EMPAct and slip control: key elements to efficiency improvement of the pushbelt CVT Bram Veenhuizen, Bram Bonsen, Tim Klaassen, Patrick Albers (TU Eindhoven), Christophe Changenet, Stéphane Poncy (ECAM Lyon) 2004 International Continuously Variable and Hybrid Transmission Congress September 23-25, CVT-49

2 Related papers 04CVT-3: Modelling Shift Speed Characteristics of a Pushbelt type CVT Oral Only: Measurement and Control of Slip in a CVT 04CVT-8: Proposal for an Electromechanical Ratio and Clamping Force Actuator for a Metal V-belt Type CVT 04CVT-13 Control-Oriented Identification of an Electromechanically Actuated Metal V-belt CVT

3 Contents Variator actuation: state of the art. Reference transmission efficiency analysis Efficiency improvement options –EMPAct system –slip control Loss comparison, loss reduction Conclusions & recommendations Next steps

4 LuK/Audi control (Multitronic) Double piston and two stage torque sensor technology Cam disc 1 Cam disc 2 Cam disc 1

5 Servo-electro-hydraulic Variator Control Hydraulic servo technique, driven by stepper motor. Closed loop ratio and pressure control. Over clamping still needed due to inaccuracies in torque estimation. ECU TCU Torqu e signal HC12

6 Reference transmission 200 Nm; 110 kW Variator Final reduction Oil pump Main loss sources:

7 Efficiency Analysis Pump driving power Variator losses –Variator torque loss –Variator slip loss Final reduction losses

8 Pump driving power

9 Variator Torque loss

10 Efficiency vs Safety 1500 [rpm] over-drive

11 Variator slip loss Normal Operating Area slip loss: few tenths of percent

12 Loss breakdown of reference transmission 1500 [rpm] over-drive

13 Improvement options (actuation and control) Avoid over clamping completely Avoid hydraulic limitations for low clamping forces Reduce actuation power rigorously Avoid bandwidth limitation Proposed system: Servo-electromechanical actuation Slip control

14 TU/e EMPAct system Avoid hydraulic non-linearities Focus: slip control (S f =1) F sec =unknown! Force balance Use electric power (hybrids) In steady state: 200 W at 200 Nm

15 Traction curve: Compare with ASR Variator Tire Desirable operating point Typical traction curve in Overdrive

16 Gaining efficiency with increased slip S f =3 S f ~1 Efficiency. gain

17 Slip control test rig; pulley position sensor

18 Slip control benefits Maximized efficiency Lower variator load leading to higher power density or more ratio coverage Increased robustness (!) Probably leads to more dynamic ratio shifting Also applicable to hydraulic systems Lower hydraulic pressure

19 Loss comparison ReferenceEMPAct & slip control

20 Loss reduction

21 Conclusions & Recommendations CVT efficiency still offers room for improvement. Servo actuation and slip control offer great efficiency potential. Develop CVT-ASR. We need small cheap servo-motors of <200 Watt continuous, ~750 Watt peak and low power consumption at low speed. (depends on CVT spec). Slip sensing device is needed.

22 Next steps Realise EMPAct proto; perform no- load tests. Develop control strategy (slip&ratio). Implement slip control on dyno. Implement slip control in car. In preparation for 3rd International CTI Symposium (Würzburg, Nov 30-Dec 2, 2004) Combine EMPAct and slip control in a car. Validate efficiency and fuel consumption. First results

23 TR3 Dyno (110 kW, Jatco CK2) Implement slip control on a dyno

24 Slip Controller More details: American Control Conference (ACC), June 8 to 10, 2005 Portland, Oregon LVDT, mounted in CK2

25 Preliminary results Low, controlled 200 rad/sec