Conceptual design of a gait simulator for testing lower-limb active prostheses

In the recent past, lower-limb prostheses technological advancement mostly concerned the possibility of integrating ever smaller and more powerful electronic components instead of new materials and topologies. For instance, the electronic knee prosthesis guarantees maximum yield by mean of sensors and actuators that allow to adjust in real time the characteristics and thus the response of the device itself. Regardless of the solution adopted, control strategies constitute the most critical aspect of the modern prosthetic design. In this context, hardware-in-the-loop simulation concept represents a useful approach for design optimization of intelligent knee controllers. Indeed, it allows to integrate the user behavior into the prosthetic development process removing the limits related to in vivo tests. However, such approach requires complex mechanical robot design and sophisticated control strategies. This paper presents the conceptual design of a bench for simulating both the stance and the swing phase according to sought gait standards. The mentioned definition process is performed in order to overcome the most significant challenges of gait simulators, that are operating at near physiologically correct velocities, inputting full scale ground reaction forces and simulating motion in all three planes (sagittal, coronal and transverse). Furthermore, the research presented in this paper addresses the question of how to satisfy the mentioned behavior requirements in such a way to ensure correct dynamics reproduction of the phenomenon using a six-axes industrial robot.