CVT Ratio Control with Adaptive Lead-Delay Compensation
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Solution Overview
Problem
Continuously variable transmissions experience instability and insufficient damping, leading to longitudinal vibration due to inadequate lead compensation, which can result in system instability when attempting to increase damping performance.
Innovation Solution
A control device for continuously variable transmissions that incorporates a lead compensation unit and a delay compensation unit, adjusting the target transmission control value based on input side rotation speed, input torque, transmission ratio, and rate of change of the transmission ratio to improve stability and damping, using phase lead and phase delay compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If lead compensation amount is increased to improve damping performance, then stability of transmission ratio is improved, but high frequency gain becomes larger causing transmission ratio control system to become unstable
Solution Approach 1:
The patent applies dynamics by making the lead compensation amount variable rather than fixed. The control device dynamically adjusts the lead compensation amount based on operating conditions (vehicle speed, engine load, transmission ratio) to optimize damping performance while preventing control system instability. This resolves the contradiction by adapting the compensation level to current system state rather than using a static high compensation value that causes instability.
Solution Approach 2:
The patent changes the parameter of lead compensation amount based on operating conditions. By varying the compensation amount according to vehicle speed, engine load, and transmission ratio, the system achieves adequate damping performance without excessive high frequency gain that would cause instability. This parameter adaptation resolves the trade-off between damping and stability.
2Stability of the object's composition
If lead compensation is performed with fixed lead amount for peak value frequency, then damping performance is improved, but sufficient damping cannot be obtained in all operating states
Solution Approach 1:
The patent makes the lead compensation amount dynamic by adjusting it according to operating conditions such as vehicle speed, engine load, and transmission ratio. This allows the system to achieve sufficient damping performance across all operating states rather than being limited to a fixed compensation value optimized for peak value frequency only.
Solution Approach 2:
The patent changes the lead compensation parameter based on operating conditions to maintain adequate damping performance across the full range of vehicle operations. By adapting the compensation amount to current operating state, the system achieves versatile damping performance rather than being constrained to a single fixed value.
3Object-affected harmful factors
If lead compensation is increased to suppress longitudinal vibration, then damping is improved, but control responsiveness may be degraded due to system instability
Solution Approach 1:
The patent dynamically adjusts the lead compensation amount to achieve adequate vibration suppression without excessive compensation that would cause instability and degrade responsiveness. By adapting the compensation level to operating conditions, the system suppresses longitudinal vibration effectively while maintaining control responsiveness.
Data Source
AI summary
A control device for a continuously variable transmission performs transmission control so that an actual transmission control value becomes a target transmission control value. The control device includes a lead compensation unit, delay compensation unit, and a setting unit. The lead compensation unit performs lead compensation of the target transmission control value. The delay compensation unit performs delay compensation of the target transmission control value. The setting unit is configured to set as the target transmission control value a post-compensation target transmission control value for which compensation is performed by the lead compensation unit and the delay compensation unit according to at least one of an input side rotation speed of the continuously variable transmission, an input torque to a driven side rotation element of the continuously variable transmission, a transmission ratio of the continuously variable transmission, and a rate of change of the transmission ratio.