Sujatha Srinivasan

Achieving stability of unmanned, heavy tracked vehicles is challenging, especially under conditions of teleoperation because the remote operator cannot predict the dynamics of the vehicle. This paper proposes a new stability approach that can predict vehicle behavior in real-time and identify the dynamic input parameters that must be controlled to ensure stability and safety of the vehicle during teleoperation. The spatial kinematics and dynamics of tracked locomotion are computed using robotic approach in the form of decomposed serial manipulators and are then combined using suitable kinematic and dynamic constraints. A new stability study approach is presented for computing Multiple zero moment point (MZMP) for the robot since the robot consists of many serial manipulator systems. The stability margins obtained using the relationship between MZMP and combined Zero moment point (ZMP) provides additional information to identify the dynamic parameters that affect stability in the unmanned tracked vehicle during real-time control scenarios.

Purpose: Only 1 in 10 people with disabilities can access assistive devices, underlining the critical need for low-cost assistive products. This paper describes the design evolution of a manual user-operated standing wheelchair (SWC), translating from prototype to product. Methods: The SWC design has been refined over 5 years through multiple iterations based on comments from user trials. The SWC product, Arise, provides standing functionality, facile outdoor mobility, affordability, customisability, and is aesthetically pleasing. A one-time fitting and training ensure optimal effort for operation, correct posture, and comfortable user experience. The SWC accommodates users of different sizes and body weights (up to 110 kg) and minimises user effort with the use of a gas spring. Incorporating discrete adjustments enables customisation while retaining the advantages of mass manufacturing, which is necessary for ensuring affordability. Results: The SWC has been field-tested and well received by over 100 wheelchair users, and Arise was launched recently by the industry partner. Conclusions: It should be noted that RESNA cautions on the use of any standing device without medical consultation. Nevertheless, with appropriate dissemination and awareness, it is anticipated that the affordable SWC product, Arise, will immensely benefit the eligible users and make a difference in their quality of life.Implications for Rehabilitation Provides standing functionality, outdoor mobility, affordability and customisability Accommodates users of different sizes and body weights in a mass-manufacturable design Ergonomic design reduces net user effort during sit-to-stand, stand-to-sit activity Design iterated and refined based on feedback from over 100 user trials.

Motorized designs of stair-climbing wheelchairs available in western countries are heavy and expensive, and hence, unsuitable for developing countries. Manually operated solutions for stair-climbing wheelchairs also tend to be bulky and complex. As stair-climbing is an occasional activity for wheelchair users, having a built-in stair-climbing mechanism results in complexity and redundancy. In this work, an add-on device is envisaged, which requires the wheelchair to be mounted onto the add-on only when stair-climbing is needed. This work developed a Hex-wheel mechanism to address the demerits of the Y-wheel mechanism commonly used in load carriers, as well as to improve usability for stair-climbing. Furthermore, a suitably designed actuation mechanism was applied to the Hex-wheel to enable manual operation. Finally, a prototype of the stair-climbing add-on device was built to validate the developed mechanisms. The force required to operate the device was measured and found to be within 10% of the predicted theoretical value. The novel design provides a solution manually operable by an assistant, which is cost-effective and independent of wheelchair type to improve accessibility in low-resource settings.

Saunders et al.(1953) provided a qualitative description of the contributions to the center-of-mass (CoM) movement. The objective of this work is to analytically quantify and study the kinematic contributions to the CoM movement in gait. A ten-degree-of-freedom anthropomorphic link segment model is used. The choice of segment angles as the generalized coordinates and a subsequent reformulation enabled the decoupling of the expression for CoM position as a summation of the kinematic contributions of individual segments. Using data from literature, the segmental contributions to the CoM displacement are then studied. Results show that the sagittal plane rotation of the shank and thigh of the stance leg are the major contributors to the CoM movement in the vertical and anterior-posterior directions. Additionally, forefoot rolling is seen to be a major contributor to the CoM vertical movement towards the end of the single support phase. In the medio-lateral direction, the frontal plane rotations of the pelvis and the stance leg are seen to be the major contributors. Results validate observations made by other researchers regarding the contributions of the degrees of freedom of the lower limbs to the CoM movement. The methodology can be extended to study asymmetric gait, such as the gait of a prosthesis user, where the properties and kinematics of the prosthetic limb are likely to differ from those of the unaffected side.

