1. Does the difference in geometry make any difference in the calculation of torque, friction, etc.?
The transmitted force and torque depends on the gear ratio between the pinion and rack degrees of freedom and the mass/inertia of the two parts. If you attach a Rack and Pinion Gear Constraint between properly constrained rack and pinion parts, the geometry only affects the torque/force if the mass and inertia calculations are based on the geometry.
2. Is it possible to reproduce a rack and pinion mechanism like the one in the image? I want the pinion gear to spin without any constraint from the rack when there is no gear.
Yes - simply omit the Rack and Pinion Constraint
3. How can I create an accurate gear using MATLAB files and Simulink blocks?
If you are speaking of the geometry, you can import the parts from CAD or use MATLAB to define extrusions for the parts. See the Simscape Multibody Parts Library for examples.
4. How can I reproduce realistic gears with gear friction, inertia, etc.?
Inertia effects are included automatically. The Rack and Pinion Constraint only implements the constraint between the gear angle and the rack displacement; you would need to add the friction effects yourself, either by adding damping to the joints defining the pinion and rack degrees of freedom or by using the External Force and Torque block.
--Steve
