38_Hydraulics and Pneumatics

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 

24 .Arska 

25 .Hydraulic actuators 

26 .Workpartner 

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