Hand neurorehabilitation involves training movements at the forearm, wrist, fingers, and thumb joints. Assisted training of all these joints requires either one complex multiple degree-of-freedom (DOF) robot or a set of simple robots with one or two DOF. Neither of these is economic or clinically viable. This paper addresses this problem with the PLUg and train rObot (PLUTO)- a single DOF robot that can train multiple joints one at a time. PLUTO has a single actuator with a set of passive attachments/mechanisms that can be easily attached/detached to train for wrist flexion-extension, wrist ulnar-radial deviation, forearm pronation-supination, and gross hand opening-closing. The robot can provide training in active and assisted regimes. PLUTO is linked to performance adaptive computer games to provide feedback to the patients and motivate them during training. As the first step towards clinical validation, the device usability was evaluated by 45 potential stakeholders/end-users of the device, including 15 patients, 15 caregivers, and 15 clinicians with standardized questionnaires: System Usability Scale (SUS) and User Experience Questionnaire (UEQ). Patients and caregivers were administered the questionnaire after a two-session training with the robot. Clinicians, on the other hand, had a single session demo, after which feedback was obtained. The total SUS score obtained from patients, clinicians, and caregivers was 73.3 ± 14.6 (n = 45), indicating good usability. The UEQ score was rated positively in all subscales by both patients and clinicians, indicating that the features of PLUTO match their expectations. The positive response from the preliminary testing and the feedback from the stakeholders indicate that with additional passive mechanisms, assessment features, and optimized ergonomics, PLUTO will be a versatile, affordable, and useful system for hand rehabilitation.

Prosthetic feet have generally been designed experimentally by adopting a trial-and-error technique. The objective of this research is to introduce a novel numerical approach for the a priori evaluation of the roll-over shape (ROS) of a prosthetic foot for application in its systematic design and development. The ROS was achieved numerically by employing a non-linear finite element model incorporating the augmented Lagrangian and multi-point constraint contact formulations, a hyperelastic material model and a higher-order strain definition. The Ottobock Solid Ankle Cushion Heel (SACH) foot was chosen to experimentally validate the numerical model. The geometry of the foot was evaluated from optical scans, and the material properties were obtained from uniaxial tensile, shear and volumetric compression tests. A new setup was designed for an improved experimental determination of the ROS, with the inclusion of an extended moment arm and variable loading. Error analysis of the radius of curvature of the ROS between the numerical and experimental results showed the percentage error to be 7.52%, thereby establishing the validity of the model. A numerical design model of this kind can be utilised to vary the input design parameters to arrive at a prosthetic foot with specified performance characteristics effectively and economically. [Figure not available: see fulltext.].

The aim of this work is to conceptualize, design and develop a device to assist the sit-to-stand (STS) motion for disabled and elderly. The device assists the human to stand up from sitting position along the natural trajectory of STS motion. Both human and device are assumed to be functioning fully in the sagittal plane. The natural trajectory of armpit is found for the STS motion using a motion capture system. The coordinates are projected onto a sagittal plane passing through the ankle. A four-bar mechanism is synthesized with four-position motion generation using Burmester curve theory. Assuming quasi-static motion, forces on joints at different time steps are found out. Finite element analysis (FEA) is carried out to determine the required cross section of the links of the structural components of device. Material and dimensions of STS device components are selected, and the device is fabricated. Final experiments of STS device with human show that while using the device, the ground reaction force (GRF) of the human during STS motion decreases by approximately 25%, thereby indicating a reduction in effort of the human for STS by the same order.

