Motion control systems, which typically control the position of stage or actuator, are sometimes tasked to provide both position and force control. These systems work in a dual mode, where the motion controller either controls the position or the force applied. In force-control mode, the motion stage must apply a controlled force while the position can vary. In position control mode, the stage position is controlled via closed-loop servo, using a position encoder as feedback. When coupled with a direct-drive linear motor, the lack of friction in an air bearing means that the driving system (motor, controller, drive) can transduce electrical current directly into applied force. The absence of friction in the bearing means that no parasitic forces are present, and force can be directly controlled via the closed-loop servo, without the need for an external force sensor. Read more
