Exoskeleton robotics has ushered in a new era of modern neuromuscular rehabilitation engineering and assistive technology research. The technology promises to improve the upper-limb functionalities required for performing activities of daily living. The exoskeleton technology is evolving quickly but still needs interdisciplinary research to solve technical challenges, e.g., kinematic compatibility and development of effective human–robot interaction. In this paper, the recent development in upper-limb exoskeletons is reviewed. The key challenges involved in the development of assistive exoskeletons are highlighted by comparing available solutions. This paper provides a general classification, comparisons, and overview of the mechatronic designs of upper-limb exoskeletons. In addition, a brief overview of the control modalities for upper-limb exoskeletons is also presented in this paper. A discussion on the future directions of research is included.

Wheelchair upper-limb exoskeletons can offer a new paradigm to assist people with neuromuscular dysfunction in their activities of daily living (ADLs) such as eating and drinking. A key challenge in their control is to ensure safe and comfortable interaction between the human upper limb and exoskeleton. Compared with industrial manipulators, exoskeletons suffer severe kinematic and dynamic uncertainties and external disturbances. Therefore, the selection of optimal control methods that can address the aforementioned challenge is required. In this paper, a method combining PD control, sliding mode control, and fuzzy logic control, i.e., PD based fuzzy sliding mode control, is developed to deal with unmodeled dynamics and external disturbances in the human-exoskeleton system. The sliding mode control can be generally divided by the equivalent control law and the switching control law. For the basic equivalent control part, it adopts the PD controller due to its simplicity in controller design and parameter tuning. For the switching control part, it is replaced by fuzzy logic control to eliminate the chattering of control input such that the smooth motion of the system is achieved. Simulation and experiment results are provided to show the effectiveness of the proposed control method.

Wheelchair mounted upper limb exoskeletons offer an alternative way to support disabled individuals in their activities of daily living (ADL). Key challenges in exoskeleton technology include innovative mechanical design and implementation of a control method that can assure a safe and comfortable interaction between the human upper limb and exoskeleton. In this article, we present a mechanical design of a four degrees of freedom (DOF) wheelchair mounted upper limb exoskeleton. The design takes advantage of non-backdrivable mechanism that can hold the output position without energy consumption and provide assistance to the completely paralyzed users. Moreover, a PD-based trajectory tracking control is implemented to enhance the performance of human exoskeleton system for two different tasks. Preliminary results are provided to show the effectiveness and reliability of using the proposed design for physically disabled people.

This paper presents the EXOTIC- a novel assistive upper limb exoskeleton for individuals with complete functional tetraplegia that provides an unprecedented level of versatility and control. The current literature on exoskeletons mainly focuses on the basic technical aspects of exoskeleton design and control while the context in which these exoskeletons should function is less or not prioritized even though it poses important technical requirements. We considered all sources of design requirements, from the basic technical functions to the real-world practical application. The EXOTIC features: (1) a compact, safe, wheelchair-mountable, easy to don and doff exoskeleton capable of facilitating multiple highly desired activities of daily living for individuals with tetraplegia; (2) a semi-automated computer vision guidance system that can be enabled by the user when relevant; (3) a tongue control interface allowing for full, volitional, and continuous control over all possible motions of the exoskeleton. The EXOTIC was tested on ten able-bodied individuals and three users with tetraplegia caused by spinal cord injury. During the tests the EXOTIC succeeded in fully assisting tasks such as drinking and picking up snacks, even for users with complete functional tetraplegia and the need for a ventilator. The users confirmed the usability of the EXOTIC.

Work-related musculoskeletal disorders (MSDs) are among the most commonly reported issue in Europe. Using robotic exoskeletons to support users in performing heavy industrial tasks can effectively mitigate the work-related MSDs. In this paper, a dynamic model of a hybrid exoskeleton is presented to analyze the assistive effect. The exoskeleton in this study is able to passively support the human shoulder joint and actively support the human forearm movements by providing different levels of assistive torque. With the model, two different tasks are simulated, i.e., an overhead lifting task and a static load transferring task. The results show that the assistive torque provided by the passive spring-loaded mechanism reduces the maximum human upper arm effort by 22.65%. Moreover, the exoskeleton elbow joint’s assistive torque reduces the peak torque of human forearm from [ ] Nm to [ ] Nm. All these results demonstrate the efficacy of the model developed in the simulation and analysis of human-exoskeleton systems.

We propose the use of computer vision for adaptive semi-autonomous control of an upper limb exoskeleton for assisting users with severe tetraplegia to increase independence and quality of life. A tongue-based interface was used together with the semi-autonomous control such that individuals with complete tetraplegia were able to use it despite being paralyzed from the neck down. The semi-autonomous control uses computer vision to detect nearby objects and estimate how to grasp them to assist the user in controlling the exoskeleton. Three control schemes were tested: non-autonomous (i.e., manual control using the tongue) control, semi-autonomous control with a fixed level of autonomy, and a semi-autonomous control with a confidence-based adaptive level of autonomy. Studies on experimental participants with and without tetraplegia were carried out. The control schemes were evaluated both in terms of their performance, such as the time and number of commands needed to complete a given task, as well as ratings from the users. The studies showed a clear and significant improvement in both performance and user ratings when using either of the semi-autonomous control schemes. The adaptive semi-autonomous control outperformed the fixed version in some scenarios, namely, in the more complex tasks and with users with more training in using the system.