Electric Vehicle Anti-Rollback Torque Control on Inclines
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Solution Overview
Problem
Electric vehicles without torque converters face challenges in mitigating rollback on inclines due to insufficient torque response time and driveline oscillations, which affect driveability and stability.
Innovation Solution
A driveline controller implements a rollback control method using position and speed compensation to generate hold torque, adjusting torque based on vehicle position, speed, grade, and mass, with algorithms to distinguish between oscillations and actual rollback, and limits torque application to prevent driveline instability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If electric vehicles use motor-generators without torque converters, then efficiency is improved, but rollback control capability deteriorates
Solution Approach 1:
The system applies hold torque to the motor-generator before the vehicle actually rolls back, based on predictive algorithms that detect early signs of rollback tendency. This preliminary torque application prevents rollback before it occurs, compensating for the lack of torque converter cushioning effect while maintaining efficiency.
Solution Approach 2:
The control system continuously monitors vehicle position, speed, and motor-generator torque, using this feedback to dynamically adjust hold torque application. The feedback loop enables real-time rollback control without requiring a torque converter, maintaining both efficiency and reliability.
2Reliability
If hold torque is applied to reduce rollback, then rollback is reduced, but driveline oscillations increase
Solution Approach 1:
The system applies only the minimum necessary hold torque to prevent rollback, rather than maximum torque. The control algorithm continuously modulates torque application to achieve just enough counteracting force, avoiding excessive torque that would cause driveline oscillations while still effectively preventing rollback.
Solution Approach 2:
The control system applies hold torque in periodic pulses rather than continuous application, synchronizing with the driveline's natural oscillation frequency to minimize disturbance. This periodic torque application maintains rollback control while reducing driveline instability.
3Reliability
If torque response time is increased to counter gravity on inclines, then rollback control improves, but driveline oscillations worsen
Solution Approach 1:
The system prepares hold torque application in advance based on predictive algorithms that detect incline conditions and vehicle state. By anticipating rollback tendency before it fully develops, the system can apply torque with optimal timing that prevents rollback without causing oscillations from delayed or excessive torque application.
Solution Approach 2:
The control system dynamically adjusts torque response characteristics based on real-time vehicle conditions, incline angle, and driveline state. This dynamic adaptation allows the system to optimize torque application timing and magnitude for each situation, achieving effective rollback control while minimizing driveline oscillations.
Data Source
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AI summary
A method of reducing rollback of a electric vehicle, including determining a position baseline of the electric vehicle; determining a position compensated speed of the electric vehicle based on the position baseline; determining a hold torque as a function of the position compensated speed; and generating a command to apply the hold torque to the motor-generator of the electric vehicle.