CN-121719813-B - High-precision servo closed-loop control system for hydraulic micro-actuator

CN121719813BCN 121719813 BCN121719813 BCN 121719813BCN-121719813-B

Abstract

The invention discloses a high-precision servo closed-loop control system for a hydraulic micro actuator, which relates to the technical field of hydraulic driving and comprises a compliance calculation module, a saturation parameter determination module, a seal judgment module and a command pressure calculation module, wherein the compliance calculation module is used for calculating first static apparent compliance and second static apparent compliance of a main oil cavity, the saturation parameter determination module is used for determining saturation compliance and saturation pressure of the main oil cavity according to the first static apparent compliance and the second static apparent compliance, the seal judgment module is used for carrying out seal formation judgment on a slit communication port between an annular blind cavity and the main oil cavity according to the saturation compliance and the saturation pressure, and the command pressure calculation module is used for calculating command pressure of the main oil cavity according to a judgment result of seal formation judgment. The invention can improve the response stability of the system under the change of the tiny target displacement.

Inventors

ZHU YIHAN
DAI CHANGMING
Lv Huajian

Assignees

山东星辉液压设备有限公司

Dates

Publication Date: 20260505
Application Date: 20260224

Claims (6)

1. The high-precision servo closed-loop control system for the hydraulic micro actuator comprises a compliance calculation module, a saturation parameter determination module and a control module, wherein the compliance calculation module is used for calculating first static apparent compliance and second static apparent compliance of a main oil cavity; the specific steps of calculating the first static apparent compliance and the second static apparent compliance of the main oil cavity are as follows: positioning a main oil cavity between an actuating mechanism of the bellows and a pressure output port of the servo valve; generating a first pressure variation of the main oil cavity and a first steady-state displacement variation of the end part of the corrugated pipe; Adding a first grade of superposition to the minimum controllable pressure amplitude of the target servo control system to obtain a second small-amplitude pressure; performing secondary small-amplitude pressure stepping on the main oil cavity according to the secondary small-amplitude pressure until the internal pressure change of the main oil cavity tends to be stable and the end displacement of the corrugated pipe reaches a steady state; After the steady-state process of the second small-amplitude pressure stepping is finished, recording the second pressure variation of the main oil cavity and the second steady-state displacement variation of the end part of the corrugated pipe; Dividing the product of the equivalent pressure receiving area of the corrugated pipe and the first steady-state displacement variation by the first pressure variation to obtain a first static apparent compliance of the main oil cavity; dividing the product of the equivalent pressure receiving area of the corrugated pipe and the second steady-state displacement variation by the second pressure variation to obtain a second static apparent compliance of the main oil cavity; The second static apparent compliance of the main oil cavity is the steady-state displacement response quantity of the end part of the bellows caused by the unit pressure change under the second small-amplitude pressure stepping steady-state of the main oil cavity, and reflects the equivalent compliance characteristic of the main oil cavity under a higher pressure interval; the specific steps for determining the saturation compliance and saturation pressure of the main oil cavity are as follows: Defining a closed annular space between the bellows and a housing shoulder in the actuating structure as an annular blind cavity; Judging whether the annular blind cavity is in a rolled state or not according to the first static apparent compliance and the second static apparent compliance; if the annular blind cavity is in a rolled state, gradually lifting and pressing the main oil cavity according to the minimum controllable pressure amplitude, and calculating the static apparent compliance of the pressure level of the main oil cavity under each pressure level; performing difference calculation on static apparent compliance of two adjacent pressure stages to obtain compliance increment; If the compliance increment is larger than a preset minimum distinguishable compliance variable quantity, continuously carrying out step-by-step pressure lifting on the main oil cavity, otherwise, stopping pressure lifting on the main oil cavity, defining the static apparent compliance of the main oil cavity at the current pressure level as the saturation compliance of the main oil cavity, and defining the actual pressure value of the main oil cavity at the current pressure level as the saturation pressure of the main oil cavity; the saturation compliance of the main oil cavity is the static apparent compliance of the main oil cavity under the pressure level when the compliance increment is smaller than or equal to the minimum distinguishable compliance variable quantity in the gradual pressure raising process, and represents that the compression characteristic of the system tends to be stable and the annular blind cavity does not participate in volume change any more; The seal judging module is used for judging the seal formation of the slit communication port between the annular blind cavity and the main oil cavity according to saturation compliance and saturation pressure; The command pressure calculation module is used for calculating the command pressure of the main oil cavity according to the judging result of the seal formation judgment; the fluid blocking judging module is used for effectively blocking and judging the fluid communication between the main oil cavity and the annular blind cavity based on the command pressure; And the control parameter optimization module is used for carrying out feedback optimization on the control parameters of the target servo control system according to the judging result of the effective blocking judgment.
