Yogo Takada

Position Estimation of Small Robotic Fish Based on Camera Information and Gyro Sensors

Robotic fish are ideal for surveying fish resources and performing underwater structural inspections. If a robot is sufficiently fishlike in appearance and does not use a screw propeller, real fish will not be easily surprised by it. However, it is comparatively difficult for such a robot to determine its own position in water. Radio signals, such as those used by GPS, cannot be easily received. Moreover, sound ranging is impractical because of the presence of rocks and waterweed in places where fish spend a lot of time. For practical applications such as photographing fish, a robotic fish needs to follow the target fish without losing awareness of its own position, in order to be able to swim autonomously. We have developed a robotic fish named FOCUS (FPGA Offline Control Underwater Searcher) which is equipped with two CMOS cameras and a field-programmable gate array (FPGA) circuit board for data processing. The forward-facing camera is used to track red objects, since this is the color of the fish of interest. In addition, using visual information obtained with the bottom-facing camera, the robot can estimate its present position. This is achieved by performing real-time digital image correlation using the FPGA. However, until now, the position estimation accuracy has been poor due to the influence of yaw and roll. In the present study, the position estimation method has been greatly improved by taking into account the yaw and roll values measured using gyro sensors.

Walking guide interface mechanism and navigation system for the visually impaired

We propose a new mechanism, with an intuitive interface, for a walking guidance system for the visually impaired. The user pushes the mechanism using a long handle like walking stick, and the mechanism steers to navigate along a given route using environmental sensors, communicating the steering angle to the user by twisting the handle. Using the interface, users are aware of their direction to go and can walk without hesitation. A navigation method incorporating simple topological map information is proposed for the mechanism, and a prototype system that follows the walls surrounding a route is developed. Experiments illustrate the usability and performance of the proposed interface and system.

In vivo visualization method by absolute blood flow velocity based on speckle and fringe pattern using two-beam multipoint laser Doppler velocimetry

Two-beam multipoint laser Doppler velocimetry (two-beam MLDV) is a non-invasive imaging technique able to provide an image of two-dimensional blood flow and has potential for observing cancer as previously demonstrated in a mouse model. In two-beam MLDV, the blood flow velocity can be estimated from red blood cells passing through a fringe pattern generated in the skin. The fringe pattern is created at the intersection of two beams in conventional LDV and two-beam MLDV. Being able to choose the depth position is an advantage of two-beam MLDV, and the position of a blood vessel can be identified in a three-dimensional space using this technique. Initially, we observed the fringe pattern in the skin, and the undeveloped or developed speckle pattern generated in a deeper position of the skin. The validity of the absolute velocity value detected by two-beam MLDV was verified while changing the number of layers of skin around a transparent flow channel. The absolute velocity value independent of direction was ...

Multi-channel laser Doppler velocimetry using a two-dimensional optical fiber array for obtaining instantaneous velocity distribution characteristics

A laser Doppler velocimeter (LDV) has been developed that is capable of performing two-dimensional (2D) cross-sectional measurements. It employs two horizontal laser light sheets that intersect at an angle of 13.3°. Since the intersection region is thin, it can be used to approximately determine the 2D flow field. An 8 × 8 array of optical fibers is used to simultaneously measure Doppler frequencies at 64 points. Experiments were conducted to assess the performance of the LDV, and it was found to be capable of obtaining spatial and temporal velocity information at multiple points in a flow field. The technique is fast, noninvasive, and accurate over long sampling periods. Furthermore, its applicability to an actual flow field was confirmed by measuring the temporal velocity distribution of a pulsatile flow in a rectangular flow channel with an obstruction. The proposed device is thus a useful, compact optical instrument for conducting simultaneous 2D cross-sectional multipoint measurements.

Performance of Very Small Robotic Fish Equipped with CMOS Camera

Underwater robots are often used to investigate marine animals. Ideally, such robots should be in the shape of fish so that they can easily go unnoticed by aquatic animals. In addition, lacking a screw propeller, a robotic fish would be less likely to become entangled in algae and other plants. However, although such robots have been developed, their swimming speed is significantly lower than that of real fish. Since to carry out a survey of actual fish a robotic fish would be required to follow them, it is necessary to improve the performance of the propulsion system. In the present study, a small robotic fish (SAPPA) was manufactured and its propulsive performance was evaluated. SAPPA was developed to swim in bodies of freshwater such as rivers, and was equipped with a small CMOS camera with a wide-angle lens in order to photograph live fish. The maximum swimming speed of the robot was determined to be 111 mm/s, and its turning radius was 125 mm. Its power consumption was as low as 1.82 W. During trials, SAPPA succeeded in recognizing a goldfish and capturing an image of it using its CMOS camera.

