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Pelvis mobility is essential to the daily seated activities of wheelchair users, however it is not yet fully addressed in the field of active wearable devices. This letter presents a novel design and optimization methodology of an in-parallel actuated robotic brace for assisting the human pelvis during seated maneuvers on wheelchair. This design uses human data captured by cameras in conjunction with the knowledge of kinematic geometry and screw theory. The mechanism has full rotational three degrees-of-freedom (DOFs) and also accommodates coupled translation of the human pelvic segment. This type of motion was realized by employing three kinematic limbs that impose non-intersecting zero-pitch constraint wrenches on the platform. Our multi-objective optimization (MOO) routine consists of two stages: (I) platform constraint synthesis, where the geometric parameters of the limb constraints were determined to minimize the pelvis-platform errors of trajectories and instantaneous screw axes (ISAs); and (II) limb structural synthesis, where limb types and dimensions, workspace, transmission performances, singularities, and actuated joint displacements were considered. The optimized mechanism has an asymmetrical [ R RR]U-2[ R R]S architecture. This mechanism can also be integrated into our previously developed Wheelchair Robot for Active Postural Support (WRAPS).

Adolescent Idiopathic Scoliosis (AIS) is a spinal curvature that affects 3% of the population and disproportionately affects females. It is treated with bracing and many researchers are developing models of the torso to optimize the effectiveness of brace designs. Unfortunately, the data available to create these models is limited by the experimental methods employed. One method, in vitro spine cadaver stiffness measurements, is generally based on specimens from the elderly, which are not representative of the adolescent population. The other method, radiographic studies, can only provide a limited amount of information because of the radiation exposure that multiple images require. In this work, we present a Robotic Spine Exoskeleton (RoSE) tailored to the population in greatest need of AIS interventions–female adolescents. We use it to create a three-dimensional stiffness characterization of the torso in vivo for eight female adolescents with scoliosis and eight without this condition. The key findings include an interaction effect of DOF and torso segment on translational collinear stiffnesses, and an interaction effect of DOF and group on rotational collinear stiffnesses. We also found that the 3D coupling stiffness pattern is in line with that of the human spine, regardless of spinal deformity. Also, the magnitude of the torso stiffness for the tested population is less than that of the adult male population previously characterized. Our results provide quantitative data for torso stiffness and can be used to improve brace designs. Our methods could also be adapted as a way to customize subject-specific treatment methods, as there is a lot of variation among subjects.

Visual and force feedback are common elements in rehabilitation robotics, but visual feedback is difficult to provide in over-ground mobile exoskeleton systems. This letter aims to provide a method to integrate visual feedback using an augmented reality HoloLens headset with our mobile C-ALEX system. A preliminary study was carried out to assess the effects of providing force-only (Haptic), force and visual (HoloHapt) or visual (Visual) feedback to three independent groups, each containing eight participants. The groups showed an increase in normalized step height, nSH (HoloHapt: 1.10 $\pm$ 0.13, Haptic: 1.03 $\pm$ 0.23 Visual: 1.61 $\pm$ 0.52) and decreased normalized trajectory tracking error, TE (HoloHapt: 42.8% $\pm$ 23.4%, Haptic: 47.6% $\pm$ 18.4%, Visual: 114 .2 % $\pm$ 60.0 % ). Visual nSH differed significantly from HoloHapt and Haptic nSH ( $p ). Lap-wise normalized tracking error differed significantly ( $p ) within participants. The results show the feasibility of and differences between each form of feedback for overground gait training. This information is useful for future studies targeted at patients with gait impairments.

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.

Coordinated head–neck movement is a challenge for patients with neurological disorders, such as cerebral palsy and amyotrophic lateral sclerosis. Neck collars are commonly used to stabilize the head–neck in these patients. These collars are mostly rigid and uncomfortable to wear for extended periods of time. We have developed a robotic neck brace to assist head–neck motion. In this letter, we focus on using the robotic neck brace for training of the head-neck motion using forces applied on the head. A force controller is implemented to deliver a moment to correct the head motion in an ‘assist-as-needed’ fashion. A human study was designed to assess the performance of the robotic neck brace with the force controller. Ten young healthy adults participated in the experiment. They were asked to perform a lateral bending motion in the coronal plane of the head-neck with and without the assistance of the brace. The motions were conducted under two conditions: i) with visual feedback, ii) with visual and force feedback. We found that the rotational movement errors were significantly reduced ( $p ) during training with the force field when compared to visual feedback alone. As expected, this change was not retained during post-training. We conclude that the force controller is able to provide the desirable force assistance to help coordinate the head motion.

