Modeling and Experiments of Untethered Quadrupedal Running with a Bounding Gait: The Scout II Robot (original) (raw)
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On the Passive Dynamics of Quadrupedal Running
2002
In this thesis, the dynamics of quadrupedal running via the bounding gait is studied. To analyse the properties of the passive dynamics of Scout II, a model consisting of a body and two massless spring-loaded prismatic legs is introduced. A return map is derived to study the existence of periodic system motions. Numerical studies of the return map show that passive generation of cyclic motion is possible. Most strikingly, local stability analysis of the return map shows that the dynamics of the open loop passive system alone can confer stability of the motion. Stability improves at higher speeds, a fact which is in agreement with recent results from Biomechanics showing that the dynamics of the body become dominant in determining stability when animals run at high speeds. Furthermore, pronking is found to be more unstable than bounding, which explains why Scout II shows a “preference” for the bounding gait. These results can be used in developing a general control methodology for le...
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Abstract This paper examines the passive dynamics of quadrupedal bounding. First, an unexpected difference between local and global behavior of the forward speed versus touchdown angle in the self-stabilized Spring Loaded Inverted Pendulum (SLIP) model is exposed and discussed. Next, the stability properties of a simplified sagittal plane model of our Scout II quadrupedal robot are investigated.
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Exploiting the body dynamics to control the behavior of robots is one of the most challenging issues, because the use of body dynamics has a significant potential in order to enhance both complexity of the robot design and the speed of movement. In this paper, we explore the control strategy of rapid four-legged locomotion by exploiting the intrinsic body dynamics. Based on the fact that a simple model of four-legged robot is known to exhibit interesting locomotion behavior, this paper analyzes the characteristics of the dynamic locomotion for the purpose of the locomotion control. The results from a series of running experiments with a robot show that, by exploiting the unique characteristics induced by the body dynamics, the forward velocity can be controlled by using a very simple method, in which only one control parameter is required. Furthermore it is also shown that a few of such different control parameters exist, each of them can control the forward velocity. Interestingly, with these parameters, the robot exhibits qualitatively different behavior during the locomotion, which could lead to our comprehensive understanding toward the behavioral diversity of adaptive robotic systems.