Abstract:
A controller for motor activation providing accurate and repeatable position changes by pressing and releasing a push button switch. Repeatable position changes are made in an advance direction by triggering a digital counter for a predetermined number of cycles of a reference clock signal. Backlash in retard motion of the motor is reduced by similarly asserting a retard motor input for an amount of time determined by another digital counter with a following advance correction made automatically after the retard signal is applied, by applying a predetermined retard-advance movement amount, as again counted by a digital counter. The advance binary amount, the retard binary amount and the retard-advance binary amount of set through binary switch inputs to respective counters to count the respective time periods (TG 3 , TG 1 , and TG 2 ).

Description:
RELATED APPLICATIONS 
   This application is a continuation of U.S. application Ser. No. 11/039,352, filed Jan. 20, 2005 now U.S. Pat. No. 7,208,904, which claims the benefit of a prior U.S. Provisional Application No. 60/539,718, filed Jan. 29, 2004. The entire teachings of the above application(s) are incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   The general field of this invention relates to the controlling of motors for accurate discrete remote positioning control throughout the range of a mechanical mechanism. 
   There are many production processes that require frequent adjustments by an operator at the beginning of each new job and during the running of the job. In many instances the adjusting mechanisms are located remotely, requiring the operator to climb a latter or walk a good distance each time an adjustment is necessary. 
   A good example of such an application is in the printing of newspapers. With the advent of four color process printing, which virtually every newspaper offers today, a popular printing machine called a printing tower has emerged as the chosen printing press configuration. The printing tower consists of two four color printing units arranged vertically so that the four process colors (yellow, magenta, cyan and black) are printed simultaneously on each side of the paper. Each printing unit employs two mechanical mechanisms with hand wheels that are used to make adjustments in registration of each color to the other colors. One hand wheel is used for adjustment in the lateral register, in the X direction, while the other mechanical mechanism provides adjustment in the circumferential register, in the Y direction. Thus a tower has a total of 16 mechanical mechanisms that the operator must manually adjust to make corrections in lateral and circumferential registration of the eight colors that are printed on both sides of the paper. 
   The tower configuration is considered to be superior, as it requires minimal floor space which is ideal for crowded press rooms, the vertical configuration requires the operator to climb a ladder to reach some of the mechanical mechanisms each time he needs to make an adjustment. 
   Electric motors have been installed on some of these towers with the intent of providing the operator with remote control capability thus making register adjustments much easier. 
   In those instances where motors have been added to existing mechanisms a number of deficiencies have still arisen that greatly inhibit the success of motorization due to the great frustration of operation personal when using the motor as a means of introducing register correction as opposed to using the hand wheel. 
   Some of these deficiencies are related all can be eliminated with the teachings of this disclosure. 
   The standard method for replacing the hand wheels with a motor includes two operator push buttons, one applying voltage to the motor when depressed by the operator driving the motor in one direction, with the other switch when depressed by the operator driving the motor in the opposite direction. Thus the amount of correction introduced depends upon the direction of correction and for how long the operator depressed the switch. The resolution or minimum correction introduced is limited to the minimum time that the operator could depress the switch which is about one third of a second. There has always been the problem that the maximum slew speed is limited to the resolution required to achieve the accuracy that was desired. Typically a 0.005 inch resolution would yield a slew speed of about 1 inch per minute. If the application was on a full range mechanism requiring moving the mechanism 20 inches for different jobs, than it would take 20 minutes or more to reposition the mechanism. For many applications it is not acceptable to require a two motor system where one motor would be used for obtaining the resolution and another motor used to provide a fast slew speed. 
   The teaching of this application includes a means of increasing the maximum rate of correction significantly as required while simultaneously increasing the resolution. 
   Other deficiencies have arisen when replacing the hand wheel. For example, when using the hand wheel the operator can automatically compensate for backlash in the mechanism when making an adjustment. As he turns the hand wheel to make an adjustment, he can feel the lesser pressure required when moving through the backlash and would always move through the backlash and then make his correction when he felt the higher pressure required to move the mechanism. When moving the mechanism using the electric motors, there was no way to sense backlash with several repeated adjustment required to get through the backlash before an actual correction was made. The lack of backlash compensation using the motors caused great difficulty in accurate positioning and significant frustration for the operator. 
   Hand wheels also have a visual centering means that allows the operator to center each mechanism before starting a new job to make sure that the full range of the mechanism was available if needed to compensate for register errors. Motors have no similar natural centering means with the result that frequently one or more mechanisms would run to a limit stop, requiring a great deal of waste in manually moving all four colors to provide for more range on the unit that ran to the stop. 
