A novel approach of using a planar inductive position sensor for the Permanent magnet synchronous motor control application

Permanent magnet synchronous motors (PMSM) are taking over the commercial, industrial (robotics) and automotive industry. Most of the applications demand high starting torque at zero speed. For generating the desired amount of torque at zero speed, accurate rotor position information is necessary, which is obtained by using position sensors. Hall sensors with digital output are sensitive to temperature and external magnetic fields and do not offer high resolution. Optical encoders provide good resolution but lead to higher cost and reliability related issues in the harsh/contaminated environment. Inductive sensing technology is an emerging technology which can be used in wide range of application such as proximity, angular displacement, linear displacement etc. PMSM control is one such application that can make use of planar Inductive position sensors which are contactless sensors, works on LVDT principle. These can be inexpensively built with stationary printed circuit board PCB coils and metal target. Inductive sensors are absolute devices which mean that they need no motion at power up to determine position. This paper covers planar inductive position sensor and its usage in PMSM control application. The experiments are carried out to substantiate the proposed technique in the speed controlled drive system of PMSM.