Patent Publication Number: US-2023147158-A1

Title: Very high resolution speed and position sensor

Description:
BACKGROUND 
     1. Field 
     The present application relates to sensors and sensorics, and more particularly to a very high resolution sensor for detecting angular rotation of a toothed wheel or a magnetic pole wheel and a method of detecting angular rotation of an toothed wheel. 
     2. Description of Related Art 
     Conventionally, wheel speed sensors may be mounted on the knuckles of a vehicle. The wheel speed sensors may detect a rotation of a wheel with which the wheel speed sensor is associated and output a pulse when a specified angular rotation is detected. 
     A pulse output by the wheel speed sensor may be utilized for vehicle control, such as to calculate a wheel speed according to the frequency of the pulses or a distance traveled according to the quantity of output pulses. Therefore, utilizing the angular rotation of the wheel about a radial axis of the wheel and a diameter of the wheel, the displacement or distance of the wheel traveled across a surface, such as a road, may be determined. Alternatively, the frequency of the pulses, such as a number of pulses per second, may be used to calculate an overall speed of the vehicle. Accordingly, various vehicular applications may leverage this information to provide appropriate vehicle control. 
     In one example, a speed of a wheel detected by a wheel speed sensor may be utilized to implement an anti-lock braking system (ABS). In particular, the wheel speed detected by a wheel speed sensor at one wheel may differ from the wheel speed detected by another wheel speed sensor at another wheel. Accordingly, the wheel speeds of the wheels detected by the various wheel speed sensors may be analyzed to determine whether slippage of one or more wheels is occurring during a braking operation, and if so anti-lock braking may be performed to account for such slippage, prevent wheels from locking, and to more safely brake the vehicle. 
     In an additional example, autonomous or semi-autonomous vehicles may perform parking of a vehicle, such as an autonomous or driver assisted parallel parking operation. To safely position the vehicle when parallel parking is performed, an accurate and precise position of the vehicle is required to avoid objects, such as curbs and other vehicles. Thus, fine control of the wheels of the vehicle is necessary, to more accurately and precisely control the position of the vehicle and to more safely and quickly park the vehicle. 
     Accordingly, a very high resolution wheel position and speed sensor would increase the precision and accuracy of vehicle systems for better controlling vehicle position. 
     SUMMARY 
     Aspects of embodiments of the present application relate to a very high resolution sensor for detecting angular rotation of an object about an axis and a method of detecting angular rotation of an object about an axis. 
     According to an aspect of an embodiment, there is provided a very high resolution sensor including a first pair of sensors configured to detect a first magnetic flux density differential of a rotating target; a second pair of sensors configured to detect a second magnetic flux density differential of the rotating target; and a controller configured to determine that a second value of the second magnetic flux density differential of the rotating target reaches a first value of the first magnetic flux density differential of the rotating target and output a pulse corresponding to a degree of rotation of the rotating target. 
     According to an aspect of an embodiment, there is provided a method of detecting an angular rotation of a rotating target, the method including detecting, by a first pair of sensors, a first magnetic flux density of a rotating target; detecting, by a second pair of sensors, a second magnetic flux density of the rotating target; determining that a second value of the second magnetic flux density differential of the rotating target reaches a first value of the first magnetic flux density differential of the rotating target; and outputting a pulse corresponding to a degree of rotation of the rotating target. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects will be more clearly understood from the following brief description taken in conjunction with the accompanying drawings, in which: 
         FIG.  1    is a diagram illustrating a very high resolution sensor, according to an embodiment; 
         FIG.  2    is a graph illustrating magnetic flux density differential of a rotating target detected by a very high resolution sensor, according to an embodiment; and 
         FIG.  3    is a flowchart of a method of detecting angular rotation of an object, according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    illustrates a very high resolution sensor, according to an embodiment. 
     A very high resolution sensor  100  according to an embodiment includes a first pair of magnetic sensors  110 , a second pair of magnetic sensors  120 , a substrate  130 , and a controller  140 . 
     The first pair of magnetic sensors  110  and the second pair of magnetic sensors  120  may be Hall effect sensors mounted on a substrate  130 . The first pair of magnetic sensors  110  and the second pair of magnetic sensors  120  may be identical sensors or sensors having a same sensitivity. 