Development and evaluation of compact robot imitating a hermit crab for inspecting the outer surface of pipes

Terrestrial hermit crabs which are a type of hermit crabs live on land, whereas typical hermit crabs inhabit the sea. They have an ability of climbing a tree vertically. Their claws allow them to hang on the tree. In this study, an outer-pipe inspection robot was developed. Its locomotion mechanism was developed in imitation of the terrestrial hermit crabs claws. It is equipped with two rimless wheels. Each of the spokes is tipped with a neodymium magnet, which allows the robot to remain attached to even a vertical steel pipe. Moreover, the robot has a mechanism for adjusting the camber angle of the right and left wheels, allowing it to tightly grip pipes with different diameters. Experiments were conducted to check the performance of the robot using steel pipes with different diameters, placed horizontally, vertically, or obliquely. The robot attempted to move a certain distance along a pipe, and its success rate was measured. It was found that the robot could successfully travel along pipes with vertical orientations, although it sometimes fell from oblique or horizontal pipes. The most likely reason for this is identified and discussed. Certain results were obtained in laboratory. Further experiments in actual environment are required.

Evaluation of Artificial Caudal Fin for Fish Robot with Two Joints by Using Three-Dimensional Fluid-Structure Simulation

A fish robot with image sensors is useful to research for underwater creatures such as fish. However, the propulsion velocity of a fish robot is very slow compared with live fish. It is necessary to swim at a speed several times faster than the speed of the current robots for various usages. Therefore, we are searching for the method of making the robot swim fast. The simulation before making the robot is important. We have made the computational simulation program of three-dimensional fluid-structure analysis. The flow around the caudal fin can be examined by analyzing the fin as an elastic body. We compared the results of numerical analysis with the results of PIV measurement. Both were agreed well. Because the performance of a fish robot with two joints is better than that of a fish robot with one joint, we searched for an excellent fin for the fish robot with two joints by using CFD. We confirmed that the swimming performance of a fish robot becomes very good when the caudal fin is rigid except for the root of the fin which is comparatively flexible.

Development of Fish Robots Powered by Fuel Cells: Improvement of Swimming Ability by a Genetic Algorithm and Flow Analysis by Computational Fluid Dynamics

A fish robot with image sensors is useful to seek disaster victims in flood areas. In order to perform rescue operation for long time, the method of supplying electric power is important. The purpose of this study is to develop fish robots powered by polymer electrolyte fuel cells (PEFCs).

Walking Pattern Generation and Stabilization of Walking for Small Humanoid Robots

Declining birthrate and a growing proportion of elderly people are closed up as social issues in Japan. Especially, a growing proportion of elderly people is seen as an issue in nations of Europe and North America and so on as well as Japan. New labors engaging in the life support and the nursing for the elderly person will need in the future. To supplement the lack of the manpower, the research that applies the robot technology to the welfare field is important. Especially, because the shape of a humanoid robot looks like human, the person who receives nursing can be relieved. Besides, a humanoid robot can act under persons life environment, and can use the tool that the person uses. In addition, it is possible to avoid colliding with something put on the ground because the biped robot does not move with wheels. The biped robot can be used even in the environment including steps and ruggedness where robots with wheels cannot be used. In a word, the biped humanoid robot is extremely effective as the robot that acts in the environment where we live in daily life. However, it is necessary to prevent the robot from falling in the case of two-legged locomotion. Moreover, it is also necessary to keep controlling while the robot is only standing with stable posture. Various techniques about the walking of a humanoid robot have been devised up to now in recent years, and the walking pattern generation of a humanoid robot with complex dynamics has become possible. On the floor where information about the height of the small step was obtained beforehand, steady dynamic walking was achieved by using such as the technique of linear inverse pendulum model where the humanoid robot was expressed with an inverted pendulum of simple single-mass system, and truck model with preview control of ZMP trajectory (Kajita, 2005, 2009). However, in the case that the robot walks in a real environment, it is difficult to obtain the detailed information on the floor beforehand and give the information to the biped robot at any time. There are research examples (Kajita & Tani., 1996) of making the robot measure the shape of the road with sensors while walking. But, it is necessary to install the highly accurate sensor in the robot. The road where the robot walks is not only a smooth road. A small ruggedness and a gradual inclination are contained in many cases. However, it is impossible to record information of detailed shape on the ruggedness onto the robot beforehand. A biped robot KHR-2HV manufactured by Kondo Kagaku Co., Ltd. in Japan and HOAP-1 manufactured by Fujitsu Automation Ltd. in Japan were used in this study as humanoid robots. The basic walking experiment was conducted by using KHR-2HV. Then, another

Development of Numerical Method for Analyzing Gas-Liquid Two-Phase Flows in Consideration of Superior Mass Conservation

In order to run a numerical analysis of gas-liquid two-phase flows accurately, a three-dimensional computational code has been developed with a new numerical method in consideration of superior mass conservation. In this code, which is based on the GTT code developed by the authors, the interface between two phases is discriminated by an interface tracking function, and the function is reconstructed according to its iso-value surface at appropriate intervals during its convection process so that the interface can be captured sharply and the mass can be absolutely conserved. By using this code with the original numerical method, the behavior of two water droplets, which impinge mutually in various manners, has been numerically analyzed and the calculated result compared with an experimental result. The results show that this code can reproduce well the phenomenon of coalescence or breakup after the mutual impingement of the droplets.