A robust method for stepper motor stall detection

This paper presents a robust method for stall detection of stepper motors controlled in open loop. The open loop control type eliminates the need for feedback sensors, and since the cost reduction is a continuous demand in industrial applications, the open loop stepper motors remain suitable in many practical application fields. The main disadvantage of the open loop control mode is the steps lost followed by the motor stall. The proposed method estimates in real-time the motor speed, based on motor currents and voltages measurements. The estimated speed is compared with the speed command, and stall error protection is signalized if the error exceeds a certain range. The detection has been implemented on a digital intelligent servo drive. The experimental results obtained for different stepper motors, in various situations, show that the proposed method detects effectively the motor stall moment.