阅读说明：本技术 一种基于参数自适应的液压系统控制方法 (Hydraulic system control method based on parameter self-adaptation ) 是由 李铁军 李赛雷 杨冬 蒙磊 李勇斌 于 2020-11-27 设计创作，主要内容包括：本发明公开了一种基于参数自适应的液压系统控制方法,涉及液压系统控制技术领域,包括以下步骤：预先获取实际关节位置,并标定期望关节位置θ；基于位置误差值e和位置误差变化ec的参数模糊自整定PID控制,其中包括标定误差值e和标定位置误差变化ec为输入,获取k-p、k-i和k-d为输出参数；基于伺服放大器和电液伺服阀进行控制。本发明具有模糊控制的鲁棒性和PID控制削弱稳态误差的性能,用模糊控制规则实现对PID参数的自动调节,其在大偏差范围内采用模糊控制,而在小偏差范围内转换成PID控制,两者的转换根据给定的偏差阈值自动实现,不仅复合控制具有更小的超调,而且在关节位置控制方面明显具有更高的控制精度。(The invention discloses a hydraulic system control method based on parameter self-adaptation, which relates to the technical field of hydraulic system control and comprises the following steps: acquiring an actual joint position in advance, and calibrating an expected joint position theta; parameter fuzzy self-tuning PID control based on position error value e and position error change ec, wherein the position error value e and the position error change ec are taken as input, and k is obtained p 、k i And k d Is an output parameter; the control is based on a servo amplifier and an electro-hydraulic servo valve. The invention has the robustness of fuzzy control and the performance of PID control for weakening steady-state error, realizes the automatic regulation of PID parameters by using the fuzzy control rule, and adopts the fuzzy control in a large deviation rangeAnd the system is converted into PID control in a small deviation range, and the conversion of the PID control and the PID control is automatically realized according to a given deviation threshold value, so that the composite control has smaller overshoot and obviously has higher control precision in the aspect of joint position control.)

1. A hydraulic system control method based on parameter self-adaptation is characterized by comprising the following steps:

acquiring an actual joint position in advance, and calibrating an expected joint position theta;

parameter fuzzy self-tuning PID control based on position error value e and position error change ec, wherein the position error value e and the position error change ec are taken as input, and k is obtained_p、k_iAnd k_dIs an output parameter;

the control is based on a servo amplifier and an electro-hydraulic servo valve.

2. The parameter adaptive-based hydraulic system control method according to claim 1, wherein the step of pre-acquiring actual joint positions includes measuring angles of the respective joints in real time by an angle encoder.

3. The parameter adaptive-based hydraulic system control method of claim 2, further comprising a range of motion of joint angles, expressed as:

4. the parameter adaptive-based hydraulic system control method according to claim 3, wherein the range of motion of the joint angle is 0 ° to 40 °.

5. The parameter adaptive-based hydraulic system control method of claim 1, wherein the step of PID controlling includes: the output of the incremental PID algorithm is the input voltage U of the servo amplifier_vExpressed as:

U_v＝U_v(i-1)+k_p[e(i)-e(i-1)]+k_ie(i)+k_d[e(i)-2e(i-1)+e(i-2)]；

wherein i is the number of times of control, k_p、k_iAnd k_dThe control parameters are PID controlled.

6. The parameter adaptive-based hydraulic system control method of claim 1, wherein the electro-hydraulic servo valve further comprises: the flow rate of the electro-hydraulic servo valve is obtained and is expressed as:

Q＝K_vI_v-K_cp_L；

wherein Q is the load flow of two hydraulic cylinders, K_vIs the flow gain of two servovalves, I_vFor the output current of the servo amplifier, K_cIs the flow pressure coefficient, p, of the servo valve_LIs the load pressure of the hydraulic cylinder.

7. The parameter adaptive-based hydraulic system control method of claim 1, further comprising controlling joints to track sinusoidal trajectories represented as: θ ═ 5sin (0.2 π t) + 15.

