Abstract:
A system and method is disclosed for detection of a direction of movement of a component using a single inductive sensor. The component may be a rotational component such as a motor, shaft, gear, or the like. An ON and/or OFF time of the inductive sensor is measured as north and south poles of one or more magnets are moved past a face of the inductive sensor. A directional correlation is established which allows for determination of an unknown direction of movement.

Description:
BACKGROUND 
     Field of the Invention 
     This invention relates to determining a direction of motion of a moving object using an inductive sensor. 
     Background of the Invention 
     An inductive proximity sensor looks for changes in a magnetic field or return signal in order to detect a metallic object or position of a metallic object. Inductive proximity sensors have a high reliability and long functional life because of the absence of mechanical parts and lack of physical contact between sensor and the sensed object. Inductive proximity sensors are able to detect movement, speed and position but are unable, to date, to detect a direction of movement using a single inductive proximity sensor. Thus, there is a need in the art for a single inductive proximity sensor which can detect movement, speed, position and direction of movement. The instant invention solves the problem of using a single inductive sensor to detect movement, speed, position, and direction of movement. 
     SUMMARY 
     The disclosed invention has been developed in response to the present state of the art and, in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available apparatus and methods. Accordingly, apparatus and methods in accordance with the invention have been developed to provide direction detection of a moving object or moving component using a single inductive sensor. The features and advantages of the invention will become more fully apparent from the following description and appended claims, or may be learned by practice of the invention as set forth hereinafter. 
     A system and method is provided for detection of a direction of movement of a component using a single inductive sensor. The component may be a rotational component such as a motor, shaft, gear, or the like. An ON and/or OFF time of the inductive sensor is measured as north and south poles of one or more magnets are moved past a face of the inductive sensor. A directional correlation is established which allows for determination of an unknown direction of movement. 
     Consistent with the foregoing, a system and method for providing direction detection of a moving object or moving component is disclosed. Such a system includes a rotational component with one or more magnets fixed thereto, a power source for powering the inductive sensor, and a processor configured to determine an ON time and OFF time of the inductive sensor as the moving component rotates the north and south poles of each of the one or more magnets past a face of the inductive sensor. A corresponding method is also disclosed and claimed herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the advantages of the invention will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered limiting of its scope, the invention will be described and explained with additional specificity and detail through use of the accompanying drawings, in which: 
         FIG. 1  is a top view showing an embodiment of a moving component with more than one magnet and an inductive sensor in accordance the invention; 
         FIGS. 2 a  and 2 b    are timing diagrams of directional ON and OFF outputs of an inductive sensor in accordance with an embodiment of the present invention; 
         FIG. 3  is a perspective view of a moving component with more than one magnet and an inductive sensor in accordance with an embodiment of the invention; 
         FIG. 4  is a top view of a moving component with more than one magnet and an inductive sensor in accordance with an embodiment of the invention; 
         FIG. 5  is a perspective view of a moving component with more than one magnet and an inductive sensor in accordance with an embodiment of the invention; 
         FIG. 6  is a perspective view of a moving component with more than one magnet and an inductive sensor in accordance with an embodiment of the invention; 
         FIG. 7  is a top view of a moving component with more than one magnet and an inductive sensor in accordance with an embodiment of the invention; 
         FIG. 8  is a top view of a split rotational moving component with more than one magnet in accordance with an embodiment of the invention; 
         FIG. 9  is a top view of a moving component with more than one magnet and an inductive sensor in accordance with an embodiment of the invention; 
         FIG. 10  is a top view of an extruded rotational cylinder with an inductive sensor and magnets in an inner area of the cylinder; and 
         FIG. 11  a schematic flow diagram of a system for determining direction in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     It will be readily understood that the components of the present invention, as generally described and illustrated in the Figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the invention, as represented in the Figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of certain examples of presently contemplated embodiments in accordance with the invention. The presently described embodiments will be best understood by reference to the drawings. 
     Referring to  FIG. 1 , a view of a rotational moving component  106  is shown with magnets  110 ,  112 ,  114 , and  116  attached thereto. Each of the north poles  104 ,  118 ,  122 , and  128  are alternately arranged with the south poles  102 ,  120 ,  124 , and  130  around moving component  106 . An inductive sensor face  108  is positioned in a fixed position in a close proximity to magnets  110 ,  112 ,  114 , and  116  such that when moving component  106  rotates each north pole and each south pole of each magnet  110 ,  112 ,  114  and  116  pass in front of inductive sensor face  108  causing a magnetic field to penetrate into the sensor face  108 . The inductive sensor  142  may have three or more wires for powering the inductive sensor and providing an output of an ON state or OFF state of the sensor  142 . Moving component  106  may rotate in a clockwise direction  138  or a counter clockwise direction  140 . 
     The inductive sensor face  108  may be positioned perpendicular to a north-south direction of each of the one or more magnets  110 ,  112 ,  114 , and  116 . 
