Catenary Controller

This invention is directed generally to the tensionless winding and unwinding of flexible material onto and off a reel, and in particular to the controlling of a catenary-like section of traveling web material suspended between a support point and a motor-driven rotating reel collecting or dispensing the material.

U. S. Pat. No. 4,195,791 discloses a method and means for monitoring in a contactless manner the low point of a catenary-like section of a traveling optic fiber in order to regulate a spooling motor rotatably driving a take-up reel. The '791 patent utilizes a video camera positioned alongside the section low point to monitor its rise and fall without physically contacting the material forming the catenary-like section. This feature advantageously permits the tensionless winding of very fragile materials (e.g., glass strands, integrated circuit conductor webs, and the like) onto a take-up reel whose rate of rotation is regulated by the video camera signal output to maintain the low point of the catenary-like section at a predetermined position so as to minimize winding tension (determined only by the weight of material forming the catenary section).

It is an object of the present invention to provide a catenary controller of the contactless type that is more rugged and less costly than the type of controller illustrated by the earlier-noted '791 patent.

It is a further object of the present invention to provide a catenary controller of the contactless type that is adaptable to controlling a wide range of materials having different electrical conductivity characteristics, geometries, dimensions, and compositions.

It is a still further object of the present invention to provide a catenary controller of the contactless type that is suitable for use in an environment when vision-obscuring, airborne dirt and dust would hamper the proper operation of optical catenary controller systems of the type illustrated by the '791 patent.

In accordance with the present invention, an ultrasonic transducer is positionable a spaced distance from the low point of a catenary-like section of traveling material suspended between a support point and a rotating reel collecting or dispensing the material. The transducer operates in the pulse/echo mode to provide an output signal indicative of the distance between the section low point and the transducer. A control means, preferably including a preprogrammed microcomputer, responds to the transducer output signal to vary the rotation rate of the reel to maintain a predetermined distance between the transducer and the section low point. Preferably, the reel is rotatably driven by a direct current stepping motor incrementally driven by the digital output of the microcomputer.

A fuller understanding of the invention may be had by referring to the following description and claims taken in conjunction with the accompanying drawings, wherein

FIG. 1 is a perspective view of a catenary controller in accordance with the present invention;

FIG. 2 is a schematic diagram of the controller of FIG. 1;

FIG. 2a illustrates a sensor zone layout used successfully in practicing the present invention; and

FIGS. 3, 4, and 5 illustrate flow charts typical of a suitable computer-controlled operation sequence for the catenary controller illustrated by FIGS. 1 and 2.

In accordance with the present invention, and with particular reference to FIG. 1, there is illustrated a catenary controller including two major structures, namely, an electronic control and sensor unit 10 and a reeling unit 30 whose operation is regulated by the control and sensor unit 10. The units 10, 30 are separately supported and movable relative to each other to permit their being individually positioned for proper control of a catenary section of traveling (linearly moving) web material 52 suspended or hanging between a support point 55 (such as an idler roller or the like) and a motor-driven reel 39 onto and around which the traveling material is wound (or from which it is unwound). The low point 50 of the catenary-like section of traveling material 52, such as, for example, a very fragile metal web of punch press formed integrated circuit conductors, will move up and down depending upon the difference between feed rates of the material into and out of the catenary-like section. The low point 50 will maintain a constant level when the feed rates into and out of the catenary-like section are equal. It is the position of this low point 50 that is monitored by the control unit 10 to regulate the rotational speed of the reel 39 so as to maintain the low point 50 at a generally fixed position, thus applying a generally constant winding and unwinding tension on the material 52 (i.e., a uniform catenary section will be of a generally constant weight, thus applying a generally constant gravity-generated tension force on the material 52).

