CN-122014718-A - Hydraulic motor constant torque self-adaptive PID control system

CN122014718ACN 122014718 ACN122014718 ACN 122014718ACN-122014718-A

Abstract

The invention relates to the technical field of hydraulic control and discloses a constant torque self-adaptive PID control system of a hydraulic motor, which comprises a controller and a hydraulic driving unit, wherein the controller utilizes a signal preprocessing module to carry out frequency domain separation on a pressure signal, extracts an average pressure difference representing driving force and a ripple amplitude representing fluid stiffness, a state observation module estimates an instantaneous volume elastic modulus based on the ripple amplitude, corrects a compression term in a flow continuity model by utilizing the modulus and calculates an instantaneous leakage coefficient of the motor in real time, and the self-adaptive control module establishes dynamic mapping of PID gain and physical parameters, namely, utilizes the leakage coefficient to adjust proportional gain to match system damping, utilizes the volume elastic modulus to adjust integral gain to adapt to natural frequency and combines feedforward compensation to synthesize a control instruction. The invention effectively solves the problem of model mismatch caused by oil characteristic change and motor abrasion, and improves the control precision of the whole life cycle of the system.

Inventors

ZHONG YING
Wen Zuming
WANG PEIJUN
Gao Puwen
SONG LUYU
HU JI

Assignees

宁波欧易液压有限公司

Dates

Publication Date: 20260512
Application Date: 20260409

Claims (10)

