The motion-input port "q" for the "Revolute Joint" block is the angle about the primitive axis given as a function of time. Similarly, the motion-input ports "px" and "py" of the "Rectangular Joint" block is the position coordinate along the primitive axis, given as a function of time. Please refer to the "Motion Input" section in the following documentation to understand more about these inputs:
Instead of inputting the acceleration to the joint, the angle/position itself can be provided as an input through the "Simulink-PS" converter block to the motion-input port of the joint block. This converter block automatically converts the angle/position input to it's time derivatives, velocity and acceleration. Kindly refer to the following documentation to understand how to configure the converter block to output the input's time derivatives:
Additionally, you can refer to the following documentation on "Input Handling" to understand how to specify actuation inputs to joints:
I hope this answers your query.
