Method and apparatus for statistical process control of machines and processes having non-constant mean of a response variable
First Claim
1. A method for analyzing a process or machine having a non-constant mean value of a response variable using statistical process control techniques comprising the steps of:
- identifying an indicator variable which varies in correlation with said mean value of said response variable;
measuring said response variable while the process or machine is operating in control;
deriving a mathematical formula correlating said indicator variable to said mean value of said response variable for predicting said mean value based on a value of said indicator variable;
measuring actual values of said response variable during ongoing operation of the process or machine; and
applying statistical process control rules by comparing said measured actual values to said predicted mean value of said response variable based on a current value of said indicator variable.
1 Assignment
0 Petitions
Accused Products
Abstract
A method and apparatus for analyzing a process or machine having a non-constant mean of a response variable using statistical process control techniques. Several measurements of a response variable are taken while the monitored machine is known to be operating in control. Through statistical regression techniques, a mathematical formula is derived to predict the value using indicator variables at various periods in the process. Then, while the process or machine is operating on an ongoing basis, actual measurements of the response variable are taken and compared to the predicted values using indicator variables calculated from the derived formula. Statistical process control rules are applied to the measured values of the response variable and the predicted value using indicator variables to determine if the machine or process has fallen out of control.
-
Citations
15 Claims
-
1. A method for analyzing a process or machine having a non-constant mean value of a response variable using statistical process control techniques comprising the steps of:
-
identifying an indicator variable which varies in correlation with said mean value of said response variable; measuring said response variable while the process or machine is operating in control; deriving a mathematical formula correlating said indicator variable to said mean value of said response variable for predicting said mean value based on a value of said indicator variable; measuring actual values of said response variable during ongoing operation of the process or machine; and applying statistical process control rules by comparing said measured actual values to said predicted mean value of said response variable based on a current value of said indicator variable. - View Dependent Claims (2, 3, 4, 11)
-
-
5. An apparatus for analyzing a process or machine having a non-constant mean value for a response variable and an indicator variable which varies with said mean value of said response variable, the apparatus using statistical process control techniques and comprising:
-
circuitry for measuring said response variable while the process or machine is operating in control; circuitry for correlating said indicator variable with said non-constant mean value of said response value for predicting an expected mean value of said response variable based on a current value of said indicator variable; circuitry for measuring actual values of said response variable during ongoing operation of the process or machine; and circuitry for applying statistical process control rules by comparing said measured actual response values to an expected mean value of said response variable based upon said indicator variable. - View Dependent Claims (6)
-
- 7. A method for analyzing output of a process or machine having a non-constant mean value of a response variable, wherein an indicator variable varies in correlation to said mean value of said response variable, the method comprising comparing actual measured values of said response variable to an expected means value of said response variable calculated based on said indicator variable using said correlation between said indicator variable and said non-constant mean value of said response variable, wherein said actual values of said response variable are measured during on going operation of the process or machine.
-
12. An apparatus for analyzing a process or machine having a non-constant mean value for a response variable, said process or machine also having an indicator variable which varies in correlation with said mean value of said response variable, the apparatus comprising:
-
circuitry for measuring actual values of said response variable while the process or machine is operating; circuitry for comparing said measured actual values of said response variable to an expected mean value of said response variable which is calculated based upon said correlation between said non-constant mean value of said response variable and said indicator variable. - View Dependent Claims (13, 14, 15)
-
Specification