Distributed diagnostic system

• US 6,199,018 B1
• Filed: 03/04/1998
• Issued: 03/06/2001
• Est. Priority Date: 03/04/1998
• Status: Expired due to Term

• Current Assignee: Emerson Electric Company
• Original Assignee: Emerson Electric Company
• Inventors: Henderson, Michael I., Grudkowski, Thomas W., Lynch, James P., Divljakovic, Vojislav, Quist, Nancy L., Buckley, George William, Kline, Joseph A. Sr., Alguindigue, Israel E., Bonnett, Austin H., Hannula, Ronald Ivar Jr., Bauer, Robert P.
• Primary Examiner(s): SHAH, KAMINI S
• Application Number:
  US09/034,767
• Time in Patent Office: 1,098 Days
• Field of Search: 702/34, 702/181, 702/182, 702/183, 702/56, 702/54, 706/20, 706/912, 318/806, 700/286
• US Class Current: 702/34
• CPC Class Codes: G01M 13/028 Acoustic or vibration analysis
• CPC Class Codes: G01M 13/045 Acoustic or vibration analysis
• CPC Class Codes: G05B 2219/24053 Diagnostic of controlled machine
• CPC Class Codes: G05B 2219/24058 Remote testing, monitoring independent from normal control by pc
• CPC Class Codes: G05B 2219/24067 Processor stores variables, events and date in eeprom, for external monitor
• CPC Class Codes: G05B 23/0213 Modular or universal configuration of the monitoring system, e.g. monitoring system having modules that may be combined to build monitoring program; monitoring system that can be applied to legacy systems; adaptable monitoring system; using different communication protocols
• CPC Class Codes: G05B 23/0221 Preprocessing measurements, e.g. data collection rate adjustment; Standardization of measurements; Time series or signal analysis, e.g. frequency analysis or wavelets; Trustworthiness of measurements; Indexes therefor; Measurements using easily measured parameters to estimate parameters difficult to measure; Virtual sensor creation; De-noising; Sensor fusion; Unconventional preprocessing inherently present in specific fault detection methods like PCA-based methods
• CPC Class Codes: Y10S 706/912 Manufacturing or machine, e.g. agricultural machinery, machine tool

Abstract

A distributed diagnostic system in which a plurality of local monitoring devices collect local information concerning various machines and process that information, according to redefined diagnostic parameters, for diagnostic purposes. The local information collected by the plurality of local monitoring devices is provided to a global processor that globally processes the collected information to provide updated diagnostic parameters to the local monitoring devices.

Claims

1. A distributed diagnostic system for monitoring a plurality of machines, the system comprising:

a plurality of local monitoring devices, each local monitoring device having;

sensors for collecting local data concerning at least one machine associated with the local monitoring device;

a local data processor for receiving and communicating the local data from the sensors concerning its associated machine;

a centralized data processor coupled to the plurality of local monitoring devices, the centralized data processor for receiving from each local monitoring device the local data concerning its associated machine, for generating a set of weighting parameters for each local monitoring device, and for communicating the set of weighting parameters to each local monitoring device; and

the local data processor of each local monitoring device further for receiving the set of weighting parameters, and analyzing the local data using the set of weighting parameters for local diagnostic purposes.

2. An apparatus for locally monitoring a rotating electric machine for diagnostic purposes, the apparatus comprising:

a set of sensors positioned with respect to the rotating electric machine to provide sensor information indicative of the operation of the rotating electric machine, at least one sensor of the set of sensors being an environmental sensor for providing environmental information indicative of an environmental condition of the machine;

load determination means for generating machine load information indicative of a machine load; and

a programmed processor for receiving the sensor information from the set of sensors, normalizing the sensor information based on the machine load information and the environmental information to provide normalized information that is independent of the machine load and the environmental condition of the machine, and for processing the normalized information to provide an output signal indicative of the diagnostic condition of the rotating electric machine.

3. The apparatus of claim 2 further comprising a communication link, and a communication board electrically coupled to the programmed processor and to the communication link, the communication board being adapted to communicate information and data over the communication link.

4. The apparatus of claim 2 further including a visual indicator electrically coupled to the processor for receiving the output signal generated by the processor, and for providing a visual indication of the diagnostic condition of the rotating electric machine based on the output signal.

5. The apparatus of claim 2 wherein the rotating electric machine includes at least one bearing structure and a phase winding and wherein the set of sensors includes:

at least one sensor positioned to provide an electrical signal corresponding to the temperature of the bearing structure;

at least one sensor positioned to provide an electrical signal corresponding to the temperature of the phase winding; and

at least one sensor positioned to provide an electrical signal corresponding to the temperature of the environment in which the rotating electric machine is operating.

6. The apparatus of claim 5 wherein the set of sensors includes at least one flux sensor that is positioned to provide an electrical signal corresponding to the magnitude of the electric flux existing in the rotating electric machine.

7. The apparatus of claim 5 wherein the rotating electric machine includes at least one endshield structure for holding the at least one bearing assembly and wherein the at least one temperature sensor is embedded in the endshield.

8. The apparatus of claim 6 wherein the at least one flux sensor includes a magnetoresistive circuit.

9. An apparatus for locally monitoring a rotating electric machine for diagnostic purposes, wherein the rotating electric machine includes an insulated phase winding, the apparatus comprising:

a programmed processor; and

a set of sensors having outputs coupled to the programmed processor, each sensor being positioned with respect to the rotating electric machine to provide output information at each output concerning the operation of the rotating electric machine, the set of sensors including an insulation failure sensor comprising;

a conductive element having a first end and an uninsulated conductive portion that is wound about a portion of the insulated phase winding; and

a detection circuit coupled to the first end of the conductive element for detecting the presence of an electrical connection between the uninsulated conductive portion and the portion of the insulated winding, thereby detecting an insulation failure,

wherein the programmed processor (i) receives the output information from the set of sensors and normalizes the output information to provide normalized information that is independent of the machine load or the environmental conditions in which the machine operates, and (ii) processes the normalized information to provide an output signal indicative of the diagnostic condition of the rotating electric machine.

