Dual-Motor Steering Actuator with Redundant Ball Nut Assembly
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Solution Overview
Problem
Existing vehicle steering systems lack redundancy and efficient control mechanisms for reliable axial movement of steerable wheels, particularly in steer-by-wire applications, where motor failures can disrupt steering functionality.
Innovation Solution
A dual-motor system with interconnected gear mechanisms and an electronic control unit (ECU) that monitors motor operation, providing redundancy by adjusting the operation of one motor if the other fails, ensuring continuous steering capability without mechanical connections to a steering input member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single motor is used to rotate the ball nut assembly, then the device complexity is reduced, but the reliability decreases due to lack of redundancy
Solution Approach 1:
The motor system is segmented into two independent motors (first motor and second motor) that can operate independently or simultaneously. Each motor has its own drive train through idler gears to the ball nut assembly, allowing the system to be divided into redundant functional units that can compensate for each other.
Solution Approach 2:
The system incorporates redundant motors before any failure occurs, preparing the steering system in advance to withstand potential motor failures. The ECU continuously monitors motor operation and can switch to the备用 motor if a failure is detected, cushioning against the harmful effects of motor failure.
2Reliability
If dual motors are used to provide redundancy, then the reliability improves, but the device complexity increases
Solution Approach 1:
Both the first motor and second motor are designed with identical structures and functions, capable of performing the same task of rotating the ball nut assembly. This universality allows the system to use redundancy without proportionally increasing complexity, as both components follow the same design template.
Solution Approach 2:
Idler gears are introduced as intermediary components between the motors and the ball nut assembly. These idler gears simplify the transmission mechanism by providing a common intermediate stage, reducing the direct complexity of connecting two separate motors to the same load while maintaining redundancy.
3Adaptability or versatility
If mechanical connections to steering input member are used, then the steering functionality is maintained, but the adaptability decreases in steer-by-wire applications
Solution Approach 1:
The system replaces traditional mechanical steering input connections with an electronic control system. The ECU receives steering input signals electronically and converts them into motor commands, eliminating the need for direct mechanical connections between the steering wheel and the ball nut assembly while maintaining steering functionality.
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 dual-motor system with ECU control ensures reliable and redundant steering, enabling autonomous or assisted steering of vehicle wheels, enhancing reliability and adaptability to vehicle conditions.
Implementation Method 1
A ball nut assembly is connected with an externally threaded portion of the steering member. The steering member moving axially in response to rotation of the ball nut assembly relative to the steering member.
Implementation Method 2
A first motor is connected with the ball nut assembly. The first motor is operable to effect rotation of the ball nut assembly relative to the steering member. A second motor is connected with the ball nut assembly. The second motor is operable to effect rotation of the ball nut assembly relative to the steering member.
Data Source
AI summary
An apparatus for use in turning steerable vehicle wheels includes a steering member which is axially movable relative to the vehicle to effect turning movement of the steerable vehicle wheels. A ball nut assembly is connected with an externally threaded portion of the steering member. A first motor is connected with the ball nut assembly. The first motor is operable to effect rotation of the ball nut assembly relative to the steering member. A second motor is connected with the ball nut assembly. The second motor is operable to effect rotation of the ball nut assembly relative to the steering member.