This paper proposes an efficient position identification method for mobile robots in the corridor environment in the building using color images and the map information. A robot can usually estimate his position by the motion history, so called dead reckoning. However, there are the cases that the robot position estimation without the motion history is required when the self tracking of his motion is falied, or just after it is powered on, for example. The proposed method is to identify the robot position by itself without the motion history. The method includes next three steps: (1) Map information for the mobile robot is prepared. (2) A color image is handled to detect a vanishing point and to generate an abstracted image. And the robot moves to the appropriate position for the identification, if the robot judges it is impossible to identify the position at the current position. (3) Current robot position is identified by the map information, a vanisging point and an abstracted image. The effectiveness of the proposed method is also shown by the experimental result.
To know positions where the fingers touch an object plays an important role to achieve a stable grasp of an unknown object by a multifingered robot hand. This paper proposes an algorithm for searching for a contact point between a multifingered hand and an unknown object. The algorithm is composed of two phases. One is the approach phase, in which each finger firstly is opened widely and approaches to an object until a part of a finger link is in contact with the object. The other is the detection phase, in which each finger posture is changed with slip while maintaining contact between object and finger. Using two selected postures during the detection phase, we can compute the intersecting point which leads to an approximate contact point. A series of motions during the detection phase is defined as self-posture changing motion (SPCM) , which is also discussed precisely for a general n-link system. Finally, the proposed algorithm is confirmed through simple experiments using a two-fingered robot hand with the capability of joint compliance control.
This paper deals with the design of foot trajectory for a quadruped walking machine. A quadruped walking machine requires both uneven terrain walking capability and high-speed flat surface walking capability. The static walking method was used for uneven terrain walking cases and the dynamic walking method was used for flat plane walking cases. In the case of dynamic walking the relative speed between the foot and the ground caused instability in the balance of the body. We designed foot trajectory based on two points of view. One uses the kinematics of foot motion and the other uses the relationship between joint motion and joint driving torque. This paper also discusses a method for reducing the impact forces upon initial contact with the floor by designing a periodic foot trajectory based on the wave motion of a cam. In this method, the vertical and horizontal motion of the foot trajectory were independently generated using cyclodic motion. We named this trajectory the composite cycloid foot trajectory. We further developed a modified cycloid foot trajectory by smoothing the joint angular acceleration.
The role of the tactile sense of human fingers when handling a pin to insert it into a hole or extract it from the hole was studied. First, the accuracy of the tactile sense in discriminating the orientation of a small bar which was pressed to the index finger was investigated. Secondly, the ability to discriminate the direction of motion was measured when the bar was moved in various directions with constant angular velocity. Thirdly, the ability to discriminate the movement in various directions of a small pin held between a thumb and an index finger was determined. The directional difference limen was found to decrease dramatically when the bar or the pin moved on the fingers in a certain range of speeds. The minimum difference limen of 0.25 degrees was obtained at an angular velocity of 2.8 degrees. These experimental results motivated us to design a force vector sensor. Our sensor model can calculate the force direction as well as the force itself. The detection accuracy for force direction was found to be about 0.27 degrees, which is similar to that of the human tactile sense.
This paper describes the study on free curve interpolation using Clothoidal curve, which gives a new tool for high-speed continuous path control. Control schemes are proposed for the manipulator to pass the given series of points smoothly at a constant-speed. In the problem formulated a criterion of limiting curvature during the entire path of motion. The Clothoid or Cornu spiral is a planar curve which is used in high-way design. Its curvature is proportional to the length of the curve measured from the origin of the spiral. Using Clothoid segments, the point series interpolation method is established and by applying this method to the welding, painting, sealing and bonding robots, it is expected to obtain the faster continuous path motion. Theoretical analysis is given and some calculated results are shown.
Advanced robots for the nuclear power plant maintenance are increasing the complexity in comparison with industrial robots, and severe in condition of use, and are increasing the importance of safety and reliability. In this paper, as a high reliability technology for Advanced Robot, Functional Failsafe control (FFC) is described. FFC isolates the faults, and keeps the minimum function of robot, using the remained potential redundancy of robot, with minimizing of additional parts to robot, at the occurrence of faults. We suggest the three reliability evaluation principles for Advanced robot, then define the FFC in these principles. In the proposed FFC, the method of using an amplifier between two servosystems in common, and the method of stucking the degrees of freedom of robot arm are studied and proved by experiments on the design of FFC. And, a new design method is showed, based on not only the reliability of time, but also the reliability of amount of working. So, we clarified some remained subjects to develop for the FFC.
This paper proposes a general theory for kinematics and dynamics of wheeled mobile robots (WMRs) . This study has two features: 1) The proposed method can deal with various WMR system ranging from typical three or four-wheeled mobile robot to multi-WMR systems where multiple WMRs are connected by joints. A WMR is regarded as a planar linkage mechanism with several ends: wheels correspond to the ends. Generally, a WMR system has active joints such as steering axis, passive joints such as casters and couplers, and driven/non-driven wheels. A model of WMR system called tree structure link covering these configurations is proposed. 2) This theory deals with kinematics and dynamics of WMR including slip of wheels. WMR dynamics is derived regarding frictional force between wheels and the ground as an external force which is a function of the slip speed. When no slip is assumed in wheels, WMR's motion is expressed by kinematics. In this manner, the proposed method is applied systematically on the kinematics when slip can be neglected and the dynamics when slip exists. Furthermore, velocity input dynamics is proposed which gives the motion of WMR when the velocity commands are inputs to active joints and wheels under the condition that wheels slip.
We developed a two dimensional operation testbed for an autonomous free-flying space robot such as an orbital maneuvering vehicle. This system is named ASROT (Autonomous space robot operation testbed) . Basically, ASROT consists of a satellite robot, a target, a host computer and a planar base. A host computer is only used for observation and data gathering of the system. A satellite robot is a satellite which can establish various tasks with a manipulator. A satellite is 620mm (W) ×805mm (H) ×620mm (L) . Its weight is 120 kg. This system is floating on a planar base using air bearings, and is able to fly around using thrusters for position control and a control moment gyro for attitude control. A manipulator is a flexible arm and 1.4m long. This paper proposes an operating system which is needed for real time autonomous control. A satellite robot installs hardware systems such as vision systems, board computers, image processing units, and software systems such as algorithms for path planning.