US3532996A - Signal processing system - Google Patents

Description

INVENTORS ATTORNEY J. L. WALLACE, JR.. A

SIGNAL PROCESSING SYSTEM Filed Dec. 25, 1966 J. Z/GHTSEY lava/1c: J42 DAVID J -M,4r.sa1v BY Oct. 6, 1970 3,532,996 SIGNAL PROCESSING SYSTEM Jacob L. Wallace, Jr., Springfield, and David J. Matson,

Vienna, Va., assignors to The Susquehanna Corporation, Fairfax County, Va., a corporation of Delaware Filed Dec. 23, 1966, Ser. No. 604,411 Int. Cl. H03k 17/16 US. Cl. 328-154 4 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a system for processing signals, and more particularly to a system for processing desired signals while eliminating or reducing the elfect of undesired or false signals.

During the operation of apparatus it is often desirable to know of the occurrence of stoppages, outages, malfunctions, and the like, including the duration the apparatus may be inoperative or operating substantially for such causes. Information of this type is valuable in ascertaining productivity of apparatus, frequency of malfunctions, total outage time, to name a few examples. Such information from a number of machines in a manufacturing environment can provide industrial engineers with information regarding efficiencies, quality control and other statistics which prove necessary to study or evaluate the equipment or factory in which the machines are housed. An example is in the textile industry where loom operation is closely monitored to obtain data which can be helpful in determining efficiency of a machine or manufacturing plant and even matters such as pay of employees where such pay is based on the total time that a particular loom is in operation. Typically, the collected data indicates whether a particular loom is running or stopped; and if it is stopped, the reason why, e.g., warp stoppage, filling stoppage, or a loom stoppage, the latter as may be caused by an actual shutting down of the loom or a malfunction in the looms mechanical apparatus.

Switches are normally provided on the loom so that if a loom stoppage, warp stoppage, or filling stoppage occurs and one or more of the switches are actuated, a signal is provided to afford a remote indication of such occurrences. However, it has been found that in factories or mills Where there is a concentration of mechanical equipment including large motors and switchgear, accompanied by the generation of electromagnetic interference or large static charges, false signals can occur and cause false indications of loom-operating condition.

Accordingly, it is an object of the present invention to provide an improved system which processes signals reflecting true machine operating condition yet rejects extraneous signals or reduces their effect upon signal utilizing equipment.

A further object of the invention is to provide such a system which is responsive to signals received from a sensing point and which processes such signals in a normal manner yet prevents undesired signals received at the system from being passed to the signal utilizing equipment.

Another object of the present invention is to provide an improved signal processing system which permits signals United States Patent indicative of machine-operating condition to be applied "ice to utilizing equipment but which controls the number of such signals applied to said utilizing equipment Where a previous signal is being processed.

Other objects and advantages will become apparent from a reading of the following specification in conjunction with the sole accompanying drawing showing 21 diagram of the present invention in schematic and logic orm.

Briefly, the signal processing system is constructed of a plurality of channels, each channel monitoring a machine or apparatus function. Signals indicative of normal operation are received by each channel and passed to utilizing equipment. When a predetermined operating condition occurs, such as a stoppage or outage, the change in signal received at the related channel is detected and then applied to the utilizing equipment. When undesired signals, which can create a false indication of the operating condition or change in condition of the machine or apparatus, are received in the channels, these undesired signals are rejected or their effect upon the utilizing equipment is minimized.

The present invention will be described with respect to a loom-monitoring operation, although it is to be understood that the present invention is useful to process signals reflecting the operating condition of other types of machines and apparatus. As shown in the figure an AC supply is applied to one side of a switching arrangement comprising three switches 10, 12, and 14. These switches are normally provided on the loom to operate automatically in response to a loom stoppage by the opening of switch 10, a Warp stoppage by the opening of switch 12, and a filling stoppage by the opening of switch 14. These switches can also be manually opened, if desired, to reflect the above three conditions. In the loom operation whenever a warp stoppage or a filling stoppage occurs, it is usually desirable to have a complete loom stoppage. Therefore as schematically shown, switch 10 opens to indicate loom stoppage any time that switch 12 or switch 14 opens. Accordingly, when switches 10 and 12 are open a warp stoppage indication will be received at utilizing apparatus, and when switches 10 and 14 are open, a filling stoppage indication will be registered. The loom may also stop for causes other than a warp or filling stoppage, and for this reason switch 10 is shown as being able to operate independently. When switch 10 alone is opened, a loom stoppage indication for reasons other than a warp stoppage or filling stoppage is registered at the utilizing apparatus.

Three separate channels A, B, and C are provided for processing the signals received through the switches 10, 12, and 14. Each channel is connected to its associated switch by lines 16, 18, and 20, respectively. Normally, the processing circuitry is positioned remote from the switches and the lines 16, 18, and 20 will be carried by a common cable 22 which can be from several feet to even several hundred feet in length.

The three channels A, B, and C each contain a diode 24, 26, and 28 respectively connected on one side to the lines 16, 18, and 20. Diode 24 is poled in a reverse manner from diodes 26 and 28. Diode 24 is connected on its other side to the junction between resistor 30 and capacitor 32 which form an RC circuit. Resistor 30 has its other terminal connected to a source of positive voltage while the other terminal of capacitor 32 is grounded. The common point of resistor 30 and capacitor 32 is applied to one input of NOR gate 34. The remaining input of this NOR gate is grounded.

In channel B, the cathode side of diode 26 is connected to an RC circuit formed of capacitor 36 and resistor 38. The diode 26 and this RC circuit is also connected to one input of NOR gate 40. In channel C, diode 28 is also connected to an RC circuit formed of capacitor 42 and resistor 44, and is also connected to a third NOR gate 46. The output of NOR gates '40 and 46 are connected respectively to the set inputs of flip-flops 48 and 50. The output of NOR gate 34 is connected by line 52 to the clear input of both of these flip-flops. The One side of flip-flop 48 is connected to the second input of NOR gate 46 by line 54, and the One side of flip-flop 50 is connected to the second input of NOR gate 40 by line 56.

Line 58 leading from NOR gate 34 and lines 60 and 62 leading respectively from the Zero sides of flip-flops 48 and 50 are applied to utilizing apparatus. Example of such utilizing apparatus can be lamps such as represented here by lamps 64, 66 and 68, or by alarms. Another form of indicator can be a chart recorder in which one type of signal is recorded by the stylus when a sensing swtich is closed and another type of signal is recorded by the stylus when the sensing switch is opened. Still another form of utilizing apparatus is the central type such as a computer where data from a number of machines, such as looms, is transmitted. In this latter type of apparatus the signals on lines 58, 60, and 62 would be first applied to an encoder which would convert these signals to a digital pulse train which is fed to the computer continually or on demand. These forms of utilizing apparatus are state-of-the-art and need not be further elaborated upon in the present description.

Assuming that the loom is operating normally and that switches 10, 12 and 14 are closed, the operation of the system shown in the figure will be described. In channel A, diode 24 rectifies the AC supply being applied to switch and line 16 so that only the negative half cycles are passed. Capacitor 32 acquires a negative charge. With a ground, or less than ground (negative) potential at both inputs to NOR gate 34, the output of this NOR gate is positive. This positive output is applied to line 58 and also holds flip-flop 48 and 50 clear by way of line 52.

In channels B and C, the AC supply is rectified by diodes 2'6 and 28, respectively, and the capacitors 36 and 42 in the RC circuits each accumulate a positive charge. A positive signal is applied to one input of NOR gate 40 and NOR gate 46. The output of each of these NOR gates is therefore at ground. It should be noted that the second input to each of NOR gates 40 and 46 is at ground because each of the flip-flops 48 and 50 is clear and their One sides are at ground. The Zero outputs are at positive potential as are output lines 60 and 62.

In normal operation when a faulty or substandard condition causes the loom to stop, switch 10 will open, as described previously. The removal of voltage from channel A permits capacitor 32 to discharge. The selection of positive voltage and the values of resistor and capacitor 32 are chosen such that it takes approximately two seconds for this RC circuit to reach a positive voltage which will open NOR gate 34. The output on line 58 then goes from a positive to a ground potential, and this abrupt change in potential can be used to effect an indication at the utilizing apparatus. Assuming that lamps 64, 66, and 68 are initially dark, lamp 64 illuminates. Positive voltage is also removed from the clear side of flip-flops 48 and 50. However, these flip-flops do not change state because the outputs of NOR gates and 46 are unchanged. No change in output signals on lines 60 and 62 occurs. Thus, a change in potential on line 58 only is transmitted out of the transfer system to indicate loom stoppage.

Because the channels B and C are identical in construction, as shown here, only the effect of opening one of the switches 12 or 14 will be described. Assuming that a warp stoppage occurs, switch 12 opens. As mentioned previously when either switch 12 or switch 14 is opened in response to either a warp stoppage or filling stoppage, switch 10 also opens. The effect on channel A caused by the opening of switch 10 is as described in the previous paragraph, and the output voltage on line 58 goes from a positive to a ground level. The appearance of a ground on line 52 removes the positive clamp from the clear sides of flip-flops 48 and 50. These flipflops are now conditioned to change state in response to a positive signal at the outputs of NOR gates 40 and 46.

In channel B with switch 12 open, charging current is removed from capacitor 36 and it begins to discharge through resistor 38. The values of these two components are chosen so that discharge is complete in approximately two seconds. At that time, there are two ground inputs into NOR gate 40 and the output of this NOR gate goes from a ground to a positive level. This plus voltage is applied to the set side of flip-flop 48. With the positive clamping voltage removed from the clear side of this flip-flop, it sets, and the Zero output and line 60 drops from a positive to a ground level.

With the change in signal level present on both lines 58 and 60, as distinguished from a change in condition only on line 58 when only the machine-stop switch was opened, it will be evident to the utilizing apparatus that the loom has been stopped because of a warp stoppage. For example, lamps 64 and 66 can both be illuminated to reflect a warp stoppage. If a filling stoppage occurs and switch 14 and switch 10 open, a change in level is then registered on lines 58 and 62, and this means to the utilizing apparatus that a filling stoppage has occurred. Appropriately, lamps 64 and 68 can be illuminated to show this occurrence. Thus, by monitoring the operation of the machine and using the signal processing system of the present invention, any true stop condition can be detected and passed to desired utilizing apparatus.

When as described above the flip-flop 48 is set, its One side goes positive and via line 54 this positive level is applied to the second input of NOR gate 46. Thus, regardless of what may happen in channel C subsequently, the output of this NOR gate will remain at ground because of always having at least one positive input. The advantage of this arrangement is that only the first cause of an outage is registered. Thus for example, with switch 12 open, a subsequent condition that would cause switch 14 to open is not made evident to the utilizing apparatus. It has been found that often when a machine has been stopped because of a warp stoppage (or filling stoppage), any subsequent switch actuation is usually inadvertent and probably results from the effect of the stoppage. Without knowing whether the second stop would have occurred absent any previous stoppage, it is preferred that no indication be received as provided by the present invention.

In a manufacturing environment having a concen tration of mechanical equipment including such things as large motors, operation of the equipment or motors can readily cause the generation of electromagnetic interference or even large static charges. Where electrical wiring or cabling is used, such as wires 16, 18 and 20, they are susceptible to electrical signals being induced by reason of their proximity to stray fields created by the electromagnetic radiation. These signals can be of a positive or negative character with respect to ground, and be of varying duration and amplitude all dependent upon the effect caused in the cable 22 by the influence of one or more sources of electromagnetic radiation or static charges. In a multiconductor cable these signals are induced in all conductors and normally have the some polarity. The ability of the present invention to reject these false signals or to minimize their effect will now be described.

Assume that the machine is running normally and all three switches are closed as shown in the drawing, and assume also that a negative transient signal is generated in all three lines 16,, 18, and 20 in the cable 22.

In channel A, the effect of this transient is inconsequential because after it passes through diode 24 it can only cause the capacitor 32 to accumulate a slightly more negative charge and no change on NOR gate 34 occurs. In channels B and C the negative transient signal is blocked by diodes 26 and 28, and no changes occur in these two channels. If this transient signal is longer than the time constant of the RC circuits in these two circuits, here being established at two seconds, then the charge on the capacitor 36 or 42 will discharge and the result will be two ground inputs to each of the NOR gates 40 and 46. The output of each NOR gate will go from a ground to a plus voltage level, but this change has no effect upon either flip-flop 48 or 50 because of the positive voltage on line 52 holding these flip-flops in a clear state. Therefore, by virtue of no change in signal occurring on the output lines 58, 60, or 62, the signal processing system has effectively rejected the false negative signal picked up on each of lines 16, 18, and 20.

If the false signal is of a positive value, then channel A is not affected because of the action of diode 24 in blocking the passage of this positive signal. It has been found that normally only a small percent of the false signals induced in the cabling has a duration greater than two seconds. However, in those cases where the duration of the positive signal here under discussion is longer than the predetermined two-second duration, the negative charge on capacitor 32 will discharge and a positive charge will begin to accumulate. With the positive input at NOR gate 34, the output of this NOR gate and line 58 will go from a positive to a ground level. Once the transient signal ends, capacitor 32 will begin to accumulate a negative charge and the output of NOR gate and accordingly line 58 will again rise to a positive level.

In other words, the false-stop indication will persist only so long as the false signal persists beyond a twosecond duration because there has been no switching action performed such as the setting of a flip-fiop or other apparatus. Thus where switch is responsive to a mannal reset when opened due to a true machine stoppage condition, an indication of a brief machine stoppage by a brief illumination of lamp 64 can be readily attributed to a false signal and ignored at the utilizing apparatus.

In channel B the positive false transient signal passes through diode 26 but has no effect on this channel except possibly the creation of a larger charge on capacitor 36. This same insignificant effect is experienced in channel C. No change in the output of NOR gate 40 or 46 is realized, and accordingly no change in the output of flip-flops 48 and 50. Therefore, false positive signals are also rejected by the present invention.

The present system is also capable of discriminating against false signals when one or more of the switches 10, and 12, and 14 are open. Assuming that the machine has stopped, and switch 10 has been opened, output line 58 is at ground which signal condition is being applied to the utilizing apparatus. Here, lamp 64 is lit. Also, the clear inputs to flip-flops 48 and 50 are at ground. If an extraneous negative signal is now generated in each of the lines 16, 18, and 20, the effect on channel A is that the negative signal passes through diode 24. The first input to NOR gate 34 which was at a positive value goes to ground and with two ground inputs, the output of NOR gate 34 goes from a ground to a positive condition. This indicates that the machine is no longer stopped but is again operational. Lamp 64 darkens. However, as discussed above, the change at the output of NOR gate 34 persists only so long as the transient signal persists. As soon as this false signal terminates, the small negative charge which may have accumulated on capacitor 32 is quickly dissipated and NOR gate 34 is once again presented with a positive input and its output goes to ground. Lamp 64 again illuminates. The sequence of events at the indicating circuit is therefore represented by an outage condition followed by a machine-operational condition for a very brief interval and followed again by a machine outage condition. This sequence can normally be attributed to false signals: and can be disregarded at the indicating apparatus.

In channel B, the negative signal is blocked by diode 26. If this negative signal is longer than the two-second timing period of the RC circuit this circuit will discharge and two ground inputs will now be applied in NOR gate 40. The output of this NOR gate goes positive. However, flip-flop 48 cannot be set because of the positive signal from NOR gate 34 being applied by line 52 to hold flipfiop 48 clear. Thus, the output on line 60 remains unchanged. Channel C responds to the negative transient signal in the same manner as channel B. Thus, a negative transient signal has no effect on channels B or C when switch 10 is open due to a machine-stop condition. While an inconsequential change does occur in channel A and thereby cause a false indication via line 58, this change is beneficial in one aspect in that it again affords a positive signal to the clear sides of flip-flops 48 and 50- for the duration of the false signal to prevent their switching in response to the change in outputs at NOR gates 40 and 46.

When switch 10 is open and a. false signal picked up by line 16, 18, and 20 is of positive value, it will not pass diode 24 and channel A. Even if this false positive signal is abnormally long, it is without effect on channel A because capacitor 32 is already positively charged. Thus, the output on line 58 stays at ground to indicate a machine stoppage.

In channels B and C the false positive signal passes through diodes 26 and 28 but has no effect on either channel except tosupplement the charge on capacitors 36 and 42.

Assuming next that switch 12 and switch 10 are open in response to a warp-stoppage, the effect on the signal processing system will be next examined. Since channels B and C are identical the description of operation of the effect of positive and negative transient signals on the three channels will also hold true where switch 14 and switch 10 are opened in response to a filling-stop. Thus, only one description need be provided. In channel A, capacitor 32 is charged to a positive level and the output of NOR gate 34 and accordingly line 58 is at ground. In channel B capacitor 36 has discharged and NOR gate 40 has two ground conditions and its output is positive. Flip-flop 48 has been set and line 60 is now at ground. Lamps 64 and 66 are lit. The One side of flip-flop 48 is now positive and this voltage level is applied by line 54 as a clamp at the input of NOR gate 46 to hold the output of this NOR gate at ground.

In channel A, a negative signal induced in line 16 passes through diode 24 and switches NOR gate 34. The output of this NOR gate and line 58 now go from ground to a positive level causing a change to be reflected at the indicating apparatus. Lamp 64 extinguishes. This same positive signal is applied to the clear side of flipflop 48. However the set side of the flip-flop has a positive holding potential and does not clear. Accordingly, the output on line 60 stays at ground. As soon as the false signal terminates, capacitor 32 begins to charge in a positive direction and the output of NOR gate and line 58 again go to ground. Lamp 64 again illuminates. Thus, at the indicating apparatus only a brief interruption of the machine stoppage condition has been registered. However, since the warp stoppage condition is unchanged and since a machine stoppage always accompanies a warp stoppage (or a fill stoppage) it is obvious at the indicating circuit that a false signal has caused the change and it can be disregarded.

In channel B the false negative signal cannot pass diode 26. Note that capacitor 36 is already discharged and accordingly the duration of this negative signal is not significant. In channel C the negative signal cannot pass diode 28. If longer than the two-second duration, capacitor 42 discharges NOR gate 46 is unaffected, however, because of the positive clamping signal being applied on line 54 from flip-flop 48.

When switches 12 and 10 are open indicating a warp stoppage, and a positive transient signal is induced in lines 16, 18, and 20, the effect on the three channels is as follows. In channel A the positive signal cannot pass diode 24. Even where it is longer than a twosecond duration, it has no effect on channel A because capacitor 32 is already charged to a positive voltage. In channel B the postive signal will pass through diode 26 and accumulate a charge on capacitor 36. This positive charge will cause the output of NOR gate 40 to go to ground, thereby applying a ground to the set side of flip-flop 48. However, this flip-flop is already set and requires a positive voltage on line 52, from NOR gate 34 to clear. However, line 52 remains at ground and flip-flop 48 is unaffected. The output signal on line 60 stays at ground. In channel C the positive charge passes through diode 28 but has no effect further on this channel except possibly to supplement the charge on capacitor 42.

Thus, when switch 10 and either switch 12 or switch 14 are open negative and positive transient signals are effectively rejected in channels B and C while in channel A the effect of such signals is minimized.

The flip-flops 48 and 50 are preferably of set-reset design and are sensitive to voltage levels rather than the leading edges of pulses. As described above, the flip-flops become set by application of a positive level to the set input, provided the positive level is at the same time absent from the clear side. Removal of the positive level does not clear the flip-flop, which can only occur by the application of a positive level to the clear side when the positive level is absent at the set side.

. Although there has been described a preferred embodiment of the invention, it will be apparent to those skilled in the art that many variations and modifications are possible. Accordingly this invention is to be limited only by the scope of the appended claims.

What is claimed is:

1. A system for detecting and processing input signals and desired changes therein to provide output signals to utilizing apparatus and for preventing undesired input signals from adversely affecting said apparatus, said system comprising at least three channels, each of said channels adapted to be responsive to a switch whose position reflects the operating state of apparatus and thereby determines the input signals applied to each channel, each of said channels containing a gate for providing an output whose level is responsive to predetermined signals at the channel input, a flip-flop in each of a plurality of channels and connected to the output of the gate in its channel to be actuated thereby, the output of the gate in one of the channels being applied to the input of the flip-flops in said plurality of channels to control the actuation of each flip-flop, means in each of said plurality of channels for applying the output of the channel flip-flop to the input of the gate in another of said plurality of channels to prevent the actuation of a flip-flop where a flip-flop in one of said plurality of channels has been previously actuated, and unidirectional means and storage means, connected in each channel at the input to the gate, for preventing, in conjunction with said gates and flip-flops, undesired signals of either polarity from affecting adversely the true output signal conditions.

2. A system as claimed in claim 1 wherein said unidirectional means is comprising a diode at the input to each channel to permit the passage of signals of predetermined polarity into each channel.

3. In a signal processing system adapted to receive input signals representative of the operating state of apparatus and to pass to utilizing apparatus output signals in response to said input signals, said system comprising at least three channels, gating means in each channel responsive to said input signals for providing a first output during a first predetermined operating state of said apparatus, as represented by said input signals, and providing a second output in response to a change to a second predetermined operating state of said apparatus, as represented by a change in said input signals, flip-flops in two of said channels, each flip-flop being responsive to the output of the gating means in its respective channel, one output of the flip-flop in each of said two channels being fed back as a clamping input to the gating means in the other of said two channels to prevent a change in said input signals from causing the flip-flop in one of said two channels to change the state of said output signals when the flip-flop in the other of said two channels has first changed the state of its output signals in response to a prior change in said input signal, means connecting the output of the gating means in the remaining channel to an input of each of said flip-flops in the other two channels to control the actuation of said flip-flops, and unidirectional means and storage means, connected in each channel at the input to said gating means, for preventing, in conjunction with said gating means and flip-flops, undesired signals of either polarity from affecting adversely the true output signal conditions.

4. A system as claimed in claim 3 wherein said unidirectional means is a diode at the input to each channel, the polarity of the diodes being arranged to permit only the passage of signals of predetermined polarity into each channel.

References Cited UNITED STATES PATENTS 3,032,664 5/1962 Rowe 307-215 3,027,465 3/1962 Di Lorenzo et a1. 307215 3,104,327 9/1963 Rowe 30 7215 3,145,342 8/1964 Hill 307-215 3,406,320 8/1968 Hemker 307-215 DONALD D. FORRER, Primary Examiner H. A. DIXON, Assistant Examiner US. Cl. X.R. 307215

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