Electric Propulsion Motor Torque Limiting for Crowd Force Control
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Solution Overview
Problem
Electrically propelled work machines experience excessive forward propulsion force when interacting with a material pile, leading to bucket jamming and hydraulic system overload due to the lack of inherent limitations on propulsion force, unlike traditional hydraulic systems.
Innovation Solution
An electronic controller is used to limit the output torque of the electric propulsion motor based on crowd force conditions, preventing excessive force on the work implement by overriding operator commands and reducing motor output torque when a crowd force exceeds a predetermined limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the electric propulsion system provides continuous forward propulsion force, then the loader can effectively load material from the pile, but the bucket may become jammed in the pile due to excessive propulsion force
Solution Approach 1:
The electric propulsion system dynamically adjusts its output based on real-time operating conditions. The controller monitors crowd force conditions and modulates motor torque accordingly, allowing the system to provide high propulsion force when needed for effective loading while automatically reducing force when crowd force exceeds predetermined thresholds, preventing bucket jamming
Solution Approach 2:
The system incorporates feedback control by monitoring crowd force conditions and using this information to adjust propulsion force. The controller receives input about the crowd force state and modifies motor output torque in response, creating a closed-loop control system that prevents excessive propulsion force while maintaining loading effectiveness
2Ease of operation
If the bucket hydraulics are activated simultaneously with driving into the pile, then the bucket can be lifted effectively, but the hydraulic system becomes overloaded due to excessive crowd force
Solution Approach 1:
The system takes preliminary action by limiting propulsion force before hydraulic overload can occur. The controller monitors crowd force conditions and restricts electric motor output when excessive crowd force is detected, preventing the situation where hydraulic systems would otherwise become overloaded during bucket lifting operations
3Productivity
If the operator commands high propulsion force, then the loader can penetrate the material pile effectively, but the crowd force exceeds safe limits causing potential component failure
Solution Approach 1:
The controller continuously monitors crowd force conditions and uses this feedback to modulate motor torque. When crowd force exceeds predetermined safe limits, the system automatically reduces propulsion force despite operator commands, maintaining both productivity and safety through real-time adjustment
Solution Approach 2:
The system changes the operational parameters of the electric motor based on crowd force conditions. By adjusting motor torque and power output according to real-time crowd force measurements, the system maintains optimal performance while preventing excessive crowd force that could lead to component failure
Data Source
AI summary
A method of operating an electrically propelled machine includes the steps of, operating an electrical power source for the machine, and limiting an output torque of an electrical propulsion motor system of the machine based upon the occurrence of a crowd force condition of the machine. An electrically propelled machine is further provided, including an electronic controller having means for limiting motor output torque based at least in part on a crowd force condition of the machine.