US 4,133,615 AGrant
Microprocessor-Based, Programmed Turbine Speed Control System
Issue Date:1979-01-09
•7 Claims
•7 Drawing Sheets
Abstract
A microprocessor-based control system for controlling the speed of a steam turbine by governing the steam supplied thereto from a steam supply source using one or more hydraulically operated servomotor throttle valves is disclosed. The operation of the speed controller is characterized by a plurality of permanently pre-programmed read-only memories containing sets of instructions and data words arranged in an addressable order. The instructions and data words are synchronously processed by the microprocessor as governed by a system clock. Apparatus is provided to initialize the status of the speed controller under the control of the microprocessor in accordance with the processing of one portion of the sets of programmed instructions and data words thereby. The remaining portion of the program is processed by the microprocessor as governed by a real time clock for coordinating the operation of an operator's panel interfaced to the controller and for monitoring the turbine speed and controlling the position of the one or more valve servomotors in accordance therewith. The subportion of the remaining portion of the program primarily characterizing the panel coordination functions is processed during each even period of the real time clock. Accordingly, the subportion of the remaining portion of the program primarily characterizing the turbine speed control is processed during the odd periods of the real time clock.
Metadata
Assignee
- Westinghouse Electric Corporation
Inventors
- William E. Zitelli
- James M. Mussler
Application Information
Application Number:US 787636&
Filing Date:1977-04-14
Priority Date:1977-04-14
Art Unit:343
Classifications
IPC:
F01D 1706
Field of Search:
4151;30;36;40;42;43
Patent Drawings (7 sheets)
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a speed control system for controlling the speed of a turbine by modulating the position of a servomotor throttle valve disposed between the turbine and a stream source for controlling the admission of steam to the turbine, and more particularly, to a microprocessor-based control system incorporating a plurality of permanently pre-programmed read-only-memories which characterize the operation of the speed control system.
2. Prior Art Discussion
Recently, general purpose minicomputer systems have been developed for the purposes of controlling the speed and load of a steam turbine. Minicomputer-based turbine controllers, similar to that described in the U.S. application, Ser. No. 722,799 (abandoned), entitled "Improved System And Method For Operating A Steam Turbine And Electric Power Generating Plant"; filed by Giras and Birnbaum on Apr. 4, 1968 and continued as Ser. No. 124,993 on Mar. 16, 1971 and Ser. No. 319,115 (abandoned) on Dec. 29, 1972 and Ser. No. 720,725 on Sept. 7, 1976, permitted turbine control operation to be characterized by a set of programs. Quite a few large turbine systems could justify the expense of a general purpose, minicomputer-based turbine controller because of the added features of automatic start-up, synchronization and automatic efficient load control afforded thereby. However, some municipalities and industrial complexes employ smaller turbines, on the order of 300 megawatts of less, which incorporate simple steam admission control valving arrangements usually actuated by mechanical-hydraulic servomotors as opposed to the large turbines, say 1,000 megawatts or greater, which use a variety of complex electrohydraulic actuated valving arrangements. These smaller turbines have generally been controlled by an operator using a basic fixed hardwired digital speed controller such as that described in U.S. Pat. No. 3,802,188; by Barrett, issued Apr. 9, 1974. In these cases, the operator performs the protective control of the turbine, manually, according to a set of operational limitations provided to him by the turbine manufacturer.
Presently, there exists some controversy surrounding the effectiveness of using a general purpose minicomputer-based machine for controlling small turbines, particularly where only a single loop speed control function is required. Normally, each general purpose minicomputer incorporates a number of system software type programs for coordinating the operation of the circuitry associated therewith. In order to apply a minicomputer to a specific function, one must, for the most part, be fully knowledgeable of the "operating systems" software package corresponding thereto. These "operating systems" dictate the priority structuring and arrangement of the sets of instructions and data programmed therein for the purposes relating to steam turbine speed control applications, for example.
Programs associated with both application and circuit operation are generally stored on rolls of punched paper tape prior to being entered into the minicomputer system. The order in which programs are entered into the read/write memory of the minicomputer system is performed in accordance with the specific system program generation procedures outlined by the "operating system" corresponding to the minicomputer used. Accordingly, additional peripheral equipment, non-essential to the control of the process, such as a tape punch, a tape reader and a teletypewriter are generally needed to ensure that proper program loading techniques have been instituted and that the programs have been assigned to the correct memory areas as a result of the loading process. It has become necessary then to not only be knowledgeable about the process that is to be controlled, but to also become equally knowledgeable about the complexities involved in loading the programs into the minicomputer systems being used in accordance with the procedures of its "operating system".
Present minicomputer systems also involve read/write memory which is susceptible to electrical noise "spikes" which occur frequently in power plant environments. Frequent occurrences of these "spikes" may cause a change in an instruction in the read/write memory which could be responsible for an eventual shutdown of the turbine process.
SUMMARY OF THE INVENTION
In accordance with the present invention, a system architecture more specifically related to the process being controlled, the speed of a steam turbine, is provided to improve the effectiveness of computerized control thereof. The cost advantages of time sharing a central processor using sets of instructions and data words programmed in memory for the operational characterization of the speed controller functions is maintained. Further the invention provides for permanent storage of the characterizing instructions and data words in easily installable modular pre-programmed memory devices to eliminate the need for peripheral loading and validity checking equipment and the program loading techniques associated therewith. In addition, the permanent memory storage will enhance the protection against electrically induced noise "spikes" and will effect the emulation of a hardwired system power-on operation. Also, a system not limited to an "operating system" software package is provided to permit a more basic program organization at the bit control level for the purposes of controlling the speed of a steam turbine.
