METHOD FOR MONITORING AN ELECTRIC MOTOR IN A VEHICLE AND A CORRESPONDINGLY TRAINED VEHICLE SYSTEM

Abstract

Vehicles and related systems and monitoring procedures are designed to detect insulation loss on one side of a power converter. A procedure includes monitoring a normalized voltage input to a power converter module coupled to the electric motor, determining, in response to the normalized voltage exceeding a diagnostic activation threshold, a first number of instances in which a range between successive extrema of the normalized voltage exceeds an insulation loss range threshold over a diagnostic time window, and automatically initiating a corrective action if the first number is greater than an insulation loss detection threshold.

Description

INTRODUCTION

[0001] The present invention relates generally to vehicle systems and, more particularly, to a method for monitoring an electric motor in a vehicle and to a correspondingly configured vehicle system.

[0002] For example, DE 10 2011 012 588 A1 describes a method for monitoring the electrical insulation of an electrical DC power circuit relative to a chassis ground. This method comprises monitoring a first electrical potential comprising a voltage difference between a positive electrical DC power bus and a negative electrical DC power bus; monitoring a second electrical potential comprising a voltage difference between the positive electrical DC power bus and the chassis ground; monitoring a third electrical potential comprising a voltage difference between the negative electrical DC power bus and the chassis ground; calculating a first voltage ratio comprising a ratiometric comparison of the third electrical potential with the second electrical potential.that electrical insulation between the positive electrical DC power bus and the chassis ground is monitored based on the first voltage ratio, and that electrical insulation between the negative electrical DC power bus and the chassis ground is monitored with respect to the first voltage ratio and the first electrical potential.

[0003] Advances in technology have led to significant changes in the design of motor vehicles. In particular, due to the electrification of the automotive propulsion system, electric motors (or electric machines) are finding an increasing number of applications in the automotive industry. Electric and / or hybrid vehicles use electric motors as either primary or supplemental torque sources in the automotive propulsion system. In electric and / or hybrid vehicles, the electric motor is typically powered by a rechargeable energy source such as a battery using one or more power conversion modules to generate the desired AC electrical signals across the electric motor's stator windings.

[0004] Electric motors are expected to operate with high reliability over extended periods of time under extreme operating conditions. However, over time, the operating stresses exerted on the electric motor can deteriorate the condition of the stator windings or otherwise render the electric motor inoperable. For example, mechanical shocks or stresses can cause rotor deformation or otherwise result in a conductive object striking or contacting the stator windings, causing intermittent insulation loss or a short circuit on the alternating current (AC) side. Accordingly, it is desirable to quickly detect and accurately diagnose insulation loss in the electric motor to extend the useful life of electrical components, reduce maintenance downtime, and maintain vehicle availability. SUMMARY

[0005] Devices for a vehicle and related methods and vehicle systems are provided. In one example implementation, a method for monitoring an electric motor in a vehicle includes monitoring, by a control module, a normalized voltage to a power conversion module coupled to the electric motor, determining, in response to the normalized voltage exceeding a diagnostic activation threshold, a first number of instances in which a range between consecutive extremes of the normalized voltage exceeds an insulation loss range threshold over a diagnostic time window after detecting that the normalized voltage exceeds the diagnostic activation threshold, and automatically initiating a remedial action if the first number is greater than an insulation loss detection threshold.

[0006] In one or more implementations, the method detects an alternating current (AC) insulation loss event after confirming that a respective average value associated with a respective instance of the consecutive extremes of the normalized voltage is within a threshold of a normalized voltage value, wherein automatically initiating the remedial action comprises automatically providing an indication of the AC insulation loss event. In one implementation, automatically providing the indication comprises the control module automatically generating a diagnostic code associated with the electric motor.

[0007] In one or more implementations, the method detects a direct current (DC) insulation loss event when a difference between a respective mean value associated with a respective instance of the consecutive extremes of the normalized voltage and a normalized voltage value is greater than a threshold, wherein automatically initiating the remedial action comprises automatically providing an indication of the DC insulation loss event.

[0008] In one or more implementations, monitoring the normalized voltage comprises obtaining a measured voltage for a reference node associated with a voltage bus coupled between a power source and the power conversion module with respect to a ground reference node and dividing the measured voltage by a direct current (DC) voltage associated with the power source to obtain the normalized voltage.

[0009] In one or more implementations, the method comprises extracting the instances of the consecutive extremes of the normalized voltage during the diagnostic time window, wherein a respective instance of the consecutive extremes includes a respective maximum of the normalized voltage and a respective minimum of the normalized voltage. In one implementation, the method subtracts the respective minimum of the normalized voltage from the respective maximum of the normalized voltage to obtain a respective range value associated with the respective instance of the consecutive extrema, wherein determining the first number of instances comprises incrementing a counter if the respective range value is greater than the insulation loss range threshold. In one implementation, automatically initiating the remedial action comprises automatically initiating the remedial action if a value of the counter is greater than the insulation loss detection threshold.