When the material 52 is of a very fragile nature, it is essential that the low point 50 of the catenary section be monitored in a contactless manner, since physical contact of a sensing element with the traveling web material 52 could damage it. Thus, in accordance with the invention, an ultrasonic transducer 18 operating in the pulse/echo mode senses the low point 50 to monitor the distance between the transducer 18 and the low point 50 of the catenary section so as to maintain the low point 50 generally at a set distance (e.g., 26 inches) spaced from the transducer. The transducer 18 is located at the distal end of a horizontal cantilever-like arm 16, which in turn is supported at the upper portion of a vertical support 14 attached to a floor-supported, pedestal-like control unit base 12. Located atop the vertical support 14 is a controller 20. Preferably, the transducer is located directly above the section low point 50 as illustrated.

In a similar manner, the reeling unit 30 includes a pedestal-like reeling unit base 32 supporting the earlier-noted reel 39 which is positioned at the top portion of a vertical member 34. A motor, in the preferred illustrated form of a permanent magnet direct current stepping motor 38, is mounted to the vertical support member 34 at a position below the reel 39 and provides a rotating shaft 38a, which in turn provides a stepping motor drive sprocket 38b which is positively connected via a drive chain 37 to a driven reel sprocket 36. The reel sprocket 36 is bearing-supported in a conventional manner by the vertical member 34 and provides a reel support shaft 36a upon which the reel 39 is nonrotatably mounted, wherein for each discrete angular rotation motion (e.g., 1.8.degree.) of the stepping motor shaft 38a, the reel 39 will rotate through a proportional angular increment. Preferably, the drive sprocket diameter is less than the driven sprocket diameter to provide for a reduction drive (e.g., 3:1) to permit the motor 38 to incrementally drive heavy reel loads.

The controller 20 functions to provide variable frequency motor control pulses of uniform magnitude via a motor control line 22 (schematically illustrated) to a sequence translator 40 (mounted on the base 32), which in turn powers the stepping motor 38 via a motor power line 42 (schematically illustrated). The line 22, in the form of a flexible cable, is long enough to permit movement of the control unit-supported transducer 18 to a position directly above the low point 50 of the catenary-like section of material 52 so that an interrogation pulse (illustrated by radiation lines 18a) impinges on the low point 50 in a generally perpendicular manner for reflection back to the transducer 18 as an echo pulse (illustrated by reflection lines 18b) constituting a reflected portion of the interrogation pulse (typical pulse/echo elapsed time through air at frequency 50-60 kilohertz - 1.78 ms/ft.).

With reference to FIG. 2, there is schematically illustrated the apparatus of FIG. 1 from an electronic control standpoint.

A suitable transducer of the electrostatic type, used successfully in practicing the present invention, is manufactured and sold by Polaroid Corporation, of Cambridge, Massachusetts, and is known as the "Polaroid Ultrasonic Ranging Unit." The transducer 18, when enabled, will generate an interrogation pulse (lines 18a) constituted by eight cycles of 60 kilohertz ultrasound, followed by eight cycles of 57 kilohertz, followed by 16 cycles of 53 kilohertz ultrasound, followed by 24 cycles of 50 kilohertz ultrasound. The cycles of each frequency are rapidly sequenced and constitute the interrogation pulse (lines 18a) having a duration of approximately one millisecond. The use of four separate frequencies ensures that at least a portion of some of the interrogation pulse can be reflected as an echo back to the transducer 18 from the interrogated material (low point 50) which may be frequency-selective (i.e., absorbs certain frequencies of ultrasound while reflecting others).

The interrogation pulse is radiated downwardly (for example, one interrogation pulse every 70 msec) as illustrated by lines 18a and impinges on the low point 50 of the catenary-like section of material 52, where at least a portion of it is reflected back to the transducer 18 in echo-like fashion. The reflected echo/pulse (lines 18b) and the interrogation pulse lines 18a are received by and generated by an electrostatic, foil-like diaphragm 18c powered by an electronic power supply and pulse control circuit known in the art.

