Automating the Precise Assembly of Large Structures with Continuous Servo Control

The industrial challenges of the HAPPY & HAPPY2 projects

Rapid market changes and the demand for customized products require more flexibility in the means of production. In aeronautics, assembly lines must be able to adapt to speeds and variants while limiting the constraints associated with heavy equipment and fixed tools.

• Provide flexibility with regard to product speeds and variants.
• reduce the intensive use of overhead cranes, which have been identified as bottlenecks in aeronautical assembly workshops;
• eliminate the use of tools anchored to the ground;
• Consider flexibility, stress, and deformation of parts and tooling during assembly.
• Accurately automate the handling and positioning of heavy parts.
• Test the technology on multiple interfaces and on more complex aeronautical and naval use cases.

In naval defence, continuous servo control is also an opportunity to standardise production methods, horizontally reference two large elements and eliminate a turning operation after pointing.

Technologies developed for automated assembly

Both projects developed and then enriched an assembly architecture based on mobile positioners, control laws and several measurement means.

• development of a control law compensating for the flexibility of parts and tooling based on continuous local measurements;
• use of cameras for the tenon / screed use case;
• use of laser profilometers for the case of orbital junction;
• adaptation of the control law to the control of the twisting of a part from a global metrology means;
• taking into account forces and deformations in order to optimize control or check the condition of the output parts;
• simultaneous servo control on multiple interfaces;
• combination of sensors, including profilometers, cameras, and eddy current sensors;
• remove markers from parts and detect smaller bores or other remarkable geometric primitives;
• comparison of 3D plane and circle detection methods with stereo and GPU system, as well as model-based 3D tracking.
• development of a visual servo with priority management to align one bore through another in the case of wing use;
• development of an algorithm for processing profilometer data to assist the operator when docking ferrules.

Project results & industrial impacts

HAPPY has validated the principle of continuous servo control on two aeronautical use cases. The demonstrator was then transferred to the Airbus Atlantic site in Montoir-de-Bretagne for an evaluation of performance in real conditions.

• development of a lightweight and modular solution, compatible with the "clean shopfloor" requirements of aeronautics;
• assembly times announced to be about ten times faster than those practiced in the aeronautics industry;
• experimental validation of the minimization of forces during twisting, before and during assembly;
• development of a marker-free visual servo solution for the post/clevis junction;
• development of a bore alignment solution for the wing use case;
• development of profilometer data processing for ferrule docking with operator assistance.

The final results of HAPPY2 are presented as promising and allow us to envisage applications on several technological bricks: simultaneous servoing on several interfaces, combination of various sensors and detection of smaller or different geometric primitives.