Position tracking control in torque mode for a robotic running foot for footwear testing

Available automatic footwear testing systems still lack flexibility and bio-fidelity to represent the human foot and reproduce the wear conditions accurately. The first part of this article introduces a new design of the robotic running foot for footwear testing using cable conduit mechanisms. This robotic running foot is integrated with an upper leg mechanism to form a complete integrated footwear testing system. The cable conduit mechanisms help remove the bulky actuators and transmissions out of the fast-moving robotic foot. Thus, this robotic running foot design not only allows high-power actuators to be installed, but also avoids a significant dynamic mass and inertia effects on the upper leg mechanism. This means that the integrated footwear testing system can have multiple powered degrees of freedom in the robotic running foot and simulate much higher human running speeds than other available systems. However, cable conduit mechanisms cause significant challenges in control approaches, especially in high-speed systems, due to their nonlinear transmission characteristics. Furthermore, the robotic running foot actuators must operate in a torque/force control mode to reproduce the foot–shoe interaction during gaits while it is critical to control the foot joints’ position in the swing phase of gaits. The latter part of this article presents a study on position tracking control in torque mode for the robotic running foot joints using adaptive and proportional–integral–derivative control designs to evaluate the system’s ability to mimic the human foot kinematics in running. Both controllers proved their effectiveness, implying that the proposed control approach can be implemented on the integrated footwear testing system to control the foot joints’ position in the swing phase of running gaits.