[0010] In one or more implementations, monitoring the normalized voltage comprises determining a mid-pack voltage between a node of a voltage bus coupled between a power source and the power conversion module and a vehicle body ground reference voltage node, dividing the mid-pack voltage by a direct current (DC) voltage associated with the power source to obtain a normalized mid-pack voltage, and monitoring the normalized mid-pack voltage. In one implementation, determining the first number of instances comprises counting the first number of instances in which the range between a respective pair of peak and valley values ​​for the normalized mid-pack voltage is greater than the insulation loss range threshold in the diagnostic time window.In one implementation, automatically initiating the remedial action includes automatically providing an indication of an alternating current (AC) insulation loss event when the first number of instances in which the range between respective pairs of peak and trough values ​​for the normalized pack center voltage is greater than the insulation loss range threshold in the diagnostic time window is greater than an AC insulation loss detection threshold number.

[0011] There is also provided an apparatus for a non-transitory computer-readable medium having executable instructions stored thereon that, when executed by a processor, cause the processor to provide a monitoring service configurable to monitor a normalized voltage to a power conversion module coupled to an electric motor of a vehicle in response to the normalized voltage exceeding a diagnostic activation threshold, determine a first number of instances in which a range between consecutive extremes of the normalized voltage exceeds an insulation loss range threshold over a diagnostic time window after detecting that the normalized voltage exceeds the diagnostic activation threshold, and automatically initiate a remedial action if the first number is greater than an insulation loss detection threshold.

[0012] In one or more implementations, the monitoring service is configurable to detect an alternating current (AC) insulation loss event after confirming that a respective mean value associated with a respective instance of the consecutive extremes of the normalized voltage is within a threshold of a normalized voltage value, wherein automatically initiating the remedial action comprises automatically providing an indication of the AC insulation loss event.

[0013] In one or more implementations, the monitoring service is configurable to detect a direct current (DC) insulation loss event when a respective average value associated with a respective instance of the consecutive extremes of the normalized voltage is greater than a normalized voltage value by more than a threshold, wherein automatically initiating the remedial action comprises automatically providing an indication of the DC insulation loss event.

[0014] In one or more implementations, the monitoring service is configurable to extract the instances of consecutive extremes of the normalized voltage during the diagnostic time window, wherein each instance of the consecutive extremes includes a respective maximum of the normalized voltage and a respective minimum of the normalized voltage. In one implementation, the monitoring service is configurable to subtract the respective minimum of the normalized voltage from the respective maximum of the normalized voltage to obtain a respective range value associated with the respective instance of the consecutive extremes, wherein determining the first number of instances comprises incrementing a counter if the respective range value is greater than the insulation loss range threshold.

[0015] A vehicle system is also provided that includes an electric motor, a direct current (DC) bus including a reference voltage node, a power conversion module coupled between the DC bus and the electric motor, and a control module coupled to the power conversion module to provide a monitoring service.The monitoring service is configurable to monitor a normalized voltage to the power conversion module, including a relationship between a measured voltage of the reference voltage node and a DC voltage associated with the DC bus, determining, in response to the normalized voltage exceeding a diagnostic activation threshold, a first number of instances in which a range between consecutive extremes of the normalized voltage exceeds an insulation loss range threshold over a diagnostic time window after detecting that the normalized voltage exceeds the diagnostic activation threshold, and automatically initiating a remedial action if the first number is greater than an insulation loss detection threshold.

[0016] In one or more implementations, the vehicle system includes an output device coupled to the control module, wherein the remedial action comprises the monitoring service providing a user notification via the output device. In one or more implementations, the output device is a dashboard indicator, and the user notification is implemented as illumination or activation of the dashboard indicator.

[0017] In one or more implementations, the vehicle system includes a power source coupled to the DC bus, where the DC voltage is an output voltage associated with the power source. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The exemplary aspects are described below in connection with the following drawing figures, where similar numerals indicate similar elements; they show: Fig. 1 is a block diagram illustrating an electrical system suitable for use with a vehicle and configurable to support a monitoring service that detects a loss of insulation on an alternating current (AC) side of the electrical system, according to various implementations; Fig. 2 a flowchart illustrating an exemplary loss of insulation (LOI) detection process that is intended to be implemented by a monitoring service in the vehicle electrical system of Fig. 1 is suitable, according to one or more implementations described herein; and Fig. 3 a graph showing normalized pack center voltages in the electrical system of Fig. 1 in conjunction with an exemplary implementation of the LOI detection process of Fig. 2 represents. DETAILED DESCRIPTION

[0019] The following detailed description is merely exemplary in nature. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding introduction, the preceding summary, or the following detailed description. As used herein, the term module refers to any hardware, software, firmware, electronic control component, processing logic, and / or processor device, individually or in any combination, including, without limitation, an application-specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) with memory executing one or more software or firmware programs, a combinational logic circuit, and / or other suitable components that provide the described functionality.

