Hitachi, Ltd.

Tokyo Electric Co.

Hitachi Engineering Ltd

Sadao Yanada

Tadahiko Iijima

Takumi Kawai

Seiitsu Nigawara

Hisanori Miyagaki

Minoru Suzuki

Yasuhiro Tennichi

Naganobu Honda

Takeshi Iwamiya

Sigeru Sibata

Tadayoshi Wakita

Yukiyoshi Tani

A method of and apparatus for controlling a triple-coil servo valve arranged having a tripled control system each of which is composed of components of a coil, a servo amplifier and a controller, the method of and the apparatus for controlling the triple servo valve including means for specifying the abnormality of each of the components, servo amplifier output separation means, means capable of desirably combining the components and means for compensating the servo amplifier. If two control systems of the tripled control system are faulty in such a manner that at least one coil, at least one servo amplifier or at least one controller is abnormal, the triple-coil servo is operated by combining the normal components or by compensating the servo amplifier so that the continuation of the operation of the plant is enabled. Although the operation of the plant employing the conventional structure is shut down if two systems of the tripled control system, each of which is composed of the coil, the servo amplifier and the controller, are abnormal, the continuation of the operation can be enabled according to the present invention while preventing a disturbance of the plant even if the two or the three systems are abnormal by combining normal components and by separating the output from the servo amplifier in a case where the servo amplifier is abnormal.

Servo valve control apparatus

A process control system has a timer circuit which fixes operational periods by issuing an instruction for starting each of a plurality of time periods in such a manner that the computation of control blocks will occur during periods of fixed duration. A periodic operation selection circuit selects control blocks to be computed within each time period in response to an instruction from the timer circuit. Control blocks selected by the periodic operation selection circuit and an instruction for completion of the computation of control blocks for each time period are stacked in an operation instruction circuit, which issues an instruction for consecutively executing the operation of the control blocks and an instruction for effecting an idle operation after completion of the operation of control blocks for each time period. When an instruction for starting an ensuing time period is issued from the timer circuit at a time when computation of a control block has not been completed within a predetermined time period, an operation completion determining circuit issues an instruction for starting the computation of the ensuing time period beginning with computation of the remaining control blocks in the predetermined time period and an instruction for stacking control blocks in the ensuing time period in the operation instruction circuit by means of the periodic operation selection circuit.

Process control system and method thereof

A method of controlling the operation of a thermoelectric power generating plant, in which the operation of the steam generating equipment and the turbine is controlled in accordance with the plant operation parameters obtained from given patterns of start up and operation of the plant. The method comprises: temporarily setting, in accordance with the above-mentioned patterns, the plant operation parameters concerning the rates of change of state of the plant such as the rates of turbine acceleration and turbine load and rates of increase of the main steam temperature and pressure; estimating the change of the quantity of state of main steam at a designated future moment; estimating the thermal stresses in respective stress-evaluation portions of the boiler and turbine; comparing the estimated thermal stresses with respective allowable thermal stresses determined so as to correspond to the consumption of the life allowed for each start up and operation cycle of the plant; selecting one of the estimated thermal stresses which has smaller margin to the allowable thermal stress and obtaining the operation parameter which provided the maximum rate of change of the state of the plant; repeating these steps until the command state is attained; and controlling the boiler and the turbine in accordance with the thus obtained plant operation parameter.

Method of controlling operation of thermoelectric power station

A sequence display apparatus including a sequence control circuit, a cathode ray tube control device and a sequence display control device is disclosed in which a keyboard included in the sequence display control device is provided with logical function specifying keys for specifying one of a plurality of logical functions corresponding to such logical circuits as AND, OR and flip-flop circuits and a timer and with keys for inputting the names of input signals and the name of an output signal. One logic function, all of the names of the input signals and the name of the output signal are inputted as one set by the key-in operation, each of a group of command codes which are determined by the kind of logical function and the number of the names of input signals, is added to a corresponding one of the names of the input signals and the name of the output signal which have been inputted, to compose a logical operation program. The names of input signals are collectively displayed at a left end part of the display surface of a cathode ray tube, a position on the display surface for displaying the logic symbol is determined in accordance with the number of input signals, and the arrangement of a line for connecting each of the names of the input signals and the logic symbol is determined on the basis of the state of the display at each of the picture elements forming the display surface.

Sequence display apparatus and method

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Hitachi, Japan

Sadao Yanada