Servo mechanism

To evaluate the quantity of interest, i.e., the relative change in reflectance, AR/R, a normalization procedure must be used to eliminate the uninteresting common feature /q(X). In Figure 2 the normalization is performed by the variable neutral density filter (VNDF) connected to a servo mechanism. The dc signal from the detector, which is proportional to /o(A.)./2(A.), is introduced into the servo, which moves the VNDF in such a manner as to keep /Q(k)R(k) constant, i.e., /q(X)R(X) = C. Under these conditions the ac signal Iq(X)ARQC) = CARQC)/RQC. ... 

The methods dependent upon measurement of an electrical property, and those based upon determination of the extent to which radiation is absorbed or upon assessment of the intensity of emitted radiation, all require the use of a suitable instrument, e.g. polarograph, spectrophotometer, etc., and in consequence such methods are referred to as instrumental methods . Instrumental methods are usually much faster than purely chemical procedures, they are normally applicable at concentrations far too small to be amenable to determination by classical methods, and they find wide application in industry. In most cases a microcomputer can be interfaced to the instrument so that absorption curves, polarograms, titration curves, etc., can be plotted automatically, and in fact, by the incorporation of appropriate servo-mechanisms, the whole analytical process may, in suitable cases, be completely automated. 

Servo Mechanism A mechanism which responds to the action of a controlling device and operates as if it were directly actuated by the controlling device. However, it is capable of supplying power output much greater than the original controlling device. The power is derived from an external and independent source. Both mechanical and electrical servo units exist. 

Accdg to Ref 3, p 211, the V-2 missile was regulated in flight by fins which were positioned by hydraulic servo-mechanisms controlled by an elaborate intelligence system. This system consisted of ... 

The principle and use of an optical non-contact extensometer available commercially has been described in some detail77. Two photoelectric sensing devices automatically follow, by means of a servo mechanism, contrastingly coloured gauge marks on the test piece. The separation of the auto followers... 

The total flow rate is controlled by a commercial mass flow controller (MFC), which contains an internal servo mechanism that links a mechanical valve to a resistance thermal device (RTD). The RTD measures mass flow (rather than gas velocity) by the change of electrical resistance in a sensing wire heated by an adjacent hot wire. Because this measurement is affected by the specific heat of the gas, the MFC must be calibrated for each individual gas. The desired MFC flow is set by applying a voltage to the MFC that corresponds to the voltage generated by the RTD at that flow. A comparator in the MFC opens or closes the internal valve to balance the RTD and the applied voltage. 

There are a variety of drive mechanisms commonly used automated dispensing including cable drive, lead screw, and linear motors. Most modern equipment uses closed loop servo mechanisms, although open loop stepper motors can be found in some less expensive equipment. The drive mechanism is not as important as the overall speed and accuracy of the equipment. Other factors, such as the alignment process and dispensing technology often overshadow the characteristics of the drive mechanism. 

Many people have the motor control necessary to operate a motor vehicle, but they do not have the strength required to operate manual hand-controls. Automatic or Fly-By-Wire hand-controls use external actuators (e.g., air motors, servo mechanisms, hydraulic motors) to reduce the force required to operate various vehicle primary controls. Power steering, power brakes, six-way power seats, and power adjustable steering columns can be purchased as factory options on many vehicles. 

Like the point-to-point robot, the continuous path robot is also run in a closed loop. Continuous path systems generate a continuous flow of control data to be fed into the servo mechanisms. The control data are similarly produced as with PTP systems but now in a continuous mode. 

Okazaki Y, Asano S, Goto T (1993) Dual-servo mechanical stage for continuous positioning. Int J Jpn Soc Precis Eng 27(2) 172-173... 

Before the regulating rod was used with its servo mechanism as a control device, experiments were devised to measure its response time. The test consisted in unbalancing the electronic system with an applied voltage (instead of an ion chamber signal) and measuring the time required for rebalancing The response time for the maximum unbalance was found to.be about 0.1 sec and is considered adequate for control of known MTR instabilities. 

Full-scale test of the servo mechanism as an automatic control device was accomplished during the low—power nuclear experiments described in Section A4.5.7. The system performed satisfactorily for several months at power levels from 100 watts to 175 kilowatts. 

A4.5.6 Performance of Control and Safety Circuits. The two instruments in which most interest has been evidenced are the period indicator and the servo mechanism. 

The servo mechanism performed exceptionally well. With this device any desired power level in the operating range could be maintained for hours with... 

Allow the air pressure is in 650/700kPa in the operating area of front servo mechanism (external of Bl), (refer to Figure 8.63). 

Y direction with 0.05 m/s speed until stress of each box maintain at the predetermined constant value through servo mechanism to the end of the experiment. The friction angles of top box, bottom box and soil particles are set to a small value to get a larger compactness, and they are reset to the regular value in accordance with Table 2 after achieving the confining pressure. 

Glass reinforced PA is used to protect brake discs, in the form of stone and splash shields. More significantly, both PA and reinforced PBT have been used for the housings of brake servo mechanisms. Small quantities of more exotic plastics are used in sophisticated ABS systems e.g., injection mouldable fluoropolymers for brake pad sensor housings, and PEEK for carbon brush holders. 

For the purpose of this exampie, faiiure of the gauge is assumed to be possibie at any time, whether the tank is being fiiied or not. it is aiso assumed that the faii-to-danger rate of the gauge is a constant, whether the tank is being fiiied or not (and therefore that faiiures of the transmitter head or servo-mechanisms may occur with equai iikeiihood at any time). Note that this assumption may not be true for all failure modes and would need consideration on a case-by-case basis. 

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