     The substrate  130  may be, for example, a substrate of a wheel speed sensor (WSS) for detecting rotation of a shaft to which a wheel of a vehicle is mounted, a substrate of an engine speed sensor (ESS) for to which a crankshaft of an engine is mounted, or any other substrate of a rotation sensor for detecting rotation of an object about an axis of rotation. 
     The first pair of sensors  110  may include a first sensor  112  and a second sensor  114 . The first sensor  112  and the second sensor  114  may be mounted to the substrate  130  at a first distance d 1  from each other. Accordingly, a center line  116  between the first sensor  112  and the second sensor  114  may be half (d 1 /2) the first distance d 1  between the first sensor  112  and the second sensor  114 . 
     The second pair of sensors  120  may include a third sensor  122  and a fourth sensor  124 . The third sensor  122  and the fourth sensor  124  may be mounted to the substrate  130  at a second distance d 2  from each other. Accordingly, a center line  126  between the third sensor  122  and the fourth sensor  124  may be half (d 2 /2) the second distance d 2  between the third sensor  122  and the fourth sensor  124 . 
     The first distance d 1  between the first sensor  112  and the second sensor may be equivalent to the second distance d 2  between the third sensor  122  and the fourth sensor  124 . 
     The first pair of sensors  110  and the second pair of sensors  120  may be aligned in the form of a row on the substrate  130 . The alignment of the sensors formed in a row may be parallel to a direction of the angular rotation of a rotating target. 
     The substrate may be positioned with respect to a target such that the first pair of sensors  110  and the second pair of sensors detect an angular rotation of the target wheel. For example, the target may be a shaft or axle to which a wheel is mounted. The shaft or axle may possess a completely regular pattern, thereby enabling the electronic control unit to calculate the speed of rotation based on the quantity of pulses per period or the distance traveled of the wheel to which the wheel is mounted based on the quantity of pulses, the effective distance d along the target perimeter, and the diameter of the vehicle wheel. 
     According to the positioning of the first pair of sensors  110  and the second pair of sensors  120  relative to the rotating target, a magnetic flux density differential may be measured. In particular, because of the alignment of the first pair of sensors  110  and the second pair of sensors  120  relative to the rotating target, and because of the common distance d 1  between the first pair of sensors  110  and the common distance d 2  between the second pair of sensors  120 , the magnitude or value of the magnetic flux density differential output by the first pair of sensors  110  and the second pair of sensors  120  will be equivalent, but detected as shifted in time during target wheel rotation. 
     More specifically, the first sensor  112  and the second sensor  114  of the first pair of sensors  110  may execute a first magnetic flux density differential measurement of the target, as the target rotates about the axis of rotation. The first magnetic flux density differential measurement of the target may be output from the first sensor  112  and the second sensor  114  to the controller  140 . 
     The alignment of the first pair of sensors  110  on the substrate  130  relative to the rotating target may produce the first magnetic flux density differential of the target measured at a first time. 
     On the other hand, the third sensor  122  and the fourth sensor  124  of the second pair of sensors  120  may detect a second magnetic flux density differential of the target, as the target rotates about the axis of rotation. The second magnetic flux density differential of the target may be output from the third sensor  122  and the fourth sensor  124  to the controller  140 . 
     The alignment of the second pair of sensors  120  on the substrate  130  relative to the rotating target, and such alignment being relative to the first pair of sensors  110 , may produce the second magnetic flux density differential of the target measured at a second time, which is later in time than the first time. 
     The controller  140  may be a central processing unit (CPU), electronic control unit (ECU), microprocessor, application-specific integrated circuit (ASIC), or other programmable circuitry. The controller  140  may include memory, such as random access memory (RAM), cache memory, or other memory programmed to store computer-readable instructions executable by the controller  140  for controlling operations of the very high resolution sensor  100 . 
     The computer-readable instructions executed under the control of the controller  140  may cause the controller  140  to perform a method of detecting rotation of a rotating target. 
     The controller  140  may be mounted to the substrate  130 . 
     The controller  140  may be communicatively coupled to the first pair of sensors  110  and the second pair of sensors  120  through, for example, a wired bus or wireless communication interface that performs communication by one or more wireless protocols, such as WiFi, Bluetooth, or other applicable wireless communication protocol or standard. 