[0020] Fig. 1 illustrates an exemplary implementation of an electrical system 100 suitable for use in a motor vehicle 150. The illustrated electrical system 100 includes, without limitation, a power source 102, a power conversion module 104, an electric motor 106, a control module 108, and at least one output device 110. In the illustrated implementation, the control module 108 is coupled to the power conversion module 104 and generates instructions for operating the power conversion module 104 in a manner that results in the desired operation of the electric motor 106 in response to instructions received from the driver of the vehicle 150 (e.g., via an accelerator pedal, a brake pedal, a cruise control system, a collision avoidance system, etc.).In example implementations, voltage sensors are coupled to respective nodes 112, 114 corresponding to the respective power supply rails of a direct current (DC) voltage bus used to deliver electrical power from the energy source 102 to the power conversion module 104 to obtain voltage measurements associated with the respective voltage nodes 112, 114 and indicative of the voltage input to the power conversion module 104.As described in more detail below, in example implementations, a loss of insulation (LOI) monitoring service at the control module 108 monitors the respective voltages of the nodes 112, 114 with respect to the body or other ground voltage to detect and diagnose an AC loss of insulation (ACLOI) at the electric motor 106 or otherwise between the power conversion module 104 and the electric motor 106 on the AC side of the electrical system 100.

[0021] The energy source 102 (or power source) generally represents the component in the vehicle 150 that can provide a direct current (DC) voltage to the power conversion module 104 to operate the electric motor 106. Depending on the implementation, the energy source 102 can be implemented as a battery, a fuel cell, a high-voltage rechargeable battery pack, an ultracapacitor, or any other suitable energy source known in the art. In still other implementations, the energy source 102 can be implemented as the output of a DC-DC converter, a rectifier, a voltage regulator, or other electrical circuits, modules, or components that accept input power from another source.With this in mind, in exemplary implementations, the energy source 102 is implemented as one or more rechargeable batteries configured to provide the desired DC voltage for operating the electric motor 106.

[0022] The power conversion module 104 generally represents the component in the vehicle 150 that is coupled between the power source 102 and the electric motor 106 to convert the direct current (DC) power from the power source 102 into alternating current (AC) power to drive the electric motor 106. In this regard, in example implementations, the power conversion module 104 is implemented as a power inverter having one or more phase legs, each phase leg corresponding to a respective phase of the electric motor 106. Generally, switches of a phase leg are modulated (opened or closed) at a particular switching frequency and duty cycle to generate an AC voltage across their associated phase from stator windings of the electric motor 106, which in turn generates a torque-producing current in those stator windings and operates the electric motor 106.For purposes of illustration, but not limitation, the power conversion module 104 may alternatively be referred to as an inverter module or a power inverter, however, the subject matter described herein is not necessarily limited to DC / AC power converters.

[0023] In an exemplary implementation, the electric motor 106 is realized as an induction motor, however, the subject matter described herein should not be construed as limited to use with any particular type of electric motor. In further implementations, the electric motor 106 may be realized as an internal permanent magnet (IPM) motor, a synchronous reluctance motor, or any other suitable motor known in the art. Although Fig. 1, the engine 106 may include a transmission integrated therewith such that the engine 106 and the transmission are mechanically coupled to at least some of the wheels of the vehicle 150 through one or more drive shafts such that the speed of the engine 106 (e.g., the rotational speed of the rotor) affects the speed of the vehicle 150.

[0024] In example implementations, the vehicle 150 is implemented as an automobile, and depending on the implementation, the vehicle 150 may be one of several different types of automobiles, such as a sedan, a station wagon, a truck, or an off-road vehicle (SUV), and may have two-wheel drive (2WD) (i.e., rear-wheel drive or front-wheel drive), four-wheel drive (4WD), or all-wheel drive (AWD). In example implementations, the vehicle 150 is implemented as an all-electric vehicle, a plug-in hybrid vehicle, or the like. However, in various implementations, the vehicle 150 may be implemented as a fuel cell vehicle (FCV) or other suitable alternative fuel vehicle, and / or the vehicle 150 may also have one or a combination of several different types of power engines, such as, for example, a diesel engine.a petrol or diesel internal combustion engine, a ‘flexible fuel vehicle’ (FFV) engine (i.e. using a blend of petrol and alcohol), an engine powered by a gaseous compound (e.g. hydrogen, natural gas, propane, etc.) and / or an internal combustion engine / electric motor hybrid engine.

