Steer-By-Wire Wheel Actuator Sensing With Redundant Dual Principles
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Solution Overview
Problem
Future steer-by-wire steering systems require precise and reliable determination of the tie rod position without a mechanical connection to the steering wheel, necessitating improved methods for unambiguous and safe position sensing.
Innovation Solution
A drive unit with two sensor units, each with different measuring principles, is used to determine the position of the control rod, utilizing a vernier principle through meshing spur gears to ensure precise and redundant angle measurement, with one sensor providing primary control and the other providing secondary redundancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two sensors with identical measuring principles are used to determine tie rod position, then measurement precision is improved, but reliability deteriorates due to risk of simultaneous failure and interference
Solution Approach 1:
The patent changes the measuring principle parameter from identical to different for the two sensors. The first sensor uses a first measuring principle (e.g., magnetic) and the second sensor uses a second measuring principle (e.g., optical), preventing simultaneous failure modes and interference while maintaining precise position determination through complementary measurement approaches
Solution Approach 2:
The patent combines different sensor types (analogous to composite materials) where the first sensor and second sensor have different measuring principles. This composite sensing approach leverages the strengths of each sensor type while mitigating their individual weaknesses, achieving both high precision and high reliability
2Measurement precision
If a shaft stub with sensor is installed in steer-by-wire system, then position reference signal is provided, but device complexity increases and economical efficiency deteriorates
Solution Approach 1:
The patent merges the position sensing function into the existing motor structure by using the motor's rotor shaft and auxiliary shaft as the sensing elements. The first sensor detects the rotor shaft angle and the second sensor detects the auxiliary shaft angle, eliminating the need for separate shaft stubs and reducing system complexity while maintaining measurement precision
Solution Approach 2:
The patent makes the motor shafts serve multiple functions: they provide both the mechanical drive function and the position sensing function. The rotor shaft and auxiliary shaft are not only drive elements but also serve as the measured objects for the sensors, thereby eliminating redundant components and simplifying the overall system
Data Source
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AI summary
The invention relates to a drive unit (100) for a a steer-by-wire system (S) for a vehicle (F), having: - a motor (10) for providing a drive power to a control rod of the wheel actuator, - a sensor device (20) for determining the position of the control rod (101), wherein the sensor device (20) has a first sensor unit (21) and at least one second sensor unit (22), the first sensor unit (21) is designed to detect the angle of a rotor shaft (11) of the motor (10), and the second sensor unit (22) is designed to detect the angle of an auxiliary shaft (12) which is mechanically operatively connected to the rotor shaft (11), - a transmission device (30) for providing the mechanical operative connection between the rotor shaft (11) and the auxiliary shaft (12), and - a controller (40) for actuating the sensor device (20) and/or for determining the position of the control rod (101) of the wheel actuator (110), said first sensor unit (21) and second sensor unit (22) using different measuring principles.