Technical Field

The invention relates to the technical field of hydraulic system control, in particular to a hydraulic system control method based on parameter self-adaption.

Background

The main driving modes of the industrial robot comprise motor driving, air pressure driving and hydraulic driving. The pneumatic drive has the defects of large bearing capacity, low cost, large elastic modulus of gas, easy rigidity reduction in working and low control precision. The motor is simple to drive and control, has high control precision, and has the defects of low power density, poor electromagnetic interference resistance and the like. The electro-hydraulic servo system has good control performance, has the advantages of high response, high precision, high power, high system rigidity, strong anti-interference capability and the like, and has better application in the fields of aerospace, mines, metallurgy, civil use, ship water conservancy and the like. The hydraulic servo system can form a servo system with compact structure, small volume, light weight and good acceleration performance, and consists of an electric signal processing device and a plurality of hydraulic elements, and the dynamic performance of each element is influenced mutually, so that the dynamic performance of each element is complex. Scholars at home and abroad have conducted various researches on the position control aspect of a hydraulic robot, a main control element of a hydraulic servo system is an electro-hydraulic servo valve, and the electro-hydraulic servo valve has the characteristics of dead zones, zero drift, asymmetric zero positions, hysteresis loops and the like, so that the high nonlinearity of the hydraulic servo system is caused.

The patent CN103562568B of the invention discloses a hydraulic system for engineering machinery. This hydraulic system includes: a hydraulic actuator and a first hydraulic machine for supplying fluid to the hydraulic actuator. The hydraulic system further includes: a hydraulic transformer for supplying fluid to the hydraulic actuator in parallel with the first hydraulic machine; and an accumulator for the fluid. The hydraulic transformer includes a first port and a second port, and the transformer is adapted to transform a first pressure and a first flow at the first port to a second pressure and a second flow at the second port. The second port of the hydraulic transformer is in fluid communication with the hydraulic actuator, and the first port is in communication with the accumulator. But the characteristics of dead zones, zero drift, asymmetric zero positions, hysteresis loops and the like of the electro-hydraulic servo valve exist, so that the high nonlinearity of the hydraulic servo system is caused.

An effective solution to the problems in the related art has not been proposed yet.

Disclosure of Invention

Aiming at the problems in the related technology, the invention provides a hydraulic system control method based on parameter self-adaptation, which is used for realizing the compensation of dead zone and null shift problems existing in an electro-hydraulic servo valve, combines fuzzy control and a traditional PID algorithm, enables a controller to have the robustness of the fuzzy control and the performance of PID control for weakening steady-state error, realizes the automatic regulation of PID parameters by using a fuzzy control rule, adopts the fuzzy control in a large deviation range, and converts the fuzzy control into the PID control in a small deviation range, and the conversion of the fuzzy control and the PID control is automatically realized according to a given deviation threshold value, so that the composite control has smaller overshoot, and obviously has higher control precision in the aspect of joint position control, thereby overcoming the technical problems existing in the prior related technology.

The technical scheme of the invention is realized as follows:

a hydraulic system control method based on parameter self-adaptation comprises the following steps:

step S1, acquiring the actual joint position in advance, and calibrating the expected joint position theta;

step S2, based on the position error value e and the parameter fuzzy self-tuning PID control of the position error change ec, wherein the position error value e and the position error change ec are taken as the input, k is obtained_p、k_iAnd k_dIs an output parameter;

in step S3, control is performed based on the servo amplifier and the electro-hydraulic servo valve.

Further, the step of acquiring the actual joint positions in advance comprises measuring the angles of the joints in real time by an angle encoder.

Further, the range of motion of the joint angle is also included, and is represented as:

further, the range of motion of the joint angle is 0 to 40 °.

Further, the step of PID control includes: the output of the incremental PID algorithm is the input voltage U of the servo amplifier_vExpressed as:

U_v＝U_v(i_1)+k_p[e(i)_e(i_1)]+k_ie(i)+k_d[e(i)_2e(i_1)+e(i_2)]；

wherein i is the number of times of control, k_p、k_iAnd k_dThe control parameters are PID controlled.

