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Traditional clinical approaches diagnose disorders of the nervous system using standardized observational criteria. Although aiming for homogeneity of symptoms, this method often results in highly heterogeneous disorders. A standing question thus is how to automatically stratify a given random cohort of the population, such that treatment can be better tailored to each cluster9s symptoms, and severity of any given group forecasted to provide neuroprotective therapies. In this work we introduce new methods to automatically stratify a random cohort of the population composed of healthy controls of different ages and patients with different disorders of the nervous systems. Using a simple walking task and measuring micro-fluctuations in their biorhythmic motions, we show that gait is compromised in healthy aging and that in young FMR1 premutation carriers, gait forecasts, even by 15 years ahead, symptoms resembling those of elderly with Parkinson9s disease. Our methods combine non-linear causal network connectivity analyses in the temporal and frequency domains with stochastic mapping, defining a new type of internal motor timings amenable to create personalized clinical interventions. We frame our results using the principle of reafference and operationalize them using causal prediction, thus renovating the theory of internal models for the study of neuromotor control.

Robotic gait training may improve overground ambulation for individuals with poor control over pelvic motion. However, there is a need for an overground gait training robotic device that allows full control of pelvic movement and synchronizes applied forces to the user's gait. This work evaluates an overground robotic gait trainer that applies synchronized forces on the user's pelvis, the mobile Tethered Pelvic Assist Device. To illustrate one possible control scheme, we apply an assistive frontal plane pelvic moments synchronized with the user's continuous gait in real-time. Ten healthy adults walked with the robotic device, with and without frontal plane moments. The frontal plane moments corresponded to 10% of the user's body weight with a moment arm of half their pelvic width. The frontal plane moments significantly increased the range of frontal plane pelvic angles from 2.6° to 9.9° and the sagittal and transverse planes from 4.6° to 10.1° and 3.0° to 8.3°, respectively. The frontal plane moments also significantly increased the activation of the left gluteus medius muscle, which assists in regulating pelvic obliquity. The right gluteus medius muscle activation did not significantly differ when frontal plane moments were applied. This work highlights the ability of the mobile Tethered Pelvic Assist Device to apply a continuous pelvic moment that is synchronized with the user's gait cycle. This capability could change how overground robotic gait training strategies are designed and applied. The potential for gait training interventions that target gait deficits or muscle weakness can now be explored with the mobile Tethered Pelvic Assist Device.

Freezing of gait is an episodic phenomena faced by many patients with Parkinson’s disease. It is characterized by episodes during which patients are unable to generate effective forward stepping movements, despite absence of motor deficits. During the onset of the event, the patients are less stable with statistically different stride width, toe in/out angle and center of pressure distance. It has been postulated that the degree of freezing can be reduced by providing external sensory feedback to the patients during the event. However, this intervention could be facilitated by accurate identification of freezing events in real-time. This manuscript presents an Artificial Neural Network model which uses signals recorded by an instrumented footwear to predict if a walking subject is having a freezing episode. Our model presented in this paper is capable of continuously predicting freezing of gait events at a high temporal resolution of 50 Hz, using a 0.5 second window of data recorded by the instrumented shoes, with a sensitivity of 96.0±2.5%, a specificity of 99.6±0.3%, a precision of 89.5±5.9%, and an accuracy of 99.5±0.4%. This algorithm was tested with data collected from 10 patients with Parkinson’s disease with frequent freezing of gait episodes.

A spatial displacement of a rigid body can be described as a combination of translation and rotation about an axis, known as Instantaneous Screw Axis (ISA). As the rigid body moves over time, ISA will form a ruled surface called axodes. The position and orientation of ISA and its trajectory over time plays an important role to determine kinematic models of the human body. It helps to design wearable orthoses and even to diagnose any pathological patterns. On the other hand, the motion of a rigid body can also be described by a transformation matrix and its time-derivative. This paper presents a synthesis of wearable orthoses based on ISA. The approach is developed based on the relation between two velocity matrices, one computed from the trajectory of the ISA, another one computed from the time-derivative of the transformation matrix. This relation yields a numerical synthesis of parameters of translations and rotations, and design parameters of a rigid body. The developed methodology is applied to a 3-RPS parallel manipulator to obtain parameters of translations and rotations, and platform dimensions for a given set of ISA. The surface of ISA axodes is visualized and three lines of ISA are selected. The poses of a 3-RPS parallel manipulator to achieve the motion defined by a given set of ISA are illustrated. The advantage of this approach is less parameters to be handled, since it aims to synthesize parameters of translations and rotations, instead of coordinates of points. A coupled motion (parasitic motion) undergone by a parallel manipulator can be easily solved by this approach.

