Hunting Phenomena Research Articles

A Numerical Investigation into Wheel-Track Profile Optimization for Minimizing Stress and Mitigating Hunting Phenomena

A Numerical Investigation into Wheel-Track Profile Optimization for Minimizing Stress and Mitigating Hunting Phenomena

Numerical Vibration Displacement Solutions of Fractional Drawing Self‐Excited Vibration Model Based on Fractional Legendre Functions

In practice, due to the fact that the phenomenon of drawing self‐excited vibration can be deemed as one of the hunting phenomena of the mechanical system, this study focuses on investigating the drawing self‐excited vibration process through proposing the fractional differential equation model of hunting phenomenon of the mechanical system. The fractional Legendre functions together with their fractional differential operational matrices are used to numerically solve the model. In this way, the numerical solutions of vibration displacement of the model are obtained. At the end, the proposed model and algorithm are proved to be effective via analyzing the numerical results and phase position.

A Novel Technique Using Multiresolution Wavelet Packet Decomposition for Real Time Diagnosis of Hunting in Line Start IPM Motor Drives

A line-start interior permanent magnet (LSIPM) motor operates with inherent hunting phenomena. This paper presents a novel procedure for real-time diagnosis of hunting in LSIPM motors based on stator current signatures. Torsional vibration associated with hunting in a LSIPM motor influences the electrical supply, and introduces variable amplitude lower and upper sidebands in the stator current. In this paper, wavelet packet decomposition is applied to perform multiresolution analysis of the nonstationary current signals for detection and extraction of the sideband frequency components superimposed on the fundamental. Statistical techniques are applied on the extracted data signals and a signature for the diagnosis of hunting phenomenon is established. The proposed technique is validated by performing finite element analysis (FEA) of two three-phase four-pole LSIPM motors of different power ratings for various case scenarios. Experimental investigations have been carried out for a three-phase four-pole 208-V, 1-HP LSIPM motor drive in order to validate the performance of the proposed method under various operating conditions. Based on FEA and experimental results, the proposed technique can successfully diagnose the hunting phenomenon without a vibration sensor.

A REVIEW OF THE EFFECTS OF CHANGES IN THE VOID FRACTION OF THE SUPERHEATED REGION ON THE TEV OPERATION AND EVAPORATOR STABILITY

A level of superheat is necessary to ensure proper operation of vapor- compression refrigeration systems. An overly superheated vapor prior to entering the compressor can render the system inefficient, while inadequate superheat can result in evaporator instability and compressor damage. The void fraction present in the suction line is directly related to evaporator stability and the hunting phenomenon in the thermostatic expansion valve (TEV). This article aims at reviewing superheated region-related researches in the field of refrigeration as they relate to the operation of the TEV and the stability of the evaporator. In a first part, literature review will explain the causes of the void fraction in the superheated region and the second part describes the effects of the lubricant oil on the void fraction. The third part of this article is a review of the effects of the superheated region on the TEV and on evaporator stability, explaining the causes of the hunting phenomena and evaporator instability.

Grasping Force Control of Robot Hand Using Stepping Motors, Gears and Plate Springs (Feedforward Grasping Force Control in Case that Shape of Grasped Body is Known)

In this paper, a prototype robot hand consisting of permanent magnet type stepping motors, gears and plate springs is developed, and the grasping force performance of the robot hand is investigated theoretically and experimentally. The robot hand is attached to a single-joint robot arm driven with a hybrid type stepping motor and a ball screw. In the theoretical analysis, the equations of motion of the system are derived, and the numerical calculations have been carried out. Then, it is ascertained numerically that the feedforward grasping force control can be well executed. Furthermore, the experiments have been carried out, and the excellent performance of the feedforward grasping force control is confirmed experimentally. Moreover, it is ascertained theoretically and experimentally that the hunting phenomena of the stepping motors are generated, when the operation time of the feedforward grasping force control is shorter to some extent.

