A Comparison between Theoretically Derived and Experimentally Verified Dynamic Modelling of a SCARA-Robot

Abstract

To achieve optimal use of the capabilities of a robot it has become increasingly important to include the dynamical behaviour of the robot in control strategies. In this case a dynamic model is needed for collision-free motion planning and control of two cooperating robots in an assembly cell. The two robots are of different types, an anthropomorphic type and a SCARA type. In this paper the derivation and identification of the dynamical model for the industrial Bosch SR800 TurboScara robot is described. The robot has 4 degrees of freedom of which the first two are the most important. Both these degrees consist of joints that are actuated with DC-motors and use harmonic-drives for speed reduction. In recent literature [1],[2] it is shown that the use of harmonic-drives can introduce considerable flexibility. Analyses of the actuator response after a step input shows flexibility in the first joint. This flexibility will be incorporated in the model. The model has been identified using black-box identification and parameter optimization. With the black-box model orders and rough parameter values are estimated. With a parameter optimization method the individual parameters, like link inertia, are estimated through minimizing the difference between measured and simulated time response. The use of time responses enables the individual estimation of parameters with an influence on a specific part of the respons.