Best Practices for Motion Control: Stepper Motor and Encoder Selection
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Lin Engineering and US Digital present stepper motor and encoder feedback selection considerations for motion control applications. We’ll share a case book example highlighting a medical application that required a high torque step motor utilizing an encoder for position feedback. Details of stepper motor and feedback options will be presented along with common terms and a guide to selection and integration.
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Best Practices for Motion Control: Stepper Motor and Encoder Selection
- 2. • • • • • Selec%ng a step motor Common step motor enhancements Case History Benefits of an encoder Encoder selec%on
- 3. 1. Maximum Efficiency Torque at Speed 2. Power Available Voltage & Current 3. Common Issues Resonance Accuracy
- 4. • Vary the voltage or the current • Find an opera%ng speed • Motor supplier will back calculate required torque
- 5. Maximizing Torque @ OperaOng Speed 24VDC, 2.0 Amps/Phase, Full Stepping 80 Lin Motor ExisOng Motor Pullout Torque (oz-‐in) 70 60 50 OLD Opera%ng Speed NEW 40 Opera%ng Speed 30 20 10 0 200 400 600 800 1000 Speed (pps, 1 pulse = 1.8 degree) 1200 5
- 6. (Varied by motor winding and power) 80 We design motor’s max. efficiency at your opera%ng speed Efficiency (%) 70 60 50 40 30 20 10 0 0 2 4 6 8 10 12 14 16 Speed (RPS) 6
- 8. Tips to reduce resonance • Change Voltage and Current • Change Iner%a of the load • Change microstepping • Change to a different motor
- 9. Vibration Amplitude Vibration Amplitude 3709 vs. Standard 0.9
- 10. • Vary Current or Voltage to find torque • Every motor can be maximized for best performance for max efficiency • Reduce resonance by changing voltage, current, microstepping or load.
- 12. • Lower Speeds and/or Higher Torque-‐ Gearboxes • Reduce Resonance-‐ Dampers • Posi%on Verifica%on and Correc%on-‐ Encoders
- 13. • When posi:on of motor must always be maintained • If a motor stall detec:on and ac%on is required • Typical Industries: • Medical • Solar • Semiconductor
- 14. Background: • Medical device used to remove mucus from pa%ent airways Requirements: • High holding torque • Accurate posi%oning • Posi%on feedback
- 16. • Mechanical • Resolu%on • Index • Differen%al vs. Single Ended Output
- 19. • Frame Size • Shac Diameter • Moun%ng Bolt Circle • Environmental Considera%ons
- 24. One Cycle 1 2 3 Quadrature States 4
- 25. • CPR -‐ Cycles Per Revolu%on • PPR -‐ Pulses Per Revolu%on • Example -‐ 100 CPR = 400 PPR
- 26. Output A Output B A Leads B
- 27. Output A Output B B Leads A
- 28. • Provide Direc%on of Shac Rota%on Informa%on • Enable 4x Resolu%on Increase Over Disk CPR • Standard Signals Regardless of Encoder Mechanical Package
- 30. Output A Output B Index
- 31. Index Paeern
- 32. • Once per 360 Degree Rota%on • Gives a Single Absolute Loca%on • Typically Used for Home or Zero Loca%on
- 34. A A’ B B’
- 35. A A’ Index Index’
- 36. • High Electrical Noise Immunity • Transmijng Encoder Signals Over a Long Distance • Requires Differen%al Receiver
- 37. Output A Output B Index
- 38. • Simple Interface Requirements • Most Common Form of Encoder Output • Short Distance Signal Transmission
- 39. • • • • • Mechanical Resolu%on Index Differen%al vs. Single Ended Output Final Step -‐ Decision
- 44. • • • • • Short Lead Times Personal Customer Service Great Value Reliability Custom Mo%on Control Solu%ons