Electric Vehicle Hold Torque Control for Uphill Rollback
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Solution Overview
Problem
Electric vehicles lack features to mitigate rollback effectively, which is the tendency to move backward when launching on an uphill grade due to the absence of a torque converter, leading to inefficiencies and reduced driveability transparency compared to conventional vehicles.
Innovation Solution
A driveline controller in electric vehicles determines a position baseline, compensates speed, and applies hold torque to the motor-generator to counteract rollback, considering factors like slope, mass, and brake activity to prevent oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a torque converter is used in conventional vehicles to mitigate rollback, then rollback is reduced, but energy efficiency deteriorates due to continuous driveline torque
Solution Approach 1:
The patent removes the torque converter from the electric vehicle drivetrain while implementing a control system that extracts only the necessary rollback mitigation function. The motor-generator controller applies torque based on position baseline and speed compensation, achieving rollback prevention without the continuous energy loss associated with torque converters.
Solution Approach 2:
The patent replaces the mechanical torque converter with an electronic control system. Instead of using a mechanical device to continuously transmit torque, the system uses electronic sensing of position and speed combined with motor-generator control to achieve the same rollback mitigation function with superior energy efficiency.
2Loss of energy
If electric vehicles launch from standstill on uphill grades without torque converters, then energy efficiency is improved, but rollback control deteriorates
Solution Approach 1:
The patent establishes a position baseline when the vehicle is stationary or at speed polarity transition before launch. This preliminary positioning information is stored and used during subsequent acceleration phases to detect and correct rollback, enabling effective control without continuous energy expenditure.
Solution Approach 2:
The patent implements a feedback mechanism where the controller continuously monitors vehicle position relative to the baseline and speed, then adjusts motor-generator torque accordingly. The position compensated speed calculation provides feedback that enables real-time rollback correction while maintaining energy efficiency.
3Stability of the object's composition
If hold torque is applied continuously to prevent rollback, then vehicle positioning stability is improved, but driveline oscillations increase
Solution Approach 1:
The patent applies hold torque periodically rather than continuously. The controller monitors position baseline and speed, applying torque only when rollback is detected. This periodic application based on actual need maintains positioning stability while avoiding the continuous torque application that causes driveline oscillations.
Solution Approach 2:
The patent applies torque selectively rather than fully continuously. By using position compensated speed and speed factor calculations, the system applies only the necessary amount of torque to prevent rollback, avoiding excessive torque application that would generate driveline oscillations while still achieving adequate positioning stability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides effective rollback mitigation, enhancing driveability transparency by ensuring stable vehicle positioning on inclines without driveline oscillations, particularly beneficial for large vehicles like buses and trucks.
Implementation Method 1
generating a command for a motor-generator of the vehicle to apply the hold torque
Data Source
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.