This study investigates how external vertical forces on the pelvis change the stability of stairmill climbing and other gait parameters such as kinematics and muscle activity. We use a Tethered Pelvic Assist Device (TPAD) to apply forces on the pelvis during continuous ascent on a stairmill. Ten young healthy subjects participated in three one-minute stair ascent with no force, a 10% body weight (BW) downward force, and a 10% BW upward force applied on the pelvis. The stability is determined by evaluating the base of support (BoS) and margin of stability (MoS). Kinematics and muscle activities were used to characterize the biomechanical changes. The results show that the upward forces applied on the pelvis decreased the (i) MoS by 1.84cm in the lateral direction, 2.07cm in the anterior direction, (ii) double stance phase by 1.85%, and (iii) the knee flexion by 5°. Furthermore, the peak activation levels of the muscles rectus femoris (RF), vastus lateralis (VL), and left gastrocnemius decreased. In contrast, the downward forces applied on the pelvis increased (i) the MOS by 1.5cm in the anterior direction and (ii) mean activation levels of RF and VL muscles. This study provides insights into the effects of applied vertical forces on the pelvis during stair ascent. These findings contribute to the understanding of the gait parameter changes and their relation with stability. Results could be used as a basis for designing training protocols to improve balance during stair ascent.

In people with severe neuromotor deficits of trunk and lower extremities, regaining balance in standing is often performed in rehabilitation with manual assistance, rigid body supports or by the use of handrails. To investigate and further expand postural control training in standing, we developed a Robotic Upright Stand Trainer (RobUST). In this study, we used RobUST to deliver trunk perturbations while simultaneously providing postural assistive forces on the pelvis in 10 able-bodied adults. Posture control responses with 'pelvic support' was then compared to 'no support' and 'hand supported' standing, with and without assistance from RobUST. We characterize postural imbalance with kinematic displacements and center of pressure (COP) outcomes, such as amplitude and root mean square of the excursions of COP. Surface electromyography (sEMG) was also applied to investigate muscle control. We additionally investigated ground reaction and handrail forces during standing to analyze how postural strategies and muscle mechanisms with 'pelvic support' via RobUST would differ from standing with 'no support' and with the 'handrail support'. Our results show that during perturbations, pelvic assistive support decreased kinematic and COP excursions compared to standing with no support. The pelvic assistance from RobUST showed similar level of COP changes as the use of handrail support but without reducing muscle activity or ground reaction forces. As expected, the maximum level of postural stability was observed when participants used the handrail and received pelvic assistive forces. In conclusion, RobUST demonstrates potential as a training device since it enhances postural balance without significantly removing muscular control mechanisms that are of interest in re-training postural control strategies in standing.

Seated postural abilities are critical to functional independence and participation in children with cerebral palsy, Gross Motor Functional Classification System (GMFCS) levels III-IV. In this proof-of-concept study, we investigated the feasibility of a motor learning–based seated postural training with a robotic Trunk-Support-Trainer (TruST) in a longitudinal single-subject-design (13y, GMFCS IV), and its potential effectiveness in a group of 3 children (6-14y, GMFCS III-IV). TruST is a motorized-cable driven belt placed on the child’s trunk to exert active-assistive forces when the trunk moves beyond stability limits. TruST-intervention addresses postural-task progression by tailoring the assistive-force fields to the child’s sitting balance to train trunk control during independent short-sitting posture. TruST-intervention consisted of 2 training blocks of 6 2hour-sessions per block (3 sessions per week). Pelvic strapping was required in the 1(st) block to prevent falls. As primary outcomes, we used the modified functional reach test, gross motor function measure-item set (GMFM-IS), Box & Blocks, and postural kinematics. After TruST-intervention children did not require pelvic strapping to prevent a fall, improved trunk stability during reaching (baseline = 5.49cm, 1week post-training = 16.38cm, 3mos follow-up = 14.63cm, p < 0.001) and increased their sitting workspace (baseline = 127.55cm(2), 1week post-training, = 409.92cm(2), 3mos follow-up = 270.03cm(2), p < 0.001). Three children also improved in the GMFM-IS. In summary, our novel robotic TruST-intervention is feasible and can effectively maximize functional independent sitting in children with CP GMFCS III-IV.