Further, the electro-hydraulic servo valve further includes: the flow rate of the electro-hydraulic servo valve is obtained and is expressed as:

Q＝K_vI_v-K_cp_L；

wherein Q is the load flow of two hydraulic cylinders, K_vIs the flow gain of two servovalves, I_vFor the output current of the servo amplifier, K_cIs the flow pressure coefficient, p, of the servo valve_LIs the load pressure of the hydraulic cylinder.

Further, the method also comprises controlling the joints to track the sinusoidal tracks, and is represented as: θ ═ 5sin (0.2 π t) + 15.

The invention has the beneficial effects that:

the invention relates to a hydraulic system control method based on parameter self-adaptation, which is characterized in that by acquiring the actual joint position in advance, and calibrating the expected joint position theta, based on the parameter fuzzy self-tuning PID control of the position error value e and the position error change ec, the controller is controlled based on the servo amplifier and the electro-hydraulic servo valve to realize the compensation of the dead zone and the null shift problem of the electro-hydraulic servo valve, combines the fuzzy control with the traditional PID algorithm, leads the controller to have the robustness of the fuzzy control and the performance of the PID control for weakening the steady-state error, realizes the automatic adjustment of the PID parameters by the fuzzy control rule, the fuzzy control is adopted in a large deviation range, the PID control is converted in a small deviation range, the conversion of the fuzzy control and the PID control is automatically realized according to a given deviation threshold value, the composite control has smaller overshoot, and the control precision is obviously higher in the aspect of joint position control.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 is a first flowchart illustrating a method for controlling a hydraulic system based on parameter adaptation according to an embodiment of the present invention;

FIG. 2 is a second flowchart illustrating a method for controlling a hydraulic system based on parameter adaptation according to an embodiment of the present invention;

FIG. 3 is a first schematic diagram of a trajectory tracking curve of a hydraulic system control method based on parameter adaptation according to an embodiment of the present invention;

fig. 4 is a schematic diagram of a trajectory tracking curve of a hydraulic system control method based on parameter adaptation according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments that can be derived by one of ordinary skill in the art from the embodiments given herein are intended to be within the scope of the present invention.

According to an embodiment of the invention, a hydraulic system control method based on parameter adaptation is provided.

As shown in fig. 1-2, the method for controlling a hydraulic system based on parameter adaptation according to an embodiment of the present invention includes the following steps:

acquiring an actual joint position in advance, and calibrating an expected joint position theta;

location basedObtaining k through parameter fuzzy self-tuning PID control of error value e and position error change ec, wherein the error value e and the position error change ec are input to obtain_p、k_iAnd k_dIs an output parameter;

the control is based on a servo amplifier and an electro-hydraulic servo valve.

And the step of acquiring the actual joint positions in advance comprises the step of measuring the angles of all joints in real time by an angle encoder.

Wherein, still include the motion range of joint angle, show as:

wherein the range of motion of the joint angle is 0-40 °.

Wherein the step of PID control includes: the output of the incremental PID algorithm is the input voltage U of the servo amplifier_vExpressed as:

U_v＝U_v(i_1)+k_p[e(i)_e(i_1)]+k_ie(i)+k_d[e(i)_2e(i_1)+e(i_2)]；

wherein i is the number of times of control, k_p、k_iAnd k_dThe control parameters are PID controlled.

Wherein, the electro-hydraulic servo valve still includes: the flow rate of the electro-hydraulic servo valve is obtained and is expressed as:

Q＝K_vI_v-K_cp_L；

wherein Q is the load flow of two hydraulic cylinders, K_vIs the flow gain of two servovalves, I_vFor the output current of the servo amplifier, K_cIs the flow pressure coefficient, p, of the servo valve_LIs the load pressure of the hydraulic cylinder.

