Edoardo Sotgiu

Force‐based impedance control of a haptic master system for teleoperation

This paper analyzes the design of a force‐based impedance control for a haptic interface system characterized by a parallel kinematics. By exploiting the features of parallel mechanisms, which perform better than the serial ones in terms of dynamic performance, stiffness and position accuracy, and by implementing a closed‐loop force control, the transparency of a haptic master system and the fidelity of resultant force feedback can be consistently improved. Issues for design and control as well as aspects of performance evaluation of haptic interfaces are treated within the paper and some results of the experimental characterization of a haptic interface are presented.

Gravity compensation algorithms for parallel haptic interface

This paper presents an experimental comparison of different algorithms for the gravity compensation of parallel mechanisms, with special reference to a 5DOF haptic interface that has been realized at PERCRO. Two methods for the static balancing of this mechanism have been investigated: a classical method, based on Lagranges approach and an algorithm that adopts the screw theory. This last method allows solving the problem in a more intuitive way. Some experimental results are reported in order to confirm this approach.

Hand and arm ownership illusion through virtual reality physical interaction and vibrotactile stimulations

Body awareness has important implications for the use of virtual reality (VR) and its effectiveness. This involves the senses of agency and body ownership, studied in the past by producing the Rubber Hand Illusion (RHI). Recent studies reported the RHI on virtual environments (VE) by giving the participant synchronous 3D visual stimulation and passive tactile stimulation manually on the hidden real hand placed on a static position. In this paper we present a novel study of the RHI within highly dynamic VE sessions with synchronous pure virtual vibrotactile stimulation of the fingers. The hand/arm participants movements are realistically reproduced on the VE and tactile stimulations are self-inflicted by the participant through actively touching the virtual objects. The results revealed that the RHI is possible in active, dynamic and fully multisensored VE sessions.

A full upper limb robotic exoskeleton for reaching and grasping rehabilitation triggered by MI-BCI

In this paper we propose a full upper limb exoskeleton for motor rehabilitation of reaching, grasping and releasing in post-stroke patients. The presented system takes into account the hand pre-shaping for object affordability and it is driven by patients intentional control through a self-paced asynchronous Motor Imagery based Brain Computer Interface (MI-BCI). The developed antropomorphic eight DoFs exoskeleton (two DoFs for the hand, two for the wrist and four for the arm) allows full support of the manipulation activity at the level of single upper limb joint. In this study, we show the feasibility of the proposed system through experimental rehabilitation sessions conducted with three chronic post-stroke patients. Results show the potential of the proposed system for being introduced in a rehabilitation protocol.

A virtual reality system for robotic-assisted orthopedic rehabilitation of forearm and elbow fractures

The combination of robotics and virtual reality seems promising for the rehabilitation of the upper limb by promoting intensive training on specific deficits with motor control and multimodal feedback in engaging game-like scenarios. In this paper we present the integration of a robotic system and virtual reality applications for the orthopedic rehabilitation of the arm, in terms of strengthening training and motion recovery. The system simulates the upper limb of the patient and their actions, and allows exhaustive exercising and motor control, giving visuomotor and haptic feedback and trajectory positioning guidance. The system allows assign specific tasks to perform within the virtual environments and aids to evaluate the mobility condition of the patient, to personalize the difficulty level of the therapy and provides kineseologic measures of the patient evolution. We present the results of a preliminary clinical assessment we are carried out on three patients in order to assess the usability and acceptance of the system.

Modelling and Experimental Evaluation of a Static Balancing Technique for a new Horizontally Mounted 3-UPU Parallel Mechanism

This paper presents the modelling and experimental evaluation of the gravity compensation of a horizontal 3-UPU parallel mechanism. The conventional Newton-Euler method for static analysis and balancing of mechanisms works for serial robots; however, it can become computationally expensive when applied to the analysis of parallel manipulators. To overcome this difficulty, in this paper we propose an approach, based on a Lagrangian method, that is more efficient in terms of computation time. The derivation of the gravity compensation model is based on the analytical computation of the total potential energy of the system at each position of the end-effector. In order to satisfy the gravity compensation condition, the total potential energy of the system should remain constant for all of the manipulators configurations. Analytical and mechanical gravity compensation is taken into account, and the set of conditions and the system of springs are defined. Finally, employing a virtual reality environment, some experiments are carried out and the reliability and feasibility of the proposed model are evaluated in the presence and absence of the elastic components.

A wireless Bluetooth Dataglove based on a novel goniometric sensors

In this paper the design and construction of a novel wireless Dataglove based on new flexible goniometric sensor technology is described. The device is characterized by a low cost and rugged construction and no requires calibration before its use. Indeed, the sensors used are purely goniometric, so they are not sensible to dimensions of the users hand. The Dataglove can measure the angular displacement of the fingers hand using 11 sensors, each sensor has a resolution of 0.2 degrees, with 3 degree of accuracy in the worst case. The communication between the Dataglove and its computer Host is carried out using a 2,4 gigahertz wireless Bluetooth radio protocol, in a guaranteed range up to 10 meters with a refresh rate of 100 Hz.

A neuromusculoskeletal model of the human upper limb for a myoelectric exoskeleton control using a reduced number of muscles

This paper presents a myoelectric control of an arm exoskeleton designed for rehabilitation. A four-muscles-based NeuroMusculoSkeletal (NMS) model was implemented and optimized using genetic algorithms to adapt the model to different subjects. The NMS model is able to predict the shoulder and elbow torques which are used by the control algorithm to ensure a minimal force of interaction. The accuracy of the method is assessed through validation experiments conducted with two healthy subjects performing free movements along the pseudo-sagittal plane. The experiments show promising results for our approach showing its potential for being introduced in a rehabilitation protocol.

Rehabilitation training and evaluation with the L-EXOS in chronic stroke

This paper presents the results of the evaluation training performed in a group of chronic stroke patients using a robotic exoskeleton device. The effects of training were assessed both by means of clinical evaluation in terms of Fugl-Meyer and Modified Ashworth assessment scales and of functional evaluation, by means of Bimanual Activity Scale. Interestingly we found a significant improvement of both clinical and functional evaluation.

Design of an Underactuated Hand Exoskeleton with Joint Estimation

In this study, we present an underactuated hand exoskeleton with the adaptation for the shape and the size of the objects during grasping tasks. The realism of the grasping tasks are improved by allowing only the normal transmission of the forces on the finger phalanges. The absence of the tangential forces allows the device to be attached to the user’s finger in an easy and comfortable manner for the operation. Furthermore, the finger size adjustability can be ensured by the linkage-based design. Underactuation assures the automatic adjustability of the device for the grasping objects, while preventing the posture control of the finger phalanges. The undersensing disadvantage of the underactuation approach is suggested to be overcome by utilizing an additional potentiometer on the device in order to estimate the finger joints and the pose analysis of the mechanism during operation.