A low-cost sensorless technique for load torque estimation in a hybrid stepping motor

This paper presents a method of torque measurement in a hybrid stepping mot or without the use of speed or position sensors. It is shown that torque ri pple can be minimized by appropriate shaping of the phase-current pulses an d that efficiency can be maximized when the level of mechanical load applie d to the shaft is known. A controller is described which generates a signal related to the mechanical load by observation of the phase-current profile using a novel low-complexity technique. Practical results are presented, s howing the torque estimation relative to measured torque.