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BACKGROUND OF THE INVENTION
This invention relates to signal distribution systems, and more
particularly to a system for communicating data for control of individual
loads in a system.
In commercial buildings or other facilities, lighting, heating,
ventilating, air-conditioning and other loads can be controlled according
to requirements determined by computer so as to optimize energy usage. A
significantly greater overall reduction in energy usage may thereby be
achieved, provided that control can be extended, individually, to a large
number of separate loads so as to achieve a much finer control mesh than
provided by present control systems. In general, the larger the building,
the greater the potential for energy savings. Moreover, computer
determination of optimum load controls is important if it is desired to
eliminate the need to have these load controls manipulated manually
several times each day at a plurality of remote locations.
Control signals generated by a microcomputer may be distributed to each
switched fixture load in the system by transmission through the power
distribution circuits (which are typically A.C.) in the facility or, in
the alternative, through a communication circuit within the facility, on a
frequency modulated carrier. If necessary, a separate microcomputer may be
employed for each of the lighting, heating, ventilating, air-conditioning
and other systems in the building. The microcomputer may be easily
programmed to the requirements of each separate system of fixtures in the
building, and provides an economical means of storing, in semiconductor
memory, information on desired states of a large number of individually
switched devices within the system. If several systems are employed in a
single building or other facility, overall control of the systems may be
accomplished by a master microcomputer or by a central process control
computer.
Accordingly, one object of the invention is to provide a method and
apparatus for generating redundant address and function codes for
transmission to a plurality of receiving stations.
Another object is to provide a method and apparatus for transmitting
function data over power distribution or communication circuits to
selected receiving stations.
Another object is to provide a system for transmitting control signals,
generated at any of a plurality of receiving stations, back to a central
control location over power distribution or communication circuits for
purposes of controlling a pre-programmed combination of loads.
SUMMARY OF THE INVENTION
Briefly, in accordance with a preferred embodiment of the invention, a
system for performing, from a central location, a selected one of a
plurality of electrical functions at a selected one of a plurality of
remote locations comprises a central processing unit, encoding means
responsive to the central processing unit for generating a predetermined
digital word, and means coupling each of the remote locations to the
encoding means. Receiver-decoder means are provided at each of the remote
locations, each of the respective receiver-decoder means having its own
unique address code and a common address code unique to each of the remote
locations. Means responsive to each of the receiver-decoder means,
respectively, are also provided for performing the selected one of the
plurality of electrical functions at the selected one of the plurality of
remote locations. Additionally, means are provided at selected ones of the
remote locations for generating control information for transmission back
to the central processing unit in order to control a pre-programmed
combination of loads responsive to that particular control signal.
In accordance with another preferred embodiment of the invention, a method
of performing a selected electrical function at a selected one of a
plurality of remote locations from a central location comprises
redundantly generating a predetermined number of digital words,
transmitting the generated words to each of the remote locations, decoding
each of the transmitted words at each of the remote locations, and
detecting a predetermined address in each of the digital words at each of
the selected remote locations. The selected function is performed at the
selected remote locations when identical digital words having the
predetermined address have appeared at the selected remote location a
predetermined number of times out of the number of times the digital words
have been redundantly generated at the central location. Additionally,
control information generated at any of the remote locations is
transmitted back to the central processing unit for controlling a
pre-programmed combination of loads responsive to that particular control
signal.
BRIEF DESCRIPTION OF THE DRAWINGS
The features of the invention believed to be novel are set forth with
particularity in the appended claims. The invention itself, however, both
as to organization and method of operation, together with further objects
and advantages thereof, may best be understood by reference to the
following description taken in conjunction with the accompanying drawings
in which:
FIG. 1 is a block diagram of a signal distribution system, connected in
accordance with the instant invention, employing single or parallel branch
distribution;
FIG. 2 is a flow chart to supplement the description of operation of the
apparatus shown in FIG. 1;
FIG. 3 is a schematic diagram of a signal distribution system, connected in
accordance with the instant invention, employing hierarchical
distribution;
FIG. 4 is a flow chart to supplement the description of operation of the
apparatus shown in FIG. 3; and
FIG. 5 is a pulse waveform illustration of a typical digital word portion
of a transmitted signal.