More specifically, a microprocessor-based control system controls the speed of a steam turbine by governing the steam supplied thereto using one or more hydraulically operated servomotor throttle valves. Characterizing sets of instruction and data words, permanently pre-programmed in read-only-memories, are processed by a microprocessor as governed by a system clock. Apparatus is provided to initialize the status of the speed controller under the control of the microprocessor in accordance with the processing of one portion of the sets of programmed instructions and data words thereby. The remaining portion of the program is processed by the microprocessor as governed by a real time clock for coordinating the operation of an operator's panel interfaced to the controller and for monitoring the turbine speed and controlling the position of the one or more valve servomotors in accordance therewith. The sub-portion of the remaining portion of the program primarily characterizing the panel coordination function is processed during each even period of the real time clock. Accordingly, the subportion of the remaining portion of the program primarily characterizing the turbine speed control is processed during the odd periods of the real time clock.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic block diagram of a turbine speed control system and a steam turbine system embodying the present invention;
FIG. 2 is a detailed schematic of relay logic suitable for use in the control system of FIG. 1;
FIG. 3 is a schematic diagram illustrating a typical control fluid pressure system;
FIG. 4 is a diagram of a panel layout suitable for use in the control system of FIG. 1;
FIG. 5 is a schematic wiring diagram of the panel depicted in FIG. 4;
FIG. 6 is a schematic block diagram of a speed monitoring and digital input interface unit for use in the system of FIG. 1;
FIG. 7 is a schematic block diagram of a speed control signal generator, digital output and program malfunction detect interface unit for use in the system of FIG. 1;
FIG. 8 is a schematic block diagram of a panel display driver interface unit for use in the system of FIG. 1;
FIG. 9 is a schematic block diagram of a digital input and output interface unit for use in interfacing the panel and the speed controller of FIG. 1; and
FIGS. 10, 11A, 11B and 12 are program flowcharts depicting a sequence in which the instructions and data words, pre-programmed in the read-only-memories, may be executed by the microprocessor of the speed controller of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
1. Overall System Architecture
Referring to FIG. 1, a microprocessor-based turbine speed controller 1 may be used to control the speed of a steam turbine system 2 in accordance with an operational characterization programmed therein. Steam is supplied to a steam turbine 3 from a conventional steam source 4 through steam piping 5. One or more steam admission valves 6 which may be of the throttle valve servomotor type are actuated by a control fluid pressure system 7 to govern the steam flow to the steam turbine 3. Steam exhausts from the steam turbine 3 through exhaust piping 8 to a condenser 10. As steam expands through the steam turbine 3, energy is transferred to the turbine blading, not shown in FIG. 1, to exert a torque on a turbine shaft 11. The net torque of the steam turbine 3 imparted to the shaft 11 accelerates the shaft to a desired speed. Speed may be detected by utilizing a notched wheel 12 attached to turbine shaft 11 and a standard variable reluctance type detector 13 coupled adjacent thereto, for example. Detector 13 normally generates a periodic time varying signal of a waveform similar in nature to a sine wave over signal line 14. The frequency of the generated time varying waveform is generally proportional to the speed of the turbine shaft 11. The speed signal generated over line 14 is monitored by speed controller 1 and a speed control signal 15A and return signal path 15B are provided thereby in accordance with the programmed operational characteristics thereof. An operator's panel 16 is used to coordinate the speed control activities of the speed controller 1 in both an automatic or supervisory mode.
More specifically, a microprocessor 18 processes instructions contained in a plurality of memory devices 19, 20, 21, 22 to read in data, to perform logical or arithmetic operations on data contained therein, and to write out processed data. A selected portion of the processed data may be stored in a temporary storage device 23. The microprocessor 18 additionally controls the flow of input/output (I/O) data using a plurality of programmed interface units 25, 26, 27 and 28. All of the aforementioned devices 18 through 28 may be connected in parallel to a common microprocessor bus 30 which includes signal conduction portions for an address word 31, bidirectional data words 32 and control signals 33. Digital input and output signals are conditioned prior to being monitored and controlled by signal conditioning functions 35, 37 and 38 which are coupled to interface units 25, 27 and 28, respectively. Digital inputs 41 and 43 are provided in this embodiment from push buttons on control panel 16 and from contacts in relay logic 1A identifying the status thereof. Digital output signal 44 and 46 are supplied for the purpose of this embodiment to drive status lamps on the control panel. Additional digital output signals 47 are suitable for driving digital binary coded decimal (BCD) displays, which are located on the operator's panel 16, through panel display buffer 48 which is coupled to interface unit 26.
The periodic time varying speed signal of signal line 14 is an input to the speed monitoring interface 54 which, in turn, is coupled to the interface unit 27. Accordingly, a digital speed control signal 55 is generated from the interface unit 28 and converted to the analog speed control signal 15A by a speed control signal generator 56. The speed control signal 15A is transformed by relay logic 1A into signal 15C which eventually controls a torque motor (see FIG. 3) in the control fluid pressure system 7 to govern the positions of the one or more inlet steam admission valve servomotors 6 which vary the steam conducted to the steam turbine 3 thereby controlling the speed of the turbine 3. An arrangement of switches 58 are also coupled to the interface unit 27. The switches 58 may be positioned in a plurality of states as will be described in further detail herebelow.
Such that the transfer of the address word 31, the data word 32 and control signals 33 are conducted over the microprocessor bus 30 synchronous to the sequential processing operations of the microprocessor 18, a system clock generator 60 is provided. A system clock signal 61 generated thereby is distributed to all of the devices coupled to the microprocessor bus 30. A real time clock signal 62 is also generated by the generator 60 and supplied to the speed monitoring interface 54 and the interface unit 27. Initialization of the turbine speed controller 1 is initiated by the power-on initialization circuit 64 by supplying an initialization signal 65 to the microprocessor 18 and interface units 25, 26, 27 and 28. To identify a malfunction in program execution of the microprocessor 18, a failure detect circuit 66 is coupled to interface unit 28 to provide a failure detect signal 67 which energizes a relay in relay logic 1A.
To provide turbine protection, relay logic 1A is provided to condition the speed control signal 15A in accordance with an auto stop latch (ASL) signal provided by a conventional turbine trip system 2A. The ASL signal is true only at times when the hydraulic fluid used to control the positions of the steam admission valves 6 is at a sufficient pressure to adequately perform the hydraulically controlled positioning of the servomotors 6.
For the purposes of this embodiment, a family of large scale integrated (LSI) circuit devices similar to that manufactured by Motorola Semiconductor Products, Inc., namely the M6800 Microcomputer Family, are used. The microprocessor 18 may be of the type MC6800 Microprocessing Unit (MPU); the temporary storage memory device 23 may be of the type MCM6810 Static Random Access Memory (128 .times. 8); the interface units 25 through 28 may be of the type MC6820 Peripheral Interface Adapter (PIA) -- all manufactured by Motorola. The memory devices 19, 20, 21 and 22 may be of the type manufactured by Intel Corp. Model No. 3604 programmable read-only-memory (PROM) wherein each device may store 512 8-bit words. The selected addressable order in which predetermined instructions and data words are permanently programmed in the memory devices as will be described in greater detail herebelow shall characterize the sequential operation of the speed controller 1. The speed controller 1 is similar to the one described in U.S. Patent application Ser. No. 771,141, entitled "A Programmable Turbine Speed Controller" filed on Feb. 23, 1977 by Zitelli, Mussler and Szabo which is incorporated by reference herein to provide a description of the apparatus and operation thereof in greater detail.
