Belt Drive Sensor Assembly for Unambiguous Toe Angle Detection
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Solution Overview
Problem
Existing power steering systems for motor vehicles face challenges in accurately determining the current toe angle of the wheels based on the rotational positions of the pulleys in the belt drive, especially when the detection history is not available, such as during vehicle startup or after a tire change.
Innovation Solution
A belt drive system with two pulleys of different diameters, where the diameters correspond to integer multiples of a unit length that are coprime, is used in conjunction with sensor assemblies to detect the rotational positions of the pulleys. This setup allows for the unambiguous assignment of pulley positions to specific toe angles of the vehicle wheels over the entire adjustment range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single sensor assembly is used to detect the rotational position of one pulley, then the device complexity is reduced, but the measurement precision and reliability of determining the current toe angle deteriorates because the rotational position cannot be unambiguously assigned to a specific toe angle
Solution Approach 1:
The system divides the measurement task into two separate sensor assemblies, each detecting the rotational position of a different pulley (drive pulley and driven pulley). This segmentation allows the system to capture the complete motion state of the belt drive, enabling unambiguous determination of the current toe angle through combined evaluation of both pulley positions.
Solution Approach 2:
The belt drive system itself acts as an intermediary that couples the two pulleys. By measuring the rotational positions of both pulleys and evaluating their relationship through the belt transmission, the system indirectly determines the toe angle with higher precision than a single sensor could achieve directly.
2Measurement precision
If additional sensor assemblies are added to enable unambiguous determination of the current toe angle, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The sensor assemblies serve multiple functions: they detect the rotational position of their respective pulleys, enable determination of the belt drive's adjustment position, and facilitate calculation of the current toe angle. This multi-functionality justifies the addition of sensors by demonstrating their versatile utility throughout the system.
Solution Approach 2:
The system continuously monitors the rotational positions of both pulleys and uses this feedback to determine the current adjustment position of the belt drive and calculate the toe angle. This ongoing feedback loop ensures accurate, real-time steering control throughout the entire adjustment range.
3Manufacturing precision
If the pulley diameters are not based on coprime integer multiples of a unit length, then the manufacturing precision requirements are reduced, but the reliability of unambiguous toe angle determination deteriorates due to ambiguous positional correspondence
Solution Approach 1:
The system changes the critical parameter of pulley diameter specification to use coprime integer multiples of a unit length. This parameter choice creates a mathematical guarantee that each combination of pulley positions corresponds to exactly one adjustment position, ensuring reliable toe angle determination while maintaining practical manufacturing tolerances.
Solution Approach 2:
The use of coprime integers creates an asymmetric relationship between the pulley circumferences that prevents periodic ambiguity. This asymmetric design ensures that the positional correspondence between the two pulleys is unique throughout the entire adjustment range, eliminating the possibility of ambiguous toe angle determination.
4Reliability
If the belt drive is designed with coprime integer multiple diameters to ensure unambiguous position assignment, then the reliability of toe angle determination improves, but the manufacturing precision requirements worsen due to stricter diameter ratio control
Solution Approach 1:
The coprime integer ratio is predetermined in the design phase, allowing manufacturers to plan and prepare the appropriate pulley dimensions before production. This preliminary specification enables the use of standard manufacturing tolerances while guaranteeing the mathematical properties needed for unambiguous position determination.
Solution Approach 2:
By changing the diameter specification to coprime integers, the system transforms a continuous parameter control problem into a discrete parameter selection problem. This allows manufacturers to choose from standard size increments that satisfy the coprime requirement without needing ultra-precise control of the actual diameter measurements.
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 enables precise determination of the current toe angle of the wheels without the need for additional sensors or rotation history, ensuring safe and reliable vehicle control across various steering positions.
Implementation Method 1
In principle, it is possible to use inductive, capacitive, magnetic and/or optical sensors to determine the rotational position of the pulleys
Data Source
AI summary
A belt drive comprises a first pulley with a first diameter and a second pulley with a second diameter as well as a belt which is arranged in each case on a lateral surface of the first and the second pulley and is configured to transmit a rotational movement of the first pulley to the second pulley. Furthermore, the belt drive has a first sensor assembly, which is arranged and configured to detect a rotational position of the first pulley, and a second sensor assembly, which is arranged and configured to detect a rotational position of the second pulley. The first diameter corresponds to a first integer multiple of a unit length and the second diameter corresponds to a second integer multiple of the same unit length, wherein the first and second integer multiples of the unit length are coprime.