What is Nanopositioning ?

1. What is Nanopositioning ?

2. Precision In Applications Source: newscaletech.com

3. Exactly what is a Nanometer? • One billionth of a meter - 1,000,000,000 • Water molecule > 1 nanometer • Typical germ ~ 1000 nanometers • Human hair ~ 100,000 nanometer • Carbon Nanotube = 1 nanometer wide

4. Nanopositioning Requirements What is the Client’s understanding oftheir Nanopositioning application? • Accuracy • Precision • Resolution • Smoothness • Constant Velocity Scanning • Repeatability

5. Nanopositioning Requirements Motion Control Applications must be: • Predictable • Verifiable • Controllable Design Considerations: • Accuracy • Stiffness • Environment

6. Design Considerations • Accuracy

7. AccuracyAccuracy 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).

8. AccuracyAccuracy vs. Precision

9. AccuracyResolution While Resolution is not Accuracy… It is part of what makes up Accuracy Two parts of Resolution • Electrical Resolution • Mechanical Resolution

10. Design Considerations • Accuracy • Stiffness

11. What Exactly is Stiffness? MOTOR SERVO STIFFNESS MECHANICAL

12. Stiffness MOTOR SERVO STIFFNESS MECHANICAL

13. StiffnessSix Degrees of Error Freedom Encoder Resolution doesn’t define the Accuracy of aCompleteMachine • Pitch • Roll • Yaw • Flatness • Straightness • Scale The combined interacting effects of all contributing factors must be analyzed before total system precision can be determined.

14. StiffnessSix Degrees of Error Freedom

15. StiffnessSix Degrees of Error Freedom

16. StiffnessSix Degrees of Error Freedom

17. StiffnessMounting / Drive location

18. StiffnessMounting / Drive location

19. Stiffness MOTOR SERVO STIFFNESS MECHANICAL

20. StiffnessServo • Servo Stiffness • Bandwidth • Servo sampling rate for current & position loops • Encoder resolution • Mechanical Stiffness

21. Stiffness MOTOR SERVO STIFFNESS MECHANICAL

22. StiffnessMotor • Motor Stiffness • Mechanical stiffness • Ability to respond to commanded motion • Flux pattern (Magnetic Servo)

23. Design Considerations • Accuracy • Stiffness • Environment

24. Environment Other Error Causing Factors • Thermal expansion errors • Abbé offsets • Feedback Position • Cosine errors • Lost motion • Orthogonality • External forces • Viberation

25. EnvironmentThermal Expansion Errors Thermal expansion coefficients of motion elements must be considered when selection high-precision platforms.

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)

27. Environment Position Feedback Control Schemes

28. Environment Position Feedback Control Schemes

29. Environment Position Feedback Control Schemes

30. Environment Position Feedback Control Schemes

31. Environment Position Feedback Control Schemes

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.

33. Environment Lost Motion (hysteresis) • Any system that reacts and recovers differently when varying directional forces are applied will exhibit lost motion. • Ballscrew backlash

34. Environment Orthogonality Orthogonality – The degree to which stages are aligned with their motion at right angles to one another.

35. Environment External forces • Side Loading • Motor resistance • System harmonics

36. Vibration – Nearby Conditions • Other machinery • Road traffic • Building sway