Low-speed Characteristics Research Articles

1732 対称形ケーシングの形状変化がクロスフロー風車の性能に及ぼす影響について(S34-4 自然流体エネルギーの利用技術(4),S34 自然流体エネルギーの利用技術)

The cross-flow wind turbine has high torque and low speed characteristics and the structure are very simple. However, even if the power coefficient is high, it is about 10%. In this research, in order to improve the performance of a cross-flow turbine, we installed the symmetrical casing that has nozzle and diffuser. Since casing has a nozzle in the symmetrical direction, wind turbine can use the wind that comes opposite direction by installing this casing. Mechanisms, which improve the performance of cross-flow wind turbine, were clarified by an experiment. Furthermore, the details of an internal flow of symmetrical casing were investigated by an experiment and CFD.

Dynamic modeling and control of a conveyance microrobotic system using active friction drive

Presents a new generation of compliant multidegree of freedom piezoelectric microconveyer for microobjects based on the cooperation of arrayed direct-drive micro standing-wave ultrasonic actuators (microSWUMs). Their operating driving principles based on active frictional contact forces offer direct-drive and low-speed characteristics at the microscale. The tradeoff, however, is the complexity of dynamic modeling and control to cope with the optimization of the intermittent friction drive mechanism. A method using an equivalent electromechanical circuit is proposed for estimating and analyzing the optimum driving force, including the dynamic electrical and the mechanical energy conversions. On the basis of the proposed method, the friction drive optimization of the microrobot is performed through the implementation of different controllers: 1) an electromagnetic-field-based preload controller ensuring optimal preload; 2) an open-loop piecewise-modulated controller for self locking and driving force control; and 3) a resonant frequency compensation. Finally, an experimental investigation has been performed on a prototype of ultrasonic microconveyer incorporating 48 arrayed microSWUMs whose overall dimensions are 47 /spl times/ 29 mm/sup 2/ in order to demonstrate the proposed optimized friction drive.

High torque ultrasonic motors for hand prosthetics: Current status and trends

This paper presents the work carried out at the Instituto de Automática Industrial, in the framework of the EU MANUS project and with the co-operation of the Katholieke Universiteit of Leuven, to develop a specifically designed TWUM for driving our prototype of hand prosthesis. The application of TWUM to prosthetic devices has clear advanteges, namely, noiseless operation, self-braking drive, high torque and low speed characteristics. Here we analyse main actuation advantages, point out main drawbacks of this technology and describe our research in the area of specific design of TWUM for high torque actuation, improved control characteristics and enhanced overall performance. We intend to provide a concurrent approach to the overall actuator design involving electronics, mechanical design as well as improved control strategies having in mind the prosthetic application.

Servo Speed Control of Traveling-Wave Ultrasonic Motors Using Pulse Width Modulation

W ith the advantages of lightweight, compact size, fast response, power-off holding torque and high-torque low-speed characteristics, the traveling-wave ultrasonic motor (TUSM) is becoming attractive for servo application. This paper presents a new pulse width modulation (PW M) method for servo speed control of a TUSM. The key is to digitally control the pulse width, hence the fundamental value, of the bipolar 2-phase voltages feeding into the TUSM. This method takes a definite advantage of minimum audible noise compared with those available methods, such as phase-difference control, frequency control, and on-off PW M control. Experimental results confirm that the proposed speed controller can offer good steady-state and transient performances and can significantly suppress the audible noise occurred at speed variations.

Stochastic neural computation. I. Computational elements

This paper examines a number of stochastic computational elements employed in artificial neural networks, several of which are introduced for the first time, together with an analysis of their operation. We briefly include multiplication, squaring, addition, subtraction, and division circuits in both unipolar and bipolar formats, the principles of which are well-known, at least for unipolar signals. We have introduced several modifications to improve the speed of the division operation. The primary contribution of this paper, however, is in introducing several state machine-based computational elements for performing sigmoid nonlinearity mappings, linear gain, and exponentiation functions. We also describe an efficient method for the generation of, and conversion between, stochastic and deterministic binary signals. The validity of the present approach is demonstrated in a companion paper through a sample application, the recognition of noisy optical characters using soft competitive learning. Network generalization capabilities of the stochastic network maintain a squared error within 10 percent of that of a floating-point implementation for a wide range of noise levels. While the accuracy of stochastic computation may not compare favorably with more conventional binary radix-based computation, the low circuit area, power, and speed characteristics may, in certain situations, make them attractive for VLSI implementation of artificial neural networks.

Process Integration of Embedded FeRAMs

This paper describes the general aspects of embedding Ferroelectric Memories (FeRAMs) with logic circuits and/or microcontrollers. These devices and stand-alone memories constitute the main thrust of applications of ferroelectric memories. The problems associated with embedding test the robustness and compatibility of the FeRAM process with established CMOS integrated circuits. As integrated circuits technology advances in lithography, FeRAMs meet the challenge, but new problems appear. In this review, existing embedded FeRAMs of the 0.8/0.6 μ generation will be discussed. A program for the 0.35/0.25 μ generation, and the 0.18 μ challenges are outlined and addressed. The paper also reviews the application of FeRAM Smart Cards. This application is becoming the best example of embedded FeRAMs in which to demonstrate the “System-One-Chip” technology direction. Smart Card ICs clearly take advantage of the low power, high-write speed and long endurance characteristics of Ferroelectric Memories.

