Mostafa Mohammadi

While designing rehabilitation exoskeletons is often realised based on experience and intuition, many processes can be computer-aided. This gives the opportunity to design lighter and more compact constructions. Hence, the devices can be fully wearable and have a wider range of motion. So far, mainly topology optimisation and parametric dimensional optimisations have been used for that. The presented study addresses the problem of automatic selection of the driving systems for exoskeletons. It consists of the literature review of the components used to actuate the joints of such constructions, optimisation algorithm development, and a case study on the EXOTIC exoskeleton. The method includes building a database of motors and gearboxes, computing inverse kinematics of a system to obtain angular trajectories from the task-oriented paths, iteration computing inverse dynamics to compute required torque and the search for the optimal solution according to the defined goal function. This approach enables single joint and multijoint optimisation, with the custom goal function minimising optionally masses, diameters or widths of the selected driving systems. The investigation consists of the 28 simulation trials for EXOTIC exoskeleton to compare results obtained for different aims. Moreover, to visualise the effect, the 1 ^st DOF driving mechanism is redesigned to obtain its minimum width based on the optimisation results. The optimal choice reduced the actuation mechanism mass by 15.3%, while its total dimensions by 17.5%, 8.5% and 26.2%, respectively. The presented approach is easily transferable to any other active exoskeleton and can contribute to designing compact and lightweight constructions. This is particularly important in assistive rehabilitation and can also be used in industrial assistance processes.

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.

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.

It is crucial to increase the independence of severely disabled individuals. Assistive robotics can aid in the desired activities of daily living, including tasks requiring remote performance e.g. grasping remote objects, turning switches on/off, and opening/closing doors. The robot control is compromised by the lack of efficient interfaces for individuals with disabilities and the lack of depth perception. This paper addresses these challenges by presenting the development and evaluation of efficient tongue-based robot interfaces and low-level robot control schemes targeting tele-robotic control through a 2D display. Ten able-bodied participants were successful in completing ten rounds of controlling a JACO robot to perform a pouring water task, using five different control methods, under 2D or 3D visual feedback. The tool-frame based tongue interface layout, L2_TF (with emulated joystick, mode switch button and a “GO” button) improved the 2D visual guided control of the JACO robot compared with the other tongue control methods. The mean trajectory length of completing the task using L2_TF was 3% longer compared with the standard joystick when controlling through 2D. The trajectory length for reaching and grabbing a bottle was shortest for L2_TF compared with all other control methods, including the joystick. The iTongue control layouts performed well in gripping time, showing no significant difference between 2D and 3D. The transition from 2D to 3D resulted in a mean decrease of 27.7% for task completion time across all interfaces. L2_TF and the joystick had the strongest and most similar robustness to the transition between 3D and 2D.

Spinal cord injury can leave the affected individual severely disabled with a low level of independence and quality of life. Assistive upper-limb exoskeletons are one of the solutions that can enable an individual with tetraplegia (paralysis in both arms and legs) to perform simple activities of daily living by mobilizing the arm. Providing an efficient user interface that can provide full continuous control of such a device—safely and intuitively—with multiple degrees of freedom (DOFs) still remains a challenge. In this study, a control interface for an assistive upper-limb exoskeleton with five DOFs based on an intraoral tongue-computer interface (ITCI) for individuals with tetraplegia was proposed. Furthermore, we evaluated eyes-free use of the ITCI for the first time and compared two tongue-operated control methods, one based on tongue gestures and the other based on dynamic virtual buttons and a joystick-like control. Ten able-bodied participants tongue controlled the exoskeleton for a drinking task with and without visual feedback on a screen in three experimental sessions. As a baseline, the participants performed the drinking task with a standard gamepad. The results showed that it was possible to control the exoskeleton with the tongue even without visual feedback and to perform the drinking task at 65.1% of the speed of the gamepad. In a clinical case study, an individual with tetraplegia further succeeded to fully control the exoskeleton and perform the drinking task only 5.6% slower than the able-bodied group. This study demonstrated the first single-modal control interface that can enable individuals with complete tetraplegia to fully and continuously control a five-DOF upper limb exoskeleton and perform a drinking task after only 2 h of training. The interface was used both with and without visual feedback.

Complete tetraplegia causes paralysis from the neck down, resulting in a need for constant care and lack of doing activities of daily living by yourself. Exoskeletons have enabled some rehabilitation and movement of paralyzed limbs but are often prohibitively large and heavy. This project aimed to redesign the wrist of the tongue controlled EXOTIC exoskeleton, making it compact and light. The new design used tendon-based technology, removing the motor from the forearm as well as employing 3D print. A proof-of-concept for the new design was obtained through a case study with three subjects.

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.

Individuals with tetraplegia have a challenging life due to the lack of independence and autonomy. Assistive robots have the potential to assist with the activities of daily living and thus improve the quality of life. However, an efficient and reliable control interface for severely disabled individuals is still missing. An intraoral tongue-computer interface (ITCI) for people with tetraplegia has previously been introduced and tested for controlling a robotic manipulator, in a study deploying discrete tongue robot mapping. To improve the efficiency of the interface, the current study proposed the use of virtual buttons based on the ITCI and evaluated them in combination with a joystick-like control implementation, enabling continuous control commands. Twelve able-bodied volunteers participated in a three-day experiment during which they controlled an assistive robotic manipulator by means of the tongue to perform two tasks: Pouring water in a cup (PW) and picking up a roll of tape (PUT). Four different tongue-robot mapping methods were compared. The results showed that using continuous commands reduced the task completion time by 16% and the number of commands of the PUT test by 20% compared with discrete commands. The highest success rate for completing the tasks was 77.8% for the PUT test and 100% for the PW test, both achieved by the control methods with continuous commands. Thus, the study demonstrated that incorporating continuous commands can improve the performance of the ITCI system for controlling robotic manipulators.