1. Robot Actuators

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

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
Air Inlet
Piston rod
Double Acting Cylinder
Retracted
Mechanical Stops
Air Inlet
Extended
Extension limit
Stroke

6. Pneumatic Actuators
Jussi Suomela
HUT/Automation

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

9. Double Action Cylinder

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

11. Hydraulic Actuators
Jussi Suomela
HUT/Automation

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

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

14. Hydraulic Valves servo valves proportional 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

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

16. Servo Valve
Jussi Suomela
HUT/Automation

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
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:

22. For ideas on building a linear actuator with a motor and some PVC, check out this link:

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

29. Comparison of various Actuators
Jussi Suomela
HUT/Automation

30. Advantages and Disadvantages of Hydraulic Actuators

31. Advantages and Disadvantages of Pneumatic Actuators

32. (DC motor and stepper motor)
Advantages and Disadvantages of Electric Actuators
(DC motor and stepper motor)

33. Motors Properties: Comparison

34. Practically In this class we will use only servos
In past we used DC motors with H-bridge, pneumatic actuators, nintinol wires and hydraulic actuators.
So far, if you want to build rather small robots and you want to concentrate on intelligence and sensing, RC servos are the best choice. Many new types arrive every year, from very small to big powerful ones. Look to internet.
We will learn about some new actuators if time will allow at the end of the class.

35. What did we learn? Feedback control is a fundament of robot control
Various kits (Lego Dacta Control Lab) have several demonstrations and project to explain the principles of feedback:
Line following
Speed control
Temperature control (fan, lamp, sensor)

36. What did we learn? Control of Many DOF robots is tough
In addition to classical and modern control theory we use:
fuzzy control
genetic algorithms
neural control
bio-mimetic systems
Review your control knowledge (for next quarter), but remember that in this class all knowledge is through programming

37. Your task
Learn about the particular servo that you plan to use. If the servo was not suggested by the professor, learn about servos that are available, calculate your project requirements for a servo and pick one. Ask Bryce to order for you. The more servos we order, the cheaper the price of one.
If you do not want to use one of standard servos, your choices are:
build your own servo from a DC motor. This is a big project by itself and you must have clear reasons to do so
Use AC motor. Only for big robots. The same as above.
Use stepper motor. Remember that they are slow and weak, why you want to use them? You must be sure of your reasons

38. Your task
Use hydraulic control. Why? You need to purchase or build your own actuator. Think about redesigning our horse leg with better syringes and oil instead of water. How can you connect the syringe to a stepper motor?
Use pneumatic control. Read first the documentation of pneumatic hand or old Electric Horse. Talk to designers.
Find pistons in Mondo-Tronics or other robot store. They are good.
Use Nintinol or other similar actutors. They are good for face muscles or similar small and weak movements.
Can they be used for a hexapod? I doubt, but try to convince me
Before you do this, read the two-volume book of Conrad and Mills

39. Sources
Braunl
Jussi Suomela
Jussi Suomela
HUT/Automation