Abstract:
A system includes a transceiver module and a rotating device. The transceiver module generates an electromagnetic (EM) field using an antenna. The rotating device includes N transponders arranged such that each of the N transponders passes through the EM field during one revolution of the rotating device. Each of the N transponders damps the EM field when passing through the EM field. The transceiver module determines a rotational speed of the rotating device based on a number of times the EM field is damped during a period. N is an integer greater than or equal to 1.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/185,336, filed on Jun. 9, 2009. The disclosure of the above application is incorporated herein by reference in its entirety. 
     
    
     FIELD 
       [0002]    The present invention relates to determining a rotational speed and position of a rotating device, and more particularly to determining the rotational speed and position using radio-frequency identification technology. 
       BACKGROUND 
       [0003]    The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
         [0004]    A vehicle may include an engine speed sensor to monitor engine speed. The engine speed sensor generates an engine speed signal that indicates rotation of a crankshaft. An engine control module may determine the engine speed based on the engine speed signal. 
         [0005]    For example, the engine speed sensor may include a Hall-effect sensor that detects passing of teeth on a gear connected to the crankshaft. The Hall-effect sensor may generate pulses that correspond to the passing of the teeth. The engine control module may determine the engine speed based on a number of pulses included in the engine speed signal during a period of time. 
         [0006]    The teeth on the gear connected to the crankshaft may be arranged to yield a pattern of pulses when the gear is rotating. For example, a longer tooth may yield a longer pulse that indicates a position of the crankshaft. The engine control module may determine the position of the crankshaft based on the pattern of pulses detected (i.e., pattern recognition) when the gear is rotating. 
       SUMMARY 
       [0007]    A system comprises a transceiver module and a rotating device. The transceiver module generates an electromagnetic (EM) field using an antenna. The rotating device includes N transponders arranged such that each of the N transponders passes through the EM field during one revolution of the rotating device. Each of the N transponders damps the EM field when passing through the EM field. The transceiver module determines a rotational speed of the rotating device based on a number of times the EM field is damped during a period. N is an integer greater than or equal to 1. 
         [0008]    A method comprises generating an electromagnetic (EM) field using an antenna and determining a rotational speed of a rotating device based on a number of times the EM field is damped during a period. The rotating device includes N transponders arranged such that each of the N transponders passes through the EM field during one revolution of the rotating device. Each of the N transponders damps the EM field when passing through the EM field. N is an integer greater than or equal to 1. 
         [0009]    Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0011]      FIG. 1  is a functional block diagram of a radio-frequency identification (RFID) system according to the present disclosure; 
           [0012]      FIG. 2  illustrates modification of a transmitted field in the RFID system due to a location of a transponder according to the present disclosure; 
           [0013]      FIG. 3  is a functional block diagram of a vehicle system according to the present disclosure; 
           [0014]      FIG. 4  is a functional block diagram of the RFID system integrated with an engine control module according to the present disclosure; 
           [0015]      FIG. 5  illustrates a method for determining a rotational speed and position of a rotating device according to the present disclosure; 
           [0016]      FIG. 6  illustrates a method for determining a rotational speed and position of the rotating device using varying field strengths according to the present disclosure; and 
           [0017]      FIG. 7  illustrates a method for determining a rotational speed and position of the rotating device that includes deactivating a transponder according to the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The following description is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical or. It should be understood that steps within a method may be executed in different order without altering the principles of the present disclosure. 
         [0019]    As used herein, the term module refers to an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. 
         [0020]    Typically, an engine control system determines a position of a rotating device (e.g., a crankshaft) using pattern recognition when the rotating device is rotating. A speed and position determination system of the present disclosure may determine the position of the rotating device when the rotating device is stationary. The speed and position determination system may include an antenna that reads data from one or more transponders arranged along the perimeter of the rotating device when the rotating device is stationary. Accordingly, the speed and position determination system may determine the position of the rotating device based on which of the transponders is read. 
         [0021]    The transponders may damp a field transmitted by the antenna when the transponders move past the antenna. Accordingly, the speed and position determination system may determine the rotational speed of the rotating device based on a number of times the transponders dampen the field transmitted by the antenna during a period. 
