Recently, we proposed a method to obtain geometrical features of objects by using linear frequency modulated (LFM) ultrasonic pulses. In this paper, we give the theoretical basis of this method to apply it to the identification of complex shaped objects. Assuming that the wavelength of ultrasonic waves are much shorter than sizes of objects, we derive a mathematical model of the object reflectance for ultrasonic waves. It states that the observed signal is the sum of echoes from relatively small number of certain particular points (stationary points), even if the object has a complex shape. Then we consider what is the optimum waveform that can separate those echoes from the amplitude of the observed signal. As the result, we show that the amplitude modulated (AM) pulse and the LFM pulse can separate them in time domain and frequency domain, respectively. Although AM pulse is commonly used for measuring distance, it needs a high-temporal resolution sensing and signal processing which can deal with the carrier frequency of the pulse. In the case of LFM pulse, however, the required temporal resolution is of only the modulation frequency although the absolute distances of the points are lost. We point out that the relative distances between those stationary points are in most appications enough to discriminate the geometry of objects. We carried out several simulations for LFM pulse. The results along with the experimental results shown previously agreed fairly well with the proposed theory.

View full abstract

In this paper we presented a method of high precision load measurement by dynamic crane scale. The basic point of this approach lies in the idea that the sampling average of dynamic load signal during a time interval between the maximum swing angles is a function of the maximum swing angle. The mass of goods is a constant factor of this function. By the function and the maximum swing angle calculation formula, the mass value of goods can be calculated under the dynamic condition. The experimental results indicated that the measurement precision of more than 0.1% F.S. can be achieved.

View full abstract

Electric contact erosion and transfer at electrodes of electric contact greatly affects on degradation of the performance of contact. In this paper, the authors discuss on visualization of change in surface profile of electrodes by means of digital image processing. The change of surface profile in measurement data is buried under errors caused by diffusion and reflection of light. When the data is processed by ordinary smoothing filter, small component of feature in surface profile is lost, and processing of image enhancement magnifies error components. The authors have proposed a new image processing technique for measurement of surface profile of electric contact to keep detail features and eliminate errors in measurement data. Missing measurement data are interpolated, and errors in measurement data are eliminated keeping profile of edge by using nonlinear equalizing filter. Inaddition, the proposed technique discriminates feature and errors by dynamic filter which coefficients depend on neighboring components. From the result, visualization of change in surface profile is realized by the proposed technique.

View full abstract

Infrared radiation thermometers measuring low temperature have an inherent problem of background radiation originated in themselves because inner parts of radiation thermometers radiate as bright as measurement objects. The problem is important to multielement radiation thermometers.
To investigate background radiation of a multielement detector, angular dependence of responsivity of a 10-element InSb linear array was measured. The detector elements responded to radiation incidence from the outside of the field of view. Radiation from the outside of the field of view is mainly background radiation in an actual radiation thermometer.
We developed a new optical method to reduce background radiation incidencee of thermal infrared detectors with cooling. A mirror iris was used in the method; it was a concave mirror having an aperture for signal radiation at the center. When the mirror iris is inserted into an optical pass between the detector and a lens, the detector observes the cold image reflected in the mirror surface.
A thermal infrared radiation thermometer having the InSb array detector and the mirror iris was developed to evaluate the effect of the optical method. Zero drift of the radiation thermometer was largely reduced by the mirror iris without an optical chopper.
Stability of the radiation thermometer observing a blackbody furnace maintained at 40°C was measured. The indicated temperature drift was less than ±0.9°C when the room temperature was varied in a range of ±6°C alternatively. The drift was improved to less than ±0.2°C with a compensation using the inner temperature of the radiation thermometer.

View full abstract

This paper is concerned with the measurement method for surface roughness by optical pattern projection. This method can be classified into two fundamental configurations. The one has one imaging system including the sample surface placed on the way of the optical pathes, which the author calls “OTF method”. The other has two step imaging systems. The first system projects the input image on the sample surface, and the second forms the output image from the reflected image on the sample surface. The author calls the second method “Re-imaging method”. The author examined the contrasts of the output images by the OTF method experimentally, and found the correlation between the contrast data and calculated results of specular component e^-g expected from the scattering theory. The OTF method is restricted the range of measurement for the roughness Ra below about 0.1μm. The possibility for larger range measurement by the Re-imaging method is examined experimentally in this paper.