[0025] In example implementations, the output device 110 generally represents a component associated with the vehicle 150 that can provide one or more user messages or alerts to a driver or another user associated with the vehicle 150. For example, in certain implementations, the output device 110 may include or be otherwise implemented as one or more lights, indicators, or other elements on an instrument panel of the vehicle 150. In further implementations, the output device 110 may be implemented as an electronic display device disposed onboard the vehicle 150 or another system onboard the vehicle 150, such asany type of infotainment module, navigation head unit, or other similar or suitable unit located on board the vehicle 150, which may be integrated into an instrument panel or another console in a passenger compartment of the vehicle 150. With this in mind, in still further implementations, the output device 110 may be realized as an electronic device associated with a vehicle owner or another user associated with the vehicle 150, which is separate and distinct from the vehicle 150, but communicatively coupled to the control module 108 via a communications network, such as a smartphone, a mobile computer (e.g., a tablet computer, a laptop computer, or a netbook computer), a wearable computing device (e.g., a smartwatch, smart glasses, smart clothing), or the like.

[0026] With reference again to Fig. 1, the control module 108 generally represents the hardware, firmware, software, and / or other components of the electrical system 100 that are configured to operate the power conversion module 104 to supply electrical power to the electric motor 106 while monitoring the voltages of the respective DC bus nodes 112, 114 in a time-overlapping manner to detect a loss of insulation on the AC side of the electrical system 100 (e.g., at the electric motor 106 or between the power conversion module 104 and the electric motor 106).Depending on the implementation, the control module 108 may include or be implemented as a custom-manufactured or off-the-shelf processor, a central processing unit (CPU), a graphics processing unit (GPU), an auxiliary processor among multiple processors associated with the control module 108, a semiconductor-based microprocessor (in the form of a microchip or chipset), any combination thereof, or generally a means for executing instructions. In practice, the control module 108 may include processing logic configurable to perform the functions, techniques, and processing tasks associated with the operation of the vehicle electrical system 100, as described in more detail below.

[0027] In example implementations, the steps of a method or algorithm described in connection with the implementations disclosed herein may be embodied directly in hardware, in firmware, in a software module executed by the control module 108, or in any convenient combination thereof. In example implementations, the control module 108 includes or otherwise accesses a data storage element, random access memory or other short- or long-term storage media, or other suitable non-transitory computer-readable devices or media capable of storing or otherwise accessing programming instructions for execution by the control module 108, which may include volatile and non-volatile memory in read-only memory (ROM), random access memory (RAM), retained memory (RAM), flash memory, registers, hard disks, removable disks, magnetic or optical mass storage, and / or the like.The computer-executable programming instructions, when read and executed by the control module 108, cause the control module 108 to execute, support, generate, or otherwise provide a monitoring service that monitors the voltages at the DC bus nodes 112, 114 to detect AC insulation loss and to perform various tasks, operations, functions, and processes described herein.

[0028] Fig. 2 illustrates an exemplary loss of insulation (LOI) detection process 200 suitable for implementation by monitoring a service associated with a control module control operation of an electric motor using a power conversion assembly. For illustrative purposes, the following description may refer to elements associated with Fig. 1 above. While portions of the LOI detection process 200 may be performed by various elements of a vehicle system, for purposes of explanation, the subject matter herein may be described substantially in the context of an LOI detection process 200 performed substantially by a monitoring service at the control module 108.

[0029] The LOI detection process 200 initializes or otherwise begins at 202 by calculating or otherwise determining normalized center-of-pack voltages (measured with respect to the vehicle body ground reference voltage) for the positive and negative rails of the DC bus supplying power to the power conversion assembly, and monitoring the normalized center-of-pack voltages to detect at 204 when at least one of the normalized center-of-pack voltages meets a diagnostic activation threshold for insulation loss detection. In this regard, the LOI monitoring service at the control module 108 continuously monitors the normalized center-of-pack voltages for a deviation from a normal operating range, potentially indicating insulation loss on the AC side of the electrical system 100.In example implementations, the LOI monitoring service calculates or otherwise determines a normalized positive center-of-pack voltage by obtaining, from a voltage sensor associated with the positive DC bus reference node 112, a positive reference voltage reading indicative of the voltage of the positive DC bus reference node 112 relative to the body or ground reference voltage, and then dividing the magnitude of the positive reference voltage reading by the voltage difference between the positive and negative DC bus reference nodes 112, 114 (e.g., the DC reference voltage output by the power source 102). Thus, the normalized positive center-of-pack voltage may correspond to the relative percentage or distribution of the battery pack voltage that is above (or positive with respect to) the body or ground voltage.Similarly, the normalized negative center-of-pack voltage is calculated by obtaining, from a voltage sensor associated with the negative DC bus reference node 114, a negative reference voltage reading indicative of the voltage of the negative DC bus reference node 114 relative to the body or ground reference voltage, and then dividing the magnitude of the negative reference voltage reading by the cumulative voltage difference between the positive and negative DC bus reference nodes 112, 114. Accordingly, the normalized negative center-of-pack voltage may correspond to the relative percentage or distribution of the battery pack voltage that is below (or negative relative to) the body or ground voltage.