Standing postural control requires a complex interaction between the sensory and motor systems. Among sensory inputs, proprioception plays a fundamental role in the fine control of postural movements. In some neuromotor disorders, defects in the proprioceptive system may be associated with unsteady, uncoordinated, and exacerbated upper body movements during activities of daily living that may secondarily result in imbalance, falls, and severe injuries. Passive or active proprioceptive interventions are implemented routinely as a critical part of rehabilitation programs that target postural balance disorders. In this study, we have created a novel multimodal robotic platform merging both passive and active modalities to enhance upper body control. We hypothesize that the combination of passive resistance at pelvis in combination with active control of the lower thorax via assist-as-needed haptic feedback can enhance standing postural control. To test this hypothesis, we recruited ten healthy adults and had them perform dexterous reaching tasks either with or without a robotic system, while they stood unstably on a balance ball. The results of our pilot study show that individuals can improve postural stability of the upper body by selectively reducing upper trunk motion relative to caudal segments in the direction of the reaching arm, after training with the robotic platform.

Dropped head syndrome is often seen in patients with neurological disorders, such as amyotrophic lateral sclerosis. Static collars are often prescribed to these patients to support their head. These collars support the head in one position but do not allow motion to the head. In this letter, we present a novel active neck brace to address this issue and provide assistance to the patients to improve their neck range of motion. This brace has three degrees-of-freedom and allows improved range of motion to the head and neck. We have developed a joystick interface for this brace to allow the user to carry out their intended head rotation with assistance of the brace. In order to assess the feasibility of the use of this brace, we present a study that recruited eight healthy subjects. We simultaneously recorded the motion of the head, electromyography of the neck muscles, and force/torque applied through the brace to the head. The results show that the brace provides support to the head and subjects activate their muscles less when assisted by the brace using the joystick.

Improving functional motor deficits in patients with neurological and musculoskeletal disorders has been a primary objective of rehabilitation. Task-oriented training in physical environments is a leading approach for rehab training utilizing tasks that are challenging, adaptable, and meaningful. Although different training paradigms can be utilized in a laboratory setting, they often require expensive training equipment and personnel, limiting the number of training sessions. Creating an effective virtual reality (VR) training environment can greatly increase the repetition, cognitive engagement, and training variability. Specifically, dynamic trunk control is required for the successful completion of everyday tasks. These tasks require coordination between the head, upper and lower trunk, and the pelvis. We have developed a novel robotic device, trunk support trainer (TruST) and a VR gaming environment, which allows training in a seated posture at and beyond an individual's point of stability failure using an assist-as-needed force tunnel strategy. The VR environment consists of challenging reaching tasks where the subject's dominant hand is used to manipulate a VR drone. We conducted a study that involved three groups: ten adult subjects trained using VR, ten adult subjects trained in a physical environment (PR), and ten without TruST assistance (control group) to investigate the changes in trunk kinematics. Our study supports the hypothesis that a single training session with TruST in both VR and PR can increase lower trunk range of motion. This approach may be useful for creating training variability and translating therapy in home settings.

