Vehicle Wheel Slip Estimation Using Segmentation and Intermediary Signals
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Solution Overview
Problem
Existing methods for estimating wheel slip in motor vehicles are unreliable, particularly when wheels are slipping, which hinders accurate calculation of vehicle speed and behavior.
Innovation Solution
A method using on-board computer calculations, involving wheel rotation speed measurements, slip derivatives, and unreliability signals to determine wheel slip states, allowing for reliable estimation of wheel slip and subsequent calculation of vehicle speed and behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wheel rotation speed sensors are used to measure rotational speeds, then real-time vehicle information is obtained, but the rotational speeds do not correctly reflect vehicle behavior during wheel slipping
Solution Approach 1:
The patent segments the wheel population into reliable and unreliable wheels based on slip indicators. The vehicle speed calculation is performed separately for reliable wheels (those without slip) and unreliable wheels (those with slip). This segmentation allows the system to maintain accurate speed estimation by excluding slipping wheels from the calculation, thereby resolving the contradiction between having real-time sensor data and ensuring measurement precision during slip events.
Solution Approach 2:
The patent introduces an intermediary mechanism - the slip indicator and unreliability signal - that mediates between the raw wheel speed measurements and the final vehicle speed calculation. This intermediary layer identifies which wheels are slipping and filters them out of the speed calculation, allowing the system to maintain accurate vehicle speed estimation even when some wheels are slipping, thus resolving the measurement precision issue.
2Reliability
If simple wheel speed measurement is used, then device complexity is low, but the estimation is unreliable when wheels are slipping
Solution Approach 1:
The patent makes the existing wheel speed sensor system multi-functional by adding computational logic that enables both normal speed measurement and slip detection functions. The same sensor infrastructure serves dual purposes: providing vehicle speed information during normal operation and identifying slipping wheels when needed. This universality increases reliability without requiring separate dedicated slip detection hardware, thus limiting the increase in device complexity.
Solution Approach 2:
The system performs self-diagnosis by using the wheel speed data itself to detect slip conditions. The slip indicator is generated by analyzing the relationship between wheel speeds and vehicle speed, allowing the system to identify unreliable measurements without external assistance. This self-service approach improves reliability through intelligent algorithms rather than additional sensors, keeping device complexity manageable.
3Measurement precision
If all wheel speeds are used for speed calculation, then calculation is simple, but accuracy decreases when some wheels are slipping
Solution Approach 1:
The patent segments the wheel population into reliable and unreliable subsets based on slip indicators. The vehicle speed calculation is performed separately for reliable wheels (those without slip) and unreliable wheels (those with slip). This segmentation allows the system to maintain accurate speed estimation by excluding slipping wheels from the calculation, thereby resolving the contradiction between having real-time sensor data and ensuring measurement precision during slip events.
Solution Approach 2:
The patent implements a dynamic selection process where the set of wheels used for speed calculation changes based on real-time slip conditions. When wheels are slipping, they are dynamically excluded from the calculation; when not slipping, they are included. This dynamic adaptation ensures measurement precision varies with operating conditions, automatically optimizing accuracy without requiring complex manual intervention, thus balancing precision and calculation complexity.
Data Source
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AI summary
The invention relates to a method for estimating the reference speed of an automobile. According to the invention, the method comprises calculating for each wheel the sliding (Sxij) from the rotation speed (Wij) of the wheel and the longitudinal movement speed (Vest) obtained, calculating for each wheel, from the measured wheel rotation speed (Wij) and another value, a wheel sliding derivative (dSxij), calculating a wheel-sliding non-reliability signal (NF), and calculating the sliding indicator (dij).