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Ch30-I044963.fm Page 148 Thursday, July 27, 2006 7:17 AM
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MEASUREMENT INSTRUMENT

The picture of the manufactured sensor system was shown in Figure 4. This structure of sensor body
had two plates with same diameter and six pillars with same size. The each pillar has single axis
accelerometer (Analog Devices Inc., ADXL105) in the central part of the pillar. And, the angle made
by measurement axis of each sensor and plates made 45 degrees each other.

Figure 4: Manufactured device
EXPERIMENTAL RESULT
In order to confirm the validity, the acceleration and angular acceleration were measured while
reciprocating the manufactured detector. The X-Y plane was set on the upper plate, and Z-axis was
vertical to X-Y plane. From the various experimental results, the detected values out of the main
direction of movement were about 1% on the peak value in main direction. Although it could not be
measured strictly by this data, the cross talk could be -35dB at least. From the experimental results of
measurement in translational and rotational reciprocation simultaneously, the error of measured
acceleration value was 15% on the calculated value, and the error of angular acceleration value was 6%.
The error of angular acceleration was similar to the value in only rotational motion. Due to the scatter
in measured performance of each accelerometer, the error of acceleration was increased, we
considered.

CONCLUSION
In this detector, we use only one kind of sensor (ADXL105 in this report) as single axis detector. The
proposed sensing device could measure six components of special motion at once. The maximum
cross axis sensitivity of sensing device is 5%, and it is almost equal to the specifications of each sensor
tips. Totally, the cross talk value is about -35dB. The acceleration and angular acceleration could be
measured by this method in translational and rotational motion respectively. In experimental
confirmation, the amplitude of acceleration was about 0.01 m/s (about 5% on the peak value).
Assuming that this value would be electrical noise of acceleration sensor tips, the acceleration and
angular acceleration could be measured in translational and rotational motion simultaneously without
calculating errors. From the results of experimental confirmation, it has been clear that new type of
sensor device, which was designed based on the fixed Stewart Platform by us, would be essential way
to construct the various kind of six component sensing device.

Reference
D. Stewart (1965), A Platform with Six Degrees of Freedom, UK Institution of Mechanical
Engineers Proceedings 1965-66, 180:Pt 1:15