Diagnostic rule tool condition monitoring system

• US 6,260,427 B1
• Filed: 11/25/1998
• Issued: 07/17/2001
• 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): NOORI, MAX H
• Application Number:
  US09/200,017
• Time in Patent Office: 965 Days
• Field of Search: 738/658, 738/659, 340/679, 340/680
• US Class Current: 73/865.9
• CPC Class Codes: G01N 3/58 Investigating machinability by cutting tools; Investigating the cutting ability of tools
• CPC Class Codes: G05B 19/4065 Monitoring tool breakage, life or condition
• CPC Class Codes: G05B 2219/50203 Tool, monitor condition tool

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 acquiring 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. In addition, a method is disclosed wherein the band may be modified for accommodating tool wear and avoiding nuisance detection such that the system can keep monitoring in tool'"'"'s lifetime.

Claims

1. A method for monitoring the condition of an electric powered tool, comprising:

measuring a power consumption signal of the tool while performing a cyclical task;

analyzing selected feature components of the power consumption signal and establishing an initial power threshold tolerance band of predetermined value in a learning mode of the tool;

continuing to use the tool in a monitoring mode while performing the cyclic task and monitoring a plurality of selected feature components of the power consumption signal;

comparing the monitored power consumption signal with the initial power threshold tolerance band and based on the comparison, diagnosing the condition of the tool;

designating at least one combination of the plurality of selected feature components of the power consumption signal as a relearning code representative of a condition of tool wear; and

during the monitoring of said power consumption signal, comparing the monitored power consumption signal to the relearning code and, in response to a detection that the monitored power consumption signal corresponds to said relearning code, recalculating and adjusting the initial power threshold tolerance band while operating in a relearning mode of the tool.

2. The method of claim 1 including using prior captured signal information to establish defined outer operational limits of an acceptable power threshold tolerance band.

3. The method of claim 2 wherein during the recalculation of the power threshold tolerance band, comparing the monitored signal information to the prior captured signal information to maintain the recalculated and adjusted power threshold tolerance band within the outer operational limits.

4. The method of claim 3 wherein the initial power threshold tolerance band has a corresponding area defined below the band, and wherein the recalculation of the band is made in relation to said area.

5. A method of monitoring a tool operation, comprising:

operating a tool in a learning mode while measuring defined operational characteristics of the tool;

analyzing the measured operational characteristics and calculating an initial operational tolerance band representative of a desired operating performance of the tool;

further operating the tool in a production mode while monitoring the operational characteristics of the tool;

designating at least certain operational characteristics as relearning code characteristics representative of a condition of the tool when experiencing tool wear;

while operating the tool in the production mode, comparing the monitored operational characteristics with the relearning code characteristics and, in response to detection that the monitored operational characteristics correspond to the relearning load characteristics, recalculating and adjusting the initial operational tolerance band in a relearning mode of the tool.

6. The method of claim 5 wherein the monitoring of the tool in the production and relearning modes includes monitoring a plurality of said operational characteristics.

7. The method of claim 6 wherein said operation characteristics of the tool measured in the learning mode includes a plurality of cycle codes representative of a operation cycle of the tool, and wherein said operational characteristics measured in said relearning mode are compared to said plurality of said cycle codes in said recalculation of said initial operational tolerance band.

8. The method of claim 7 including employing a user-defined quantity of said operation cycles for comparison in said relearning mode.

9. The method of claim 5 wherein the initial operational tolerance band includes upper and lower band limits and a defined area under said limits, and wherein said initial operational tolerance band is adjusted based on the difference between the initial position of said upper and lower band limits and said defined area and said plurality of said operation cycles.

10. The method of claim 5 wherein said initial operational tolerance band includes upper and lower band limits and including defined outer limits, and including controlling the adjustment of said initial operational tolerance band such that said band limits remain within said outer limits.

11. The method of claim 10 including calculating said outer limits based on a standard deviation of a calculated area below said upper and lower band limits.

12. The method of claim 10 including calculating said outer limits based on an acceptable standard deviation difference between said upper and lower band limits.

13. A method of monitoring a tool operation comprising the steps of:

1) operating said tool in a learning mode and capturing samples of selected operational characteristics associated with an operation cycle of said tool;

2) analyzing said capture sample characteristics to define an operational tolerance band having an upper limit and a lower limit of expected operation;

3) defining an extreme upper limit and an extreme lower limit relation to a standard deviation difference between said upper band limit and said lower band limit;

4) operating said tool in a production mode;

5) capturing selected operational characteristics of each operational cycle of said tool during said production mode;

6) storing some of said captured operational characteristics to define relearning code characteristics of said tool;

7) comparing said captured operational characteristics of each operational cycle to said stored relearning code characteristics; and

8) adjusting said upper band limit and said lower band limits within said extreme upper and lower limits should said captured operational characteristics match said relearning code characteristics.