Feedback linearization and simultaneous stiffness-position control of robots with antagonistic actuated joints.

In this paper, the dynamic model of a robot with antagonistic actuated joints is presented, and the problem of full linearization via static state feedback is analyzed. The use of transmission elements with nonlinear relation between the displacement and the actuated force allows to control both the position and the stiffness of each joint. The main advantage of this actuation modality is that the achieved stiffness becomes same mechanical characteristic of the system and it is not the result of an immediate control action as in the classical impedance control scheme. Different examples of implementation of this kind of devices are known in literature, even if limited to one single joint and the application of antagonistic actuated kinematic chains in the field of robotic hand design is under investigation. After a brief review of the dependence of the properties of antagonistic actuation on the transmission elements characteristics, a scheme for simultaneous stiffness-position control of the linearized system is presented. Finally, simulation results of a two-link antagonistic actuated arm are reported and discussed

A Static Intrinsically Passive Controller to Enhance Grasp Stability of Object-based Mapping between Human and Robotic Hands

Abstract — Replicating human hand capabilities on robotic hands is a great challenge in robotics. The high complexity of mechanical and actuation systems of available robotic device can be, however, considerably mitigated if a human inspired control is considered. In this paper the application of an objectbased mapping to the control of robot hands is presented. The basic idea is to use a virtual object, e.g. a virtual sphere, to capture human hand motion generating suitable reference signals for a low level controller of the robotic hand. The low level controller considered, which shares the idea of virtual object to reduce the complexity of the control, is the static Intrinsically Passive Controller (s-IPC). This controller is inspired by the dynamic IPC, but provides a simpler and more efficient implementation. The proposed approach allows to map motion of a human hand model, controlled on the reduced subspace of postural synergies, onto robotic hands guaranteeing the stability of the robotic grasp. This concept, which has been experimentally validated in the paper, can be exploit for complex planning methods or used in telemanipulation application. I

Local Online Planning of Coordinated Manipulation Motion

In this work, we deal with the problem of planning a manipulation task for a robotic system composed of at least one dexterous arm and a dexterous multi-fingered hand. The goal of the local planner is to include both, the arm and the hand, in the execution of the task in a coordinated way. This is achieved by using the workspace of the hand which is computed offline. During the online planning, the current in-hand manipulation capability is evaluated taking advantage of the dimensions of the hand workspace and considering the task itself. Dynamic weights enable the computation of the instantaneous contributions of the two subsystems on the motion of the manipulated object. The method is evaluated in simulation as well as in several experiments on the real robot