     The controller  140  may receive the first magnetic flux density differential measurement from the first pair of sensors  110  and the second magnetic flux density differential measurement from the second pair of sensors  120 . The controller  140  may determine a target wheel position at which the value of the magnetic flux density differential measurement by the first pair of sensors  110  (leading sensors) is equal to the value of the second magnetic flux density differential measurement from the second pair of sensors (lagging sensors). At the position where the output of the lagging pair of sensors  120  is equal to the output of the leading pair of sensors  110 , the controller  140  may output a pulse. 
     The generation of two pulses may indicate a displacement by a distance d of the target detected by the very high resolution sensor  100 . For example, the distance d may indicate a one degree rotation of the rotating target, based on its diameter. 
     The resolution of the very high resolution sensor  100  may be controlled by the distance d between the leading pair of sensors  110  and the lagging pair of sensors  120 . For example, increasing a distance d between the first center line  116  and the second center line  126  may decrease the resolution of the very high resolution sensor  100 . Conversely, decreasing the distance d between the first center line  116  and the second center line  126  may increase the resolution of the very high resolution sensor  100 . 
     The value of the magnetic flux density measured by the two pairs of sensors  110 ,  120  when the sensors  110 ,  120  are located over the exact same position on the target wheel is expected to be the same. To ensure this is the case, filtering, calibration, trimming and other techniques may be used during the manufacturing process of the IC and in corresponding algorithm. 
     As described above, any of various systems receiving the pulse train output by the very high resolution sensor  100  may then utilize the pulse train, which represents the rotation of the target, to determine a speed of rotation of the target, a distance of rotation of the target such as a shaft, a distance of rotation of an object connected to the target such as a wheel attached to a shaft, or any other calculation dependent upon the rotation of the target to be determined. 
       FIG.  2    is a graph illustrating magnetic flux density differential of a rotating target detected by a very high resolution sensor, according to an embodiment. 
     As illustrated in  FIG.  2   , a vertical axis of the graph  200  includes a first amplitude  210  of the first magnetic flux density differential of the target output by the first pair of sensors  110  and a second amplitude  220  of the second magnetic flux density differential of the target output by the second pair of sensors  120 . In  FIG.  2   , the target may be an edge of a gear coupled to a rotating shaft. 
     As described above with respect to  FIG.  1   , the alignment of the first pair of sensors  110  on the substrate  130  relative to the rotating target may produce the first magnetic flux density differential of the target detected at a first time. Consequently, the first amplitude  210  of the first magnetic flux density differential of the target output by the first pair of sensors  110  may be continuously output over time in accordance with the rotation of the rotating target. As illustrated in  FIG.  2   , the values of the first amplitude  210  of the first magnetic flux density differential of the target output by the first pair of sensors  110  may collectively form a leading trace. 
     As described above with respect to  FIG.  1   , the alignment of the second pair of sensors  120  on the substrate  130  relative to the rotating target may produce the second magnetic flux density differential of the target measured at a second time. Consequently, a second amplitude  220  of the second magnetic flux density differential of the target output by the second pair of sensors  120  may also be continuously output over time in accordance with the rotation of the rotating target. As illustrated in  FIG.  2   , the values of the second amplitude  220  of the second magnetic flux density differential of the target output by the second pair of sensors  120  may collectively form a lagging trace. 
     Owing to the alignment of the second pair of sensors  120  on the substrate  130  relative to the rotating target, and relative to the first pair of sensors  110 , the second magnetic flux density differential of the target is output later in time than the first magnetic flux density differential of the target. Additionally, because of the alignment of the first pair of sensors  110  and the second pair of sensors  120  relative to the rotating target, and because of the common distance d 1  between the first pair of sensors  110  and the common distance d 2  between the second pair of sensors  120 , the magnitude or value of the magnetic flux density differential output by the first pair of sensors  110  and the second pair of sensors  120  will be identical. Accordingly, the first amplitude  210  of the first magnetic flux density differential of the target output by the first pair of sensors  110  (“leading trace”) over time may be identical, but shifted in time, from the second amplitude  220  of the second magnetic flux density differential of the target output by the second pair of sensors  120  (“lagging trace”) over time. 