         [0022]    Referring now to  FIG. 1 , a radio-frequency identification (RFID) system  10  includes a rotating device  12 , transponders  14 , an antenna  16 , and a transceiver module  18 . The rotating device  12  may rotate about an axle  20 . The transponders  14  may be connected to the rotating device  12 . For example, the transponders  14  may be arranged near a perimeter of the rotating device  12 . 
         [0023]    The RFID system  10  may be included in a vehicle system. Accordingly, the rotating device  12  may be a component of the vehicle system that rotates. For example only, the rotating device  12  may be one of a flywheel, a flex plate, a component connected to a camshaft, and an output shaft. While the RFID system  10  is described as being included in the vehicle system, the RFID system  10  may be used generally to measure the speed and position of rotating devices in other systems. 
         [0024]    The transceiver module  18  may transmit signals (e.g., RF carrier signals) to the transponders  14  via the antenna  16 . Each of the transponders  14  may include a transponder antenna (not shown) that receives the transmitted signals. The transmitted signals may hereinafter be referred to as a transmitted “field.” The transponder antennas may absorb energy from the field transmitted by the antenna  16 . 
         [0025]    The transponders  14  may include memory that stores transponder data. For example, transponder data may include unique identification (ID) numbers. The transponders  14  may transmit the transponder data via the transponder antennas when the transponders  14  absorb a sufficient amount of energy from the field transmitted by the antenna  16 . The transceiver module  18  may receive the transponder data via the antenna  16 . Transponders that have received a sufficient amount of energy to transmit the transponder data may be referred to as “activated transponders.” Transponders that have not received a sufficient amount of energy to transmit the transponder data may be referred to as “inactive transponders.” In some implementations, the transponders  14  may be passive transponders. In other implementations, the transponders  14  may include a power source for transmitting the transponder data. The transponders  14  may operate at various frequencies (e.g., 125 kHz). 
         [0026]    The antenna  16  may be positioned to receive the transponder data from each of the transponders  14  as the rotating device  12  rotates about the axle  20 . For example, the transceiver module  18  may transmit/receive transponder data to/from the transponders  14  within a limited area  22 , hereinafter referred to as a “detection area  22 .” The transceiver module  18  may receive transponder data from one or more transponders  14  at the same time when the one or more transponders  14  are within the detection area  22 . 
         [0027]    The speed and position determination system may determine a position of the rotating device  12  based on which transponders  14  are read in the detection area  22 . For example, the speed and position determination system may determine the position of the rotating device  12  based on one or more unique IDs received from the transponders  14  in the detection area  22 . The speed and position determination system may include a table that relates the position of the rotating device  12  to one or more unique ID numbers. 
         [0028]    The transponders  14  may modify the field transmitted by the antenna  16  when the transponders  14  move through the detection area  22 . The field transmitted by the antenna  16  may be damped when the transponders  14  move through the detection area  22 . The transponders  14  may not absorb a sufficient amount of energy from the field transmitted by the antenna  16  to be activated when moving through the detection area  22 . Accordingly, the transponders  14  may not transmit the transponder data when the rotating device  12  is rotating. 
         [0029]    Referring now to  FIG. 2 , the graph illustrates variations in the field transmitted by the antenna  16  based on a position of a transponder  14  relative to the antenna  16 . The transceiver module  18  may detect when the transponder  14  damps the field transmitted by the antenna  16 . For example, the transceiver module  18  may detect when the field is damped based on a voltage induced in the antenna  16 . 
         [0030]    Strength of the field may be at a maximum when the transponder  14  is outside of the detection area  22 . The field may be damped to less than the maximum when the transponder  14  enters the detection area  22 . Strength of the field may return to the maximum when the transponder  14  moves outside of the detection area  22 . The speed and position determination system may determine a rotational speed of the rotating device  12  based on a number of times the field is damped during a period. 
