Damiano Zanotto

The value of robotic systems in stroke rehabilitation

In this paper, we discuss robot-mediated neurorehabilitation as a significant emerging field in clinical medicine. Stroke rehabilitation is advancing toward more integrated processes, using robotics to facilitate this integration. Rehabilitation approaches have tremendous value in reducing long-term impairments in stroke patients during hospitalization and after discharge, of which robotic systems are a new modality that can provide more effective rehabilitation. The function of robotics in rehabilitative interventions has been examined extensively, generating positive yet not completely satisfactory clinical results. This article presents state-of-the-art robotic systems and their prospective function in poststroke rehabilitation of the upper and lower limbs.

Effects of Complementary Auditory Feedback in Robot-Assisted Lower Extremity Motor Adaptation

This study investigates how complementary auditory feedback may affect short-term gait modifications induced by four training sessions with a robotic exoskeleton. Healthy subjects walked on a treadmill and were instructed to match a modified gait pattern derived from their natural one, while receiving assistance by the robot (kinetic guidance). The main question we wanted to answer is whether the most commonly used combination of feedback (i.e., haptic and visual) could be either enhanced by adding auditory feedback or successfully substituted with a combination of kinetic guidance and auditory feedback. Participants were randomly assigned to one of four groups, all of which received kinetic guidance. The control group received additional visual feedback, while the three experimental groups were each provided with a different modality of auditory feedback. The third experimental group also received the same visual feedback as the control group. Differences among the training modalities in gait kinematics, timing and symmetry were assessed in three post-training sessions.

Sophia-3: A Semiadaptive Cable-Driven Rehabilitation Device With a Tilting Working Plane

Sophia-3 (string-operated planar haptic interface for arm rehabilitation) is a planar cable-driven device with a tilting working plane. It represents the first application of the adaptive cable-driven design paradigm recently introduced by the authors, featuring a moving pulley-block that allows the robot to achieve excellent force capabilities, despite the low number of cables. This study presents the design, kinematics, and control of the device and results of experimental validation on healthy subjects.

Knee Joint Misalignment in Exoskeletons for the Lower Extremities: Effects on User's Gait

Due to the complexity of the human musculoskeletal system and intra/intersubjects variability, powered exoskeletons are prone to human-robot misalignments. These induce undesired interaction forces that may jeopardize safe operation. Uncompensated inertia of the robotic links also generates spurious interaction forces. Current design approaches to compensate for misalignments rely on the use of auxiliary passive degrees of freedom that unavoidably increase robot inertia, which potentially affects their effectiveness in reducing undesired interaction forces. Assessing the relative impact of misalignment and robot inertia on the wearer can, therefore, provide useful insights on how to improve the effectiveness of such approaches, especially in those situations where the dynamics of the movement are quasi-periodic and, therefore, predictable such as in gait. In this paper, we studied the effects of knee joint misalignments on the wearers gait, by using a treadmill-based exoskeleton developed by our group, the ALEX II. Knee joint misalignments were purposely introduced by adjusting the mismatch between the length of the robot thigh and that of the human thigh. The amount of robot inertia reflected to the user was adjusted through control. Results evidenced that knee misalignment significantly changes human-robot interaction forces, especially at the thigh interface, and this effect can be attenuated by actively compensating for robot inertia. Misalignments caused by an excessively long robot thigh are less critical than misalignments of equal magnitude deriving from an excessively short robot thigh.

Adaptive assist-as-needed controller to improve gait symmetry in robot-assisted gait training

This paper introduces the overall design of ALEX III, the third generation of Active Leg Exoskeletons developed by our group. ALEX III is the first treadmill-based rehabilitation robot featuring 12 actively controlled degrees of freedom (DOF): 4 at the pelvis and 4 at each leg. As a first application of the device, we present an adaptive controller aimed to improve gait symmetry in hemiparetic subjects. The controller continuously modulates the assistive force applied to the impaired leg, based on the outputs of kernel-based non-linear filters, which learn the movements of the healthy leg. To test the effectiveness of the controller, we induced asymmetry in the gait of three young healthy subjects adding ankle weights (2.3kg). Results on kinematic data showed that gait symmetry was recovered when the controller was active.

