Ïn this paper, the authors have established the design criteria by which mean-squared-error value is minimized. Though they are rough, we can apply them effectively for the design of compensator.
When noise is present, Wiener's theory of Optimum Filter is applied, and when noise is negligiblly small, the saturation of the controlled process is taken into consideration, using Booton's linearization.
If the bandwidth of control system is sufficiently larger than that of input signal and noise is small, it is shown that our criteria agree with those which minimize the integrated squared-error value for step input. Some examples of design by those criteria are also shown.

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The output member of an actual servomechanism has always the Coulomb friction. We show the effect of the Coulomb friction on the parameters in a 2nd order servomechanism, which uses a D. C armature-controlled servomotor. First, we assume that the Coulomb friction can be treated as the viscous friction varied with the output speed. Then we can use the well-known transfer function of a servomotor, in which Kv and Tm, are the functions of output speed. Therefore, the damping ratio ξ and the natural frequency of the closed-loop system also vary with the output speed. Because the Coulomb friction increases the steady state error and causes the delay in the response, we propose a method of cancelling out the Coulomb friction and linearizing the system by impressing the compensating voltage to the controller. Furthermore, we present a new servo system, in which the Coulomb friction is utilized to improve the response by stopping the cancellation intermittently according to the combinations of the signs of error and output velocity. Sometimes the limit cycle occurs in the linearized system, but the stable system with very small steady state error is obtained in the latter case.

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This paper describes a servo analyzer which is based upon the principle of correlation between the output from a measured system and the special rectangular waves. These special waves are formed by cutting away the width of π/6 radians from both sides of the normal rectangular waves as shown in Fig. 2 (b), (c).
The operating principle of this apparatus is as follows:
A measured system is given the sinusoidal input which is generated by signal generator driven by rate servo. The output from a measured system is multiplied by two special rectangular waves out of phase by π/2 to each other by means of a simple multiplying switch (shown in Fig. 6) coupled to the output shaft of rate servo. These two multiplied outputs are integrated respectively during adequate period. These integrated signals are given to XY recorder. Thus the Nyquist diagram is automatically plotted.
The advantages of this method are that the measurement over the frequency range 1-100 cps is possible because of the simple construction of multiplying switch, and that the accuracy of measurement is considerably good even in case of measured systems containing nonlinearity.

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A new method for automatic measurement of dynamic characteristics of the process has been developed. By this method the transfer function of the 1st or the 2nd order system can be measured without disturbing the operation of the system. Experimental results are shown to demonstrate the validity of the theory.
The measuring system is composed of several filters and a kind of the simultaneous solver, which includes several multipliers

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The conventional pneumatic control valves are inferior to other control components in the static and dynamic characteristics because of followings:(1) Friction at gland packings, (2) Undesirable characteristics induced by springs and (3) Inaccurate shape of inner valves.
The author examined some glandless control valves of which principle was similar to that of commonly used pilot valves. They were superior to the usual control valves in the above characteristics, besides were able to be made more compactly and economically. Some discussion on the limitations in their application were also given.

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