AC magnetic field detection system applied to motion tracking

In the context of motion tracking and virtual reality, there is a strong need for sensors to monitor the motion of a moving object. These sensors are characterised by their performances (ranges, accuracy, drifts, and susceptibility to the ambient environment) and embedded (small size, light weight). The magnetic technology compared to the mechanical or optical solution allows the working without structural skeleton composed of links interconnected by monitored joints and with possible optical shadows. The principle of an AC magnetic field detection system is to generate an AC magnetic field with a reference coil (generally in the stationary frame), and to receive the signals with a sensing coil (generally in the moving frame). The analysis of the signals received allows retrieving the position of the sensing coil with reference to the emitting coil. This detection technique comes with the need of ultra low-noise and mixed-signals electronics to receive and sample the signals, and power electronics to generate the AC magnetic field. It also requires the use of small size emitting and sensing coils. In the frame of the SURGIMAG project supported by the French global competitive cluster MINALOGIC, Cedrat Technologies has developed the electronics and the magnetic transducers to complete such a detection chain. A 6 DOF (Degrees Of Freedom) AC magnetic field detection system is presented in this paper.