View full abstract

A new method for diffused gases detection and location in an open space using laser ultrasonic technique is proposed. When a laser pulse which is tuned to an absorption line of a gas molecule is irradiated to a localized concentration of the gas, an acoustic pulse is generated. As to a photo-acoustic effect in an open space, it is newly found that the signal has a frequency of about 40kHz and a propagation directivity which is perpendicular to the laser axis. In the feasibility test, methane gas molecules are excited by an optical parametric oscillator (OPO) type laser source which has a wavelength of 1330nm and an output power of about 5mJ per pulse. Array microphones and 2-dimensional laser scanning system are used for detecting the gas distribution. A 3-dimensional visualization result applying to methane gas leakage is presented.

View full abstract

The triple point of equilibrium hydrogen is realized calorimetrically using a closed cycle refrigerator (Gifford-McMahon type refrigerator) instead of conventional liquid helium baths. The usage of the closed cycle refrigerator with closed fixed-point cells is found not only to be the easiest and the simplest way in handling and in operation, but to be one of the most accurate realizing methods of the low temperature fixed points. The standard uncertainty in calibrating standard platinum resistance thermometers at the triple point of equilibrium hydrogen is estimated to be 0.07mK, which is better than the average values of the conventional realization. By the high reproducibility of the calorimetric measurement is observed an abnormality in the heat capacity of solid hydrogen at temperatures just below the triple point when the catalyst of ferric hydroxide is used for the ortho-para conversion of hydrogen molecular modifications, but no abnormality is observed in the case of a cell without catalyst.

View full abstract

The push-up motion is one of the essential activities for patients with spinal cord injury (SCI). The push-up motion is the raising of bodies up from the sitting position on the bed, the floor or the wheelchair. Physical therapists should train the patients to improve 3 factors, that is the skill, the power and the maintenance of the power. We made push-up motion measurement system that measure three dimensional floor reaction forces of hands during push-ups, and measured this activity according to this system in 27 SCI subjects. We calculated the torque of shoulder joints to evaluate the power of push-ups, and analyzed the force data to evaluate the skill of push-ups in order to apply to rehabilitation medicine. From careful observation, we recognize 2 manners of the push-up motion in SCI. These are the passive manner and the active one. The hip joints of some SCI subjects move backwards and they elevate their hips as highly as possible. We call this manner the active manner. As the results of this study, the following conclusions were obtained. (1) The torque of the shoulder joints is a very important power factor of the push-up motion. We calculated this value by using very simple mechanical model. The shoulder torque is high in the subjects whose push-ups show the active manner. This torque can be a parameter to evaluate the power of push-ups. (2) We compare and analyze three dimensional floor reaction among each subject. Then we found that the pattern of anteroposterior force Fx was quite different among the subjects. The patterns of Fx could be classified into 4 types. The Fx distinguishes one of these types (Type C) when the subjects performed push-up in the active manner. The Fx pattern can be a parameter to evaluate the skill of push-ups.

View full abstract

In pipe systems for water, gas and electric power transports and also for communication lines, it is greatly important to detect abnormalities in the pipes as accurately and promptly as possible, from the viewpoint of realizing a rapid restoration of the life lines. The paper proposes a method which measures the location, thickness and cross-sectional area of the abnormal objects in pipes based on the reflected wave. When transmitting a sonic wave into the pipes, many reflections are usually generated from not only the abnormal objects but also the pipe ends and the branch points in the pipes. To make the problem much worse, they are strongly superposed to each other. The paper thus proposes to apply a separation technique based on the reflected wave model and enables the measurement of the location, thickness and cross-sectional area of the abnormal objects, despite an exact information on the shape and length of the pipe system.

