7. Accuracy
Accuracy vs. Precision
• Accuracy doesn’t mean Precision
• Accuracy represents the ability to get
closest to a defined point.
• Precision is the ability to execute a
move and return to the same point
(regardless of accuracy).
Sold & Serviced By:
ELECTROMATE
Toll Free Phone (877) SERVO98
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www.electromate.com
sales@electromate.com
9. Accuracy
Resolution
While Resolution is not Accuracy…
It is part of what makes up
Accuracy
Two parts of Resolution
1. Electrical Resolution
2. Mechanical Resolution
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ELECTROMATE
Toll Free Phone (877) SERVO98
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www.electromate.com
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11. What Exactly is Stiffness?
M
O
OT
RV
OR
SE
STIFFNESS
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ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
MECHANICAL www.electromate.com
sales@electromate.com
12. Stiffness
M
O
OT
RV
OR
SE
STIFFNESS
Sold & Serviced By:
ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
MECHANICAL www.electromate.com
sales@electromate.com
13. Stiffness
Six Degrees of Error Freedom
Encoder Resolution doesn’t define the
Accuracy of a Complete Machine
1. Pitch
2. Roll
3. Yaw
4. Flatness
5. Straightness
6. Scale
The combined interacting effects of all contributing
factors must be analyzed before total system
precision can be determined.
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ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
www.electromate.com
sales@electromate.com
14. Stiffness
Six Degrees of Error Freedom
Sold & Serviced By:
ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
www.electromate.com
sales@electromate.com
15. Stiffness
Six Degrees of Error Freedom
Sold & Serviced By:
ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
www.electromate.com
sales@electromate.com
16. Stiffness
Six Degrees of Error Freedom
Sold & Serviced By:
ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
www.electromate.com
sales@electromate.com
19. Stiffness
M
O
OT
RV
OR
SE
STIFFNESS
Sold & Serviced By:
ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
MECHANICAL www.electromate.com
sales@electromate.com
20. Stiffness
Servo
• Servo Stiffness
– Bandwidth
• Servo sampling rate for current & position loops
– Encoder resolution
– Mechanical Stiffness
Sold & Serviced By:
ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
www.electromate.com
sales@electromate.com
21. Stiffness
M
O
OT
RV
OR
SE
STIFFNESS
Sold & Serviced By:
ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
MECHANICAL www.electromate.com
sales@electromate.com
22. Stiffness
Motor
• Motor Stiffness
– Mechanical stiffness
– Ability to respond to commanded motion
– Flux pattern (Magnetic Servo)
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ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
www.electromate.com
sales@electromate.com
25. Environment
Thermal Expansion Errors
Thermal expansion coefficients of motion
elements must be considered when
selection high-precision platforms.
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ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
www.electromate.com
sales@electromate.com
26. Environment
Abbé Offsets
Abbé errors result from a positioning measuring
device (typically a linear encoder) being offset
from the point of work (end-effector)
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ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
www.electromate.com
sales@electromate.com
27. Environment
Position Feedback Control Schemes
Sold & Serviced By:
ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
www.electromate.com
sales@electromate.com
28. Environment
Position Feedback Control Schemes
Sold & Serviced By:
ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
www.electromate.com
sales@electromate.com
29. Environment
Position Feedback Control Schemes
Sold & Serviced By:
ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
www.electromate.com
sales@electromate.com
30. Environment
Position Feedback Control Schemes
Sold & Serviced By:
ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
www.electromate.com
sales@electromate.com
31. Environment
Position Feedback Control Schemes
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ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
www.electromate.com
sales@electromate.com
32. Environment
Cosine Errors
Cosine errors occur when a positioning
feedback scale is not in perfect parallel
alignment with the motion of the
moving carriage.
Sold & Serviced By:
ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
www.electromate.com
sales@electromate.com
33. Environment
Lost Motion (hysteresis)
• Any system that reacts and recovers
differently when varying directional
forces are applied will exhibit lost
motion.
– Ballscrew backlash
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ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
www.electromate.com
sales@electromate.com
34. Environment
Orthogonality
Orthogonality – The degree to which
stages are aligned with their motion at
right angles to one another.
Sold & Serviced By:
ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
www.electromate.com
sales@electromate.com
35. Environment
External forces
• Side Loading
• Motor resistance
• System harmonics Sold & Serviced By:
ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
www.electromate.com
sales@electromate.com