Takashi Tsubouchi

Outdoor navigation of a mobile robot between buildings based on DGPS and odometry data fusion

The authors aim at map based outdoor navigation of a mobile robot. In navigation, robot position is fundamentally obtained by odometry. However, the position is misaligned as the robot moves because odometry has cumulative error. DGPS measurement data may cancel its position error. The framework of EKF is used for the modification and the fusion between odometry and DGPS measurement data. The DGPS measurement data, however, could have large error because of multipath near buildings. In this paper, the authors propose a method which eliminates erroneous DGPS measurement data when odometry robot position is fused, and confirm the validity of this approach.

Differential GPS and odometry-based outdoor navigation of a mobile robot

This paper describes outdoor navigation for a mobile robot by using differential GPS (DGPS) and odometry in a campus walkway environment. The robot position is estimated by fusion of DGPS and odometry. The GPS receiver measures its position by radio waves from GPS satellites. The error of GPS measurement data increases near high buildings and trees because of multi-path and forward diffractions. Thus, it is necessary to pick up only accurate DGPS measurement data when the robot position is modified by fusing DGPS and odometry. In this paper, typical DGPS measurement data observed near high buildings and trees are reported. Then, the authors propose a novel position correction method by fusing GPS and odometry. Fusion of DGPS and odometry is realized using an extended Kalman filter framework. Moreover, outdoor navigation for a mobile robot is accomplished by using the proposed correction method.

A development of a new mechanism of an autonomous unicycle

We propose a new mechanism of a unicycle. One feature of this robot is the shape of the wheel which is similar to a rugby ball. The other feature is that the body is separated into upper and lower parts. We give the details of a mechanism of the robot, simple controller system, and some results of a performance experiment using the designed controller. We present experimental results that show that the robot can move in a straight line and steer itself by the proposed mechanism.

Map assisted vision system of mobile robots for reckoning in a building environment

The authors have constructed a self-contained intelligent robot on which ultrasonic range finders are installed. A sensory system with sensing ability appears necessary; the authors propose a vision system for a mobile robot that meets real time requirements. In the vision system, a color image provids actual image information and map information is also utilized for reckoning in a building environment. The key point is that matching between image and map information is performed by using highly abstracted information from the image and also from the map. The constitution of the vision system and experimental results are described.

Outdoor map building based on odometry and RTK-GPS positioning fusion

The final objective of the authors is to realize mobile robot navigation in walkway of outdoor environment. The path along the walkway which is measured correctly together with landmarks must be given in the framework in this paper. The robot identifies its position by means of odometry, DGPS and laser range finder (LRF) during the motion along the path. This work contributes to the map building of landmarks along the walkway. To make the map, RTK-GPS, odometry and LRF are used for the sensory devices and Kalman smoothing technique is also incorporated to interpolate trajectory of the scanning LRF equipment between the two point that RTK-GPS measurement took place. The scanning by LRF is performed to acquire the 3-D shape of objects along the walkway. The trajectory presumed properly and well organized shapes of the objects are reconstructed.

Approach Path Generation to Scooping Position for Wheel Loader

Our group developed a method of path generation for wheel loaders as part of our ongoing research on the autonomous loading operation of wheel loaders at surface mines and construction sites. The path connecting the present vehicle position and scooping position consists of clothoid curves and straight lines. Each line segment is optimized in a path generation procedure. A simplified model of the pile shape and bucket trajectory is used to determine the scooping direction based on an estimation of the resistance force applied on the bucket during the scooping motion. We applied the proposed method in an experimental model. A stereo-vision system was used to measure the shape of the pile and the scooping direction that imposed the least moment on the bucket was selected as the scooping position. This method generates an appropriate path for the wheel loader.

3-D object modeling by a camera equipped on a mobile robot

This paper describes 3-D shape modeling performed by a mobile robot. We propose a method in which the robot in the real environment acquires the accurate shape and constructs a 3-D model of an object using Computer Vision techniques under the condition that position and shape of the object is unknown. 3-D modeling is performed from image streams which are captured by a camera placed on the robot. The results show the effectiveness of our method.

Fusion of dead-reckoned positions with a workspace model for a mobile robot by Bayesian inference

Estimation of the position based on a conventional dead-reckoning for a mobile robot intrinsically contains cumulative errors. In relation to this, large nonzero probability of its error distribution is occasionally found even outside the workspace, because the dead-reckoning takes no account of the unreachability outside the workspace. This paper presents a new fusion algorithm for dead-reckoning, in which both the dead-reckoned position and the knowledge of the closed workspace are fused by means of Bayesian inference. This algorithm produces zero probability outside the workspace theoretically. Through a computer simulation, the effectiveness of the proposed algorithm is confirmed.<<ETX>>

A straight pipe observation from the inside by laser spot array and a TV camera

This research work contributes to an active vision system for an gas pipe inspection robot moving inside of the pipe. The robot must be able to know what shape of the pipes where the robot is moving. The shapes of the pipe include straight, L or T. Also, when it is moving in the straight section, the robot must detect the relative angle with respect to its principal axis. The authors propose to use a laser spot array and TV camera for the vision sensor, which can find the three dimensional position of each spot on the surface of the pipe by means of triangulation. The shape of the pipe inside can be reconstructed by the information of the camera. A method is also presented to distinguish the shape whether it is straight or not.

A simple driving device for a vehicle implementation and evaluation

We are interested in the operation facilities of vehicle that are simple even for persons who are not experienced in vehicle operation. One idea simplifying the vehicle operation is to separate the operation from the mechanism of the vehicle. In this system, the human operator specifies a temporary goal position of the mobile robot by touching the monitor in which front view images are displayed. The robot then travels toward this goal position. The path to the goal position is generated by the system and shown on the front view images. Therefore, the operator need not practice how to operate steering wheel or accelerator. We have constructed an experimental setup and evaluated it by controlling the robot.