Electric Drive Pedal Control for Low-Speed Torque Limiting
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Solution Overview
Problem
Existing electric drive units in vehicles, particularly in wheel loaders, face issues with uncontrollable maximum torque delivery leading to wheel slips and reduced controllability, especially in conditions requiring torque control like digging into piles or slippery grounds.
Innovation Solution
Implementing a method that determines a maximum and reduced current limit function based on the drive pedal speed request, allowing for both speed and torque control by mapping pedal requests to respective current limits, ensuring optimal control in various driving conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the electric drive unit directly provides maximum torque from very low speeds (speed control mode), then the vehicle achieves best drivability and responsiveness, but wheel slips occur and controllability is lost in high-load conditions
Solution Approach 1:
The control system dynamically switches between speed control mode and torque control mode based on operating conditions. At low speeds or high load conditions (below threshold speed), the system transitions to torque control mode where current is limited by the reduced current limit function, preventing wheel slips while maintaining responsiveness when needed
Solution Approach 2:
The system changes the current limit parameter based on speed conditions. The reduced current limit function is applied below a threshold speed to limit torque and prevent wheel slips, while above the threshold speed the maximum current limit function is used for full performance, achieving both controllability and drivability
2Speed
If the electric drive unit provides maximum torque at low speeds, then acceleration is fast and responsive, but wheel slips occur on slippery grounds or when approaching piles
Solution Approach 1:
The control system applies preliminary anti-action by implementing the reduced current limit function before wheel slips can occur. When speed drops below the threshold (indicating high load or slippery conditions), the system proactively limits the current to prevent torque-induced wheel slips, rather than reacting after the slips occur
Solution Approach 2:
The system dynamically adjusts current limiting based on real-time speed feedback. The control unit continuously monitors actual speed and compares it to the threshold, switching between reduced current limit and maximum current limit functions to prevent wheel slips while maintaining acceleration performance when conditions permit
Data Source
AI summary
A method for controlling an electric drive unit of a vehicle, in particular a construction machine such as a wheel loader, wherein the vehicle comprises a drive pedal for providing an actual drive pedal speed request value (SRV) for operating the electric drive unit depending on the degree of operation of the drive pedal, and the electric drive unit being signaling coupled to the drive pedal via a control unit, wherein the electric drive unit is configured for driving the vehicle depending on the actual drive pedal SRV.