement.

The factor r is to reduce the integrator amplification because smaller amplification tends to stabilize the algorithm but extends the offset compensation time. The specific value can be further adjusted through experiments and balanced according to production requirements. The parameter G may remain constant for a certain type of press.

Step three, obtaining the latest compensation value theta through the step two_c(k +1) is used for compensating the servo motor position curve so as to obtain a latest compensated curve theta_b(k +1), i.e.

Wherein: when k is 1

h₁₄(1)＝h₁₂

θ_b(1)＝θ_a

Curve theta after compensation_bAnd (k +1) is temporarily stored in the control software and is sent to the servo driver as a motor operation control command in the next stamping period to control the rotation of the servo motor. The servo motor rotates according to the curve, and then pushes the sliding block to operate through the transmission mechanism. The bottom dead center of the slide for the new press cycle should be closer to the desired value and be able to completely eliminate the bottom dead center bias after several cycles.

The error between the actual value and the expected value of the bottom dead center of the sliding block can be measured in each stamping process, and the position curve of the servo motor is automatically compensated by utilizing the feedback control principle. The compensation process is completed in software inside the controller, and can be completed quickly without additional mechanical equipment. In addition, the compensation amplitude of the software to the control command can be very fine, so that the method can lead the deviation of the bottom dead center to be infinitely reduced, thereby greatly improving the precision of the bottom dead center.

after a plurality of stamping cycles, the lower limit error of the slide block can be reduced to zero, and when the error is increased due to the change of external conditions, curve compensation is carried out at any time to ensure that the bottom dead center of the slide block is equal to a desired value.

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.