Condition-Based Maintenance Optimization for Motorized Spindles Integrating Proportional Hazard Model with SPC Charts

Table 1

Characteristics of four typical SPC charts.

Feature	Monitored statistic	Control limits
Shewhart
MA
CUSUM
EWMA
	Monitored variable at t		The mean of in-control data
	The standard deviation of in-control data	n	Control limit width
W	Moving average width	k	The slope of the lower arm
D	Distance typically set to 10	λ	The weighted parameter,
UCL	Upper control limit	LCL	Lower control limit