Adaptive Rotary Transformer Envelope Diagnosis

Abstract

A diagnostic system and method for a rotary transformer used in an electric motor are disclosed. The diagnostic system includes an x-phase winding, a y-phase winding, and a processor. The x-phase winding generates an x-phase voltage, and the y-phase winding generates a y-phase voltage. The processor obtains the x-phase and y-phase voltages, determines an adaptive cosine envelope from the x-phase voltage and an adaptive sine envelope from the y-phase voltage, determines an adaptive amplitude from the adaptive sine and adaptive cosine envelopes, determines an amplitude average based on the adaptive amplitude, determines a fault in the rotary transformer when the ratio of the adaptive amplitude to the amplitude average is greater than a threshold, and transmits a fault signal.

Description

Technical Field

[0001] This subject matter relates to electric motors, and more particularly to systems and methods for diagnosing faults in rotary transformers used for direct field-oriented control of electric motors. Background Technology

[0002] Electric motors are used to generate rotational motion and are used in the propulsion systems of electric or hybrid vehicles. An electric motor consists of a stator and a rotor, with the rotor rotating within the stator due to a magnetic field generated by electricity flowing through windings in the stator and / or rotor. The operation of an electric motor can be affected by various parameters, such as the angular alignment between the stator and rotor, and the angular position of the windings on one or both of the stator and rotor. A resolver can be used to monitor these parameters of the electric motor in order to properly control the motor's magnetic field. However, resolvers can deteriorate or fail over time, leading to faulty resolver operation, which results in incorrect control of the motor's magnetic field. Therefore, it is desirable to be able to diagnose the operation of the resolver so that it can be properly monitored and replaced when necessary. Summary of the Invention

[0003] In one exemplary embodiment, a method for diagnosing a rotary transformer for an electric motor is disclosed. Adaptive sine envelopes and adaptive cosine envelopes are obtained from measurements taken from the rotary transformer. Adaptive amplitude is determined from the adaptive sine envelopes and adaptive cosine envelopes. Amplitude averaging is determined based on the adaptive amplitude. Faults in the rotary transformer are determined based on the adaptive amplitude and amplitude averaging.

[0004] In addition to one or more features described herein, the amplitude averaging is a rolling average. Adaptive amplitudes at multiple time intervals are determined, and a rolling average is determined from the adaptive amplitudes at multiple time intervals. The method also includes replacing the resolver when a fault is identified. The method further includes identifying a fault when the absolute value of the difference between 1 and the ratio of the adaptive amplitude to the amplitude average is greater than a threshold. The method also includes obtaining the x-phase and y-phase voltages from the resolver and performing oscillation compensation on the x-phase and y-phase voltages to obtain adaptive cosine envelopes and adaptive sine envelopes, respectively. The method also includes identifying a fault in the resolver on the motor while the motor is operatively coupled to the vehicle.

[0005] In another exemplary embodiment, a diagnostic system for a resolver of an electric motor is disclosed. The diagnostic system includes an x-phase winding, a y-phase winding, and a processor. The processor is configured to obtain an x-phase voltage from the x-phase winding and a y-phase voltage from the y-phase winding; determine an adaptive cosine envelope from the x-phase voltage and an adaptive sine envelope from the y-phase voltage; determine an adaptive amplitude from the adaptive sine and adaptive cosine envelopes; determine an amplitude average based on the adaptive amplitude; determine a fault in the resolver based on the adaptive amplitude and the amplitude average; and transmit a fault signal.

[0006] In addition to one or more features described herein, the amplitude averaging is a rolling average. The processor is also configured to determine adaptive amplitudes at multiple time intervals and to determine a rolling average from the adaptive amplitudes at multiple time intervals. A signal indicates a defect in the resolver. The processor is also configured to determine a fault when the absolute value of the difference between 1 and the ratio of the adaptive amplitude to the amplitude average is greater than a threshold. The processor is also configured to perform swing compensation on the x-phase voltage and y-phase voltage to obtain adaptive cosine envelopes and adaptive sine envelopes, respectively. The processor is also configured to determine a resolver fault when the motor is operatively coupled to the vehicle.

