Multi-Link Rear-Wheel Steering with Single-Motor Dual-Mode Control
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Solution Overview
Problem
Existing rear-wheel steering systems face reliability issues due to the use of multiple actuators, which can lead to uncoordinated steering if one actuator fails, and they lack comprehensive control over steering and braking performance.
Innovation Solution
A dual-mode active rear-wheel steering device incorporating a multi-linkage mechanism and extendable-retractable push rod assemblies, controlled by electromagnetic pin pullers, allows simultaneous control of rear-wheel steering angles and switching between steering and braking modes using a single motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple independent actuators are used to control rear-wheel steering, then steering precision can be improved, but system reliability deteriorates due to potential actuator failure
Solution Approach 1:
The patent combines multiple actuator functions into a single integrated actuator that controls both left and right rear wheels through a unified mechanical linkage system. This single actuator drives a rack and pinion mechanism that simultaneously adjusts the toe angles of both rear wheels, eliminating the need for separate actuators and thereby improving system reliability while maintaining steering precision.
Solution Approach 2:
The single actuator is designed to perform multiple functions: it controls the steering angle of both rear wheels, adjusts the mechanical linkage geometry, and can operate in different modes (steering mode and braking mode) by varying its output. This multi-functional design replaces what would traditionally require multiple specialized actuators.
2Reliability
If a single actuator is used to control rear-wheel steering, then system reliability is improved, but steering precision and control capability deteriorate
Solution Approach 1:
The patent introduces a rack and pinion mechanism as an intermediary between the single actuator and the rear wheels. The actuator drives the pinion, which moves the rack laterally, and this rack is mechanically linked to both rear wheel steering knuckles. This intermediary mechanism amplifies and distributes the single actuator's motion precisely to both wheels, maintaining steering precision.
Solution Approach 2:
The mechanical linkage system is designed with dynamic geometry that adapts to different steering conditions. The linkage arms and connection points are positioned to optimize the mechanical advantage and steering angle distribution across different vehicle speeds and steering inputs, ensuring precise control throughout the operating range.
3Adaptability or versatility
If extendable-retractable push rod assemblies are used, then adaptability to different steering conditions is improved, but device complexity increases
Solution Approach 1:
The extendable and retractable push rod functions are merged into the existing mechanical linkage structure. The push rods are integrated with the rack and pinion mechanism, using the same actuator output to both drive steering and adjust linkage geometry. This integration adds adaptability without proportionally increasing complexity.
Solution Approach 2:
The push rod assemblies are designed with variable length capability that activates only when needed for specific steering conditions. The rods can extend or retract dynamically based on the required steering angle and vehicle speed, allowing the mechanism to adapt its geometry while maintaining a relatively simple base structure.
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 system reliability by eliminating the need for multiple actuators, improves steering and braking performance, and ensures safe operation under various conditions by allowing adaptive steering and self-locking mechanisms.
Implementation Method 1
a first electromagnetic pin puller; and a second electromagnetic pin puller
Data Source
AI summary
A dual-mode active rear-wheel steering device based on a multi-linkage mechanism, including: a steering angle control motor with a speed-reduction mechanism, a multi-linkage mechanism assembly for converting rotational motion of the steering angle control motor into linear motion of an end of the push rod, a steering actuating mechanism for converting linear motion of the multi-linkage mechanism assembly into rotation of a knuckle around a kingpin to make the rear wheels steer, a first electromagnetic pin puller and a second electromagnetic pin puller respectively configured to control a first extendable-retractable push rod assembly and a second extendable-retractable push rod assembly to work at a fixed or variable axial length. The device uses the steering angle control motor to drive the two rear wheels to turn in the same direction or opposite directions through the control of energized state of the two electromagnetic pin pullers.