We propose a new real-time self-localization method for an autonomous mobile robot amidst dynamically moving multiple obstacles. This method uses direction of two landmarks and dead reckoning. Conventional method uniquely determines the pose of the robot if at least three landmarks are observed. However, robots often fail to simultaneously recognize three different landmarks in such environment: landmarks are easily occluded. When a robot detects two landmarks and measures angles of their directions, the robot is constrained to be on a circle, so we obtain a set of candidates of robot's pose. Successively the robot moves for a short period, and then observes landmarks. Displacement obtained by dead reckoning is added to pose candidates. Localization error of candidates is evaluated by difference of direction angle to the landmarks: comparison is made between measured direction of landmarks and computed ones. The robot's motion and measurement of landmarks is repeated, and the evaluation of candidates is updated. Finally correct pose is determined uniquely as the one having the smallest error accumulation. Multiple localization process in parallel results robust and accurate localization. The proposed method applies to the soccer robot in the RoboCup Middle-size league and experimental results indicate that the approach is reliable.
In the aged society, it has become more important than in the past to develop technologies for human assist. In this paper, a power assist system for the attendant of an omni-directional transport wheelchair is developed. The applied force of the attendant is measured by a force sensor attached to handles of the wheelchair. The desired motion of the wheelchair is estimated from the output signal of the force sensor using fuzzy reasoning. Then, it is transmitted to four motors of the wheelchair to make it move toward desired direction. The effectiveness of the proposed method is examined by experiments.
A development of stair climbing mobile vehicle to be the base for stair climbing wheelchairs and/or inspection robots is greatly demanded. Several types of the vehicles using crawlers, wheels and legs have been proposed to perform such a stable stair climbing motion. However, conventional vehicles are limited by their mobility, safety, and mechanical size and weight. We propose a new stair climbing leg-wheel hybrid vehicle coined as“Zero Carrier”. The Zero Carrier composed of unified eight prismatic-joint legs, four of which attached active wheels and other four attached passive casters. Proposing Zero Carrier can be designed lightweight and powerful. It can also maintain high stability on stair climbing motion and perform slip-less turning motion. Design of driving mechanisms, sensors, and motion control of the Zero Carrier are then performed and demonstrated its motion by the mechanical model Zero Carrier I.
In this research, the slip margin between an elastic object and a rigid plate is estimated based on the analysis of Hertz contact model. A method of the grip force control using the slip margin is proposed. When an elastic object is pressed and slid slightly on a rigid plate, a partial slip, called“incipient slip”occurs on the contact surface. The slip margin can be estimated based on tribology from the deformation of the elastic object, the tangential force and the radius on the contact surface. The deformation and the displacement of the elastic object are measured by the camera. In addition, the load force can be measured by the force sensor. In this research, a measuring device consists of a camera and a force sensor is developed.“Eccentricity”is defined to estimate the displacement of the elastic object from the shift of the contact area. The grip force is controlled based on the estimated slip margin without knowing the friction coefficient. The proof of the contact stability is obtained. The validity of the proposed method is confirmed by the experiment.
A planning method for linear object manipulation including knotting/unknotting in the three-dimensional space is proposed. Firstly, topological states of a linear object are represented as sequences of crossing points including the crossing type at each crossing point. Secondly, transitions among crossing states are defined. They correspond to operations that change the number of crossing points or permute their sequence. Then, we can generate possible sequences of crossing state transitions, that is, possible manipulation processes from the initial state to a given objective state. Thirdly, a method for determination of actions, that is, grasping points and their moving direction, is proposed in order to realize derived manipulation processes. Furthermore, criteria for evaluation of manipulation processes are introduced in order to reduce the candidates of manipulation plans. Finally, it is demonstrated that our developed system based on the above method can generate and execute manipulation plans for untying an overhand knot.
Force display systems are a kind of human-coexistent robot systems, which share the space with people while working, and which directly touch and display force-senses to their users. They are expected to have much effects and advantages as means of human interface. On the other hand, they are inherently involved a potential hazard in that they may uncontrollably move and hurt operators. We have proposed that safety of robot systems can be estimated quantitatively and ensured mechanically by using a clutch-type actuator. Moreover, we have developed ER actuators and MR actuators that are a kind of clutch-type actuators. In this study, we successed to develop an MR actuator with low inertia, high responsibility, and high torque/inertia ratio, and to develop a 2-D force display system using the developed MR actuator that can present virtual objects with high rigidity and good operativeness.
Tactile sensors for robot hands are important in order to improve the working performance of the industrial manipulating robots' hands. However, as for the most tactile sensors, which have been suggested, these sensors have no flexiblity, and contact areas between the sensors and the objects, are small. Therefore, the pressures of local distributions are obtained from the sensors. Consequently, we proposed a new pressure distribution sensor that combined flexible material and conductive rubber for robot hands. The usefulness of our new sensor is described in this paper.
In this paper, we propose an active vision strategy for the construction of a 3D map in a robot brain from its stereo eye images. We show that the combination of the robot action and image change caused by the action improves the accuracy of the map. If the robot stereo cameras have been accurately calibrated, the obtained reconstruction of the static scene stays stationary. If the calibration is not accurate, the reconstructed scene changes according to the robot action. Therefore, we utilize this change to correct the parameters of the stereo cameras and the 3D map so as to obtain stationary scene under the action. We show the feasibility of this idea as an auto-calibration of robot vision with some simulation experiments and implementation on actual robots.
This paper presents a new method for controlling legged robots during the multi support phase, where the robot may have hand contact with the walls, in addition of feet supported on ground. We present an alternative way to define the zero moment point (ZMP), in order to derive a simpler control method. By selecting a virtual horizontal surface over the robot, we define the ZMP on this surface. The relation between the virtual surface, reaction force and body motion can be formulated in a similar way with the motion of a mass suspended by a wire. The motion of mass can be controlled by manipulating the position of ZMP and by adjusting the position of lifting hook along the virtually defined ceiling. The proposed control algorithm is verified in the real hardware of prismatic joint biped robot. The experimental results show a good performance of the proposed control method.
In this paper, we propose a formation transition algorithm adapting to geometrical features of an environment for multiple autonomous mobile robots. In order to be compatible both keeping formation and avoiding collisions, we emproyee Delaunay diagram. According to geometrical features that apper in Delaunay diagram, the proposing algorithm determs appropriate neighbors in multiple robots. By adding an algorithm to avoid deadlock situations, the proposing algorithm can guarantee ability that all followers can move with an leader without get lost their ways. We have verified the algorith by carrying out simulations and an experiment.