Kinematic Trade-offs in Elastic Mechanisms

Elastic spring mechanisms are used both in biology and robotics to drive ultra-fast movements that outperform direct muscle-driven or motor-driven systems. One challenge in comparing the kinematic performance of spring-driven versus motor-driven systems is the many ways in which performance can be measured - e.g. maximum velocity, take-off duration, and maximum power output. We explored trade-offs between these different metrics of kinematic performance using a simplified model for both spring-driven and motor-driven systems. We found that hybrid systems with a motor and spring in series can balance trade-offs between high velocity and short take-off duration. Surprisingly, we found that tuning the stiffness of the system's spring to maximize stored elastic energy does not necessarily maximize the power output. These results suggest that the design of elastic mechanisms can be fine-tuned to optimize specific performance objectives.