Hydrostatic Drive Gear Ratio Transition Control
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Solution Overview
Problem
Hydrostatic drive systems in machines experience jerking or lugging during quick direction, speed, or torque changes, leading to reduced efficiency and operator discomfort due to the inability to smoothly transition between gear ratios.
Innovation Solution
A control method that determines a gear ratio rate of change and defines an overlap range within which the displacements of the variable displacement pump and motor are simultaneously changed, and outside of which they are sequentially changed, using electronic signals to manage the transition smoothly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the operator commands the hydrostatic drive system to accelerate, decelerate, or change directions quickly, then the responsiveness of the system is improved, but the machine may jerk or lug
Solution Approach 1:
The displacement change process is segmented into multiple stages: initial rapid displacement change for quick responsiveness, followed by overlapping displacement adjustments of pump and motor to maintain smooth operation. This segmentation allows the system to achieve both quick response and smooth transitions by dividing the control process into distinct phases with different control strategies.
Solution Approach 2:
The system performs preliminary action by pre-calculating and preparing displacement adjustments before the actual gear ratio change is commanded. The controller determines the required displacement changes in advance and executes them in a coordinated manner, ensuring that the system is ready for quick transitions while maintaining smooth operation throughout the transition process.
2Productivity
If the operator commands quick transitions in direction, speed, and torque, then the efficiency in performance of the work cycle is improved, but the machine may jerk or lug
Solution Approach 1:
The control system dynamically adjusts the displacement of both the pump and motor during gear ratio transitions. Rather than using fixed sequential control, the system continuously monitors operating conditions and dynamically coordinates displacement changes to achieve both quick responsiveness and smooth transitions, thereby maintaining high productivity without jerking or lugging.
Solution Approach 2:
The system employs feedback control by continuously monitoring the actual gear ratio, pump displacement, and motor displacement during transitions. The controller uses this feedback information to adjust the displacement changes in real-time, ensuring that the transitions remain smooth even when quick responsiveness is required for improved work cycle efficiency.
3Speed
If the hydrostatic drive system components are made capable of quick transitions, then the responsiveness is improved, but the machine may jerk or lug
Solution Approach 1:
The patent merges the control of pump displacement and motor displacement into a coordinated overlapping control strategy. Instead of changing one component's displacement after the other (sequential), both components have their displacements changed simultaneously in an overlapping manner during gear ratio transitions. This merging of control actions enables quick transitions while preventing jerking or lugging, thereby improving both transition speed and operational smoothness.
Data Source
AI summary
A method is provided for controlling a gear ratio change in a hydrostatic drive machine. The hydrostatic drive machine includes a variable displacement pump and at least one variable displacement motor fluidly connected with the variable displacement pump. The method includes a step of determining a gear ratio rate of change corresponding to a change from a current gear ratio to a new gear ratio. Start and stop overlap gear ratios corresponding to the gear ratio rate are determined and define an overlap range. The current gear ratio is changed to the new gear ratio using electronic signals at least in part by simultaneously changing displacements of the variable displacement pump and the at least one variable displacement motor at gear ratios within the overlap range, and sequentially changing displacements of the variable displacement pump and the at least one variable displacement motor at gear ratios outside the overlap range.