1. The hydraulic motor constant torque self-adaptive PID control system is characterized by comprising a hydraulic drive hardware unit and a controller (100); the hydraulic drive hardware unit comprises a hydraulic pump (10), an electrohydraulic servo valve (20), a hydraulic motor (30), a load (40) and a sensor assembly for acquiring system state quantity; The controller (100) is logically divided into: The signal preprocessing module (110) is used for calculating an original differential pressure signal according to the acquired pressure signal, carrying out frequency domain separation on the original differential pressure signal, and decoupling and outputting an average differential pressure signal representing driving force and a ripple amplitude representing fluid stiffness; A state observation and identification module (120) for estimating an instantaneous bulk modulus of elasticity of the fluid based on the amplitude of the ripple, and correcting a flow continuity model in combination with the average differential pressure signal and the instantaneous bulk modulus, for observing an instantaneous leakage coefficient of the hydraulic motor (30) in real time; An adaptive control law calculation module (130) for establishing a dynamic mapping of PID gains to physical state parameters: And adjusting proportional gain by utilizing the instantaneous leakage coefficient, adjusting integral gain by utilizing the instantaneous volume elastic modulus, performing closed-loop feedback operation on deviation of a target differential pressure and the average differential pressure signal by utilizing the adjusted proportional gain and the adjusted integral gain, and combining a feedforward control instruction to synthesize a final control instruction to drive the electrohydraulic servo valve (20).
2. The hydraulic motor constant torque adaptive PID control system according to claim 1, wherein the sensor assembly comprises an oil inlet pressure sensor (50), an oil outlet pressure sensor (60), a rotational speed sensor (70) and a spool position sensor (80), wherein an outlet of the hydraulic pump (10) is connected to an oil inlet of the electrohydraulic servo valve (20), the electrohydraulic servo valve (20) is connected to an oil inlet and an oil outlet of the hydraulic motor (30), an output shaft of the hydraulic motor (30) is connected to the load (40), the oil inlet pressure sensor (50) and the oil outlet pressure sensor (60) are respectively mounted at the oil inlet and the oil outlet of the hydraulic motor (30), the rotational speed sensor (70) is mounted at the output shaft of the hydraulic motor (30), and the spool position sensor (80) is integrated inside the electrohydraulic servo valve (20).
3. The hydraulic motor constant torque adaptive PID control system of claim 2, characterized in that the signal preprocessing module (110) calculates the difference between the oil inlet pressure and the oil outlet pressure to obtain the raw differential pressure signal; the signal preprocessing module (110) comprises a low-frequency control channel and a high-frequency characteristic extraction channel; In the low frequency control channel, the signal preprocessing module (110) extracts the average differential pressure signal by using a low-pass filter with a cut-off frequency lower than the minimum fundamental frequency of the hydraulic pump (10); in the high-frequency characteristic extraction channel, the signal preprocessing module (110) calculates the flow pulsation fundamental frequency according to the rotating speed measured by the rotating speed sensor (70) and sets the flow pulsation fundamental frequency as the center frequency of a band-pass filter, and extracts the pressure ripple component from the original differential pressure signal and calculates the ripple amplitude.
4. The hydraulic motor constant torque adaptive PID control system according to claim 3, characterized in that the state observation and recognition module (120) comprises a bulk modulus correction unit (121); the volume elastic modulus correction unit (121) normalizes the ripple amplitude value by using a rotating speed signal; The volume elastic modulus correction unit (121) stores a reference ripple amplitude and calculates the instantaneous volume elastic modulus according to the mapping relation between the normalized ripple amplitude and the reference ripple amplitude; The volume elastic modulus correction unit (121) is further used for updating the reference ripple amplitude according to the actually measured ripple amplitude at the steady state of the system, and is used for compensating the abrasion of the pump source.
5. The hydraulic motor constant torque adaptive PID control system of claim 2, characterized in that the state observation and recognition module (120) further comprises a leakage coefficient observation unit (122); The leakage coefficient observation unit (122) calculates an estimated flow rate through the electro-hydraulic servo valve (20) based on data of the spool position sensor (80); -said leakage coefficient observing unit (122) subtracting from said estimated flow a theoretical volumetric flow of said hydraulic motor (30) and a fluid compression flow determined by said instantaneous bulk modulus of elasticity, obtaining a flow difference; the leakage coefficient observation unit (122) divides the flow difference value by the average differential pressure signal to calculate the instantaneous leakage coefficient.
6. The hydraulic motor constant torque adaptive PID control system according to claim 5, characterized in that the leakage coefficient observation unit (122) stores an effective observation threshold; Outputting the instantaneous leakage coefficient calculated in real time when the absolute value of the average differential pressure signal is higher than the effective observation threshold; and when the absolute value of the average differential pressure signal is lower than or equal to the effective observation threshold value, locking the instantaneous leakage coefficient at the last moment of output.
7. The hydraulic motor constant torque adaptive PID control system according to claim 1, characterized in that the adaptive control law calculation module (130) comprises a feed-forward calculation unit (131); -the feedforward calculation unit (131) calculates a theoretical target flow rate comprising a leakage compensation using the instantaneous leakage coefficient; The feedforward calculation unit (131) converts the theoretical target flow into a feedforward control instruction based on an electrohydraulic servo valve inverse model; in the inverse model operation, the feedforward calculation unit (131) stores a minimum differential pressure protection threshold, and when the valve port differential pressure is smaller than the minimum differential pressure protection threshold, the minimum differential pressure protection threshold is used for participating in denominator operation, so as to prevent the numerical value from overflowing.
8. The hydraulic motor constant torque adaptive PID control system of claim 7, characterized in that the adaptive control law calculation module (130) further comprises an adaptive PID feedback unit (132); The specific logic of the adaptive PID feedback unit (132) to perform the dynamic mapping is: setting a proportional gain and the instantaneous leakage coefficient to have a positive correlation; Setting integral gain and the instantaneous volume elastic modulus to have positive correlation; the adaptive PID feedback unit (132) calculates the deviation between the target differential pressure and the average differential pressure signal by using the regulated proportional gain and integral gain, and generates a feedback control instruction.
9. The hydraulic motor constant torque adaptive PID control system of claim 8, characterized in that the adaptive control law calculation module (130) superimposes the feedforward control command and the feedback control command and performs clipping processing according to the rated input range of the electrohydraulic servo valve (20) to generate a final control command.
10. The hydraulic motor constant torque adaptive PID control system of claim 1, characterized in that the controller (100) comprises a hardware timer and an analog-to-digital converter for synchronous trigger sampling of the sensor assembly; the front end of the analog-to-digital converter is connected with a hardware low-pass filter, and the cut-off frequency of the hardware low-pass filter is set to be higher than the flow pulsation frequency generated by the hydraulic pump (10) at the highest working rotation speed and is used for retaining the characteristic of the ripple amplitude value.