Typically, the operation of the speed controller 1 starts from the power V+ being turned on. The power-on initialization circuit 64 detects the power turn-on condition and responds by sending an initialization pulse of a pre-selected time duration over line 65 to the microprocessor 18 and interface units 25 through 28. A plurality of programming registers contained in the interface units, not shown in FIG. 1, are cleared to all logical zeros during the initialization pulse. The microprocessor 18 responds to the reset pulse by vectoring to its starting instruction address as programmed in one of the memory devices 19 through 22. After the initialization pulse, the microprocessor 18 proceeds to process the programmed instructions of the memory devices 19 through 22 at a frequency controlled by the system clock signal 61. At times, designated by the addressable order of the instructions of the memory, the microprocessor 18 may address one or more of the registers contained in the interface units 25 through 28 to read data from or write data into said registers as controlled by the system clock signal 61, state of the control signals 33 and address of the corresponding register. This will be explained in more detail herebelow.
Normally the speed signal 14 as conditioned by the speed monitoring interface 54 is read in by the microprocessor 18 at a minimum frequency which will allow stable control of the steam turbine 2. The speed signal monitoring frequency is usually determined by the real time clock signal 62. Likewise, the speed control signal generator 56 may be updated at a similar frequency to ensure stable control of the steam turbine 2 by the speed control signal 15A. The operation of the turbine controller 1 is characterized by the set of programmed memory devices 19 through 22 to read in a speed signal data word through interface unit 27, to operate on this speed signal and to generate a new speed control signal 55 which is written out to interface unit 56. Digital outputs included in signals 44, 46 and 47 which are coupled to status lamps, and displays on operator's control panel 16 are updated at a frequency synchronous to the clock signal 62. Normally, the digital inputs included in signals 41 and 43 change state asynchronous to the clock signal 62, however these digital input states are monitored at times synchronous to the real time clock frequency signal 62. That data which is constantly being updated by the processing operation of the microprocessor 18 may be temporarily stored in predetermined addressed registers of the temporary storage memory 23.
Referring to FIG. 2, the ASL signal from the conventional turbine trip system 2A energizes a relay ASLR when in the true state. The relay is supplied with power by voltage source, Vcc.sup.+. When energized, relay ASLR closes normally open, NO, contacts CC6 and CC7 and opens normally closed, NC contact CC5. In addition, when NO contact CC6 is closed, a signal path is provided between the failure detect signal 67 and another relay DCS. If speed controller 1 is functioning properly, signal 67 is permitted to energize relay DCS only if relay ASLR is energized. When relay DCS is de-energized, NO contact CC1 "open circuits" signal 15A from 15C and NC contact CC2 "short circuits" signal 15C to 15B which is at essentially ground potential for the purposes of this embodiment. When relay DCS is energized, NO contacts CC1 and CC4 are closed and NC contact CC2 and CC3 are opened.
In operation then, as the hydraulic pressure for operating the valve servomotors 6 increases to an adequate level, signal ASL becomes true energizing relay ASLR. Signal 100 which is a portion of 43B is conducted to ground potential and signal 102 which is a portion of 43C is disconnected from ground potential and a signal path is provided between signal 67 and relay DCS. If speed controller 1 is functioning, signal 67 will energize relay DCS. Signal 15C will be disconnected from ground potential and conducted to signal 15A. Signal 104 which is a portion of 43B is conducted to ground potential and signal 106 which is a portion of 43C is disconnected from ground potential. Should a "turbine trip" be initiated during a speed control operation, both relays ASLR and DCS will become de-energized as a result of ASL becoming false. All relay contacts will respond to their normal de-energized state.
In FIG. 3, the pressure in the control fluid signal line 7A is controlled either automatically or manually from a control fluid supply source 110. Under automatic operation, a conventional cup valve arrangement 112 is tightly closed by either a handwheel 114 or an electric motor 116 which are both geared in a conventional manner to position the cup valve 112. With cup valve tightly closed, no control fluid is permitted to flow through check valve 118 and piping 120 to drain 122 thereby eliminating the effects of this manual portion of the control fluid pressure system 7. In accordance with automatic control, a torque motor 124 is controlled by speed control signal 15C and return line 15B to position another conventional cup valve arrangement 126 coupled thereto. The position of the cup valve 126 controls the flow of control fluid from control line 7A through a check valve 128 and a typically motor operated valve 130 to drain 132 using line 134. The amount of flow of control fluid from line 7A fixes the pressure therein and it is this pressure which positions the steam admission servomotor valve 6 as shown in FIG. 1.
In the present embodiment, should a malfunction in the speed controller 1 occur or a loss in hydraulic fluid pressure occur, the associated DCS relay or both relays, as the case, may become de-energized causing the signals 15C and 15B coupled to the torque motor 124 to be "shorted" together. With no signal supplied thereto, the torque motor 124 opens the cup valve 126 to a wide open position such to bring the pressure in line 7A to a substantially low state. This low pressure in line 7A will bring the servomotor valve 6 to a closed position. A suitable method of transferring to manual control of the pressure in the control line 7A is to first crank open cup valve 112 with either the handwheel 114 or electric motor 116. When the pressures in the lines 120 and 134 are brought to within +1 PSI of each other as detected by a differential pressure switch 136, the motor actuated valve 130 is permitted to close. Control of the position of the cup valve 112 will maintain the control fluid pressure in line 7A once the automatic portion of the control fluid pressure system 7 is no longer effective.
An operator's control panel 16 used for the purposes of controlling the speed of a turbine system through the utilization of the speed controller 1 is shown in FIG. 4. A display window DP1 which may be comprised of four numerical digits can be affected to display either a speed reference signal or an actual speed signal using a pushbutton PB4. The split lens backlighting of PB4 provides an indication to the operator as to which parameter is displayed in the display window DP1. A display window DP2 which may also be comprised of four numerical digits can be affected to display either a desired acceleration of the speed reference signal or a desired speed demand (target) of the speed reference using a pushbutton PB1. The split lens backlighting of pushbutton PB1 provides an indication to the operator as to which parameter is displayed in the display window DP2.
Decrease and increase pushbuttons, PB2 and PB3, respectively, when depressed, perform mutually exclusive operations to set the parameter in window display DP2 to a desired setting. For example, if the speed controller 1 is controlling turbine speed around a speed reference setting of 1800 RPM and it is desired to increase that speed to 2100 RPM per minute, the acceleration parameter is entered in the window DP2 and the increase or decrease pushbuttons, PB3 or PB4, is depressed to bring the acceleration to 200 RPM. A suitable algorithm is used to step the displayed parameter to that desired as a function of the number of integer seconds that the pushbutton, PB2 or PB3, is depressed. That algorithm may be expressed by the following equation: ##EQU1## where N.sub.n .tbd. the integer variation in the window parameter for n seconds, and
n .tbd. total time in seconds that pushbutton was depressed.
