Engine temperature estimation based on a thermal model

Abstract

Vehicle that includes: a power source configured to supply electrical energy; a motor having a motor temperature and comprising a plurality of motor regions including a volume of oil used in the motor, a flux-generating region, a non-flux-generating region, and a region of stator windings, each of the plurality of motor regions having a respective regional temperature, and wherein the motor is configured to receive electrical energy from the power source and to generate rotational motion from the received electrical energy; and a computing device comprising a thermal model that estimates each of the regional temperatures, the computing device configured to estimate the engine temperature in real time based at least in part on the regional temperatures estimated by the engine thermal model; wherein the computing device is configured to estimate the engine temperature such that the engine temperature is the highest of the estimated regional temperatures or the lowest of the estimated regional temperatures or an average of the estimated regional temperatures, or wherein the computing device is configured to weight the estimated regional temperatures of one or more engine regions more heavily than the estimated regional temperatures of other engine regions and consequently estimate the engine temperature according to the weight given to each engine region; wherein the thermal model includes a plurality of nodes and at least one thermal resistor; wherein each node represents a region of the motor regions, and wherein each thermal resistor represents a heat transfer path between at least two of the nodes.

Description

TECHNICAL FIELD

[0001] The invention relates generally to estimating an engine temperature based on a thermal model and more particularly to a vehicle having a computing device including such a thermal model. BACKGROUND

[0002] A hybrid or battery-powered vehicle may use a motor that generates torque to propel the vehicle. The motor may generate rotational motion from electrical energy (e.g., direct current or alternating current). The rotational motion from the motor may be transferred to the vehicle's wheels, and the torque delivered to the wheels may be proportional to the rotational motion of the motor.

[0003] DE 10 2008 040 725 A1 describes a method for determining the rotor temperature of a permanent magnet synchronous machine, in which a first estimated value for the rotor temperature is determined as a function of a remanent flux density in a permanent magnet contained in the rotor, which, in order to make the rotor temperature determination more precise, is fed at least partially to a Kalman filter of a thermal model used to determine a second rotor temperature estimated value.

[0004] WO 2003 / 081764 A discloses another method for determining the rotor temperature of a permanent magnet synchronous machine using a temperature model. SUMMARY

[0005] The invention is based on the object of specifying a vehicle of the type mentioned above in which the engine temperature of the vehicle engine as a whole can be estimated as accurately as possible in real time.

[0006] According to the invention, this object is achieved by a vehicle having the features of claim 1. Preferred embodiments of the vehicle according to the invention emerge from the subclaims, the present description and the drawing.

[0007] The vehicle according to the invention comprises a power source designed to supply electrical energy, an engine having an engine temperature and a plurality of engine regions representing an oil volume used in the engine, a flow-generating region, a non-flow-generating region, and a region of stator windings, wherein each of the plurality of motor regions has a respective regional temperature, and wherein the motor is configured to receive electrical energy from the power source and to generate a rotary motion from the received electrical energy, and a computing device comprising a thermal model that estimates each of the regional temperatures, wherein the computing device is configured to estimate the engine temperature in real time based at least in part on the regional temperatures estimated by the thermal model of the engine, wherein the computing device is configured to estimate the engine temperature such that the engine temperature is the highest of the estimated regional temperatures, the lowest of the estimated regional temperatures, or an average of the estimated regional temperatures, or wherein the computing device is configured to weight the estimated regional temperatures of one or more engine regions more heavily than the estimated regional temperatures of other engine regions and thus estimate the engine temperature according to the weight given to each engine region,wherein the thermal model contains several nodes and at least one thermal resistance, wherein each node represents a region of the motor regions, and wherein each thermal resistor represents a heat transfer path between at least two of the nodes. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic drawing of an exemplary vehicle having an engine, a power source, and a computing device. Fig. Figure 2 is a schematic drawing of an example thermal model of a permanent magnet motor. Fig. Figure 3 is a schematic drawing of an example thermal model of an induction motor. Fig. Figure 4 is a flowchart of an example process that can be used to estimate the temperature of an engine. DETAILED DESCRIPTION

[0008] A vehicle is provided that is capable of estimating a temperature of, for example, an electric motor in real time based at least in part on a thermal model of the motor. The thermal model may be expressed as one or more energy balance equations that can be used by a computing device in the vehicle to accurately estimate the temperature of various regions of the motor. The computing device may further estimate the motor temperature based on the temperature at each region. The vehicle may take many different forms and include many and / or alternative components and features. Although an example vehicle is shown in the figures, the components depicted in the figures are not intended to be limiting. Indeed, additional or alternative components and / or implementations may be used.

