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Cartesian space computed torque control for planar parallel kinematic machines using visual servoing

Grant number: 15/25936-4
Support type:Scholarships in Brazil - Master
Effective date (Start): April 01, 2016
Effective date (End): March 31, 2018
Field of knowledge:Engineering - Mechanical Engineering
Principal Investigator:Maira Martins da Silva
Grantee:Fernanda Thaís Colombo
Home Institution: Escola de Engenharia de São Carlos (EESC). Universidade de São Paulo (USP). São Carlos , SP, Brazil

Abstract

Classical control strategies for robotic manipulators have to be revisited when dealing with the design of parallel kinematic manipulators. Among these strategies, two strategies should be considered: (i) joint space computed torque control and (ii) Cartesian space computed torque control. The first strategy (i) requires the calculation of inverse kinematics of the manipulator since the feedback control is performed by using the actual position of the active joints. This strategy, which is widely employed in serial manipulators, may not be suitable for parallel manipulators due to the complexity of the required calculations. This complexity imposes serious difficulties for the controller design such as: lack of speed and performance, stability issues, among others. The second strategy (ii) requires the measurement of the position of the end-effector since because the feedback control strategy is based on this measurement. Thus, although mathematically simpler, this choice imposes a significant technical challenge: the measurement of the end-effector. In this research project, Cartesian space computed torque control is going to be exploited numerically and experimentally in a planar parallel kinematic manipulator. Aiming that, the position of the end-effector is estimated from a fixed camera in the workspace, and image processing algorithms. The experimental evaluation of this proposal will be carried out on a prototype recently built with funds provided by FAPESP2014/01809-0. This prototype, denoted as 3RRR, consists of a planar parallel manipulator with three kinematic chains actuated by three rotational motors. This research project aims to contribute to the evolution of the controller design for parallel kinematic manipulators, since experimental results in the literature are still scarce due to technical difficulties.