Suppose that in our example, the acceleration is presently set at 319 RPM per minute. To bring the acceleration to 200 RPM per minute, the decrease PB2 is depressed for 15 seconds for a total decrease of 120 in accordance with equation (1) above which results in a reading of 199. Then, the increase PB3 is depressed for 1 second resulting in the desired acceleration setting of 200 RPM per minute in window DP2. Similarly, the speed demand may be set by just entering the speed demand parameter in DP2 using PB1 and then, exclusively depressing either pushbutton PB2 or PB3 to set the desired value.
To initiate the ramping of the speed reference to its demand (target) value at the desired acceleration, a GO pushbutton PB6 must be depressed. The pushbutton is backlighted to provide an indication to the operation of the operation which is being performed. The speed reference ramping may be inhibited at any time by depressing a HOLD pushbutton PB5 which is also backlighted during a HOLD mode. To re-initiate the ramping operation, pushbutton PB6 is again depressed. When the speed reference becomes equal to the speed demand setting the ramping operation is terminated.
Light emitting diode (LED) monitor lamps L1, L2 and L3 are provided on panel 16 to indicate status. The Turbine Trip lamp L3 is lit in response to the de-energized state of the ASLR relay of FIG. 2 using signal line 102 as shown in FIG. 5. The Manual lamp L2 is lit in response to the de-energized state of the DCS relay of FIG. 2 using signal line 106 as shown in FIG. 5. The Speed Control Monitor lamp L1 is lit by the speed controller during times when the error between the speed reference and actual speed is beyond a predetermined value. A power-on pushbutton PBO is supplied with the panel 16 to provide power from a source to the speed controller system. The pushbutton PBO is mechanically fashioned to backlight when power is turned on.
The cooperation between depressing pushbuttons, backlighting pushbuttons, displaying parameters and status as previously described above in connection with panel 16 is all performed in accordance with instructions as preprogrammed in a fixed addressable order in the PROM devices 19 through 22 of the speed controller 1. These operations will be better understood after reading the program organization and operation section which is described in detail herebelow. A possible apparatus structure to permit control of the operator's panel 16 by the speed controller is as shown in FIG. 5. FIGS. 6, 7, 8 and 9 will be referred to from time to time in connection with the description of the schematic depicted by FIG. 5.
In FIG. 5, signal lines 110 and 112 respectively couple the pushbutton switches of PB1 and PB4 to the signal conditioning circuits 190 of bits 0 and 1 of the A side of the interface unit 27 as shown in FIG. 6. Signal line 114 and 116 respectively couple the speed demand and acceleration split lens backlight indicators of PB1 with the output driver circuits 197 of bits 4 and 5 of the B side of the interface unit 28 as shown in FIG. 7. Signal lines 118 and 120 respectively couple the actual speed and speed reference split lens backlight indicators of PB4 with the output buffer circuits 197 of bits 6 and 7 of the B side of interface circuit 28 as shown in FIG. 7. Signal lines 122, 124, 126 and 128 respectively couple the pushbutton switches of PB5, PB6, PB3 and PB2 to the signal conditioning input circuits 190 of the bits 0, 1, 2 and 3 of the A side of interface unit 25 as shown in FIG. 9. Also, signal lines 130, 132, 134 and 136 respectively coupled the backlight indicators of PB5, PB6, PB3 and PB2 to the output driver circuits 197 of bits 0, 1, 2 and 3 of the B side of interface unit 25 as shown in FIG. 9. Accordingly, signal line 138 couples the LED status lamp L1 with the output driver circuit 197 of bit 4 of the B side of interface unit 25. All of the backlight indicators of the pushbuttons are supplied power from Vcc.sup.+. The LED status lamps are supplied power from Vc.sup.+ through current limiting resistors R1, R2 and R3 associated therewith.
Each adjacent two digits of window displays DP1 and DP2 enter display information from 8-bits of "bused" data supplied thereto in accordance with a strobed gate signal. More specifically, signal lines 150, 152, 154 and 156 respectively couple the binary coded decimal (BCD) data from the lower order digit of each of the adjacent sets of digits to the display drivers 48 of bits 0, 1, 2 and 3 of the A side of the interface unit 26 as shown in FIGS. 5 and 8. Also, signal lines 158, 160, 162 and 164 respectively couple the BCD data from the higher order digit of each of the adjacent sets of digits to the display drivers 48 of bits 4, 5, 6 and 7 of the A side of the interface unit 26. Gating signals 166, 168, 170 and 172 are respectively coupled from the display drivers 48 of bits 4, 5, 6 and 7 of the B side of interface unit 26 to adjacent displays 140-141, 142-143, 144-145 and 146-147.
Referring to FIG. 6, speed monitoring interface 54 functions to produce one or more speed data words from the input speed signal 14 during each period of the real time clock signal 62 (RTCINT). For the purposes of this embodiment, the speed data word is 8 bits which are coupled in parallel to the interface unit 27 using bits 0 through 7 of the B side. Control of the speed monitoring interface 54 is performed using signal lines CA2 and CB2 coupled thereto from the interface unit 27. In addition, control line CA1 provides a signal to the interface unit 27 indicating that the speed data word register of 54 has exceeded a predetermined value. The operation of control lines CA1, CA2 and CB2 is conducted in response to a set of instructions stored in the PROM devices which may be executed once every period of the real time clock signal 62, for example. This operation is described in greater detail in the U.S. Patent application Ser. No. 771,141 previously referenced to hereinabove.
Interface unit 27 further monitors pushbutton status from the panel 16 over signal lines 110 and 112 and relay contact status from relay logic 1A over signal lines 100 and 104 as previously described above. In addition, interface unit 27 monitors the states of a set of switches 58 using the bits 4, 5, 6 and 7 of its B side. The application of the selection of a particular state of the switches 58 corresponds to a set of one time constant and one gain for use in a proportional plus integral closed-loop speed controller function characterized by the instructions preprogrammed in the PROM devices 19 through 22. This will become more apparent from the description of the program organization found herebelow.
Referring to FIG. 7, bits 4, 5, 6 and 7 of the B side of the interface unit 28 are used to drive the backlighted indicators located within the pushbuttons on panel 16 as previously described. The remaining 12 output bits of interface unit 28 make up the speed control signal data word 55 which is converted into an analog signal 15A with return line 15B using the speed control signal generator 56. A suitable range of the speed control signal 15A for the purposes of driving the torque motor 124 of the control fluid pressure system 7 was found to be 0 to 200 ma. The speed control signal generator 56 is similar to that described in U.S. Patent application Ser. No. 771,141, supra.
