CVT Variator Speed Ratio Closed-Loop Feedback Control
Solution Overview
Problem
Current continuously variable transmission (CVT) systems have slow response times and rely heavily on accurate stepper motor positioning for adjusting variator speed ratios, leading to inefficiencies and increased costs due to hydraulic system lag.
Innovation Solution
Implementing a closed-loop feedback control system that adjusts the position of rollers between input and output disks using a motor, allowing for real-time sensing and adjustment of variator speed ratios based on driver and vehicle inputs, enabling quick and accurate control of transmission speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If hydraulic solenoids and hydraulic controls are used to vary hydraulic force, then the CVT system can adjust roller position, but the response time is slow due to lag in the hydraulic systems
Solution Approach 1:
The patent replaces the hydraulic control system with an electric motor-driven system. The motor directly adjusts the roller position based on control signals from the controller, eliminating the hydraulic lag and providing faster response time. This substitution of mechanical/hydraulic actuation with electric motor actuation resolves the contradiction between response speed and system complexity.
2Measurement precision
If a stepper motor is used to adjust actuator position in open-loop, then the desired roller position can be achieved, but the response time is slow and accuracy depends heavily on stepper motor positioning precision
Solution Approach 1:
The patent implements a closed-loop feedback control system where the controller continuously monitors the actual roller position and compares it with the desired position. Based on the position error, the controller adjusts the motor drive signals to eliminate the error. This feedback mechanism provides both high accuracy and fast response time, resolving the contradiction between precision and speed by dynamically correcting position errors rather than relying solely on open-loop stepper motor positioning.
3Measurement precision
If stepper motor positioning accuracy is increased to achieve desired VSR, then positioning precision improves, but system cost increases
Solution Approach 1:
The closed-loop feedback control system achieves high positioning accuracy using a standard motor rather than a precision stepper motor. The feedback controller compensates for positioning errors through continuous adjustment, allowing the use of lower-cost motors while maintaining the required accuracy. This resolves the contradiction between positioning precision and manufacturing cost.
Data Source
AI summary
A system and method of controlling a continuously variable transmission with variator speed ratio (VSR) closed-loop feedback is provided. The method includes determining a desired VSR based on at least one of the driver and vehicle inputs, determining a motor position adjustment needed to adjust the position of a roller to achieve the desired VSR, driving the motor based on the determined motor position adjustment needed, sensing a transmission output speed as the motor is being driven, determining an actual VSR as the motor is being driven, and providing closed-loop feedback corresponding to any difference between the actual VSR and the desired VSR and driving the motor to eliminate the difference, thereby achieving the desired VSR.