Gait analysis is an important clinical tool in the management of locomotion disability arising from orthopedic and neurological conditions and is an active area of research particularly in rehabilitation and sports medicine. The procedure demands dedicated space, thus limiting its usage to indoor environments. In this paper, we present a novel wearable wireless inertial sensor (i-Sens)-based design for estimation of joint angle in the sagittal plane. The i-Sens hardware comprises of triaxial accelerometer, gyroscope sensors, microcontroller and Bluetooth module. It is portable and can be readily used in indoor and outdoor settings. A novel simplified complementary filter algorithm was incorporated in the design for sensor data fusion. Four normal volunteers were chosen to test the sensor; they wore the sensor at knee level on one side, and assessed its performance while walking in both outdoor and indoor environments. The data was transmitted wirelessly through Bluetooth to the data acquisition system. The gait parameters of the subjects were compared with normative reference data. At the initial contact phase of the gait cycle, mean and standard deviation of knee angle was 3.6° ± 3.5°, while the maximum swing phase knee flexion angle was 67.8° ± 4.5°, which is within the normative data range, suggesting accuracy of the joint angle estimation. Hence, i-Sens can be useful for movement analysis of the lower limb. Further clinical trials are required to validate the sensor at different joints (ankle, knee and hip) under various pathological and environmental conditions.

This paper proposes a novel hybrid robotic locomotion and discusses the development of a unified approach that can analyse legged and track modes of locomotion simultaneously. A hybrid locomotion robot designed using a combination of track and legs is suitable for safe manoeuvrability on dangerous uneven terrain, such as in minefields. Modelling a hybrid locomotion is difficult because of the complex kinematics and dynamics of different modes of locomotion (e.g. legged, track, and wheeled), when used simultaneously. The thrust of this work is, establishing the equivalence of a serial manipulator configuration for modelling tracked locomotion similar to legged locomotion. The spatial motion of the hybrid system is analysed by decomposing into serial manipulators and using suitable constraints. A novel approach to study stability is also presented for computing Multiple Zero Moment Point (MZMP) for the proposed robot that consists of many serial manipulator systems. The stability margins are determined using the correlation between MZMP and combined Zero Moment Point (ZMP), which provide information to identify the unstable dynamic sub systems that can then be rectified in real-time operations. In this paper, the design of the robot using leg and track locomotion is described, and the kinematic, dynamic and stability simulations conducted on the hybrid robotic locomotion using the unified approach are presented.

This paper is based on work from the Global Research, Innovation, and Education on Assistive Technology (GREAT) Summit that was coordinated by WHO’s Global Cooperation on Assistive Technology (GATE). The purpose of this paper is to describe the needs and opportunities embedded in the assistive product lifecycle as well as issues relating to the various stages of assistive product mobilization worldwide. The paper discusses assistive technology product terminology and the dangers of focusing on products outside the context and rolling out products without a plan. Additionally, the paper reviews concepts and issues around technology transfer, particularly in relation to meeting global needs and among countries with limited resources. Several opportunities are highlighted including technology advancement and the world nearing a state of readiness through a developing capacity of nations across the world to successfully adopt and support the assistive technology products and applications. The paper is optimistic about the future of assistive technology products reaching the people that can use it the most and the excitement across large and small nations in increasing their own capacities for implementing assistive technology. This is expressed as hope in future students as they innovate and in modern engineering that will enable assistive technology to pervade all corners of current and potential marketplaces. Importantly, the paper poses numerous topics where discussions are just superficially opened. The hope is that a set of sequels will follow to continue this critical dialog.Implications for Rehabilitation Successful assistive technology product interventions are complex and include much more than the simple selection of the right product. Assistive technology product use is highly context sensitive in terms of an individual user’s environment. The development of assistive technology products is tricky as it must be contextually sensitive to the development environment and market as well. As a field we have much to study and develop around assistive technology product interventions from a global perspective.