چكيده به لاتين
This thesis presents the subject of combining two robotic systems, a wheeled mobile robot and an under-constrained 6DOF cable robot. In this regard, at the first step, the kinematic and dynamic equations of the cable robot with wheeled platform are derived. The dynamic interaction between the two robotic parts, i.e. the cable robot and the wheeled mobile robot, is observable in the governing equations of the system. Considering non-holonomic constraints in the equations of the wheeled platform, the internal dynamics appears in the equations. It is shown that the closed loop equations are input–output feedback linearizable. In situations where the platform trajectory is not given, the desired platform trajectory is designed using the proposed path planning method and the desired end-effector trajectory.
This research compares a number of control methods of the flexible systems in terms of computation load and required sensors. Using a rigid-model based controller, singular perturbation technique and Lyapunov stability criterion, the condition which guarantees the system stability is spcified. In order to suppress the end-effector vibration, utilizing the Input Shaping method to prevent excitement of the system natural modes is presented. The performance of the rigid controller with the shaped input compared with the composite controller, which uses the end-effector pose feedback in addition to the actuators feedback, is shown by simulation. This evaluation is performed using a new defined index, indicating the vibration reduction ratio. Furthermore, the governing equations of the flexible cable robot with wheeled mobile platform are obtained and the stability condition of this system is investigated. For the system control, the optimized gains are determined based on the trade-off between the control input and the system error. For the obstacle avoidance task of the wheeled platform, the correction algorithm of the control gains using the potential field method is presented.
Manufacturing an under-constrained 6-DOF cable-driven parallel robot with wheeled mobile platform is accomplished for validating the simulation results. Communication of the computer with the sensors and the drivers is performed using a number of micro-controllers. In order to evaluate the effectiveness of the control approach for the wheeled mobile cable robot, the simulation results of a trajectory tracking are compared with experimental test. For validating the vibration reduction approach using the input shaping method, the accelerometer and gyro sensor data are investigated in the time and frequency domains.
In addition, the relative effect of the cable stiffness and the end-effector position in the workspace on the system vibration characteristics is specified. This investigation is carried out by sensitivity analysis of the criteria of the system natural frequency, residual kinetic energy and the end-effector position error, using Sobol method.
Keywords: Flexible Cable Robot, Wheeled Mobile Robot, Feedback Linearization, Input Shaping, Sensitivity Analysis
