38_Hydraulics and Pneumatics

Actuators are used in order to produce mechanical movement in robots. --Not only electrical actuators --Pneumatic Actuators --Hydraulic Actuators --Comparison of various Actuators

1. Robot Actuators

2.Actuators for Robots Actuators are used in order to produce mechanical movement in robots. Slides from Braunl and Jussi Suomela Jussi Suomela HUT/Automation 2

3. Not only electrical actuators • Pneumatic • Hydraulic • chemical

4.Hydraulic and Pneumatic Motors Pneumatic Power - Air-powered cylinders • Compressed air • Either stored on board or injected by a pump • Produces linear motion through activation of cylinders Hydraulic Power - Fluid (non-air)-powered cylinders • Uncompressible fluid, most often oil. • Requires a pump to generate the pressure and flow rate needed. • Complex and difficult to build effectively, and costly.

5.Hydraulic and Pneumatic Motors Double Acting Cylinders Piston rod Retracted Air Inlet Mechanical Stops Double Acting Cylinder Air Inlet Extended Stroke Extension limit

6. Pneumatic Actuators Jussi Suomela HUT/Automation 6

7.Pneumatic Devices  It is very similar to hydraulic system, but power-to-weight ratio is much lower than hydraulic system.  Because the air is compressible, it compressed and deforms under load.

8.Pneumatic Actuators like hydraulic except power from compressed air fast on/off type tasks big forces with elasticity no leak problems Jussi Suomela HUT/Automation 8

9.Double Action Cylinder

10. Compressed air Single Action Cylinder Compressed air Double Action Cylinder

11. Hydraulic Actuators Jussi Suomela HUT/Automation 11

12. When we use liquid as the fluid, we call it a hydraulics system

13. Hydraulic Actuators Components and Properties o linear movement o big forces without gears o actuators are simple o in mobile machines o Bad efficiency o motor, pump, actuator combination is lighter than motor, generator, battery, motor & gear combinationHUT/Automation Jussi Suomela 13

14. Hydraulic Valves  servo valves  complicated structure, expensive  good control  proportional valves  simple, cheap  robust  more difficult to control  Digital hydraulics, new!  several fast on/off valves (2n)  digital control of the flow Jussi Suomela HUT/Automation 14

15. Hydraulic actuators: cylinders Cylinder types: Double acting piston: Single acting: work can be done only in one direction Work is done in both Plunge directions r Piston rod on both sides Piston Tandem Telescop Fast Telescop Fast moving ic ic moving 2005/2006 I. Hydraulic and Pneumatic Systems 15

16. Servo Valve Jussi Suomela HUT/Automation 16

17.Advantages of Hydraulic Actuators  Hydraulic Actuator offers: • a high power-to-weight ratio , • large forces at low speeds • compatibility with microprocessor • tolerance of extreme hazardous environments. torque dA t dr r2 r2 T  p r dA  p r t dr r1 r1 r2 1  pt  r dr  pt (r22  r12 ) r1 2 where,  A is the effective area of the piston,  p is the working pressure.

18.Comparing Electrical and Fluid Actuators

19.A simple hydraulic system can be made out of syringes and aquarium tubing

20.A simple ROV with a hydraulic actuator

21. Click the two links below to see some simple but effective hydraulic systems in action: http://www.youtube.com/watch? v=VFje0G69ku8&feature=related http://www.youtube.com/watch? feature=endscreen&v=vsF95qA1x7I&NR=1

22. For ideas on building a linear actuator with a motor and some PVC, check out this link: http://blog.davidjbarnes.com/2009/03/m aking-linear-actuator-for-robots.html

23. Applications of Hydraulic Motors


25.Hydraulic actuators


27.Actuators are Everywhere - Examples

28.Other Actuators  piezoelectric  magnetic  ultra sound  SMA  inertial Jussi Suomela HUT/Automation 28

29. Comparison of various Actuators Jussi Suomela HUT/Automation 29