Built-in Temperature Detecting System for Diagnosing Ball-Screw Preload Variation of a Feed Drive System

This paper presents a built-in detecting system for precisely measuring temperature of interest points on a ball-screw structure and the method of diagnosing different ball-screw preload based on processing acquired signals with further classification by support vector machines (SVM). The detecting system mainly consists of a sensing unit and a hardware signal processing unit. The core sensor, utilizing a glass-type SMD PT-100 with a Wheatstone bridge circuit configuration, is implemented onto a 1 cm x 1 cm circuit board and then packaged by a metal housing as a sensing unit with a dimension less than 1.5 cm(3). The resolution of the measured temperature can be reached 0.01 degrees C within the range of -40 to 125 degrees C through our developed signal processing circuit unit. A preload-adjustable ball screw is designed, manufactured, and installed into a computer-controlled single-axis feed drive system. The temperature sensing unit is built into the screw nut for acquiring signals with different ball-screw preload level settings. Results show that diagnosis of ball-screw preload can be achieved less than 100 sec, and the preload level classification reaches nearly 100%. The developed built-in temperature detecting system and analysis method demonstrated the feasibility of evaluating ball-screw health condition and would be very useful in many industrial applications.