An-Najah Staff

Advanced model based control schemes and the solution of the direct dynamic problem requires accurate knowledge of the dynamic parameters of robotic systems, mainly the inertial properties of the links and the friction parameters at the kinematic joints. A well known and a very useful tool for their determination is through a dynamic identification process. Normally, in this process, only a subset of the dynamic parameters of a robot, known as “base parameters”, can be identified. When parameter identification is performed experimentally, not all the aspects of the robot can be modeled in detail. Moreover, measurement variables are affected by noise. These sources of error lead to the fact that not all the base parameters can be properly identified. Therefore, in this paper, the identifiability of the dynamic parameters of a class of parallel robot, in the presence of noise in measurement and discrepancy in modeling, is addressed. The analysis is carried out by means of a simulated robot and over an actual parallel 3-RPS robot.

The issue of identification of dynamic parameters in open-chain industrial manipulators is addressed with emphasis on the physical feasibility of the identified set of parameters. The dynamic model on which the identification procedure is based considers rigid-link robots including a complete actuator dynamics modeling and is obtained starting from the Gibbs–Appell equations. Friction at the joints is also considered. The dynamic equations of the model are written linearly with respect to the dynamic parameters to be identified. The matrix form linear system is solved through a quadratic optimization procedure with non-linear constraints in order to ensure the physical feasibility of the identified parameters. The procedure is tested using a PUMA 560 industrial robot. A comparison between control actions and torques obtained from the Inverse Dynamic Problem considering identified parameters is performed in order to establish the validity of the proposed procedure. The set of physically feasible dynamic parameters is used in an integration of the equations of motion of the robot and the results of the simulation are compared with the robot actual movement.