Safety and energetic efficiency in wearable robots. Innovative actuated devices

Wearable robots are person-oriented robots worn by human operators and aimed at assisting users' movements. They provide human limbs with physical support and functional supplement by enhancing the strength of wearer's joint in order to give people with mobility impairments the chance to regain the ability to walk over the ground, upstairs and downstairs, or to augment the performance of able-bodied wearers. Research in the field of wearable robots started in late 1960s in USA and Yugoslavia for military and medical purposes respectively and even though a lot of progresses have been done especially in the last two decades, a lot of challenges are still associated with them and several research contributions aim to overcome current limitations. Portability is one of the main requirement of wearable robots. It is conceived as the capability to be worn and carried around by users who need to be supported in a large variety of operational scenarios and for an extended length of time. Comfortable and ergonomic mechanical structures, as well as efficient and convenient actuation systems ensure portability of these robotic devices. Current actuation technologies challenge the development of portable and effective wearable robots. Actuation of these devices must fulfil often opposing requirements which are hard to conciliate at the same time. They must be powerful enough for providing the high peak of torque and power demanded in a gait cycle of locomotion tasks, they should have a low energy consumption in order to increase the operating range of the device and finally they must be as small and lightweight as possible in order to decrease the metabolic expenditure and facilitate portability. Efficient actuatosr capable of exploiting the passive dynamic of human walking by storing and releasing energy according to the phases of the gait cycle, can reduce the energy requirement of the motor leading to the development of long lasting and lightweight systems. More than the joint power augmentation, also the balance challenges the development of portable wearable robots. Most of wearable robots have been not primarily designed to assist balance and users have to count on conventional assistive technologies, such as canes or crutches, to prevent the risk of falling. However, these external assistive devices are hold in the hands and this is not convenient for people with limited strength in upper limbs. Furthermore, they can interfere with balance in some situations and they reduce the effectiveness of wearable robots in comparison to wheel chairs. Multi degree of freedom actuated joints would improve gait stability, despite the increase of the weight and of the control complexity. Robotic assistive technologies, such as moment exchange actuators, have the potential of providing balance assistance to the wearer in his daily life actions and consistently with human balance control. They detect the subject�s loss of balance and exert corrective actions to avoid or delay the risk of falling. Balance assistive devices can either be included in powered wearable robots or be worn separately by subjects suffering balance disorders to control and improve their balance. This thesis gives a contribution to the development of portable wearable robots in terms of energetic efficiency and safety. The current actuation technologies for joint power augmentation and balance assistance have been investigated with the aim of finding novel solutions that could improve the portability of wearable robots for human locomotion assistance and human strength augmentation. The investigation resulted in the development of two concepts of actuated devices focused on enhancing joint strength and on balance compensation respectively.