Physical human–robotic interaction is a crucial area of concern for robotic exoskeletons. Lower weight requirement for the worn exoskeletons limits the number and size of joint actuators, resulting in a low active degree of freedom for the exoskeletons with joint actuators having limited power and bandwidth. This limitation invariably results in reduced physical human–robotic interaction performance for the exoskeleton. Recently several techniques have been proposed for the low active degree of freedom exoskeletons with improved physical human–robotic interaction performance using better load torque compensators and improved active compliance. However, effective practical implementation of these techniques requires special hardware and software design considerations. A detailed design of a new lower body exoskeleton is proposed in this paper that can apply these recently developed techniques to practically improve the physical human–robotic interaction performance of the worn exoskeletons. The design presented includes the exoskeleton's structural design, new joint assemblies and the design of novel 3-D passive, compliant supports. A methodology of selecting and verifying the joint actuators and estimating the desired assistive forces at the contact supports based on human user joint torque requirements and the degree of assistance is also thoroughly presented. A new CAN-based master–slave control architecture that supports the implementation of recent techniques for improved physical human–robotic interaction is also fully presented. A new control strategy capable of imparting simultaneous impedance-based force tracking control of the exoskeleton in task space using DOB-based-DLTC at joint space is also thoroughly presented. Simulation verification of the proposed strategy based on the actual gait data of elderly is presented lastly.

Safe physical human-robotic interaction is a crucial concern for worn exoskeletons where lower weight requirement limits the number and size of actuators to be used. A novel control strategy is suggested in this paper for the low degree of freedom exoskeletons, by combining proposed mechanically decoupled passive-compliant arm-supports with active compliance, to achieve an improved and safer physical-human-robotic-interaction performance, while considering the practical limitations of low-power actuators. The approach is further improved with a novel vectoral-form of disturbance observer-based dynamic load-torque compensator, proposed to linearize and decouple the nonlinear human-machine dynamics effectively. The design of a four-degree of freedom exoskeleton test-rig that can assure the implementation of the proposed strategy is also shortly presented. It is shown through simulation and experimentation, that the use of proposed strategy results in an improved and safer physical human-robotic interaction, for the exoskeletons using limited-power actuators. It is also shown both through simulation and experimentation, that the proposed vectoral-form of disturbance based dynamic load-toque compensator, effectively outperforms the other traditional compensators in compensating the load-torques at the joints of the exoskeleton.

A disturbance observer-based-dynamic load-torque compensator for current-controlled DC-drives, as joint actuator of assistive exoskeletons, has been recently proposed. It has been shown that this compensator can effectively linearize and decouple the coupled nonlinear dynamics of the human-exoskeleton system, by more effectively compensating the associated nonlinear load-torques of the exoskeleton at the joint level. In this paper, a detailed analysis of the current controlled DC drive-servo system using the said compensator, with respect to performance and stability is presented, highlighting the key factors and considerations affecting both the stability and performance of the compensated servo system. It is shown both theoretically and through simulation results that the stability of the compensated servo system is compromised as performance is increased and vice-versa. Based on the saturation state of the servo system, a new hybrid switching control strategy is then proposed to select stability or performance-based compensator and controller optimally. The strategy is then experimentally verified both at the joint and task space level by using the developed four active-degree of freedom exoskeleton test rig.

This paper presents the design and preliminary testing of a full-body assistive exoskeleton AXO-SUIT for older adults. AXO-SUIT is a system of modular exoskeletons consisting of lower-body and upper-body modules, and their combination as full body as well to provide flexible physical assistance as needed. The full-body exoskeleton comprises 27 degrees of freedom, of which 17 are passive and 10 active, which is able to assist people in walking, standing, carrying and handling tasks. In the paper, design of the AXO-SUIT is described. End-user testing results are presented to show the effectiveness of the exoskeleton in providing flexible physical assistance.