View full abstract

A gain design method of a stochastic fuzzy controller is described by using a linear min-max control law in discrete-time. It is shown that the stochastic fuzzy control system using such a design method can assure an asymptotic stability to within some tolerance, instead of assuring an ideally asymptotic stability about zero, as along as satisfying the so-called matching condition for the uncertainties. The effectiveness of the proposed method is illustrated by giving some simulations for the trajectory tracking control problem of a mobile robot with two independent driving wheels, in which the mobile robot is assumed to have completely unknown parameters.

View full abstract

This paper presents conditions for a linear uncertain descriptor system to be robustly stabilizable via linear feedback control. It is assumed that the system has a fixed number of exponential modes, but no impulsive mode. Applying the quadratic stabilization approach to tractable equivalent systems, robust stabilizability conditions for a system with polytopic uncertainties are obtained in terms of linear and bilinear matrix inequalities. An algorithm based on the idea of the homotopy method is proposed to solve the bilinear matrix inequality.

View full abstract

For a nonlinear/linear system the disturbance to which is restricted to a finite domain, the reachable domain in the state space from a given initial state is called a state reachable set. Though some theoretical approaches have been proposed on investigating state reachable sets, it is difficult to evaluate the state reachable set actually for general nonlinear systems by using these approaches directly.
In this paper, we introduce a quadratic system based on a quadratic approximation for nonlinear systems. Then we propose an approach based on linear matrix inequalities to investigate the reachable set of the quadratic system the disturbance to which is restricted to inside of a unit disc. In numerical case study, we demonstrate efficacy of the proposed approach by evaluating the state reachable set actually for a given quadratic system.

View full abstract

We have shown the design of nonlinear regulator which is globally stable using power state vector and genetic algorithm. In this paper we show the design of direct control of stabilization for nonlinear systems using power state feedback. This design method is to select constant feedback matrix using genetic algorithm so as to have a Lyapunov function of a closed loop applying power state feedback. This method is analogy to stabilizing feedback of linear system. In nonlinear system there is no concept of pole of linear system, though stabilization of nonlinear system is natural extension of stabilization of linear system in case of using Lyapunov function. This method can design strictly nonlinear feedback control law of bounded power degree to stabilize globally nonlinear system of odd degree polynomial.

View full abstract

The controllability with positive input constraints is very important and interesting in dealing with many practical control applications such as a pendulum system, economic system, etc. Although the necessary and sufficient condition for the controllability of discrete-time linear systems with positive controls is given earlier, it is not easy to determine whether a given multiple input system is positive controllable or not based on the former result.
This paper presents simple criteria for multiple input discrete-time linear systems to become positive controllable based on the Jordan canonical form and elimination method of Gauss. It is pointed out that the number of steps necessary to discriminate the positive controllability is finite. The results presented here clarify the structure of positive controllable systems and are useful in discussing fundamental control problems.

View full abstract

When the sampled-data control systems are used, undesirable oscillations between the sampling instance are occasionally observed. Such phenomenon is called ripple. Some studies deal with this problem, and derive the conditions to achieve the ripple-free responses.
In this note, we consider the ripple-free tracking problem for sampled-data systems. A proof for the necessary and sufficient conditions to achieve the ripple-free tracking is given. This result also shows the necessity of the continuous-time internal model for the possibility of the ripple-free responses. The feature of our proof is that we use a new concept “convergence to the C^∞ class.” We consider this concept makes discussion easier in this note.

View full abstract

This paper describes a new simple vehicle model derived by an object-oriented technique to analyze and design the vehicle control systems. The model describes four wheeled vehicle dynamics by a set of non-linear differential equations derived by the Newton-Euler method. In order to describe the simple but accurate vehicle dynamics, we developed 16 degree of freedom model which is consist of 3 rotational and transitional dynamics around the vehicle center of mass, 4 wheel rotation, suspension deflection and x-y rotation of front wheels which are due to the change of steering angle. Even the model is simple, it is enough accurate to be used to design vehicle controller. In the object-oriented approach, a well-known commercially available software is used for the verification of vehicle model. An example of straightforward analysis and design of vehicle dynamic system is shown. The model and the approach tasted by simulation shows the capability of real-time simulation.

