Rear-Wheel Steering Control Using Low-Speed Tooth Detection
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Solution Overview
Problem
Existing rear wheel steering systems in vehicles are not designed for continuous use when stationary, leading to undesirable tire scrub and excessive actuator load, and existing wheel speed sensors fail to provide reliable speed data at very low speeds.
Innovation Solution
A control system that utilizes speed-dependent signals from wheel speed sensors, such as tooth count, to permit rear wheel steering based on wheel motion detection, independent of precise speed calculations, allowing steering at very low speeds by detecting incremental tooth counts or waveform features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If rear wheel steering is permitted at very low speeds using traditional wheel speed sensors, then vehicle agility is improved, but the system may experience unreliable speed data and excessive actuator load
Solution Approach 1:
The patent replaces traditional mechanical wheel speed sensors with a toothed wheel encoder system that generates digital pulses. This substitution allows for more reliable detection of wheel motion at very low speeds by counting discrete tooth passages rather than relying on continuous analog speed signals, thereby resolving the contradiction between low-speed operation and signal reliability
Solution Approach 2:
The patent introduces an intermediary processing system that counts tooth passages and determines steering permission based on cumulative tooth count thresholds rather than direct speed measurement. This intermediary approach filters out noise and provides reliable low-speed detection, enabling steering activation at speeds where traditional sensors fail
2Ease of operation
If rear wheel steering is permitted at very low speeds, then vehicle agility is improved, but tire scrub and actuator load increase excessively
Solution Approach 1:
The patent implements dynamic threshold adjustment where the minimum tooth count requirement for steering permission varies based on operating conditions. This allows the system to permit steering at very low speeds when necessary for maneuverability while preventing excessive actuator load by requiring a minimum motion threshold, thereby resolving the contradiction between ease of operation and harmful factors
Solution Approach 2:
The patent changes the control parameter from continuous speed measurement to discrete tooth count accumulation. By requiring a minimum number of tooth passages before permitting steering, the system ensures sufficient wheel motion to avoid tire scrub while still allowing operation at very low speeds, thus resolving the contradiction between maneuverability and harmful effects
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
Enables reliable rear wheel steering at low speeds without tire scrub or actuator overload, improving vehicle agility and reducing battery load by using a control system that estimates wheel motion through coarse speed indications.
Implementation Method 1
receive a speed-dependent signal from a wheel speed sensor, the speed-dependent signal being dependent on a rate at which teeth of a toothed wheel move past the wheel speed sensor
Data Source
AI summary
A control system for a vehicle is described. The control system comprises one or more controllers, the control system configured to receive a speed-dependent signal from a wheel speed sensor, the speed-dependent signal being dependent on a rate at which teeth of a toothed wheel move past the wheel speed sensor, and in dependence on the speed-dependent signal, permitting rear wheel steering of the vehicle. In this way, rear wheel steering can be permitted from a very low speed, at which speeds a vehicle or wheel speed signal is not generally available. By using a tooth count, such low speeds, or at least an indication that the vehicle is moving, may be estimated.