DESCRIPTION OF TYPICAL EMBODIMENTS
In FIG. 1, a signal distribution system, constructed in accordance with the
instant invention, is illustrated as comprising a central processor unit
(or CPU) 10, at a central apparatus location 25. CPU 10 may typically
comprise a commercially available microcomputer such as an Intel 8080A. A
control state and digital address store 11 coupled to CPU 10 and typically
comprising a random access solid-state memory such as an Intel 8708,
stores assigned frequency allocations and modulation codes. Similarly, an
interconnect matrix store 12, also coupled to CPU 10 and typically
comprising a random access solid-state memory similar to control state and
digital address store 11, digitally stores, under control of CPU 10,
combinations of control states corresponding to particular remote
receiver-decoder addresses. Those skilled in the art will appreciate that
stores 11 and 12 could be combined into a single store, if desired.
A programmable waveform generator 14, such as a Wavetek Model 154, is
connected to CPU 10 and generates a frequency shift keyed (FSK) carrier
modulated with a digital word of a predetermined number of bits, such as
fourteen, in response to a low-level signal from the CPU. The digital word
consists of address and function data. Selection of the digital word is
made according to signals from the CPU. A typical fourteen bit digital
word is illustrated in FIG. 5. The bit preceding the function code is
always a ONE, to serve as a flag bit that signifies to the receiving
apparatus that a digital word is about to be received and that function
information will follow immediately. The next two bits serve to carry
function information for the load to be controlled. The final twelve bits
constitute address information, designating which load is intended to
receive the function information. CPU 10 causes waveform generator 14 to
repeat the generated word so that the word is transmitted several times
(such as three) in succession, rendering redundant the transmitted address
and function code.
Provision is made for tone-code modulation of programmable waveform
generator 14 by a tone-code generator 13, such as a Frequency Devices,
Inc. Model 510 encoder, when a remote address is generated, thereby
providing for tone-coded as well as digitally-encoded carrier frequencies.
Use of a programmable waveform generator permits assignment of different
frequencies to different branch circuits or to subsystem combinations of
receiver-decoders, thereby reducing the number of different digital
addresses necessary for a given number of receiver-decoders.
Frequency-shifted keyed signals on a high frequency carrier are introduced
onto the power distribution circuit for the facility in which the
apparatus of the instant invention is to be installed, by being coupled
thereto at a junction 15. For transmitting signals on power circuits,
jucntion 15 typically comprises a filter which avoids deleterious
interaction between the power current and the signal; that is, the signal
is confined to the part of the distribution circuit on which the loads are
to be controlled, and low frequency noise originating elsewhere in the
power system is attenuated with respect to the output of programmable
waveform generator 14 (which provides output frequencies at least two
orders of magnitude greater than the power frequency). It will be evident
to those skilled in the art that, in the alternative, a communications
line may be employed to distribute the signal through the facility and, in
such case, junction 15 comprises a directional coupler.
A second junction 16, comprising a filter or a directional coupler, passes
signals from junction 15 to receiving apparatus at remote locations within
the facility in which the apparatus is installed. In addition, junction 16
passes signals originating from apparatus at remote locations to a decoder
18 which decodes the tone-encoded command codes received from
remotely-located transmitters by demodulating the signals, and applies the
decoded information to CPU 10, where the point of origin is identified.
The CPU then interrupts its normal sequence long enough to carry out the
received control command in accordance with information stored in
interconnect matrix store 12 utilizing address signals stored in control
state and digital address store 11.
Digital signals originated within central apparatus 25 and supplied through
junction 16 are received by receiver-decoders 20 at various remote
locations 22 within the facility. Each of these receiver-decoders may
typically be of the type disclosed and claimed in Eichelberger and Garratt
application Ser. No. 748,932, filed Dec. 9, 1976 now U.S. Pat. No.