View full abstract

Many pneumatic cylinders are utilized for automation and usually driven by a meter-out circuit, because the cylinder velocity can be determined by adjusting the effective area of the exhaust restriction and the motion time is the same even if the load force is changed. That is, speed control is realized by using only a restriction. This characteristic is verified by numerical analysis of cylinder physical equations. However, the principle of speed control has been unknown despite of the basis on cylinder selection. Although, one of the researchers explained constant motion time by feedback qualitatively, feedback mechanism is not explained till now.
The purpose of this study is to clarify the speed control mechanism through the block diagram and the transfer function of the cylinder system, which are determined from linearizing fundamental equations. As a result, the following are found: 1) The air compressibility makes the feedback loop. The terminal velocity is unique since the transfer function from the load force to the cylinder velocity is one type. 2) Changing the load force, each change of air mass swept by the piston and exhausting flow rate is just canceled. This is the cause for minus one type transfer function. 3) The relation between initial (when motion starts) and equilibrium condition is fixed for any load force change. Therefore, not only terminal velocity but transient response is the same and moving time is unchanged. By this study, the principle of speed control is proved theoretically.

View full abstract

This paper is concerned in a PI controller with adaptive parameter tuning. The PI parameters are adjusted automatically by using a high-gain adaptive control strategy. It is shown that the closed system is stable and the output error goes to zero when the proposed PI controller is applied to minimum phase plants with relative degree one. We also present a compensation method for plants with relative degree more than two so that the proposed controller will be applicable. Finally, some simulation results are given to illustrate the performance of the proposed controller.

View full abstract

With the development of modern control theories, various novel control methods have been proposed on torsional vibration system recently.
To solve the problem of torsional vibration and gear backlash, this paper proposes a simple control method of vibration suppression for drive system with gear backlash.
The proposed controller consists of a PI controller and PD feedback compensation of the gear torque estimated by a disturbance observer. Although the control design approach is easy to apply, the performance of the proposed method is better than conventional PID controller, and the effectiveness is shown by both simulations and experiments.

View full abstract

While torque converters in automatic transmission systems provide benefits such as good riding quality, they also decrease transmission efficiency of engine torque. To improve the efficiency, most automatic-transmission systems are equipped with a lock-up clutch, which directly combines the engine and the driving shaft. In a low-speed range, however, the lock-up clutch must be slipped at a rate by controlling the hydraulic pressure on the clutch; otherwise low-frequency noises and vibrations are generated. This paper first proposes a first-order model of the dynamics from hydraulic pressure command to the slip rate. The model is obtained from the experimental result that the dynamics from the converter torque to the slip rate is described by a first-order state equation whose parameters depend on turbine revolution rate only. Using the linear-parameter-varying model, a two-degree-of-freedom-control system is designed. The feedforward controller is given as a desired model that is gain-scheduled as a function of the turbine revolution rate. Next, the feedback controller is designed by a robust control method, i.e., μ-synthesis, which makes the closed-loop system robust against uncertainties such as variation of operating condition and aging. The effectiveness of the model and the controllers is demonstrated through driving tests.

View full abstract

A new design scheme of Multi-Controller Systems (MCSs) is proposed based on YJBK-Parametrization of all stabilizing controllers. In the MCS of this scheme, multiple control modes tuned for various specifications are selected by directly switching YJBK-Paremeters which are stable, proper and open-loop LTI elements. Thereby the MCS is completely parallel, in the sense that all the controllers are always connected to the input and on stand-by. Also proposed is a method to reduce the transient response after each switching, by using coprime factorization of the controlled object determined by virtual optimal state feedback law. Finally, as an example, application of the proposed scheme to an active-cab-suspension system is examined and the validity of the scheme is verified through simulations.

View full abstract

This paper deals with an approximate solution method by decomposing a search space dynamically combined with genetic algorithm(GA) and Lagrangian relaxation(LR) method for solving a job-shop scheduling problem. In this method a subspace of a search space is constructed by using information on partial processing order relations between operations which use same resources. We search these subspaces by using GA. We evaluate each subspace with lower bound obtained by using LR method and with minimum value of the set up cost obtained by the structure of subspace. We reduce the size of solution space gradually, and search a feasible solution in the subspace finally obtained. Some numerical experiments are included to evaluate the proposed method.

