Electric Vehicle Coasting Torque Control for Wheel Slip Stability
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Solution Overview
Problem
Hybrid electric and pure electric vehicles face challenges in maintaining driving stability on low friction road surfaces and improving fuel efficiency, particularly due to wheel slip issues and the inefficiencies of conventional braking systems.
Innovation Solution
A vehicle system comprising a motor, a modulator, and a controller that adjusts coasting torque through pulse width modulation (PWM) based on control values, with the controller determining wheel slip and road surface conditions to manage torque levels, ensuring stability and regenerative braking without hydraulic brake usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If coasting torque is increased to improve fuel efficiency through regenerative braking, then energy recovery is improved, but wheel slip occurs on low friction road surfaces reducing driving stability
Solution Approach 1:
The patent implements dynamic adjustment of coasting torque control strategies based on real-time detection of wheel slip conditions. The controller monitors wheel rotation speeds and dynamically switches between coasting control and safety control modes, adjusting the modulation values sent to the motor controller to prevent wheel slip while maximizing regenerative braking efficiency when conditions permit
Solution Approach 2:
The system employs feedback control by continuously monitoring wheel rotation speeds through sensors and comparing detected values with threshold values. When wheel slip is detected (when the difference in rotation speeds exceeds a threshold for a predetermined time), the controller receives feedback and automatically adjusts the coasting torque by modifying the modulation value, creating a closed-loop control system that balances energy recovery with driving stability
2Speed
If hydraulic brake is used to stop the vehicle quickly, then deceleration performance is improved, but energy is lost without regenerative braking
Solution Approach 1:
The patent changes the control parameters of the motor operating in generator mode to optimize regenerative braking performance. By adjusting modulation values (PWM duty cycles) and torque commands based on vehicle speed, battery state of charge, and wheel slip detection, the system maximizes energy recovery while maintaining adequate deceleration capability, reducing reliance on hydraulic braking
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 system enhances driving stability and fuel efficiency by variably controlling coasting torque during wheel slip events and performing motor regenerative braking, reducing the loss associated with hydraulic braking.
Implementation Method 1
a motor for providing a driving force to the plurality of wheels based on electrical energy stored in a battery
Implementation Method 2
The controller may calculate a modulation value through a pulse width modulation (PWM) method based on at least one of the first control value or the second control value
Data Source
AI summary
A vehicle includes: a plurality of wheels; a motor for providing a driving force to the plurality of wheels based on electrical energy stored in a battery; a modulator for controlling a number of rotations of the motor; and a controller for controlling the modulator based on a first control value at a coasting control and controlling the modulator based on a second control value when a wheel slip occurs in a safety control.