Application of frequency domain multiplexing for the reduction of ADCs in vector control of PMSM

This paper describes the application of frequency domain multiplexing (FDM) to reduce the number of analog-to-digital converters (ADC) used in vector control of a permanent magnet synchronous motor (PMSM), when a resolver sensor is used as position transducer. The signals of the current sensors and the resolver sensor can have different bandwidths by selecting properly the excitation frequency of the position sensor and the switching frequency of the inverter, allowing an easy implementation of FDM. Two new signals are conformed by the combination of the outputs of the current sensors with those that belong to the resolver sensor. A set of digital filters allows the reconstruction of the original signals. As a result, only two ADCs are needed to get the current and the position signals, by using FDM. This fact reduces the complexity of the signal conditioning system, simplifies the implementation of vector control in processors as FPGAs and ASICs, which do not have implicit ADCs, and allows working with cheaper DSPs. Simulations and experimental results show that FDM can be successfully used in vector control of PMSM.