Akira Nishi

Design of a robot capable of moving on a vertical wall

The development of a mobile robot which can work on the vertical walls of tall buildings, the side walls of large ships, etc. has been expected for a long time. A magnetic force or vacuum pressure is available to sustain the robot on a vertical wall, and wheels, crawlers and some other walking mechanisms can be used as the methods of moving. Many combinations of these mechanisms will be developed for various applications. Two kinds of robot model were built and tested. The air was sucked from the peripheral nozzle of the suction cup to the fan and crawlers were used as the moving system. There are two dangerous situations-slipping and falling, and their limits are determined. It is important to decrease the shock of an impulsive load, such as a falling body colliding with the robot on the wall. In such a case, a guard with a shock absorber is useful for avoiding this danger, and its optimum design condition is derived. The aerodynamic matching between the fan and suction cup is also important to understan...

Active control of turbulence for an atmospheric boundary layer model in a wind tunnel

Abstract Many types of meteorological and boundary layer wind tunnels have been used for a long time to simulate the atmospheric effects on large structures and the transport of air pollutants. In addition, a few actively controlled wind tunnels have been proposed to obtain more realistic effects on structures. New types of multiple-fan wind tunnels have been developed in our laboratory. To produce the required wind turbulence in the tunnels, fans and oscillating airfoils were controlled independently by a computer. Statistical parameters, such as mean wind velocity, turbulence intensity, turbulence scale and power spectral density profiles in a boundary layer, were satisfactorily reproduced in the tunnel. In addition to these parameters, a Reynolds stress profile was achieved and corresponding coherent motions were observed in the boundary-layer flow.

Reproduction of wind velocity history in a multiple fan wind tunnel

Abstract An actively controlled wind tunnel for simulating the atmospheric boundary layer is described. The air flows are generated by 99 frequency-controlled fans arranged in a 9 wide by 11 high matrix. Various fluctuating flows can be reproduced in this wind tunnel by altering the input data of the fans through computer control. In this paper the method used to reproduce the wind velocity history is described. Some experiments are carried out to investigate the basic performance of the wind tunnel. The simulations of velocity histories of the intermittent turbulent flow and fully developed turbulent flow are also carried out.

Turbulence control in multiple-fan wind tunnels

Abstract Many types of meteorological, environmental and boundary layer wind tunnels have been constructed to simulate atmospheric phenomena on buildings and structures. New types of two- and three-dimensional wind tunnels have been constructed. These tunnels habe multiple-fans and oscillating blade rows to control the turbulence in the tunnels, and are controlled by computers. In this study a few turbulence parameter profiles were obtained in both longitudinal and vertical directions, and a trial to control the Reynolds stress was carried out.

An Actively Controlled Wind Tunnel And Its Application To The Reproduction Of The Atmospheric Boundary Layer

An actively controlled wind tunnel equipped with multiple fansand airfoils has been developed, mainly for the purpose of reproducing the atmospheric boundary layer (ABL) for wind engineering applications. Various fluctuating flows can be achieved in this wind tunnel by altering the input data of the fans and airfoils through computer control. In this study, the ABL is physically simulated in this wind tunnel, and particular attention ispaid to the simulation of the profile of Reynolds stress. The method of generating the fluctuating flow and the experimental results of reproducing the ABL are presented. As the results show, the spatial distribution of Reynolds stress is satisfactorily simulated, and the profiles of other statisticalturbulent parameters, such as mean velocity, turbulent intensity, integral scale and power spectrum are successfully reproduced simultaneously.

Robot actuation with low-pressure air-powered motors

Air-powered motors have the advantages of being lightweight and of low cost, as well as the characteristics of employing air power as the power source. These features make air-powered motors promising candidates to drive walking mechanisms, such as a wall-climbing mechanism. This paper describes the research carried out on the characteristics and control of a low-pressure pneumatic system to actuate a 3 d.o.f. robot, which is an intermediate model in our development of an air-powered wall-climbing robot. The motors used are low-pressure rotary-type air motors equipped with two valves to adjust the motor speed and its direction. The 3 d.o.f. model is used to perform tests of path control under different payloads. A personal computer, position sensors, and a set of valve adjusting devices are employed to control the robot. A control methodology based on the PID control algorithm and the rule of the time-optimal control algorithm is employed to control the robot. The experiments have been carried out and the...

Development of a Large-Scale Wind Tunnel of Multi-Fan Type (Characteristics of Turbulent Flow by a Uniformly-Active Method)

In an attempt to simulate both large scale and high-intensity turbulence within a limited entry length, an innovative wind tunnel of “multi-fan type” is developed. The airflow is driven by an array of fans (9 columns×11 rows), each of which is independently controlled by a computer. Details of the wind tunnel were introduced, and two typical methods (“uniformly-active” and “quasi-grid” methods) were applied to drive the wind tunnel. Comparison with the quasi-grid method revealed the spatial structure of the turbulent flow generated by the uniformly-active method.