Belt-Driven Ball Screw Position Sensing for Steer-By-Wire
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Solution Overview
Problem
The transition to steer-by-wire (SbW) systems has eliminated the need for a mechanical connection between the handwheel and the rack, thereby removing the pinion shaft and rack teeth, necessitating a new position sensor solution that maintains the position signal without a pinion in vehicle steering systems.
Innovation Solution
A belt driven position sensor utilizing a ball screw with a belt operatively coupled to it, pulleys engaged with the belt, and sensor magnets embedded in the pulleys, along with a circuit board to determine the absolute position based on the angular position of the magnets, ensuring a non-repeating signal over full travel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a pinion-driven position sensor is used in traditional REPS systems, then absolute rack position can be provided to the ECU, but the system requires a mechanical connection between the handwheel and the rack which is eliminated in steer-by-wire systems
Solution Approach 1:
The patent extracts the position sensing function from the traditional pinion-driven mechanism. By removing the dependency on the pinion shaft and rack teeth, the invention creates a standalone position sensor system that can function independently of the mechanical connection between handwheel and rack, enabling adaptability to steer-by-wire architectures.
Solution Approach 2:
The belt-driven position sensor serves multiple functions: it provides absolute position sensing, maintains signal resolution equivalent to pinion-driven systems, and enables compatibility with both traditional REPS and modern steer-by-wire architectures. The sensor housing integrates multiple components including pulleys, magnets, and sensor chips into a unified structure that performs both positioning and signal generation functions.
2Measurement precision
If the position sensor is removed from the pinion shaft in steer-by-wire systems, then the mechanical connection is eliminated, but a new position sensor solution is needed to maintain position signal resolution
Solution Approach 1:
The patent introduces a belt as an intermediary element that transfers motion from the ball screw to the pulleys carrying the sensor magnets. This belt-mediated transmission mechanism maintains the precision required for position sensing while decoupling the sensor system from direct mechanical connections to the pinion shaft, enabling both high measurement precision and ease of manufacture in steer-by-wire systems.
Solution Approach 2:
The invention replaces the traditional mechanical pinion-driven position sensor with a belt-driven system that uses a ball screw, belt, and pulley mechanism. This substitution maintains position signal resolution through precise belt-pulley engagement while simplifying manufacturing by eliminating complex pinion shaft integrations and allowing modular assembly of sensor components.
3Reliability
If sensor magnets are embedded in pulleys, then the position signal is maintained without a pinion, but dimensional tolerance stack-up must be accommodated
Solution Approach 1:
The patent employs a flexible belt that can dynamically accommodate dimensional variations in the pulley positions and magnet placements. The belt's flexibility allows the system to absorb tolerance stack-up from manufacturing variations while maintaining reliable position signal transmission, ensuring that minor dimensional deviations do not compromise signal reliability.
Solution Approach 2:
The invention changes the physical state of the connection between the ball screw and sensor magnets from rigid (as in pinion-driven systems) to flexible through the use of a flexible belt. This parameter change allows the system to tolerate dimensional variations in pulley and magnet positioning while maintaining position signal reliability, effectively decoupling signal integrity from strict manufacturing precision requirements.
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 belt driven position sensor maintains the same position signal resolution as pinion-driven systems, reduces mechanical complexity, and minimizes potential failure points by isolating sensor magnets from ball screw rolling and bending, while accommodating dimensional tolerance stack-up.
Implementation Method 1
a ball screw... wherein the belt moves in response to translation of the ball screw
Implementation Method 2
a belt operatively coupled to the ball screw, wherein the belt moves in response to translation of the ball screw. The belt driven position sensor further includes a plurality of pulleys, each of the plurality of pulleys being engaged with the belt, wherein the movement of the belt rotates each of the plurality of pulleys
Implementation Method 3
a circuit board including a plurality of sensor chips, the plurality of sensor chips being configured to detect an angular position of each of the plurality of sensor magnets
Data Source
AI summary
A belt driven position sensor includes a ball screw. The belt driven position sensor also includes a belt operatively coupled to the ball screw, wherein the belt moves in response to translation of the ball screw. The belt driven position sensor further includes a plurality of pulleys, each of the plurality of pulleys being engaged with the belt, wherein the movement of the belt rotates each of the plurality of pulleys. The belt driven position sensor yet further includes a plurality of sensor magnets, at least one of the plurality of sensor magnets being at least partially embedded in each of the plurality of pulleys. The belt driven position sensor also includes a probe housing assembly having a plurality of sensor chips to determine an absolute position of the ball screw based on the angular position of each of the plurality of sensor magnets.