Resolution Improvement of a Capacitive-type linear Encoder with Untethered Slider

In this paper, an improved sample of capacitive-type linear encoder with untethered slider is presented that has higher resolution and lower error. This encoder has a simple structure consisting of two main parts, stator and slider. Both parts are made of hard PCB. The stator has a sequence of four-phase receiver electrodes and the slider contains two-phase transmitter electrodes. The electrical energy is supplied to transmitter electrodes by the electrostatic induction. Therefore, there is no need to connect any wire to the slider. These features make the encoder to use in limited spaces. By improving resolusion, smooth and precise movement of motors is facilitated in the closed loop systems. Thus, the improved encoder is equipped with two ground electrodes between the receiver electrodes and induction electrodes on the stator board to reduce electrostatic interface between these electrodes. As, output error goes down. In addition, the step of electrodes are reduced to increase resolution. Making an experimental sample of improved encoder and testing it, showed 15µm error in 1µm resolution. This indicates, the error and resolution are improved than the previous one.