   When using the hand wheel in making a correction, the operator could make an exact and repeatable adjustment in either direction which is not possible when using the motor in the face of backlash. 
   Until now the only means of overcoming these limitations when using motors for remote positioning of registration has been to add feedback from the printed image using an automatic register control. The automatic register control would eventually correct for any error including when moving through the backlash by making a number of corrections. However automatic register controls have a number of major disadvantages including very high cost, complexity, the need for significant operator training and the difficulty of locating the printed marks that must be included in the art work for the system to operate. 
   This patent relates to a method to overcome all of these disadvantages and addition provides a low cost alternative to automatic register controls. 
   SUMMARY OF THE INVENTION 
   Among the objectives of this invention is to overcome these deficiencies and provide the following benefits:
     1. Provide a means for greatly increasing the resolution or smallest magnitude of correction that can be introduced by a motorized mechanical mechanism while at the same time increasing the maximum rate of correction that can be introduced.   2. Provide the means for controlling an AC motor to make repeatable discrete positional changes in either direction on any mechanical mechanism on which a motor can be installed and without the use of an encoder or any other conventional feedback device.   3. Provide a means for controlling an AC motor to make repeatable discrete positional changes in either direction for any mechanical mechanism where a motor can be installed independent of any amount of backlash or loss motion in the mechanism or in the coupling between the motor and mechanical input to the mechanism.   4. Provide for automatic centering for each motorized mechanism that can be actuated at the beginning of each job to prevent running into mechanical stops.   5. Provide 1 through 4 to control single or multiple motors simultaneously.   6. Provide the utmost in simplicity to minimize the cost of installation and the need for operator training.   

   The following list details some of the advantages possible in some of the preferred embodiments of the present invention:
     1. By controlling motor activation time electronically, significantly higher and significantly consistent resolutions and slew rates can be achieved.   2. The present invention provides the capability of using low cost AC induction motors with far greater tolerance of friction and inertial loads, greater flexibility and selection of motor power and gearbox ratios.   3. Accurate and repeatable position changes are made each time a switch is first pressed and then released. The time interval for correction is set in integers 120 cycles per second.   4. The low pass filter inherent in the AC induction motor due to armature inertia provides automatic gain reduction with time thus providing a much greater dynamic range with increased accuracy and speed of response over synchronous motors.   5. Repeatable positional changes can be made in both directions that are far smaller than the backlash or loss motion in the mechanism.   6. The complete elimination of any feedback device such as an encoder or potentiometer makes for a greatly simplified and less costly installation.   

   Briefly, the present invention is a method and means of providing a significant increase in resolution and slew rates, repeatable discrete incremental position control with automatic positioning or centering of the mechanism anywhere within its range. These advantages are provided in the face of any degree of loss motion or backlash inherent in the mechanism due to design limitations, wear or poor maintenance. 
   While any motor type can be used with this invention, AC synchronous and AC induction motors are the preferred motor type each providing additional unique capabilities as will be revealed. 
   Installation and application requirements are much simpler as no conventional encoder or feedback device is required thus greatly reducing the costs and simplifying the installation. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing will be apparent from the following more particular description of example embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments of the present invention. 
       FIG. 1  is a block diagram of the system. 
       FIG. 2  is a motor schematic showing limit switches. 
       FIG. 3  illustrates an operator control panel. 
       FIGS. 4A and 4B  are an electrical schematic counter circuitry. 
       FIGS. 5A and 5B  are an electrical schematic of the incremental, backlash and centering state machines. 
       FIGS. 6A and 6B  are a schematic of the operator interface logic. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A description of example embodiments of the invention follows. 
   Prior art motor positioning has been limited to either stepper motors in an open or closed loop configuration and other motor types in a closed loop configuration using encoder or potentiometer feedback.
     1. Stepper motor control: Stepper motors are motors that advance a specific amount for each power pulse applied to the windings of the motor. They are highly susceptible to inaccurate counting in applications where high friction and inertial loads are encountered and thus in these applications an encoder is usually employed. Due to the added complexity of power circuitry and its added cost with additional maintenance and cooling requirements, stepper motors are rarely used in all but the lowest power applications with little friction and constant low inertia applications.   2. Closed loop potentiometer feedback: This method is the most common method of feedback position control currently in use on existing machines. The output of a potentiometer, (variable resistance ratio device) usually ten turns, is connected through a suitable gear ratio so that the range of the potentiometer covers the entire range of the mechanical mechanism. The position of the potentiometer slider corresponds to the position of the mechanical mechanism with the voltage ratio of the slider voltage to the excitation voltage representing an analogue of the position of the mechanical mechanism.   3. Closed loop encoder feedback. This method substitutes an encoder (usually an optical encoder) for the potentiometer as described above. Digital pulses are generated directly by the optical encoder and when accumulated in a counter represents the position of the mechanical mechanism. While this method can be more accurate than the potentiometer, it requires significant additional complexity and unacceptable costs for most position control applications in view of this disclosure.   

