Patent Publication Number: US-11650107-B2

Title: Temperature measurement system and method of calibration thereof

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is a divisional of U.S. Non-Provisional patent application Ser. No. 16/285,593, entitled “TEMPERATURE MEASUREMENT SYSTEM AND METHOD OF CALIBRATION THEREOF”, and filed on Feb. 26, 2019. The entire contents of the above-listed application are hereby incorporated by reference for all purposes. 
    
    
     TECHNICAL FIELD 
     The subject matter of the embodiments described herein is directed toward a temperature measurement system, and more particularly to a temperature measurement system and a method for calibration thereof. 
     BACKGROUND 
     Conventional temperature measurement systems typically include at least one temperature sensor used to measure or estimate a temperature of a desired component or system. Commonly, a temperature dependent resistor, commonly referred to as a thermistor, is employed as the temperature sensor in the temperature measurement system. Commercially available thermistors, however, typically have resistance versus temperature properties which deviate significantly from the nominal values thereof provided by the manufacturer of the thermistor. This deviation in resistance versus temperature properties can result in a substantial shift or skewing of an operation or response of the desired component or system in view of the different value of resistance measured for any given temperature. Error in the measured resistance can result in a different response from the desired component or system than is desired where the desired component or system is programmed to respond in accordance with a particular algorithm or value from a look-up table. 
     Where the desired component or system is assembled in mass production such as in vehicle systems, for example, a significant variation in resistance versus temperature properties of the commercially available thermistors can result in a prohibitively wide variation in the response of the vehicle system or, in a worst-case scenario, the vehicle system becoming completely dysfunctional. Ideally, a calibration of each and every thermistor within the temperature measurement system would occur as a final step in the manufacture of the vehicle system to obtain highly accurate temperature sensing. However, such calibration would be extremely expensive and require complex logistics. 
     Accordingly, it would be desirable to develop a temperature measurement system and a method of calibration thereof which improves accuracy of the temperature measurement system while minimizing cost and complexity. 
     SUMMARY 
     In concordance and agreement with the present disclosure, a temperature measurement system and a method of calibration thereof which improves accuracy of the temperature measurement system while minimizing cost and complexity, has surprisingly been discovered. 
     In an embodiment, a temperature measurement system of a vehicle, comprises: a controller in electrical communication with at least one temperature sensor, wherein the temperature measurement system is calibratable based upon a comparison of a plurality of temperatures at least one of measured and estimated by the at least one temperature sensor after a predetermined time. 
     In another embodiment, a temperature measurement system of a vehicle, comprises: a controller in electrical communication with a memory for storing data; a first temperature sensor in electrical communication with the controller, wherein the first temperature sensor is configured to transmit a measured voltage difference representative of a temperature of a first location to the controller; and a second temperature sensor in electrical communication with the controller, wherein the second temperature sensor is configured to transmit a temperature of a second location to the controller, wherein the controller is configured to determine the temperature of the first location from the measured voltage difference using a determination method which is calibratable based upon a comparison of the temperature of the first location to the temperature of the second location. 
     In yet another embodiment, a method of temperature measurement system calibration, the method comprises the steps of: providing a temperature measurement system including a controller, a memory for storing data, a first temperature sensor, and a second temperature sensor, wherein the controller is in electrical communication with the memory for storing data, the first temperature sensor, and the second temperature sensor; and calibrating the temperature measurement system based upon a comparison of a temperature of a first location and a temperature of a second location, wherein the temperature of at least one of the first location and the second location is determined after a predetermined time. 
     As aspects of certain embodiments, at least one of the temperatures is at least one of measured and estimated by the at least one temperature sensor after a predetermined time from an end of operation of the vehicle. 
     As aspects of certain embodiments, the at least one temperature sensor at least one of measures and estimates a temperature of a desired location. 
     As aspects of certain embodiments, the at least one temperature sensor at least one of measures and estimates a temperature of an input location. 
