Hydrostatic Vehicle Control for Uncommanded Motion
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Solution Overview
Problem
Hydrostatically driven vehicles, such as asphalt compactors, experience uncommanded motion on graded surfaces or inclines, leading to safety concerns and inefficiencies in material compaction due to inadequate control systems.
Innovation Solution
A system with a variable displacement pump and electronic controller that senses the swashplate angle or propel motor rotation, compares the actual to the desired signal, and arrests vehicle motion when the difference exceeds a threshold for a predetermined time, using a timer to initiate a fault flag and engage the brakes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional control systems are used in hydrostatically driven vehicles, then the vehicle can operate on various terrains, but uncommanded motion occurs on graded surfaces or inclines
Solution Approach 1:
The patent implements a feedback control system that continuously monitors the actual vehicle speed and compares it to the commanded speed. When the difference exceeds a threshold for a predetermined time period, the system automatically adjusts the pump displacement to correct the uncommanded motion. This closed-loop feedback mechanism resolves the contradiction by maintaining reliable control while preventing harmful uncommanded motion on graded surfaces.
Solution Approach 2:
The patent replaces traditional mechanical control linkages with an electronic control system that uses sensors to detect swashplate angle or motor rotation and electronically actuates the pump displacement control. This substitution of mechanical systems with electronic sensing and control enables more precise and responsive control, preventing uncommanded motion while maintaining operational reliability.
2Object-affected harmful factors
If the control system frequently arrests vehicle motion to prevent uncommanded motion, then safety is improved, but operating efficiency and compaction rate are reduced
Solution Approach 1:
The patent applies partial action by using a threshold-based arrest mechanism rather than continuous intervention. The control system only arrests motion when the speed difference exceeds a predetermined threshold for a specific time duration, allowing normal operational variations while preventing harmful uncommanded motion. This selective intervention maintains safety without unnecessarily reducing productivity.
Solution Approach 2:
The patent implements dynamic control by continuously monitoring vehicle speed and automatically adjusting pump displacement in real-time based on the difference between commanded and actual speeds. This dynamic response allows the system to maintain high productivity during normal operation while automatically preventing uncommanded motion when safety concerns arise, optimizing both safety and compaction efficiency.
Data Source
AI summary
A hydrostatically driven vehicle has an engine operating a variable displacement propel pump, a displacement of which can vary based on an angle of a rotating swashplate, such that a fluid flow impelled by the pump transfers power to at least one propel motor rotating a wheel of the vehicle. An electronic controller of the vehicle senses an operating parameter of the system, for example, the angle of the rotating swashplate or the direction and speed of rotation of the propel motor with a sensor to yield an actual signal, and relays the actual signal to an electronic controller. The controller determines a desired angle for the rotating swashplate based on the control signal, and compares it to the actual signal from the sensor. Motion of the vehicle is stalled when the angle signal differs from the desired angle by a predetermined extent and for a predetermined period.