By means of the technical scheme, the actual joint position is obtained in advance, the expected joint position theta is calibrated, parameter fuzzy self-tuning PID control based on the position error value e and the position error change ec is realized, control is performed based on a servo amplifier and an electro-hydraulic servo valve, the dead zone and null shift problems existing in the electro-hydraulic servo valve are compensated, fuzzy control and a traditional PID algorithm are combined, the controller has robustness of the fuzzy control and performance of the PID control for weakening steady-state errors, automatic regulation of PID parameters is realized by using a fuzzy control rule, the PID parameters are converted into PID control in a small deviation range, conversion of the fuzzy control and the PID control is automatically realized according to a given deviation threshold value, composite control has smaller overshoot, and obviously has higher control precision in the aspect of joint position control.

In addition, specifically, the hydraulic cylinder is driven by the pressure of hydraulic oil, the hydraulic oil flows into the hydraulic cylinder from the outlet of the electro-hydraulic servo valve, during the driving process, the hydraulic cylinder is used as an execution element to push the load to move rapidly, and the flow continuity of the hydraulic cylinder is represented as:

wherein Q₁、Q₂Respectively the flow of oil inlet and outlet of the hydraulic cylinder, A₁、A₂Areas of the rod chamber and rodless chamber of the hydraulic cylinder, respectively, C_ip、C_epRespectively the internal and external leakage coefficients, p, of the hydraulic cylinder₁、p₂Pressure, V, in the rod chamber and rodless chamber of the hydraulic cylinder, respectively₁、V₂Total volume of the rod-containing and rodless cavities, respectively, beta_eIs the effective bulk modulus of the hydraulic oil.

In addition, specifically, as shown in fig. 3-4, in one embodiment, the position of the single-joint experimental platform is controlled by using a fuzzy PID algorithm and a conventional PID algorithm, respectively. In the experiment, the traditional PID parameters are obtained as the better control parameters determined after continuous experiments, and the control parameters of the fuzzy PID algorithm are limited to fluctuate within an equidistant range by taking the traditional PID algorithm as the center in order to compare the control precision of the fuzzy PID algorithm and the traditional PID algorithm. Considering the dynamic response frequency of the servo valve, the sampling frequency and the control frequency are both 100Hz in the experimental process, and knowing the environmental constraint, the control joint is controlled to track the sinusoidal track (unit degree) in order to avoid the occurrence of position interference: θ ═ 5sin (0.2 π t) + 15.

In order to quantify the position control accuracy of the two control methods and analyze joint dynamic response, the average tracking error is defined as:

wherein N is the total number of data. In the trajectory tracking experiment, the maximum position error is reduced from 5.2731 degrees to 2.9234 degrees, and the position average tracking error is reduced from 2.8135 degrees to 1.4542 degrees. The experimental data can show that the position tracking effect of the fuzzy PID algorithm is obviously superior to that of the traditional PID algorithm in the joint tracking effect, and the tracking rapidity and accuracy of the fuzzy PID controller are much higher than those of the traditional PID controller in the track tracking process.

In conclusion, by means of the technical scheme of the invention, through acquiring the actual joint position in advance, and calibrating the expected joint position theta, based on the parameter fuzzy self-tuning PID control of the position error value e and the position error change ec, the controller is controlled based on the servo amplifier and the electro-hydraulic servo valve to realize the compensation of the dead zone and the null shift problem of the electro-hydraulic servo valve, combines the fuzzy control with the traditional PID algorithm, leads the controller to have the robustness of the fuzzy control and the performance of the PID control for weakening the steady-state error, realizes the automatic adjustment of the PID parameters by the fuzzy control rule, the fuzzy control is adopted in a large deviation range, the PID control is converted in a small deviation range, the conversion of the fuzzy control and the PID control is automatically realized according to a given deviation threshold value, the composite control has smaller overshoot, and the control precision is obviously higher in the aspect of joint position control.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.