4,091,361, issued May 23, 1978, and assigned to the instant assignee. When
the digital signal is received at the intended receiver-decoder a
predetermined number of times (e.g. two) out of the number of times it is
consecutively generated (e.g. three), control signals are produced by the
receiver-decoder to actuate the associated controlled apparatus 21 in
accordance with the functions assigned. By transmitting control signals in
repetitive fashion, the redundant and cyclic nature of the transmissions
makes it safe to assume that the individual load points will eventually
achieve the states assigned to them at memory store 11, allowing readout
of the overall state of the system from the central store rather than
having to transmit acknowledging signals back from each control point.
A plurality of transmitters 23 each comprises a tone-encoded signal
generator to which a simple control code is added; that is, the
identification of each transmitter 23 is preset so as to generate the same
tone-encoded address signal each time the transmitter is actuated, while a
selected one of several tone-encoded control signals, depending upon the
control function desired by a person at one of a plurality of remote
locations 22, is produced immediately after the identification code in
accordance with the keys of a control keyboard 24 depressed manually at
the remote location. This keyboard (or, in the alternative, sensing and
encoding means responsive to the condition of controlled apparatus 21)
actuates transmitter 23 coupled thereto to furnish to CPU 10 a control
code corresponding to the new, selected condition of controlled apparatus
21 at the appropriate one of remote locations 22 (although condition of
controlled apparatus 21 at any other remote location may also be modified
by the same transmitter simply by pre-programming such operation into the
system). A modified telephone-type key pad may, if desired, suffice as
keyboard 24 for each of transmitters 23.
To recapitulate operation, an FSK modulated signal generated by
programmable waveform generator 14 in response to signals from CPU 10 is
injected through junction 15 and 16 in sequence, onto distribution
circuits in the facility in which the invention is installed, to
ultimately reach receiver-decoders 20 wherein the signals appropriate to
an individual receiver are received and decoded. Digital signals from
remote transmitters 23, for individual adjustment of controlled apparatus
21, are routed through junction 16 to decoder 18, where the information
representing point of origin and command code is decoded. This information
is supplied to the CPU, interrupting its normal sequence long enough to
carry out the control command received from any one of transmitters 23.
The action in response to this control command is carried out by selecting
a designated control state from interconnect matrix store 12 and combining
it with an appropriate address or addresses from control state and digital
address store 11. The ensuing command from central apparatus 25 is
transmitted to the selected individual receiver-decoders 20 by an
appropriately encoded signal.
The information retrieved at any given time from control state and digital
address store 11 essentially constitutes a control state map. A number of
such maps are stored for use therein, and selected maps are put into
effect by CPU 10 at appropriate times. For the circuit configuration
illustrated in FIG. 1, a given set of maps is associated with separate
carrier frequencies used for individual branch circuits (i.e., remote
locations). In normal operation, these maps are put into effect by CPU 10
as determined by an executive program (designated "EXEC" for flow chart
nomenclature) and may be responsive to time of day or other information.
As shown by the flow chart of FIG. 2, the sequence of reading out
information appropriate to individual control states, and transmitting
appropriate signal codes to the individual receiver-decoders, is a
sequential iterative process. The format of the digital signal employed,
as illustrated in FIG. 5, is such that many individual control states can
be put into effect using a single carrier frequency.
The normal sequence of control, as indicated in FIG. 2 for the apparatus of
FIG. 1, is subject to an interrupt mode initiated by an interrupt signal
transmitted from any one of remote transmitting stations 23. This tone
encoded signal is converted by decoder 18 into binary coded digital format
and applied to the interrupt line of CPU 10. Origin of the interrupt
signal is indicated by the address code supplied at transmitter 23.