[0007] In yet another exemplary embodiment, a diagnostic system for use with a resolver of an electric motor is disclosed. The diagnostic system includes a processor configured to obtain an x-phase voltage from an x-phase winding of the resolver and a y-phase voltage from a y-phase winding of the resolver, determine an adaptive cosine envelope from the x-phase voltage and an adaptive sine envelope from the y-phase voltage, determine an adaptive amplitude from the adaptive sine and adaptive cosine envelopes, determine an amplitude average based on the adaptive amplitude, and determine a fault transmission signal.

[0008] In addition to one or more features described herein, the amplitude averaging is a rolling average. The processor is also configured to determine adaptive amplitudes at multiple time intervals and to determine a rolling average from the adaptive amplitudes at multiple time intervals. In an embodiment, a signal indicates a defect in the resolver. The processor is also configured to determine a fault when the absolute value of the difference between 1 and the ratio of the adaptive amplitude to the amplitude average is greater than a threshold. The processor is also configured to perform oscillation compensation on the x-phase voltage and y-phase voltage to obtain adaptive cosine envelopes and adaptive sine envelopes, respectively.

[0009] The above-described features and advantages, as well as other features and advantages of this disclosure, will become apparent when taken in conjunction with the accompanying drawings and the following detailed description. Attached Figure Description

[0010] Other features, advantages, and details appear by way of example only in the following detailed specification, which refers to the accompanying drawings, wherein:

[0011] Figure 1 An electric motor is shown in an illustrative embodiment;

[0012] Figure 2 A schematic diagram of the diagnostic system is shown;

[0013] Figure 3 A graph showing the raw winding voltage received at the processor of the diagnostic system is displayed.

[0014] Figure 4 A graph of the adaptive voltage envelope is shown;

[0015] Figure 5 An illustrative plot of adaptive amplitude based on adaptive voltage envelope is shown; and

[0016] Figure 6 A flowchart is shown for a method of diagnosing defective rotary transformers. Detailed Implementation

[0017] The following description is exemplary in nature only and is not intended to limit this disclosure, its application, or use. It should be understood that throughout the drawings, corresponding reference numerals denote the same or corresponding parts and features.

[0018] According to an exemplary embodiment, Figure 1 An electric motor 100 is shown in an illustrative embodiment. In various embodiments, the electric motor 100 may be adapted for use in a vehicle. In various embodiments, the electric motor 100 may be coupled to a vehicle for operating the vehicle during testing and diagnostics. The electric motor 100 includes a stator 102 and a rotor 104 that rotates with the stator 102. The stator 102 includes windings 106, and the rotor 104 includes a magnet 108. Current circulates through the windings 106 to generate a magnetic field that interacts with the magnetic field of the magnet 108, thereby rotating the rotor 104. The rotor 104 is coupled to a shaft 110 for transmitting rotation to a device in the vehicle for vehicle operation. The shaft 110 passes through a resolver 112, which measures the rotation of the shaft 110.

[0019] Figure 2 A schematic diagram of a diagnostic system 200 is shown. The diagnostic system 200 is coupled to a resolver 112. The resolver 112 includes a reference winding 202, an x-phase winding 204, and a y-phase winding 206. The reference winding 202 is arranged on a shaft 110. As the shaft 110 rotates, the reference winding 202 rotates relative to the x-phase winding 204 and the y-phase winding 206 of the resolver 112. Figure 2As shown, shaft 110 extends vertically out of the page, and reference winding 202 rotates in the plane of the page. X-phase winding 204 and Y-phase winding 206 are located in a plane transverse to shaft 110 (i.e., within the page) and rotate 90 degrees apart from each other. During rotation, reference winding 202 energizes an x-phase voltage (also referred to herein as a cosine voltage) at x-phase winding 204 and a y-phase voltage (also referred to herein as a sine voltage) at y-phase winding 206. The cosine and sine voltages are sent to processor 208. Processor 208 applies the methods disclosed herein to the cosine and sine voltages to determine faults in resolver 112. Processor 208 can then send or transmit a signal to warning device 210, such as a display or audio alarm system, to indicate that resolver 112 is acceptable or that diagnostic tests have failed. This signal can alert the operator to a defect in the resolver, allowing the operator to replace the resolver.

