Motor Vehicle Torque Range Control for Wheel Speed Correction
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Solution Overview
Problem
Existing electric drive systems in motor vehicles are limited to a first setting range that prevents them from applying torques opposite to the wheel's direction of movement, leading to inefficient wheel acceleration and potential mechanical tension in the drive train, especially at low coefficients of friction, affecting steering control and lateral stability.
Innovation Solution
Implementing a second setting range that allows torques with a sign deviation from the torque setpoint, enabling the drive device to apply positive drive torque during braking and negative braking torque during acceleration, controlled by a central unit and actuator-specific control devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric drive device is limited to a first setting range between zero torque and torque setpoint, then the control system maintains simplicity and avoids mechanical tension, but the system cannot rapidly correct speed deviations leading to loss of steering control and lateral stability
Solution Approach 1:
The control system dynamically adjusts the setting range based on operating conditions. When speed deviation exceeds a threshold, the system transitions from the first setting range (zero to torque setpoint) to a second setting range (negative torque limit to positive torque limit), enabling rapid correction while maintaining normal operational simplicity
Solution Approach 2:
The system changes the torque parameter range from a restricted first setting range to an extended second setting range with opposite signs, allowing the drive device to generate torques in both directions for rapid speed correction when needed
2Productivity
If the electric drive device applies only torques in the direction of wheel movement, then mechanical tension in the drive train is avoided, but wheel acceleration becomes inefficient especially at low coefficients of friction
Solution Approach 1:
The system dynamically selects between unidirectional torque application (avoiding mechanical tension) and bidirectional torque application (improving acceleration efficiency) based on speed deviation thresholds and operating conditions
Solution Approach 2:
The torque sign parameter is changed from always positive (or zero) to allowing negative values when speed correction is needed, improving acceleration efficiency without causing sustained mechanical tension
3Reliability
If the drive device is integrated into braking control with limited torque range, then the system structure is simplified, but the system cannot maintain speed limits during sudden friction changes
Solution Approach 1:
The control system continuously monitors actual wheel speed and compares it with the speed limit value, using this feedback to determine when to expand the torque setting range from the first to the second setting range for rapid correction of speed deviations
Solution Approach 2:
The torque setting range parameter is changed from a restricted first setting range to an extended second setting range when speed deviation exceeds the threshold, enabling the system to maintain speed limits during sudden friction changes
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
Enhances steering control and lateral stability by rapidly correcting deviations from speed limits, ensuring safe and efficient integration of electric drive and braking systems, even in sudden friction changes.
Implementation Method 1
the wheel is assigned a drive device with a controllable second actuator, in particular an electric machine
Implementation Method 2
the wheel is assigned a wheel braking device with a controllable first actuator
Data Source
AI summary
A method for operating a motor vehicle. The motor vehicle has at least one axle with at least one wheel assigned a wheel braking device with a controllable first actuator. The wheel is assigned a drive device with a controllable second actuator. Depending on an acceleration request or braking request, at least one torque setpoint for the actuators and a speed limit value can be specified. A first setting range extending between a zero torque and the torque setpoint is specified for a torque that can be generated by the second actuator. The second actuator is controlled within the first setting range to meet the acceleration request or braking request. An actual speed value is recorded and compared with the speed limit value, and depending on the comparison, a second setting range is provided.