View full abstract

Modeling and estimating the volatility of financial time series data has been of great importance in financial analysis over the last decade. The early developments are attained by the introduction of autoregressive conditonal heteroskedasticity and its variants. The main purpose of this article is to develop new forecasting models for time series data with heteroskedastic variance, using artificial neural networks. The neural network systems under consideration contain sub-module to estimate the future volatility from the financial data. Finally, in empirical test based on the real Japanese stock market data, we show that the proposed models are superior on their predictive abilities to ordinary neural networks and statistical autoregressive models.

View full abstract

In supply chain management, it is crucial to incorporate the pertinent and timely information on customers into a production resource allocation plan. In this paper, we address a situation where resource shortages may cause unsatisfied demand and the reduction its firm's customer base. We propose a resource allocation system taking advantage of intelligent agent technology. First, the management agent solves a linear program that maximizes the current profit subject to resource constraints. Then, account agents analyze the responses of their customers to possible unsatisfied orders, and participate in an auction process to adjust the preliminary resource allocation plan. We describe the proposed system with an example, and demonstrate its benefits based on a simulation study.

View full abstract

A new identification approach based on an over-sampling scheme is proposed for a Hammerstein model which consists of a nonlinear element followed by a linear dynamic model. Making use of an observation set of the system input and over-sampled output, the unknown linear transfer function model can be identified independently of identification of the nonlinear element. Therefore, it can be clarified that the consistency of the parameter estimates of the linear dynamic part is assured. The nonlinear element is given by a mapping between a given input and recovered intermediate input. The prior information of the nonlinear element is not necessary in the new algorithm.

View full abstract

This paper presents a systematic design of fuzzy control systems based on quadratic performance function and robust stability. First, robust stability conditions for a class of uncertain fuzzy systems are derived. An LMI-based approach is employed to design a robust fuzzy controller. Next, a fuzzy controller design based on quadratic performance indexes is realized by solving a minimization problem of the upper bound of a give quadratic performance index. Furthermore, a mixed control problem that simultaneously considers both of them is defined and solved efficiently by derived LMI conditions. Finally, a design example, stabilization of an inverted pendulum system, shows the effect of the proposed design method.

View full abstract

The excitability of the stretch reflex system can be examined by the gain of the stretch reflex, which includes short latency and long latency components. However, the wrist joint impedance characteristics, such as stiffness, viscosity, and inertia, must be estimated simultaneously in order to analyze the relations between the excitability of stretch reflex system and the wrist joint impedance characteristics. In this paper, we developed a method satisfying this demand using a linear motor system. While the subject maintains a wrist joint torque isometrically, an external disturbance to estimate the wrist joint impedance and to elicit the stretch reflex was applied to the subject's hand. The wrist joint impedance is estimated by a least square method, and the stretch reflex is recorded from the flexor carpi radialis muscle using a surface electromyogram technique. The experimental results showed that the stretch reflex excitability was quasi-linearly facilitated by the increase of the wrist joint torque. Also, the viscosity and the stiffness of the wrist joint were closely related to the stretch reflex excitability, while the inertia of wrist joint was almost constant. Indeed, the natural frequency and the damping coefficient of the wrist joint were linearly related to the increase of the wrist joint torque.

View full abstract

The purpose of this paper is to construct a learning algorithm for variable hierarchical structure learning automata with an S-model nonstationary random environment at each level. The learning propertiy of our algorithm is considered theoretically, and it is proved that the probability finding the optimal objective path can be approached 1 as much as possible by using our algorithm. In numerical simulation, the usefulness of our algorithm is shown.