[0030] After determining the normalized positive and negative center-of-pack voltages, the LOI detection process 200 compares the normalized center-of-pack voltage values ​​to one or more activation thresholds or other criteria used to initiate diagnostic monitoring to confirm whether the excursion or deviation of the normalized center-of-pack voltages is attributable to an ACLOI condition. For example, in one implementation, the LOI detection process 200 monitors the normalized center-of-pack voltages to detect when one of the normalized center-of-pack voltages falls below a lower threshold of 0.2 (or 20% of the battery pack voltage) or exceeds an upper threshold of 0.8 (or 80% of the battery pack voltage).In this regard, the one or more diagnostic activation thresholds may be selected to accommodate transient fluctuations in voltage due to active isolation or other processes or operations that may cause fluctuations in the relative voltage between the DC bus nodes 112, 114 and the ground or body reference voltage node.

[0031] In response to detecting a normalized center-of-pack voltage that meets a diagnostic activation threshold, the LOI detection process 200 monitors the respective normalized center-of-pack voltages over a diagnostic time window to identify and extract consecutive pairs of voltage extrema (cycle maxima or peaks and cycle minima or valleys) in the diagnostic window at 206. To identify and extract peaks and valleys, the LOI monitoring service at the control module 108 analyzes consecutive samples of the respective voltage nodes 112, 114 to determine whether the difference between samples is greater than a threshold voltage difference (e.g.,to attenuate noise), and adds the normalized voltage value to a temporary matrix or buffer if the difference from the previous sample in the matrix is ​​greater than the threshold voltage difference, and discards the normalized voltage sample if the difference is less than the threshold voltage difference. When the normalized voltage samples in the temporary matrix or buffer indicate an extremum or change in the electrical cycle, the LOI monitoring service stores or otherwise retains this minimum or maximum value as a respective peak or valley extremum in the diagnostic window.For example, in one implementation, the temporary matrix may be configured to retain the three most recent normalized voltage samples that exceed the threshold voltage difference with respect to the previous sample. If the buffered normalized voltage values ​​indicate an extremum and a corresponding change in the direction of the electrical cycle, the second or middle normalized voltage sample corresponding to that extremum is then stored or retained as a respective peak or valley value in the diagnostic window. In this manner, the LOI monitoring service at the control module 108 extracts a first set of normalized peak and valley voltage extrema for the positive DC bus reference node 112 and a second set of normalized peak and valley voltage extrema for the negative DC bus reference node 114.

[0032] With reference again to Fig. 2, after extracting the normalized voltage extrema for the respective pack center voltages for the positive and negative rails of the DC bus, the LOI detection process 200 calculates or otherwise determines a mean and range values ​​for respective peak and valley pairs of extrema in the diagnostic window at 208 and detects an occurrence of an ACLOI condition based on the respective mean and range values ​​at 210. In this regard, in example implementations, the LOI detection process 200 performs a rainfall flow range mean analysis to determine when to due the diagnosis of an ACLOI event based on the number of respective range values ​​that exceed an LOI range detection threshold and that are greater than a diagnostic threshold.If the number of range values ​​exceeding the LOI range detection threshold in the diagnostic window is less than the diagnostic threshold, the LOI detection process 200 determines that no LOI condition exists and returns to monitoring the normalized pack center voltages to reinitiate a subsequent diagnostic window at 202 and 204. In this way, the LOI detection process 200 avoids false positives or false triggering of LOI notifications due to noise or other transients.

