ECE5320 Mechatronics Assignment#01: Literature Survey on Sensors and Actuators

1. Linear Motor Introduction ECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Prepared by: William Bourgeous Dept. of Electrical and Computer Engineering Utah State University E-mail: williamk@cc.usu.edu Phone: (435) 750-0147

2. Outline • Basic working principle illustrated • Major specifications • Limitations • Linear Motor Types • Major applications • Selection and Purchasing • To probe further • Reference list

3. Working Principle A basic linear motor can be envisioned as a conventional rotary motor slit axially and rolled out flat. Courtesy of: Sinker Description

4. Working Principle The force (F = I L x B) on the moving charges in the purple bar magnet cause it to move to the right. Applying this principle we can build a linear motor. Courtesy of: sjsu

5. Working Principle Linear Motors are typically composed of: • Stationary magnets or planten (rotor); • Moving coil assembly - a specific arrangement of permanent magnets and/or electro-magnets Courtesy of: Rockwell Automation

6. Rotary vs. Linear Motors Courtesy of: Copley Motion Sytems

7. Advantages of Linear Motors #1 advantage of linear motors: Totally eliminates the need, cost and limitations of mechanical rotation-to-translation mechanisms such as racks and pinions or belts and pulleys which are sources of elasticity and backlash. The complexity of the mechanical system is drastically reduced Courtesy of: Baldor

8. Advantages of Linear Motors (Cont) • High repeatability – resolution to (0.1 microns) – this makes sure all parts produced are accurate and identical • Highly accurate – (2.5 micron/300 mm) – provides precise machine operation for precision parts • Faster acceleration – from 1 to over 10 G’s – this leads to shortened cycle times and improved productivity • Higher velocities – speeds to over 300 inches/second (8 meters/sec) – to position the payload faster Courtesy of: Baldor

9. Advantages of Linear Motors (Cont) • Long term reliability – only two parts with only one moving part – this leads to simplicity and improves the applications reliability • No wear or maintenance – no contacting parts, thus reducing component friction and wear • Ease of installation – linear motors are designed to allow for alignment tolerances. Misalignment produces no degradation of performance Courtesy of: Baldor

10. Disadvantages of Linear Motors • Costly to purchase and install • Requires Higher Bandwidth in Sensors, Controls and Drives • Force Per Package Size: Linear motors are not compact force generators compared to a rotary motor. Linear motors are not brute force devices. • Heating: The forcer is often attached to the load. If an application is sensitive to heat, thermal management techniques need to be applied. Air and water cooling options are popular and common. • “No” Friction: For example, a linear motor is traveling at high speed and loses power. Without resistance in the system, it does not take long before the motor reaches the end of the stroke and slams the mechanical stops. Courtesy of: Compumotor

11. Common Linear Motor Types • Linear motors can be classified by power supply, operation and control just as rotary motors are: • There are a wide variety of linear motors so we will classify them by mechanical construction. • Permanent Magnets • Electromagnets • Hybrid • Planten • DC • AC • Stepper • Servo

12. Common Linear Motor Types • Permanent Magnet Motors • Platen Type Linear Motors • Linear Induction Motors • U shaped Linear Brushless Motors • Tubular Courtesy of: Copley Motion Systems

13. Limitations of Common Linear Motor Types • Permanent Magnet (PM) Motors • Limited forces/speeds • Platen Type Linear Motors • Precision air gap required • Exposed track • Linear Induction Motors • Large physical size • High power consumption • Cooling typically required • U shaped Linear Brushless Motors • Restricted heat dissipation • Tubular Linear Motors • Limited travel; ends must be supported Courtesy of: Copley Motion Systems

14. Permanent Magnet Linear Motor • The same magnetic principles that apply to rotary PM motors hold true for linear PM motors (Figures A&B). Figure A – Electromagnetic Principles Figure B – PM Linear Motor Courtesy of: Rockwell Automation

15. X-Y Robotic Arm; PM Linear Application Cable Management Permanent Magnets Courtesy of: Idaho National Laboratory

16. Platen • The electromagnets are formed in the shape of teeth so that their magnetic flux can be concentrated. • Only one set of teeth is aligned with the teeth on the platen at any time. Courtesy of: Compumotor

17. Platen (cont) • When a pattern of energizing one coil and then another is established, the resulting magnetic field will pull the motor in one direction from one tooth to the next. When current flow to the coil is stopped, the forcer will align itself to the appropriate tooth set and create a holding force that tends to keep the forcer from moving left or right to another tooth. Courtesy of: Compumotor

18. Platen Motor Applications • Accurate Position Applications Courtesy of: National Instruments

19. Linear Induction Motor (LIM) • The Linear Induction Motor (LIM) is designed for high force, long-stroke applications, such as material handling and people movers. • The single sided Linear Induction Motor consists of coil assemblies and a reaction plate. • The coil assembly is comprised of steel laminations and phase windings encapsulated in epoxy. • When voltage is applied to the coil windings, a traveling magnetic field is created. This induces current in the reaction plate which in turn creates its own magnetic field. • The interaction of the two magnetic fields generates the force and direct linear motion. Courtesy of: Baldor

20. Linear Induction Motor Application 1 • Rail Based Trains • Railcar is reduced • Can travel on grades as steep as 8% vs the 3.5% limit for conventional rotary motor railcars Courtesy of: Hitachi-Rail.com

21. Linear Induction Motor Application 2 • Magnetic Levitation Trains • Travel at speeds of up to 310 mph Courtesy of: HowStuffWorks.com

22. U-Channel Linear Motor • Constructed of two parallel magnet tracks facing each other with the forcer between the plates. • The forcers are ironless, the ironless coil assembly has low mass, allowing for very high acceleration. • This design reduces magnetic flux leakage. Courtesy of: aerotech

23. Tubular Linear Motor An outer thrust block carrying the motor coils envelops and moves along a stationary thrust rod that houses magnets. • High Thrust • Low Maintenance • Simple Design Courtesy of: Control Engineering

24. Motor Selection • Selection Parameters: • Compute force calculations • Compute operating requirements • Consider thermal issues • Identify the right technology for the application i.e. (commutation methods) • Compare Bearing loading

25. Motor Sizing • Motors are rated by force. • Fa = force required to accelerate the load • Ft = force required during traverse motion • Fd = force required to decelerate the load Courtesy of: Aerotech

26. Where to Buy • Aerotech, Inc. • Baldor Electric Company • Bosch Rexroth Corporation • Copley Controls Corp. • Danaher • H2W Technologies • NSK Precision America, Inc. • Parker • Rockwell Automation • Servo Magnetics Incorporated • Siemens • Yaskawa Electric

27. To explore further • LinearMotors - • http://www.engineeringtalk.com/guides/linear-motors.html • Linear Encoders – • http://www.heidenhain.com/linear-1.html • http://www.engineeringtalk.com /guides/linear-encoders.html

28. Reference list • Manufactures Data Sheets • Rockwell Automation • Parker • Aerotech • Compumotor • Copley Automation • Precision Motion Control With Disturbance Observer for Pulsewidth-Modulated-Driven Permanent-Magnet Linear Motors, IEEE Transactions on Magnetics, vol. 39, no. 3, May 2003 • San Jose State University

29. The End Questions? Prepared by: William Bourgeous Dept. of Electrical and Computer Engineering Utah State University E-mail: williamk@cc.usu.edu Phone: (435) 750-0147