Advanced Collaborative Multifunctional End-Effector (ACME)

Motivation

• The drilling operation is one of the most dominant manufacturing processes in aircraft assembly.

• Ex. Around one million holes are drilled for rivets and fasteners in an A220.

• Still, a considerable portion of drilling is done manually, which has its downsides.

Automated Drilling

• Higher productivity

• A smaller number of operators

• Capable of providing accurate, repeatable results

Manual Drilling

• Time and labour-intensive

• Musculoskeletal problems

• Requires a large number of jigs

• Not flexible to engineering changes

Challenges in Automated Drilling

• Safety

• Large capital and time investments for adoption

  • Over $2 million for each unit of Kuka + ALEMA drilling unit

• Disruption to the factory floor layouts

• Obtaining tight aerospace manufacturing tolerances

System Design

Specifications:

• 5 DoF drilling tool for cobots

• Provides clamping force up to 100 kg by attaching the surface using suction cups

• Double curvature surfaces (up to 2m in radius) with normality compensation

• Onboard sensors

  • Camera for localization

  • Loadcell for clamping force control

  • Encoders for accurate positioning

Clamping Force:

• Clamping force is achieved by moving the frame towards the surface and contacting the drilling nose with it.

• The Pressure builds up and is monitored (force control) using a hole-through load cell at the nose.

Normalization Mechanism:

• Self-normalization based on reaction forces on the nose (Any clamping force above 560 N will normalize the nose to the surface automatically)

• Active joints (A&B) with servo motors + absolute encoders can also be utilized.

Clamping Mechanism

CoreXY Mechanism illustration

XY Positioning:

• The CoreXY mechanism reduces the number of moving parts (minimum inertia) for accurate and fast positioning.

• The XYZ is controlled using absolute magnetic encoders for accurate positioning.

Mechatronic Components

• All the mechatronic components serve to achieve the sequence of drilling.

Layout of the electronics components and control box

Layout of pneumatic circuit

Drilling Sequence

• The layout of the electronics and control box helps with proper assembly, installation, and maintenance

• Pneumatic system provides suction for attachment and powers the drilling unit. It is controlled by the main controller (Raspberry Pi GPIO) with relay modules for digital ON/OFF control of suction and drilling units, employing serial communication protocols and feedback loops for precise operational timing and enhanced reliability.

ACME in Operation