[0033] In one or more implementations, for each consecutive pair of normalized peak and valley voltage extrema for the positive DC bus reference node 112, the LOI monitoring service at the control module 108 may calculate a respective range value associated with that respective peak and valley pair by subtracting the extracted normalized valley voltage value from the extracted normalized peak voltage value and calculating a corresponding average value associated with that respective peak and valley pair by averaging the respective extracted normalized valley voltage value and the respective extracted normalized peak voltage value.In example implementations, the LOI detection process 200 identifies an ACLOI condition by counting the number of respective peak-valley pairs that have an associated range value greater than an ACLOI range threshold, and detecting the ACLOI condition when the number of respective peak-valley pairs that exceed the ACLOI range threshold within the diagnostic window is greater than an ACLOI detection threshold. For example, in one implementation, the LOI monitoring service at the control module 108 detects an ACLOI condition when two or more peak-valley pairs associated with a respective DC bus reference node 112, 114 have an associated range value greater than 0.8 (or 80% of the battery pack voltage).

[0034] In certain implementations, the average value associated with the respective peak-valley pairs is used to confirm or otherwise verify that the range values ​​associated with the respective peak-valley pairs indicate an LOI condition. For example, if the average value associated with the respective peak-valley pairs is within an LOI confirmation threshold of the normalized mid-pack voltage value of 0.5 (or 50% of the battery pack voltage), no DCLOI is detected because the normalized positive and negative mid-pack voltages are symmetrical around the value of 0.5 during normal conditions. However, the range value associated with the respective peak-valley pair may be considered indicative of an ACLOI condition, even if the average value is consistent with a normal condition on the DC side of the electrical system 100 (e.g.,The LOI detection process 200 may classify or otherwise characterize the respective peak-to-valley pair as indicating a DC insulation loss (DCLOI) condition and may fail to increment an ACLOI counter. In this regard, in certain implementations, if the number of respective peak-to-valley pairs having a range value that exceeds an ACLOI range threshold, the LOI monitoring service at the control module 108 may detect an AC LOI condition.In this way, the respective range values ​​associated with respective peak-valley pairs can be used to detect an ACLOI condition, and the mean value associated with the respective peak-valley pairs can be used to classify the LOI condition as a DCLOI event.

[0035] With reference again to Fig. 2, in example implementations, upon detecting an LOI condition, the LOI detection process 200 automatically initiates one or more remedial actions at 212. In one or more implementations, in response to detecting an ACLOI event at the control module 108, the LOI monitoring service automatically generates or otherwise provides an indication of an LOI event, e.g., by setting an ACLOI diagnostic flag bit to a value indicative of an ACLOI event, or otherwise automatically initiating generation of a service code or diagnostic code associated with the electric motor 106 to provide a user, via the output device 110, with appropriate notification to examine the electric motor 106 or the AC side of the electrical system 100 during the next service event.Additionally or alternatively, the LOI monitoring service at the control module 108 may automatically initiate generation of a user notification via the output device 110 alerting the driver or another operator of the vehicle 150 of a potential maintenance issue (e.g., by illuminating an engine check light or one or more instrument panel indicators) to expedite maintenance related to the vehicle 150. In certain implementations, the LOI monitoring service may also cause the control module 108 to implement an alternative control mode when the power conversion module 104 and / or the electric motor 106 are operating to potentially mitigate adverse effects of an ACLOI condition (e.g., a safe mode, a limp home mode, and / or the like).In this regard, it should be appreciated that numerous different possible combinations of remedial actions and corresponding schemes, thresholds, and / or logic rules for generating such remedial actions exist, and the subject matter described herein is not intended to be limited to any particular implementation. Additionally, it should be appreciated that the LOI monitoring service at control module 108 may automatically generate or otherwise provide an indication of an LOI event in response to a DCLOI event being detected in a similar manner (e.g., by setting a DCLOI diagnostic flag, generating a DCLOI diagnostic code, etc.).

[0036] Fig.3 is a graph 300 illustrating a relationship between the normalized positive pack center voltage 302 associated with the positive DC bus reference node 112 and the normalized negative pack center voltage 304 associated with the negative DC bus reference node 114 with respect to time for an exemplary implementation of the LOI detection process 200. At a time 310, when the normalized positive pack center voltage 302 falls below the lower diagnostic activation threshold 308 (e.g., 0.2) and the normalized negative pack center voltage 304 exceeds the upper diagnostic activation threshold 306 (e.g., 0.8), the LOI monitoring service at the control module 108 initiates the diagnostic monitoring window (e.g., at 204).Next, the LOI monitoring service at the control module 108 identifies and extracts a valley 312 corresponding to a lower extremum of the normalized positive center-of-pack voltage 302, followed by a peak 314 corresponding to the following upper extremum of the normalized positive center-of-pack voltage 302, and a peak 316 corresponding to the upper extremum of the normalized negative center-of-pack voltage 304, followed by a valley 318 corresponding to the following lower extremum of the normalized negative center-of-pack voltage 304 (e.g., at 206 of the LOI detection process 200). Note that during normal operating conditions, the normalized positive center-of-pack voltage 302 and the normalized negative center-of-pack voltage 304 would be expected to be symmetrical with respect to the midpoint or median value of 0.5 in the absence of an LOI condition.