In assistive robotics applications, the human limb is attached intimately to the robotic exoskeleton. The coupled dynamics of the human-exoskeleton system are highly nonlinear and uncertain, and effectively appear as uncertain load-torques at the joint actuators of the exoskeleton. This uncertainty makes the application of standard computed torque techniques quite challenging. Furthermore, the need for safe human interaction severely limits the gear ratio of the actuators. With small gear ratios, the uncertain joint load-torques cannot be ignored and need to be effectively compensated. A novel disturbance observer based dynamic load-torque compensator is hereby proposed and analysed for the current controlled DC-drive actuators of the exoskeleton, to effectively compensate the said uncertain load-torques at the joint level. The feedforward dynamic load-torque compensator is proposed based on the higher order dynamic model of the current controlled DC-drive. The dynamic load-torque compensator based current controlled DC-drive is then combined with a tailored feedback disturbance observer to further improve the compensation performance in the presence of drive parametric uncertainty. The proposed compensator structure is shown both theoretically and practically to give significantly improved performance w.r.t disturbance observer compensator alone and classical static load-torque compensator, for rated load-torque frequencies up to 1.6 Hz, which is a typical joint frequency bound for normal daily activities for elderly. It is also shown theoretically that the proposed compensator achieves the improved performance with comparable reference current requirement for the current controlled DC-drive.

The paper presents details of the AAL Call 4 EXO-LEGS project aimed at developing and testing lower body assistive exoskeletons to help elderly persons perform daily living activities independently such as stable standing, sit-to-stand transfers and straight walking. The key components needed have been realized using mobility requirements and design preferences provided by an end user group comprising 118 members via 5 surveys. Modular human-centric concepts are followed for mechanical design, sensing and actuation, system integration, etc., to realize a BASIC exoskeleton prototype able to provide up to 30% power to assist the human perform the intended motions. Two ethical approvals have been obtained to involve end users in the research, development and test phases of the project. To date, 5 test subjects have tested the exoskeleton prototype in walking and the sit-to-stand test; summary results are presented in this paper.

The paper describes the design details for realising the EXO-LEGS assistive exoskeletons for Ambient Assisted Living (AAL) applications based on modelling and simulation studies performed for key mobility functionalities in activities for daily living such as stable standing in open space and straight walking. The results provide the basis for selecting sensors and actuators to develop the needed assistive exoskeletons to help the elderly to stay active and independent for as long as possible.

For ageing individuals, declining physical functional capacity can lead to loss of independence, decreased engagement in the community and reductions in quality of life. As such, solutions that can effectively and affordably supplement older adults’ diminishing functional capacity, and thus facilitate maintained independence and social participation over time are urgently required. The AXO-SUIT project - funded by the European Commission under the Ambient Assisted Living Joint Programme is developing assistive exoskeleton devices for older adults with impaired mobility and/or difficulties in performingactivities of daily living. This paper will report on-going research which aims to identify end user needs, and thus provide inputs to specify the design requirements of the AXO-SUIT exoskeletons. The objectives of this initial questionnaire study are to identify the functional assistance requirements of potential end users of the AXO-SUIT in terms of mobility, reaching and handling, and full-body support for performing activities of daily livingat home and in the wider community. The end user requirements identified will be used to formulate functional specifications for the AXO-SUIT lower-body and upper-body sub-systems, which will ensure that the AXO-SUIT prototypes will provide for the specific mobility, reaching and handling needs of end users, and also to provide useful insights into the perspectives and needs of end users in relation to assistive exoskeletons in general.

The paper presents a research update on the AAL Call 4 EXO-LEGS project aimed at developing lower-body mobility exoskeletons to assist elderly persons to stay independent in their normal daily living activities for as long as possible. The important movement functionalities and key design issues to be included in the process are identified via specifically developed questionnaires and responses from a pan-European end user group set up as part of the project. The user requirements are used together with the recently published ISO safety requirements for personal care robots to perform targeted technical research in the areas of human gait analysis, modelling and simulation, mechanical engineering, embedded system design, and ergonomic user interfacing.