Quantitative analysis of the plantar pressure distribution during dynamic tasks can facilitate diagnosis of foot and ankle dysfunctions and prevent potential injuries by providing detailed information about weight bearing and weight shifting patterns. Traditional laboratory measurements are currently limited by high operating costs and lack of portability. The use of instrumented insoles capable of capturing kinematic and kinetic gait parameters as subjects perform out-of-the-lab dynamic activities is a promising approach to overcome these limitations. This letter introduces SportSole , a fully portable system that can measure spatiotemporal gait parameters and center of pressure (CoP) trajectories. Wearing the SportSole , nine able-bodied subjects completed a walking session followed by a running session, each consisting of 10 full laps along a 16-meter straight-line path. Accuracy and precision of CoP trajectories and kinematic parameters were assessed using an electronic walkway as the reference system. After calibration, mean deviations in the CoP were 0.61 $\pm$ 0.05 cm (RMSE $\pm$ SD) for walking and 0.72 $\pm$ 0.08 cm for running. Deviations in stride length, stride time, and velocity were 1.66 $\pm$ 0.18 cm, 0.006 $\pm$ 0.003 s, and 1.65 $\pm$ 0.10 cm/s for walking, 1.91 $\pm$ 0.19 cm, 0.01 $\pm$ 0.03 s, and 2.67 $\pm$ 0.38 cm/s for running. These promising results indicate that the proposed system has the potential to be used for out-of-the-lab gait analysis of walking and running.

Haptic feedback affects not only the quality of training but can also influence the physical design of robotic gait trainers by determining how much force needs to be applied to the user and the nature of the force. This paper presents the design of a variable damping force tunnel and explores the effect of the shape and strength of the damping field using ALEX III, a treadmill-based exoskeleton developed at Columbia University. The study consists of 32 healthy subjects who were trained for 40 minutes in the device. The subjects were trained to follow a footpath with a 50% increase in step height, so the foot would have 1.5 times the ground clearance. Subjects were assigned to one of four groups: linear high, linear low, parabolic high, and parabolic low. Linear or parabolic denotes the shape of the damping field, and high or low denotes the rate of change (strength) of the field based on error. It is shown that the new controller is capable of inducing gait adaptations in healthy individuals while walking in the device. All groups showed adaptations in step height, while only the high strength groups showed changes in normalized error area, a measure of how closely the desired path was followed.

Head drop is a symptom commonly seen in patients with amyotrophic lateral sclerosis. These patients usually experience neck pain and have difficulty in swallowing and breathing. Static neck braces are used in current treatment. These braces, however, immobilize the head in a single configuration, which causes muscle atrophy. This letter presents the design of a dynamic neck brace for the first time in the literature, which can both measure and potentially assist in the head motion of the human user. This letter introduces the brace design method and validates its capability to perform measurements. The brace is designed based on kinematics data collected from a healthy individual via a motion capture system. A pilot study was conducted to evaluate the wearability of the brace and the accuracy of measurements with the brace. This study recruited ten participants who performed a series of head motions. The results of this human study indicate that the brace is wearable by individuals who vary in size, the brace allows nearly $70\%$ of the overall range of head rotations, and the sensors on the brace give accurate motion of the head with an error of under $5^{\circ }$ when compared to a motion capture system. We believe that this neck brace can be a valid and accurate measurement tool for human head motion. This brace will be a big improvement in the available technologies to measure head motion as these are currently done in the clinic using hand-held protractors in two orthogonal planes.

Dynamic seated trunk control is required during the execution of many everyday tasks. These tasks require an intricate coordination between the head, upper and lower trunk, and the pelvis. Furthermore, reaching beyond the arm's length requires precise joint control and intersegmental coordination. With practice specificity, humans can learn particular motor skills that may be performed across contexts of similar characteristics. As new tasks are explored, human movements are learned and organized by the release and constraint of degrees-of-freedom, and the modulation of joint amplitudes that are specific to the task demands. Thus, by providing seated reach training without foot support that challenges postural control close to and beyond the stability limits or point of stability failure, an individual with an optimal level of trunk assistance could improve postural control by increasing the range of motion of the trunk and expand the boundaries that define the point of stability failure. We have developed a novel cable robotic device, trunk support trainer (TruST), which allows training of seated posture at and beyond an individual's point of stability failure during volitional trunk displacement. This is accomplished by creating a force tunnel to support posture beyond the sitting stability region. The system provides an assist-as-needed force strategy to support the trunk. We conducted a proof-of-concept study with 20 healthy adult subjects (10 experimental and 10 control) to investigate the changes in lower trunk center of mass (COM) displacement and trunk kinematics. Our study supports the hypothesis that a single training session with TruST at and beyond the point of stability failure increases lower trunk COM displacement and increases the lower trunk and pelvic rotation. The findings suggest that this approach may be useful for training patients with neurological and musculoskeletal disorders where children or adults have compromised postural stability.