Bilateral Assessment of Functional Tasks for Robot-assisted Therapy Applications

This article presents a novel evaluation system along with methods to evaluate bilateral coordination of arm function on activities of daily living tasks before and after robot-assisted therapy. An affordable bilateral assessment system (BiAS) consisting of two mini-passive measuring units modeled as three degree of freedom robots is described. The process for evaluating functional tasks using the BiAS is presented and we demonstrate its ability to measure wrist kinematic trajectories. Three metrics, phase difference, movement overlap, and task completion time, are used to evaluate the BiAS system on a bilateral symmetric (bi-drink) and a bilateral asymmetric (bi-pour) functional task. Wrist position and velocity trajectories are evaluated using these metrics to provide insight into temporal and spatial bilateral deficits after stroke. The BiAS system quantified movements of the wrists during functional tasks and detected differences in impaired and unimpaired arm movements. Case studies showed that stroke patients compared to healthy subjects move slower and are less likely to use their arm simultaneously even when the functional task requires simultaneous movement. After robot-assisted therapy, interlimb coordination spatial deficits moved toward normal coordination on functional tasks

Timing and correction of stepping movements with a virtual reality avatar

Research into the ability to coordinate one’s movements with external cues has focussed on the use of simple rhythmic, auditory and visual stimuli, or interpersonal coordination with another person. Coordinating movements with a virtual avatar has not been explored, in the context of responses to temporal cues. To determine whether cueing of movements using a virtual avatar is effective, people’s ability to accurately coordinate with the stimuli needs to be investigated. Here we focus on temporal cues, as we know from timing studies that visual cues can be difficult to follow in the timing context. Real stepping movements were mapped onto an avatar using motion capture data. Healthy participants were then motion captured whilst stepping in time with the avatar’s movements, as viewed through a virtual reality headset. The timing of one of the avatar step cycles was accelerated or decelerated by 15% to create a temporal perturbation, for which participants would need to correct to, in order to remain in time. Step onset times of participants relative to the corresponding step-onsets of the avatar were used to measure the timing errors (asynchronies) between them. Participants completed either a visual-only condition, or auditory-visual with footstep sounds included, at two stepping tempo conditions (Fast: 400ms interval, Slow: 800ms interval). Participants’ asynchronies exhibited slow drift in the Visual-Only condition, but became stable in the Auditory-Visual condition. Moreover, we observed a clear corrective response to the phase perturbation in both the fast and slow tempo auditory-visual conditions. We conclude that an avatar’s movements can be used to influence a person’s own motion, but should include relevant auditory cues congruent with the movement to ensure a suitable level of entrainment is achieved. This approach has applications in physiotherapy, where virtual avatars present an opportunity to provide the guidance to assist patients in adhering to prescribed exercises

Influence of Muscle Fatigue on Electromyogram-Kinematic Correlation During Robot-Assisted Upper Limb Training

© The Author(s) 2020. Creative Commons Non Commercial CC BY-NC: This article is distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 License (https://creativecommons.org/licenses/by-nc/4.0/) which permits non-commercial use, reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access pages (https://us. sagepub.com/en-us/nam/open-access-at-sage).Introduction: Studies on adaptive robot-assisted upper limb training interactions do not often consider the implications of muscle fatigue sufficiently. Methods: In order to explore this, we initially assessed muscle fatigue in 10 healthy subjects using electromyogram features (average power and median power frequency) during an assist-as-needed interaction with HapticMASTER robot. Spearman’s correlation study was conducted between EMG average power and kinematic force components. Since the robotic assistance resulted in a variable fatigue profile across participants, a completely tiring experiment, without a robot in the loop, was also designed to confirm the results. Results: A significant increase in average power and a decrease in median frequency were observed in the most active muscles. Average power in the frequency band of 0.8-2.5Hz and median frequency in the band of 20-450Hz are potential fatigue indicators. Also, comparing the correlation coefficients across trials indicated that correlation was reduced as the muscles were fatigued. Conclusions: Robotic assistance based on user’s performance has resulted in lesser muscle fatigue, which caused an increase in the EMG-force correlation. We now intend to utilize the electromyogram and kinematic features for the auto-adaptation of therapeutic human-robot interactions.Peer reviewedFinal Published versio

GENTLE/A - Adaptive Robotic Assistance for Upper-Limb Rehabilitation

Advanced devices that can assist the therapists to offer rehabilitation are in high demand with the growing rehabilitation needs. The primary requirement from such rehabilitative devices is to reduce the therapist monitoring time. If the training device can autonomously adapt to the performance of the user, it can make the rehabilitation partly self-manageable. Therefore the main goal of our research is to investigate how to make a rehabilitation system more adaptable. The strategy we followed to augment the adaptability of the GENTLE/A robotic system was to (i) identify the parameters that inform about the contribution of the user/robot during a human-robot interaction session and (ii) use these parameters as performance indicators to adapt the system. Three main studies were conducted with healthy participants during the course of this PhD. The first study identified that the difference between the position coordinates recorded by the robot and the reference trajectory position coordinates indicated the leading/lagging status of the user with respect to the robot. Using the leadlag model we proposed two strategies to enhance the adaptability of the system. The first adaptability strategy tuned the performance time to suit the user’s requirements (second study). The second adaptability strategy tuned the task difficulty level based on the user’s leading or lagging status (third study). In summary the research undertaken during this PhD successfully enhanced the adaptability of the GENTLE/A system. The adaptability strategies evaluated were designed to suit various stages of recovery. Apart from potential use for remote assessment of patients, the work presented in this thesis is applicable in many areas of human-robot interaction research where a robot and human are involved in physical interaction

