Abstract
This paper presents a model-based kinematic and non-kinematic calibration method for a 7R 6-DOF robot with non-spherical wrist. By using the proposed method, kinematic errors, compliance errors from external load and self-gravity are particularly compensated. Firstly, kinematic error model is built based on modified DH (MDH) model, meanwhile calibration models for compliance and inertial parameters are derived by proper linearization of stiffness model. Secondly, to derive a suitable minimal model for practical application, model reduction and parameter identifiability analysis are conducted by considering parameter properties defined in controller. Finally, a step-by-step procedure for error parameter estimation is proposed with laser tracker as measuring device: (1) kinematic parameter errors are identified when the robot is not loaded. (2) compliance parameters are identified when the robot is loaded. (3) inertial parameters are calibrated together with kinematic errors, if deformations from self-gravity need to be compensated. Simulations and experiments on a 7R 6-DOF industrial painting robot are conducted to verify that the proposed calibration method can improve accuracy of the robot under no load and loaded conditions.
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