Instability of automotive air conditioning system with a variable displacement compressor. Part 1. Experimental investigation

A test system is built first in order to investigate the instability of the automotive air conditioning (AAC) system with a variable displacement compressor (VDC), and hunting phenomena caused by the large external disturbance in the AAC system with a VDC and a thermal expansion valve, and in the AAC system with a VDC and a fixed-area throttling device are investigated experimentally in part 1 of this paper. The experimental results indicate that there also exist the hunting phenomena in the AAC system with a fixed-area throttling device. The system stability is found to be dependent on the direction of the external disturbance, and the system is apt to cause hunting when the condensing pressure decreases excessively since it may cause two-phase state at the throttling device inlet and make a large disturbance to the system. The piston stroke length will oscillate only when the oscillation amplitudes of forces acting on the wobble plate are great enough, otherwise the piston stroke length will be kept invariable, and then the system instability rule is also suitable for the AAC system with a fixed displacement compressor. From the experimental results, it is concluded that the two-phase flow at the throttling device inlet or at the evaporator outlet is the necessary condition but not sufficient condition for system hunting. Finally, a new concept, conservative stable region, is proposed based on the experimental results and theoretical analysis.

Dynamic Routing System for Traffic Dispersion Using Global Traffic Information and Local Communication.

We propose a new way to disperse planning route of transportation using IVC (Inter Vehicle Communication) in this paper. VICS (Vehicle Information and Communication System) has been developed to solve the traffic jam which is one of the ITS (Intelligent Transportation Systems) technologies. The VlCS is able to provide real-time global information with drivers and navigation system which helps drivers to find the fastest route according to the current traffic conditions. However, it is afraid that spatial oscillation of traffic jam "hunting phenomena" will happen if most of cars follow given global information with time delay from VICS. 0n the other hand, IVC is a developing technology which enables cars to exchange various information with others by optical communication, millimeter electromagnetic waves and so on. We therefore propose the combination way to decrease traffic congestion using IVC and VICS. At first we show the hunting phenomena in numerical simulations and the relationship between hunting phenomena and VICS user ratio. We propose a way to disperse planning route by IVC, and then confirm effect of the proposed way in city traffic models in numerical simulations.

Dynamical Analysis and Suppression of Human Hunting in the Excavator Operation.

Construction vehicle is widely used in construction works. Especialy in town area, a small-sized construction vehicle is often used, since it is usable in narrow place and low cost. However, the small-sized construction vehicle has characteristic problem of human hunting, and it make difficult to opereat. This paper deals with Human Hunting phenomena(HHP), which is one of the coupled vibration phenomena between the vehicle and the operator on board, appearing at the operation of the small-sized excavator and degrades operativity. This phenomena is related not only to the vehicle dynamical characteristic but also to human-operator's dynamical characteristic. To analize this phenomenon, it is necessary to consider the vehicle-operator dynamic model. We derived a mathematical model, which has six degrees of freedom to analyze this phenonmenon. Up and down motion of the excavator-boom is simurated. And it agrees with the phenomenon well. The linearized mathematical model shows that some control lever parameters are related to stability criterion. By simulation, it is confirmed that the proper selected control parameters can suppress the HHP.

High Performance Servo-System by Rotational Machines. A Proposition of Overlap Speed Detection Method and Improvement of Characteristics of Speed Observer.

In a speed control system used a low resolution rotary encoder, the unstable phenomena is caused by the long pulse period in extremely low speed region. Currently, a speed estimation method utilizing the disturbance observer is applied to suppress it. But this method required highly precise speed detection. So, in order to improve the speed detection characteristics, the speed measurement circuit is increased to four circuits, which number is same as the pulse edge types. And the measurement periods are overlapped each others.Furthermore, the fluctuation of a static friction at zero speed region cannot be estimated. So there is a problem of the speed hunting phenomena. Therefore, by applying the upper limit information in place of speed detection and continually operating the observer, the torque and speed estimation are corrected more accurately.It was confirmed through experiments that by applying the above mentioned technology, it is possible to obtain a stable and high speed response characteristic from zero speed to high speed regions.

