Toroidal CVT Gain Control Across Low- and High-Speed Ranges
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Solution Overview
Problem
Toroidal continuously variable transmissions face limitations in high-speed applications due to impaired control responsiveness and stability, as the gain of closed-loop control must 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, decreasing sensitivity in low-speed ranges to prevent instability and maintaining responsiveness in high-speed ranges by adjusting the rate of decrease in sensitivity, allowing for both control stability and responsiveness across a broader 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 (lower) for high rotation speeds to ensure stability, and a second gain value (higher) for low rotation speeds to maintain responsiveness. This dynamic adjustment resolves the contradiction by adapting the control parameter to the operating conditions.
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 a set of predetermined values, the system optimizes the balance between stability and responsiveness across different operating ranges.
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, and different gain values are assigned to different segments. Instead of a continuous inverse proportion reduction, the gain is reduced in discrete steps corresponding to different rotation speed ranges. This segmentation prevents the gain from becoming excessively small while maintaining stability across the full speed range.
Solution Approach 2:
The control system dynamically selects from a set of predetermined gain values based on the current rotation speed range. This dynamic switching approach allows the system to maintain appropriate control authority even at high speeds, avoiding the excessive gain reduction that would occur with continuous inverse proportion scaling.
3Ease of operation
If the tilt sensitivity of the power roller increases with rotation speed, then transmission ratio adjustment capability is improved, but control stability deteriorates due to excessive sensitivity
Solution Approach 1:
The control gain parameter is changed according to the rotation speed to compensate for the varying tilt sensitivity. At high rotation speeds where tilt sensitivity is naturally higher, a lower gain is applied to prevent excessive control activity and maintain stability. At low rotation speeds where tilt sensitivity is lower, a higher gain is applied to ensure adequate responsiveness.
Solution Approach 2:
The control system uses feedback from the rotation speed sensor to continuously monitor operating conditions and adjust the control gain accordingly. This feedback mechanism ensures that the control stability is maintained across varying rotation speeds by adapting the gain to the current tilt sensitivity conditions.
Data Source
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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.