Off-Highway Vehicle Adhesion Control via Traction Motor Duty Cycle
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Solution Overview
Problem
Existing systems for off-highway vehicles fail to accurately detect and correct wheel slip, often leading to unnecessary reduction in tractive effort, as they either uniformly reduce power or completely shut down traction motors, which can be overly corrective and inefficient.
Innovation Solution
A method that detects wheel slip by measuring parameters such as voltage and current of traction motors, compares them to running averages, and adjusts the duty cycle of the traction motor driving the slipping wheel based on the severity of slip, while also implementing a system-wide adhesion loss detection and correction system to modify the duty cycles of all traction motors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the output of the genset or energy source is reduced to correct adhesion loss, then wheel slip is eliminated, but the tractive effort of every wheel and the overall motive force provided by the vehicle is reduced
Solution Approach 1:
The patent divides the adhesion control into independent axle-level segments rather than system-wide uniform control. Each axle's traction motors are controlled independently based on its own wheel slip conditions, allowing non-slipping axles to maintain full tractive effort while only slipping axles receive corrective duty cycle reduction.
Solution Approach 2:
The control system applies different duty cycle adjustments to different traction motors based on local wheel slip conditions at each axle. Instead of uniform system-wide power reduction, each motor receives customized control tailored to its specific adhesion conditions, preserving tractive effort where adhesion is adequate.
2Reliability
If the traction motor driving the slipping wheel is completely shut down for a predetermined period of time, then wheel slip is eliminated and other wheels continue to provide maximum tractive effort, but the tractive effort provided by the slipping wheel is unnecessarily reduced (over correction)
Solution Approach 1:
The duty cycle is dynamically adjusted based on the severity of wheel slip detected at each axle. Rather than static complete shutdown, the system continuously modulates the duty cycle proportionally to slip conditions, allowing tractive effort to be recovered once adhesion improves while preventing slip during severe conditions.
Solution Approach 2:
The system uses feedback from wheel speed sensors and traction motor rpm sensors to continuously monitor wheel slip conditions and adjust the duty cycle accordingly. This closed-loop control prevents over-correction by reducing power only to the extent necessary to eliminate slip, then restoring power when adhesion recovers.
3Loss of information
If wheel speed sensors or traction motor rpm sensors are used to determine adhesion loss, then adhesion loss detection is achieved, but the detection accuracy may be insufficient to distinguish between different causes of speed differences
Solution Approach 1:
The patent combines multiple sensing approaches - wheel speed sensors, traction motor rpm sensors, and current/voltage measurements - to detect and verify wheel slip conditions. This multi-parameter monitoring system cross-validates adhesion loss detection and distinguishes between wheel slip and other causes of speed variations.
Solution Approach 2:
The control system uses current and voltage measurements as intermediary parameters to infer wheel slip severity and validate sensor-based detection. These electrical parameters provide additional information about motor load and wheel-m rail interaction, enhancing the precision of adhesion loss detection beyond what speed sensors alone can provide.
Data Source
AI summary
A system and method for controlling adhesion of a wheel of an off-highway vehicle to a surface supporting the wheel measures a parameter of a traction motor of the off-highway vehicle driving the wheel. The parameter is analyzed to determine if wheel slip is present and the severity of the wheel slip. Some embodiments of the invention include adjusting a duty cycle of the traction motor as a function of the severity of the detected wheel slip.