     In  FIGS. 2 a  and 2 b   , timing output diagrams of a sensor system as shown in  FIG. 10  is presented for two directions of movement of a moving component such as is shown in  FIG. 1 .  FIG. 2 a    shows one direction of movement with an ON time of an inductive sensor as a function of north and south poles of magnets passing a face of the inductive sensor.  FIG. 2 b    is on the same time scale and uses the same rotational speed as is shown in relation to  FIG. 2 a   . The ON time  202  shown in  FIG. 2 a    represents a first direction of motion and the ON time of  FIG. 2 b    represents a second direction of motion of a system of the present invention. It is clearly evident that the ON time  202  of  FIG. 2 a    is less than the ON time  206  of  FIG. 2 b   . Each cycle shown is a result of a north and south pole of a magnet being rotated past the face of an inductive sensor. When the rotation direction is reversed, the ON timing and OFF timing also change. When the inductive sensor senses the changing magnetic poles a delay in switching of the output of the inductive sensor takes place. This difference can be utilized to determine a direction of rotation in accordance with the invention herein disclosed. 
     In  FIG. 3 , a disk  304  is attached to a rotational shaft  310  with magnets  306  and  308  on an outer surface of disk  304 . Here disk  304  only uses two magnets  306  and  308 . These magnets need not be at 180 degrees separated from each other. Inductive sensor  312  is located at a distance  302  from magnet  308 . Distance  302  is optimally from 0.010 to 1 inch. Inductive sensor  312  may be a Hall effect sensor or other inductive sensor which is capable of sensing a changing magnetic field. 
       FIG. 4  shows a top view with magnets inset in a cylinder or disk. The magnets are arranged with north poles  402 ,  404 ,  406  and  408  in a similar side of each magnet and south poles  410 ,  412 ,  414 , and  416  on similar opposite sides of the magnets. The north and south poles need to be consistently placed in reference to a similar side of the magnet. Accordingly, poles  402 ,  404 ,  406 , and  408  can all either be “North” poles or “South” poles. The same is true with poles  410 ,  412 ,  414 , and  416 . 
       FIG. 5  shows a motor  502  with a magnet  508  in a keyway  506  of the motor shaft  504 . Here only one magnet  508  is used to determine a direction of rotation of the motor shaft. The north and south poles of the magnet are rotated past sensor  510  in order to determine a direction of rotation of the motor shaft. 
     In  FIG. 6 , we have a disk with magnets partially embedded in a face  602  of a moving component. 
     In  FIG. 7 , a gear system  700  is shown with magnets embedded in gear face  702 . The gear may be made out of metal, plastic, wood, polymer, carbon fiber, non-ferrous metals, ceramic, rubber, elastomeric compounds, glass, or petroleum. 
     In  FIG. 8 , a split rotational component or clamping cylinder  800  containing magnets in an outer surface is shown. The magnets may be place on any surface of the split rotational component which allows the north and south poles of each magnet to be rotated past a face of an inductive sensor. The magnets may be embedded, partially embedded or on a surface of a rotational component of the invention. Rotational component  800  may be split into two sections  802  and  804  by removal of fasteners  806 . A split rotational component  800  may be fastened on to a rotational shaft without removing existing components on a rotational shaft. 
       FIG. 9 , shows a linear moving component  902  for moving in a liner fashion as indicated at  904 . 
       FIG. 10  is a top view of an extruded rotational cylinder  1002  with an inductive sensor  1006  and magnets in an inner area of the cylinder. The inductive sensor  1006  is fixed within the extruded cylinder area  1004 . This configuration may provide increase protection to the magnets and inductive sensor and may be useful in harsh environments such as mines and other indoor and outdoor hazard areas. The rotational cylinder  1002  may be connected to a rotating shaft or driven by a chain or other drive mechanism (not shown). 
       FIG. 11 , shows a schematic block diagram of a system of the present invention. A method of determining a direction of movement will be described in relation to this Figure. 
     Moving component  1104  rotates in a first known (clockwise direction) and inductive sensor switches from an ON state to an OFF state as moving component  1104  rotates. An ON time is determined as a function of rotation speed and the ON time is recorded in a memory of determination system  1108 . The ON time may be determined by many different ways which are well known in the art of signal processing. Such ways may include positive to negative signal transitions, sampling within an ON time with a known frequency, etc. After the ON time is determined for the first know direction it is stored in a memory location of determination system  1108 . Determination system  1108  may include process and memory, a micro-controller, a data acquisition device, a computer and program instruction for carrying out functions related to ON time detection of a sensor, storage of sensor value and comparing of sensor values. Determination system  1108  may also be configured to output a determination of a direction of rotation of moving component  1104 . Next, moving component  1104  is rotated in a second known, opposite direction (counter clockwise), and the ON time is determined and stored in a similar way as that of the first direction. Predetermined bounds or thresholds of the ON times for the first and second directions may be set according to statistical curves allowing for a margin on each side of a fixed value. Next, moving component  1104  is rotated in an unknown direction (either clockwise or counter clockwise) and an ON time is determined and compared to the stored ON time values for known clockwise and counter clockwise rotations. The direction is then determined by choosing an ON time value which is closer to an ON time of a known direction. For example, if the known clockwise ON time was 6 milliseconds and the known counter clockwise ON time was 3 milliseconds and the unknown direction ON time was between a threshold of 2-4 milliseconds the determined direction would be counter clockwise. An ON time and/or OFF time and/or ratio of the ON time to the OFF time may be used to determine a direction of movement of a component. 
     Table 1 below shows results of rotation of a moving component  1104  and sampling data points at a fixed rate for ON times (high data points) and OFF time (low data points) for various sensor distances between the inductive sensor and the rotating magnets. Rotational speeds are also listed. It should be noted that inductive sensors may be setup in an active ON or active OFF configuration and the data points may swap positions depending on the hardware setup of the sensor and type of inductive sensor used. The inductive sensor used in the table below is a normally open type Hall effect proximity sensor. When rotating north and south poles of four magnets past a Hall effect sensor in a clockwise direction at 470 rotations per minute, 16847 samples at 25 kHz were obtained for an ON state time and when rotated in a counter clockwise direction about half of the data samples were obtained for an ON state. This shows a significant switching delay between rotation directions and an ON state of the inductive sensor used. The data is consistent even when the speed of rotation is changed. 
     