An Approach for Low Speed Pneumatic Actuators

This paper presents an attempt for improving low speed characteristics of pneumatic actuators. When operated at low speed, the pneumatic actuators tend to have a jump start and a stick-slip responses. In particular after a long time rest, the response usually has a distinct jump start, which sometimes is not tolerable. To solve these problems, this paper conducts a theoretical analysis on the pneumatic speed control circuit and based on the analysis a new pneumatic circuit is proposed. The proposed circuit is a Meter-In control circuit with two pressure control valves added to keep the exhaust pressure at a high lever. The experimental results show that the proposed circuit is feasible for low speed pneumatic actuators.

Performance of ultrasonic mini-motors using design of experiments

This paper describes speed-torque characteristics of a parametrized set of 8 mm diameter tall ultrasonic motors fabricated using design of experiments. Design of experiments methods provide for a way of developing a model based on the gathering of data and a way of analysing the data to compute both quantitative and qualitative results which can point towards an optimal set of parameters for the final design. Ultrasonic motors are known for their high-torque, low-speed characteristics. These devices have demonstrated maximum no-load speeds of 1710 rpm and peak power outputs of 27 mW. Stall torques of these 8 mm motors have been measured as high as , yielding roughly 50 times the stall torque density of the smallest commercially available DC motors. Results of the study yield insight into optimizing stall torques and no-load speeds of miniature ultrasonic motors.

Large area InAlAs/InGaAs metal semiconductor metal photodiode with very low dark current and its frequency response

An MBE grown InGaAs metal semiconductor metal (MSM) photodiode (PD) with an InAlAs barrier enhancement layer is reported that has very low dark current and high speed characteristics. The detector using Cr/Au Schottky metal fingers with 4m spacing on a large active area of 300×300m2 shows a low dark current of 38nA at 10V. This corresponds to a dark current density of 0.42pA/m2 and is, to our knowledge, the best dark current ever obtained from a large area InGaAs MSM PD. The device also shows a low capacitance of 0.8pF and a high 3dB bandwidth of 2.4GHz. By fitting the measured frequency response to a model consisting of both RC time and transit time limited responses, we show that the device has an RC time and a transit time limited 3dB bandwidth of 3.0 and 4.9GHz, respectively.

Low-speed characteristics for the wing-canard configuration of the International Vortex Flow Experiment

Comprehensive aerodynamic investigations have been carried out on the coplanar wing-canard configuration of the International Vortex Flow Experiment (VFE) in symmetrical flow at low speed. Results of three-component balance, surface-pressure, and flowfield measurements are presented for the canard-off and the canard-on configuration. The vortex systems of canard and wing remain separate from each other. The main interference effects take place over the wing. The formation of the wing vortices is delayed to positions downstream of the apex. The canard vortices pass the wing leading edge relatively high, and after the onset of the wing vortices they are moved inward and downward over the wing. The trailing vortex sheet of the canard merges with the upper surface boundary layer in the inner portion of the wing. Considerably reduced vorticity is shed from the side-edges of the wing. This leads to a characteristic deformation of the vortex sheet in this region on the canardoff configuration, and to the formation of a side-edge vortex on the canard-on configuration. These results represent the limiting case M =^> 0 within the VFE.

ディザによる油圧サーボモータの低速特性の改善

Electro-hydraulic servosystems are utilized in various industrial fields, not to speak of control of machine tools. In the electro-hydraulic servosystems, hydraulic motors are used as actuators. There exists solid friction in the sliding parts inside the hydraulic motors. This solid friction results in sticky rotation of the hydraulic motors in very low speed region, in other words, the hydraulic motors cannot rotate smoothly in that region. Needless to say, this sticky rotation of the motors is undesirable from the viewpoint of control. The purpose of this research is to rotate a hydraulic servomotor, which consists of a spool valve and an axial piston motor, as slow as possible by applying dither on the shaft of the axial piston motor. In related fields, there are a few published papers on the dither and on stick-slip motion. The fomer ones discuss on the dither for removing dead zone caused by static (solid) friction. in other words, they discuss about the dither effect on removing the solid friction only when mean velocity of the motor is zero. The latter ones are related to the analyses of the stick-slip motion, but they don't show the way to remove the stick-slip motion of the motors by the dither. In the first part of this paper, necessary velocity amplitude and frequency of the dither ta remove equivalently the solid friction at the various mean velocity of the motor are investigated theoretically. On the other hand, it is generally impossible to generate the dither whose amplitude and frequency are arbitrary. So, in the second part of the paper, conditions which are necessary to enable generation of the dither are discussed theoretically. In the final part of the paper, experimental results of the low speed characteristics of a hydraulic servomotor are shown. In this experiment, the servomotor was rotated with appropriate dither obtained from the above mentioned theoretical results, and it was clarified that minimum velocity of the servomotor was much lower than the one without the dither.

Progress of the Rigid Rotor Concept

All of us know the history of the helicopter, but certain facets of this history need to be repeated in the framework of the development of the rigid rotor helicopter. It was in 1919, I believe, that Juan de la Cierva, shocked from the death of his brother in a spin accident, reasoned that the best way to build an aeroplane was to build one that made use of the spin as a fundamental. He put a bearing between the spinning wings and the fuselage so that the wings could spin without spinning the fuselage. This was a great advance in the state of the art and created an aeroplane with some rather good low-speed characteristics.