Wearable robotic devices often need electrical energy. An interesting idea is to collect mechanical energy during walking and convert it into electrical energy to recharge these devices directly. In this article, we built a light-weight robotic prosthesis (1.3 kg) with the feature of self-charging. During stance phase, the prosthetic ankle joint with damping, is driven by human dynamics. The rotated ankle joint backdrives the motor, and the motor works as a generator according to the electromagnetic induction theory. Five subjects participated in experiments to verify the feasibility and five speeds walking were studied (0.7, 0.9, 1.1, and 1.3 m/s treadmill speeds and one self-selected outdoor walking speed). Experimental results demonstrate that the electrical regenerative energy per step is 1.53 $\pm \;\text{0.29}\,\text{J}$ on average. Meanwhile, an average consumed energy per step of the robotic prosthesis is 4.64 $\pm \;\text{0.15}\;\text{J}$ , which means 33 $\pm \;5\%$ energy can be returned to the active prosthesis (battery, 24 $\,\text{V}$ , 2.6 $\,\text{Ah}$ ).

Individuals with chronic hemiparesis post-stroke exhibit gait impairments that require functional rehabilitation through training. Exoskeletal robotic assistive devices can provide a user with continuous assistance but impose movement restrictions. There are currently devices that allow unrestricted movement but provide assistance only intermittently at specific points of the gait cycle. Our design, a cable-driven active leg exoskeleton (C-ALEX), allows the user both unrestricted movement and continuous force assistance throughout the gait cycle to assist the user in new walking patterns. In this study, we assessed the ability of C-ALEX to induce a change in the walking patterns of ten post-stroke participants using a single-session training protocol. The ability of C-ALEX to accurately provide forces and torques in the desired directions was also evaluated to compare its design performance to traditional rigid-link designs. Participants were able to reach 91% ± 12% of their target step length and 89% ± 13% of their target step height. The achieved step parameters differed significantly from participant baselines ( ${p} ). To quantify the performance, the forces in each cable’s out of the plane movements were evaluated relative to the in-plane desired cable tension magnitudes. This corresponded to an error of under 2Nm in the desired controlled joint torques. This error magnitude is low compared to the system command torques and typical adult biological torques during walking (2–4%). These results point to the utility of using non-restrictive cable-driven architectures in gait retraining, in which future focus can be on rehabilitating gait pathologies seen in stroke survivors.

Virtual Reality is a versatile platform to study human behavior in simulated environments and to develop interventions for functional rehabilitation. In this work, we designed a dual-task paradigm in a virtual environment where both tasks demand motor skills. Twenty-one healthy adults (mean age: 24.1 years) participated in this study. The experiment involved three conditions - normal overground walking, catch and throw a ball while standing, and catch and throw a ball while walking overground -all in the virtual environment. We investigated the dual-task gait characteristics and their correlations with outcomes from cognitive assessments. Results show that subjects walk conservatively with smaller stride lengths, larger stride widths and stride time while catching and throwing. However, they are able to throw the balls more accurately at the target and achieve higher scores. During the dual-task throw, we observed that the participants threw more balls during the stance phase of the gait when the foot was in the terminal stance and pre-swing region. During this region, the body has forward momentum. In addition, the changes in gait characteristics during dual-task throw correlate well with outcome measures in standardized cognitive tests. This study provides a new and engaging paradigm to analyze dual-motor-task cost in a virtual reality environment and it can be used as a basis to compare strategies adopted by different population groups with healthy young adults to execute coordinated motor tasks.

PurposeMulti-manned assembly lines are designed to produce large-sized products, such as automobiles. In this paper, a multi-manned assembly line balancing problem (MALBP) is addressed in which a group of workers simultaneously performs different tasks on a workstation. The key idea in this work is to improve the workstation efficiency and worker efficiency of an automobile plant by minimizing the number of workstations, the number of workers, and the cycle time of the MALBP.Design/methodology/approachA mixed-integer programming formulation for the problem is proposed. The proposed model is solved with benchmark test problems mentioned in research papers. The automobile case study problem is solved in three steps. In the first step, the authors find the task time of all major tasks. The problem is solved in the second step with the objective of minimizing the cycle time for the sub-tasks and major tasks, respectively. In the third step, the output results obtained from the second step are used to minimize the number of workstations using Lingo 16 solver.FindingsThe experimental results of the automobile case study show that there is a large improvement in workstation efficiency and worker efficiency of the plant in terms of reduction in the number of workstations and workers; the number of workstations reduced by 24% with a cycle time of 240 s. The reduced number of workstations led to a reduction in the number of workers (32% reduction) working on that assembly line.Practical implicationsFor assembly line practitioners, the results of the study can be beneficial where the manufacturer is required to increased workstation efficiency and worker efficiency and reduce resource requirement and save space for assembling the products.Originality/valueThis paper is the first to apply a multi-manned assembly line balancing approach in real life problem by considering the case study of an automobile plant.