     The controller  140  records the values of the first magnetic flux density differential of the target output by the first pair of sensors  110  (“leading trace”) over time and the second amplitude  220  of the second magnetic flux density differential of the target output by the second pair of sensors  120  (“lagging trace”) over time. The controller  140  may record the values of the first magnetic flux density differential of the target output by the first pair of sensors  110  (“leading trace”) over time and the second amplitude  220  of the second magnetic flux density differential of the target output by the second pair of sensors  120  (“lagging trace”) over time in registers, as a database, lookup table, or other data structure accessible to the controller  140 . Alternatively, the controller  140  may record values of the first magnetic flux density differential of the target output by the first pair of sensors  110  (“leading trace”) every unit of time, such as one microsecond, and output pulses when detecting equivalent values of the second magnetic flux density differential of the target output by the second pair of sensors  120  (“lagging trace”) over time. Accordingly, the values of the first magnetic flux density differential of the target output by the first pair of sensors  110  (“leading trace”) may be recorded over time, while the second amplitude  220  of the second magnetic flux density differential of the target output by the second pair of sensors  120  (“lagging trace”) may be simply detected over time for comparison to the recorded values of the first magnetic flux density differential. 
     As illustrated in  FIG.  2   , when the magnitude or value of the second magnetic flux density differential output by the second pair of sensors  120  becomes equivalent to the magnitude or value of the first magnetic flux density differential output by the first pair of sensors  110 —namely an edge of the rotating target object has moved a distance equal to the distance d between the first center line  116  between the first sensor  112  and the second sensor  114  of the first pair of sensors  110  and the second center line  126  between the third sensor  122  and the fourth sensor  124  of the second pair of sensors  120 —then a pulse  230  is output by the controller  140 . 
     For example, at a point  1  illustrated in  FIG.  2   , the magnitude or value of the first magnetic flux density differential output by the first pair of sensors  110  may have a first value. Then, at a point  2  illustrated in  FIG.  2   , the magnitude or value of the second magnetic flux density differential output by the second pair of sensors  120  may become equivalent to the first value. Accordingly, at point  2  illustrated in  FIG.  2   , a pulse  230  may be output. 
     Similarly, at a point  3  illustrated in  FIG.  2   , the magnitude or value of the first magnetic flux density differential output by the first pair of sensors  110  may have a second value. Then, at a point  4  illustrated in  FIG.  2   , the magnitude or value of the second magnetic flux density differential output by the second pair of sensors  120  may become equivalent to the second value. Accordingly, at point  4  illustrated in  FIG.  2   , another pulse  230  may be output. 
     As illustrated by way of example in  FIG.  2   , the very high resolution sensor  100  may output more than 5 pulses per degree of rotation, depending on the target wheel diameter and general geometry. 
     The resolution of the very high resolution sensor  100  illustrated in  FIG.  2    is merely exemplary. As described above with respect to  FIG.  1   , a resolution of the very high resolution sensor  100  may be configured according to the distance d between the first center line  116  between the first sensor  112  and the second sensor  114  of the first pair of sensors  110  and the second center line  126  between the third sensor  122  and the fourth sensor  124  of the second pair of sensors  120 . 
       FIG.  3    is a flowchart of a method of detecting angular rotation of an object, according to an embodiment. 
     The method of  FIG.  3    may be implemented by the very high resolution sensor  100  described above with respect to  FIGS.  1  and  2   . 
     As illustrated in  FIG.  3   , in step  310 , the method  300  of detecting the angular rotation of an object includes measuring a first magnetic flux density differential of a rotating target using a first pair of sensors. In step  310 , a value of a magnitude of the first magnetic flux density differential of the rotating target may be stored. 
     In step  320 , a value of a second magnetic flux density differential of the rotating target is measured using a second pair of sensors. 
     In step  330 , the value of the magnitude of the first magnetic flux density is compared to the value of the second magnetic flux density. If the value of the magnitude of the second magnetic flux density reaches the value of the magnitude of the first magnetic flux density ( 330 —Y), then a pulse is output by the very high resolution sensor in step S 340 . 
     If the value of the magnitude of the second magnetic flux density has not reached the value of the magnitude of the first magnetic flux density ( 330 —N), then a pulse is not output and measurement of the second magnetic flux density differential of the rotating target is continued to be performed until the value of the magnitude of the second magnetic flux density reaches the value of the magnitude of the first magnetic flux density. 
     As described above, a very high resolution sensor provides improved detection of rotation of a rotating target. The resolution of the very high resolution sensor may not be directly dependent on the number of teeth on the rotating target. Accordingly, a highly accurate and precise measurement of object rotation may be provided.