Many collaborative robots use strain-wave-type transmissions due to their desirable characteristics of high torque capacity and\nlow weight. However, their inherent complex and nonlinear behavior introduces significant errors and uncertainties in the robot\ndynamics calibration, resulting in decreased performance for motion and force control tasks and lead-through programming\napplications. This paper presents a new method for calibrating the dynamic model of collaborative robots. The method combines\nthe known inverse dynamics identification model with the weighted least squares (IDIM-WLS) method for rigid robot dynamics\nwith complex nonlinear expressions for the rotor-side dynamics to obtain increased calibration accuracy by reducing the\nmodeling errors. The method relies on two angular position measurements per robot joint, one at each side of the strain-wave\ntransmission, to effectively compensate the rotor inertial torques and nonlinear dynamic friction that were identified in our\nprevious works. The calibrated dynamic model is cross-validated and its accuracy is compared to a model with parameters\nobtained from a CAD model. Relative improvements are in the range of 16.5% to 28.5% depending on the trajectory.
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