The program execution failure detect circuit 66 is controlled by the control lines CA2 and CB2 from the interface unit 28. CA2 and CB2 under operation of instructional code found in the PROMs 19 through 22 maintain a periodic triggering of two monostables correspondingly associated therewith. The monostables are enabled by a power supply malfunction detection circuit. Should either or both outputs of the two monostables go to a false state, signal line 67 will de-energize the DCS relay of the relay logic 1A. This circuitry is also similar to that described in U.S. Patent application Ser. No. 771,141.
The interface unit 26 of FIG. 8 is used to effect the control of the information entered into display windows DP1 and DP2 of the operator's panel 16 as previously described above. Also, interface unit 25 of FIG. 9 monitors the pushbutton switches of the operator's panel 16 using signal lines 122, 124, 126 and 128 and drives the backlighted indicators of the pushbuttons using signal lines 130, 132, 134, 136 and 138 as described above in connection with FIG. 5.
2. PROGRAM ORGANIZATION AND OPERATION
As has been described hereinabove in connection with FIG. 1, a number of read-only-memories are permanently pre-programmed with sets of digital instructions and data words in an addressable order for characterizing the operation of the speed control system depicted by FIG. 1. For the purpose of this embodiment, the instruction sets were developed using the Motorola M6800 assembly level language which is used herein to provide a greater detail of the invention for a better understanding and appreciation thereof. The address range of each of the PROM devices 19 through 22 are shown in the following table:
In using the Motorola M6800 assembly level language, it was found that approximately 1370 bytes of PROM storage was necessary. The storage arrangement for permanently programming the instruction and data words in the PROM devices used the addressed register locations from F600 through F7FF in PROM 20; FA00 through FB98 in PROM 21; and FE00 through FFBE, and FFFB through FFFF in PROM 22. PROM 19 was not programmed with instructions and data for this embodiment. An additional 48 bytes of the temporary storage device 23 from 0000 to 002F were also designated to store system variables.
A printout of the assembly level language program illustrating the addressable order in which it was preprogrammed into the PROMs 20, 21 and 22 is shown in Appendix B. A PROM burner such as the one manufactured by DATA I/O Corp. Model No. 2136D PROM burner was found suitable for permanently pre-programming the set of instructions and data in the PROM devices. The operation and organization of the programs will be provided in greater detail herebelow.
2.1 FUNCTIONAL FLOWCHART
Referring to the flowcharts of FIG. 10, program processing begins at block 200 where the microprocessor 18 (see FIG. 1) receives the initialization signal 65 from circuit 64. Generally when power to the speed controller 1 is turned on, functional block 201 disables the microprocessor response to the real time clock (RTC) interrupts provided to it from the real time clock generator 60 via interface unit 27 and control lines 33. In block 202, the microprocessor 18 processes an initialization program to set a stack pointer to $007F, clear all registers in the temporary storage device 23 and initialize all the registers of the interface unit 25 through 28. Thereafter, the microprocessor 18 is enabled to respond to RTC interrupts in block 203. The previously described portion of the sets of instructions and data is executed only as governed by the initialization pulse over signal line 65, generally when power is turned on.
The decision block 204 essentially loops about itself until a RTC interrupt occurs. A RTC period of 64 Hz was found suitable for the purposes of this embodiment. Therefore, the portion of the instruction sets of programming following the interrupt loop are executed once every 1/64 second. Functional Block 206 reads the speed measurement data word from the speed monitoring interface 54 and stores it in a temporary storage location in device 23. In addition, the digital inputs of the B side of interface unit 27 (PIAO) are read into the microprocessor and stored in the stack of device 23 using functional block 208. The odd and even periods of the RTC signal 62 are determined by functional block 210 which further decides the processing flow therefrom. During an even period of the RTC signal 62, the functional flow diagrams depicted by FIGS. 11A and 11B are processed. During an odd period thereof, that depicted by FIG. 12 is processed.
Starting with FIG. 11A, functional block 211 calculates a new value of the measured speed during each even period of the RTC according to the following algorithm. The instant value of the measured speed is reduced by 1/16 of its value. The speed measurement data words produced by the speed monitoring interface unit 54 during the preceding two periods of the RTC are added to the reduced measured speed value. The result is the new measured speed value. This method produces an exponentially weighted average of the speed measurement data words produced by the speed monitoring interface 54. In the present embodiment, the calculations may be carried out to 24 bits or 3 bytes of storage in device 23 to maintain a 16 bit accuracy. A 1/4 RPM resolution is thus achieved with a 1/2 second response time to change in the actual speed. If an overflow condition should occur during the calculations of block 211, the program stops all processing activity and waits for the malfunction detection circuitry 66 to time out and deenergize the DCS relay in relay logic 2A.
Accordingly, functional block 212 monitors the depression of PB1 on panel 16. If the PB1 has not been depressed, the appropriate display information is provided to window display DP2 of panel 16 in accordance with the status of the backlighting of PB1 using blocks 213, 214 and 215. Otherwise, the backlighting of the lamp requested by the instant depression of PB1 is accomplished with functional blocks 216, 217 and 218 and the window displayed undating is bypassed during the instant execution period. Decisional block 220 monitors the depression of PB4 in panel 16. If PB4 has not been depressed, the appropriate display information is provided to window display DP1 of panel 16 in accordance with the backlighting of the PB4 using blocks 221, 222 and 224. Functional block 223 accomplishes a display filtering effect by updating the speed measurement display only once every fraction of a second. A 0.5 second display update was found preferable. If PB4 has been depressed, the appropriate lamp in PB4 is backlighted as requested by the instant depression of PB4 using functional blocks 225, 226 and 227.
A ramp interval timer, HN, used as one method for increasing the speed reference value to the speed demand value at the desired acceleration, is incremented in functional block 230. An attempt to energize the DCS relay, shown in FIG. 2, is performed by 232 which is similar to that of the malfunction detection circuit 66 described in greater detail in the referenced U.S. application, Ser. No. 771,141. The energization of the DCS relay is monitored by block 234. If DCS relay is not energized, the flag bit which is used to backlight the GO lamp of PB6 is set false and the flag bit which is used to backlight the HOLD lamp of PB5 is set true and the speed reference (SPR) value is set equal to zero by block 209. The program processing is returned to the wait for interrupt loop at point and the next interrupt execution. If the DCS relay is energized, processing continues at block 240.
