Can I apply the force model in the radial engine with pneumatic force model with position as input instead?

I'm doing a free piston linear generator model with dual piston using simmechanics. I'm trying to apply pressure to each side of the piston. So I found the radial engine example and want to apply the force model to my model. So how can I set the force model to be taking piston position instead of crank angle value? I tried to use signal builder to give force to the prismatic joint but it is hard to make it consistent and the pistons keep on moving outside the boundaries and I don't know how to apply the constraints.Therefore i would like to try using pneumatic force model and hope it works. Basically the model looks like the picture. I would like to move the pistons and rod left and right.

Hope you guys can help me. Thanks.

Answer 1

[Steve Miller]

The example sm_radial_engine.slx has a mechanical connection between the piston head and the chamber where the pressure increases and decreases. The pressure in the chamber is deliberately a function of crank angle because it takes two crank turns for the entire cycle. If solely piston position was used, you would have the same pressure if the piston was moving away from the crank or towards the crank.

The model as shown shows you how to use piston position and speed to determine the pressure inside the piston chamber and therefore the force applied to the piston. You can use that as a starting point.

--Steve