Variable Filter Vehicle Speed Estimation for Wheel Slip
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Solution Overview
Problem
All-wheel-drive construction vehicles face challenges in accurately estimating vehicle speed due to dynamically changing road conditions and wheel slip, which affects the convergence of slip and accuracy of existing speed estimation methods.
Innovation Solution
A vehicle speed estimator that includes a rotation speed detector, a reference wheel-speed calculator, a variable filter processor with a time constant changer, and a wheel-speed distribution calculator, which adjusts the time constant of the low-pass filter processing based on travel conditions, acceleration, deceleration, and gear shifts to improve estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed time constant is used for low-pass filter processing in vehicle speed estimation, then the device complexity is reduced, but the measurement precision of vehicle speed deteriorates under dynamically changing road conditions
Solution Approach 1:
The patent implements a variable time constant for the low-pass filter that dynamically changes based on wheel slip conditions. When wheel slip is detected, the time constant is adjusted to maintain accurate vehicle speed estimation despite changing road conditions. This dynamic adjustment resolves the contradiction by adapting the filter characteristics to match the current operating state, thereby maintaining measurement precision without requiring overly complex fixed-structure filters.
Solution Approach 2:
The patent changes the time constant parameter of the low-pass filter based on detected wheel slip conditions and convergence states. By modifying this key parameter in response to changing road conditions, the system maintains accurate vehicle speed estimation without increasing overall device complexity. The parameter change allows the same filter structure to adapt to different operating conditions effectively.
2Measurement precision
If the time constant is made variable to adapt to changing conditions, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent implements a variable time constant that changes based on wheel slip detection and convergence state. This parameter modification allows the low-pass filter to adapt to dynamically changing road conditions, maintaining accurate vehicle speed estimation. The complexity increase is minimal, involving only the addition of detection logic and conditional parameter adjustment, rather than a complete redesign of the filtering system.
Solution Approach 2:
The system uses feedback from wheel slip detection and convergence state monitoring to automatically adjust the time constant. This closed-loop approach allows the filter to adapt to changing conditions based on actual system performance, improving measurement precision without requiring complex manual intervention or overly sophisticated algorithms.
3Ease of operation
If wheel slip convergence is assumed under normal conditions, then the ease of operation is improved, but the reliability deteriorates on irregular ground with constantly changing road conditions
Solution Approach 1:
The patent implements continuous monitoring of wheel slip convergence and uses this feedback to detect when road conditions change. When slip convergence is no longer maintained, the system automatically adjusts the time constant to account for the changing conditions. This feedback mechanism maintains reliability on irregular ground without complicating the basic operation, as the adjustments occur automatically based on detected conditions.
Solution Approach 2:
The system transitions from a static assumption of slip convergence to a dynamic approach that continuously adapts to changing road conditions. By making the time constant variable based on real-time slip detection, the system maintains reliability across diverse terrains while keeping the operational interface simple, as no manual intervention is required to activate the adaptive behavior.
Data Source
AI summary
A vehicle speed estimator includes a unit that selects a minimum rotation speed among rotation speeds of wheels detected by a rotation speed detector and calculates a reference wheel speed of a construction vehicle at every predetermined time. The unit includes: a variable filter processor that performs a low-pass filter processing to the minimum rotation speed, the variable filter processor having a variable time constant; and a time constant changer that changes the time constant of the variable filter processor in accordance with travel conditions of the construction vehicle.