Design and control of two planar cable-driven robots for upper-limb neurorehabilitation

Post-stroke robot-aided neurorehabilitation is an emerging research field, aiming to improve the intensity and the effectiveness of post-stroke rehabilitation protocols by using robotic technology and virtual reality. One classification that has been proposed for therapy robots is between exoskeletons and end-effector based machines. The latter are those devices whose interaction with the patients arm takes place at the end-effector level. This paper presents the design of two novel end-effector based robots for upper-limb rehabilitation, named Sophia-4 and Sophia-3. Although the devices are based on a common concept (the cable-drive actuation over a planar workspace), the latter differs from the former by the number of employed cables (4 and 3, respectively), and, by several design solutions, such as the introduction of a moving pulley-block to enhance workspace and a tilting table to better target the patients shoulder. Both mechanical and control system design are addressed and a comparison of performances is presented.

Modeling and Control of a 3-DOF pendulum-like manipulator

This work deals with the kinematic and dynamic modeling of a 3-DOF, under-actuated, pendulum-like manipulator and its control system. The cable-based device is capable of completing point-to-point planar motions, driving the end-effector from a starting pose to a goal pose, by means of two actuators only. The device relies on parametric excitation to control the oscillations of the variable-length pendulum. Unlike a previous work [1], the dynamic model introduced here is consistent with the assumption of cable-based device. Several control strategies are compared through numerical simulations.

Planar Robotic Systems for Upper-Limb Post-Stroke Rehabilitation

Rehabilitation is the only way to promote recovery of lost function in post-stroke hemiplegic subjects, leading to independence and early reintegration into social and domestic life. In particular, upper limb rehabilitation is fundamental to regain ability in Activities of Daily Living (ADLs). Robot-aided rehabilitation is an emerging field seeking to employ leading-edge robotic systems to increase patient recovery in the rehabilitation treatment. Even though the effectiveness of robotic therapy is still being discussed, the use of robotic devices can increase therapists’ efficiency by alleviating the labor-intensive aspects of physical rehabilitation, and can produce a reduction in treatment costs. This paper presents a comparison between different planar robotic devices designed for upper-limb rehabilitation in chronic patients. A planar configuration of the workspace leads to straightforward mechanical and control system design, and allows to define very simple and understandable treatment exercises. Also, the graphical user interface becomes very intuitive for the patient, and a set of Cartesian-based measures of the patient’s performance can be defined easily. In the paper, SCARA (Selective Compliance Assembly Robot Arm) robots such as the MIT-Manus, Cartesian robots and cable-driven robots are considered and compared in terms of inertial properties and force exertion capabilities. Two cable-driven devices, designed at the Robotics Lab of the Department if Innovation In Mechanics and Management, University of Padua, Italy, are presented for the first time. The first robot employs four driven cables to produce a planar force on the end-effector, whereas the second one is based on a three-cable configuration plus a linear actuator to obtain better overall robot performance.© 2008 ASME

ALEX III: A novel robotic platform with 12 DOFs for human gait training

ALEX III is a bilateral exoskeleton for gait rehabilitation. It is an evolution of two previous prototypes - ALEX and ALEX II - developed at the University of Delaware. The new robot comprises a support platform and two robotic legs. Its unique characteristic is the possibility to actively control 12 degrees-of-freedom: 4 at the pelvis and 4 for each leg. This paper focuses on the design and fabrication of the robotic leg. Results from early evaluations are presented where the robotic leg is attached to a fixed frame and controlled with a zero-interaction controller.

Reducing muscle effort in walking through powered exoskeletons

This paper presents a novel assistive control for lower limb exoskeletons. The controller provides the user with a scaled version of the Winters nominal torque profile, which is adapted online to the specific gait features of the user. The proposed assistive controller is implemented on the ALEX II exoskeleton and tested on two healthy subjects. Experimental results show that when assisted by the exoskeleton users can reduce the muscle effort compared to free walking.