Biped robots with passive elements
Biped Robots with Elastic and Dissipative Elements in Terms of Energy Consumption and Stability Considerations
The project „Elastische Mechanismen“ (Elastic Mechanisms, UL 105/32) is part of the DFG package proposal „Natur und Technik intelligenten Laufens“ (Nature and Technology of intelligent walking, DFG PAK 146). The aim of the project is to investigate the influence of elastic and dissipative elements on technical bipedal locomotion. This is archived in cooperation with the Locomotion Laboratory (www.lauflabor.de), University of Jena.
In technical two-legged locomotion two contrary concepts dominate. The first one concerns humanoid robots, with actuated degrees of freedom. For this kind of robot, among other things, the following two topics are important: enhancement of the system stability and reduction of energy consumption, especially when thinking of humanoids working autonomously within a human environment. The second concept concerns robots based on the idea of limit-cycle-walking. The versatility of these robots is very limited. Nevertheless, due to their passive-elastic elements they are able to walk with a very energy efficient gait.
In this project we are investigating a humanoid robot model with adapted actuation. Therefore, we want to take advantage of the benefits from the concept of limit-cycle-walkers,
namely passive-elastic elements for energy storage. Thus, the investigated multibody simulation model is based on the topology and geometry of the humanoid robot Johnnie. For the actuation of the robot, different concepts are studied:
The first one is the biologically inspired arrangement, based on the JenaWalker II model from our cooperation partners from the Locomotion Laboratory, University of Jena. For this actuation version several muscle groups are represented by spring-damper elements with linear and progressive characteristics. The model is driven by a dc-motor actuating the thigh only.
For the second concept the joints, which are originally actuated with a drive-chain based on industrial robot, are extended using spring- damper elements. These can be placed serial or parallel to the power-train unit.
By implementing passive elements into the system many questions arise. These concern e.g. a proper set of suitable spring-damper parameters, unknown facts about the robot dynamics, stability and control. Therefore, numerical parameter determination based on optimization as well as shooting methods for the identification of limit cycle motion are applied. The resulting system characteristics are analyzed with respect to cost of transportation and stability considerations.