Huang, YanlinYanlinHuangLiang, ChiahaoChiahaoLiangChen, BohaoBohaoChenCHAO-CHIEH LAN2025-09-242025-09-242021https://www.scopus.com/inward/record.uri?eid=2-s2.0-85112096336&doi=10.1109%2FACCESS.2021.3094506&partnerID=40&md5=4aa50fd6d7000f6f388cbe307729f5d4https://scholars.lib.ntu.edu.tw/handle/123456789/732490Actuators that can generate controllable compliant output motion are suitable for robots that need to interact safely with humans or the environment. To obtain the accurate output torque required to control the compliant motion, existing robotic actuators use one or more sensors to measure the deformation of a stiff or compliant element between the actuator and the output. The complexity, reliability, and cost of sensors are the current challenges. Deformation-based sensing also suffers from limited bandwidth and stability range. This paper proposes a torque-sensorless control method of stepper motors to generate compliant motion. Stepper motors are used because of their low cost and reliability. They also have a much higher torque-to-weight ratio and torque-to-rotor-inertia ratio than other DC motors. Torque and impedance controllers based on stepper motor current feedback are developed. Torque-sensorless impedance, and gripping force control experiments are provided to show the advantages of the proposed method. It is expected that the new control method for stepper motors can offer a competitive alternative when cost, stability, or bandwidth of complaint actuators are the major concerns.Compliant MotionFriction CompensationGripping Force ControlHarmonic DrivePhase CurrentStepper MotorTorque-sensorless ControlActuatorsBandwidthCostsDc MotorsDeformationMotion ControlStepping MotorsTorqueTorque ControlComplaint ActuatorsCompliant MotionControl ExperimentsControl MethodsImpedance ControllersLimited BandwidthRobotic ActuatorsSensorless Control MethodSensorless Control[SDGs]SDG7journal article10.1109/ACCESS.2021.30945062-s2.0-85112096336