[0020] Figure 3 A graph 300 shows the original winding voltages received at processor 208 from x-phase winding 204 and y-phase winding 206 due to rotation of reference winding 202. Time is shown in seconds (s) along the horizontal axis and amplitude in volts (V) along the vertical axis. A cosine voltage envelope 302 and a sinusoidal voltage envelope 304 are shown over several rotations of reference winding 202. Due to the spatial relationship between x-phase winding 204 and y-phase winding 206, the cosine voltage envelope 302 and the sinusoidal voltage envelope 304 have a phase relationship of approximately 90 degrees. The cosine voltage envelope 302 has a different amplitude than the sinusoidal voltage envelope 304. This difference may be due to the oscillation of reference winding 202 and / or shaft 110.

[0021] Figure 4 A graph 400 showing the adaptive voltage envelope is illustrated. Time is represented in seconds (s) along the horizontal axis, and amplitude in volts (V) along the vertical axis. The adapted voltage is obtained by compensating for the oscillation of the original voltage. Oscillation compensation normalizes the voltage. Therefore, the adaptive cosine voltage 402 and the adaptive sine voltage 404 have the same amplitude. However, oscillation compensation preserves the phase error in the phase offset between the adaptive cosine voltage 402 and the adaptive sine voltage 404. In various embodiments, the phase error can be ±10 degrees.

[0022] Figure 5 An illustrative graph 500 is shown for the adaptive amplitude 502 based on adaptive cosine voltage and adaptive sine voltage. Time is shown in seconds (s) along the horizontal axis and amplitude in volts (V) along the vertical axis. The adaptive amplitude 502 (Mag) at a given time can be determined from the values ​​of the adaptive sine envelope and the adaptive cosine envelope, as shown in equation (1):

[0023]

[0024] in It is an adaptive sinusoidal voltage, and It is an adaptive cosine voltage. Ideally, when the x-phase winding 204 and the y-phase winding 206 are 90 degrees out of phase, the amplitude is constant with time. However, for the operation of the rotary transformer, the measured values ​​of the cosine voltage envelope 302 and the sinusoidal voltage envelope 304 will differ, and therefore the amplitude will vary with time. Figure 5 As shown, the adaptive amplitude 502 (Mag) fluctuates around a standard value within a region between a lower limit and an upper limit. In various embodiments, the lower limit is approximately 0.985 of the standard value, and the upper limit is approximately 1.015 of the standard value. However, these limits are not intended to limit the invention. When the fluctuation is sufficiently small, the resolver 112 can be considered defect-free. However, when the fluctuation is large, the resolver 112 is considered defective and may be used to replace the resolver and / or the motor. The adaptive amplitude 502 can be compared to an average value (or a standard component rating) to determine whether the resolver is defective.

[0025] The adaptive amplitude of equation (1) can be obtained at multiple times in the formation of the time series. Multiple adaptive amplitudes can then be used to generate an amplitude average (Mag_Avg) or a time average of the amplitude measurement, as shown in equation (2):

[0026]

[0027] Where n is the number of values ​​considered. In various embodiments, Mag_Avg is a rolling average. Therefore, Mag_Avg is determined using n previous Mag values. Mag and Mag_Avg are used to form a ratio.

[0028] The ratio is compared with the threshold, as shown in equation (3):

[0029]

[0030] When the absolute value of the difference between the ratio and the value "1" is greater than a threshold, the resolver is considered defective, and an appropriate signal can be sent to warning device 210. The threshold can be a predetermined value or a value selected by those skilled in the art.

