Obstacle avoidance with translational and efficient rotational motion control considering movable gaps and footprint for autonomous mobile robot

This paper presents a sensor-based real-time obstacle avoidance method for an autonomous omnidirectional mobile robot based on simultaneous control of translational and efficient rotational motion considering movable gaps and the footprint. Autonomous mobile service robots that have been developed in recent years have arms that work and execute tasks. Depending on the task using moving parts, the shape of the robot (i.e., the footprint) changes. In this study, to improve the safety and possibility of reaching a goal even through a narrow gap with unknown obstacles, a sensor-based real-time obstacle avoidance method with simultaneous control of translational and efficient rotational motion (without unnecessary rotational motion) based on the evaluation of movable gaps and the footprint is proposed. To take account of the anisotropy footprint of the robot, multiple-circle robot model is proposed. In this paper, a novel control method based on fuzzy set theory is presented. To verify the effectiveness of the proposed method, several simulations and experiments are carried out.

     

Simultaneous Measurements of an Ultrasound and a Torsional Oscillator for Pressurized 4He in a Nanoporous Glass

Recently, torsional oscillator (Yamamoto et al. in Phys. Rev. Lett. 93:075302, 2004) and ultrasound (Kobayashi et al. in AIP Conf. Proc. 128:797, 2007) measurements were carried out for pressurized ⁴He filled in a nanoporous glass (Gelsil), and the superfluid transition temperature T _C shows a different pressure dependence. Thus motivated, we have performed simultaneous measurements with a torsional oscillator and with ultrasound for pressurized ⁴He in Gelsil. T _C is in agreement between the two techniques at all pressures, and the superfluid component above 0.5 K shows most of the same temperature dependence. Furthermore, it was found that the χ-factor (the fraction of superfluid which remains locked to the substrate ) is independent of measuring frequency between the torsional oscillator (kHz-order) and the ultrasound (MHz-order) ranges.