EV Torque Control Using Mass and Road Grade Estimation
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Solution Overview
Problem
Electric vehicles face challenges in optimizing regenerative braking and mitigating rollback, especially when vehicle mass and road grade vary, leading to inefficiencies and potential skid events.
Innovation Solution
A driveline controller that estimates vehicle mass and road grade to determine optimal regenerative braking and anti-rollback torque by applying weight factors to initial torque calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If regenerative braking torque is increased to improve energy recovery, then energy efficiency is improved, but vehicle stability deteriorates causing skid events
Solution Approach 1:
The system dynamically adjusts regenerative braking torque based on real-time vehicle mass estimation and road grade detection. The torque application is not fixed but adapts to changing conditions, allowing maximum energy recovery when conditions permit while preventing skids when the vehicle is lightweight or on slippery surfaces
Solution Approach 2:
The system uses feedback from acceleration sensors, grade sensors, and torque measurements to continuously estimate vehicle mass and adjust regenerative braking torque. The controller monitors actual vehicle response and modifies torque application to maintain stability while maximizing energy recovery
2Use of energy by moving object
If vehicle mass estimation is implemented to improve torque optimization, then regenerative braking efficiency is improved, but device complexity increases
Solution Approach 1:
The system uses existing vehicle sensors (acceleration sensors, torque sensors, grade sensors) that are already part of the vehicle's standard equipment. The mass estimation algorithm processes data from these existing sensors without requiring additional specialized hardware, allowing the system to serve itself using available resources
Solution Approach 2:
The system changes the parameter being controlled from a fixed torque value to a dynamically calculated torque value based on estimated mass and road grade. This parameter transformation allows the same hardware to achieve optimized performance across different loading conditions without adding complexity
3Reliability
If anti-rollback torque is applied to prevent vehicle rollback on grades, then vehicle position stability is improved, but energy efficiency deteriorates
Solution Approach 1:
The system applies anti-rollback torque before the vehicle actually rolls backward by detecting grade conditions and estimating mass in advance. This preliminary action prevents rollback from occurring rather than correcting it after the fact, eliminating wasted energy movements
Solution Approach 2:
The system adjusts anti-rollback torque as a dynamic parameter based on estimated vehicle mass and detected road grade rather than using a fixed conservative torque value. This allows minimal torque application sufficient to prevent rollback, optimizing energy efficiency while maintaining position stability
Data Source
AI summary
A method of controlling torque of an electric vehicle, including sensing a surface grade; determining an acceleration of the vehicle; determining an initial torque of the vehicle; estimating a weight of the vehicle based the surface grade, the acceleration, and the initial torque; converting the weight of the vehicle to a weight factor; and determining an output torque by applying the weight factor to the initial torque.