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.

An ambulatory elder with SCI, AIS C, balance deficits, and right ankle-foot-orthosis participated. RobUST-intervention comprised six 90 min-sessions of postural tasks with pelvic assistance and trunk perturbations. We collected three baselines and two 1 week post-training assessments—after the first four sessions (PT1) and after the last two sessions (PT2). We measured Berg Balance Scale (BBS), four-stage balance test (4SBT)—including a 30 s-window with and without vision—standing workspace area, and reactive balance (measured as body weight%). Kinematics, center-of-pressure (COP), and electromyography (EMG) were analyzed to compute root-mean-square-COP (RMS-COP), the margin of stability (MoS), ankle range of motion, and integrated EMG (iEMG) normalized to baseline. The Borg Rating of Perceived Exertion (BRPE), and change in the Mean Arterial Pressure (MAP) and heart rate (HR) compared with baseline were collected to address training tolerance. A 2SD-bandwidth method was selected for data interpretation. The maximum BBS was achieved (1-point improvement). In the 4SBT, the participant completed 30 s (baseline = 20 s) with reduced balance variability during semi-tandem position without vision (RMS-COP baseline = 50.32 ± 2 SD = 19.64 mm; PT1 = 21.29 mm; PT2 = 19.34 mm). A trend toward increase was found in workspace area (baseline = 996 ± 359 cm(2); PT1 = 1539 cm(2); PT2 = 1138 cm(2)). The participant tolerated higher perturbation intensities (baseline mean = 25%body weight, PT2 mean = 44% body weight), and on average improved his MoS (3 cm), ankle range of motion (4°), and gluteus medius activity (iEMG = 10). RobuST-intervention was moderate-sort of hard (BRPE = 3–4). A substantial reduction in MAP (9%) and HR (30%) were observed. In conclusion, RobUST-intervention might be effective in ambulatory SCI.

Background. High-intensity repetitive training is challenging to provide poststroke. Robotic approaches can facilitate such training by unweighting the limb and/or by improving trajectory control, but the extent to which these types of assistance are necessary is not known. Objective. The purpose of this study was to examine the extent to which robotic path assistance and/or weight support facilitate repetitive 3D movements in high functioning and low functioning subjects with poststroke arm motor impairment relative to healthy controls. Methods. Seven healthy controls and 18 subjects with chronic poststroke right-sided hemiparesis performed 300 repetitions of a 3D circle-drawing task using a 3D Cable-driven Arm Exoskeleton (CAREX) robot. Subjects performed 100 repetitions each with path assistance alone, weight support alone, and path assistance plus weight support in a random order over a single session. Kinematic data from the task were used to compute the normalized error and speed as well as the speed-error relationship. Results. Low functioning stroke subjects (Fugl-Meyer Scale score = 16.6 ± 6.5) showed the lowest error with path assistance plus weight support, whereas high functioning stroke subjects (Fugl-Meyer Scale score = 59.6 ± 6.8) moved faster with path assistance alone. When both speed and error were considered together, low functioning subjects significantly reduced their error and increased their speed but showed no difference across the robotic conditions. Conclusions. Robotic assistance can facilitate repetitive task performance in individuals with severe arm motor impairment, but path assistance provides little advantage over weight support alone. Future studies focusing on antigravity arm movement control are warranted poststroke.

Purpose Parallel two-sided assembly lines are usually designed to produce large-sized products such as trucks and buses. In parallel two-sided assembly lines, both left and right sides of the line are used for manufacturing one or more products on two or more assembly lines located parallel to each other. The purpose of this paper is to develop a new mathematical model for the parallel two-sided assembly line balancing problem that helps to evaluate and validate the balancing operations of the machines such as removal of tools and fixtures and reallocating the operators. Design/methodology/approach The proposed approach is explained with the help of an example problem. In all, 22 test problems are formed using the benchmark problems P9, P12, P16 and P24. The results obtained are compared among approaches of the task(s) shared, tool(s) shared and both tool(s) and task(s) shared for effect on efficiency as the performance measure. The solution presented here follows the exact solution procedure that is solved by Lingo 16 solver. Findings Based on the experiments, line efficiency decreases when only tools are shared and increases when only tasks are shared. Results indicate that by sharing tasks and tools together, better line efficiency is obtained with less cost of tools and fixtures. Practical implications According to the industrial aspect, the result of the study can be beneficial for assembly of the products, where tools and tasks are shared between parallel workstations of two or more parallel lines. Originality/value According to the author’s best knowledge, this paper is the first to address the tools and tasks sharing between any pair of parallel workstations.