   In general all of the above methods of position control are limited and suffer from the following disadvantages:
     1. For applications requiring power (⅛ HP plus or minus) because of high friction or inertial loading all of the above methods of position control are cost prohibitive.   2. All of the above methods of position control require detailed engineering analysis for each application with little leeway in providing stable operation with variations in friction and inertial loading.   3. All of the above methods of position control have limited selection of available gearbox motor combinations and require engineering design for each application to incorporate limit switches which prevent damage to the mechanical mechanisms.   4. All of the above methods of position control require individual selection of all of the parts or assemblies associated with the application from numerous sources. This includes motor, gearbox, limit switches power amplifiers.   

   A variety of different motor types have been installed on formerly manually controlled mechanisms to provide remote activation without the need of the operator to leave his operating station to make corrections. The most common types of motors used for this purpose have been either 2 or 3 phase motors. The most common motor that has been used for this purpose for many years is the 2 phase synchronous motor and specifically the line of synchronous motors manufactured by the Superior Electric Co. under the trade name of SLO SYN. The advantage of the SLO SYN motor over other motor types is its high reliability, and its simplicity of electrical and mechanical interconnections. 
   The ability of the SLO SYN motor to start and stop within 0.025 seconds eliminates the need for a brake to prevent overrunning or coasting as is required in 3 phase motors when accurate positioning using this invention is desired. 
   Although the SLO SYN motor is ideal and provides the most accurate positioning for very large distances, it has a number of disadvantages that make it unsuitable for many applications where high inertia and friction loads are encountered and where higher resolutions and slew rates are required. Where high inertial and friction loads are encountered or where higher resolutions and slew speeds are desired, the 2 or 3 phase AC Induction Motors like those manufactured by Oriental Motor Co. of Japan are better suited using this invention. 
   Thus a major advantage of this invention is the ability to use many different motor types to provide for a variety of different applications. 
   In applications where former manually positioned mechanisms have been motorized to make it easier for the operator to make manual corrections, serious operational deficiencies have been encountered that have limited the success of this cost effective method for reducing the physical demands on operating personnel. 
   While this invention has been particularly shown and described with references to example embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims. 
   DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
   A multiple motor controller consists of a number of components connected as stated below. 
     FIG. 1  is an overall block diagram of the interconnections of the system components that provide for simultaneous control of up to eight motors according to this disclosure. As each motor performs in the same manner the connections for one motor  104  will be described. 
   Motor  104  of  FIG. 1  is better described from the enlarged view as shown in  FIG. 2 . 
   Motor  200  of  FIG. 2  can be any motor however, the two phase reversible induction motors manufactured by the Oriental Motor Company of Japan are preferred. Motor  200  is restricted in its travel in both directions via adjustable limit switches  201  and  202 . That is, when the motor runs in one direction it will eventually open either limit switch  201  or  202  to stop the motor before it jams up or causes damage to the mechanism. In addition to stopping the motor before it reaches the end of its travel, the limit switches also provide a basis for timing the motor to center it or position it to a specific position as will be discussed. 
   In referring back to  FIG. 1 , motor  104  is connected to interconnection panel  102  through connector  103 . Phase shift capacitor  101  is also connected to Motor  104  through connector  103 . 
   Motor  104  connections are routed through connector  105  and connected to solid state relay  106 . Solid state relays  106  and  107  plus computer  108  provide for bidirection control of four motors. Relays  106  and  107  are manufactured by OPTOo-22 as their Model G4PB4R. 
   Operator Panel  109  connects directly to computer  108  which provides the signals that are conditioned on computer  108  providing the advantages as described in this disclosure. 
     FIG. 3  is a drawing of the operator control panel  109  of  FIG. 1 . The top four sets of operator control buttons are arranged vertically as they control the circumferential register where the lower sets of four control buttons are arranged horizontally as they control the lateral register, however the connections are the same for both functions. Thus only the right hand control buttons will be described. 
     303  represents a toggle switch which, when toggled in one direction, will directly activate the motor in one direction, and when toggled in the opposite direction will directly activate the motor in the opposite direction. This provides a very fast slew speed of the motor and is used only for initial setup or if large errors are present at startup. 
     302  and  304  are simple push buttons which when depressed will close a contact. One switch  302  closes a contact in the advance direction while the second switch  304  closes the contact in the retard direction. 