Functional blocks 240, 241, 242, 243 and 244 of FIG. 11B identify that a speed error beyond a predetermined value exists and accomplishes the associated action in response thereto. The predetermined speed error value found suitable for this embodiment is 300 RPM. More specifically, block 240 compares the instant SPR value with a value, typically 3400 RPM. If SPR is greater than 3400 RPM, functions 241 through 244 are bypassed and execution continues at block 250. Otherwise, speed error is monitored by 241. If greater than RPM, the following is performed in block 242: the flag for lighting the speed control monitor lamp, L1, is set true, the flags to backlight the lamp for pushbuttons, PB5 and PB6, are set respectively true and false and the speed demand is set equal to the instant speed reference. Otherwise, the speed control monitor lamp, L1, is monitored by 243. If the lamp L1 is illuminated, block 244 sets the flag for illuminating lamp L1 false and the program processing continues at block 246 which will be described herebelow. Else, program processing continues at block 250.
Functional block 250 compares the speed demand (SPD) with the instant speed reference (SPR) and if equal, block 251 sets the flag which backlights the PB6 false and continues execution at 246. IF SPR is not equal to SPD, the functional blocks 250 through 260 are executed to essentially perform the logic for: (a) interrupting the ramping of the speed reference with a HOLD function in response to depression of the HOLD pushbutton PB5 while in the GO mode and backlighting the appropriate pushbutton lamps, PB5 and PB6, and (b) restarting the ramping of the speed reference with a GO function in response to the depression of the GO pushbutton PB6 while in the HOLD mode and backlighting the appropriate pushbutton lamps, PB5 and PB6. If in the HOLD mode, program execution continues at block 246 and if in the GO mode, execution continues at block 262. More specifically, blocks 259 and 260 ensure that a value of the speed demand (SPD) greater than zero has been entered through panel 16 before the GO mode may be executed.
In functional block 262, a calculation shown in equation 2 below is performed to increment the speed reference value to the desired speed demand value at the desired acceleration value. The desired values of speed demand and acceleration being that which has been entered through panel 16 in accordance with equation (1) above will be described in greater detail herebelow. ##EQU2## wherein a = acceleration desired in RPM per minute.
Hn = accumulated count in the ramp interval timer incremental every 1/32 second in block 230 shown in FIG. 11A.
1920 = conversion factor for converting counts based on 1/32 second to counts per minute (i.e. 32 counts/sec. .times. 60 sec./min. = 1920 counts/min.)
Spr.sub.o = starting value of speed reference at time HN = 0.
Also, SPR.sub.o may be set to the instant value of the speed reference and HN may be set to zero every time the acceleration changes sign or magnitude of the ramp interval timer, HN, overflows or when SPR is to be maintained constant, for example. This function is performed by block 246. The program execution continues, after functional block 262, at point in the flowchart.
After performing the ramp reinitialization in functional block 246, the speed reference is monitored in block 270. If the speed reference is ramping to the speed demand, the program is next processed at , else the decrease pushbutton and increase pushbutton, PB2 and PB3, respectively are monitored in blocks 271, 272 and 273. Decisional block 273 protects against the case in which both pushbuttons PB2 and PB3 are depressed concurrently in which event further responsive program processing is aborted to point . If PB3 is depressed, its lamp is backlighted by block 274. If PB2 is depressed, its lamp is backlighted by block 275. A time counter associated with incrementing or decrementing the speed demand and acceleration in window DP2 is incremented or decremented in block 276 in accordance with the time that either pushbutton PB2 or PB3 is depressed. The variable, speed demand or acceleration, to be changed in value is determined by monitoring the lamps in pushbutton PB1 using decisional block 277. The time counter of block 276 is accumulating the number which is to be added to or subtracted from the selected variable in DP2 for each second the pushbutton PB2 or PB3 is depressed. In either case, it must next be determined whether to add to or subtract the accumulation of the time counter displayed in DP2 in accordance with the equation 1 shown hereinabove.
Blocks 280 through 284 check the instant speed demand variable against predetermined high and low limits and add or substract the value of the time counter in 276 respectively thereto or therefrom. If a high limit, for example 3800 RPM, has been reached, the increase lamp will be turned off by block 286. Also, if a low limit, for example 0 RPM, has been reached, the decrease lamp will be turned off by block 288. In either case, the program processing will be unresponsive to the depression of PB2 or PB3, as the case may be, to further change the value of the speed demand should its high limit or low limit be attained.
Blocks 290 through 294 check the instant acceleration variable against predetermined high and low limits and add or substract the value of the time counter in 276 respectively, thereto or therefrom. If a high limit value, for example 1000 RPM per minute, has been reached, the increase lamp will be turned off by block 286 and accordingly, if the low limit, for example 0 RPM per minute, has been reached, the decrease lamp will be turned off by block 288. In either case, the program processing will be unresponsive to the depression of PB2 or PB3, as the case may be, to further change the value of the acceleration should its high or low limit be attained.
When neither pushbutton is found depressed during the instant execution of blocks 271 and 272, processing is continued at point 6 of FIG. 11B where the flags for backlighting the lamps of PB2 and PB3 are set false in 296 and the time counter, incremented by 276, is cleared to zero in block 298. Program processing is then reverted to point 1 of FIG. 10 which is a wait for interrupt loop.
During odd periods of the real time clock, RTC, as determined by the decisional block 210 in FIG. 10, the portion of the program shown in FIG. 12 is executed. In block 300, the status of the ASLR relay is tested. If the ASLR relay is de-energized, no further program processing will be performed, block 209 will be executed and the microprocessor 18 will wait for the next interrupt. If the ASLR relay is energized, an attempt will be made to energize the DCS relay in 302 and if the DCS is not yet energized as determined by decisional block 304, program processing will be branched back to point 1 via block 209. If the DCS is energized, a speed control algorithm will be processed at block 306.
The speed control algorithm implements a proportional plus integral control function whose output, V.sub.j, is best represented by an equation (3) shown below: ##EQU3## where k.sub.p = proportional gain constant.
k.sub.I = integral gain constant which is representative of the integral time constant.
E.sub.j = speed error between the speed reference and speed measured values during the j.sup.th execution of the speed control algorithm which is normally executed 32 times per second.
The set of four SPST switches 58 connected to the A side of interface unit 27 (see FIG. 6) represents a binary code which allows the selection of one of sixteen proportional and integral gain pairs -- (k.sub.p 0, k.sub.I 0),....., (k.sub.p 15, k.sub.I 15) -- which are pre-programmed in the PROM devices and used in the speed control algorithm as shown in equation (3) above. Internal to the program, the gain constants may be represented as the ratio of two integers. For example, the denominator, k.sub.pd, of the proportional gain is fixed while the numerator is, k.sub.pn, of the integral gain is fixed, while the denominator, k.sub.Id, is selected by the binary switch 58. Typical examples of proportional gains and integral time constants found suitable for the present embodiment are shown in the table below:
The result, V.sub.j, of equation (3) is representative of the valve position update value converted to the speed control signal 15A and 15B by the speed control signal generators 56 as shown in FIG. 7.