The transducer 18, after being enabled, will provide a pair of control pulses (interrogation and corresponding echo) which are fed via signal lines to a conventional level translator 19 (providing digital output from analog-type input) having corresponding output lines that are inputted to the controller 20, preferably in the form of a digital computer constituted by a single microcomputer-integrated circuit, such as a Series MK 38P74, as manufactured by Mostek Corporation, of Carrollton, Tex. This microcomputer is especially suited for control applications in that it has 32 input/output ports, an internal interval timer, and an external interrupt port. The noted integrated circuit (MK 38P74) is programmed (illustrated by block 20a) via a program control-integrated circuit, such as a Series 2758 EPROM (electronically programmable read only memory, 8 bits.times.1024 bytes), also manufactured and sold by Mostek Corp., that plugs piggyback fashion into the processor controller (MK 8P74).

In accordance with a suitable program 20a contained in the EPROM, an output signal line 22 from the controller 20 provides digital type, direct current pulses (illustrated as signal waveform 22a -symmetrical -50 percent duty cycle) whose frequency determines the stepping rate of the stepper motor 38, a conventional sequence translator 40 being provided to convert the digital pulsing on the pulse line 22 into the required switching sequence needed to incrementally drive the permanent magnet d.c. stepping motor 38. The motor 38, in response to the pulse signal 22a, will rotate its output shaft and the coupled reel through a plurality of angular motions of generally uniform magnitude, the frequency of the pulses determining the rotation rate of the motor. A suitable direct current stepping motor and associated sequence translator are manufactured and sold by The Superior Electric Company, of Bristol, Conn. A direct current stepping motor is preferred, since it provides ideal starting torque and braking characteristics for heavy reel loads and is easily controlled to minimize inertia-generated shocks imposed on the catenary-like section. Further, it is particularly suited to be controlled directly by the digital output of a microcomputer as discussed above. It is clearly contemplated that a digital-to-analog converter could be provided in place of the translator 40 to regulate a conventional variable speed DC servomotor (in place of the stepping motor 38) as an alternative embodiment of the invention).

A typical operating sequence of the catenary controller of the present invention will now be discussed under the assumption that the reel 39 is rotating in a clockwise direction (as viewed in FIGS. 1 and 2) to take up material 52 from the catenary-like section suspended or hanging between the reel 39 (or a reel-associated support) and the support point 55.

In accordance with the present invention, the low point 50 of the catenary section is maintained at a predetermined normal distance, e.g., 26 inches (shown at level "0"), away from the transducer 18, and thus a set distance (e.g., 18 inches) above the floor 13 which supports the control unit 10 and the reel unit 30 (see FIG. 1). If the feed rate of the material from the support point 55 into the catenary-like section increases, the low point 50 will drop down into a lower control zone (-) In so doing, the time between generating the interrogation pulse and receiving the reflected echo pulse will increase. This increase in time, which translates to a greater distance between the transducer 18 and the low point 50 of the catenary-like section, will cause the controller 20 to increase the frequency of the pulse signal 22a by predetermined increments in accordance with the program 20a contained in the program integrated circuit (EPROM). This increased pulse frequency will in turn cause the stepping motor 38 to move in uniform angular increments at a higher rate to increase the rotational take-up speed of the reel 39 and thus raise the low point 50 of the section upwardly to its normal "0" position. For each pulse outputted from the controller 20, the stepping motor 39 will advance by 1.8 degrees, for example. As noted earlier, there is a 3:1 reduction between the driven sprocket 36 and the drive sprocket 38b (located on the reel unit 30; see FIG. 1) so that the reel 39 moves less than 1.8 degrees for each pulse provided by the controller 20 to the translator 40.

Conversely, a decrease in the feed rate of the material into the catenary-like section will cause the low point 50 to rise into an upper control zone level (+) wherein the distance between transducer 18 and the section low point 50 decreases, resulting in a shorter time period between interrogation pulse generation and detection of the corresponding reflected echo. This shorter period of time causes the controller 20 to decrease in predetermined increments the frequency of the pulse signal 22b so as to slow down the rotation rate of the stepping motor 38, and thus lower the section low point 50 back to its normal "0" level position.

It is to be noted that the control circuit as discussed above would generally operate in an opposite manner, with the reel 39 rotating in a counterclockwise direction (as viewed in FIGS. 1 and 2) to dispense material into the catenary-like section for feeding to an external means via the support point 55.

