Hello community,
I have a fairly specific conceptual problem regarding my project. I am trying build a simscape model which should be able to represent the vehicle's longitudinal behavior when a specific throttle input is given for certain environmental factors (like inclination, etc.), similar to the Matlab vehicle model examples. Unfortunately, I could not find a solution to my problem by analyzing the example models. Note that my model still looks a bit messy and is not finished yet.
The model:
The model consists of a generic engine block with a torque-speed map which is given a throttle input. There is logic controlled clutch between the engine and the tranismission which engages once the engine reaches a certain rpm. In order for the engine to work from an initial velocity of zero, I understand that I either need a torque converter, which I will implement once I obtain data or a logic controlled clutch. The vehicle is able to shift gears (implemented by a transmission block) and accelerates to v_max as expected. The tire-ground contact and longitudinal body 'dynamics' are implemented by using a vehicle body block, a simple tire block and a custom block that accepts a variable rolling resistance ceofficient. The model works as expected for a maximum statinary throttle input and a small road incline. Note that I implemented data values from a real working vehicle whereever I could. For any unknowns, I either changed them by trial and error so that the models works/ the model still represents the real vehicle or I left the parameters as their default values. All lines that do not seem connected in the attached screenshots are connected to scopes etc.
My problem:
When I lower the throttle input or increase the systems resistance by increasing the inclination of the road for example, the engine does not seem to be able to uphold it's torque and the vehicle rolles backwards or does not accelerate at all. From my understanding this is due to the kinetic and static friction torque of the logic controlled clutch and the clutch in the transmission block. If the value is too high, the engine does not seem to have enough power to overcome the torque resistance from the friction of the clutches, if the values is too low, the drivetrain does not get enough power/ torque from the engine.
I am aware that I can rewrite blocks, which I did for the logic controlled clutch. However, the source code for the transmission block protected, so I cannot alter the kinetic and sttaic fricion parameters dynamically. Unfortunately i have to use the transmission block, since I do not have enough data to use a Simscape Drivetrain transmission component.
My question:
Since there are numerous example vehicle models available that use logic controlled clutches and are able to model vehicle behavior for a variable throttle input and torque demand from driving resistances, I wonder if there is a way to get the logic controlled clutch block and the transmission block to work without altering their source code, ot if there is a smarter way of doing this in my specific usecase?
I would be happy for any input since I am not sure how to overcome this problem.
I attached some screenshots of the model so that you can get a general idea of how the model works. I hope this helps.
