Steering Actuator Locking via Planetary Screw and Wrap Spring
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Solution Overview
Problem
Existing steering actuator systems face challenges with durability and efficiency, particularly in adaptive rear steering systems, where ball screw transmissions require complex locking mechanisms and lead screw transmissions have high motor mass and low efficiency, while planetary screw drives are difficult to integrate with simple locking mechanisms.
Innovation Solution
A steering actuator system incorporating a planetary screw drive with a wrap spring as a simple locking mechanism, which allows bi-directional rotation of the shaft and prevents back-drive by constriction, reducing system power requirements and enabling efficient actuation of rear wheels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ball screw transmissions are used in steering actuators, then steering precision is improved, but the system requires complex locking mechanisms reducing reliability
Solution Approach 1:
The patent extracts the locking function from a separate complex mechanism and integrates it directly into the planetary screw drive structure. The planetary screw drive inherently provides self-locking capability through its geometric design, eliminating the need for additional locking components while maintaining steering precision.
Solution Approach 2:
The patent combines the transmission function and locking function into a single integrated planetary screw drive mechanism. The planetary configuration merges gear reduction with inherent self-locking properties, achieving both precision steering and automatic locking without separate mechanisms.
2Weight of moving object
If lead screw transmissions are used in steering actuators, then motor mass is reduced, but transmission efficiency deteriorates
Solution Approach 1:
The patent changes the transmission parameters by using a planetary screw drive with optimized lead angle and gear ratio. This configuration achieves efficient power transmission with reduced motor mass by optimizing the mechanical advantage and reducing friction losses through the planetary gear arrangement.
3Loss of energy
If planetary screw drives are used in steering actuators, then system efficiency is improved, but integration with locking mechanisms becomes difficult
Solution Approach 1:
The planetary screw drive is designed to be self-locking through its inherent geometric configuration. The high reduction ratio and specific helix angle create sufficient friction and mechanical advantage to prevent back-driving, allowing the system to lock itself without external locking mechanisms while maintaining high efficiency during active steering.
4Reliability
If complex locking mechanisms are used in steering actuators, then anti-backdrive functionality is improved, but system mass and package size increase
Solution Approach 1:
The patent removes the need for separate heavy locking mechanisms by extracting the anti-backdrive functionality directly into the planetary screw drive structure. The inherent self-locking capability of the planetary configuration provides reliable anti-backdrive protection without additional components, reducing overall system mass.
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
The system achieves optimized efficiency and reduced mass and package size by integrating a planetary screw drive with a wrap spring locking mechanism, providing zero or minimal backlash and effective anti-backdrive functionality without the need for complex locking mechanisms.
Implementation Method 1
a wrap spring wrapped around at least a portion of the wrap spring effector on the pulley sleeve, wherein the wrap spring is configured to constrict in response to the torque applied at the pulley sleeve and rotation of the wrap spring effector on the pulley sleeve
Data Source
AI summary
A steering actuator comprising a shaft having an input coaxial with an output, wherein the output is in drivable communication with one or more wheels of a vehicle, and a locking mechanism configured to enable the shaft to rotate in both a first direction and a second direction in response to torque provided at the input, and prevent the shaft from rotating in both the first direction and the second direction in response to torque provided at the output.