A clearer understanding of a typical operating sequence of the present invention can be had with reference to FIGS. 2A, 3, 4, and 5, which illustrate the programmed regulation of the stepping motor 38 by the controller 20 in accordance with the time durations between interrogation pulse generation and echo portion return generated by the transducer 18, the controlling operation being determined by the preprogrammed integrated circuit EPROM noted earlier. It is to be understood that programs other than that following could be utilized in practicing the invention.

With reference to FIG. 2A, there is illustrated a sensor zone layout extending over a 44-inch vertical distance between the transducer diaphragm 18C and the floor 13, this layout having been successfully used in practicing the present invention, wherein the reel 39 (see FIGS. 1 and 2) is rotating to take up material from the catenary-like section.

As discussed earlier, the low point 50 (FIG. 2) of the catenary-like section of traveling material is desirably maintained at or near a "0" or normal position. As illustrated in FIG. 2A, the normal position ("0" level) was chosen to be 18 inches above the floor or, conversely, 26 inches below the transducer, the distance between the transducer and the floor being chosen at 44 inches, as noted above. With the low point 50 of the catenary-like section detected at the normal "0" level, the frequency of pulses to the stepper motor 38 (FIG. 2) will remain constant for a constant feed rate of material. If the feed rate of material into the catenary-like section increases, the low point 50 of the catenary-like section will tend to drop into an "increment" zone illustrated as extending between the 18-inch level ("0" level) and a level 12 inches from the floor (i.e., the increment zone extends downwardly 6 inches from the normal position of the section low point).

In the illustrated preferred embodiment utilizing the zone layout of FIG. 2A, the transducer 18 senses the position of the section low point approximately every 70 milliseconds. When the low point of the section is sensed as being within the increment zone (12 to 18 inches above the floor), the frequency of pulses driving the stepper motor will be incremented (multiplied) by a factor of 1.08 (at predetermined intervals e.g. 70 msec) so as to provide for a gradually increasing frequency (to a predetermined limit), which will gradually increase the rate of rotation of the reel 39 (FIG. 2) so as to raise the low point of the section back to its normal "0" level. If the low point of the catenary-like section should continue downwardly (rapidly increasing feed rate), it will enter a "double speed" zone extending downwardly from the 12-inch level, constituting the lower boundary of the "increment" zone to a 4-inch level above the floor 13. When the low point of the section is in the "double speed" zone, the last frequency provided to the motor while the low point 50 was is in the increment zone will be doubled. After another period of time (e.g. 70 msec), it will again be doubled, until a maximum speed is reached. This will tend to raise the low point of the catenary-like section rapidly upwardly back to the normal "0" level via the "increment" zone (last frequency is halved and remains constant as low point moves from "double speed" zone to "0" via "increment" zone). If the low point of the section still does not move upwardly, and continues to fall into a lower "hold" zone extending from the floor 13 upward to a 4-inch level (indicating excessive feed rate or a break in the material forming the catenary-like section), pulses (22b-See FIG. 2) to the stepper motor 38 will remain at its last speed, and the rotation rate of the reel 39 will not change.

In a situation where the rate of feed of material 52 into the catenary-like section decreases without a corresponding decrease in the rotary feed of the reel, the low point of the catenary-like section will rise into a decrement section extending upwardly from the 18-inch normal "0" level to a 24-inch level, wherein in a manner similar to that discussed with regard to the "increment" zone (12"-18"), the frequency of drive pulse to the stepper motor will be decremented (divided) by a factor of 1.08 (at predetermined intervals e.g. 70 msec sample time) to gradually decrease it and thus allow the low point of the catenary-like section to move downwardly back to the 18-inch normal "0" level. If the section low point 50 (FIG. 2) continues to rise into a "1/2 speed" zone extending upwardly from the 24-inch level to a 31-inch level, the last frequency applied to the drive motor when the section low point was in the "decremented" zone will be halved at predetermined intervals (e.g. 70 msec) until a predetermined low speed limit is reached, wherein the section low point will rapidly move downwardly towards its normal 18-inch level via the "decrement" zone (last frequency is doubled and remains constant as low point moves from "1/2 speed" zone to "0" level via "decrement" zone). If the low point of the section should continue to move upwardly out of the "half speed" zone, an upper "stop" zone extending upwardly from the 31-inch level to the 44-inch level will be entered, wherein pulses to the stepping motor will cease. An alarm-type switch can be triggered upon entry of the low point 50 into the upper "stop" zone to cease the feeding of material out of the catenary-like section.