[0009] With reference to Fig. 1, the vehicle 100 may include a power source 105, a motor 110, a computing device 115, and a storage device 120. The vehicle 100 may be any passenger or commercial vehicle, such as a hybrid electric vehicle, including a plug-in hybrid electric vehicle (PHEV) or an extended-range electric vehicle (EREV), a battery electric vehicle (BEV), a fuel cell vehicle, or the like.

[0010] The power source 105 may include any device, such as one or more batteries, configured to supply electrical energy to, for example, one or more components of the vehicle 100. The power source 105 may further include or be in electrical communication with a rectifier / inverter (not shown) configured to convert the electrical energy stored in the power source 105 from, for example, direct current (DC) energy to alternating current (AC) energy. The power source 105 may further be configured to receive and store electrical energy supplied, for example, by a generator. Thus, the rectifier / inverter may be configured to convert the AC energy supplied by the generator to DC energy for storage in the power source 105.

[0011] Motor 110 may include any device configured to convert electrical energy into rotary motion. Thus, motor 110 may be an induction motor, a permanent magnet motor, a synchronous reluctance motor, a separately excited wound rotor, etc. In any case, motor 110 may be configured to receive electrical energy from power source 105 either directly or via the rectifier / inverter and to generate torque in accordance with the received electrical energy. Vehicle 100 may include any number of motors 110.

[0012] In one possible implementation, the motor 110 may include a stator 125 and a rotor 130. The stator 125 may include any device that remains stationary relative to the rotor 130 during operation of the motor 110 and that generates an electromagnetic field using, for example, an electromagnet or a permanent magnet. The rotor 130 may include any device that rotates relative to the stator 125 during operation of the motor 110 to generate rotational motion and thus torque. Like the stator 125, the rotor 130 may generate an electromagnetic field using, for example, an electromagnet or a permanent magnet. If either the rotor 130 or the stator 125 includes an electromagnet, the electrical energy required to generate the electromagnetic field may come from the power source 105.The interaction of the electromagnetic fields of rotor 130 and stator 125 may cause rotor 130 to rotate relative to stator 125. Thus, the direction, speed, and output torque of motor 110 may be controlled based on the electrical energy supplied to rotor 130, stator 125, or both.

[0013] During operation, different regions of the motor 110 may generate and transfer heat at different rates. For example, the rotor 130 and / or the stator 125 may include flux-generating and non-flux-generating regions formed from a metal such as iron. Furthermore, the rotor 130 and / or the stator 125 may include windings formed from, for example, copper, which generate the magnetic field when supplied with electrical energy. The energy supplied to the rotor 130 and / or the stator 125, which causes the motor 110 to generate rotational motion, may also generate heat at different regions of the motor 110, and the heat generated in one region of the motor 110 may be transferred to another region of the motor 110 via a heat transfer path, for example, by convection or conduction. Cooling techniques may be applied to one or more regions (e.g.,Thermal loss regions) of the engine 110 may be applied to remove heat from various regions of the engine 110. As described below with reference to FIG. Fig. 2 and Fig. 3 in greater detail, the temperature of each motor 110 may be estimated in real time using a thermal model that takes into account the heat generated and dissipated (e.g., due to cooling) at various regions of the motor 110.

[0014] Computing device 115 may include any device configured to estimate the temperature of engine 110 in real time based at least in part on the thermal model of engine 110. For example, the thermal model may be expressed as one or more energy balance equations representing the temperature of each region of engine 110 represented in the thermal model. Computing device 115 may be configured to solve the energy balance equations to determine the temperature at each region. Computing device 115 may further determine a change in temperature in each region over time by solving the energy balance equation at each region at two or more time steps. Computing device 115 may estimate the temperature of engine 110 based on the temperature or the change in temperature over time in each region.

[0015] Each energy balance equation may be derived from the thermal model. In one possible implementation, the energy balance equations solved by the computing device 115 may be first-order differential equations. Each energy balance equation may consider the temperature at one or more regions, including regions of thermal loss, and one or more heat transfer paths associated with each region. As discussed below, each heat transfer path may be based on various physical properties of the components that make up the engine 110.

