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In a previous study, a tethered pelvic-assist device (TPAD) was used to successfully retrain crouch gait in children with cerebral palsy by applying a downward force on the pelvis while walking on a treadmill. While the results of this study were promising, an important issue was to translate this training to the children in a more practical manner. This motivated the question in this letter whether a different intervention could result in similar improvements in the gait as seen with the TPAD. This is the motivation for this study, which compares the biomechanical differences in walking under the following two conditions. 1) The TPAD applies a pure downward force on the pelvis using tethers. 2) A weighted pelvic belt is used to apply the same downward force on the pelvis. In this case, the weight belt also increases the mass at the pelvis. A total of ten healthy subjects performed two separate experiments while walking on an instrumented treadmill. The whole-body kinematics were recorded using a motion-capture system, and the ground reaction forces were measured by the force plates embedded in the treadmill. We found no significant differences in the kinematic gait parameters of healthy subjects when the downward force, equivalent to 15% body weight, applied by the TPAD was replaced by a weighted pelvic belt having 15% body weight. However, the activation of the gastrocnemius muscle and the estimated maximum ankle torque, predicted by an inverted pendulum mathematical model, during the single support phase of walking, showed a higher increase with the weight belt when compared to a pure downward force. Thus, the weight belt, because of its simplicity, must be further considered as a more convenient candidate to translate the results of TPAD in children with cerebral palsy who suffer from crouch gait.

How best to attach exoskeletons to human limbs is an open and understudied problem. In the case of upperbody exoskeletons, cylindrical handles are commonly used attachments due to ease of use and cost effectiveness. However, handles require active grip strength from the user and may result in undesirable flexion synergy stimulation, thus limiting the robot’s effectiveness. This paper presents a new design, the Eminence Grip, for attaching an exoskeleton to the hand while avoiding the undesirable consequences of using a handle. The ergonomic design uses inverse impedance matching and does not require active effort from the user to remain interfaced with the exoskeleton. We compare the performance of the Eminence Grip to the handle design in a healthy subject target reaching experiment. The results show that the Eminence Grip achieves similar performance to a handle in terms of relative motion between the user and the exoskeleton while eliminating the requirement of grip force to transfer loads to/from the exoskeleton and avoiding stimulation of the flexion synergy. Taken together, the kinematic equivalence and improvement in ergonomics suggest that the Eminence Grip is a promising exoskeleton-hand attachment interface supporting further experiments with impaired populations.

Measurement of interaction forces distributed across the attachment interface in wearable devices is critical for understanding ergonomic physical human–robot interaction (pHRI). The main challenges in sensorization of pHRI interfaces are (i) capturing the fine nature of force transmission from compliant human tissue onto rigid surfaces in the wearable device and (ii) utilizing a low-cost and easily implementable design that can be adapted for a variety of human interfaces. This paper addresses both challenges and presents a modular sensing panel that uses force-sensing resistors (FSRs) combined with robust electrical and mechanical integration principles that result in a reliable solution for distributed load measurement. The design is demonstrated through an upper-arm cuff, which uses 24 sensing panels, in conjunction with the Harmony exoskeleton. Validation of the design with controlled loading of the sensorized cuff proves the viability of FSRs in an interface sensing solution. Preliminary experiments with a human subject highlight the value of distributed interface force measurement in recognizing the factors that influence ergonomic pHRI and elucidating their effects. The modular design and low cost of the sensing panel lend themselves to extension of this approach for studying ergonomics in a variety of wearable applications with the goal of achieving safe, comfortable, and effective human–robot interaction.

In this work, we present and validate a novel inverse kinematics method for rehabilitation upper-limb exoskeletons that require joint coordination constraints. Starting from the conventional differential kinematics algorithm based on the inversion of the Jacobian matrix, we describe and test the improved algorithm based on the Projected-Gradient method, which takes into account inter-joint coordination constraints. The Harmony exoskeleton is used as a platform to demonstrate the method. In detail, we address the joint constraints needed to match anatomical shoulder movement and results show good performances of the proposed algorithm., https://youtu.be/x-EkavyAp_E

Hemiparetic gait is abnormal asymmetric walking, often observed among patients with cerebral palsy or stroke. One of the major features of asymmetric gait is excessive reliance on the healthy leg, which results in improper load shift, slow walking speed, higher metabolic cost, and weakness of the unused leg. Hence, clinically it is desirable to promote gait symmetry to improve walking. While there are no clear methods to achieve this goal, we are exploring new methods where we guide the pelvis to change the gait symmetry. This controller is designed to mimic the hands of a physical therapist holding the pelvis and guiding it to promote the usage of both legs during walking. In this paper, we show that the essence of this method can be demonstrated by promoting asymmetry in the gait of healthy subjects when walking with the device. The results showed that their kinematics and kinetics changed asymmetrically during the intervention. Subjects demonstrated asymmetric lateral ground reaction force to compensate for the lateral forces applied on the pelvis. Muscle activities increased on the targeted leg show the forced use of the leg which can be used for rehabilitation of patients with an asymmetric gait.

This work involves study of the first three natural frequencies of the perforated plates. The effect of the parameters which influence them have been studied. The parameters considered are the shape of perforations, pattern of the perforations, aspect ratio of the plate, dimensions of the plate, ligament efficiency and the mass remnant ratio (MRR). The study is focused on the effect of the most influencing parameter on the free vibrations.