The Supernumerary Robotic Fingers to Compensate and Augment the Human Manipulation Abilities

Besides, traditional prosthesis and exoskeletons, a very challenging research direction is to add robotic limbs to human, rather than substituting or enhancing them. This addition could let the human to augment their abilities and could give support in everyday tasks. These wearable robots are aimed to augment not only the strength and the precision of the human users, but also their range of skills and interactions with the environment. The guiding principles of the robotic design are safety, transparency and user comfort. The advantage of using supernumerary robotic devices is twofold. From one side, this addition can enable humans to augment their capabilities. In the other side, extra limbs can compensate the missing abilities of impaired limbs, e.g., in case of chronic stroke patients. The extra-limbs can extend the human abilities from compensation to augmentation. The main objective of this activity focuses on how a novel wearable assistive technology i.e. supernumerary robotic fingers can be used by chronic stroke patients to compensate for grasping in several Activities of Daily Living (ADL) with a particular focus on bi-manual tasks. The first part of study investigates how to enhance the capabilities of the human hand by means of wearable robotic fingers. Adding wearable robotic fingers could give humans the possibility to manipulate objects in a more efficient way, enhancing our hand grasping dexterity and ability. In this regard, we design and developed a family of extra fingers ranging from fully actuated to underactauated. Together with the design issues related to portability and wearability of the devices, another critical aspect is integrating the motion of the extra fingers with the human hand. We proposed three possible control strategies along with their suitable robotic devices in terms of actuation and sensing capabilities. The first one is based on mapping algorithm able to transfer to the extra fingers a part or the whole motion of the human hand. The second one is based on wearable sensorimotor haptic interfaces which enable the user to control not only the motion of robotic fingers but also perceive the information related to robotic finger status in terms of contact/no contact with the grasped object and in terms of force exerted by the device. The third one is electromyography (EMG) control interfaces to control motion and joints compliance of a supernumerary robotic finger. The second which is also the major part of research explores the real potential of supernumerary robotic fingers as new generation of wearable assistive technology for stroke patients. Stroke and amputation are the two main causes of disabilities of the upper limb. While the scientific community made remarkable advancements in robotic prostheses for upper-limb amputees, only few results are available to compensate for missing manipulation abilities in subjects with paretic upper limbs, such as subjects suffering from chronic stroke or other pathologies. According to the World Health Organization stroke is the disease which leads to most of deaths and high disability problems. Approximately 60% of stroke survivors suffer from some form loss of sensory and/or motor function of the hand. For people with paretic upper limb, most of the attention of the community has been focused on exoskeletons which are very difficult to use because of their limitation in accommodating the subjects anatomical variations due to impairment. Moreover, the poor wearability, in terms of weight and size, make them difficult to use in Activities of Daily Living. One of the biggest challenge of rehabilitation and assistive engineering is to develop technology to practice intense movement training at home. The creation of a functional grasp by means of the extra- fingers enables patients to execute task-oriented grasp and release exercises and practice intensively using repetitive movements. Supernumerary robotic fingers can increase patient’s performances, with a focus on objects manipulation, thereby improving their independence in ADL, and simultaneously decreasing erroneous compensatory motor strategies for solving everyday tasks. The idea of wearable supernumerary limbs as assistive devices is different in nature than other approaches used in rehabilitation and assistive robotics. Extra limbs will provide novel opportunities to recover missing abilities, resulting in improvements of patient’s quality of life. The robotic devices design principles are wearability, ease of use and safety which can further be shaped into bracelet when being not used. The robotic devices are the result of several experiments with the patients conducted in cooperation with a rehabilitation team to incorporate both ergonomics and functional requirements during their design and development process. As a result, the proposed wearable supernumerary fingers are proved to be important as assistive tools in subjects with paretic limbs to recover the manipulation abilities.