     301  and  305  are neon lamps that will light up when the motor is running or when it runs into a stop opening the limit switch contact  202  or  201  of  FIG. 2 . 
   Push button  306  initiates the automatic centering function as will be described. 
   In operation, the operator depresses an advance or retard push button  302  or  304  on Operator Control Panel  109  of  FIG. 1  which sends a signal to circuit board  108  of  FIG. 1  that conditions the signal, which then goes to solid state relay  106  of  FIG. 1 , that then activates the respective motor in the desired direction according to the instructions that come from circuit board  108 . 
     FIGS. 4A ,  4 B,  5 A,  5 B,  6 A and  6 B are detailed schematics of circuitry that together with the components already described provide the features that are the subject of this invention. 
   Specifically  FIGS. 4A and 4B  illustrate details of the counter circuitry that provides the timing to implement the features of incremental discrete correction, automatic backlash and centering.  FIGS. 5A and 5B  define the state machines that provide these features, and  FIGS. 6A and 6B  define the interface circuitry between the operator input and the resulting motor operation. 
     401  and  402  of  FIG. 4B  are 8 bit bidirectional binary counters connected as a single 16 bit counter. They are commercially available chips manufactured by Fairchild Semiconductor of Portland, Me. their product number 74F269. The 74F269 chips have an eight bit preset which is connected by a bus to chips  403  through  407  ( FIGS. 4A and 4B ), which are Octal Bidirectional transceivers with 3 state outputs also manufactured by Fairchild Semiconductor as their product number 74F245. 8 bit binary switches  409  through  417  are connected to the inputs of transceivers  403  through  407  respectively. Eight bit pull up resisters  408  through  416  are also connected to the 8 bit binary switches  409  through  417  respectively and provide current for a binary  1  value. 
   Counters  401  and  402  count clock pulses  426  and  422 , respectively these clock pulses can be generated from a number of sources but in this embodiment a Fairchild Semiconductor chip H11A817 which is  501  of  FIG. 5  is used because of its simplicity and low cost. This chip is an optically coupled device that will generate 120 cycles per second (cps) from a 60 cps voltage source. Item  502  of  FIG. 5  represents the 120 cycle clock source, and item  503  of  FIG. 5  processes this frequency through a flip flop to provide a 60 cps clock source. The 120 cps clock source represent pulses that are 1/120 or 0.0.0083 seconds in duration. 
   As each set of binary switches, pull up resisters, and octal transceiver in  FIGS. 4A and 4B  function in the same manner only the set consisting of  409 ,  408 ,  403 ,  419 ,  420 , and  421  will be described now in detail. 
   A binary number from 1 to 16 bits long is selected in binary switches  409  and  421 . This number represents the number of 0.0083 clock time periods that the counters will be preset to, after which the counters will then count down to zero, providing a time interval equal to the present number times of 0.0083 second pulse intervals. 
   Incremental Advance Correction 
   This action is triggered when the operator presses an advance push button  301  of  FIG. 3 , which is connected to one of the four advance flip flops (FFs)  601 ,  612 ,  614 , and  616  of  FIGS. 6A and 6B . For this discussion, consider that FF  601  is connected to push button  301 . This initiates the following sequences: 
   The Q output of flip flop  601  of  FIG. 6A  is set to a 1. 
   The output of gate  504  through gate  505  clocks FF  506 , setting its Q output high. 
   After 2 Clk pulses the Q output of FF  507  goes high and with the still high notQ of  508  provides a notA at the output of gate  511 . 
   This notA pulse goes to  414  and  415  loading the contents of binary switches  409  and  412  in to counters  401  and  402 . On the next clock cycle, the contents of binary switches  409  and  412  are clocked into the counters when the output of gate  513 , PE goes low. 
   This starts counters  401  and  402  to count down and when they reach zero output pulse  418 , notTC is asserted. 
   TC clocks FF  509  complete the time interval represented by the output of FF  508  TG 3 . 
   After two clock cycles, the original FF  601  of  FIG. 6A  that started the action is reset through the clear  602  signal of  FIG. 6B . 
   During the time interval TG 3  which is an input to  603 , an output signal is generated through gates  604  and  605  which activates an optically isolated relay running the motor at full speed during the time interval TG 3 . 
   Backlash Considerations 
   In the advanced direction the motor is always run in the same direction so that the backlash is always loaded out in one direction. However in the retard direction the motor is first reversed for a total increment that equals an amount equal or greater than the amount of backlash defined here as (XBL) plus the amount of correction desired, called CD, and then advanced an amount equal to XBL. In this manner the mechanism is automatically loaded out in the retard direction thus providing the finest resolution independent of the magnitude of the backlash or wear in the mechanism. 
