A surgical robotic arm includes an instrument having a coupler rotatable about a longitudinal axis, the coupler including: a drive screw; a drive nut threadably coupled to the drive screw, the drive nut movable along the longitudinal axis in response to rotation of the drive screw; and a drive member coupled to the drive nut and movable in response to movement of the drive nut. The surgical robotic arm also includes an instrument drive unit having: a motor configured to engage the coupler and rotate about the longitudinal axis to rotate the coupler and the drive screw; one or more sensors configured to measure one or more properties of the motor; and a controller coupled to the sensor(s) and the motor. The controller is configured to control the motor based on the property of the motor.