The restoration of gait for patients with impairments of the central nervous system (CNS), like, e.g., stroke, spinal cord injury (SCI) and traumatic brain injury (TBI) is an integral part of rehabilitation. The rehabilitation of CNS impairments usually takes several months at minimum and its outcome often influences whether a patient can return home or to work. Particularly stroke is the leading cause for disability in all industrialised countries; the incidence is approximately one million patients in the European Union each year [1, 2]. Modern concepts of motor learning favour a task specific training, i.e., to relearn walking, the patient should ideally train all walking movements, needed in daily life, repetitively in a physically correct manner . Conventional training methods based on this approach proved to be effective, e.g., treadmill training , but they require great physical effort from the physiotherapists to assist the patient – so does even more training of free walking guided by at least two physiotherapists. Assisted gait movements other than walking on even floor, like for instance stair climbing, are practically almost impossible to train, due to the overstrain of the physiotherapists. Robotic haptic gait training devices may offer a solution to fill this gap and lead to an intensified patient training plus a relief for the physiotherapists from strenuous work.
Different rehabilitation robotics research groups already developed a number of robotic gait rehabilitation devices with haptic features [5, 6], all of them are based on the exoskeleton principle and need to be operated in combination with a treadmill on which the patient walks. The exoskeleton robot then substitutes the physiotherapist and moves the patients’ legs. Due to their operating principle, all of these machines are restricted to training of walking on even ground and do not allow physical interaction between patient and physiotherapist during training.
In contrast, it was a major goal of the HapticWalker project to develop a robotic walking simulator, which offers training of arbitrary and freely programmable foot motions. This lead to the development of a machine based on the principle of programmable footplates. On this type of machine the patients’ feet are attached to two footplates, on which he stands. The footplates are located at the end-effectors of two robot arms which carry the patients’ body weight and move his feet along the foot trajectories. In addition to daily life walking trajectories like walking on a plane floor or stair climbing, the machine dynamics should allow the simulation of asynchronous events, such as stumbling or walking on rough ground, which require high acceleration capability.