High-Precision Incremental Capacitive Angle Encoder Developed by Micro Fabrication Technology

This article proposes a high-precision incremental capacitive angle encoder based on microfabrication technology. Compared to traditional printed circuit board technology, the encoder manufactured by microfabrication technology has higher processing accuracy and better temperature characteristics. Further, the microfabrication technology makes the encoder obtain larger sensitive capacitances and achieve more electrical cycle divisions within a smaller volume. To overcome the effect of the parasitic parameters led by microfabrication technology, electric models were established and analyzed, and the solution was proposed. First, to reduce the parasitic capacitance coupling to the ground, the process materials and fabrication steps are improved and optimized. Then, a differential structure on excitation voltage wires is adopted to minimize the nonlinear error on the measurement results. In addition, the collection electrode interconnection model is optimized to reduce parasitic parameters on the collection and enhance the signal to noise ratio. Both analytical calculation and finite-element analysis results verified the feasibility of the improvement and optimization. Finally, the optimized prototype is fabricated and measured, and the result shows that the prototype can achieve 0.0002° measurement resolution and 0.0012° measurement accuracy within a 58 mm diameter.