US 5,587,931 A · Tool condition monitoring system

Abstract

A tool monitoring system monitors the condition of an electrically powered tool performing a cyclical operation. The tool monitoring system operates generally in two modes: learning mode and monitor mode. In learning mode, the tool monitoring system gathers statistical data on the power consumption of tools of the selected tool type during learning cycles. A power threshold is generated based upon the statistical data. The tool monitoring system then counts the number of crossings by each of the learning cycles of the power threshold and generates statistical data regarding the number of crossings. Preferably, the mathematical operation of wavelet packet transform is used to calculate the power threshold. Feature wavelet packets of the power consumption signal of the tool are calculated. The power consumption signal is then reconstructed from the feature wavelet packets and used to determine the power threshold. In monitor mode, the tool monitoring system counts the number of crossings of the power threshold by the power consumption signal of a tool in operation. The tool monitoring system identifies a worn tool when the number of crossings increases to a certain number relative to the crossings by the learning cycles.

Claims18

Dependent claims

A method for monitoring the condition of an electrically powered tool of a selected tool type performing a cyclical task comprising the steps of:

a. using a tool to perform a cyclical task and measuring a power consumption signal of said tool as said tool performs said cyclical task;
b. decomposing said power consumption signal of said tool into components by converting said power consumption signal into time segments, each time segment having a digital value equivalent to the analog value of said signal at said time, and decomposing said time segments of said power consumption signal into different frequency components using a mathematical algorithm;
c. selecting feature components of said power consumption signal;
d. using said selected components of said power consumption signal to set a power threshold in a learning cycle;
e. using a tool to perform a cyclic task and monitoring its power consumption signal;
and
f. identifying a worn condition of the tool of step e. based upon a comparison of said power consumption signal with said predetermined power threshold of step d.

4 more elements

A method for monitoring the condition of an electric motor powered tool of a selected tool type comprising the steps of:

a. using a first tool to perform a plurality of cyclical tasks, and measuring a power consumption signal of said first tool as said first tool performs said plurality of cycles of cyclical task;
b. decomposing said power consumption signal of each said cycle of said first tool into components;
c. selecting feature components of said components of said power consumption signal;
d. reconstructing said power consumption signal from said feature components;
e. generating a power threshold based upon said reconstructed power consumption signal of said first tool, said power threshold including an upper limit for said power consumption signal;
f. counting the number of crossings of said power threshold by said power consumption signal of said first tool while performing a plurality of cycles of said cyclical task;
g. using a second tool to perform said cyclical task, and measuring the power consumption signal of said second tool as said second tool performs said cyclical task;
h. counting the number of crossings of said power threshold by said power consumption signal of said second tool;
i. comparing the number of crossings of said power threshold by said second tool with the number of crossings of said power threshold by said first tool;
and
j. signalling a worn condition of said second tool when the number of crossings of said power threshold by said second tool exceeds the number of crossings of said power threshold of said first tool by a predetermined amount in a predetermined time frame.

8 more elements

Dependencies are inferred from the claim text.

Tool condition monitoring system

Life of this patent

Tool condition monitoring system

Life of this patent

Abstract

Claims18