This paper proposes a path planning system using fuzzy rules and a potential field. As an example, we took the problem of backing up a truck to a loading dock which Nguyen and Widrow originally used. We propose a new hybrid method of fuzzy control rules and a potential field for a vehicle navigation and control in the presence of obstacles. This technique has the following merits: (1) As long as we have the map information, we can control a truck to the goal point. (2) We can consider the operator's technique because of using fuzzy logic for a vehicle control. (3) The control method is very simple. The system can successfully back a truck up to the goal point by the following two ideas: (1) a potential field that peaks at the surface of obstacles and contains no spurious local minima. (2) use of simple fuzzy rules whose number is much less than those used by Kong and Kosko.
The authors started studying and developing a new capacitor used for a 1.5 MHz highly-stable LC tuning circuit in 1963. The high-stability of capacitor was severely required under the conditions that the signal voltage is from 1.4 to 9.2 V, the temperature is from -30 to 65°C and the period is for 20 years. The aging characteristics of the ceramic capacitors available 20 years ago were ΔC/C=±0.1%/year or so, but the requirements was ΔC/C=(-0.01±0.08)%/20 years. In addition, no design method to satisfy the requirements was established. Therefore, the authors developed a ceramic capacitor housed in a low-humidity metallic case using a paraelectric (MgTiO3) element, considering the stability of aging characteristics for 20 years. It could be assumed during the study that the aging characteristics would change almost linearly with the logarithm of time under the influence of humidity. So, the authors proposed the characteristics change for 20 years could be expected based on the data for 10 days of the specimen. To confirm that the proposal was correct, they measured the aging characteristics for 20 years, and found that the measurement value was within the specified value of ΔC/C which was (-0.01±0.08) %/20 years.
An autonomous robot must have a real-time path plan satisfying environmental changes and unknown situations. Obstacle avoidance is one of the problems in the path plan. With respect to studies concerning obstacle avoidance, a potential method based on vector analysis and a novel technique based on graph theory have been proposed. A sensory point moving method is a technique based on a parallel algorithm. This technique has involved a problem on the path planning in the working environment containing the blind alley obstacle. In this paper, we propose an improvement on renewal rule of a sensory point and path plan based on vector analysis. We developed a mobile robots system using a bird's-eye view. Through the path planning simulation and the application of this technique to a mobile robots system, the effectiveness of the present technique is confirmed.
A technique for forecasting daily peak load on a utility power system is presented. After embedding time series data of daily peak load into a reconstructed state space, a nonlinear mapping is constructed by a local approximation method based on the orthonormal Gram-Schmidt bases. This method utilizes only the past load data for short-term prediction of the daily peak load, while many conventional methods make prediction with various kinds of data such as temperature and weather. The quality of prediction by the proposed method is as good as those with other prediction methods. Moreover, the results of short-term prediction by this method are satisfactory even with data as small as 250 points.
This paper presents a trial of constituting a DC reference voltage circuit which has general purpose feasibilities. The circuit pursuing a high quality on both the exactness and the preciseness is composed of a zener diode parallely connected by a Lithium storage battery. The fundamental idea is to suppress the noise and fluctuation components inherently inevitable in the zener diode to as low a level as possible by using the battery as a capacitor having a large capacity, since the Lithium battery is of quite low noise. Then the key point is dependent on the exactness and the stability of the temperature control of the circuit. The circuit having the reference voltage 3.2[V] is produced by way of trial and the characteristics are as follows: (i) The temperature dependence is 1.43[μV/°C] (=0.45[ppm/°C]); (ii) The amplitude of the fluctuation frequency components lower than l[Hz] is less than ±0.75[μV] and (iii) The noise components over the frequency range from l[Hz] to 2[MHz] is less than 0.9[μV] (rms). The fluctuation level arrives at the order of -130[dB] and there can never be found a voltage reference device having such a quality regarding the pursuit of the general purpose utilities.
This paper proposes a new s-z transform method to obtain a digital system simulating an analog system. The method is based on preserving the waveform response of the analog system for the digital system, and employs triangular pulse whose Fourier spectrum attenuates with high rate. This choice brings the desirable property of reduced effect of aliasing in the frequency response and error of the impulse response. Several examples will be presented and describe that the new method is more useful than the conventional methods.