         [0031]    Referring now to  FIG. 3 , an exemplary vehicle system  100  includes an engine  102  that drives a transmission  105  via a crankshaft (not shown). While a spark ignition engine is illustrated, other engines are contemplated. For example only, compression ignition engines and homogenous charge compression ignition (HCCI) engines are also contemplated. An engine control module (ECM)  103  communicates with components of the vehicle system  100 . The components may include the engine  102 , sensors, and actuators. The ECM  103  may include the transceiver module  18 . Accordingly, the ECM  103  may implement the speed and position determination system in the vehicle system  100 . 
         [0032]    The ECM  103  may communicate with a key/ignition sensor  104 . The key/ignition sensor  104  may determine whether a key is inserted into the vehicle and/or whether the engine  102  has been started. The ECM  103  may actuate a throttle  106  to regulate airflow into an intake manifold  108 . Air within the intake manifold  108  is distributed into cylinders  110 . The ECM  103  actuates fuel injectors  112  to inject fuel into the cylinders  110 . The ECM  103  may actuate spark plugs  114  to ignite an air/fuel mixture in the cylinders  110 . Alternatively, the air/fuel mixture may be ignited by compression in a compression ignition engine. While four cylinders  110  of the engine  102  are shown, the engine  102  may include more or less than four cylinders  110 . 
         [0033]    The crankshaft rotates at engine speed or a rate that is proportional to the engine speed. A crankshaft sensor  116  generates a crankshaft signal that indicates rotation of the crankshaft. For example, the crankshaft signal may indicate rotation of a gear connected to the crankshaft. The crankshaft sensor  116  may include the antenna  16 . The gear connected to the crankshaft may include the transponders  14 . Accordingly, the ECM  103  may determine the rotational speed of the crankshaft and the position of the crankshaft when the crankshaft sensor  116  includes the antenna  16  and the gear connected to the crankshaft includes the transponders  14 . 
         [0034]    An intake camshaft  117  regulates a position of an intake valve  120  to enable air to enter the cylinder  110 . Combustion exhaust within the cylinder  110  is forced out through an exhaust manifold  122  when an exhaust valve  124  is in an open position. An exhaust camshaft (not shown) regulates a position of the exhaust valve  124 . Although single intake and exhaust valves  120 ,  124  are illustrated, the engine  102  may include multiple intake and exhaust valves  120 ,  124  per cylinder  110 . 
         [0035]    The intake camshaft  117  and the exhaust camshaft may rotate at engine speed or a rate that is proportional to the engine speed. A camshaft sensor  118  may generate a camshaft signal that indicates rotation of the intake camshaft  117  and/or the exhaust camshaft. For example, the camshaft signal may indicate rotation of a gear connected to the intake camshaft  117 . The camshaft sensor  118  may include the antenna  16 . The gear connected to the intake camshaft  117  may include the transponders  14 . Accordingly, the ECM  103  may determine the rotational speed of the intake camshaft  117  and the position of the intake camshaft  117  when the camshaft sensor  118  includes the antenna  16  and the gear connected to the intake camshaft  117  includes the transponders  14 . 
         [0036]    Drive torque produced by the engine  102  may drive wheels  126  via an output shaft  128 . A vehicle speed sensor  130  may generate a vehicle speed signal that indicates rotation of the output shaft  128 . The vehicle speed sensor  130  may include the antenna  16 . The output shaft  128  may include the transponders  14 . Accordingly, the ECM  103  may determine the rotational speed of the output shaft  128  and the position of the output shaft  128  when the vehicle speed sensor  130  includes the antenna  16  and the output shaft  128  includes the transponders  14 . The ECM  103  may determine a speed of the vehicle based on the vehicle speed signal. 
         [0037]    The vehicle system  100  may include one or more wheel speed sensors  132  that generate wheel speed signals. The wheel speed signals may indicate rotation of components connected to the wheels  126 . The wheel speed sensors  132  may each include the antenna  16 . The components connected to the wheels  126  may include the transponders  14 . Accordingly, the ECM  103  may determine the position of the wheels  126  and the rotational speed of the wheels  126  when the wheel speed sensors  132  include the antenna  16  and the components connected to the wheels  126  include the transponders  14 . The ECM  103  may determine the speed of the vehicle based on the wheel speed signals. 