View full abstract

State-space digital filters can synthesize the optimal filter structure with respect to overall quantization effects, but have many more multiplications than a canonical structure has. Therefore the sampling rate and the latency become important problems on implementing these filters. Especially for the very long latency the control system becomes unstable when these filters are used in the feedback control systems, such as the robot control system.
Previously we proposed a VLSI-oriented highly parallel architecture for state-space digital filters with high sampling rate and small latency. For the purpose of further speeding up and reducing hardware complexity, the distributed arithmetic, of which processing time depends on only word length, was applied to this architecture, making good use of high accuracy of state-space digital filters. Therefore, the very high sampling rate can be implemented independently of the filter order and the numbers of the inputs and outputs.
This paper presents a low power dissipation architecture for our proposed VLSI processor of state-space digital filters using distributed arithmetic. To reduce power dissipation, we replace ROMs using in usual distributed arithmetic with optimal circuits of logical gates. In addition, by applying the properties of filter structures to optimal functional circuits, a more decrease in power dissipation becomes possible. As a result, high-performance VLSI processor is implemented, which has very high sampling rate of 3.9MHz (0.6μm CMOS technology) and low power dissipation of about 2.1W in the case where the filter order is 16. This can decrease power dissipation to about 77% when compared to the VLSI processor using ROMs.

View full abstract

This paper proposes a method of adaptive simulated annealing that can effectively be used for solving combinational optimization problems. This method is based on simulated annealing and performs an adaptive search but without knowledge base. It recognizes characteristics of a problem from search history and adaptively changes its search strategies. The method thus performs search in the neighborhood not randomly but by making use of the search history. This method is applied to an optimal allocation problem of irregular shapes. This problem arises in many industrial production processes, e.g., sheet metal process and cloth cutting process. The problem is known to be very difficult, since many irregular shapes must be handled. A new algorithm for locating irregular shapes is proposed, which is based on people's way of thinking in placing such shapes. Simulation examples show that this algorithm provides natural and good locations for the shapes. The adaptive simulated annealing and the other meta-heuristics, i.e., local search, simulated annealing, genetic algorithm and tabu search, are compared using simulation experiments. The result shows that the adaptive simulated annealing is better than the other mesa-heuristics.

View full abstract

This paper proposes a new model of bacteria including not only intracellular information processing but also motor control on the basis of the molecular evidence. E. coli is chosen as a target bacterium, which has a simple molecular structure and is amenable to biochemical and genetic analysis. We focus on the bacterial intelligent behavior called chemotaxis in order to develop its computer model. Parameters included in the model are determined using an optimization technique in order to maximize a fitness representing a chemotactic ability. Results of the computer simulations are compared with the behavior of E. coli to show the effectiveness and validity of the proposed model.

View full abstract

When the characteristic dimension of a cavity is much greater than the thickness of the thermal boundary layer (δ) the acoustic conductance of the cavity is proportional to the inner surface area of that cavity. On this principle the surface area of an object can be known by measuring the acoustic impedance of the container in which the object is placed. For cavities of the smaller characteristic dimension, however, the acoustic conductance is not accurately proportionate to the cavity surface area since the effect of edges and corners comes to be not negligible. The distributions of acoustically caused temperature variation about edges and corners were investigated numerically. And the edge correction-the equivalent extension of the length and the width of the object in the acoustical surface area measurement-was calculated and found to be 0.6δ. The corner correction-the equivalent reduction of the length of the wall-was also calculated and turned out to be -1.28δ.

View full abstract

A modification of the stabilizing control low for uncertain systems with unmatched unmcertainties was presented by Sei et. al. However, this method has some problems on the effects of stabilizing controls. The report seems to have neglected the fact that, because of the discontinuity of control functions, there can arise sliding modes in system trajectories. Here, it is shown that, in order to prove the stability of the system, further conditions on the uncertain functions are needed.

View full abstract

The vibration control of a cantilever beam with an active mass damper is considered. A hybrid parameter system model is introduced. A linear quadratic regulator is constructed by the lumped-parameter-part feedback, and the feedback gain is tuned to satisfy prescribed H_∞-norm bound.

View full abstract

We describe the fractal structure of fluctuating load of the multi task operating system. The fractal dimension, which is obtained from a computer remains in a certain range. We propose a simple model based on the queuing system theory and make an inquiry about the fractal genaretion by changing the model parameters related to the load distribution. The present approach can provides a plausible fractal very close to that from computer.

View full abstract