A new method of trajectory analysis is described for a type of tele-focussing electron gun similar to the one designed by K. H. Steigerwald. The Steigerwald gun has a point source of electrons and a Whenelt electrode which may create the crossover point downstream of the anode. The method is applied here to a gun with a similar electrode configuration, but with a source of finite size. It is assumed that the ions created by the electron beam at a downstream target will cause space charge neutralization, resulting in the cancellation of space charge forces at the crossover points. Analytic solutions are presented for the regions near the cathode and elsewhere, and applied to the configuration of the above-mentioned type of gun. Good agreement is found when the result is compared with the numerical calculation of Runge-Kutta method.
To design and implement controllers for autonomous mobile robots are well known as a complex task. In this paper, we propose an object-oriented design support system for developing autonomous mobile robots. The system consists of three kinds of testing stages; simulation test, ‘actual robot in virtual environment’ test and actual test. The testing stages gradually progress from simulated world to real world. The ‘actual robot in virtual environment’ test, at which an actual robot moves in a real environment without obstacles while being affected by simulated sensors, is significant to maintain the experiments safe. Each testing stage has three control modes; manual mode, playback mode and autonomous mode. In the autonomous mode, a robot can autonomously operate according to a robot control program. The program is available without modifying it for the whole testing stages. This enables us to implement the program rapidly. The proposed system is constructed from software components based on an object-oriented design. An interconnection mechanism between components and a task control mechanism for activating components allow us to design controllers efficiently. To show that the proposed system is useful, an action-based layered controller for navigating a robot is implemented.
More than two hundred of TCNQ complex salts were synthesized and salts having high melting point and moderate conductivity were selected, These TCNQ complex salts were melted and impregnated into micropores of etched aluminum foil covered with aluminum oxide dielectric layer. Aluminum solid electrolytic capacitors with these TCNQ complex salts showed improved thermal stability at soldering temperature, however high ESR (Equivalent Series Resistance) values. Low ESR was achieved by employing the mixture of two salts for solid electrolyte, and these capacitors have exellent frequency characteristics, thermal stability and reliability.
As for the free-wheeling diode (FWD) used for an inverter in power electronics, reduction of forward voltage (VF) and reduction of reverse recovery charge (Qrr) have been demanded for reduction of power loss. The soft reverse recovery characteristic which suppresses surge voltage even on the operating condition of high di/dt has also been demanded. In this paper, an analysis will be given about soft reverse recovery of the PIN diode structure paying attention to carrier distribution, distribution of impuritiy concentration and depletion layer, which has not been analyzed up to now. This result shows that the method of reducing the surface impurity concentration and the diffusion depth of the P-layer is effectual in soft reverse recovery. Moreover, it shows that the structure where impurity concentration of the transition part which is the boundary region of the I-layer (the N--layer) and the N+-layer goes up gradually from the I-layer to the N+-layer, is important to achieving soft reverse recovery. The 2 step gradient structure of impurity concentration of N-layer is proposed from this analysis result. This structure is the optimum one of PIN diode as FWD which can control Qrr maintaining soft reverse recovery.
This paper presents an analysis-based fuzzy retrieval method to detect the data with specified characteristics of changes by directly using the human's sensuous expression from the large-scale regional statistic data base. The sentence of “For a given period of time, list up the number of regions which have very large population and rapid population increase” is one example of fuzzy queries. For this purpose, fuzzy retrieval is carried out by classifying frequently using data retrieval patterns including the human's fuzzy language according to the characteristics of changes in the data. Both a fuzzy set and a fuzzy membersihp function to correspond to each data retrieval pattern are defined, and the special grammar of fuzzy retrieval condition is determined, Then, fuzzy set operations on fuzzy sets are applied. The fuzzy retrieval method is realized on SUN Workstation. Retrieval results prove that the method is practical applicable to real data. Furthermore, the method is applied Osaka University Regional Simulation model. The retrieval and analysis results concerning the cause of changes in the data could be displayed in separate graphical forms by use of the developed display system.