Electric Wheel Torque Control for Tight Cornering Without Slip
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Solution Overview
Problem
Conventional motor vehicles with multiple drive wheels and electric machines struggle to achieve optimal steering response and cornering without slip, especially at maximum steering angles, due to limitations in torque distribution and wheel speed control.
Innovation Solution
A method that independently sets the curve path of a motor vehicle by determining wheel-individual movement speeds and distributing total drive torque based on vehicle speed, steering angle, and chassis geometry, allowing for closed-loop torque control and selective wheel speed adjustments to achieve tighter cornering radii and maintain traction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional steering geometry is used to set setpoint wheel speeds, then the vehicle follows the geometrically specified curve path, but the steering response is limited and cannot achieve tighter cornering radii
Solution Approach 1:
The patent divides the wheel speed control into independent segments for each drive wheel. Each wheel's setpoint speed is calculated independently based on its specific position, steering angle, and vehicle dynamics, allowing individual optimization of each wheel's contribution to cornering performance.
Solution Approach 2:
The system dynamically adjusts setpoint wheel speeds in real-time based on actual vehicle speed, steering angle, and chassis geometry. This dynamic adaptation allows the vehicle to achieve optimal steering response and tighter cornering radii by continuously optimizing the relationship between wheel speeds and steering input.
2Reliability
If wheel-individual speed control is implemented to achieve cornering without slip, then traction is maintained, but the control system complexity increases
Solution Approach 1:
The system employs feedback control by continuously monitoring actual wheel speeds and comparing them against calculated setpoint speeds. Based on this feedback, the control unit adjusts the torque distribution to each drive wheel to maintain the desired speed relationships and prevent slip during cornering maneuvers.
Solution Approach 2:
The patent changes the control parameters from fixed steering geometry-based wheel speeds to dynamic parameters that adapt to vehicle speed, steering angle, and actual driving conditions. This allows the system to maintain optimal wheel speed differentials for cornering without slip across varying operating conditions.
3Speed
If mechanical wheel brakes are used to control setpoint wheel speeds in all-wheel drive vehicles, then wheel speed adjustment is possible, but the system is less responsive compared to direct drive machine control
Solution Approach 1:
The patent replaces the mechanical brake-based wheel speed control system with a direct electric drive machine control system. This substitution allows for more rapid and precise wheel speed adjustment by controlling the torque output of each electric drive machine independently, eliminating the delays and losses associated with mechanical brake actuation.
Data Source
AI summary
A method for operating a motor vehicle having multiple drive wheels and multiple drive machines, each drive machines being an electric machine and being allocated to a drive wheel. The method includes: acquiring a total setpoint drive torque; acquiring a current vehicle driving speed, a current steering angle, and optionally, the wheel loads of all drive wheels; determining wheel-individual movement speeds of the drive wheels over the roadway based on the current vehicle driving speed, the current steering angle, a known chassis geometry of the motor vehicle, and optionally, the wheel loads; determining a setpoint wheel speed for each drive wheel based on the determined movement speeds, and distributing the total setpoint drive torque to all drive wheels such that an actual curve path deviates from a setpoint curve path specified by the steering angle; actuating each drive machine to adjust the setpoint wheel speed at the respective drive wheel.