Hydraulic Pump Displacement Control for Faster Actuator Response
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Solution Overview
Problem
A deviation between the actual displacement and the targeted displacement of the hydraulic pump affects the accuracy of control of a hydraulic actuator, which in turn impacts the work performance of a work machine. Therefore, it is essential to enhance the responsiveness of displacement control for the hydraulic pump.
Innovation Solution
A control system for a work machine that includes a hydraulic pump, a displacement control unit, a displacement sensor, and a controller. The controller uses a mathematical model to predict the pump's displacement and computes an optimum control input based on the predicted value and constraints, adjusting these constraints based on an evaluation value derived from the displacement target and actual measured values.
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, enabling proactive adjustment of control inputs to achieve faster responsiveness without adding complex hardware components.
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 from the mathematical model. Based on the deviation between actual and predicted values, the controller adjusts the control input to minimize tracking error, thereby improving responsiveness while maintaining a relatively simple control structure.
2Speed
If the displacement control is made more responsive, then the work performance improves, but the control precision may be compromised
Solution Approach 1:
The controller continuously acquires actual displacement values from the displacement sensor and compares them with predicted values from the mathematical model. This feedback mechanism enables real-time correction of control inputs, ensuring that rapid displacement changes maintain high precision by constantly minimizing the deviation between actual and target displacement values.
Solution Approach 2:
The controller changes the control input parameters dynamically based on the deviation between actual and predicted displacement values. By adjusting control parameters in real-time according to the system's actual state, the controller achieves both rapid responsiveness and high precision in displacement control.
Data Source
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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.