     As aspects of certain embodiments, the determination method of the temperature measurement system determines the temperature of the first location based upon at least one of a tolerance band and a function stored in the memory for storing data and the measured voltage difference transmitted by the first temperature sensor. 
     As aspects of certain embodiments, the determination method of the temperature measurement system determines the temperature of the first location based upon a look-up table stored in the memory for storing data and the measured voltage difference transmitted by the first temperature sensor. 
     As aspects of certain embodiments, the first temperature sensor is a thermistor configured to transmit a measured voltage difference to the controller. 
     As aspects of certain embodiments, the first location is one of a component and fluid of the vehicle of which a direct temperature measurement is unobtainable by the first temperature sensor. 
     As aspects of certain embodiments, the second location is one of a component and fluid of the vehicle of which a direct temperature measurement is obtainable by the second temperature sensor. 
     As aspects of certain embodiments, the method further comprises the step of: determining the temperature of the first location based upon at least one of a tolerance band and a function stored in the memory for storing data and the measured voltage difference transmitted by the first temperature sensor. 
     As aspects of certain embodiments, the method further. comprises the step of: determining the temperature of the first location based upon a look-up table stored in the memory for storing data and the measured voltage difference transmitted by the first temperature sensor. 
     As aspects of certain embodiments, the step of calibrating the temperature measurement system based upon a comparison of a temperature of a first location and a temperature of a second location includes calibrating a determination method from which the temperature of the first location is determined. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above, as well as other advantages of the present embodiments, will become readily apparent to those skilled in the art from the following detailed description when considered in the light of the accompanying drawings in which: 
         FIG.  1    is a graphical representation of a vehicle including a temperature measurement system according to an embodiment of the present subject matter; and 
         FIG.  2    is a schematic flow diagram of a method for calibration of the temperature measurement system shown in  FIG.  1    according to an embodiment of the subject disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     It is to be understood that the preferred embodiments may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in herein. Hence, specific dimensions, directions or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting. 
       FIG.  1    depicts a vehicle  10  according to an embodiment of the present subject matter. The vehicle  10  may be any vehicle type as desired such as a conventional fuel-powered vehicle, an electric vehicle, and an electric-hybrid vehicle, for example. The vehicle  10  includes a temperature measurement system  12 . In certain embodiments, the temperature measurement system  12  includes a controller or microcontroller  14 , a first temperature sensor  16  for measuring and/or estimating a temperature T 1  of a desired location  18  (e.g. a component or fluid of the vehicle  10  which is impossible or impracticable to obtain a direct temperature measurement), a memory  20  for storing data, and a second temperature sensor  24  for measuring a temperature T 2  of an input location  26  (e.g. a component or fluid of the vehicle  10 ). It is understood that additional temperature sensors  24  may be employed for measuring temperatures at a plurality of input locations  26 . More particularly, the desired location  18  may be a clutch assembly of a rear drive unit, differential gear assembly, and the like, for example. Further, the input location  26  may be a vehicle engine, an engine fluid, a vehicle transmission, a transmission fluid, ambient air, and the like, for example. 
     The temperature measurement system  12  is configured to allow various components, modules, systems, and applications of the vehicle  10  to communicate with each other. Various types of controllers or microcontrollers  14  may be employed in the vehicle  10  such as a controller area network (CAN) system, for example. In the embodiment shown, the controller  14  is electrically connected to at least one of the first temperature sensor  16 , the memory  20 , and the second temperature sensor  24  of the temperature measurement system  12  to allow communication thereamong. 
     In one embodiment, the first temperature sensor  16  is thermistor. Various types of thermistors may be employed as the first temperature sensor  16  such as a negative temperature coefficient (NTC) thermistor and a positive temperature coefficient (PTC) thermistor, for example. With an NTC thermistor, when the temperature increases, resistance of the NTC thermistor decreases. Conversely, when temperature decreases, resistance of the NTC thermistor increases. On the other hand with a PTC thermistor, when temperature increases, the resistance of the PTC thermistor increases, and when temperature decreases, resistance of the PTC thermistor decreases. 
