This paper describes a new method of pulse width modulator which can be read out nondestructively by a square wave voltage of comparatively low frequency (here 50Hz). The modulator is constructed from two-hole elements which are made by laminating a sheet of core of Fe-Ni 50% permalloy with square loop properties. The memory holding characteristics of this modulator were investigated experimentally in detail. Then it became clear as a result that there are two modes in the mechanism of the write-in and the readout. The linearity of the readout pulse width characteristics becomes better if the amount of the flux written in is controlled by the constant voltage by means of negative feedback. The difference of the first pulse width from the second one which was read out at a drive time is especially larger than the difference of the second from the third, etc. Then this second readout pulse width was selected as the standard one, and the memory holding characteristics were represented by the difference between the readout pulse width and standard one for the number of the readout.
The adequate selection of the compensation winding and the bias voltage can make this difference within ±0.5%. The use of the write-in method due to the feedback setting can make this difference within 0.25% in the range of 1, 000 times of the readout.

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Recently, electro-hydraulic servovalves have come to be used widely in hydraulic control, but the complexity of their construction is unfavourable. Needless to say, servovalves without any moving parts are desirable from the viewpoint of fast-response, efficiency and reliability.
So, the purpose of this research, as the first step to the desirable servovalves, is to develope a new servovalve adopting a piezoelectric flapper directly actuated by an electric signal. A piezoelectric flapper, adopted instead of a conventional torque motor and a flapper, consists of piezoelectric slabs and a steel slab. As the result of the preliminary experiments, it was clarified that this flapper could be practically used if the adverse effect of its inherently strong hysteresis is removed.
In this research in order to give the flapper equivalently linear characteristics, the input signal to the flapper is given in the form of a pulse width modulated wave. However, in this case the output of the pulse width modulator consists of the various frequency components depending on the input and the carrier frequency. It is well-known that the signal cannot be accurately transmitted, when the ratio of the carrier frequency to the input frequency becomes small. So, one of the most important points of this paper is to establish the conditions of the accurate signal transmission in the P.W.M. mode operation.
As the results of the experiments on the new servovalve, it has become clear that in spite of the strong hysteresis, the new flapper has equivalently linear characteristics, when driven by the pulse width modulated wave from the modulator. Futhermore it has been clarified theoretically and experimentally that for accurate signal transmission through the modulator, the carrier frequency must be higher than seven times the highest frequency of the input signal components.

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This study deals with a hydraulic actuator system which is operated by two 2-way solenoid valves in the PWM-Digital mode. The solenoid valves act as converters of electronic-pulse signals to hydraulic-ones.
It is considered that the dynamic characteristics of the system depend largely on the be h avior of on/off action of the solenoid valves. The response performance of the system, for example, might be inevitably affected by the time lag existing between the input and output signals of the valves. Details of such effects of the solenoid valves, however, have yet to be satisfactorily clarified, mainly because an adequate mathematical model for the system has not been developed.
The object of this study is, therefore, to prop o se a mathematical model for the PWM-actuator system. The dynamic charateristics of the system are investigated by the method of digital simulation based on the proposed model. The simulated time responses are compared with the measured ones to confirm the validity of the mathematical model.

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A pneumatic servo presented has a feature to set a by-pass valve in a conduit with a proper resistance connecting both rooms in the power cylinder, and to make the valve open and closed at each proper time for the improvement of damping in positioning of the step response. In application of this method to a single rod cylinder, a distinct difference is found between cases of extension and retraction of the piston. In the latter case, the merits of the by-pass method are reduced a little, so another little modefied method also has been examined. Means of making use of the by-pass valve properly including the case of double rod cylinder are presented to each case. Experimental results are compared with computer simulations, and good coincidence is obtained.

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If we could realize a power variable resistor of which resistance can be varied at will, we would have many applications of it in the field of control and measurement.
For this purpose, a mechanical variable resistor is not adequate in its response and available power. The thyristor variable resistor to be mentioned here is a power variable resistor in which the equivalent resistance between two terminals is varied by means of controlling thyristor switches. Owing to the use of thyristors, we can expect the variable resistor to have a fast response as compared with mechanical ones.
In this paper, we describe the thyristor variable resistor circuit using choppers and constant resistor element. This circuit can be used in both DC and AC systems. From the circuit analyses, we obtain the equivalent resistance and its practical variable range. Furthermore we give an example of thyristor gate control circuit to get the linear characteristics. Next we give the design criterion of the filter that absorbs the variation of the load current occurred by the switching. Lastly we exhibit the experimental circuit which has the variable range from 10 to 100Ω and the rate current 10A. We obtained satisfactory test results.

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Quick response solenoid valves acting as simple on-off hydraulic control devices are inexpensive and easy to operate. There are several hydraulic cylinder control methods using the quick response solenoid valves, which control the flow rate by varying the number of opened valves. Based on these methods, multiple valves open and close simultaneously so that the flow rate and the corresponding cylinder motion become stepwise. This might cause noise and/or vibration on the hydraulic system or the machinery moved by the cylinder. We have developed a new hydraulic cylinder control method to cope with this problem. Based on the method, in addition to the number of the opened valves, the period of the open time of each valve is appropriately controlled, while shifting the timing of the opening action. This improves the continuity of the cylinder motion in a wide range of flow rate. This paper presents the specification of the method and the result of application to the servo control of heavy machinery.

