1. Model Based Control for a Pressure Control Type CVT
Wansik Ryu, Juhyun Nam, Hyunsoo Kim,
Sungkyunkwan University
Yongjoon Lee,
Hyundai Motor Company
Dynamic System Design & Control Lab.
Sungkyunkwan University

2. Introduction Flow Control Type Pressure Control Type
Pressure control is easier than the flow control in maintaining the desired CVT speed ratio.
Pressure control system has an advantage of preventing the belt from slippage in active manner.

3. Purpose of Study
Design a ratio controller for pressure control type CVT
Design a model based controller
Investigate model based controlled CVT shift performance

4. Pressure Control Type Ratio Control Valve
Solenoid presusre
Feed back pressure
Spring
force

5. CVT System Dynamics Force equilibrium of the spool motion
State equation of the primary pressure
where
CVT shift dynamics by Ide (1995)

6. Pressure Characteristics at a Steady State

7. P-line

8. Prediction of Shift Performance by P-line
Shift speed at B is the fastest among the three points, A, B and C

9. Prediction of Shift Performance by P-line

10. Experiments for Ratio Control Performance
CVT Test rig

11. Block Diagram of Ratio Control with PID Control

12. There exist small response lag in the CVT ratio response
Control Performance
There exist small response lag in the CVT ratio response

13. Ratio Response for Stepwise Input of Ps

14. Steady State Pressure Characteristics with P-line
Psol=3.5bar
Psol=2.5bar

15. Model Based Control

16. Model Based Control

17. Model Based Control

18. Conclusion
A P-line is proposed from the steady state relationship between the primary pressure and secondary pressure
CVT shift performance is predicted using the P-line
Linear control algorithm such as PID type controller can be used for the pressure control type CVT
A model based control algorithm is proposed
The model based control is able to provide improved tracking performance and robustness