     Unlike other temperature sensors, the first temperature sensor  16  is a nonlinear thermistor, meaning a relationship between a resistance and a temperature is not a 1:1 ratio. As such, the temperature to resistance values plotted on a graph representing such relationship form a curve rather than a straight line. It is understood that the first temperature sensor  16  may have a variety of shapes and sizes such as a disk, chip, bead, rod, surface-mounted, for example. The first temperature sensor  16  can also be encapsulated in epoxy resin, glass, baked-on phenolic, and painted, if desired. 
     In the embodiment shown, the first temperature sensor  16  is employed to at least one of measure and estimate the temperature T 1  of the desired location  18 . The first temperature sensor  16  has a minimal amount of electrical current  25  (also commonly referred to as a bias current) flowing therethrough. The controller  14  is configured to cause an electrical source  27  to transmit the electrical current  25  to the first temperature sensor  16 . The first temperature sensor  16  has a resistance R 1  associated with the temperature T 1  of the desired location  18 . The electrical current  25  flowing through the first temperature sensor  16  converts the resistance R 1  of the first temperature sensor  16  to a measured voltage difference V 1  across terminals of the first temperature sensor  16 . The measured voltage difference V 1  is then transmitted from the first temperature sensor  16  to the controller  14 . In certain embodiments, the controller  14  determines a temperature T 1  of the desired location  18  based upon at least one determination method such as using the measured voltage difference V 1  and a tolerance band or function of the first temperature sensor  16  stored within the memory  20  of the temperature measurement system  12 , for example. The first temperature sensor  16  is initially configured to operate within a certain tolerance band or function. A relationship between voltage and resistance is known, and may be calculated by utilizing a look-up table  28 , or other mathematical relationship therebetween. As such, in certain other embodiments, the determination method of the controller  14  utilizes the look-up table  28  stored in the memory  20  to determine the temperature T 1  of the desired location  18  based upon the measured voltage difference V 1  of the first temperature sensor  16 . 
     To improve accuracy of measuring or estimating the temperature T 1  of the desired location, the determination method of the temperature measurement system  12 , from which the temperature T 1  is determined, is calibratable. In certain embodiments, the determination method, using the tolerance band or function of the first temperature sensor  16  stored within the memory  20  of the temperature measurement system  12  or look-up table  28 , is calibratable based upon thermal dynamics of the vehicle  10 . 
     Referring now to  FIG.  2   , a flow diagram showing a method of calibration  100  for the temperature measurement system  12 . At step  102 , the temperature measurement system  12 , during an operation of the vehicle  10 , causes the electrical source  27  to transmit the electrical current  25  to the first temperature sensor  16  and flow therethrough, which generates the resistance R 1 . At step  104 , the resistance R 1  of the first temperature sensor  16  is then converted to the measured voltage difference V 1  across the terminals of the first temperature sensor  16  representative of the temperature T 1  of the desired location  18 . At step  106 , the measured voltage difference V 1  is then transmitted to the controller  14  of the temperature measurement system  12 . At step  108 , the controller  14 , using the determination method, determines the temperature T 1  of the desired location  18 . In one embodiment, the temperature T 1  of the desired location  18  is based upon the tolerance band or function of the measured voltage difference V 1  of the first temperature sensor  16 . In certain other embodiments, the temperature measurement system  12  utilizes the lookup table  28  stored in the memory  20  to determine the temperature T 1  of the desired location  18  based upon the measured voltage difference V 1  of the first temperature sensor  16 . At step  110 , the temperature T 1  of the desired location  18  is stored in the memory  20  of the temperature measurement system  12 . 