Description

Hydraulic motor constant torque self-adaptive PID control system Technical Field The invention relates to the technical field of hydraulic control, in particular to a constant torque self-adaptive PID control system of a hydraulic motor. Background The hydraulic motor constant torque control system is widely applied to engineering machinery winches, rotary driving mechanisms and industrial manufacturing equipment, and the control performance of the hydraulic motor constant torque control system is directly related to the stability and safety of operation. Such systems typically employ a closed-loop pressure control strategy that maintains a constant motor inlet-outlet pressure differential by adjusting the opening of the electro-hydraulic servo valve, thereby achieving precise control of the output torque. However, in actual conditions, the physical parameters of the hydraulic system are not constant. The bulk modulus of hydraulic oil (i.e. fluid stiffness) can change with the increase of the oil temperature or the mixing of air, but the existing control system design simplifies the hydraulic oil into a fixed constant, or the hydraulic oil can only be detected offline by adding a high-cost special oil quality sensor, and a low-cost online monitoring means is lacked, so that when the fluid characteristics change, the control model preset by the system is mismatched. In addition, during long-term operation of the hydraulic motor, wear of its internal kinematic pairs can lead to a gradual increase in the leakage coefficient. While the prior art attempts to estimate leakage through flow observers, the impact of fluid compressibility on transient flow balance was ignored in the calculation process, simply attributing the flow differences entirely to leakage. Under the unsteady state working condition that the system pressure changes rapidly, the flow for compressing the fluid volume is not negligible, and the simplification treatment can lead to the identification result of the leakage coefficient to have larger deviation. Because of the lack of accurate perception of the physical states such as the fluid stiffness and the leakage coefficient, the traditional PID controller adopts fixed gain parameters, or carries out surface layer adjustment only according to error statistical characteristics, and cannot adapt to the changes of the damping characteristics and the natural frequency of the system in a physical mechanism. The control system has the problems of reduced response bandwidth, increased overshoot or deteriorated steady-state precision when facing motor wear or fluctuation of oil liquid state, and the like, and is difficult to maintain consistent control performance in the whole life cycle of the equipment. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a constant torque self-adaptive PID control system of a hydraulic motor, which solves the problems that the control parameters cannot adapt to the physical characteristic change of the system and further the control precision of the system is reduced and the dynamic response is unstable in the whole life cycle because the change of the fluid volume elastic modulus cannot be monitored on line with low cost and the interference of the compressibility of the stripping fluid on leakage identification is difficult in the prior art. In order to achieve the above purpose, the invention is realized by the following technical scheme: The invention provides a hydraulic motor constant torque self-adaptive PID control system, which comprises a hydraulic drive hardware unit and a controller. The hydraulic drive hardware unit comprises a hydraulic pump, an electrohydraulic servo valve, a hydraulic motor, a load, an oil inlet pressure sensor, an oil outlet pressure sensor, a rotating speed sensor and a valve core position sensor, wherein the oil inlet pressure sensor, the oil outlet pressure sensor, the rotating speed sensor and the valve core position sensor are used for acquiring system state quantity. The controller is logically divided into a signal preprocessing module, a state observation and identification module and an adaptive control law calculation module. The signal preprocessing module is used for performing signal characteristic decoupling, calculating an original differential pressure signal according to the collected pressure signal, performing frequency domain separation on the original differential pressure signal, and respectively outputting an average differential pressure signal representing driving force and a ripple amplitude representing fluid stiffness. The state observation and identification module is used for performing cascading observation of multiple physical field parameters, estimating the instantaneous volume elastic modulus of the fluid based on the ripple amplitude value, correcting a fluid compression term in a flow continuity model by utilizing the instantaneous volume elastic modulus, and fur