Instantaneous robotic gait energetics is evaluated at each joint actuator, and is characterized relative to those of humans. A degree-of-freedom (DOF)-based instrumentation system is designed for instantaneous evaluation of electrical energy expenditure (EE) rates at each DC servomotor, and implemented into a DARwIn-OP biped robot. The robot’s EE rates for the entire lower body are in agreement with its periodic gait cycle, and their trends between gait phases are similar to those of humans. The robot’s cost of transport (COT) as a function of normalized speed is also in agreement with the human COT with respect to its convexity. The contrasting distributions of EE throughout the robot and human DOFs and the robotic COT curve’s considerably large magnitudes and small speed ranges illustrate the energetic consequences of stable but inefficient static walking in the robot versus the more efficient dynamic walking of humans. These characteristics enable the identification of the DOFs and gait phases associated with the inefficiency in the robotic gait, and reflect the differences in the system parameters and gait strategies in terms of the efficiency and stability. The proposed instrumentation system provides a quantitative benchmarking approach.

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