Electric Transmission Control for Wheel Loader Digging Slip Prevention
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Solution Overview
Problem
Electric work vehicles with speed-controlled electric transmissions experience wheel slip during the 'digging' phase due to high torque delivery, causing operator discomfort and tire deterioration, as the existing systems fail to manage torque effectively within the wheel slip limit.
Innovation Solution
A method and system that automatically reduce the target speed of the vehicle by adjusting the proportionality ratio between the accelerator pedal deflection and vehicle speed, specifically during digging conditions, to prevent wheel slip, allowing for more manageable operations and maintaining propulsion without excessive tire wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If speed control strategy is implemented with accelerator pedal identifying vehicle speed value, then electric motor can deliver high torque, but wheel slip occurs during digging phase
Solution Approach 1:
The control system dynamically adjusts the proportionality ratio between accelerator pedal deflection and target vehicle speed based on detected digging conditions. When digging is detected, the ratio is reduced to limit torque delivery and prevent wheel slip; when digging ends, the ratio returns to normal. This dynamic adaptation resolves the contradiction between maintaining high torque capability and preventing wheel slip during specific operating conditions.
Solution Approach 2:
The system changes the control parameter (proportionality ratio) based on the operating condition. By detecting digging conditions through multiple sensors and conditions, the system modifies the relationship between pedal position and target speed, thereby controlling torque delivery to stay within wheel slip limits during digging while maintaining normal performance elsewhere.
2Productivity
If high torque is delivered to maintain propulsion during digging, then vehicle can overcome resistance, but excessive tire deterioration occurs
Solution Approach 1:
The system takes preliminary action by detecting digging conditions before excessive torque delivery occurs. By monitoring multiple parameters (vehicle speed, torque, arm position, bucket angle, hydraulic function status), the system anticipates the need to limit torque and adjusts the proportionality ratio accordingly, preventing both wheel slip and tire deterioration while maintaining adequate propulsion capability.
3Reliability
If operator manually controls accelerator pedal to prevent wheel slip, then propulsion is maintained, but operator comfort decreases
Solution Approach 1:
The control system performs self-service by automatically detecting digging conditions and adjusting the proportionality ratio without operator intervention. The system monitors multiple parameters, determines when digging conditions exist, and autonomously modifies torque delivery characteristics, freeing the operator from manual dose control while maintaining wheel slip prevention and propulsion capability.
Data Source
Figure 1~2
Figure 3
AI summary
Method of controlling an electric transmission of a mechanical shovel (CWL) equipped with an arm (B) and a shovel or bucket (T), the transmission comprising an electric motor (M) of propulsion, the method comprising, acquiring a value of a deflection (a) of an accelerator pedal (AP) and a control process of the electric motor (M) so as to achieve a speed control in closed loop, wherein the target speed value is a function of said value deflection according to a predetermined proportionality ratio, and when a digging operation is recognized, said predetermined proportionality ratio is reduced to a settable value.