Achieving EI Accuracy

Standard robot: positional uncertainty

Robots have motors connected by linkages to their corresponding axes. Rotary encoders on the motor tell the controller where the end effector is in space. This creates positional uncertainty due to:

• Mechanical wind-up and backlash of drive systems
• Deflections from payload and link masses
• Rail alignment and deflection of linear 7th axis

EI Accurate Robot: positional certainty

EI's Accurate Robot employs scales on each axis to obtain the actual axis position at the axis, rather than just at the motor encoder. This is how we achieve uniquely high accuracy, along with the benefits detailed below:

Improved rigidity

• Resist deflection from process forces
• Reduce cycle time with higher speeds and acceleration

Negligible backlash, superior repeatability

• Wear in transmission can be ignored
• Extended calibration validity
• Return to locations from any direction for further processing without needing to resynchronize

Automated health check

• Dual encoders enables cross-checking
• Immediate and automatic detection of positioning issues

Enhanced kinematic model accounts for:

• Link positions and lengths
• Payload and link weight deflection (bearing deflections and link bending)
• Feedback scaling
• Axis harmonics, runout
• Base mounting skew
• Tool point location

Additional anti-skid algorithm

• Compensates for robot deflections caused by clamping (pushing) force while drilling

External Linear 7th Axis Enhancement

• Dual drive system with zero backlash, high acceleration, and stiffness
• External encoders to support high rigidity and superior repeatability
• High rigidity equates to extended calibration validity
• Horizontal and vertical axis capability

Automated Calibration Process

• Robot Calibration software provides automated means of collecting data, generating calibration files, and verifying robot accuracy
• Interfaces with robot controller and Spatial Analyzer to move robot through a series of poses for laser tracker data collection
• Data is used to generate and verify calibration files

White Papers:

• High Accuracy Articulated Robots with CNC Control Systems
  9/17/2013 | 2013-01-2292 | SAE
• High-Accuracy Articulated Mobile Robots
  9/19/2017 | 2017-01-2095 | SAE, AeroTech
• High-Accuracy Robotic Drilling/Milling of 737 Inboard Flaps
  10/18/2011 | 2011-01-2733 | SAE, AeroTech
• Improved Accuracy of Unguided Articulated Robots
  11/10/2009 | 2009-01-3108 | SAE, AeroTech

Patent:

• Robotic Manufacturing System with Accurate Control
  3/24/2015 | US 8,989,898 B2