Abstract
Current microprocessor controlled prostheses for transfemoral amputees consist of two main functional components: a knee joint and an ankle-foot joint. These normally function as isolated joints without any feedback about the state of the other joint. In this research an approach investigating the system integration of the whole transfemoral limb has been undertaken. An integrated limb system was built based on two already existing but ‘stand-alone’ prosthetic joints by creating an appropriate control system and communication architecture. Two additional functionalities that require inter-joint communication were implemented: standing mode and ramp descent mode to support those challenging situations for transfemoral amputees. The development and biomechanical assessment of the ramp descent mode were undertaken to establish if integrated inter-joint control has the potential to change gait characteristics compared to non-integrated isolated single-joint control. Four different conditions (no braking, braking of foot, braking of knee and braking of the whole limb) were assessed trying to replicate non-integrated and integrated control in a systematic manner. The biomechanical assessment from the two amputee studies conducted revealed that braking of the whole limb showed the largest differences compared to the different conditions with some reaching statistical significance however the findings of the gait studies were inconsistent. There were some indications of increase of braking ratio, reduction in propulsive impulse and decrease of self-selected speed however not all results could be replicated. Overall this could indicate a more controlled ramp descent. Overall the research showed the potential of integrated coordinated transfemoral limb control and its benefits in one particular gait situation. For future work it is proposed to refine the ramp descent mode and focus on additional functionalities such as ramp ascent using the integrated approach. Integrating the socket and residual stump control into the integrated control system might provide a completely new approach of intuitive control.