The value, V.sub.j, is conditioned and transferred to the converter of 56 by the instructional block 308. The value of V.sub.j is limited to positive numbers any result which is negative is set equal to zero prior to being transferred to converter 56.
2.2 SUBROUTINES
The program functionally described above includes both a main section and a number of subroutines disposed therethrough. The subroutines rendered a reduction in the amount of redundant programming substantially. The first of the subroutines are designated MAD1 and MAD2 which perform the operation represented by the equation (4) below:
subroutines MAD1 and MAD2 divide a 16 bit positive integer, X, by a 16 bit positive integer, Y, and multiply the quotient by a 16 bit positive integer, Z. The result, R, is a signed 32 bit number having a 16 bit integer part and a 16 bit fraction part. The sign of the result is positive if the most significant bit of memory location designated as TEMP1 in device 23 is zero. Otherwise, the result is negative.
Input: (MAD1) The addresses of Y and Z are stored immediately after the subroutine call as can be seen in the printouts of the program in Appendix B.
Instructional calling sequence:
Jsr mad1
address of Y
address of Z
The address of X must be loaded into the index register of microprocessor 18 prior to the subroutine call.
(MAD2) The addresses of X and Z are stored after the subroutine call and the address of Y is loaded into the index register.
Instructional calling sequence:
Jsr mad2
address of X
address of Z
Output: The signed 32 bit result is stored in 4 consecutive bytes of memory starting at a location designated as SCPDR in device 23. The integer part of the result is loaded into accumulators A (most significant byte) and B of microprocessor 18. If an overflow occurs the largest positive (or negative) number is returned as the result. The content of the index register is preserved.
Memory Used: 214 bytes of program memory and 11 bytes of temporary storage including the four byte result. Additional memory is also required for the input integers X, Y, and Z and the sign flag at TEMP1 in device 23.
Execution Time: Execution time is a function of the values of X, Y, Z, and TEMP1. The worst case time is less than 5200 clock cycles and the typical execution time is 4160 clock cycles of the system clock 60.
Another subroutine, BCD, converts a 16 bit positive binary integer into a 4 digit BCD number and sends the result to one of the two panel displays, DP1 and DP2.
Input: The address of the 16 bit integer must be loaded into the index register prior to the subroutine call. If the result is to be sent to the speed reference/measured speed display, a hexadecimal E8 must be stored in a memory location designated as TEMP2 in device 23. If the result is to be sent to the speed demand/acceleration display, B8 must be stored in TEMP2.
Output: The four BCD digits are sent to the appropriate display, DP1 or DP2, and are stored in memory locations designated as BCDH (most significant digits) and BCDL in device 23. If an overflow occurs a hexidecimal 9FFF is sent to the display, blanking the last three digits. The content of the index register is preserved, but the contents of the two accumulators of microprocessor 18 are destroyed.
Memory Used: 54 bytes of program storage and 3 bytes of RAM storage. Additional memory is required for the peripheral interface adapter (PIA) used as the output port for the decimal displays.
Execution Time: Execution time is a function of the value of the number to be converted. If the sum of the digits in the result is N, then the execution time is [676 + 22N] clock cycles of the system clock 60.
Yet another subroutine, DADD, adds a 16 bit word in memory to the 16 bit word contained in accumulators A (most significant byte) and B of the microprocessor 18 and stores the result in temporary storage device 23.
Input: The address of the word to be added to A and B must be loaded into the index register of microprocessor 18.
Output: The result of the summation is in accumulators A and B and the memory addressed by the index register. If an overflow occurs A and B contain the largest positive (7FFF) or smallest negative (8000) number. The contents of the index register are preserved.
Memory Used: 22 bytes of program storage plus 2 bytes of temporary memory for the result.
Execution Time: 31 clock cycles of the system clock 60 if no overflow occurs, 39 clock cycles if negative overflow occurs, and 43 clock cycles if positive overflow occurs.
Still another subroutine, LIGHT, turns the front panel 16 HOLD, GO, INCREASE, DECREASE or SPEED CONTROL MONITOR lights on or off according to the contents of accumulators A and B of microprocessor 18.
Input: Accumulator A is loaded with a "1" at each bit position corresponding to the light that is to be turned on. Accumulator B is loaded with a "0" at each bit position corresponding to the light that is to be turned off.
Output: The lights are turned on or off as described above. If an attempt is made to turn a light on and off during the same subroutine call, the off condition will dominate. The contents of the accumulators are destroyed.
Memory Used: 12 bytes of program storage, 1 byte of temporary storage (TEMP2), and the memory required by PIA-3 (used to control the lamp drivers).
Execution Time: 21 clock cycles of the system clock 60.
A final subroutine, RMPST, transfers the current speed reference value (SPR) to the initial speed reference value (SPRO) and clears the 16 bit time counter (HN) in accordance with the functional block 246 of FIG. 11B.
Input: None.
Output: The contents of accumulators A and B of microprocessor 18 are destroyed.
Memory Used: 15 bytes of program storage plus 6 bytes of temporary storage containing SPR, SPRO, and HN.
Executtion Time: 29 clock cycles of system clock 60.
2.3 PROGRAM ORGANIZATION
An assembled listing of the programmed instructions for performing the functions of the flowcharts depicted in FIGS. 10, 11A, 11B and 12 is found in Appendix B. These instructions and data have been permanently preprogrammed in the PROM devices 20, 21 and 22 in accordance with speed control system characterization of the present embodiment. The organization of the instructions and data as programmed in the PROM devices is best presented in the form of PROM Maps which are shown below:
To more fully understand the program listing of Appendix B, a dictionary of labels and symbols is presented in Appendix A to be reference during the perusal of the program listing of Appendix B.
3. TYPICAL OPERATION OF THE SPEED CONTROL SYSTEM
The typical operation of the speed control system embodiment described in connection with FIG. 1 herein follows. The hydraulic fluid used for operating the valve servomotors 6 is brought to a pressure above the operational level and the ASL becomes true to energize the ASLR relay of relay logic 2A. The PROM devices 20, 21 and 22 are permanently pre-programmed with a plurality of sets of instructions and data words and are inserted into their corresponding locations in the speed controller 1. Power is turned on and the initialization pulse is conducted to the microprocessor 18 which in turn, executes the intialization portion of the programmed instructions and data contained in the PROM devices. After initialization, a wait for RTC interrupt loop is processed until a RTC interrupt occurs. Thereafter, the remaining portion of programming is executed once every 1/64 second at the occurrence of a RTC interrupt.