[0031] Figure 6A flowchart 600 of a method for diagnosing a defective resolver is shown. The method begins at block 602. Cosine and sinusoidal voltages are measured, and adaptive cosine envelopes and adaptive sinusoidal envelopes are obtained from the cosine and sinusoidal voltages, respectively. In block 604, an adaptive amplitude (Mag) is obtained using, for example, equation (1). In block 606, the time average of the adaptive amplitude (Mag_Avg) is determined as shown in equation (2). In block 608, a ratio is placed between the adaptive amplitude and the time average. The absolute value of the difference between this ratio and the value "1" is compared with a threshold. If the absolute value of the difference between the ratio and the value "1" is greater than the threshold, the method proceeds to block 610. In block 610, a fault is set to indicate that the resolver is defective. Returning to reference block 608, if the absolute value of the difference is not greater than the threshold, the method proceeds to block 612. In block 612, no fault is set. From block 610 or block 612, the method proceeds to block 614, where the diagnosis ends.

[0032] In real-world environments, resolvers can experience large temperature fluctuations (from -40°C to 150°C). The resistances of the x-phase winding 204 and the y-phase winding 206 change with temperature. Consequently, the amplitudes of the cosine voltage envelope 302 and the sine voltage envelope 304 also change with temperature. Therefore, under extreme temperature conditions, simply observing the amplitudes of the cosine voltage envelope 302 and the sine voltage envelope 304 is insufficient to identify a defective resolver. However, by using equations (2) and (3), where the amplitude of the resolver signal is normalized in real time to generate a ratio, this ratio can be used to detect faults at the resolver. This ratio is consistent across component variations and temperature variations.

[0033] While the foregoing disclosure has been described with reference to exemplary embodiments, those skilled in the art will understand that various changes can be made and elements can be substituted with equivalents without departing from its scope. Furthermore, many modifications can be made to adapt particular situations or materials to the teachings of this disclosure without departing from the basic scope of this disclosure. Therefore, this disclosure is not intended to be limited to the specific embodiments disclosed, but will include all embodiments falling within its scope.

Claims

1. A method for diagnosing a rotary transformer for an electric motor, comprising: The x-phase voltage and y-phase voltage are obtained from the rotary transformer, and swing compensation is performed on the x-phase voltage and the y-phase voltage to normalize the voltage, so as to obtain adaptive cosine envelope and adaptive sine envelope respectively; The adaptive magnitude at a given time is determined from the values ​​of the adaptive sine envelope and the adaptive cosine envelope; The average amplitude is determined based on the adaptive amplitude. as well as The fault of the rotary transformer is determined based on the adaptive amplitude and the amplitude averaging.

2. The method according to claim 1, wherein, The amplitude average is a rolling average determined from adaptive amplitudes at multiple time intervals.

3. The method according to claim 1, further comprising determining the fault when the absolute value of the difference between 1 and the ratio of the adaptive amplitude to the average amplitude is greater than a threshold.

4. The method of claim 1, further comprising determining the fault of the rotary transformer on the electric motor when the electric motor is operatively coupled to the vehicle.

5. A diagnostic system for use with a rotary transformer for an electric motor, comprising: The processor is configured as follows: Obtain the x-phase voltage from the x-phase winding of the rotary transformer and the y-phase voltage from the y-phase winding of the rotary transformer; Swing compensation is performed on the x-phase voltage and the y-phase voltage to normalize the voltage, so as to obtain adaptive cosine envelope and adaptive sine envelope respectively; The adaptive magnitude at a given time is determined from the values ​​of the adaptive sine envelope and the adaptive cosine envelope; The average amplitude is determined based on the adaptive amplitude. The fault of the rotary transformer is determined based on the adaptive amplitude and the amplitude averaging. as well as Based on the fault transmission signal.

6. The diagnostic system according to claim 5, wherein, The amplitude average is a rolling average determined from adaptive amplitudes at multiple time intervals.

7. The diagnostic system according to claim 5, wherein, The signal indicates that the rotary transformer is defective.

8. The diagnostic system according to claim 5, wherein, The processor is also configured to determine the fault when the absolute value of the difference between 1 and the ratio of the adaptive amplitude to the average amplitude is greater than a threshold.

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