Background: Those with increased dynamic knee valgus are vulnerable to increased risk of non-contact kneeinjuries. However, studies on the top down kinetic chain of lower limb mechanics during dynamic motionssuch as single leg squat (SLS) among trained males were scarce.Objective: The objective of the study was to evaluate the relationship between isokinetic hip and knee strengthand frontal plane projection angle (FPPA) of the knee joint during SLS.Methods: Thirty-two male junior athletes (twelve cyclists, ten runners and ten squash players) were screenedfor excessive dynamic knee valgus (DKV) prior to participation. Only those within the normal value of DKV wereincluded. Their hip and knee isokinetic strength in sagittal plane were evaluated at 60Âo/s of angular velocityfor both legs using dynamometer. Two dimensional knee FPPA was evaluated during SLS at 60Âo of knee flexion.Pearson correlation was evaluated between knee FPPA during SLS and isokinetic leg strength.Results: Correlations between knee FPPA and hip and knee isokinetic strength were not statistically significantexcept between knee flexion peak torque/body weight (r = -0.35, p = 0.05) and hamstring to quadriceps ratio(r = -0.39, p = 0.03) of non-dominant leg.Conclusions: Isokinetic hip and knee strength and knee FPPA during SLS was correlated only for non-dominantleg during SLS among male junior athletes. DKV during SLS may be reduced through strengthening the musclesaround hip and knee joints.

Virtual reality (VR) is a useful tool to assess and improve spatial navigation, a complex skill and relevant marker for progression of dementia. A fully-immersive VR system that allows the user to physically navigate in the space can provide an ecologically valid environment for early detection and remediation of cognitive and navigational deficits. The aim of this study was to develop a virtual version of the floor maze test (VR-FMT), a navigational test that requires navigating through an unfamiliar two-dimensional floor maze. With the VR-FMT, mazes of desired complexity and walls of preferred height can be built to challenge navigational ability and mask visual clues. Fifty-five healthy adults completed the FMT in three different conditions: real environment (RE), virtual environment with no walls (VE-NW), and virtual environment with walls (VE-W). In addition, they completed two neuropsychological tests, the Trail Making Test and Digit Symbol Substitution Test. Results showed that the time to complete the maze in the VE was significantly higher than in the RE. The introduction of walls increased the number of errors, the completion time, and the length of the path. Only time to exit in the VE-W correlated with results of the cognitive tests. Participants were further subdivided on the basis of their time to exit the maze in the RE, VE-NW, and VE-W (low navigational time - LNT, and high navigational time - HNT). Only when analyzing the time to exit the maze in the VE-W, the LNT group outperformed the HNT group in all cognitive tests.

Objective This paper presents the first study where a dynamic neck brace was used to characterize the head motion of ALS patients while concurrently recording the surface electromyography (EMG) of the neck muscles. Methods Eleven ALS patients and 10 age‐matched healthy controls consented and participated in an experiment. Each participant was asked to perform three single‐plane motions of the head‐neck that included flexion–extension in the sagittal plane, lateral bending in the coronal plane, and axial rotation in the transverse plane. Each motion was performed in a cycle and was repeated five times at self‐selected speeds. Results During single‐plane flexion–extension under gravity, compared to healthy peers, ALS patients showed a shorter duration to reach the maximum flexion and an earlier EMG onset in the neck extensors starting from the neutral. The brace measures in activation of the neck muscles in ALS patients were well correlated with clinically measured scores, such as the ALSFRS‐r and the FVC. The activation duration of sternocleidomastoid, used to rotate the head, correlated well with the ALSFRS‐r and FVC in ALS patients during axial rotation. Interpretation The ability to synchronously activate a pair of muscles to execute single‐plane motions in ALS patients seems to have been compromised due to the disease and potentially results in head drop. The neck brace measures can be adapted in the clinic to complement self‐reporting in ALS patients and used to assess the head drop and progress of the disease.