[0016] The temperature of each region represented in the thermal model may depend on the operating conditions of the motor 110. Accordingly, the computing device 115 may be configured to derive information about the operating conditions of the motor 110, for example, based on the speed, torque, or current generated by the motor 110. In one possible implementation, the computing device 115 may be configured to determine the speed and / or torque generated by the motor 110 based on the amount of electrical energy supplied to the motor 110 by the power source 105. The computing device 115 may further be configured to compensate for regions with thermal losses of the motor 110, for example, due to cooling techniques, when determining the temperature at each region represented in the thermal model.Consequently, the computing device 115 can determine the temperature at each region of the engine 110 represented in the thermal model from the operating conditions of the engine 110.

[0017] Computing device 115 may be configured to consider heat transfer distances between the various regions of engine 110 represented in the thermal model when solving the energy balance equation and estimating the temperature of engine 110. Heat transfer between regions of engine 110 may be caused by conduction, convection, or the like. Some example physical properties considered by computing device 115 may include the length, thermal conductivity, cross-sectional area, heat transfer coefficient, surface area, mass, and / or specific heat capacity of the materials used to form the various components of engine 110.Computing device 115 may be further configured to derive values ​​associated with the physical properties of the various regions of engine 110 or to access these values ​​from, for example, a lookup table stored in storage device 120, as discussed below. Computing device 115 may use these values ​​to solve the energy balance equation for each region of engine 110 represented in the thermal model.

[0018] Although in Fig. 1, only one computing device 115 is shown, the vehicle 100 may include any number of computing devices 115. The computing device 115 may generally utilize any of a number of computer operating systems and may include computer-executable instructions, where the instructions may be executed by one or more computing devices. Computer-executable instructions may be compiled from or interpreted from computer programs generated using a variety of programming languages ​​and / or technologies, including, without limitation, either independently or in combination, Java™, C, C++, Visual Basic, Java Script, Perl, etc. In general, a processor (e.g., a microprocessor) receives instructions from, for example, memory, a computer-readable medium, etc.and executes those instructions, thereby performing one or more processes that include one or more of the processes described herein. Such instructions and other data may be stored and transmitted using a variety of computer-readable media.

[0019] A computer-readable medium (also referred to as a processor-readable medium) includes any non-transitory (e.g., tangible) medium that participates in the provision of data (e.g., instructions) that can be read by a computer (e.g., by a processor of a computer). Such a medium can take many forms, including, but not limited to, non-volatile media and volatile media. Non-volatile media can include, for example, optical or magnetic disks and other persistent storage. Volatile media can include, for example, dynamic random access memory (DRAM), which can constitute main memory.Such instructions may be transmitted by one or more transmission media, including coaxial cable, copper wire, and fiber optics, including the lines that form a system bus coupled to a processor of a computer. Some forms of computer-readable media include, for example, a floppy disk, a flexible disk, a hard disk, magnetic tape, any other magnetic medium, a CD-ROM, a DVD, any other optical medium, punched cards, paper tape, any other physical medium with hole patterns, a RAM, a PROM, an EPROM, a flash EEPROM, any other memory chip or cartridge, or any other medium from which a computer can read.

[0020] Storage device 120 may include any device configured to store information such as the energy balance equations, information that may be used by computing device 115 to solve one or more of the energy balance equations, and / or any other information that may be used by computing device 115. Like computing device 115, storage device 120 may include any non-volatile and / or volatile media. The information stored in storage device 120 may be in one or more lookup tables.For example, the storage device 120 may store one or more lookup tables containing information regarding the temperature change of various heat-generating or heat-losing regions of the engine 110 given various operating conditions, the physical properties of the components of the engine 110, etc. The storage device 120 may also store other information in the lookup tables, and although only one storage device 120 is shown, the lookup tables may be stored in multiple storage devices 120.

[0021] Fig. 2 is a schematic drawing of an exemplary thermal model 200 of one type of engine 110. For example, the computing device 115 may be configured to calculate the thermal model 200 of Fig. 2 or a similar thermal model to estimate the temperature of a permanent magnet motor 110. As shown, the thermal model 200 includes eight nodes representing the temperature of various regions of the motor 110 under certain given operating conditions and boundary conditions of, for example, one or more components of the vehicle 100. However, more or fewer regions of the motor 110 and / or boundary conditions may be considered to estimate the temperature of the motor 110.