10. An apparatus for locally monitoring a rotating electric machine for diagnostic purposes, wherein the rotating electric machine includes at least one bearing structure and a phase winding, the apparatus comprising:

a programmed processor; and

a set of sensors having outputs coupled to the programmed processor, each sensor being positioned with respect to the rotating electric machine to provide output information at each output concerning the operation of the rotating electric machine, the set of sensors including;

at least one sensor positioned to provide an electrical signal corresponding to an ambient temperature of the bearing structure;

at least one sensor positioned to provide an electrical signal corresponding to a temperature of the phase winding; and

at least one sensor positioned to provide an electrical signal corresponding to a temperature of the environment in which the rotating electric machine is operating,

wherein the programmed processor (i) receives the output information from the set of sensors and normalizes the output information to provide normalized information that is independent of the machine load or the environmental conditions in which the machine operates, and (ii) processes the normalized information to provide an output signal indicative of the diagnostic condition of the rotating electric machine, and

wherein the programmed processor normalizes the bearing structure and phase winding temperature information to provide normalized temperature information that is independent of the machine load or the environmental conditions in which the machine operates, in accordance with the following equation;

11. Apparatus for producing an electrical signal indicative of the rotational speed frequency of the rotor of an induction machine comprising:

a flux sensor positioned to provide an output signal that corresponds to the flux in the induction machine;

a comparator having an output, a first input and a second input, the first input receiving a reference voltage signal and the second input receiving the output of the flux sensor, the comparator producing at its output a signal having a first logic state whenever the voltage at the first input is greater than the voltage at the second input and a second logic state whenever the voltage at the second input is greater than the voltage at the first input; and

means coupled to the output of the comparator for producing an electrical signal corresponding to the frequency at which the output of the comparator changes states, wherein the electrical signal is indicative of the rotational frequency of the rotor.

12. A method of determining the slip of an induction machine having a rotor and a stator, the rotor defining a rotational frequency and the stator defining a synchronous frequency, the method comprising the steps of:

monitoring the flux passing through a portion of the induction machine and providing an electrical signal corresponding to the flux;

deriving a first digital signal corresponding to the frequency at which the electric signal corresponding to the flux varies from above a predetermined value to below the predetermined value, the first digital signal corresponding to the rotational frequency of the rotor;

determining the major frequency component of the electrical signal corresponding to the flux and deriving a second digital signal corresponding to the major frequency component, the second digital signal corresponding to the synchronous stator frequency; and

determining the slip S of the induction machine in accordance with the following equation;

13. A monitoring device for use in monitoring an electric machine, the monitoring device comprising:

a programmed processor; and

a set of sensors having outputs coupled to the programmed processor, each sensor being positioned with respect to the electric machine to provide information at its output concerning the operation of the electric machine;

means operatively associated with the programmed processor for operating the processor in a birth certificate mode wherein the outputs of the sensors are processed by the programmed processor and stored as baseline operational parameters;

means associated with the programmed processor for operating the device in a monitoring mode, after the programmed processor has been operated in the birth certificate mode, wherein the programmed processor processes the outputs from the sensors, compares the processed outputs to the baseline operational parameters, and provides an indication of the diagnostic condition of the electric machine based on the comparison.

14. The device of claim 13 wherein the sensor set includes a vibration sensor and the baseline operational parameters include:

(i) the vibration sensor mean;

(ii) the vibration sensor variance;

(iii) the vibration sensor range;

(iv) the overall vibration characteristics of the machine; and

(v) predefined characteristic vibration spectrum frequencies of the machine.

15. The device of claim 13 wherein the sensor set includes an accelerometer for measuring the acceleration of the electric machine, a voltage sensor for sensing the electric voltage applied to the electric machine, and a temperature for sensing the temperature of at least a portion of the machine.

16. The device of claim 13 further including a flash memory device coupled to the programmed processor for storing the baseline operating parameters.

17. The device of claim 13 further including means associated with the programmed processor for operating the device in a learning mode to determine the typical load associated with the electrical machine and wherein the means for operating the device in the monitoring mode provides an indication of the diagnostic condition of the electric machine based at least partially on the typical load.

18. A method of determining the load characteristics of an electric machine, the method comprising the steps of:

using an electrical sensor set to periodically monitor the temperature of at least a portion of the electric machine and the rotational speed of the electric machine at given points in time over a first extended period and, for each point in time, storing in a digital memory a data couplet containing information concerning the temperature, the rotational speed, and the point in time;

using a digital processor to identify couplets having temperature values within a predetermined temperature range; and

providing an indication of a steady state load if the temperature readings for at least a first predetermined number of couplets are within a first predetermined temperature range and the speed readings for the at least a first predetermined number of couplets are within a first predetermined speed range;

or

providing an indication of an ON/OFF load if, for at least a second number of couplets, the following condition is true;

speed at k−

3=speed at k−

2=speed at k−

1=speed at k and temp at k−

3<

temp at k−

2<

temp at k−

1<

temp at k, where k corresponds to the time of the couplet, and k−

x corresponds to the time of the xth preceding couplet.