It minimizes weight and space which are large constraints for M2 and M4. FrEAc - FrEAc is a series elastic actuator which stands for Fr ameless E lastic Ac tuator. The design was based from FrAP and the mistakes and lessons which that actuator taught. This actuator will be used for M2 and a planar quadruped robot, Corn Dog . A ctuator P rototype is an experiment to apply series elasticity to the hydraulic domain.
Hydraulic actuators are similar to electric motors in that they position causal.
In other words, they are good at position control and not good at force control. However, by introducting springs in series with the output, they alter their causality and can in principle be good at force control. The stirling engine is a fascinating system to study. It includes interaction between many different domains such as fluid, heat and mass transfer, and modulated mechnical junction structures. For the final project of 2.141, Multi-Domain Modeling, I created a working network model of the stirling engine used in 2.670.