         [0038]    Referring now to  FIG. 4 , the ECM  103  may include the transceiver module  18 , a starting module  140 , a position determination module  142 , and a speed determination module  144 . The transceiver module  18  may transmit/receive signals to/from the transponders  14  via the antenna  16 . The starting module  140  may determine when the engine  102  starts. The position determination module  142  may determine the position of the rotating device  12 . The speed determination module  144  may determine the rotational speed of the rotating device  12 . 
         [0039]    The rotating device  12  may include a component of the vehicle system  100  that rotates. For example, the rotating device  12  may include at least one of the gear connected to the crankshaft, the gear connected to the intake camshaft  117 , the output shaft  128 , and the components connected to the wheels  126 . While the speed and position determination system is described in the vehicle system  100 , the speed and position determination system may be generally applicable to systems that measure rotational speed of rotating devices. 
         [0040]    The speed and position determination system may be implemented when the engine  102  is turned on. The starting module  140  may determine that the engine  102  is turned on based on signals received from the key/ignition sensor  104 . The rotating device  12  may be stationary when the engine  102  is started. Accordingly, the position determination module  142  may determine an initial position of the rotating device  12  when the engine  102  is started. The position determination module  142  may determine the initial position of the rotating device  12  based on which transponders  14  are read when the engine  102  is started. For example, the position determination module  142  may determine the position of the rotating device  12  based on one or more unique IDs received from the transponders  14  in the detection area  22  when the engine  102  is started. 
         [0041]    The position determination module  142  may include calibration memory that relates positions of the rotating device  12  to unique ID numbers stored in each of the transponders  14 . For example, if 10 transponders  14  are equally spaced along the perimeter of the rotating device  12 , each of the 10 transponders  14  may correspond to a 36 degree slice of the rotating device  12 . Accordingly, the position determination module  142  may determine which 36 degree slice is in the detection area  22  based on the unique ID of the transponder  14  in the detection area  22 . 
         [0042]    The detection area  22  may include more than one transponder  14  when the engine  102  is started. The position determination module  142  may determine the position of the rotating device  12  based on more than one unique ID number when more than one transponder  14  is in the detection area  22  when the engine  102  is started. The position determination module  142  may determine the initial position of the rotating device  12  with greater resolution when the detection area  22  includes more than one transponder  14 . For example, when the detection area  22  includes two transponders  14 , the position determination module  142  may determine that the position of the rotating device  12  is between the two positions corresponding to the two transponders  14 . The position determination module  142  may determine the position of the rotating device  12  based on one or more unique IDs using averaging algorithms and/or fuzzy logic. 
         [0043]    In some implementations, the transponders  14  may be arranged along the perimeter of the rotating device  12  so that at least one transponder is in the detection area  22  at all times. Accordingly, the position determination module  142  may determine the position of the rotating device  12  at any angle of rotation. In other implementations, the transponders  14  may be arranged along the perimeter of the rotating device  12  so that more than one transponder  14  is in the detection area at all times. 
         [0044]    While the position determination module  142  is described as determining the position of the rotating device  12  when the engine  102  is started, the position determination module  142  may also determine the position of the rotating device  12  when the engine  102  is stopped or stalled. The position determination module  142  may store the position of the rotating device  12  when the engine  102  is off. The ECM  103  may retrieve the stored position when the engine  102  is started. 
         [0045]    The speed determination module  144  may determine the rotational speed of the rotating device  12  based on a number of times the field transmitted by the antenna  16  is damped during a period. For example only, the speed determination module  144  may detect the field damped 10 times per revolution of the rotating device  12  when the rotating device  12  includes 10 transponders  14 . 
         [0046]    In some implementations, the transceiver module  18  may change the strength of the field transmitted from the antenna  16 . The transceiver module  18  may transmit a stronger field to activate the transponders  14  and read the transponder data from the activated transponders. Accordingly, the transceiver module  18  may transmit the stronger field to determine the position of the rotating device  12  when the engine  102  is started. Activated transponders may react differently to the field transmitted by the antenna  16  than inactive transponders. For example, activated transponders may transmit transponder data when the rotating device  12  is rotating, instead of damping the field. The activated transponders may not transmit transponder data when moving through a weaker field, however the activated transponders may still damp the weaker field. Accordingly, the transceiver module  18  may transmit a weaker field when the rotating device  12  is rotating, so the activated transponders behave similarly to the inactive transponders when the rotating device  12  is rotating. 
