This work presents the development and the preliminary experimental assessment of a novel EMG-driven robotic hand exoskeleton for bilateral active training of grasp motion in stroke. The system allows to control the grasping force required to lift a real object with an impaired hand, through the active guidance provided by a hand active exoskeleton, whose force is modulated by the EMG readings acquired on the opposite unimpaired arm. To estimate the grasping force, the system makes use of surface EMG recordings during grasping, developed on the opposite unimpaired arm, and of a neural network to classify the information. The design, integration and experimental characterization of the system during the grasp of two cylindrical objects is presented. The experimental results show that an optimal force tracking of the interaction force with the object can be achieved.

A conically shaped Dielectric Elastomer (DE) linear actuator is presented which is obtained by coupling a DE film with a compliant mechanism. The compliant mechanism is designed, by means of a pseudo-rigid-body model, to suitably modify the force generated by the elastomer film. The resulting actuator provides a nearly constant force along the entire actuator stroke when the DE film is activated and returns to an initial rest position when the DE film is deactivated. Experimental activity fully validates the proposed concept. Possible applications of this kind of actuator are Braille cells, light weight robots and haptic devices.

This paper presents an optimization procedure conceived to design parallel mechanisms (PMs) with legs of constant and/or variable length connected, at their endpoints, to a fixed base and a movable platform through universal and spherical joints, respectively. In the proposed procedure, the first natural frequency of the mechanism is the objective function to be maximized. The optimization problem is formulated by using dimensionless variables in order to identify the optimal geometry independently of mechanism size, platform density, and leg cross-sectional area and material. As a case study, the procedure is employed to find the optimal geometry of a 2-DOF spherical PM to be used as an orienting device in future space missions.

This paper deals with a class of over-constrained parallel manipulators that can be obtained from architecturally singular parallel mechanisms with legs of type US (U and S stand for universal and spherical joints respectively) by the addition of legs of type UPS (P stands for actuated prismatic pair). These manipulators can be internally preloaded in order to tune the system stiffness, to diminish system backlash and to control the state of tension of their structural elements. The paper, in particular, addresses the static and stiffness analyses of this class of manipulators. A symmetric stiffness matrix defined as the Hessian of the elastic potential energy of the system is used, as an alternative to the Cartesian stiffness matrix used in this field, to describe the stiffness characteristic of these manipulators. An over-constrained 2-dof parallel spherical wrist is analyzed as a case study.

We present a mechanical design for a humanoid robotic shoulder complex. The aim of the mechanism is to support the load of the arm and to copy four principal motions of the human shoulder in order to furnish the desired arm mobility and reachability. We utilize a fully parallel mechanism with four driven legs that provide to the movable platform (on which the arm is to be attached) three rotations and one translation. These three rotations represent the shoulder's flexion-extension (about the vertical axis), the shoulder's abduction-adduction (about the anterior-posterior axis), and the shoulder's rotation (about the medial-lateral axis). The fourth degree of freedom is controlled depending on the angles of the first two rotations and represents the shoulder contraction and enlargement along the medial-lateral axis.

The authors proposed methods: (i) for determination of special link positions, (ii) computer aided simulation and identification of manipulator configurations and (iii) execution of prescribed trajectories. Examples of application are given for the Cincinnati Milacron Manipulator and Unimation Puma Manipulator.