[0022] In one possible implementation, some of the nodes in the thermal model 200 may represent regions of the stator 125 and other nodes may represent regions of the rotor 130, and each node may have a temperature associated with it. That is, a first stator node 205 may represent the temperature at a non-flux-generating region of the stator 125 (e.g., stator iron). A second stator node 210 may represent the temperature at a flux-generating region of the stator 125 (e.g., stator iron). A third stator node 215 may represent the temperature of the copper used in the windings of the stator 125, such as the copper disposed in slots defined by the stator 125. A fourth stator node 220 may represent the end-turn temperature of the copper used in the windings of the stator 125. A first rotor node 225 may represent the temperature of the permanent magnets used by the rotor 130.A second rotor node 230 may represent the temperature at a non-flux generating region of the rotor 130 (e.g., a rotor iron).

[0023] The thermal model 200 may further include additional nodes representing various other regions of interest of the engine 110 independent of the stator 125 and the rotor 130. For example, some nodes may represent the temperature of the oil used in the engine 110. In an example implementation, a first oil node 235 may represent the temperature of the oil in one region of the engine 110, and a second oil node 240 may represent the temperature of the oil in another region of the engine 110.

[0024] Each of the nodes in the thermal model 200 may be connected to at least one other node by one or more heat transfer paths. The thermal model 200 may therefore include thermal resistances representing the heat transfer paths between the nodes. For example, a first thermal resistance 245 may represent external heat transfer by convection between the regions represented by the first oil node 235 and the first stator node 205. A second thermal resistance 250 may represent heat conduction between the regions represented by the first stator node 205 and the second stator node 210, via, for example, the stator lamination stack.A third thermal resistor 255 may represent heat conduction between the regions represented by the second stator node 210 and the third stator node 215, via, for example, the stator core, copper windings, and an insulation system. A fourth thermal resistor 260 may represent heat transfer through, for example, an air gap between the regions represented by the second stator node 210 and the first rotor node 225. A fifth thermal resistor 265 may represent heat conduction through copper windings between the regions represented by the third stator node 215 and the fourth stator node 220. A sixth thermal resistor 270 may represent convection between the regions represented by the fourth stator node 220 and the second oil node 240, e.g., from the oil to the winding ends of the stator 125.A seventh thermal resistor 275 may represent heat conduction through the rotor core between the regions represented by the first rotor node 225 and the second rotor node 230. An eighth thermal resistor 280 may represent the heat transfer path between the second rotor node 230 and the second oil node 240 caused by convection from the oil to the hub of the rotor 130. A ninth thermal resistor 285 may represent convection between the second oil node 240 and the first rotor node 225 (e.g., the rotor rings).

[0025] Fig. 3 illustrates a thermal model 300 of another type of motor 110, e.g., an induction motor 110. As shown, the first stator node 205, the second stator node 210, the third stator node 215, the fourth stator node 220, the second rotor node 230, the first oil node 235, and the second oil node 240 are substantially the same as described above with reference to Fig. 2. In the thermal model 300 of Fig. 3, however, the first rotor node 225 may represent the temperature of the bars of the rotor 130. Additionally, the thermal model 300 includes a third rotor node 305, which may represent the temperature of the end rings of the rotor 130.

[0026] The first to eighth thermal resistors 245-280 of the thermal model 300 may be substantially equal to the corresponding thermal resistors 245-280 described above with respect to the thermal model 200 of Fig. 2. The thermal model 300 of Fig. However, Figure 3 further includes a ninth thermal resistor 310, which may represent heat transfer between the regions represented by the first rotor node 225 and the third rotor node 305, which may be caused by heat conduction between the bars and end rings of the rotor 130. A tenth thermal resistor 315 may represent heat transfer by convection between the regions represented by the third rotor node 305 and the second oil node 240, between the oil and the rotor rings.

[0027] The computing device 115 can calculate the thermal model 200 from Fig. 2, the thermal model 300 from Fig. 3 or any other thermal model to estimate the temperature of the motor 110. For example, the thermal model may be presented to the computing device 115 as one or more first-order differential equations defining the energy balance at each node. The computing device 115 may solve the energy balance equation at each of the nodes based on the temperature of the node and the thermal resistances associated with each node. Additionally, the computing device 115 may consider the operating conditions of the motor 110 and the physical properties of the components that make up the motor 110, as discussed above.Furthermore, the computing device 115 may be configured to solve the energy balance equation at each node at multiple time steps and estimate the temperature of the engine 110 based at least in part on the change in temperature at each node over time. Furthermore, the computing device 115 may use the thermal model to consider regions with thermal losses as well as heat-generating regions when estimating the temperature of the engine 110.

