A coaxial alignment method for large aircraft component assembly using distributed monocular vision

Abstract

Purpose The assembly of large component in out-field is an important part for the usage and maintenance of aircrafts, which is mostly manually accomplished at present, as the commonly used large-volume measurement systems are usually inapplicable. This paper aims to propose a novel coaxial alignment method for large aircraft component assembly using distributed monocular vision. Design/methodology/approach For each of the mating holes on the components, a monocular vision module is applied to measure the poses of holes, which together shape a distributed monocular vision system. A new unconstrained hole pose optimization model is developed considering the complicated wearing on hole edges, and it is solved by a iterative reweighted particle swarm optimization (IR-PSO) method. Based on the obtained poses of holes, a Plücker line coordinates-based method is proposed for the relative posture evaluation between the components, and the analytical solution of posture parameters is derived. The required movements for coaxial alignment are finally calculated using the kinematics model of parallel mechanism. Findings The IR-PSO method derived more accurate hole pose arguments than the state-of-the-art method under complicated wearing situation of holes, and is much more efficient due to the elimination of constraints. The accuracy of the Plücker line coordinates-based relative posture evaluation (PRPE) method is competitive with the singular value decomposition (SVD) method, but it does not rely on the corresponding of point set; thus, it is more appropriate for coaxial alignment. Practical implications An automatic coaxial alignment system (ACAS) has been developed for the assembly of a large pilotless aircraft, and a coaxial error of 0.04 mm is realized. Originality/value The IR-PSO method can be applied for pose optimization of other cylindrical object, and the analytical solution of Plücker line coordinates-based axes registration is derived for the first time.

A Coordination Space Model for Assemblability Analysis and Optimization during Measurement-Assisted Large-Scale Assembly

“…In this case, d is 2.46 × 10 −14 mm 3 rad 3 . The KAC number to be compensated is 5,6,8,10,12,14,18,19, and 20. The center SDT of the coordination zone in scheme 18 is −0.0363 mm, 0.0210 mm, 0.0098 mm, 2.52 × 10 −6 rad, 1.64 × 10 −6 rad, −2.35 × 10 −6 rad .…”

“…2020, 10, 3331; doi:10.3390/app10093331 www.mdpi.com/journal/applsci which improved the accuracy of pose evaluation. Li et al [5] proposed a coaxial alignment method using distributed monocular vision. The iterative reweighted particle swarm optimization method was constructed to improve the measurement ability of complicated wearing holes.…”

A Coaxial Alignment Method for Large Flange Parts Assembly Using Multiple Local Images

“…Liu et al used a CCD camera and an LDS in the AGV system to recognize and localize the part by detecting the point and circle features of the parts, and then accomplished the assembly of large components [23]. Li et al improved Liu's method by acquiring images via coaxially distributed cameras and fitting the edges as ellipses, and then aligned the components by building and solving an optimization model via Particle Swarm Optimization (PSO) method [24]. Some other kinds of large parts, such as radar antennas and large frames were also assembled by using cameras, LDS, and inclination angle sensors [25]- [27].…”

A ball head positioning method based on hybrid force-position control

“…1 Before the docking assembly, the large component of aircraft (LCA) must be precisely adjusted to align the posture between the components. 2 The traditional assembly process adopts manual hoisting and rigid frame positioning, which requires technical workers to adjust the posture of the LCA manually. 3 The workload of posture adjustment is heavy, but the docking accuracy cannot be guaranteed.…”