Passivity-Based Control of Delta Robot for Trajectory tracking
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Date
2021-11
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Addis Ababa University
Abstract
Parallel manipulators have some special properties in comparison to serial robots,
making them increasingly appealing in industrial applications as technology advances.
such as: more rigid structure, high orientation accuracy, better control on
the limits of velocities and accelerations, good positioning accuracy, high payloadto-
weight-ratio and low inertia of moving parts. On the other hand, parallel
robots are nonlinear multi-input multi-output (MIMO) systems whose dynamics
are governed by a highly nonlinear coupled, time-varying system with many
uncertainties such as load variation, friction and external disturbances, making
robot control more di cult and necessitating a robust control system.
This thesis provides passivity-based control as one of the strategies for designing
robust controllers for a 3-DOF Delta Robot trajectory tracking. Passivity is a
fundamental attribute of many physical systems that may be nearly characterized
in terms of energy dissipation and transformation and its intrinsic input output
property quanti es and de nes a system’s energy balance when external inputs
imitate to produce some outputs. Furthermore, it is a method of operating a
system with the goal of making the closed loop system passive. The 3-D model of
a 3-DOF Delta robot is designed in 3D-CAD (Solidworks). Hence, this modeling
environment enables to introduce real but not approximated parameters of the
robot and eased computation of large matrixes. Dynamical model with all the
kinematic constraints for a robot will simply be found by exporting a 3D-CAD
model of the robot to Simscape Multibody.
The kinematics, dynamics and singularity analysis of the 3-DOF Delta robot has
been carried out, a passivity based controller has been designed and its performance
is tested by tracking a circular trajectory centered at (15,15,/0) on X-Y plane
with 160mm radius. The simulation result shows that the steady state tracking is
reached in about 3 seconds for a circular trajectory and X & Y rms error of 2.88mm.The robustness of the designed controller is illustrated mathematically and the
simulation is carried out on MATLAB, and it shows that the controller is robust to
external disturbances.
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Keywords
Passivity Based Control (PBC), 3D CAD (solidworks) model of Delta Robot, 3-DOF Delta Robot, MATLAB/Simulink