Toroidal CVT Gain Scheduling for Stable High-Speed Ratio Control
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Solution Overview
Problem
Toroidal continuously variable transmissions face limitations in high-speed conditions due to impaired control responsiveness at the expense of control stability, as the gain of closed-loop control needs to be reduced to maintain stability, leading to insufficient sensitivity in following fine fluctuations in transmission ratio.
Innovation Solution
A transmission controller that adjusts the gain of closed-loop control based on disc rotation speed ranges, decreasing sensitivity in low-speed ranges to prevent instability and maintaining responsiveness in high-speed ranges by adjusting the rate of decrease in sensitivity, ensuring both control stability and responsiveness across the entire speed range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the gain of closed-loop control is reduced to maintain control stability at high rotation speeds, then control stability is improved, but control responsiveness deteriorates
Solution Approach 1:
The gain of the closed-loop control is made dynamically adjustable based on the rotation speed of the disc. The control device switches between a first gain value for low-speed ranges and a second gain value for high-speed ranges, allowing the system to adapt its responsiveness characteristics to match the operational conditions and tilt sensitivity variations across different speed regimes.
Solution Approach 2:
The invention changes the control parameter (gain value) based on the rotation speed parameter. By detecting the rotation speed and selecting appropriate gain values from multiple predetermined values, the system optimizes the balance between stability and responsiveness for each operating condition, preventing both instability at high speeds and excessive responsiveness at low speeds.
2Stability of the object's composition
If the gain of closed-loop control is continuously reduced in inverse proportion to rotation speed increase, then control stability is maintained, but the gain becomes excessively small in high-speed range, impairing control responsiveness
Solution Approach 1:
The rotation speed range is segmented into multiple ranges (low-speed range and high-speed range), with each range having its own optimized gain value. This segmentation allows the system to prevent instability in low-speed ranges while maintaining adequate responsiveness in high-speed ranges, avoiding the excessive gain reduction that would occur with continuous inverse proportionality.
Solution Approach 2:
The gain value is dynamically selected from multiple predetermined values based on the detected rotation speed. The control device switches between different gain values corresponding to different speed ranges, enabling the system to maintain appropriate responsiveness characteristics across the entire operating range without excessive gain reduction at high speeds.
Data Source
AI summary
A transmission controller of a toroidal continuously variable transmission includes a gain setting unit that adjusts a gain of closed-loop control for calculating a target value of a roller position in accordance with a change in a rotation speed of a disc in a first rotation speed range and a second rotation speed range higher than the first rotation speed range. The gain setting unit changes, in the first rotation speed range, the gain so that sensitivity of the closed-loop control decreases with an increase in the rotation speed, and changes, in the second rotation speed range, the gain so that a rate of decrease in the sensitivity of the closed-loop control with the increase in the rotation speed is smaller than that in the first rotation speed range.