CVT Speed Signal Filtering for Vibration-Induced Ratio Instability
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Solution Overview
Problem
Vibrations in a vehicle's powertrain cause undesired distortion in the speed signal of a continuously variable transmission (CVT), leading to unstable shift control, reduced fuel efficiency, and decreased durability.
Innovation Solution
A method and device that utilize a vehicle speed filter to stabilize the target transmission ratio by filtering the speed signal, using filter coefficients to determine the filtered speed signal, and a transmission calculator to calculate a stable target transmission ratio based on the filtered signals from the acceleration pedal and vehicle speed, thereby reducing vibration-induced distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional vehicle speed filter is used to process the speed signal, then the filtering capability is insufficient and the response speed is slow, but increasing the filtering capability and response speed may amplify vibration-induced distortions in the target transmission ratio
Solution Approach 1:
The patent applies dynamics by making the filter coefficient adaptive rather than fixed. The filter coefficient is dynamically adjusted based on the correlation between the speed signal and acceleration signal, allowing the filtering strength to vary with driving conditions. This resolves the contradiction by enabling strong filtering when needed (high correlation indicates vibration) while maintaining responsiveness when not needed (low correlation indicates normal operation).
Solution Approach 2:
The patent changes the parameter of filter coefficient from a static value to a dynamically adjustable parameter. By calculating the correlation between speed and acceleration signals and using this to modulate the filter coefficient, the system adapts its filtering behavior to match actual vibration conditions, achieving both stability and responsiveness without excessive complexity.
2Stability of the object's composition
If the vehicle speed filter strongly filters the speed signal to reduce vibration distortion, then the stability of target transmission ratio improves, but the response speed of the filter decreases
Solution Approach 1:
The filter coefficient is made dynamic and adaptive based on real-time correlation analysis between speed and acceleration signals. When vibration is detected (high correlation), stronger filtering is applied to improve stability. When no vibration is present (low correlation), weaker filtering maintains fast response. This dynamic adaptation resolves the stability-speed tradeoff.
Solution Approach 2:
The system uses feedback by continuously monitoring the correlation between speed and acceleration signals and adjusting the filter coefficient accordingly. This closed-loop approach ensures that filtering strength is optimized in real-time based on actual vibration conditions, achieving stability when needed without sacrificing normal response speed.
3Speed
If no filtering is applied to the speed signal, then the response speed remains fast and the system remains simple, but the target transmission ratio becomes unstable due to vibration-induced distortion
Solution Approach 1:
The patent introduces an intermediary mechanism - the correlation-based filter coefficient adjustment system - that mediates between the raw speed signal and the filtered signal used for transmission ratio calculation. This intermediary layer selectively attenuates vibration components while preserving legitimate speed changes, achieving both stability and responsiveness.
Solution Approach 2:
By changing the filter coefficient parameter based on correlation analysis, the system adapts its filtering behavior to match actual vibration conditions. This parameter change enables the system to achieve stability when vibration is present without sacrificing normal response speed, resolving the contradiction between filtering and responsiveness.
Data Source
AI summary
A method of filtering a target transmission ratio of a continuously variable transmission of a vehicle includes: controlling, by a controller, a vehicle speed filter configured to filter a speed signal of a vehicle distorted due to vibration of the vehicle; controlling, by the controller, a target driving pulley speed memory configured to output a target driving pulley speed signal of the continuously variable transmission based on an output value of an acceleration pedal sensor and the filtered speed signal of the vehicle; and controlling, by the controller, a transmission calculator configured to calculate a target transmission ratio of the continuously variable transmission that is a stable value based on the target driving pulley speed signal of the continuously variable transmission and the filtered speed signal of the vehicle, wherein the vehicle speed filter increases filtering capability and a response speed of the vehicle speed filter and decreases the speed signal of the vehicle to a value that makes the target transmission ratio of the continuously variable transmission stable.