Abstract

Parallel robot is a kind of robot that uses several computer-controlled serial chains to support
a single platform, or end-effector (EE). It has been widely used in the various applications such as
aircraft simulator, high precision machining and aerospace manufacturing, etc. However, achieving
high precision pose control of 6-DOF parallel robot makes a challenge for robotic researchers due
to the lack of dynamic modeling of robot and accurate measurement of pose. The present research
study aims at controlling the pose of end-effector (EE) of 6-RSS parallel platform in real time.
In this thesis, the kinematics of the robot including the inverse and forward kinematics are presented.
The numerical solution of forward kinematics model is provided and the forward kinematic
model is implemented in the Simulink to serve as the parallel robot for the pose control design.
A Simulink model is built in order to simulate and implement the pose controller for the parallel
robot.
The parallel robot consists of six Brush-Less DC (BLDC) actuators. Both linear and nonlinear
dynamic models of the DC motors are derived. The parameters of linear dynamic models are
identified using Genetic Algorithm (GA). Also, the parameters of nonlinear actuators’ dynamic
model are identified using the multi-objective optimization method. Then a proportional-integralderivative
(PID) controller is used to control the EE and track the desired trajectory. The simulation
results demonstrate an outstanding tracking performance for the designed PID controller.
To further validate the designed pose controller in the real time experiment, we use the photogrammetry
sensor–C-track from Creaform Inc. to obtain the pose of EE. By comparing the
desired pose with the current measured pose by C-track, the inverse kinematic model of the parallel
robot is validated and the experimental results demonstrate that the inverse kinematic model is
accurate enough for the subsequent real time pose control.
In order to control the pose of the parallel robot, the pose measured by C-track is used to
implement the real time pose feedback control system. Since the C-track is connected to one
computer and the parallel robot is connected to a different computer, it is necessary to transfer
the obtained pose data by C-track from one PC to the other one that controls the actuators of
the parallel robot. A serial port has been used for the real time data transferring. A lot of effort
has been dedicated to the retrial of the pose data in the real time pose control Simulink blocks.
Finally, six PID controllers are applied to track the pose of the EE. The experimental results show
an acceptable pose tracking control of the system.