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Error Analysis and Adaptive-Robust Control of a 6-DoF Parallel Robot with Ball-Screw Drive Actuators


Affiliations
1 Dipartimento di Meccanica, Politecnico di Milano, Campus Bovisa Sud, Via La Masa 1, 20156 Milano, Italy
2 Dipartimento di Ingegneria Industriale e dell’Informazione, Universita degli Studi di Pavia, Via A. Ferrata 5, 27100 Pavia, Italy
 

Parallel kinematic machines (PKMs) are commonly used for tasks that require high precision and stiffness. In this sense, the rigidity of the drive system of the robot, which is composed of actuators and transmissions, plays a fundamental role. In this paper, ball-screw drive actuators are considered and a 6-degree of freedom(DoF) parallel robot with prismatic actuated joints is used as application case. A mathematical model of the ball-screw drive is proposed considering the most influencing sources of nonlinearity: sliding-dependent flexibility, backlash, and friction. Using this model, the most critical poses of the robot with respect to the kinematic mapping of the error from the joint- to the task-space are systematically investigated to obtain the work space positional and rotational resolution, apart from control issues. Finally, a nonlinear adaptive-robust control algorithm for trajectory tracking, based on the minimization of the tracking error, is described and simulated.
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  • Error Analysis and Adaptive-Robust Control of a 6-DoF Parallel Robot with Ball-Screw Drive Actuators

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Authors

Navid Negahbani
Dipartimento di Meccanica, Politecnico di Milano, Campus Bovisa Sud, Via La Masa 1, 20156 Milano, Italy
Hermes Giberti
Dipartimento di Ingegneria Industriale e dell’Informazione, Universita degli Studi di Pavia, Via A. Ferrata 5, 27100 Pavia, Italy
Enrico Fiore
Dipartimento di Meccanica, Politecnico di Milano, Campus Bovisa Sud, Via La Masa 1, 20156 Milano, Italy

Abstract


Parallel kinematic machines (PKMs) are commonly used for tasks that require high precision and stiffness. In this sense, the rigidity of the drive system of the robot, which is composed of actuators and transmissions, plays a fundamental role. In this paper, ball-screw drive actuators are considered and a 6-degree of freedom(DoF) parallel robot with prismatic actuated joints is used as application case. A mathematical model of the ball-screw drive is proposed considering the most influencing sources of nonlinearity: sliding-dependent flexibility, backlash, and friction. Using this model, the most critical poses of the robot with respect to the kinematic mapping of the error from the joint- to the task-space are systematically investigated to obtain the work space positional and rotational resolution, apart from control issues. Finally, a nonlinear adaptive-robust control algorithm for trajectory tracking, based on the minimization of the tracking error, is described and simulated.