Prepared by: VIJAY C. JACOB vijay.jacob@aggiemailu

1. ECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Topic: Servo Pneumatic Actuator Prepared by: VIJAY C. JACOB vijay.jacob@aggiemail.usu.edu 03/06/2009

2. Outline • Brief/Origin • Advantages and Disadvantages • Elements of a Servo Pneumatic system • Pneumatic Compressors • How it works? • Major specifications • How to choose? • Limitations • Overcoming problems with Pneumatics • Computer control • Reference List ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

3. Brief/Origins • The term ‘pneumatic’ originates from the Greek word ‘pneumos’, namely to breathe. • Conventional pneumatic actuation is a long established means of providing power in industrial processes. • Avariant on the conventional cylinder actuator wasdeveloped to provide a positioning capability based the input of a pressure signal. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

4. Advantages • Systems are simple and easily maintained. • The components are relatively low in cost. • Widely sourced. • Control is easily achieved in conventional forms. • Generally safe in operation. • Self cooling properties. • Clean in nature. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

5. Advantages (Contd.) • Good power density. • Compliant due to the compressibility of air. • Actuators can stall over prolonged periods with no adverse effects. • Relatively temperature insensitive. • Fast acting with high accelerations / deceleration’s. • Servo technology can be coupled with low cost computing to exploit the capabilities of advanced control techniques to overcome severe control issues normally associated with regular pneumatic actuation. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

6. Disadvantages • Compressed air is anexpensive and inefficient power source due to the compression process and distribution losses. • Losses through leakage are likely. • Can be potentially dangerous when operated at elevated pressures. • Water vapor can accrue. • Compressibility is inherent. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

7. Elements of a pneumatic servo actuator system: ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

8. The components of a pneumatic actuation system are: • The compressed air generation system, consisting of the compressor, the cooler, possibly a dryer. • The storage tank, the intake and output filters. • The compressed air treatment unit, usually consisting of the FRL assembly (filter, pressure regulator, and possibly a lubrifier), which permits filtration and local regulation of the supply pressure to the actuator valve. • The valve, that is, the regulator of the pneumatic power. • The actuator, which converts the pneumatic power into mechanical power. • The piping. • Sensors and transducers. • User Interface. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

9. Pneumatic Compressors • Single Action. • Double Action. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

10. Single Action • Pneumatic porting only in one direction • Usually have a return spring to return the system to the stable position ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

11. Double Action • The two sides of the piston are pressurized • This enables two-way motion • The forces can be different in opposing directions if desired ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

12. How It Works?! • Pressure can be placed on one side of a piston which causes it to extend • It can be detracted using an opposing force or a spring when the original force is removed ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

13. Major Operating Specifications • Cylinder stroke – “distance between fully extended and fully retracted rod positions” • Operating pressure range – “specifies the full-required range of operating pressure” • Globalspec.com ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

14. Other Specifications • Bore size • Mounting options • Connectors or port size • Body material • Features ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

15. Limitations • Length of rod stroke is limited • Wide range of pressures • Operating temperature ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

16. How to Choose? • Cylinder style • Bore size and length • Material / robustness • Cost • Pressure ratings • Application ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

17. Overcoming control problems associated with pneumatics: • Pneumatic servo actuators operating at the relatively low pressures pertinent to industrial usage are characterized by highly non-linear system behavior due to factors such as the compressibility of air, low inherent damping, time lags, dead zone, position dependent stiffness, time-dependent frictional effects in the actuator and non-linear control components with discontinuities, which leads to undesirable operational characteristics such asinstability, inconsistent transient response, large static positioning errors and limit cycling. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

18. The stability of pneumatic actuators can be improved with the use of either pressure feedback or ‘minor loop’ compensation in the form of velocity and acceleration feedback. • The transient response can be enhanced with ‘gain scheduling’ techniques implemented in the form of look-up tables. • The static positioning error can be minimized by increasing the proportional gain . • Response time lags can be minimized with the application of ‘front-end’ control strategies which modify the demand to the actuator. • The characteristics of the control components, in-particular the valve, have a significant influence on the pneumatic actuator. • Methods have been devised to minimize non-linearity’s, discontinuities and dead zone in the control valve through the use of ‘null control’ algorithms. • The transient response of pneumatic actuators can be further enhanced with the profile planning techniques. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

19. Computer control of pneumatic actuators: • Simplified set up and configuration of the actuator. • Low cost ,powerful processing platforms. • Easier to implement digital control strategies. • Intelligence and communications can be embedded within the actuator design. • Intelligent software gives rise to “Intelligent Actuators”. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

20. Some commercially available actuator systems: • Some of the currently available commercial servo pneumatic technology includes; servo actuator systems produced by: Festo, Origa and Bosch. • Each of these systems is available with a range of cylinder actuators in both conventional and rod-less configurations which are capable of point-to-point motion. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

21. Application Areas: • Agriculture. • Materials handling. • Packaging machinery. • Machine tools. • Robotics. • Food processing and process industry. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

22. Sample Images ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

23. Future • There remains considerable scope for further development of components, tools and techniques for optimizing theperformance of low pressure pneumatic servo-mechanisms. • The development of tools for modeling and simulation in the design of pneumatic servo systems is a definite requirement. • Growing interest in the possibility of pneumatic drives based on closed circuit systems which could overcome, at least in-part, the high running cost associated with this drive medium. • The development of new valve technology. • There also remains considerable scope for the fundamental development of new actuator types based on a pneumatic power source (e.g. pneumatic muscles, etc.). ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

24. Reference List • Andersen, B. W., The analysis and design of pneumatic systems, Wiley, New York, 1967.Globalspec.com • Mechatronics Handbook • ‘‘Pneumatic Servo Actuator Technology” by Professor Philip Moore and Dr JunSheng. • wikipedia.com ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators