Background of the Invention
The basic advantage of the human link to a system or process is man's ability to rationalize and to reach a logical decision to situations deviating from the normal. Thus, in order to employ this ability, data must be available and presented in a manner enabling the man to quickly recognize the data characteristic, compare it to known acceptable characteristics and conclude whether or not a problem exists.
Several problems exist in developing a display system that creates the desired control responses. Some of these are:
1. The ability to read the display meters with required accuracy.
2. To evaluate the readings versus acceptable values where acceptable values may vary from parameter to parameter.
3. To detect abnormal conditions quickly before the characteristic condition becomes serious.
4. Evaluate deviations from normal against the need for corrective actions.
It is obvious that a large conventional instrument panel will contain many types of meters ranging from digital displays to multipoint recorders. A man checking this panel must first establish what parameter a particular meter is reading, the value of its scale divisions and the safe limit of the parameter. This represents a considerable amount of thought and integration for each meter and a vastly larger evaluation problem where many meters exist.
The evaluation of these readings against acceptable limits is even more complex since acceptable limits vary for each parameter displayed.
The detection of abnormal conditions depends on the operator evaluating every meter reading, its relative position in the normal operating range and the rate it may be changing. Unless an operator is alert and is continuously checking the instrument panel, the probability of detecting an abnormal reading is small and may not occur until serious system trouble exists.
When deviations are detected, the need for corrective action must be determined and should be based on the parameter deviation and the rate at which it is changing.
Summary of the Invention
A display method, patterns and illustrative apparatus that enables a person to quickly visualize real time conditions in a complex system or process by means of a simultaneous graphic display comprised of a number of measured parameters. The display plots real time histograms into wedge-like segments that are assembled into a circle. Radial displacement of the plot from the outer periphery of the circle, in each wedge, is related to that parameter's deviations from mean acceptable levels.
Angular displacements represent time, past and present. As time progresses fresh data is added, the oldest data is removed, while the remaining data is rotated. Mean acceptable parameter levels are established and normalized so that they produce markings on the outer periphery of the display circle. Maximum acceptable deviation levels are established, for each parameter, then normalized and compressed to produce markings that reach to a second smaller concentric circle. Critical deviation from the mean levels, for each parameter, are also normalized making these markings fall within a smaller concentric circle. The deviation direction is indicated by a plus or minus indicating symbol.
The illustrative apparatus used to implement the display includes a normalizing wheatstone bridge circuit in which one arm is comprised of a voltage controlled resistor element. The mean acceptable voltage level for each parameter nulls the bridge. Diode-resistor circuits normalize and compress these deviations appropriately. The resulting voltage magnitudes are then sampled, converted to binary numbers and stored in a memory. The stored data, continually refreshed and shifted, provides the basis for generating the real time histograms. The clock that controls the entire process also acts to phase lock a sine wave generator, at a much lower frequency, which is then applied to the x and y axis of a cathode ray tube with a 90.degree. phase shift on one axis to produce radial displacements. Modulators, controlled by a digital to analogue converting resistor-switch network, controls the radial displacements. A second frequency divider network, which periodically omits a pulse, activates the z axis of the CRT creating the simultaneous plot of as many as 32 different histograms. The direction of the deviations plotted are marked, in this example, by either angular or radial extended markings, depending on the polarity.
The various aspects and advantages of this invention will be more fully understood from a consideration of the following detailed description in conjunction with the accompanying drawings.
Brief Description of the Drawings
FIG. 1 illustrates the basic display pattern.
FIG. 2 illustrates how time progression occurs in the display pattern.
FIG. 3 illstrates a method for increasing the information content of the basic display pattern.
FIG. 4 illustrates a preferred circuit to normalize and process the voltages received that are indicative of a parameter's amplitude.
FIG. 5 illustrates a preferred circuit for generating the display.
Detailed Description of the Drawings
FIG. 1 illustrates the basic display pattern of the invention. In this example, the display is divided in 8 equal wedge shaped sectors 1-8. The outer periphery of the resulting circle 9, represents the mean normal level for each parameter. Concentric circle, 10, indicates maximum acceptable deviation from a mean normal level. Concentric circle, 11, marks the start of critical parameter levels requiring emergency action. The space between the circle 10 and 11 represents a region of abnormal conditions that do not require immediate reaction. The space between circles 9 and 10 represents normal operation and the space bounded by circle 11 represents critical conditions. The premise behind the normalized deviation presentation of data is that the eye has a limited zone, for a given eyeball position, over which it can provide good resolution and intelligent interpretation. By simultaneously plotting related parameters on a common graphic display and causing all indications that require rapid critical judgments to move to the center of the display, a means for improving the flow of complex information to the judgment centers of the brain is realized. Compressing less important deviations makes them less distracting and better focuses the attention on the important deviation areas. The region between maximum allowable deviations for normal operation, and the onset of critical operation, is a useful region for fault prediction and fault analysis. No deviation compression occurs here. For this example, the radically extended markings indicate positive deviations from the mean level and the angularly extended markings indicate positive deviations.
FIG. 2 illustrates how this real time histogram progresses with time. The extreme clockwise marking in each wedge sector, 1-8, represents the newest data while the markings in the extreme counter clockwise angular position indicates the oldest data. As new data is fed in, the histogram pattern progresses in a counter clockwise direction, for this example.
FIG. 3 illustrates how a display can be made to contain more data. Sector 1a, illustrates a marking that consists of four overlapping markings falling within a given angular unit. For this example, the four markings are negative. The radial thickness of the marking now provides information as to how much change has occurred during the marking interval. The relationship with adjoining markings helps indicate the direction of change. Similarly in sector 2a, four positive markings have occurred causing a radial widening of the marking. Again, each marking's relationship with its adjoining marking gives a sense of direction of change.
FIG. 4 and FIG. 5 illustrate an apparatus design that can be employed to implement the display. FIG. 4 illustrates the deviation normalization and processing circuit, 13, which is used to process the voltage representing each parameter. Potentiometer 14 and amplifier 16 are used to roughly normalize the signal fed to opto-resistor 18. Opto-resistor 18 provides an isolated, voltage variable resistance in which a photo sensitive resistance changes as the voltage controlled light intensity changes. Opto-resistor 18 is part of wheatstone bridge 20. Adjustable resistor 22 is used for fine nulling which establishes a mean normal level. Amplifier 23 provides isolation and some gain. Diode 24 and adjustable resistor 26 are used to control the compression of positive deviations from the mean level and diode 24a and adjustable resistor 26a provide compression for negative deviations. Adjustable resistors 28 and 28a establish the normalized maximum allowed deviation for acceptable operation. Adjustable resistor 30 provides display centering. Transistor 31 amplifies and isolates signals to operate the subsequent network of zener diodes and adjustable resistors that control the normalization of the critical zones for both positive and negative deviations and also controls the degree of compression that results when signals pass into the critical zone. Adjustable resistor 32 and zener diode-adjustable resistor 33, in conjunction with zener diodes 34 and 35, normalize the critical voltage levels while the values of resistor 34a and 35a determine the degree of compression provided for post critical levels. Transistor 36 provides isolation.
FIG. 5 illustrates the display generating apparatus. A signal processor-normalizer, 13, is provided for each parameter being monitored and is connected to assigned terminals of a commutating switch 38, which is stepped through all positions by a voltage fed to it from stepping counter 50. The momentarily sampled voltages are then fed into analogue to digital converter 39. The parallel outputs from the counter are fed into digital memory 40. Ring counter, 44, sequentially reads data stored in memory 40 into series voltage controlled switches 56a-f in series with resistors 58a-f. The resistor values have a binary relationship to each other in that 58a is twice 58b which is twice 58c, etc.
As ring counter 44 reads out the stored data from 116 memory elements, in memory 40, the last 12 steps of the 128 step counter are tied together to feed step counter 50. Step one of counter 50 dumps the stored data from memory 40 into memory 42. Step 2 erases the data in memory 40. Steps 3-10 actuate commutator 38 and A/D converter 39. Step 11 dumps the data stored in memory 42 back into memory 40 with each line shifted 8 places. Step 12 then erases memory 42. This completes the data shift in preparation for receiving new data.
Master clock, 60, which times the entire display, is divided by 128 in divider 62. The divided output is used to phase lock sine wave generator 54 which drives both the y axis of a CRT through isolated modulator 53 and the x axis through a 90.degree. phase shifter and isolated modulator 55. The output of binary resistor network 58a-f adjusts the loss of both modulators. This provides circular electronic beam quadrature sine wave motion that is synchronized to the master clock. The radius of the circle is instantaneously controlled by the summed output current from binary resistor network 58a-f. The beam position is marked by actuating the z axis. The z axis is energized by a circuit comprised of subtraction circuit 64, divider circuit 66, differentiator 72 and one shot multivibrator 74, whose output energizes the z axis.
Divider 66, for this example, divides by 16 and drives divider, 68, which, with one shot multivibrator, 70, inserts one pulse count into subtraction circuit 64 for every n clock pulses, where n is the product of the two divisors of dividers 66 and 68. This subtracted pulse causes an angular progression in the display. For example, if the display has 8 sectors, and the divisor of divider 68 is 8, the marking will progress, in a clockwise direction, one angular unit for every 8 points plotted. If divider 68 were to divide by 32, then four markings would occur in a single angular unit and the number of data points stored on the screen is increased by a factor of 4.
In order to indicate positive or negative deviations from the mean accepted level of each parameter, an angular extension of each marking is created to indicate a negative deviation and a radial extension to indicate a positive deviation. The most significant digit of the conventional binary code is used to actuate the sign. For example, a zero on line 90 would indicate a negative deviation. This closes switch 78 permitting one shot multivibrator 76 to insert a much wider pulse onto the z axis than what multivibrator 74 generates, thereby extending the radial marking width.
When a pulse is fed out on line 90, gate 98 is opened and high frequency oscillator 86 is fed into modulators 55 and 57 to widen the radial marking and indicate a negative deviation.
Other types of displays such as LED and LCD matrices would be instrumented somewhat differently. Where a continuously progressing histogram is not required, mechanical displays, using sensitized paper on a rotating turntable, with an electrically controlled radial displacement and marking by electrical discharge can be used.