Variants of the Quantized Visibility Graph for Efficient Path Planning

We propose variants of the quantized visibility graph (QVG) for efficient path planning. Conventional visibility graphs have been used for path planning when the obstacles are polygonal. The QVG extends its usability to arbitrarily-shaped objects by representing the obstacles as polygons. We propose QVG variants which represent all combinations of three factors, each with two alternatives: (i) quantization level (fixed-level or multiple-level), (ii) object representation method (inner and boundary cells together or boundary cells only), and (iii) methods used to check whether pairs of points are mutually visible (rotational plane sweep algorithm or sign inequality discrimination (SID) algorithm). In the verification of the efficiency of the proposed QVGs, (i) all QVGs produced the same best path, which was shorter than the convectional algorithms, (ii) computational cost to find the shortest path is lower when using QVGs than when using the convectional algorithms and (iii) the QVG that uses multi-level quantization, partial obstacle representation and SID visibility checking provides the shortest best path and has lower computational cost than all other methods.     

Autonomously generating efficient running of a quadruped robot using delayed feedback control

We report on the design and stability analysis of a simple quadruped running controller that can autonomously generate steady running of a quadruped with good energy efficiency and suppress such disturbances as irregularities of terrain. In this paper, we first consider the fixed point of quasi-passive running based on a sagittal plane model of a quadruped robot. Next, we regard friction and collision as disturbances around the fixed point of quasi-passive running, and propose an original control method to suppress these disturbances. Since it is difficult to accurately measure the total energy of the system in a practical application, we use a delayed feedback control (DFC) method based on the stance phase period measured by contact sensors on the robot's feet with practical accuracy. The DFC method not only stabilizes running around a fixed point, but also results in the transition from standing to steady running and stabilization in running up a small step. The effectiveness of the proposed control method is validated by simulations. MPEG footage of these simulations can be viewed at: http://www.kimura.is.uec.ac.jp/running.