[0037] The monitoring service at the control module 108 determines that the difference between the peak-and-valley value pair 312, 314 associated with the normalized positive center-of-pack voltage 302 (e.g., 0.93) is greater than an ACLOI range threshold (e.g., 0.8) and increments an ACLOI detection counter (e.g., at 208 of the LOI detection process 200). Accordingly, if the difference between the peak-and-valley value pair 316, 318 associated with the normalized negative center-of-pack voltage 304 (e.g., 0.93) is greater than an ACLOI range threshold (e.g., 0.8), the LOI monitoring service at the control module 108 increments the ACLOI detection counter. If the value of the ACLOI detection counter, which tracks the number of ACLOI range excursion events in the diagnostic window, is greater than or equal to the ACLOI detection threshold (e.g., 2), the LOI monitoring service at the control module 108 detects an occurrence of an ACLOI event at time 310 (e.g.,at 210 of the LOI detection process 200). In this regard, accordingly, if the LOI monitoring service verifies that both the average of the positive reference DC peak-and-valley pair 312, 314 and the average of the negative reference DC peak-and-valley pair 316, 318 are within a normalized pack center voltage threshold of 0.5, the LOI monitoring service at the control module 108 classifies the LOI event as a DCLOI event and accordingly initiates one or more remedial actions in response to the DCLOI event (e.g., at 212 of the LOI detection process 200).

[0038] It can be seen that the LOI detection process 200 can quickly and accurately diagnose a short circuit or other insulation loss on the AC side of the electrical system (e.g., at the electric motor 106 or between the power conversion module 104 and the electric motor 106) by monitoring voltage measurements on the DC side of the electrical system 100. By comparing positive-to-body and negative-to-body center-of-pack voltages to calibratable voltage thresholds and analyzing the ranges and averages calculated from extremes of the center-of-pack voltages during a diagnostic window, the LOI detection process 200 can distinguish a true ACLOI event from active insulation or insulation loss on the DC side.By reliably diagnosing an ACLOI event, the costs associated with a misdiagnosis or an inability to diagnose the problem are reduced. For example, a lack of an accurate diagnosis of an ACLOI event can result in false triggering of DC-side diagnostic events and undesirable maintenance costs and downtime, such as replacement or further maintenance performed on the power source 102, the power conversion module 104, or other DC-side components (e.g., contactors or other components) when the ACLOI condition or another fault condition actually exists in the electric motor 106 or otherwise on the AC side.Additionally, a driver or other vehicle operator may be notified of the ACLOI event at an earlier stage to enable remedial actions by the driver or other vehicle operator prior to progression of the ACLOI condition to prolong operation of the vehicle 150.

[0039] For the sake of brevity, conventional techniques related to electric vehicle systems, electric motors, power converters, and other functional aspects of the systems (and the individual operating components of the systems) need not be described in detail here. Furthermore, the interconnections shown in the various figures included herein are intended to illustrate exemplary functional relationships and / or physical couplings between the various elements. It should be appreciated that many alternative or additional functional relationships or physical connections may exist in an implementation of the subject matter.

[0040] As used herein, the word "exemplary" means "serving as an example, instance, or illustration." Thus, an implementation described herein as "exemplary" should not necessarily be construed as preferred or advantageous over other implementations. All of the implementations described herein are exemplary implementations provided to enable those skilled in the art to make or use the invention.

[0041] Those skilled in the art will appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the implementations disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. Some of the implementations are described above in terms of functional and / or logical block components (or modules) and various processing steps. However, it should be recognized that such block components (or modules) may be implemented by any number of hardware, software, and / or firmware components configured to perform the specified functions. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality.Whether such functionality is implemented in hardware or software depends on the specific application and the design constraints defined for the overall system. Skilled professionals can implement the described functionality in various ways for each specific application.

[0042] When implemented in software or firmware, various elements of the systems described herein are essentially the code segments or instructions that perform various tasks. The program or code segments may be stored in a processor-readable medium or transmitted by a computer data signal embodied in a carrier wave over a transmission medium or communication path. The "computer-readable medium," "processor-readable medium," or "machine-readable medium" may include any medium capable of storing or transmitting information. Examples of the processor-readable medium include an electronic circuit, a semiconductor memory device, a read-only memory (ROM), a flash memory, an erasable read-only memory (EROM), a floppy disk, a CD-ROM, an optical disk, a hard disk, a fiber optic medium, a radio frequency (RF) link, or the like.The computer data signal may include any signal capable of propagating over a transmission medium such as electronic network channels, optical fibers, air, electromagnetic paths, or RF links. The code segments may be downloaded over computer networks such as the Internet, an intranet, a LAN, or the like.