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In this paper, authors propose the new measuring method of the density of dc current flowing in solution by the way of feedback Current Pulse-width-Modulation method (C.P.M. method) using a pair of Hg-Cl electrodes with less polarization and quick response of rise-time of micro-second region.
C.P. M method is the one of zero-compensation methods balancing the integral of current flowing in solution with respect to time, by the integral of pulse current which the pulse height and width are known as yet.
On the basis of C.P. M method, authors manufactured the measurement apparatus as trial and tried to measure the density of current ranging of order of about mA/m².
As the results, it is shown that the density of dc current flowing in solution is able to be measured free from the conductivity of solution and this method is applicable for the measurement of density of stepchanging current flowing in solution.

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LEDアレイ書込装置を用い，電子写真方式で4ドラム感光体と4色現像装置にてカラー画像を得るタンテム型のプリンタを研究した．特にLEDアレイのカラー用階調性検討ができるLEDアレイの開発を行い，光量バラツキ，LEDドットの機械的位置精度，熱による影響などを解析した．またタンデム型特有の色ズレに関し4個の感光体とその駆動系，記録紙搬送機構系，書込系LEDアレイとの関連を解析した．さらに，LEDアレイにてカラー多値階調点灯制御するパルス制御を検討し，パルス変調と階調性の関係，光量バラツキの補正方法，画像データのテータ転送速度についても論じた．その結果，カラー面像として色ズレ0．1mm以下を達成出来，階調性も32階調以上の画像を得ることができることが分った．

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The high accuracy position servo system of pneumatic cylinder is already reported by using a diaphragm-type electro-pneumatic converter. In this paper, a novel simple high accuracy position servo system are shown by using high response solenoid valves. The actuating part consists only of two valves and a cylinder. The valves open or close by a pulsating signal and charge the air to the cylinder or discharge from the cylinder directly. The pulse time duration and interval change with position of piston and this is not same as the conventional PWM method. To realize high accuracy piston displacement, the interval becomes as short as 0.005 s when the piston approaches near by the desired point.
The characteristics of this servo system are given by using a system model, and the relationship between stability of the piston displacement and valve opening duration can be shown theoretically. The single rod-type cylinder with 40 mm bore and 100 mm stroke is tested experimentally. As a result of repeated positioning test, it was shown that the piston keeps moving slightly at the desired point but it is able to position within 0.01 mm to the point.

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Pneumatic actuators are less expensive and have higher power/weight ratio than other types of actuators. On the other hand, it is very difficult to control the pneumatic actuators because of uncertainties caused by the nonlinear pneumatic circuit and large friction caused by mechanical contact between piston-ring and cylinder. Then the pneumatic actuator has hardly applied to precise positioning and smooth drive control.
In this paper we applied optimal control theory and model feedback control scheme to control of the pneumatic cylinder in order to realize both the precise positioning and the smooth driving. The effectiveness of the proposed control system is shown through experiments. Results of these experiments are compared with the results which were carried out by fuzzy control logic.

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To realize a continuous fine motion control with a pneumatic actuator, the electronical intelligent control is required, in which an electro-pneumatic conversion is essential. In this study, by introducing a Pulse-Code-Modulation (PCM) technique into this conversion, the microcomputer controlled digital pneumatic servo system with a pneumatic cylinder and on-off solenoid valves is proposed. Its positioning performance is experimentally examined to obtain the following results.
1) The PCM technique enables the continuous control with only on-off solenoid valves, in which the control signal directly corresponds to the binary signal. Therefore this method is suitable for the microcomputer control and much practical as a digital control method of a pneumatic actuator.
2) In the repetitive positioning, the learning control modifying the reference input based on the preceding positioning error is much effective to eliminate the unpredictable errors due to the sliding friction and so on.
3) Under some conditions the nonlinear friction makes the stopping manner change to largely decrease the positioning accuracy. When unchanged, the scattering amount of the repetitive stopping position almost agrees with the minimum resolution distance in the PCM. The experimental system can realize the positioning accuracy of about ±0.25mm.
4) In the PCM control, the maximum piston speed must be constrained for the satisfactory positioning accuracy. To prevent the positioning time increasing due to this constraint, the positioning method added the open-loop controlled high speed region is proposed and its effectiveness is proved.

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There are several methods of Pulse Width Modulation (PWM). For any method, the output of the pulse width modulator corresponding to a sinusoidal input consists of the various frequency components, depending on the frequencies of the input and the carrier. Generally speaking, some frequency components lower than the input frequency are mixed therein. When the ratio of the carrier frequency (fc) to the input frequency (fe) becomes small, the signal cannot be accurately transmitted, because these components become large. In communication, it is easy to make this ratio large enough. On the other hand, in control, the carrier frequency (fc) is limited by some function of the equipment in the systems, and it is required to broaden the bandwidth of the systems as far as possible. So it is important to use a method by which a frequency signal as high as possible can be transmitted on a constant (fc). For the above method it is necessary to clarify the limit of the ratio (fc/fe) from the viewpoint of accurate signal transmission.
In this paper, four typical modulators are shown. First their characteristics are analyzed theoretically. Second each modulator is compared from the viewpoints of the frequency characteristics and the so-called “effect of the removal of time independent nonlinearities” this is the significant advantage of the PWM. Finally as the result of the comparison, it is concluded that the method using both edges is the best one.

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