Hunting phenomena of the balloon motions observed over Antarctica

It was reported that the strong hunting motions of the balloons were observed just after reaching the ceiling altitude for the balloons launched at Antarctica in the daytime. Such hunting motions are observed at middle latitude only for the nighttime launching. In this article, the thermal analysis of the balloon motions is performed by considering the atmospheric temperature and the environmental radiation conditions at the balloon altitudes. We found that the hunting phenomena over summer Antarctica are caused by the fact that the balloons over Antarctica encounter similar thermal conditions of flights at night over the midlatitude.

Experimental study on hunting phenomena in synchronous generators

AbstractNumerous studies have been made on the hunting phenomena of synchronous machines. However. most of them have been concerned with the mathematical analysis based on equivalent‐circuit models of machine and system, and experimental studies are quite rare. However, few papers have treated the phenomena from the viewpoint of internal air‐gap fluxes which actually govern the machine behaviors.This paper describes the experimental results on hunting phenomena of synchronous generators caused by a fast‐acting AVR (Automatic Voltage Regulator) in a laboratory‐model one‐machine/infinite‐bus power system. Changes of air‐gap fluxes in the process of hunting phenomena are measured by a search coil wound around a stator tooth on top of the tested synchronous generator and are examined. The interaction is made clear between field fluxes and quadrature‐axis fluxes both of which directly influence the hunting phenomena. The results obtained are confirmed by simulation studies. Thus, the relationship between system stability and machine fluxes is given a clearer understanding than before.

同期機の乱調現象に関する考察

同期機の乱調現象に関する考察

AN ANALYSIS OF RUNNING STABILITY OF HIGH SPEED RAILWAY TRUCKS CONNECTED IN SERIES WITH ELASTIC AND FRICTIONAL FORCES WORKING AGAINST TRUCK TURNING

SUMMARY The author theoretically analyzed the hunting stability of a bogie truck hunting which is a six degrees of freedom system having small clearances in the connecting positions between the truck frame and the bolster anchors where spring and friction are connected in series against truck turning. The study revealed that the limit cycle wad affected by various factors such that as the clearances at the connecting positions between the truck frame and the bolster anchors, the stiffness of the bolster, the frictional forces of the side bearers, the lateral stiffness of the rail, the non-linear creep force, etc. From the results, the hunting phenomena in the actual experiment could be well explained theoretically. Thus, in this basic investigation truck hunting which has been an unsolved phenomenon is now clarified and its preventing method has been established.

Development of a simulator for the fuel injection system of a diesel engine.

The governor of a diesel engine often induces self-oscillations called "hunting", associated with the fuel injection system of the engine. It would be very troublesome, however, to investigate the hunting phenomena using real engines. In the present study, a fuel system simulator has been developed to vary the parameters with ease. By replacing the engine with an analog computer and a hydrostatic transmission system, the characteristics of the engine could be varied easily. The frequency characteristics of this simulator agreed very well to those of the real engine below 1 Hz. Using this simulator, the authors investigated the effects of some parameters on the hunting phenomena below 1000 rpm, where irregular injections often occurred, and to which the conventional linear stability theory could not be applied.

An analysis of running stability for high speed railway vehicles connected in series with elastic and frictional forces against truck turning. (3rd report Stability criteria for vehicle hunting)

In this paper, we analysed theoretically the hunting stability of a high speed railway vehicle which has at least seven degrees of freedom with respect to lateral motion when elastic and frictional forces are connected in series against truck turning. According to the theoretical results, it was found that the stability criteria of the hunting, so-called, lower-center rolling, upper-center rolling and yawing of a car body, and the front and rear trucks depended on the lower hunting velocity was an unstable limit cycle, while the upper limit cycle changed into either a stable limit cycle or an unstable one corresponding to the magnitude of the angular amplitude. As the amplitude increased, the unstable region between the lower and upper limit cycles increased larger. Further, as the angular amplitude increased, the truck hunting phenomena of a bogie car connected with the damping of a suspension device between the car body and the trucks, the magnitude of the angular amplitude between the front and rear trucks, phase angle and others are made clear.

A method of computing the hunting phenomena of synchronous machines

A method of computing the hunting phenomena of synchronous machines