SummaryPeople with severe neuromuscular trunk impairment cannot maintain or control upright posture of the upper body in sitting while reaching. Passive orthoses are clinically available to provide support and promote the use of upper extremities in this population. However, these orthoses only position the torso passively without any degree of trunk movement.We introduce for the first time a novel active-assistive torso brace called Wheelchair Robot for Active Postural Support (WRAPS). It consists of two rings over the hips and chest connected by a 2RPS-2UPS parallel robotic device. WRAPS can modulate the displacement of the upper ring and/or the forces applied on the torso through the ring in four degrees-of-freedom (DOF), including rotations and translation in the sagittal and frontal planes.In the present study, we evaluate the design of WRAPS and its functions. Moreover, we discuss the potential effectiveness of WRAPS as a therapeutic robotic tool in people with severe trunk control deficits. The performance of WRAPS was evaluated in seated healthy subjects. Kinematics and surface electromyography (sEMG) were collected when the participants performed selective trunk movements. First, the torso range of motion (tROM) was calculated with WRAPS in transparent mode—zero-force control mode—which was compared with free-guided tROM (no WRAPS) with motion capture system. Second, a position control mode was configured to mobilize the torso along the trajectories obtained with the transparent mode.Our results show that the design of WRAPS suited well the subject’s anthropometrics while supporting the weight of the torso. Importantly, WRAPS can be programmed to replicate the subject’s tROM, without the full activation of torso muscles. This can be critical in individuals with no trunk control. Altogether, these preliminary results indicate the potential applicability of WRAPS to promote active-assistive trunk mobility in people who cannot sit independently because of trunk dysfunction.

The authors present a Recurrent Neural Network classifier model that segments the walking data recorded with instrumented footwear. The signals from 3 piezoresistive sensors, a 3-axis accelerometer, and Euler angles are used to generate temporal gait characteristics of a user. The model was tested using a data set collected from 28 adults containing 4198 steps. The mean errors for heel strikes and toe-offs were -5.9 ± 37.1 and 11.4 ± 47.4 milliseconds. These small errors show that the algorithm can be reliably used to segment the gait recordings and to use this segmentation to estimate temporal parameters of the subjects.

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.

Cable-driven exoskeletons add minimal inertia and restrictions to the user’s leg while still providing feedback and quantitative measures of the user’s performance. However, cable robots require at least n + 1 cables to control n degrees-of-freedom, i.e., they require more actuators than the leg’s degrees-of-freedom, challenging their widespread adoption as wearable technology. The state-of-the-art in this field aims to reduce the number of actuated motors. In this paper, we design and evaluate a “single motor-driven” leg exoskeleton prototype based on the Cable-driven Active Leg EXoskleton (C-ALEX). The prototype consists of four crank-spring mechanisms and a crankshaft designed using epicycle analysis. The epicycle analysis is performed using discrete Fourier transform (DFT) and sine curve fitting (SCF). While DFT suggests the maximum number of epicycles to imitate the target waveform, a large number of nested epicycles is challenging to design and manufacture for implementation. To validate the epicycle-guided design, we constructed a simple crankshaft model using one epicycle. Our proposed simplified model predicted and produced the joint angles calculated from the inverse and forward kinematics of a cable-driven leg exoskeleton with multiple motors. To our knowledge, this is the first multi-cable driven exoskeleton powered by a single actuator that is designed to provide continuous assistance to the user.

In this paper, a customized optical force sensor is developed for an application with a cable-driven leg exoskeleton. Sensors are vital components of cable-driven, exoskeletal robotic systems, which require real-time and accurate measurement of cable tensions. While these systems’ accuracy is a consideration, the added weight, volume, and complexity of the system must is an essential part of widespread adoption for wearable applications. These sensors can also be costly, which is undesirable. An optical force sensor has the advantages of being lightweight, lower in manufacturing cost, and easy to incorporate within the exoskeleton architecture. We designed a sensor to accommodate the expected force profiles and magnitudes during gait while wearing the Cable-Driven Active Leg Exoskeleton (C-ALEX) during a walking task. We carried out four different calibration tests with dynamic loading of the sensors from 10N to 40N. Once a sensor calibration was established, the optical sensor’s performance was compared to a traditional load cell in validation tests. Both components were used in an assist-as-needed force controller in a walking task with a user, with the optical force sensor incorporated into the C-ALEX exoskeleton arms. Comparing the sensor responses to the command tension forces, the results show a root-mean-square error (RMSE) of 0.9595N ± 0.5360N.