2. The high-precision servo closed-loop control system for a hydraulic micro-actuator according to claim 1, wherein generating a first pressure variation of the main oil chamber and a first steady-state displacement variation of the bellows end portion comprises: Performing a first small-amplitude pressure step on the main oil cavity based on the minimum controllable pressure amplitude of the target servo control system until the internal pressure change of the main oil cavity tends to be stable and the end displacement of the bellows reaches a steady state; and after the steady-state process of the first small-amplitude pressure stepping is finished, recording the first pressure change quantity of the main oil cavity and the first steady-state displacement change quantity of the end part of the corrugated pipe.
3. The high-precision servo closed-loop control system for a hydraulic micro-actuator according to claim 1, wherein the determination of the seal formation of the slit communication port between the annular blind cavity and the main oil cavity according to the saturation compliance and the saturation pressure comprises: carrying out single pressure level difference fallback on the saturated pressure according to the minimum controllable pressure amplitude; after the single pressure level difference is fallen back, carrying out single small-amplitude pressure stepping on the main oil cavity to obtain the post-return-pressure compliance of the main oil cavity; calculating the difference value between the post-back-pressure compliance and the saturation compliance to obtain a back-pressure stage compliance difference value; And judging whether a slit communication port between the annular blind cavity and the main oil cavity forms a seal or not according to the absolute value of the compliance difference value in the back pressure stage and the preset minimum distinguishable compliance variable quantity.
4. The high-precision servo closed-loop control system for a hydraulic micro-actuator according to claim 1, wherein calculating the command pressure of the main oil chamber based on the determination result of the seal formation determination comprises: if the judgment result of the seal forming judgment is that the slit communication port forms a seal, defining the current pressure value of the main oil cavity as the seal pressure of the main oil cavity; Performing difference value calculation on the target displacement of the end part of the corrugated pipe and the actually measured displacement of the end part of the corrugated pipe to obtain a displacement error; Calculating the ratio of the equivalent pressure area of the corrugated pipe to the nominal bulk modulus of the actuating mechanism to obtain a static conversion coefficient; multiplying the static conversion coefficient by the displacement error to obtain a static pressure difference compensation quantity; and adding the static pressure difference compensation quantity and the sealing pressure to obtain the command pressure of the main oil cavity.
5. The high-precision servo closed-loop control system for a hydraulic micro-actuator according to claim 1, wherein the effective blocking determination of the fluid communication between the main oil chamber and the annular blind chamber based on the command pressure comprises: Carrying out single pressure level difference fallback on the command pressure of the main oil cavity according to the minimum controllable pressure amplitude, and recording static apparent compliance after fallback of the main oil cavity; Performing pressure recovery on the main oil cavity according to the command pressure, and recording static apparent compliance of the main oil cavity after recovery; Performing difference value calculation on the static apparent compliance after falling and the static apparent compliance after recovering to obtain the compliance deviation in the falling-recovering stage; If the absolute value of the fall-back-recovery stage compliance deviation is smaller than or equal to the preset minimum distinguishable compliance variation, judging that the fluid communication between the main oil cavity and the annular blind cavity is effectively blocked.
6. The high-precision servo closed-loop control system for a hydraulic micro-actuator according to claim 1, wherein the feedback optimization of the control parameters of the target servo control system according to the judgment result of the effective blocking judgment comprises: If the judgment result of the effective blocking judgment is that the fluid communication between the main oil cavity and the annular blind cavity is blocked effectively, the control parameters of the target servo control system are kept unchanged; If the judgment result of the effective blocking judgment is that the fluid communication between the main oil cavity and the annular blind cavity is not blocked effectively, the minimum controllable pressure amplitude is reduced and adjusted to obtain an adjusted pressure amplitude, and the update command pressure of the main oil cavity is calculated according to the adjusted pressure amplitude.

