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G. Li et al.
hydraulic, fuel manifold, air conditioning, portable water galley, auxiliary power
unit, oxygen line, manometric line, and thrust reverser door actuator systems. On
the other hand, they are assembled on the aircraft’s overall frame as a structure to
increase the overall stiffness and strength of the aircraft. Not only does the exterior
of these tubular components withstand high and low temperature and high frequency
vibration, but the interior also withstands the pulsating impact of the fluid medium,
so that their working conditions are very harsh [3]. Thus, the manufacturing and
assembling of aviation tubular components are highly concerned.
At present, tubular bent components are fabricated by numerical control bending
[1, 4]. Their shapes are inspected by means of laser-measurement [5, 6], and special
software is used to compare the difference between the measured shape and the
theoretical shape [7–9], so as to realize the digital inspection of aviation tubing.
The above technologies only inspect the tubing as a part, and they adopt the best
fitting in the comparison process. Thus, there is no clear detection datum, so that the
assembling positioning datum in the aircraft is not considered.
Due to the difference between the inspection datum just for the tubing in the status
of parts and assembly positioning datum of the tubing in the assembling status, the
deviation of tubing shape and that of assembling positioning can not correspond
individually. There are often misjudgement situations of “positive judgment for the
unqualified (PJN)”, i.e., parts that can not meet the assembly requirements are judged
to be qualified and “misjudgement for the qualified (MJQ)”, i.e., parts that can meet
the assembly requirements are judged to be unqualified. Therefore, it is necessary
to integrate the inspection datum of parts and the assembling positioning datum
and to divide the deviations of tubing shape, and finally solving the problem of
misjudgement of tubing accuracy.
4.2 Tubing Inspection Method
The tubing in the aircraft is generally made of metal, for instance, titanium alloy [10],
aluminum alloy [11] and stainless steel [12], etc. Its shape is composed of line sections
and bent sections alternately and its cross section is the standard circle. Accordingly,
the tubing shape can be directly determined through the centerline, and the inspection
datum and assembling positioning datum can be unified. As shown in Fig. 4.1, the
central point of the fixed joint and the locating point of the clamp are used as the
reference points to calculate the shape deviation of the tubing. The correspondence
between the deviation of tubing shape, viz., axial deviation, radial deviation and angle
deviation and the deviation of tubing assembling position, viz., the butt clearance,
misalignment and angle deviation can be obtained. The occurrence of PJN and MJQ
can be avoided, and the requirements of manufacturing and assembling of the tubing
are satisfied. In order to realize this digital inspection, the key technical issues, viz.,
assembling datum analysis, centerline data extraction, measuring datum fitting and
assembly accuracy analysis, need to be investigated.
G. Li et al.
hydraulic, fuel manifold, air conditioning, portable water galley, auxiliary power
unit, oxygen line, manometric line, and thrust reverser door actuator systems. On
the other hand, they are assembled on the aircraft’s overall frame as a structure to
increase the overall stiffness and strength of the aircraft. Not only does the exterior
of these tubular components withstand high and low temperature and high frequency
vibration, but the interior also withstands the pulsating impact of the fluid medium,
so that their working conditions are very harsh [3]. Thus, the manufacturing and
assembling of aviation tubular components are highly concerned.
At present, tubular bent components are fabricated by numerical control bending
[1, 4]. Their shapes are inspected by means of laser-measurement [5, 6], and special
software is used to compare the difference between the measured shape and the
theoretical shape [7–9], so as to realize the digital inspection of aviation tubing.
The above technologies only inspect the tubing as a part, and they adopt the best
fitting in the comparison process. Thus, there is no clear detection datum, so that the
assembling positioning datum in the aircraft is not considered.
Due to the difference between the inspection datum just for the tubing in the status
of parts and assembly positioning datum of the tubing in the assembling status, the
deviation of tubing shape and that of assembling positioning can not correspond
individually. There are often misjudgement situations of “positive judgment for the
unqualified (PJN)”, i.e., parts that can not meet the assembly requirements are judged
to be qualified and “misjudgement for the qualified (MJQ)”, i.e., parts that can meet
the assembly requirements are judged to be unqualified. Therefore, it is necessary
to integrate the inspection datum of parts and the assembling positioning datum
and to divide the deviations of tubing shape, and finally solving the problem of
misjudgement of tubing accuracy.
4.2 Tubing Inspection Method
The tubing in the aircraft is generally made of metal, for instance, titanium alloy [10],
aluminum alloy [11] and stainless steel [12], etc. Its shape is composed of line sections
and bent sections alternately and its cross section is the standard circle. Accordingly,
the tubing shape can be directly determined through the centerline, and the inspection
datum and assembling positioning datum can be unified. As shown in Fig. 4.1, the
central point of the fixed joint and the locating point of the clamp are used as the
reference points to calculate the shape deviation of the tubing. The correspondence
between the deviation of tubing shape, viz., axial deviation, radial deviation and angle
deviation and the deviation of tubing assembling position, viz., the butt clearance,
misalignment and angle deviation can be obtained. The occurrence of PJN and MJQ
can be avoided, and the requirements of manufacturing and assembling of the tubing
are satisfied. In order to realize this digital inspection, the key technical issues, viz.,
assembling datum analysis, centerline data extraction, measuring datum fitting and
assembly accuracy analysis, need to be investigated.