Description of our
Instrumentation
and Data Collection System
We
currently have four different types of instrumented grinders available at the
Machining, Inspection, and Tribology User Center (MITUC). All four grinders are
equipped with instrumentation packages and data collection systems that are
virtually identical, as described below.
Software
The
instrumentation and data collection system was developed for MITUC by Controlink
Systems, LLC, located in Lawrenceburg, IN. This customized software provides
a framework for the entire system, making it very easy to collect grinding data
in real time. The software also has its own internal analysis routines, or the
data can be exported to other products such as DADiSP (a data display and
analysis package from DSP Corporation) or even Microsoft Excel. The system
hardware includes a number of off-the-shelf sensors, whose signals are processed
by a National Instruments
AT-MIO-series data acquisition board.
The
system software consists of a series of customized virtual instrument windows,
created in Labview®. Using the virtual instrument window concept, data can be
displayed in near real-time for the following variables:
-
X, Y, and Z forces
-
Spindle vibration
-
Spindle horsepower
-
Acoustic emission
-
Coolant Temperature
-
Spindle speed
Additional
features of the real-time data-acquisition system include:
-
User selectable gain
settings, sensitivity settings, and maximum sampling rate
-
Selectable sampling rates
for individual channels
-
User control over which
channels are stored to disk
-
User control over when the
information is stored to hard disk
Hardware
The
real-time data collection system consists of several subsystems:
Force
measurement subsystem This subsystem uses four Kistler Instruments piezoelectric
force transducers to measure x, y, and z components of force. The charge yielded
by the quartz crystals is converted to a proportional voltage by the Kistler
charge amplifier. The amplifier signal is captured by the National Instruments
AT-MIO card, which is installed in an IBM-compatible PC.
Spindle
horsepower measuring subsystem This subsystem determines true spindle horsepower
by means of a load control unit which measures voltage, current and power
factor. It has extremely high sensitivity and linear output at low loads.
Spindle
vibration measurement subsystem This subsystem measures spindle vibration by
means of a piezo transducer (accelerometer) mounted on the spindle housing. A
charge amplifier is used to convert the signal from the transducer into a
low-impedance voltage signal. The amplifier has seven user-selectable gain
settings and four different low pass filters between 100 and 30 kHz.
Acoustic
emission measurement subsystem The acoustic emission spectrum is measured using
a Model I151 acoustic emission sensor, manufactured by Physical Acoustics Corp.
The sensor has a usable range between 100 and 400 kHz.
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