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 direction 
                 Hi data pts 
                 Low Data pts 
                 ratio 
                 rpm 
                 distance 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 CW 
                 16847 
                 8753 
                 1.889 
                 470 
                 0.2 
               
               
                 CCW 
                 8876 
                 16724 
                 0.5296 
                 490 
                 0.2 
               
               
                 CW 
                 16952 
                 8648 
                 1.9838 
                 1018 
                 0.2 
               
               
                 CCW 
                 8574 
                 17026 
                 0.5087 
                 1058 
                 0.2 
               
               
                 CW 
                 17415 
                 8185 
                 2.1287 
                 1600 
                 0.2 
               
               
                 CCW 
                 8293 
                 17307 
                 0.4608 
                 1788 
                 0.2 
               
               
                 CW 
                 13796 
                 11804 
                 1.172 
                 529 
                 0.3 
               
               
                 CCW 
                 11311 
                 14289 
                 0.8027 
                 560 
                 0.3 
               
               
                 CW 
                 13791 
                 11809 
                 1.1765 
                 1092 
                 0.3 
               
               
                 CCW 
                 11369 
                 14231 
                 0.8006 
                 1118 
                 0.3 
               
               
                 CW 
                 13692 
                 11908 
                 1.1534 
                 1954 
                 0.3 
               
               
                 CCW 
                 11288 
                 14312 
                 0.7845 
                 1770 
                 0.3 
               
               
                 CW 
                 13582 
                 12018 
                 1.134 
                 3239 
                 0.3 
               
               
                 CCW 
                 11273 
                 14327 
                 0.759 
                 3322 
                 0.3 
               
               
                   
               
             
          
         
       
     
     The apparatus and methods disclosed herein may be embodied in other specific forms without departing from their spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.