Development and characterization of a robotic dynamic activity simulator

A robotic device was developed to recreate the physiologic motion and loading associated with the stance phase of dynamic activities in cadaveric lower extremity specimens. This device, referred to as the Robotic Dynamic Activity Simulator (RDAS), represents the newest version of a previous model, the Dynamic Gait Simulator (DGS). The RDAS simulates muscle function and the motion of the tibia in the sagittal plane over a time-scaled stance phase event that includes heel-strike and toe-off. The behavior of the foot and ankle is a result of the forces developed between the plantar surface of the foot and the force plate, the simulated muscle action and the constrained kinematics of the proximal tibia. The RDAS offers distinct advantages over the DGS, most notably the ability to vary simulation kinematic input parameters to optimize simulations for individual specimens.; To assess the fidelity of the loading environment generated with the RDAS, six cadaver specimens were evaluated during walking simulations. The sensitivity of these simulations to the anthropometric characteristics of subjects from which kinematic data were taken and used as input to drive the device was investigated. Simulations demonstrated excellent repeatability for ground reaction force (GRF), kinematic, and tendon force measures. The kinematics of the foot and ankle during walking simulations were representative of in vivo behavior. The GRF reproduction exhibited improvements over the DGS for some conditions and was representative of in vivo behavior in the sagittal plane, but was dependent on the targeted tibial motion and anthropometric matching between the subjects from whom kinematic input data were derived and the experimental cadaver specimens.