Hydraulic Pump Displacement Control With Predictive Constraint Tuning
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Solution Overview
Problem
The deviation between actual and targeted displacement of the hydraulic pump affects the accuracy of control of hydraulic actuators, impacting the work performance of work machines.
Innovation Solution
A control system for hydraulic pumps that includes a displacement control unit, a displacement sensor, and a controller using a mathematical model to predict and optimize displacement control, incorporating constraints on control inputs to improve responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional displacement control is used for the hydraulic pump, then the control system is simple, but the responsiveness of displacement control is slow
Solution Approach 1:
The controller stores a mathematical model predicting pump displacement characteristics in advance. Before actual displacement control occurs, the controller uses this pre-stored model to predict future displacement values and compute optimal control inputs that anticipate system behavior, thereby improving responsiveness without adding complex hardware
Solution Approach 2:
The controller acquires the actual displacement value from the displacement sensor and feeds it back to compare with the predicted displacement value. Based on this feedback and the evaluation value computed from the deviation, the controller adjusts the control input to minimize displacement error, achieving rapid and accurate displacement tracking
2Productivity
If the displacement of the hydraulic pump is changed rapidly, then the work performance improves, but the deviation between actual and targeted displacement increases
Solution Approach 1:
The controller uses the stored mathematical model to predict future pump displacement values before actual control actions are taken. By computing optimal control inputs based on predicted values and constraints, the system can rapidly change displacement while maintaining accuracy, as the predictive model anticipates how rapid changes will affect actual displacement
Solution Approach 2:
The controller continuously monitors the deviation between actual and targeted displacement through the displacement sensor. Based on this feedback and the evaluation value, the controller adjusts control inputs in real-time to correct any deviation, enabling rapid displacement changes while maintaining precision through continuous correction
Data Source
AI summary
A control system of a work machine includes a hydraulic pump that is rotationally driven by a prime mover and supplies hydraulic operating oil to a hydraulic actuator, a displacement control unit that controls the displacement of the hydraulic pump according to a control input, a displacement sensor that senses a displacement actual measured value of the hydraulic pump, and a controller that acquires a displacement target value of the hydraulic pump and outputs the control input according to the displacement target value to the displacement control unit. A mathematical model for predicting the displacement of the hydraulic pump is stored in the controller. The controller computes a displacement predicted value of the hydraulic pump by using the mathematical model and computes the optimum control input on the basis of the displacement predicted value and a constraint on the control input. The controller computes an evaluation value on the basis of the displacement target value and the displacement actual measured value and changes the constraint on the control input depending on the evaluation value.