Path Tracking by a Mobile Robot Equipped with Only a Downward Facing Camera

This paper presents a practical path-tracking method for a mobile robot with only a downward camera facing the passage plane. A unique algorithm for tracking and searching ground images with natural texture is used to localize the robot without a feature-point extraction scheme commonly used in other visual odometry methods. In our tracking algorithm, groups of reference pixels are used to detect the relative translation and rotation between frames. Furthermore, a reference pixel group of another shape is registered both to record a path and to correct errors accumulated during localization. All image processing and robot control operations are carried out with low memory consumption for image registration and fast calculation times for completing the searches on a laptop PC. We also describe experimental results in which a vehicle developed by the proposed method repeatedly performed precise path tracking under indoor and outdoor environments

Development of a video-rate range finder using dynamic threshold method for characteristic point detection

This study develops a video-rate stereo range finding circuit to obtain the depth of objects in a scene by processing video signals (R, G, B, and brightness signals) from binocular CCD cameras. The electronic circuit implements a dynamic threshold method to decrease the affect of signal noise in characteristic point detection, where a video signal from each CCD camera is compared with multiple thresholds, shifting dynamically by feeding back the previous comparison result. Several object depth measurement experiments for simple indoor scenes show that the dynamic threshold method gives high acquisition and correct rates of depth data compared with those by a fixed threshold method for the video signals and a relative method for R, G, and B signals utilized in the authors' previous range finders

Backstepping Control for a Tandem Rotor UAV Robot with Two 2-DOF Tiltable Coaxial Rotors

The study of a fully actuated multi-rotor UAV robot is very important in the field of infrastructure inspection because it needs a dexterous motion, such as hovering in a special fixed attitude, etc. This paper presents a backstepping control method for a simplified fully actuated model of a tandem-rotor UAV robot with two 2-DOF tiltable coaxial rotors. A MIMO vectorial backstepping approach is adopted here because the input distribution matrix is a square and nonsingular matrix. The two-stage control method based on the Lyapunov second method is presented to stabilize the position and attitude of the whole system. The static control allocation problem is also solved by using a Moore-Penrose pseudo-inverse. Finally, two simulations are demonstrated to verify the performance of the proposed control method, where one is a stabilizing problem in which all the desired position and attitude are to be constant, whereas the other is a trajectory tracking problem in which the desired positions are time-varying while the desired attitudes are to be constant

Obstacle avoidance by changing running path for an autonomous running vehicle applying visual servoing

This paper describes an improved running control algorithm based on the visual servoing in consideration of the turning back of a running path to avoid an obstacle on the path by changing the running path. This paper also describes an experimental autonomous running vehicle to demonstrate the algorithm. As a vision sensor, the vehicle equips with a video-rate stereo rangefinder which processes color images from stereo CCD cameras and is developed in the authors' laboratory. From the several basic autonomous running experiments, it is concluded that the experimental vehicle runs smoothly any planned path composed of several teaching routes by transferring routes. It is also concluded that the vehicle can turn back on a path including turning back of route transference</p

Positioning device for outdoor mobile robots using optical sensors and lasers

We propose a novel method for positioning a mobile robot in an outdoor environment using lasers and optical sensors. Position estimation via a noncontact optical method is useful because the information from the wheel odometer and the global positioning system in a mobile robot is unreliable in some situations. Contact optical sensors such as computer mouse are designed to be in contact with a surface and do not function well in strong ambient light conditions. To mitigate the challenges of an outdoor environment, we developed an optical device with a bandpass filter and a pipe to restrict solar light and to detect translation. The use of two devices enables sensing of the mobile robot’s position, including posture. Furthermore, employing a collimated laser beam allows measurements against a surface to be invariable with the distance to the surface. In this paper, we describe motion estimation, device configurations, and several tests for performance evaluation. We also present the experimental positioning results from a vehicle equipped with our optical device on an outdoor path. Finally, we discuss an improvement in postural accuracy by combining an optical device with precise gyroscopes

Control of a Quadrotor Equipped with a Fixed-wing by Tilting Some of Four Rotors

Abstract—Unmanned aerial vehicles (UAVs) are beingexpected to be used for the vegetational observation and theinformation collection of disaster sites. Especially, rotorcraftstypified by helicopters are attractive, because they are able tohover and achieve vertical take-off and landing (VTOL).However, rotorcrafts have a disadvantage that it cannot have along-distance flight, because they fly by the thrust of upwarddirection. Aircrafts with tilt rotors are developed in order toovercome such disadvantages. Such aircrafts can be hovering andtake a VTOL and also a long-distance flight by changing theangle of the rotor. In this research, it is aimed at proposing aVTOL-type UAV with a fixed-wing and four tiltable rotors andcontrolling it.</p

Localization of a Walking Robot Using a Laser Speckle Odometry

In this study, we propose a laser odometry tolocalize an underwater walking robot. In the laser odometryusing optical sensors, motion is estimated by tracking laserspeckle patterns. However, measurement error increases whenthe sensor is tilted. We describe the overview of our walkingrobot with the sensor, the principle of laser odometry, and theexperimental result