Hydrostatic Drive Swashplate Control Feedback
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Solution Overview
Problem
Conventional hydrostatic drive unit control systems for work vehicles lack operational feedback to operators, leading to productivity and controllability losses due to excessive de-stroking of the swashplate in response to increasing loads, which is either not addressed in closed-loop systems or results in substantial losses in open-loop systems.
Innovation Solution
A control system that determines a reference swashplate position and monitors the actual position, generating a compensated current command to adjust for loading conditions, reducing the swashplate de-stroke sensitivity while maintaining operator feedback by using a controller coupled with sensors and valves to regulate hydraulic fluid pressure and flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If open-loop control systems are used to provide operational feedback to the operator, then the operator receives tactile indication of increased loads through swashplate de-stroking, but substantial productivity and controllability losses occur
Solution Approach 1:
The control system monitors the actual swashplate position and compares it to the reference position, then generates a compensated current command based on the difference. This closed-loop feedback mechanism provides the operator with operational feedback through controlled swashplate de-stroking while preventing excessive de-stroking that would cause productivity losses.
Solution Approach 2:
The system dynamically adjusts the swashplate position by modifying the current command to the hydraulic pump based on loading conditions. By changing the electrical parameter (current) in response to detected position deviations, the system achieves controlled de-stroking that provides feedback without sacrificing productivity.
2Productivity
If closed-loop control systems maintain fixed swashplate position regardless of loading conditions, then productivity is maintained, but the operator receives no operational feedback about load increases
Solution Approach 1:
The system introduces a controlled feedback mechanism that allows the swashplate position to deviate from the reference position based on loading conditions. This provides the operator with tactile feedback about load changes while the control system actively manages the deviation to prevent excessive de-stroking and maintain productivity.
Solution Approach 2:
Instead of completely preventing swashplate de-stroking (which would eliminate feedback), the system allows partial de-stroking that is sufficient to provide operational feedback to the operator. The compensated current command ensures the de-stroking remains within acceptable limits that do not significantly impact productivity.
3Loss of information
If the swashplate is allowed to de-stroke freely in response to increasing loads, then operational feedback is provided to the operator, but controllability and productivity are substantially reduced
Solution Approach 1:
The control system implements a feedback loop that monitors actual swashplate position and generates compensatory current commands. This feedback mechanism provides operational feedback to the operator through controlled position changes while actively counteracting excessive de-stroking that would impair controllability.
Solution Approach 2:
The system applies preliminary anti-action by generating a compensated current command that counteracts the natural de-stroking tendency of the swashplate under load. This preemptive control action prevents excessive de-stroking before it occurs, maintaining controllability while allowing sufficient de-stroking for operator feedback.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system reduces load sensitivity and increases controllability and productivity by providing the operator with tactile feedback of increasing loads while minimizing the swashplate de-stroke, thus enhancing the overall performance of the work vehicle.
Implementation Method 1
the hydraulic pump has a displacement chamber for hydraulic fluid. The fluid flow is controlled by the angular position of a swashplate of the pump, which controls the effective length of the displacement chamber
Implementation Method 2
The fluid flow from the pump causes the drive motor to rotate the axles, which drive the wheels and, thus, the work vehicle
Data Source
AI summary
A method for controlling a hydrostatic drive unit of a work vehicle is disclosed. The method may generally include determining a reference swashplate position for a hydraulic pump of the hydrostatic drive unit, wherein the reference swashplate position is associated with an uncompensated current command, and monitoring an actual swashplate position of the hydraulic pump, wherein the actual swashplate position differs from the reference swashplate position due to a loading condition of the work vehicle. In addition, the method may include determining a current compensation based at least in part on the actual and reference swashplate positions and generating a compensated current command by adjusting the uncompensated current command based on the current compensation, wherein the compensated current command is associated with a compensated swashplate position for the hydraulic that differs from the reference swashplate position.