Rotary Task Kinematic and Kinetic Analysis of the Lower Extremity After Total Knee Arthroplasty: Stability and Strategies

Knee instability has been identified as a contributor to the need for total knee replacement (TKR) revision surgery. As TKR revisions increase, the importance of understanding the mechanisms of knee instability becomes a priority to the surgeons, rehabilitation specialists and designers in industry. Objective measurements of knee instability have been recorded by instruments such as the knee arthrometer or with the leg encased in a boot driven by a dial test tool for rotation. Both of these tests are performed in the open-chain position and the knee arthrometer only measures laxity in the sagittal plane. Despite capturing total range of motion (ROM) excursion or laxity measurement, these tests do not reproduce what is described as the working definition for knee instability. Functional knee instability, defined as the subjective report of the knee `buckling' or `giving way', correlates to a dynamic event rather than an open-chain occurrence. Therefore, a weight-bearing, dynamic test would be required in order to identify knee instability. In order to test dynamic knee instability, rotation should be included to add a dimension of out-of-plane movement that correlates to pivoting, change of direction or rotating with bending and extending or reaching while loading and unloading the knee. Twenty-eight individuals (10 TKR, 12 Healthy, 6 Unstable) performed two tasks, Stair Task and Target Touch Task (TTT), and kinetic and kinematic data were captured by motion analysis and force platforms. The Stair Task included a pivot turn after stair descent and the TTT required a series of button pushes while squatting and extending, with rotation or crossing mid-line. Variables from both tasks were imputed to a Principle Components Analysis (PCA) in order to identify differences of performance across the groups. In the Stair Task, the TKR group had less Ground Reaction Force (GRF) on initial impact after stair descent compared to the unaffected leg (p=0.021) and during mid-stance compared to the healthy group (p=0.049). The affected stance leg had less knee flexion during mid-stance in both the straight trial (p=0.002) and turn (p=0.010). Similarly, the TKR individuals maintained a more extended knee position for both affected (14.7°) and unaffected (17.8&#730;) during the TTT when compared to the healthy (25.5&#730;) when approaching mid-line to transfer weight in order to push the low button when squatting (p<.05). Further, a difference was noted between the TKR legs during the motion to push the high button. At 90% of this cycle of movement, the unaffected knee was more flexed when compared to the affected knee (p<.05). A large variation of loading during mid-cycle was noted with the TKR group suggesting difficulty with stabilization during the transition of side to side motion with rotation. The PCA model was utilized to compile 29 variables selected from the two tasks in order to identify related performance variables for all groups. Interestingly, no dominant concepts were derived from the analysis; rather, the percentage of variables loaded up to 12 PCs to achieve 80% of the explained variation. Temporal variables dominated PC1 when comparing Unstable to Healthy as well as TKR to Healthy. Both the Unstable and TKR groups performed the tasks slower than the Healthy group. While delay or slowed response may be related to a protective response to avoid fall, the hesitation may be associated with information response from the Central Nervous System (CNS). In addition, compensatory movements from adjacent joints were noted in the TKR group such as utilizing torso movements to achieve the TTT rather than bending the knee. Altered mechanics that may be a result of pre-operative habits or a result of surgery, could lead to injuries to other joints. Rehabilitation interventions should address symmetrical movements with weight transfer and rotation in order to avoid future injuries

Joint Trajectory Generation and High-level Control for Patient-tailored Robotic Gait Rehabilitation

This dissertation presents a group of novel methods for robot-based gait rehabilitation which were developed aiming to offer more individualized therapies based on the specific condition of each patient, as well as to improve the overall rehabilitation experience for both patient and therapist. A novel methodology for gait pattern generation is proposed, which offers estimated hip and knee joint trajectories corresponding to healthy walking, and allows the therapist to graphically adapt the reference trajectories in order to fit better the patient's needs and disabilities. Additionally, the motion controllers for the hip and knee joints, mobile platform, and pelvic mechanism of an over-ground gait rehabilitation robotic system are also presented, as well as some proposed methods for assist as needed therapy. Two robot-patient synchronization approaches are also included in this work, together with a novel algorithm for online hip trajectory adaptation developed to reduce obstructive forces applied to the patient during therapy with compliant robotic systems. Finally, a prototype graphical user interface for the therapist is also presented

The Investigation of Motor Primitives During Human Reaching Movements and the Quantification of Post-Stroke Motor Impairment

Movement is a complex task, requiring precise and coordinated muscle contractions. The forces and torques produced during multi-segmental movement of the upper limbs in humans, must be controlled, in order for movement to be achieved successfully. Although a critical aspect of everyday life, there remain questions regarding the specific controller used by the central nervous system to govern movement. Furthermore, how this system is affected by neurological injuries such as stroke also remains in question. It was the goal of this thesis to examine the neurological control of movement in healthy individuals and apply these findings to the further investigation of chronically motor impaired stroke patients. Additionally, this work aimed at providing clinicians with a more reliable, easy to use, and inexpensive approach to quantify post-stroke motor impairment

Economic performance of public investments in irrigation in India in the last three decades

Irrigation programsPublic investmentPerformanceIrrigation systemsRegression analysisOperationsMaintenanceCropsDiversification

Proceedings of the workshop on selected irrigation management issues, Digana Village, Sri Lanka, 15-19 July 1985

Irrigation managementEvaluationRehabilitationWater distributionFarmers' associationsSocial aspectsInstitutional constraintsCanals