Kinematics and workspace analysis of a 3DOF parallel reconfigurable robot

Parallel robots are widely used in many industrial and medical applications. Reconfigurable parallel robots could be defined as a group of parallel robots that can have different geometries, thus obtaining different degrees of freedom derived from the basic structure. These robots have some disadvantages like having erratic workspace and singular points in the workspace. These limitations should be studied for proper usage of parallel manipulators. This paper presents the kinematics and workspace analysis of a 3DOF parallel reconfigurable robot. This robot has two different configurations. The first configuration is a Tricept robot (3UPS-PU) and the second is a fully Spherical robot (3UPS-S). The kinematic equations are derived based on the geometry of the system and then Jacobian matrices are determined via velocity loop closure analysis. The kinematic model is verified by the results obtained from robot simulation in ADAMS software. Then, the workspace of the robot is determined by considering the kinematic constraints

A QFT robust controller as a remedy for TRMS

Control of a Twin Rotor Multi-input Multi-output System (TRMS) is not a simple work. Because it has complex nonlinear dynamics, cross-coupling, uncertainties, and instability. This paper provides a practical method for control of a TRMS, named Quantitative Feedback Theory (QFT) as one of the robust approaches. Firstly, the TRMS set and modeling procedure are introduced. Secondly, the nonlinear and linear equations of electrical and mechanical parts in both vertical and horizontal planes are presented. Next, using the QFT method, a controller is designed for motion in each plane. Finally, the robustness of the control strategy is illustrated by simulations of vertical and horizontal motions, including controller and pre-filter in the presence of uncertainties. The results demonstrate that the proposed robust controller can guarantee the system stabilization, as well as pitch and yaw tracking of TRMS