Rear-Axle Steering Control for Low-Speed Damage Prevention
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Solution Overview
Problem
Rear-axle steering systems face challenges at low vehicle speeds, particularly below 6 km/h, where increased steering forces can lead to system damage, high energy consumption, and actuator overheating, resulting in customer dissatisfaction and unnecessary repair shop visits.
Innovation Solution
A computer-implemented method for controlling a rear-axle steering system that determines the physical and operating states of the system, specifies a maximum permissible steering angle based on these states and vehicle parameters, and activates the system to prevent excessive steering angles, thereby optimizing its use at low speeds without risking damage or energy inefficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the rear-axle steering system is used in the speed range close to a standstill, then the maneuverability and road position improvement are achieved, but the steering forces required grow strongly leading to increased load and potential damage
Solution Approach 1:
The control device changes the operating parameters of the rear-axle steering system by deactivating it in the speed range close to a standstill (below approximately 6 km/h). This parameter change (speed threshold) prevents the system from operating under conditions where excessive steering forces would cause damage, while allowing full functionality at higher speeds where maneuverability benefits are achieved.
Solution Approach 2:
The system dynamically adjusts its operational state based on vehicle speed. The control device continuously monitors speed and switches the rear-axle steering system between active and deactivated states, optimizing performance across different operating conditions while protecting the system from damaging loads at low speeds.
2Ease of operation
If the rear-axle steering system is activated at low speeds, then steering control is available, but energy consumption increases and the actuator heats up
Solution Approach 1:
The control device uses speed as a threshold parameter to deactivate the rear-axle steering system below approximately 6 km/h. This parameter-based control prevents excessive energy consumption and actuator heating that would occur during frequent low-speed steering operations, while maintaining full energy availability for high-speed maneuvering where the system provides genuine benefit.
Solution Approach 2:
The deactivation of the rear-axle steering system at low speeds, while limiting steering control availability, actually benefits the system by preventing energy waste and actuator overheating. This apparent limitation converts the potential harm of excessive energy consumption into a benefit by preserving actuator availability and reducing overall energy usage.
3Reliability
If the rear-axle steering system is deactivated in the speed range close to a standstill, then damage and energy waste are prevented, but the advantages of rear-axle steering cannot be used
Solution Approach 1:
The control device uses speed threshold (approximately 6 km/h) as a parameter to determine system activation. This parameter-based approach ensures the system is deactivated only in the specific speed range where damage and energy waste occur, while maintaining full functionality at higher speeds, thus balancing reliability and adaptability.
Solution Approach 2:
The system dynamically adapts its operational state based on vehicle speed, being deactivated at low speeds to protect reliability and activated at higher speeds to provide maneuverability benefits. This dynamic adaptation resolves the contradiction by adjusting functionality according to operating conditions.
4Reliability
If the actuator applies sufficient counterforce to return wheels to straight position at standstill, then wheel positioning is maintained, but energy supply requirements increase
Solution Approach 1:
The control device changes the power demand parameter by deactivating the actuator in the speed range close to a standstill. Instead of continuously applying counterforce, the system uses speed-based deactivation to prevent the need for high power output that would be required to overcome adhesive forces at complete standstill, while maintaining wheel position stability through appropriate speed threshold selection.
Data Source
AI summary
A method and device for controlling a rear-axle steering system, in particular a rear-axle steering system of a motor vehicle, determines a current physical condition of the rear-axle steering system on the basis of a detected current operating state and a pre-determined reference operating state of the rear-axle steering system. The method defines a maximum permissible steering angle of the rear-axle steering system depending on the estimated physical condition of the rear-axle steering system and depending on at least one of the operating parameters of driving speed, steering angle and steering angle speed of the vehicle, and actuates the rear-axle steering system such that the steering angle of the rear-axle steering system does not exceed the assigned defined maximum permissible steering angle for the current operating parameter(s) of the vehicle.