NESM-γ: An Upper-Limb Exoskeleton With Compliant Actuators for Clinical Deployment

Abstract

This letter describes the design and characterization of an upper-limb exoskeleton for post-stroke rehabilitation. The platform interacts with the shoulder and elbow of the user through four active joints, driven by series elastic actuators (SEAs) with custom springs to achieve compactness and ease of maintenance. The exoskeleton adopts a passive kinematic chain for aligning the user's and robot joints' rotation axes, and a quick flipping mechanism to enable dualside use. The pole-placement method based on the dynamic model of the SEA was used to design the low-level controller, to guarantee torque control precision and stability. The joint load due to the robot's gravity is counteracted by using a feedforward gravity compensation algorithm. Experimental characterization demonstrates the torque control bandwidth up to 10 Hz and highly transparent behavior of the joints (namely, close to null parasitic impedance) at least up to 2 Hz, showing suitability for rehabilitation purposes.

Asymmetric Bimanual ADL Training With Underactuated Exoskeleton Using Independent Joint Control and Visual Guidance

“…Regarding research significance, the proposed control framework benefits various exoskeleton designs since it independently controls the active joints' movement. For example, redundantly-actuated exoskeletons like Harmony [18], ARMin [19], CURER [34], and NESM-γ [35]; underactuated exoskeletons with passive joints like UULE [24], ASSISTON-SE [20], and NESM [21]; and wearable exoskeletons with fewer DoFs like Elbow-Wrist Exoskeleton [36] and portable shoulder exoskeleton [37]. Also, it is not required to have any specific and complicated controller for different kinds of exoskeletons.…”

Self-Aligning Finger Exoskeleton for the Mobilization of the Metacarpophalangeal Joint

“…signal, feeding a current input 𝑢 to the motor driver. The controller has been designed via a pole-placement method, based on the identification of the open-loop transfer function as in [24]. It contains an integrator to nullify steady-state errors and the gain 𝐺 𝑐 is chosen to have all closed-loop poles on the negative real axis in the complex plane.…”

A Self-Aligning Upper-Limb Exoskeleton Preserving Natural Shoulder Movements: Kinematic Compatibility Analysis

“…The NESM- features a shoulder-elbow module to support GH abduction/adduction (sA/A), flexion/extension (sF/E), internal/external rotation (sI/E), and elbow flexion/extension (eF/E) movements via series-elastic actuators (SEAs) in a reaction force-sensing configuration [25]. Each SEA unit contains a brushless DC motor, a Harmonic Drive reducer, and a custom hollow torsional spring.…”

“…This paper presents the kinematic design and experimental assessment of the kinematic compatibility of a novel exoskeleton, i.e., NEUROExos Shoulder-elbow Module - (NESM- Fig. 1), for the physical motor-function training of post-stroke patients [25]. The kinematic chain has been designed to actively mobilize the GH joint and passively align the CoRs of the robot and human joints in the 3D space, also accounting for deviations of the user's trunk pose.…”