Clark, Jonathan E

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  • Publication
    Toward a Dynamic Vertical Climbing Robot
    (2006-09-01) Clark, Jonathan E; Goldman, Daniel I; Full, Robert J; Koditschek, Daniel E; Chen, Tao S
    Simple mathematical models or ‘templates’ of locomotion have been effective tools in understanding how animals move and have inspired and guided the design of robots that emulate those behaviors. This paper describes a recently proposed biologically-based template for dynamic vertical climbing, and evaluates the feasibility of adapting it to build a vertical ‘running’ robot. We present the results a simulation study suggesting that appropriate mechanical and control alterations to the template result in fast stable climbing that preserves the characteristic body motions and foot forces found in the template model and in animals. These design changes should also allow the robot to operate with commercially available actuators and in the same power to weight range as other running and climbing robots.
  • Publication
    DESIGN OF A MULTI-DIRECTIONAL VARIABLE STIFFNESS LEG FOR DYNAMIC RUNNING
    (2007-01-01) Galloway, Kevin C; Clark, Jonathan E; Koditschek, Daniel E
    Recent developments in dynamic legged locomotion have focused on encoding a substantial component of leg intelligence into passive compliant mechanisms. One of the limitations of this approach is reduced adaptability: the final leg mechanism usually performs optimally for a small range of conditions (i.e. a certain robot weight, terrain, speed, gait, and so forth). For many situations in which a small locomotion system experiences a change in any of these conditions, it is desirable to have a variable stiffness leg to tune the natural frequency of the system for effective gait control. In this paper, we present an overview of variable stiffness leg spring designs, and introduce a new approach specifically for autonomous dynamic legged locomotion. We introduce a simple leg model that captures the spatial compliance of the tunable leg in three dimensions. Lastly, we present the design and manufacture of the multi-directional variable stiffness legs, and experimentally validate their correspondence to the proposed model.
  • Publication
    Design of a Tunable Stiffness Composite Leg for Dynamic Locomotion
    (2009-08-01) Galloway, Kevin C; Clark, Jonathan E; Koditschek, Daniel E
    Passively compliant legs have been instrumental in the development of dynamically running legged robots. Having properly tuned leg springs is essential for stable, robust and energetically efficient running at high speeds. Recent simulation studies indicate that having variable stiffness legs, as animals do, can significantly improve the speed and stability of these robots in changing environmental conditions. However, to date, the mechanical complexities of designing usefully robust tunable passive compliance into legs has precluded their implementation on practical running robots. This paper describes a new design of a ”structurally controlled variable stiffness” leg for a hexapedal running robot. This new leg improves on previous designs’ performance and enables runtime modification of leg stiffness in a small, lightweight, and rugged package. Modeling and leg test experiments are presented that characterize the improvement in stiffness range, energy storage, and dynamic coupling properties of these legs. We conclude that this variable stiffness leg design is now ready for implementation and testing on a dynamical running robot.