This paper presents a novel solution for the inverse kinematics of redundant space manipulators, which is aimed at\ud locally minimizing the dynamic disturbances transferred to the spacecraft during trajectory tracking maneuvers.\ud The solution is based on a constrained least-squares approach and is suitable for real-time implementation. To\ud formulate the problem as a function of dynamic variables, the inverse kinematics at the acceleration level is\ud considered. The proposed solution is introduced in the context of a more general theory, including the classical\ud pseudoinverse, the extended task-space, and the task priority solutions. Moreover, the introduction of joint\ud acceleration constraints in order to take into account the physical limits of the manipulator joints and the relaxing of\ud the end-effector tracking requirements have been studied, and their influence on the minimization performance has\ud been assessed. The experimental validation of the proposed solutions, with an insight on the effect of joint flexibility\ud on their performance, has been carried out for a planar three-degrees-of-freedom manipulator. Two test cases have\ud been considered, in which the number of force and torque reaction components to be controlled are equal to or\ud greater than the available degree of redundancy

Motion-planning algorithms play a vital role in attaining various levels of autonomy for any ground or flying agent. Three-dimensional (3D) motion-planning is interesting, but rather complex, especially for flying agents such as autonomous unmanned aerial vehicles (UAVs), due to the increased dimensionality of space and consideration of dynamical constraints for a feasible trajectory. Usually, in 3D path search problems, it is hard to avoid extra expanded nodes due to increased dimensionality with various available search options. Therefore, this paper discusses and implements a modified heuristic-based A* formalism that uses a truncation mechanism in order to eradicate the mentioned problem. In this formalism, the complete motion planning is divided into shortest path search problem and smooth trajectory generation. The shortest path search problem is subdivided into an initial naïve guess of the path and the truncation of the extra nodes. To find a naïve shortest path, a conventional two-dimensional (2D) A* algorithm is augmented for 3D space with six-sided search. This approach led to the inclusion of extra expanded nodes and, therefore, it is not the shortest one. Hence, a truncation algorithm is developed to further process this path in order to truncate the extra expanded nodes and then to shorten the path length. This new approach significantly reduces the path length and renders only those nodes that are obstacle-free. The latter is ensured using a collision detection algorithm during the truncation process. Subsequently, the nodes of this shortened path are used to generate a dynamically feasible and optimal trajectory for the quadrotor UAV. Optimal trajectory generation requires that the plant dynamics must be differentially flat. Therefore, the corresponding proof is presented to ensure generation of the optimal trajectory. This optimal trajectory minimizes the control effort and ensures longer endurance. Moreover, quadrotor model and controllers are derived as preliminaries, which are subsequently used to track the desired trajectory generated by the trajectory planner. Finally, results of numerical simulations which ultimately validate the theoretical developments are presented.

The stiffness properties of industrial robots are very important for many industrial applications, such as automatic robotic assembly and material removal processes (e.g., machining and deburring). On the one hand, in robotic assembly, joint compliance can be useful for compensating dimensional errors in the parts to be assembled; on the other hand, in material removal processes, a high Cartesian stiffness of the end-effector is required. Moreover, low frequency chatter vibrations can be induced when low-stiffness robots are used, with an impairment in the quality of the machined surface. In this paper, a compliant joint dynamic model of an industrial robot has been developed, in which joint stiffness has been experimentally identified using a modal approach. First, a novel method to select the test configurations has been developed, so that in each configuration the mode of vibration that chiefly involves only one joint is excited. Then, experimental tests are carried out in the selected configurations in order to identify joint stiffness. Finally, the developed dynamic model of the robot is used to predict the variation of the natural frequencies in the workspace.

This paper presents investigations toward the development of an inflated deformable rolling rover. The proposed novel locomotion system could find potential future use, for example, in scouting and exploration missions. The manufacturing procedure used to fabricate a preliminary prototype is presented in this paper. The prototype consists of a rigid frame and four dielectric elastomer actuator (DEA) sectors, which give the prototype a spherical shape. Analytical models are proposed to predict the electromechanical behavior of the DEA sectors and to estimate their effect on the prototype's dynamics. These models are validated through an experimental procedure.