Naoji Shiroma

Nonholonomic control of a three-DOF planar underactuated manipulator

Control of a manipulator with a passive joint which has neither an actuator nor a holding brake is investigated. The manipulator has three degrees of freedom in a horizontal plane, with the third joint being passive. The dynamic constraint on the free link is shown to be second-order nonholonomic. Controllability of the system is proved by constructing examples of the input trajectories from arbitrary initial states to arbitrary desired states, considering the motion of the center of percussion of the link. Trajectories for positioning are composed of simple translational and rotational trajectory segments. The trajectory segments are stabilized by nonlinear feedback control. Simulations and experimental results show the effectiveness of the planned trajectory and the feedback control law.

Study on effective camera images for mobile robot teleoperation

The effectiveness of different camera images for mobile robot teleoperation is investigated. During a robot teleoperation where the operator can only control the robot through observing the camera images rather than direct-view control, the information provided by the images must be sufficient enough to allow the operator to perform the remote control efficiently. In order to understand which kind of camera images are most effective for robot teleoperation, we have conducted several experiments to examine their validness. The experimental results indicated that an image where the robot is positioned in the center of the camera view with clear survey of the surroundings shows high efficiency in remote control of a mobile robot.

Feedback control of a 3-DOF planar underactuated manipulator

Feedback control of a manipulator with a passive joint which has neither an actuator nor a holding brake is investigated. The manipulator has three degrees of freedom in a horizontal plane, with the third joint being passive. The dynamic constraint on the free link is 2nd-order nonholonomic. A trajectory for positioning is composed of simple translational and rotational trajectory segments. The trajectory segments are stabilized by nonlinear feedback, considering the motion of the center of percussion of the free link. Simulation results show the effectiveness of the feedback control.

Development of a high mobility wheeled rescue robot with a 1-DOF arm

Human rescuers, who carry out urban search and rescue (USAR) missions, frequently enter dangerous zones to search for survivors. In these zones, rescuers life may be threatened. For this reason, rescue robots are expected to become useful work partner for urban search and rescue missions. This paper presents platform design of FUMA, which is a four-wheeled rescue robot with a 1-DOF arm for environment information gathering. Only one arm of FUMA has two benefits for both mobility and teleoperation. Using this arm, FUMA can climb higher obstacles than simple four-wheeled robot. Human rescuers can operate FUMA at a safe distance while the missions are carried out. To teleoperate robot systems efficiently, the key is the interface between the robot systems and operators. During rescue operation, an operator of FUMA usually relies on the images from two fish-eye cameras installed at the top of the arm, as they provide wide images of the environment with the robot included in those views.

Development and Control of a High Maneuverability Wheeled Robot with Variable-Structure Functionality

Common wheeled robots face many difficulties when traveling in complex environments, especially its incapability to climb over obstacles higher than its wheel radius. Many alterations were made to these robots to allow them to travel in rough terrains or conquer high obstacles, nevertheless, most designs are complex in nature and lost several original wheeled robot advantages by gaining others. In this paper, we propose a novel wheeled type robot with variable structure functionality. It is designed with simple structure consisting of three main robot parts, the main body, the left and right wheel-arm units. The robot could achieve five locomotion modes that allows the robot to travel in various environments and climb over high obstacles. Moreover, the fast-speed advantage in flat floor condition that common wheeled robot originally hold is still remained. The confirmation of the effectiveness of the robots maneuverability is shown by several experimental results

Development of omni-directional image stabilization system using camera posture information

A teleoperated robot which works in unstructured environments such as disaster sites is mainly controlled based on images obtained from cameras mounted on the robot. Since it runs on rough terrains, the images from the mounted camera are non-steady ones. These non-steady images will make the operator difficult to understand the surrounding information and will cause the camera motion sickness. We have developed the image stabilization system using camera posture information for a mobile robot that moves on uneven terrains. Since the camera posture information is detected by a 3D motion sensor separately from the camera image, this system works even in bad light condition environments and is robust for the light condition changes. The wide field of view images are obtained by the fish-eye lens camera in the previous implementation and these images are used to handle a large amplitude disturbance. The sphere mapping and the image shifting of a region of interest according to the detected camera attitudes are used for the motion compensation. We have extended our previous system to handle much larger amplitude vibration by using four fish-eye lens cameras. The omni-directional hemisphere world image can be obtained by the system and the rotation angle which can be compensated is 360 deg in yaw rotation.

Compact image stabilization system for small-sized humanoid

Wearable computing has been actively investigated as the dimensions of devices such as computers, sensors and motors are getting smaller. In this work our aim is to develop an image stabilization system for a small-sized humanoid robot as the first step for sharing of visual information between humans. A small-sized humanoid robot is used to simulate a person who captures visual information of a distant site. The developed image stabilization system can be used for an advanced wearable telepresence system. Requirements of an image stabilization system, which can be used as a wearable system, are compactness, lightness in weight, and real time process such as 30 frames/s. We have implemented our image stabilization system to satisfy these requirements. The developed system uses a 3D motion sensor for camera rotation detection, optical flow for camera translation detection and image process for motion compensation. The experimental results show that images from a small-sized humanoid robot can be stabilized by our developed system.

Development of Robot Teleoperation System in Bad Viewing Condition

In robot teleoperation there is a mounted camera on a robot and the operation is usually performed from a remote site using captured images by the mounted camera. Even though color cameras provide many useful information of a remote site, robot teleoperation using color cameras are highly effected by environmental conditions such as lighting, colors, smoke, etc. and there might be a case that cameras might become useless during an operation such as in dark places. In this paper we have developed a robot teleoperation system which does not fully rely on color camera images and works well in bad viewing condition for operating a robot and searching for a victim. A laser rangefinder is used for sensing surroundings of a robot and a thermal camera is used for victim detection. An operator can control a robot in a remote site only using environmental contour figure information around a robot without color camera images. The augmented image interface consists of color and thermal camera images are used for victim detection. We have executed a victim searching task in different lighting conditions with different sensor configurations to show the effectiveness of developed system.

Synthesized Scene Recollection for Robot Teleoperation

In this paper we propose an innovative robot remote control method, a synthesized scene recollection method, which provides the operator with a bird’seye view image of the robot in an environment which is generated by using position and orientation information of the robot, stored image history data captured by a camera mounted on the robot, and the model of the robot. This method helps the operator to easily recognize the situation of the robot even in unknown surroundings and enables the remote operation ability of a robot to be improved. This method is mainly based on two technologies, robot positioning and image synthesis. In this paper we use scan matching of laser rangefinder’s scan data for robot positioning and realized self-contained implementation of the proposed method in 2D horizontal plane.

Development of rescue robotic systems for both daily and emergency use

In order to improve our life further, it is our inspiration to develop efficient robotic systems that can assist our usual need. The system that we are developing not only bring forward efficiency and credibility for daily usage or research platform, but when natural catastrophes like earthquake happens to strike, our robotic system is also capable of entering post-disaster sites and collect information about victim states that will be transmitted to the human rescuers, so that a more accurate and efficient rescue mission can be carried out. This paper presents the up-to-date information about our robotic system development of two different types of robots, the snake-type and the wheel-type.