It can be seen that the frequency of drive pulses applied to the motor is incremented or decremented a predetermined or fixed amount and then doubled or halved in order to maintain the low point of the catenary-like section at the 18-inch normal "0" level.

To maintain the low point 50 of the catenary-like section at the normal 18-inch "0" level, as discussed specifically with regard to FIG. 2A and as further discussed generally with regard to FIGS. 1 and 2, FIGS. 3, 4, and 5 illustrate in a flow chart fashion a program successfully utilized by the microcomputer discussed earlier included as part of the controller 20 (see FIG. 1). It is to be noted that the program illustrated by FIGS. 3, 4, and 5 is simply an example of one control sequence that has been successfully practiced.

With specific reference to FIG. 3, a start switch or power switch on the controller 20 (FIG. 1) is energized, wherein initial conditions (initialization) for control of the catenary-like section are set up. For example, a pulse frequency of approximately 83 hertz is selected as a starting point for maintaining the section low point 50 at the normal "0" (26 inches from transducer; 18 inches above floor) level. After initialization, the controller 20 will send an "enable" signal (See FIG. 2) to the transducer 18 and then wait to receive a pulse (See FIG. 2) back from the transducer, such pulse indicating that an ultrasonic interrogation pulse (see lines 18a, FIGS. 1, 2) has been generated. If this pulse is not received, the controller will simply cycle as illustrated, indicating that a hardware malfunction has occurred necessitating correction before operation of the catenary controller can resume.

If a pulse indicative of an interrogation pulse generation is received by the controller 20, a normalized V1 count is initiated, wherein one count period is of a time duration equal to the time it takes for the interrogation pulse to travel out and back to the transducer over a one-inch interval. Thus, the controller will start counting (cycling in a count loop) upon receipt of a pulse from the transducer 18 indicative of interrogation pulse generation, the count continuing while the controller 20 waits for the return of an associated echo (indicated to the controller 20 by the transducer 18). If the count reaches 40 (corresponding to 40" level of FIG. 2a) without an echo (See FIG. 2) being sensed by the transducer, the controller 20 will then determine if either an external stop mode switch or a fast run mode switch has been energized. An external stop switch could be used by the operator to cease rotation of the reel taking up the material. If such an external stop is in fact activated, the controller 20 will continuously sense (cycle) to see if the external stop remains activated. When the external stop is deactivated, the controller will again return to the initialization point as illustrated in FIG. 3, to once again begin an interrogation pulse/echo sequence. In the case of a fast run mode activation, a switch, such as a push button switch, has been pressed to cause the reel to rotate at a high speed, such a function being useful when completing the filling of a reel manually. In a manner similar to that earlier discussed with respect to the external stop mode, the controller will continuously monitor the fast run mode switch to see if it is activated, and if activated will continue to cycle and to monitor its condition. When the fast run mode activating switch is released, the controller will return to the point in the program illustrated in FIG. 3 to then return to the point in the program immediately subsequent to the initialization step discussed earlier, wherein a pulse/echo sequence is again undertaken.

If neither the external stop nor fast run modes are activated, the controller will maintain pulse generation to the motor (a count of 40 indicating that the lower "hold" zone (40"-44" from transducer) may have been penetrated by the section low point 50 (FIG. 2).

