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R2000 Rotopod Robotic Gait Simulator

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Seattle Robotic Gait Simulator

In Seattle, Washington, USA, the Center of Excellence for Limb Loss Prevention and Prosthetic Engineering has been developing the Robotic Gait Simulator (RGS). This is a custom device developed around an R2000 Rotopod which is used to model the interaction between the lower extremity and the ground. The R2000 Rotopod allows the full six-degree of Freedom movement and the power necessary for this simulation to take place.

Purpose:

The primary purpose of the RGS is to simulate gait in vitro using cadaveric specimens. These simulations will serve as a test bed to explore various reconstructive surgical procedures for different foot deformities. By employing measurement techniques too invasive for use with living subjects great insight can be gained into the biomechanical function of the foot and ankle. The prosthetic gait simulation is able to recreate the motion and forces that occur during transtibial prosthetic gait in vitro. This simulation provided a simple test case in which questions regarding RGS methodologies and hardware were investigated and answered, while producing a system that potentially can be employed in the future to study and develop prosthetic feet.

Figure 1 Robotic gate simulator breakdown. The R-2000 Rotopod, with the (A) motors, (B) support frame, (C) prosthetic foot mounted to the frame, (D) force plate, and (E) mobile platform.  The inset shows a drawing of the R-2000 removed from the surrounding steel frame.

Figure 1 The R2000 Rotopod, with the (A) motors, (B) support frame, (C) prosthetic foot mounted to the frame, (D) force plate, and (E) mobile platform. The inset shows a drawing of the R2000 removed from the surrounding frame.

The RGS mimics the gait cycle inversely by holding the tibia still while moving the "ground," represented as a force plate mounted on the six-degree of freedom hexapod robot (R2000). Nine linear actuators in series with nine load cells supply tendon force via liquid nitrogen tendon freeze clamps to the nine main extrinsic tendons of the lower limb. An embedded real time controller performs ground reaction force data acquisition and tendon force feedback control.

Update:

Patrick Aubin, in working with the Department of Veterans Affairs and the University of Washington, has written his MS EE Thesis about Gait Simulation with a 6-DOF robot while working with the R2000. To quote a portion of his Thesis...

A novel six degree of freedom parallel robotic platform was leveraged as the central hardware portion of the RGS (Robotic Gait Simulator). The natural characteristics of a parallel rotopod, including high stiffness to weight ratio, fast yawing action, and tight motion control, matched well with the requirements of the RGS."

For additional details, please see this article.