| Fast-Tool Servo systems are electromechanical devices used on high precision manufacturing for either introducing non-rotationally symmetric features on the workpiece or to compensate for microscopic effects that degrade the performance of high precision machine tools. Currently available fast tool servos are primarily driven by piezoelectric stacks, which have a very restricted range of motion and other limitations such as nonlinear behavior, high power consumption, high cost, etc. Magnetic Servo Levitation has been proposed as a new actuation principle for fast tool servo devices that allows both wide bandwidth and a range of motion several times larger than a piezo driven device, while keeping very low power consumption. The device motion is controlled by electromagnetic attractive force, which provides significantly larger forces than Lorentz (shear) force devices, but is more difficult to control and highly nonlinear. This work describes modeling, control and related implementation issues of long-range magnetic servo levitation. A novel parametric model and several control techniques have been developed to achieve long-range fast tracking. It has been established that it is possible to achieve excellent command tracking with near zero phase lag and very low power consumption, while operating a magnetically levitated device over a wide range of travel distances and frequencies. Furthermore, machining experiments have been carried out that demonstrate the feasibility of using magnetic servo levitation to actuate fast tool servo systems. |
