Accurate Motor Current Sensing for Fine Torque Control of Actuators in Robotic Arms

Accurate measurement of motor current is essential for fine current control and in turn torque control of actuators. The paper presents a current sensing scheme suited for motion control of robotic actuators driven by a three-phase BLDC motor. A low-side current sensing scheme with a triple current sensor is employed to acquire the motor current rather than the commonly used methods with the single current sensor. The method demonstrated in this paper provides accurate measurement of motor current with minimum hardware resources. Various practical aspects affecting the current measurements are discussed. The efficacy of the scheme is evaluated by acquiring motor current data using a microcontroller and comparing it against the actual current flowing through the motor.