[0043] In this document, relational expressions such as first and second and the like may be used solely to distinguish one unit or action from another unit or action, without necessarily requiring or implying any actual such relationship or sequence between such units or actions. Numerical ordinals such as "first," "second," "third," etc., simply denote various ones of a plurality and do not imply any order or sequence unless specifically defined by the claim language. The sequence of text in any of the claims does not imply that process steps must be performed in a temporal or logical order according to such sequence unless specifically defined by the claim language. The process steps may be interchanged in any order.

[0044] Furthermore, the foregoing description may refer to elements, nodes, or features that are "coupled" to one another. As used herein, unless expressly stated otherwise, "coupled" means that an element / node / feature is not necessarily mechanically connected (or directly or indirectly communicates) with another element / node / feature. For example, two elements may be physically, electronically, logically, or otherwise coupled to one another by one or more additional elements. Thus, although the drawings depict a particular exemplary arrangement of elements directly connected to one another, additional intervening elements, devices, features, or components may be present in an implementation of the depicted subject matter.In addition, certain terminology may be used herein for reference purposes only and is not intended to be limiting. legend

[0045] In the drawings, N stands for No and Y stands for Yes.

Claims

[1] A method for monitoring an electric motor (106) in a vehicle (150), the method comprising: Monitoring by a control module (108) a normalized voltage to a power conversion module (104) coupled to the electric motor (106); Determining, in response to the normalized voltage exceeding a diagnostic activation threshold, a first number of instances in which a range between consecutive extremes of the normalized voltage exceeds an insulation loss range threshold over a diagnostic time window after detecting that the normalized voltage exceeds the diagnostic activation threshold; and automatically initiate a remedial action if the first count is greater than an insulation loss detection threshold. [2] The method of claim 1, further comprising detecting an alternating current (AC) insulation loss event after confirming that a respective average value associated with a respective instance of the successive extremes of the normalized voltage is within a threshold of a normalized voltage value, wherein automatically initiating the remedial action comprises automatically providing an indication of the AC insulation loss event. [3] The method of claim 2, wherein automatically providing the indication comprises the control module (108) automatically generating a diagnostic code associated with the electric motor (106). [4] The method of claim 1, further comprising detecting a direct current (DC) insulation loss event when a difference between a respective mean value associated with a respective instance of the successive extremes of the normalized voltage and a normalized voltage value is greater than a threshold, wherein automatically initiating the remedial action comprises automatically providing an indication of the DC insulation loss event. [5] The method of claim 1, wherein monitoring the normalized voltage comprises: Obtaining a measured voltage for a reference node (112, 114) associated with a voltage bus coupled between a power source (102) and the power conversion module (104) with respect to a ground reference node; and Dividing the measured voltage by a direct current (DC) voltage associated with the energy source (102) to obtain the normalized voltage. [6] The method of claim 1, further comprising extracting the instances of the successive extrema of the normalized voltage during the diagnostic time window, wherein a respective instance of the successive extrema comprises a respective maximum of the normalized voltage and a respective minimum of the normalized voltage. [7] The method of claim 6, further comprising subtracting the respective minimum of the normalized voltage from the respective maximum of the normalized voltage to obtain a respective range value associated with the respective instance of the successive extrema, wherein determining the first number of instances comprises incrementing a counter if the respective range value is greater than the insulation loss range threshold. [8] The method of claim 7, wherein automatically initiating the remedial action comprises automatically initiating the remedial action when a value of the counter is greater than the insulation loss detection threshold. [9] The method of claim 1, wherein monitoring the normalized voltage comprises: Determining a pack center voltage between a node of a voltage bus coupled between a power source (102) and the power conversion module (104); Dividing the pack center voltage by a direct current (DC) voltage associated with the energy source (102) to obtain a normalized pack center voltage; and Monitoring the standardized pack center voltage. [10] Vehicle system that contains: an electric motor (106); a direct current (DC) bus comprising a reference voltage node; a power conversion module (104) coupled between the DC bus and the electric motor (106); and a control module (108) coupled to the power conversion module (104) to provide a monitoring service configurable to: Monitoring a normalized voltage to the power conversion module (104) comprising a relationship between a measured voltage of the reference voltage node and a DC voltage associated with the DC bus; Determining, in response to the normalized voltage exceeding a diagnostic activation threshold, a first number of instances in which a range between consecutive extremes of the normalized voltage exceeds an insulation loss range threshold over a diagnostic time window after detecting that the normalized voltage exceeds the diagnostic activation threshold; and automatically initiate a remedial action if the first count is greater than an insulation loss detection threshold.

Images