When designing mechanical control system, the designer is inevitably led to face the problems of kinematics, dynamics, and control. These subjects are explained with two practical application case studies. One is a spatial motion simulator, and the other is an inertially stabilized system (ISS) for tracking radar. Both two applications have many similar and opposite aspects in the point of kinematics, dynamics, and control. For kinematics, motion simulator is a parallel kinematic structure and a non real time problem, but the ISS is a serial and requires a real time computation to compensate the rigid body base motion. The dynamics of motion simulator is nonlinear, and it is derived by Lagrangian equation. But flexible dynamics of ISS can be approximated by Newtonian mechanics. In the control of motion simulator, a robust PID controller is designed, and tuning law and the performance limitations are described. The robust controller of ISS is used to cope with the flexibility uncertainty and to stabilize the line of sight of radar antenna. In addition, performance enhancement method is presented by using disturbance observers to compensate the actuator nonlinearities.