CVT Control Device Thrust Balance Limiting
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Solution Overview
Problem
Existing continuously variable transmission (CVT) systems face issues with transmission ratio overshooting and thrust imbalance during low speed position return control due to excessive accumulation of the control input integral component, leading to undesirable behavior when the vehicle restarts to accelerate.
Innovation Solution
A CVT control device that employs a limiting control mechanism to manage the control input integral component based on thrust balance between the primary and secondary pulleys, maintaining the transmission ratio at the final target by setting a limiting-control limit that decreases stepwise and adjusts to achieve a thrust-balanced state, preventing overshooting and imbalance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the control input integral component is reset to zero when the transmission ratio reaches the target transmission ratio, then the transmission ratio overshooting is prevented, but the thrust balance between the primary pulley and the secondary pulley is disrupted, causing the transmission ratio to behave undesirably during vehicle re-acceleration
Solution Approach 1:
The patent changes the parameter of the control input integral component from being reset to zero to being limited by a threshold value. This parameter change allows the integral component to be maintained within a specific range, preventing both overshooting and thrust balance disruption. The limiting threshold is set based on the relationship between the control input integral component and the thrust difference between pulleys, achieving optimal control precision and stability.
2Productivity
If feedback control with control input integral component accumulation is used during low speed position return control, then the transmission ratio can reach the target transmission ratio, but excessive accumulation causes the transmission ratio to overshoot toward the lower speed position side
Solution Approach 1:
The patent introduces a feedback mechanism where the control input integral component is continuously monitored and limited by a predetermined threshold. When the integral component approaches the threshold, it is restricted to prevent excessive accumulation. This feedback control ensures that the transmission ratio reaches the target efficiently while preventing overshooting, maintaining both productivity and precision.
3Stability of the object's composition
If the control input integral component is limited based on thrust balance, then the transmission ratio stability is maintained, but the system complexity increases due to the need to monitor and adjust multiple parameters
Solution Approach 1:
The patent applies preliminary action by pre-calculating and setting a limiting threshold for the control input integral component based on the thrust balance relationship between pulleys. This threshold is determined in advance and stored in the control unit, eliminating the need for real-time complex calculations during operation. The system simply compares the integral component against this pre-set threshold, maintaining stability while minimizing control system complexity.
Data Source
AI summary
A continuously variable transmission is mounted in a vehicle, and includes a primary pulley, a secondary pulley, and a belt, wherein the belt is wound around the primary pulley and the secondary pulley. A control device performs a low speed position return control by a feedback control employing a control input integral component. The low speed position return control is to control a transmission ratio to a final target transmission ratio for lower speed position while the vehicle is decelerating. The control device performs a limiting control in response to a condition that the transmission ratio has reached the final target transmission ratio during the low speed position return control. The limiting control is to limit the control input integral component based on thrust balance between the primary pulley and the secondary pulley so as to maintain the transmission ratio at the final target transmission ratio.