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CVT Final Presentation.RevC

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CVT Final Presentation.RevC

  1. 1. CVT Project MATT MYERS, DELANEY BALES, TAYLOR VANDENHOEK, ALEK LINQUIST, JESS MCCAFFERTY ME 416, FALL 2014
  2. 2. Background CVT - Continuously Variable Transmission ◦ Transitions between an infinite number of gear ratios ◦ Primary pulley driven by engine RPM ◦ Secondary pulley driven by torque Baja Team runs a CVT to transfer power from the engine to the gearbox.
  3. 3. How CVT Works http://grabcad.com/library/cvt-gearbox-1
  4. 4. Purpose The CVT on the Cal Poly Baja car has several factors leading to inefficiencies and improper tuning. ◦ Last year we tried tuning the CVT with different weights. ◦ Placed 33rd in the Acceleration Event with 5.023 seconds ◦ 1st place had a time of 4.199 seconds CVT should be custom tailored for Baja Car. This model would be used by the Baja Club to predict CVT performance based on variable inputs.
  5. 5. Goals Our goal as a group was to improve the efficiency of the CVT through theoretical modeling. ◦ Create dynamic model of CVT ◦ Determine most influential variables ◦ Determine the relationships between variables ◦ Reduce time to distance from 0-100 ft and 0-150 ft ◦ Improve acceleration time by 10%, from 5.023s to 4.58s, which would equal 5th place based on 2014 results.
  6. 6. Baja Vehicle Performance Tractive Effort Curve ◦ Ideal Tractive Effort ◦ Actual Tractive Effort ◦ Road Load ◦ Traction Limit Ideal CVT Ratio MOTOR CVT GEARBOX CVJ TIRES η = 96% η = 98%10 HP η = 85% 3.5-0.9:1 6.25:1 Reff = 10in.
  7. 7. 0 500 1000 1500 2000 2500 0 5 10 15 20 25 30 35 FORCE,LBF VEHICLE SPEED, MPH TRACTIVE EFFORT ROAD LOAD TRACTION LIMIT IDEAL TRACTIVE EFFORT ACTUAL TRACTIVE EFFORT
  8. 8. 0.0 1.0 2.0 3.0 4.0 5.0 6.0 0 5 10 15 20 25 30 35 CVTRATIO VEHICLE SPEED, MPH IDEAL CVT RATIO ACTUAL CVT RATIO IDEAL CVT RATIO
  9. 9. Theoretical Model SolidWorks model of CVT primary pulley. Adams simulation of primary pulley to generate the pulley diameter as a function of time and belt tension. Simulink model to calculate time to distance of the vehicle. SolidWorks Adams Simulink
  10. 10. Assumptions RPM increases steadily (no longer constant) Asphalt, no slip Ignore belt stretching Constant belt length and width Constant center-to-center distance between pulleys Constant effective vehicle mass
  11. 11. SolidWorks CVT primary pulley Can control ramp angle, weight (material density or volume)
  12. 12. Ramps 70 Degrees 68 Degrees [Flat] 66 Degrees Θ ΘΘ
  13. 13. Weights Adjusted mass of 'weights' in Adams ◦ 50 grams ◦ 60 grams ◦ 70 grams ◦ 80 grams
  14. 14. Adams Import SolidWorks model and run primary pulley to generate pulley diameter as a function of time and belt side pressure Can control: ◦ Belt Side Pressure ◦ Engine RPM ◦ Weights ◦ Spring Rate
  15. 15. Results from Adams
  16. 16. -0.018 -0.014 -0.009 -0.005 0.000 0 500 1000 1500 2000 2500 3000 3500 4000 0.000 0.500 1.000 1.500 2.000 PULLEYDISPLACEMENT,METERS ENGINESPEED,RPM TIME, SECONDS RESPONSE TIME WITH VARIOUS WEIGHTS RPM 50 GRAMS 60 GRAMS 70 GRAMS 80 GRAMS
  17. 17. (ramp results) (Jess will send) -0.018 -0.014 -0.009 -0.005 0.000 0 500 1000 1500 2000 2500 3000 3500 4000 0.000 0.500 1.000 1.500 2.000 PULLEYDISPLACEMENT,M ENGINESPEED,RPM TIME, SECONDS RESPONSE TIME WITH VARIOUS RAMP ANGLES RPM 66 DISP 68 DISP 70 DISP
  18. 18. Simulink Calculate time to distance of vehicle, from 0 to 100 ft using Ideal CVT Ratio.
  19. 19. Simulink Calculate time to distance of vehicle, from 0 to 100 ft using Ideal CVT Ratio.
  20. 20. 0 5 10 15 20 25 30 35 0 50 100 150 200 250 300 350 400 0 1 2 3 4 5 6 7 8 9 10 VEHICLESPEED,MPH DISTANCE,FEET TIME, SECONDS IDEAL CVT RATIO RESULTS DISTANCE VELOCITY
  21. 21. Summary and Findings ◦ Primary does not operate independently from secondary. ◦ Keeps expanding after engine reaches 3400 RPM. ◦ Dynamic belt side pressure ◦ From Adams: ◦ More weight means faster expansion and quicker response time. ◦ Ramp angle has the best chance of obtaining Ideal CVT Ratio ◦ Spring stiffness shifts elongates the displacement vs. rpm graph ◦ Adams is good for finding trends, but not good for giving realistic data ◦ Model the secondary pulley ◦ Experimental results would be better than analytical model results
  22. 22. References Aaen, Olav. Clutch Tuning Handbook. 2007. Print. Adams Tutorial Kit for Mechanical Engineering Courses. 2nd ed. MSC Software. Print. Budynas, Richard, and J. Keith Nisbett. Shigley's Mechanical Engineering Design. 9th ed. New York: McGraw-Hill, 2011. Print. Cha, S.W., W.S. Lim, and C.H. Zheng. "Performance Optimization of CVT for Two-Wheeled Vehicles." International Journal of Automotive Technology 12.3 (2010): 461-68. Print. Chang-song, Jiang, and Wang Cheng. Computer Modeling of CVT Ratio Control System Based on Matlab. IEEE, 2011. 146-150. Print. Narita, Yukihito. "Design of Shaft Drive CVT - Calculation of Transmitted Torque and Efficiency." Power Transmission and Gearing Conference. Vol. 5B. ASME, 2005. 875-881. Print. Willis, Christopher Ryan. A Kinematic Analysis and Design of a Continuously Variable Transmission. Blacksburg, VA: Virginia Polytechnic Institute and State University, 2006. Print.

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