Receipt of this interrupt signal causes CPU 10 to interrupt interrogation
of control state and digital address store 11 and interrogate interconnect
matrix store 12 where signal codes corresponding to the desired states
specified by the interrupt signal are stored. These codes are then
transmitted to the particular receiver-decoders 20 whose states are to be
modified in accord with the interrupt signal. This is a sequential
iterative process, at the end of which a check is made for specific
instructions residing in the executive program. These instructions may
comprise, for example, an instruction for CPU 10 to proceed with a
complementary map from control state and digital address store 11 for the
purpose of placing a time delay or hold into effect for those loads 21
whose states have been adjusted by the interrupt signal.
FIG. 3 illustrates a typical hierarchical system in which signals furnished
from central apparatus 25, such as shown in greater detail in FIG. 1, are
distributed to remote subsystems 30, one of which is shown in detail. Each
remote subsystem 30 includes an individual microcomputer 31 which
establishes a normal sequence of operation within its individual remote
subsystem. Specifically, signals from central apparatus 25, transmitted
over either power or communication circuits, are supplied by microcomputer
31 in each remote subsystem to predetermined ones of a plurality of
receiver-decoders 32 having controlled apparatus 33 connected thereto
within the respective remote subsystem. Those skilled in the art will
recognize that since each remote subsystem includes an individual
microcomputer, the signals transmitted from central apparatus 25 can be
limited to tone codes or simple combinations of tone codes and digital
codes. Receiver-decoders 32 are typically of the type designated
receiver-decoder 20 in FIG. 1. Respective sensing and encoding means 34
may be mechanically or electrically coupled to predetermined ones of
controlled apparatus 33, respectively, for supplying signals to
microcomputer 31 in accordance with the sensed condition of the controlled
apparatus coupled thereto. However, even in absence of sensing and
encoding means 34, microcomputer 31 can make available from the stores
information concerning the assumed state of any of controlled apparatus
33. Thus output signals representing the overall state of the subsystem
(e.g. real and reactive power, peak load versus time, etc.), or a portion
thereof, may be supplied to a transmitter 35 which is similar to
transmitter 23 of FIG. 1 (i.e., a tone-encoded signal generator to which a
simple control code is added). More specifically, the identification of
transmitter 35 in any given subsystem 30 is preset so as to generate the
same tone-encoded address signal unique to that transmitter each time the
transmitter is actuated either by a manually-operated keyboard 36 or by
microcomputer 31, and a selected one of a plurality of tone-encoded
control signals, depending upon the actuated keys of the keyboard or the
sensed condition of the controlled apparatus is produced after the
identification code.
Microcomputer 31 therefore produces a specific condition code depending
upon conditions within the given subsystem 30. This condition code is
transmitted back to central apparatus 25 wherein it is accepted and stored
by the CPU in an auxiliary store for later use as necessary. Those skilled
in the art will appreciate that, while only three receiver-decoders 32 are
illustrated in subsystem 30, a larger number may be employed as necessary
to completely automate operation of the remote subsystem.
Microcomputer 31 in each remote subsystem 30 receives signals from central
apparatus 25 and passes them on to the receiver-decoders within the
subsystem. Only the addressed receiver-decoder responds to the signal from
central apparatus 25. However, the receiver-decoders within any given
subsystem may be assigned a common address and be controlled by
microcomputer 31 to perform their functions in a predetermined sequence,
thereby obviating any need for a completely different digital word to be
transmitted by central apparatus 25 each time it is necessary to alter the
state of any controlled apparatus 33 within any remote subsystem 30. A
typical microcomputer 31 for carrying out the necessary functions may
comprise an Intel 8080A microprocessor and an Intel 8708 control state and
digital address store.
The flow chart of FIG. 4 illustrates several possible modes of operation
for the apparatus of FIG. 3, depending upon the communications protocol
established. The normal mode of operation is similar to that of the branch
circuit system shown in FIG. 1. Various interrupt modes are possible,
depending upon the source of the interrupt signal. This may originate at
central apparatus 25 and be transmitted to a remote subsystem 30 in the
form of a tone-encoded signal utilizing tone code generator 13 in
conjunction with programmable waveform generator 14 shown in FIG. 1. In
this instance, the central apparatus initiates the signal in order to
modify the process normally carried out by the specific remote subsystem
addressed. Modification maps for the subsystem are stored at the subsystem
microcomputer 31.