         [0047]    In some implementations, the transceiver module  18  may apply the same magnetic field strength when the rotating device  12  is stationary and when the rotating device  12  is rotating. To prevent the activated transponders from transmitting transponder data when moving through the field, the transceiver module  18  may send a command to the activated transponders to deactivate the activated transponders. For example only, the activated transponders may be inactive transponders after the transceiver module  18  sends the command to deactivate the activated transponders. Accordingly, the activated transponders that receive the command to deactivate will behave similarly to the transponders that were not activated when the engine  102  was started. In other words, the activated transponders that were deactivated may not transmit transponder data, but may damp the field. 
         [0048]    In some implementations, the speed and position determination system may implement pattern recognition to determine the position of the rotating device  12  while the rotating device  12  is rotating. The transponders  14  may be selectively arranged on the rotating device  12  to implement pattern recognition. For example, the transponders  14  may be arranged so that a gap between two of the transponders  14  is larger than a gap between each of the other transponders  14 . Accordingly, the ECM  103  may determine the position of the rotating device  12  while the rotating device  12  is rotating based on a longer time lapse that occurs between the transponders  14  that are separated by the larger gap. 
         [0049]    Referring now to  FIG. 5 , a method  200  for determining a rotational speed and position of a rotating device starts in step  201 . In step  202 , the starting module  140  determines that the engine  102  is started. In step  204 , the position determination module  142  acquires transponder data. In step  206 , the position determination module  142  determines the initial position of the rotating device  12 . 
         [0050]    In step  208 , the speed determination module  144  detects field damping when the rotating device  12  is rotating. In step  210 , the speed determination module  144  determines the rotational speed and position of the rotating device  12 . In step  212 , the ECM  103  determines whether the engine  102  has stopped. If the result of step  212  is false, the method  200  continues with step  208 . If the result of step  212  is true, the method  200  continues with step  214 . The method  200  ends in step  214 . 
         [0051]    Referring now to  FIG. 6 , a method  300  for determining a rotational speed and position of a rotating device using varying field strengths starts in step  301 . In step  302 , the starting module  140  determines that the engine  102  is started. In step  304 , transceiver module  18  transmits a strong field to activate the transponders  14  in the detection area  22 . In step  306 , the position determination module  142  acquires transponder data. In step  308 , the position determination module  142  determines the initial position of the rotating device  12 . In step  310 , the transceiver module  18  decreases the strength of the field when the rotating device  12  starts rotating. 
         [0052]    In step  312 , the speed determination module  144  detects field damping when the rotating device  12  is rotating. In step  314 , the speed determination module  144  determines the rotational speed and position of the rotating device  12 . In step  316 , the ECM  103  determines whether the engine  102  has stopped. If the result of step  316  is false, the method  300  continues with step  312 . If the result of step  316  is true, the method  300  continues with step  318 . The method  300  ends in step  318 . 
         [0053]    Referring now to  FIG. 7 , a method  400  for determining a rotational speed and position of a rotating device that includes deactivating a transponder starts in step  401 . In step  402 , the starting module  140  determines that the engine  102  is started. In step  404 , the position determination module  142  acquires transponder data. In step  406 , the position determination module  142  determines the initial position of the rotating device  12 . 
         [0054]    In step  408 , the transceiver module  18  deactivates the activated transponders. In step  410 , the speed determination module  144  detects field damping when the rotating device  12  is rotating. In step  412 , the speed determination module  144  determines the rotational speed and position of the rotating device  12 . In step  414 , the ECM  103  determines whether the engine  102  has stopped. If the result of step  414  is false, the method  400  continues with step  410 . If the result of step  414  is true, the method  400  continues with step  416 . The method  400  ends in step  416 . 
         [0055]    The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification, and the following claims.