Modern societies are privileged with high quality of life and high average life expectancy, mainly due to the improvement of living conditions, development of medicine and improvement of medical care. Consequently, research for new, improved and faster rehabilitation therapies is a requirement for these populations and for researchers themselves. A target of these rehabilitation therapies is mobility, since it is one of the common and relevant human physical activities. Without it, daily life activities such as getting up from bed in the morning, walking to the bathroom, going for a walk or even working can be drastically affected. Furthermore, lack of mobility can lead to a deprived social life and a decrease in communication and mental health. Our body health is also affected, since our muscles can deteriorate without mobility. As mentioned in [12], human motor impairment can result in social and work (10% in working age) exclusion, early retirement, costly medical treatments and social assistance. Therefore, rehabilitation therapies regarding the improvement of people’s mobility can be a goal to robotics rehabilitation, once it can reinforce and/or restore the human performance concerning mobility.
Therefore, lower-limb robotic devices are an excellent research opportunity in the field of assistive technologies to motor rehabilitation. Consequently, therapies assisted by these wearable devices for treating lower limb impairments have been increasingly used in addition to conventional therapeutic approaches, in the fields of rehabilitation and assistance [1][13]. Particularly, powered exoskeletons and orthoses have been highlighted, as they increase human motor function, and rehabilitate through task-oriented training.
The main goal of these robotic devices is to have active technologies, ultimately controlled by the user, to both increase human motor function, and rehabilitate through task oriented and repetitive gait training. One key feature of these technologies, is the ability to act according to patients’ intention by applying assist as need (AAN) strategies.
In the backbone of these technologies, low-level assistive strategies are responsible for controlling the actuators that allow the execution of the AAN strategies and, consequently, of the rehabilitation therapies. Hence, these devices should be embedded with efficient, robust, and adaptive low-level controllers, capable of performing an effective and reliable actuation so the reestablish of the abnormal gait pattern can be successful.