An alternative mode of operation for the hierarchical system shown in FIG.
3 involves direct communication between individual subsystems 30, using
transmitter 35. Microcomputer 31 of a first subsystem 30 initiates the
signal in order to provide a specific input to a second subsystem 30
corresponding to changes in state of the first subsystem. An example of
this type of operation is use of changes in state of a lighting subsystem
as a control input to modify the state of a heating, ventilating and air
conditioning subsystem, or the use of modification maps for the lighting
subsystem in order to reduce the peak requirement on the heating,
ventilating and air conditioning subsystem. Use of this type of
anticipatory signal in subsystem control is a feature of the distributed
control system described herein which is not feasible to accomplish with
prior control systems.
Reviewing the flow chart of FIG. 4, if an interrupt signal is not received
by microcomputer 31, the control state and digitial address stores
associated therewith are read out to generate signal codes corresponding
to desired states for a given map. The microcomputer produces output
voltages which select codes and frequency corresponding to the given map,
and generates FSK carrier signals for transmission to receiver-decoders 32
as indicated in the given map. If there are further inputs, this process
repeats itself. If there are no further inputs, microcomputer 31 carries
out the executive program. If an interrupt signal is received,
microcomputer 31 identifies the origin of the interrupt signal and reads
out signal codes corresponding to desired states for the given map. Output
voltages are then supplied by microcomputer 31 to select appropriate codes
and frequency corresponding to particular receiver-decoders 32 according
to the given map. FSK carrier signals are then generated for transmission
to receiver-decoders 32 as called for on the given map. If there are
further interrupt inputs, this process is repeated. However, if there are
no further interrupt inputs, the microcomputer checks for specific
instructions in the executive program. If there are such instructions,
they are carried out and the system returns to its normal mode of
operation. If there are no specific instructions in the executive program,
the system is likewise returned to normal operation.
In FIG. 5, a typical code signal transmitted by central apparatus 25 of
FIGS. 1 and 2 is illustrated with respect to 120 Hz clock pulses
conveniently derived from the 60 Hz A.C. power line by conventional
techniques. Those skilled in the art will appreciate that higher clock
frequencies may, alternatively, be derived by the 60 Hz A.C. line, though
with some diminution in noise immunity. If communication circuits are
used, the preferable signalling rate is considerably higher than 120 Hz.
In FIG. 5, the initial portion of the digital word comprises a
predetermined number of logic ZEROs, which preferably corresponds to the
number of bits in the remote location address, followed by a flag bit (a
ONE) to specify start of the function information. Although the function
code in the illustrated word is shown comprising two bits, those skilled
in the art will appreciate that as many bits as needed to carry out the
desired functions may be added to the word, as long as the apparatus
employed in the system has the capacity to accommodate the number of bits
employed. The function code is followed by the remote location address,
which ensures that the intended functions are carried out by the desired
remote receiver-decoders, and only those receiver-decoders. In the case of
a hierarchical system, a single, tone-encoded remote location address may
be employed for all the receiver-decoders in any single remote subsystem
30, with the function code including, in a predetermined sequence, the
specific functions to be carried out by each controlled apparatus 33 in
subsystem 30. In such case, the remote subsystem microcomputer 31 controls
the sequence in which receiver-decoders 32 actuate their respective
controlled apparatus 33 to carry out the specified functions.
The foregoing describes a method and apparatus for generating redundant
address and function codes for transmission to a plurality of receiving
stations, with function data being provided over power distribution or
communication circuits to selected receiving stations. The system also
provides for transmitting control signals, generated at any of a plurality
of receiving stations, back to a central control location over the power
distribution or communication circuits for purposes of controlling a
pre-programmed combination of loads.
While only certain preferred features of the invention have been shown by
way of illustration, many modifications and changes will occur to those
skilled in the art. It is, therefore, to be understood that the appended
claims are intended to cover all such modifications and changes as fall
within the true spirit of the invention.
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