[0028] Fig. 4 is a flowchart of an example process 400 that may be used to estimate the temperature of the engine 110 in real time. This process 400 for estimating the temperature of the engine 110 takes into account the operating conditions of the engine 110 as well as the physical properties of the components that make up the engine 110.

[0029] At block 405, the thermal model of the motor 110 may be generated. Generating the thermal model may include identifying one or more regions of, for example, the rotor 130 and the stator 125 that have physical significance during operation of the motor 110. Generating the motor 110 may further include identifying heat transfer paths between the identified regions of the motor 110. The identified regions of the motor 110 may each be associated with a node, and the identified heat transfer paths may each be associated with a thermal resistance. Additionally, an energy balance equation may be derived for each node, taking into account, for example, the operating conditions of the motor 110, the physical properties of the components used in the motor 110, regions of thermal loss of the motor 110, and so on.The thermal model, including the equations defining the temperature at each node, may be stored, for example, in the storage device 120.

[0030] At block 410, the computing device 115 may receive the thermal model of the engine 110. As discussed above, the thermal model may be expressed as one or more energy balance equations, such as one or more first-order differential equations. Consequently, the computing device 115 may access the energy balance equations from the storage device 120 that define the temperature at each node.

[0031] At block 415, the computing device 115 may solve the energy balance equation for each node. As discussed above, the energy balance equation may be used by the computing device 115 to determine the temperature at each node. In one possible implementation, the computing device 115 may solve each energy balance equation at two or more time steps to determine the temperature change at each node over time. The computing device 115 may access information from the storage device 120, stored, for example, in a lookup table, to solve the energy balance equation.

[0032] At block 420, the computing device 115 may estimate the temperature of the engine 110 in real time based at least in part on the temperature or temperature change at each node and the thermal resistances as defined by the thermal model, for example, via the energy balance equations. The computing device 115 may be calibrated to estimate the temperature of the engine 110 to be the highest, lowest, an average, etc., of the regions' temperatures. Alternatively, the computing device 115 may weight the temperature of one or more regions more heavily than other regions and thus estimate the temperature of the engine 110 according to the weight given to each region.

[0033] While the best modes for carrying out the invention have been described in detail, those skilled in the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.

Claims

[1] Vehicle that includes: a power source configured to supply electrical energy; a motor having a motor temperature and comprising a plurality of motor regions including a volume of oil used in the motor, a flux-generating region, a non-flux-generating region, and a region of stator windings, each of the plurality of motor regions having a respective regional temperature, and wherein the motor is configured to receive electrical energy from the power source and to generate rotational motion from the received electrical energy; and a computing device comprising a thermal model that estimates each of the regional temperatures, the computing device configured to estimate the engine temperature in real time based at least in part on the regional temperatures estimated by the engine thermal model; wherein the computing device is configured to estimate the engine temperature such that the engine temperature is the highest of the estimated regional temperatures or the lowest of the estimated regional temperatures or an average of the estimated regional temperatures, or wherein the computing device is configured to weight the estimated regional temperatures of one or more engine regions more heavily than the estimated regional temperatures of other engine regions and consequently estimate the engine temperature according to the weight given to each engine region; wherein the thermal model includes a plurality of nodes and at least one thermal resistor; wherein each node represents a region of the motor regions, and wherein each thermal resistor represents a heat transfer path between at least two of the nodes. [2] The vehicle of claim 1, wherein the computing device is configured to solve an energy balance equation for each node represented in the thermal model to estimate the temperature of the engine. [3] The vehicle of claim 2, wherein the computing device is configured to solve the energy balance equation for each node at a plurality of time steps. [4] The vehicle of claim 1, wherein the computing device is configured to estimate the temperature of the engine based at least in part on a change in temperature at each node. [5] The vehicle of claim 1, wherein the computing device is configured to estimate the temperature of the engine based at least in part on the temperature at each node at a plurality of time steps. [6] The vehicle of claim 1, wherein the computing device is configured to estimate the temperature of the engine based at least in part on at least one of the thermal resistances. [7] A vehicle according to claim 1, wherein at least one of the thermal resistances represents heat transfer in the engine by conduction and / or convection. [8] The vehicle of claim 1, wherein a thermal loss is associated with at least one of the nodes in the thermal model, and wherein the computing device is configured to estimate the temperature of the engine based at least in part on the thermal loss associated with at least one of the nodes. [9] The vehicle of claim 1, wherein at least one of the thermal resistances is based at least in part on a physical property of at least a portion of the engine.

Images