With reference to FIG. 5, an echo interrupt routine is disclosed, such routine interrupting the main body program illustrated by FIG. 3 each time an echo (See FIG. 2) is received by the transducer 18. If an echo is received before the count V1 reaches 40 (as discussed earlier), the echo interrupt routine of FIG. 5 will run. As illustrated in FIG. 5, if the count V1 is equal to or less than 13 (i.e., if the low point of the catenary-like section is equal to or less than 13 inches away from the transducer-upper "stop" zone-FIG. 2a), the controller 20 will terminate drive pulses to stop the stepper motor. If the count is between 13 and 40 (indicative of the section low point being somewhere between 14 inches and 40 inches from the transducer), the controller 20 will then proceed to determine if the count is equal to a preset count V4, which in the illustrated case is equal to 26, which corresponds to the normal "0" level, i.e., 26 inches downwardly from the transducer or 18 inches above the floor. If the V1 count derived from the echo and the V4 preset by the user equal each other, this indicates that the low point of the catenary-like section is at its normal position ("0" level, see FIG. 2) and that the frequency of drive pulses to the motor should not be altered. If, on the other hand, V1 does not equal V4, this indicates that the catenary-like section is either above or below the normal position. When the low point of the section is below its normal sensed position (V1 greater than V4), the controller 20 will then determine if V1 is less than V4 plus 6 inches or greater than V4 plus 6 inches (i.e., the controller will determine if the catenary-like section low point is in the "increment" zone or the "double speed" zone, as discussed earlier with regard to FIG. 2A). If V1 is less than 6 plus V4, the frequency of the motor will be incremented by the factor 1.08 as discussed earlier and as illustrated in FIG. 5. On the other hand, if V1 is greater than V4 plus 6 inches, the frequency to the motor will be doubled.

Conversely, if the low point of the catenary-like section is above its normal position (V1 less than V4), the controller will then determine if V1 is less than V4 plus 6 inches or greater than V4 plus 6 inches. Dependent upon the position of the catenary-like section (i.e., whether it is in the decrement zone or the half-speed zone), the frequency of the drive pulses to the motor will be decremented by the 1.08 factor or the frequency of the pulses, and thus the motor speed, will be halved. After such an adjustment is made, a newly calculated value V2 is loaded into a register and the echo interrupt is completed, with control being returned to the main body of the program illustrated in FIG. 3. It can be seen that as the echo return time varies, the resultant registry stored value V2 will vary in accordance with the zone at which the low point of the catenary-like section is detected.

FIG. 4 illustrates a conventional time interrupt routine which actually changes the speed of the motor by varying the frequency of the pulse output driving it. A register, which includes the value V2, is associated with another register V3, which in turn is associated with the timer. The count V3 (decremented) determines the time-out period of the timer, the timer counting down until it reaches zero, wherein an interrupt signal is generated. If at the time of the interrupt, V3 is equal to zero, then a pulse is applied to the motor and the value of V2 is substituted for the value of V3 and the countdown procedure begins once again, with V3 incrementing downwardly by one for each interrupt. Thus, by changing the value of V2 in accordance with the echo return count provided by the echo interrupt routine of FIG. 5, the frequency of pulses driving the stepping motor will increase or decrease incrementally, or will half or double so as to maintain the low point of the catenary-like section as at zero position illustrated in FIG. 3.

The use of a microcomputer as applied in the present invention allows programming of the control unit 20 for different applications where different zone layouts (FIG. 2a) may be desired. Further, while a one-inch resolution has been illustrated, a tenth-of-an-inch resolution (4000 counts -0.1 to 40 inches from transducer) can easily be provided where such increased resolution is desired. Further, the present invention has proved to be operable in factory environments where airborne dirt, dust, oil mist, and the like, could prove detrimental to other types of catenry controllers. Further, high ambient noise conditions, typical of a factory environment, have been found not to affect reliable operation of the present invention. Further, the present invention is not an ON-OFF type catenary controller, but rather generally continuously adjusts reel speed (at 70 msec intervals as illustrated) to control the catenary section of material.

The following machine language program has been utilized to successfuly accomplish the teachings as discussed with regard to FIGS. 1 through 5 and is included herein as follows.

Although a preferred embodiment of this invention has been shown and described, it should be understood that various modifications and rearrangements of the parts may be resorted to without departing from the scope of the invention as disclosed and claimed herein.