     At step  112 , an operation of the vehicle  10  is ended. At step  114 , the temperature measurement system  12 , after a first predetermined time from an end of the operation of the vehicle  10 , causes the second temperature sensor  24  to measure a control temperature T c  of the input location  26 . At step  116 , the control temperature T c  of the input location  26  is stored in the memory  20  of the temperature measurement system  12 . At step  118 , the temperature measurement system  12 , after a second predetermined time from the end of the operation of the vehicle  10 , causes the electrical source  27  to transmit the electrical current  25  to the first temperature sensor  16  and flow therethrough. It should be appreciated that the steps to measure the control temperature T c  of the input location  26  and the steps to determine the temperature T 2  of the desired location  18  may be conducted substantially simultaneously, chronologically, or vice versa, by the temperature measurement system  12 , as desired. In one example, each of the first and second predetermined times from the end of the operation of the vehicle  10  is of such a length of time to allow convergence of temperatures over an entirety of the vehicle  10 , in other words, to allow the vehicle  10  to reach a steady state. In another example, at least one of the first and second predetermined times from the end of the operation of the vehicle  10  is longer than 4-5× a longest time constant of the vehicle  10 . It is understood, however, that each of the first and second predetermined times can be any length of time, as desired. It is further understood that the first and second predetermined times may be substantially the same, the first predetermined time may be shorter than the second predetermined time, or the first predetermined time may be longer than the second predetermined time. 
     The first temperature sensor  16  has a resistance R 2  associated with a temperature T 2  of the desired location  18 . At step  120 , the resistance R 2  is then converted to a measured voltage difference V 2  across the terminals of the first temperature sensor  16  representative of the temperature T 2  of the desired location  18 . At step  122 , the measured voltage difference V 2  is then transmitted to the controller  14  of the temperature measurement system  12 . At step  124 , the controller  14 , using the determination method, determines the temperature T 2  of the desired location  18  based upon the tolerance band and/or function of the measured voltage difference V 2  of the first temperature sensor  16 , or by utilizing the look-up table  28 , or other mathematical relationship therebetween. 
     At step  126 , the temperature T 2  of the desired location  18  is then compared to the control temperature T c  of the input location  26 . When the temperature T 2  of the desired location  18  is not substantially equal to the control temperature T c  of the input location  26 , the determination method of the temperature measurement system  12  is calibrated at step  128 . It should be appreciated that the temperature T 2  of the desired location  18  may be permitted to differ from the control temperature T c  of the input location  26  by a certain amount or percentage without requiring a calibration of the temperature measurement system  12 . 
     More particularly, at step  128 , the determination method using the tolerance band and/or function of the measured voltage difference V 1 , or look-up table  28 , or other mathematical relationship therebetween, is calibrated so that the temperature T 2  of the desired location  18  determined therefrom would be substantially equal to the control temperature T c  of the input location  26 . In one embodiment, the controller  14 , based upon the difference between T 2  and T c , updates which tolerance band or function of the first temperature sensor  16  is utilized by the determination method to determine or calculate the temperature T 2  of the desired location  18  when the measured voltage difference is received from the first temperature sensor  16 . In another embodiment, the controller  14 , based upon the difference between T 2  and T c , updates which look-up table  28  is utilized by the determination method to determine or calculate the temperature T 2  of the desired location  18  when the measured voltage difference is received from the first temperature sensor  16 . Accordingly, the control temperature T c  of the input location  26  when the vehicle  10  has reached steady state is a baseline utilized to adjust and calibrate the determination method from which the temperature T 2  of the desired location  18  is determined, thereby minimizing error and improving an accuracy of the temperature measurement system  12 . 
     It should be appreciated that any number of tolerance bands, functions and look-up tables may be employed and stored within the memory  20  of the temperature measurement system  12 . It should also be appreciated that the temperature measurement system  12  may only employ a single tolerance band, function, or look-up table, which is continuously calibrated and stored within the memory  20 . 
     In accordance with the provisions of the patent statutes, the present subject matter has been described in what is considered to represent its preferred embodiments. However, it should be noted that the subject matter can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.