Simscape: Constraining Translational Network with Slider Crank Block

Hi,

I am building a Simscape digital twin of a twin-cylinder opposed-piston engine. I am unsure if my basic block configuration is correct to describe a single crankshaft with two opposing cylinders. When the pistons of the left and right cylinders are at their TDC positions (initial conditions set to TDC with peak cylinder pressures) where the crank initial angle should be 270 degrees CA and 90 degrees CA (horizontal), respectively. However, in the model, I need to enter 180 CA and 90 CA, respectively, in an attempt to get reasonable rotation of the crank. I have used an Ideal Angular Velocity Source (94.3 rad/s) in an attempt to help debugging, however, the motion of the slider seems erratic. I will paste a schematic of the crank assembly, and image of the model below. Any help be great, as seem to struggling with what seems like a basic Simscape task of constraining the translational motion of the piston mass with the slider-crank block.

My model uses a simply force input imported directly from the workspace, where the left cylinder force is positive in sign (translating the piston mass to the right), and the right cylinder force is negative in sign (translating the piston mass to the left), and the translational motion is constrained by the crank assemby, with a crank radius of 70 mm (total stroke of 140 mm) and a con rod length of 400 mm, and assumes a rotational speed of 94 rad/s (15 Hz) so a basic model.

Thanks, Patrick

[Yifeng Tang]

I feel like this is fix-able :)

are you able to attach the model for better diagnostics?

[Patrick]

Hi Yifeng,

Thanks for responding to my question. I am working on a diagnostic model using force's imported from the workspace, can I send it to your MATLAB email address?

Thanks, Patrick

[Yifeng Tang]

Hi Patrick, please reach out to Technical Support. You may mention this MATLAB Answer post and my name, and ask them to route your inquiry to Application Engineering. Thanks!