Description

High-precision servo closed-loop control system for hydraulic micro-actuator Technical Field The invention relates to the technical field of hydraulic drive, in particular to a high-precision servo closed-loop control system for a hydraulic micro-actuator. Background Currently, the hydraulic driving system is widely applied to high-precision actuating mechanism scenes, and particularly has irreplaceable advantages in position control tasks with strict requirements, such as aerospace, precision optics, inertial navigation, micro-displacement control and the like. In such systems, a bellows structure is employed as the hydraulic micro-actuator of the main execution unit, which achieves a fine axial displacement output by adjusting the main oil chamber pressure. However, due to manufacturing structure limitations, the root of the bellows generally surrounds and forms an annular blind cavity, the blind cavity and the main oil cavity are kept in weak fluid connection through a slit communication port, and residual gas-liquid mixture in the area is easily involved in the response of the main oil cavity in the initial oil filling, pressure increasing and inching control process of the system, so that the rigidity, stability and servo accuracy of the system are affected. Especially in the high-precision closed-loop control process, the uncontrollable compression behavior of the annular blind cavity can introduce micro drift, hysteresis and even steady-state errors, so that zero point offset and response of the control system are degraded. In the prior art, modes of high-pressure standing, vacuum pre-exhausting or structural adhesive sealing and filling during initial filling are mostly adopted to try to avoid the problem of blind cavity residual gas, but the methods cannot dynamically identify the blind cavity state and monitor whether the blind cavity state is in fluid exchange with the main oil cavity again at the later period of system operation. Meanwhile, the stability of the seal is difficult to quantitatively evaluate, the change condition of the blind cavity cannot be effectively responded in the control logic, an unexpected error is generated in the micro-motion or holding stage of the whole servo system, and the application of the high-precision hydraulic actuating mechanism in the ultra-precision field is limited. Disclosure of Invention The invention aims to solve the defects that the stability of a seal in the prior art is difficult to quantitatively evaluate, the change condition of a blind cavity cannot be effectively responded in control logic, and an unexpected error is generated in a micro-motion or holding stage of the whole servo system. In order to solve the problems existing in the prior art, the invention adopts the following technical scheme: A high precision servo closed loop control system for a hydraulic micro-actuator, comprising: The compliance calculation module is used for calculating the first static apparent compliance and the second static apparent compliance of the main oil cavity; The saturation parameter determining module is used for determining the saturation compliance and the saturation pressure of the main oil cavity according to the first static apparent compliance and the second static apparent compliance; The seal judging module is used for judging the seal formation of the slit communication port between the annular blind cavity and the main oil cavity according to saturation compliance and saturation pressure; The command pressure calculation module is used for calculating the command pressure of the main oil cavity according to the judging result of the seal formation judgment; the fluid blocking judging module is used for effectively blocking and judging the fluid communication between the main oil cavity and the annular blind cavity based on the command pressure; And the control parameter optimization module is used for carrying out feedback optimization on the control parameters of the target servo control system according to the judging result of the effective blocking judgment. Preferably, calculating the first static apparent compliance and the second static apparent compliance of the main oil chamber includes: positioning a main oil cavity between an actuating mechanism of the bellows and a pressure output port of the servo valve; generating a first pressure variation of the main oil cavity and a first steady-state displacement variation of the end part of the corrugated pipe; Adding a first grade of superposition to the minimum controllable pressure amplitude of the target servo control system to obtain a second small-amplitude pressure; performing secondary small-amplitude pressure stepping on the main oil cavity according to the secondary small-amplitude pressure until the internal pressure change of the main oil cavity tends to be stable and the end displacement of the corrugated pipe reaches a steady state; After the steady-state process of the second smal