Diagnostic rule base tool condition monitoring system

• US 6,308,138 B1
• Filed: 07/28/1997
• Issued: 10/23/2001
• Est. Priority Date: 07/28/1997
• Status: Expired due to Fees

• Current Assignee: Tri-Way Manufacturing Technologies
• Original Assignee: Tri-Way Machine Limited
• Inventors: Wu, Ya, Jones, Joel W.
• Primary Examiner(s): WACHSMAN, HAL D
• Application Number:
  US08/901,609
• Time in Patent Office: 1,548 Days
• Field of Search: 702/34, 702/35, 702/42-44, 702/57, 702/60, 702/61, 702/71, 702/64-66, 702/79, 702/81, 702/82, 702/176-178, 702/179, 702/182-185, 702/189, 702/193, 702/FOR-135, 702/FOR.170, 702/FOR.171, 702/FOR.103, 702/FOR.104, 702/FOR.106, 364/140.04, 364/140.09, 364/184, 364/185, 364/468.15, 364/486.16, 364/468.17, 364/474.01, 364/474.02, 364/474-5-4, 364/474.19, 364/474.2, 364/474.22, 364/474.34, 364/474.35, 364/528.1, 364/528.21, 364/528.3, 364/528-6-5, 364/528.31, 340/680, 340/683, 735/93, 731/04, 736/60, 318/565-567, 388/909, 408/11, 408/6, 408/8, 408/16, 409/134, 409/193, 409/194, 706/904, 706/912, 700/174, 700/175, 451/5, 451/8, 451/21
• US Class Current: 702/34
• CPC Class Codes: G05B 19/4065 Monitoring tool breakage, life or condition
• CPC Class Codes: G05B 2219/37252 Life of tool, service life, decay, wear estimation

Abstract

A tool condition monitoring system monitors the power consumption of a tool during performance of a cyclical task. The system monitors a plurality of characteristics of the power consumption and diagnoses the condition of the tool based upon the plurality of characteristics. A rule base of the plurality of characteristics is generated in a learning mode by monitoring a tool of known condition for a plurality of cycles. In monitor mode, the system monitors the power consumption of a tool and diagnosis the condition of the tool by indexing the rule base based upon the plurality of characteristics monitored.

Claims

1. A method for monitoring the condition of an electric motor powered tool including the steps of:

a. monitoring the power consumption of the electric motor powered tool during performance of a cyclical task;

b. counting the number of crossings by said power consumption of a power threshold;

c. comparing the number of crossings to a predetermined number;

d. comparing said power consumption to a predetermined maximum value;

e. monitoring an amount of time that said power consumption is above and below said power threshold;

f. comparing said amount of time to a predetermined time value;

g. creating a rule base encompassing a plurality of combinations of possible outcomes of the comparisons of steps c), d) and f);

h. associating each of said plurality of combinations with an associated potential condition of said electric motor powered tool;

i. diagnosing said condition of said electric motor powered tool by indexing said rule base based upon said steps c), d) and f);

j. indicating said condition of said electric motor powered tool.

2. A system for monitoring the condition of an electric tool comprising:

means for measuring the power consumption of said electric tool during performance of a cyclical task;

means for monitoring a plurality of characteristics of said power consumption during said cyclical task; and

means for diagnosing the condition of said electric tool based upon the combination of states of said plurality of characteristics, including a rule base encompassing a plurality of combinations of said plurality of characteristics, said rule base associating each of said plurality of combinations with an associated condition of said electric tool, and wherein said means for diagnosing the condition of said electric-powered tool indexing said rule base based on said monitored plurality of characteristics.

3. The system of claim 2 further including:

means for assigning a value for each of said plurality of characteristics;

said means for diagnosing diagnosing said condition based upon said values.

4. The system of claim 2 further including:

said means for diagnosing comparing said power consumption to a power threshold having an upper limit and a lower limit;

said means for diagnosing determining whether each of said plurality of characteristics occurs above an upper limit;

said means for diagnosing determining whether each of said plurality of characteristics occurs below a lower limit;

said means for diagnosing diagnosing based upon whether each of said plurality of characteristics occurred above the upper limit, below the lower limit or both.

5. A method of monitoring the condition of an electric-powered tool, comprising:

a) operating the electric-powered tool in a learning mode during performance of a cyclic task while monitoring a power consumption signal of the electric-powered tool having a plurality of distinct operational characteristics associated with the power consumption signal;

b) processing the power consumption signal and generating a diagnostic rule base comprising a plurality of different combinations of the operational characteristics each associated with a different operational condition of the electric-powered tool;

c) continuing to operate the electric-powered tool in a monitoring mode while performing the cyclic task and monitoring the power consumption signal of the electric-powered tool;

d) comparing the plurality of distinct operational characteristics associated with the power consumption signal from step c) with the diagnostic rule base; and

e) diagnosing the existence of any of a number of particular operational conditions of the electric-powered tool by identifying a match between at least one combination of the plurality of combinations of operational characteristics associated with the power consumption signal monitored in step c) with a corresponding combination of operational characteristics of the diagnostic rule base.

6. The method of claim 5 wherein each of the characteristics is either absent or present, said method further including the step of diagnosing the condition of the electric-powered tool based upon the absence or presence of each of the plurality of operational characteristics.

7. The method of claim 6 further including the step of diagnosing the condition of the electric-powered tool based upon the presence of at least two of the plurality of characteristics.

8. The method of claim 5 wherein said plurality of different combinations of the operational characteristics includes all possible permutations of the plurality of operational characteristics, said method further including the step of indexing the diagnostic rule base based upon the permutations of the plurality of operational characteristics.

9. The method of claim 8 wherein said plurality of operational characteristics includes a first characteristic and a second characteristic, said first characteristic including a first upper threshold and a first lower threshold, said second characteristic including a second upper threshold and a second lower threshold.

10. The method of claim 5 wherein each of said plurality of operational characteristics includes four possible values, said method further including the step of indexing the diagnostic rule base based upon the four possible values.

11. the method of claim 10 further including the step of multiplying each of the four possible values of each of the characteristics by a different multiple of a base number to produce an index number, said method further including the step of indexing the diagnostic rule base based upon the index number.

12. The method of claim 5 wherein step b) includes assigning a value for each of said plurality of operational characteristics.

13. The method of claim 5 wherein step b) includes assigning an upper and lower limit of a power threshold of the electric-powered tool, and wherein steps d) and e) includes determining whether each of said plurality of operational characteristics of the power consumption signal occurs above the upper limit, below the upper limit, or both above and below the upper and lower limits, respectively.

14. The method of claim 13 wherein steps d) and e) further include counting the number of crossings of the power threshold limits by the power consumption signal and comparing the counted number of crossings to a predetermined number in diagnosing the operational condition of the electric-powered tool.

15. The method of claim 14 wherein step b) includes assigning a predetermined maximum value of the power consumption signal, and steps d) and e) includes comparing the monitored power consumption signal to the predetermined maximum value.

16. The method of claim 15 wherein step b) includes assigning a predetermined time value that power consumption operates above and below the power threshold limits, and in steps c) and d) monitoring an amount of time that the monitored power consumption signal spends above and below the power threshold limits and comparing the monitored time value to the predetermined time value.

17. The method of claim 5 wherein step a) includes operating the electric powered tool in the learning mode for a plurality of cyclic cycles.