   Incremental Retard Correction 
   The action is triggered when the operator presses a retard push button  304  of  FIG. 3  which is connected to one of the four retard FF&#39;s  607 ,  613 ,  615 , and  617  of  FIGS. 6A and 6B . For this discussion consider that FF  607  is connected to push button  304 . This initiates the following sequences: 
   The Q output of flip flop  607  of  FIG. 6A  is set to 1. 
   The output of gate  526  through gate  514  clocks FF  516  setting Q high ( FIGS. 5A and 5B ). 
   After 2 Clk pulses the Q output of FF  517  goes high and with the still high notQ of  518  provides a notBR at the output of gate  524 . 
   This notBA pulse goes to  427  and  428  loading the contents of binary switches  411  and  434  in to counters  401  and  402 . On the next clock cycle the contents of binary switches  411  and  412  are clocked into the counters when the output of gate  513 , PE goes low. 
   This starts counters  401  and  434  to count down and when they reach zero output pulse  418  notTC is generated. 
   TC clocks FF  519  completing the time interval represented by the output of gate  525  TG 1 . Note this is the time interval for which the motor is reversed equivalent in time to both the amount of backlash and correction desired. 
   During the time interval TG 1  which is an input to  608 , an output signal is generated through gates  610  and  611  which activates an optically isolated relay running the motor at full speed in the retard direction during the time interval TG 1 . 
   When FF  519  is clocked by TG, it starts an 8 clock delay through FF  520  and counter  527 . During this delay time the motor will automatically come to a stop before a reverse voltage is applied to advance the motor. This provides a softer transition from full speed in one direction to full reverse voltage in the opposite direction. 
   At the end of the delay FF  520  through gate  523  loads the contents of binary switches  413  and  435  into counters  401  and  402  through pins  429  and  430  of octal bidirectional transceivers  405  and  439  respectively. At the same time the contents of binary switches  413  and  435  are loaded into the counters through gates  512  and  513 . 
   This starts counters  401  and  402  counting down to zero and when zero is reached the signal TC clocks FF  521  producing the time interval  526  TG 2 . 
   Time interval TG 2  goes to gate  609  and trough gates  605  and  606  run the motor in the advance direction for the interval TG 2 .  526   
   The remaining 9 FF&#39;s shown at the bottom of  FIGS. 5A and 5B  provide for automatic centering of the mechanism. However it functions in the same manner as the Retard correction and thus will not be described. 
   Comments and Conclusions 
   The previous detailed description of the method for providing exact incremental correction to a motor has a number of unique application advantages. 
   1. The resolution of the motor (minimum correction) can be any value depending upon the clock frequency selected and capability of the motor. In this disclosure the clock frequency is selected as 0.0083 seconds which allows the motor to be actuated for a minimum time of 0.0083 seconds. 
   Typically an operator can manually actuate a switch in a minimum time of about 0.33 seconds. Thus a considerable improvement in resolution is possible allowing a significant increase in slew speed for those applications where frequent large excursions in compensating mechanisms are required in setting up new jobs. 
   2. The ability to provide exact and repeatable corrections in either direction enable the ability to provide the same resolution in the face of any degree of backlash or wear in the mechanism. 
   A single 16 bit counter enables intervals of from 1 to 65,536 clock pulses. With a clock period of 0.0083 seconds, the total time intervals can be set from 0.0083 seconds to 9.102 minutes (65,536×0.0083). 
   In the application of motorizing previously manually controlled hand-wheels, the time intervals for both the advance and retard directions can be pre set very accurately by knowing the following information most of which is obtained by direct measurement. 
   A. The minimum correction desired. Example: 0.005 inch in both the advance and retard direction. 
   B. Maximum correction in one revolution of the hand-wheel. Example: 0.1 inch. 
   C. Maximum rate of motor correction. Example: 1″/minute. 
   D. Amount of loss motion when reversing direction. Example: 20 degrees. 
   Calculate from the above as follows Correction/Second=0.016″/sec. 
   Correction time for Advance-Retard 0.005″=0.31 sec. 
   Correction time for loss motion 20/360×6=0.33 sec. 
   This one can set the binary switches as follows: 
   Enter into Advance Binary Switch  409  of  FIG. 4  binary number 37 (0.31/0.0083) equal to LS 10100100. 
   Enter into Retard Binary Switch  411  of  FIG. 4  binary number 77 (0.31+0.33)/0.0083 equal to LS 10110010. 
   Enter into Retard-Advance Binary Switch  413  of  FIG. 4  binary number  39  (0.33/0.0083) equal to LS 11100100. 
   While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.