Hydraulic Pump Swash Plate Angle Control for Differential Steering
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Solution Overview
Problem
Existing differential steered vehicles using tandem-pump ground drive hydraulic systems face limitations in steering due to mechanical stresses and reduced top-end speed when swash plates reach their angular limits, as current methods either restrict swash plate angles or reduce efficiency.
Innovation Solution
A method and control system that measure and compare swash plate angles of left and right hydraulic pumps, adjusting them within thresholds to prevent mechanical limits, allowing for increased steering capability and efficiency by dynamically adjusting swash plate angles based on measured parameters like vehicle speed and angle limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the swash plate angle is limited to less than full stroke when not turning, then steering capability is improved by providing headroom for turning, but top-end speed is reduced and pump efficiency is not fully utilized
Solution Approach 1:
The system dynamically adjusts the swash plate angle based on real-time operating conditions. During straight-line travel, the swash plate operates at or near full stroke to maximize speed and efficiency. When turning is detected or initiated, the control system dynamically reduces the swash plate angle to provide the necessary headroom for differential steering, then restores it afterward. This dynamic adjustment eliminates the need for permanent angle limitation.
Solution Approach 2:
The invention changes the swash plate angle parameter dynamically based on the vehicle's operational state. By monitoring parameters such as vehicle speed, steering input, and pump displacement, the control system adjusts the swash plate angle to optimize performance for the current condition - maintaining full stroke for maximum speed during straight travel, and reducing it only when turning is required.
2Force
If the swash plate reaches its mechanical limit (full angular travel), then maximum torque is available, but steering capability is limited and mechanical stresses increase causing binding
Solution Approach 1:
The control system performs preliminary action by detecting the intent to turn (through steering input sensors or differential speed commands) before the vehicle actually begins to turn. Upon detecting this intent, the system proactively reduces the swash plate angle from its maximum position, creating the necessary angular headroom in advance. This prevents the swash plate from reaching its mechanical limit during the turning maneuver, thereby maintaining both torque availability and steering capability.
Solution Approach 2:
The system continuously monitors the swash plate angle, vehicle speed, and steering commands, using this feedback to adjust the swash plate position. When the system detects that a turn is being initiated or that the vehicle is approaching a condition where the swash plate would reach its mechanical limit, the feedback loop triggers a reduction in the swash plate angle to prevent binding and maintain steering capability while preserving as much torque as possible.
Data Source
AI summary
A method of differentially steering a hydraulically driven vehicle includes measuring left and right swash plate angles of pumps which drive left and right wheels of the vehicle and if the angles are different from one another and the larger swash plate angle is equal to or exceeds a threshold value then reducing the larger swash plate angle. If the larger swash plate angle is between the threshold value and a lower limit, or below the lower limit the swash plate angle is increased. Control systems and vehicles include swash plate angle sensors and actuators in communication with a controller which effects the steering control method.