Two subportions of the remaining program are alternately executed during respective alternate odd and even RTC periods. That subportion associated primarily with panel operation is executed during the even periods of the RTC and that subportion associated primarily with the speed control functions is executed during the odd periods of the RTC, for example.
During the initial operation of the speed controller 1 prior to any panel commands, the status of the turbine system 2 will be established, the DCS relay will be energized, the operator's panel will be updated and the speed measurement value will be calculated. Also during this initial period a speed control signal 15A and 15B having a value substantially close to ground potential will be generated by unit 56. The plant operator may enter a speed demand and acceleration value using the window display, DP2, and pushbuttons PB1, PB2 and PB3 of panel 16. The speed reference may be accelerated to the entered speed demand value at the entered acceleration value upon depressing the GO pushbutton PB6. The speed of the turbine 2 will be controlled to track the speed reference in accordance with the proportional plus integral closed-loop control function programmed in the PROM devices and executed by the microprocessor 18 utilizing the valve servomotors 6 to admit steam from the source 4 to the turbine 3. The values of the reference or measured speed may be monitored through display window DP1 as selected by the state of pushbutton PB4. The speed reference acceleration may be inhibited at any time by depressing the HOLD pushbutton PB5. All pushbuttons are backlighted during the activation of their function by the microprocessor 18. The speed reference acceleration may be restarted by again depressing the GO pushbutton PB6. The speed reference may be ramped to a number of preselected speed demand values at various accelerations until a final turbine speed is achieved.
If a malfunction in speed controller operation should occur, the DCS relay will de-energize due to the loss of signal 67 which, in turn, will cause the valve servomotors 6 to close by zeroing the signal to the torque motor 124 in the control fluid pressure system 7. Control of the valve servomotors 6 may be performed manually by transferring modulation of fluid pressure signal 7A to the manual cup valve assembly 112 of system 7.
Claims
We claim:
1. A microprocessor-based speed control system energized by an electrical power source for controlling the speed of a steam turbine over a wide speed range from turning gear to substantially synchronous speed by controlling the steam admission thereto from a steam supply source using a hydraulically operated servomotor throttle valve, said system comprising: a plurality of read-only-memories permanently preprogrammed with sets of digital instructions and data words in an addressable order for characterizing the speed control operation of the control system; means for generating a system clock signal; a microprocessor governed by the system clock signal to process the sets of instructions and data words of the programmed read-only-memories synchronous to the system clock signal; means for temporarily storing a plurality of data words resulting from the processing operations of the microprocessor; means responsive to electrical power turn-on to generate an initialization signal to said microprocessor, said microprocessor being responsive to said initialization signal to initialize the status of the microprocessor-based speed controller to a predetermined initial state by processing an initialization set of said sets of digital instruction and data words of the preprogrammed read-only-memories; a real time clock for generating interrupts to said microprocessor, said microprocessor being responsive to said interrupts, only after processing said initialization set of digital words, to segregate its central processing activities into processing time intervals; means for generating a signal representative of actual turbine speed; first means, coupled to the microprocessor and functionally operative in cooperation therewith, for converting the signal representative of actual turbine speed to at least one speed measurement data word corresponding to each generated interrupted as governed by the processing of a first set of instructions and data words by the microprocessor for use thereby; said microprocessor being operative to process a second set of said sets of instruction and data words to calculate a new value of measured turbine speed during each processing time interval in a first set of said segregated processing time intervals based on a function of a present value of measured turbine speed and the values of a predetermined number of speed measurement data words, both corresponding concomittantly with the processing time interval during which the new speed value is being calculated; said microprocessor being further operative to process a third set of said sets of instruction and data words to reduce the error between each new value of measured turbine speed and a value of speed reference substantially concurrent therewith over said wide speed range by generating a control data word which is based on a real time function of said substantially concurrent measured and reference values of turbine speed, said third set of instructions being processed during each processing time interval in a second set of said segregated processing time intervals; second means, coupled to the microprocessor and functionally operative in cooperation therewith, for converting said control data word generated by the microprocessor to a speed control signal as governed by the processing of a fourth set of instructions and data words by the microprocessor; third means governed by the speed control signal to modulate the pressure of a hydraulic fluid signal which is coupled to the servomotor throttle valve for controlling the position thereof; and a control panel, coupled to the microprocessor and functionally operative in cooperation therewith, for entering data thereto and displaying data therefrom and selecting at least one of a plurality of predetermined speed control operating modes of the speed control system, said microprocessor being responsive to said panel mode selection, data entries and data displays in accordance with the processing of a fifth set of instructions and data words thereby.
2. The system in accordance with claim 1; wherein the real time clock signal governs the processing of one portion of the sets of instructions and data words by the microprocessor.
3. The system in accordance with claim 2 wherein the one portion of the sets of instructions and data words is divided into a first subportion comprising the first, second and fifth sets and a second subportion comprising the first, third and fourth sets, said first and second subportions being processed by the microprocessor during respective alternate periods of the real time clock signal.
4. The system in accordance with claim 1 further including: means for detecting a malfunction in the microprocessor instruction processing operation and generating a malfunction signal in response thereto; means for detecting a turbine disabling condition and generating a trip signal in response thereto; and means, disposed between the second means and the control pressure monitoring means, for effecting a closed position of the servomotor throttle valve in response to at least one of the malfunction and trip signals.
5. The system in accordance with claim 1 wherein the reduction of the error between the substantially concurrent speed measurement data word value and the speed reference value is performed by the microprocessor in accordance with a control function having a selected gain and time constant associated therewith.
6. The system in accordance with claim 5 further including a set of switches, coupled to the microprocessor, for supplying a digital code thereto as indicated by the state thereof, said microprocessor being responsive to the digital code to select a gain and a time constant data word from a table of gains and time constant data words preprogrammed in one of the plurality of programmed read-only-memories in accordance with the processing of the third set of instructions.
7. The system in accordance with claim 1 wherein a speed demand value and an acceleration value are entered, at times, from the panel to the microprocessor in accordance with the fifth set of instructions and data words processed by the microprocessor, the speed reference having the entered speed demand value as a final value being ramped thereto at the entered acceleration value governed by the selected panel operating mode; and wherein further the change in speed demand and acceleration value when entered through the panel, is incrementally performed by the microprocessor based on a function of the time during which the change is commanded by the panel.
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