How do I use a generic engine block successfully within my vehicle simscape model?

I have been using the Mathworks "Formula Student: Physical Modeling Training" tutorial videos to create an accurate vehicle simscape model. Part 4 discusses how to model powertrain and I have been having an issue with this.

I am using a torque curve data from an engine dyno to input in to the generic engine block. However the power output drops to zero when a gear change is implemented in the simulation. The torque also seems to feedback data that I would not expect. I am using a three gear subsystem set up as shown:

Running the simulation gives a high initial value of Power which exponentially decreases to zero. If I change the initial rpm of the engine then I achieve a power graph which is more representable, both of which can be seen below:

This graph shows for a run in a constant gear. If I change gear the power rises initially and then drops back to zero gradually. I am new to Simscape and I am not sure if I have run with an incorrect parameter or need to model this differently. Any help or suggestions would be great.

Thanks, Ryan

Answer 1

[Christoph Hahn]

Hi Ryan,

I had a look at your model. Overall your model looks meaningful to me.

Here a few comments:

• If you are starting with Simscape, make sure you watch all video of the training carefully. You will start from scratch and build your models gradually. By jumping within or between the videos you may miss important points.
• I suggest you work with an ideal torque source first before replacing by an actual engine. Hereby you can check whether the torque is enough to obtain the desired accelerations.
• Find attached an example for tabulated torque data for an engine. Make sure you rename the variables accordingly
• You can use callbacks (File -> Model Properties -> Callbacks) to execute code when opening / running the model. Consider running the scripts containing all the parameters here.
• CTRL + R can be used to rotate blocks. That's clearly nitpicking ;-)

In hope that is helpful.

Cheers Christoph

PS I didn't see the same behavior as you were observing. That's mainly because I had to come up with my own tire data and tabulated torque data (find attached) as you only submitted your model without its parameters.

Answer 2

[Christoph Hahn]

Hi Ryan,

can you please attach the model (or a simplified one). I would like to try and see whether I experience sth similar.

Cheers Christoph

[Ryan Dimmock]

Hi Christoph,

Sorry about the delay, I have converted the file to a .mdl as it would not let me attach the .slx file to this comment. Let me know if you need anything else.

Thanks, Ryan

Answer 3

[Christoph Hahn]

Hi Ryan,

I had a look at the model you sent in the mail. Here a few comments:

• The description of the vehicle body says: “Connection H is the mechanical translational conserving port associated with the horizontal motion of the vehicle body. The resulting traction motion developed by tires should be connected to this port.” I attached a screenshot how it could look like. Find the models on FileExchange.

• Make sure you use natural numbers for gears.

Cheers Christoph