A Versatile FPGA based Commutation Sequence Generator for BLDC Motors

Recent trends in Radio Telescopes deploy BLDC motors for their 2-axis rotation. BLDC motors implement electronic commutation by avoiding carbon brushes and mechanical commutation. Resolvers mounted on rotor shaft of BLDC motors form good sensor feedback and work in-conjunction with RDC and FPGA interface to implement speed and position control. Brushes in DC torque form an important source of arcing and generation of considerable EMI interference noise. Such EMI interferences reduce the S/N of signals obtained from faint radio sources in Radio Telescope. Also BLDC motors gain importance as drive sources in focal plane instruments of Radio Telescopes, avoid brushes and uses electronic commutation. This approach helps in attaining enhanced sensitivity and S/N ratio. Complete FPGA based Sequence Generator is described here. FPGA based controller scheme used to provide stator voltage to BLDC motor, speed and position control of telescope. By avoiding brushes and arcing in mechanical commutation EMI interference is reduced. The focus motor of telescope gains an importance by providing better S/N from this approach. Complete hardware and software aspects of FPGA controller scheme for BLDC motor control is covered. FPGA accepts shaft position information from a syncro mounted on motor shaft and interfaced through RDC to FPGA.