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Modeling a Generic Engine + Continuously Variable Transmission in SimDriveline 2.3 (R2012b)

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Phin on 22 Jul 2014
Answered: Steve Miller on 6 Aug 2020
I am trying to model a rear wheel drive, light off-road vehicle with an IC Engine, CVT and fixed gear ratio in SimDriveline. I am using the Generic Engine as my source, and I am dividing the power and angular velocity from the engine to get torque as an input into the Variable Ratio Transmission (which represents the CVT, through a signal builder, changing the ratio from 2 to 1 with respect to time). There is also a final gear with an 8:1 ratio.
I have successfully modelled a 3-speed transmission (using dog clutches) with the same parameters, then replaced the 'Gearbox' subsystem with the 'CVT+Final drive'.
The issues I have are that;
1. When throttle is fully depressed (signal at 1) the Variable Ratio Transmission does not seem to vary the ratio (even when I make the slope of the ratio variation very high), rather the engine max's out and I get an error message.
2. When I input an impulse signal to the engine, the engine revs rise from stall rapidly to just below max (depending on the size of the impulse), and it stays there for the whole 60s simulation, while the engine power rises to max then drops back down to zero, which means I have no torque (there is a momentary large oscillation on the torque sensor, which dies out quickly) going into the CVT, and the vehicle hardly moves.
I am struggling to understand why the model is not working. I have attached the .slx and .mdl file in a zip folder. Thanks in advance
  1 Comment
Matheus  Bastos Freire da Motta
Have you already find out what was wrong?
I am having a Little Trouble to set up my CVT Parameters. What did you do to get your cvt Ratio?
Best Regards Matheus

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Answers (1)

Steve Miller
Steve Miller on 6 Aug 2020
The original model did not have a mechanical connection between the engine and the Variable Ratio Transmission. That means the engine torque was only applied to the input shaft, not to the Variable Ratio Transmission or the Vehicle itself. This caused the engine to redline and stop the simulation.
I have put in a mechanical connection between the engine and the rest of the driveline. I also enabled the redline controller so that the engine won't go so fast as to trigger the error diagnostic. With these changes, the simulation runs the entire 60 seconds. In the Simscape Results Explorer, you can see the ratio vary in the Variable Ratio Transmission block. I also stiffened the compliance in the Variable Ratio Transmission block so that there are fewer oscillations in the beginning.
A screenshot is below and the model is attached.

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