Prepared by: Daniel Ricsi Dept. of Electrical and Computer Engineering Utah State University

1. ECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Topic: Hydraulic Actuators Prepared by: Daniel Ricsi Dept. of Electrical and Computer Engineering Utah State University E: daniel.ric@aggiemail.usu.edu 2/26/2009

2. Outline • Reference list • To explore further • Linear actuators • Basic working principal • Hydraulic actuator • Special hydraulic cylinder • Cylinder types • Cushioning of cylinder • Parts of hydraulic cylinder • Calculations • Major applications • Major specifications • Limitations • Interesting applications ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

3. Reference list • http://home.wxs.nl/~brink494/frm_e.htm • http://science.howstuffworks.com/hydraulic1.htm • http://www.engineersedge.com/hydraulic/hydraulic_actuator.htm • http://en.wikipedia.org/wiki/Hydraulic_system ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

4. To Explore Further • http://science.howstuffworks.com/hydraulic.htm • http://en.wikipedia.org/wiki/Hydraulic_system • http://home.wxs.nl/~brink494/frm_e.htm • http://www.hydraulicsupermarket.com/technical.html ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

5. Linear Actuator • Devices that develops force and motion from an available energy source, in a linear manner. • Below is a list of different types of linear actuators: • Mechanical Actuators. • Hydraulic Actuators. • Piezoelectric Actuators. • Electro-mechanical Actuators. • Linear motors. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

6. Basic working principle • Hydraulic systems operate according to Pascal's Principle - Pressure is transmitted undiminished in an enclosed static fluid. • The figure on the right side illustrates how force multiplication can be achieved by the applying pressure according to Pascal's principle, which for the two pistons implies P1 = P2 • Therefore, with the automatic hydraulic lift, heavy load can be lifted with a small force. Of course, assuming in an ideal case with no frictional loss, work cannot be multiplied: Winput = Woutput http://hyperphysics.phy-astr.gsu.edu/Hbase/fluids/imgflu/hpress.gif ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

7. Hydraulic Actuators • Also known as hydraulic cylinders. • Typically made of a hollow cylinder with a piston inserted in it. The two sides of the piston are alternately pressurized and de-pressurized hydraulic fluid (oil) achieving precise displacement of the piston. • Hydraulic actuators are usually used when large amount of force is required otherwise pneumatic actuators are preferred. • The most common design of hydraulic actuator is the Piston type. • The pushing or pulling force of a hydraulic cylinder is: ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

8. Special hydraulic cylinders • Telescopic cylinder • telescopic cylinders can be two, three, four, five and even six stroke. In general telescopic cylinders are much more expensive that normal cylinders. Most telescopic cylinders are single acting (push). Double acting telescopic cylinders must be specially designed and manufactured. • Plunger cylinder • A hydraulic cylinder without a piston or with a piston without seals is called a plunger cylinder. A plunger cylinder can only be used as a pushing cylinder; the maximum force is piston rod area multiplied by pressure. This means that a piston cylinder in general has a relatively thick piston rod. • Differential cylinder • A differential cylinder acts like a normal cylinder when pulling. If the cylinder however has to push, the oil from the piston rod side of the cylinder is not returned to the reservoir, but goes to the bottom side of the cylinder. In such a way, the cylinder goes much faster, but the maximum force the cylinder can give is like a plunger cylinder. A differential cylinder can be manufactured like a normal cylinder, and only a special control is added. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

9. Cylinder types: Single acting: work can be done only in one direction Double acting piston: Work is done in both directions Plunger Piston rod on both sides Piston Tandem Telescopic Telescopic Fast moving Fast moving ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

10. Cushioning of cylinders: A hard impact of the piston at the end surfaces has to be inhibited – kinetic energy has to be absorbed. This is done by increasing the hydraulic resistance at the end of the stroke. • Piston • Cushion nose • Cylinder cap • Stroke volume • Cushion orifice • Throttle • Cushion adjustment screw • Mother • Non-return valve • Gas valve ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

11. Parts of Hydraulic Cylinder • Cylinder barrel. • Cylinder bottom or cap. • Cylinder Head. • Piston. • Piston rod. • Rod gland. • Seals and cushions ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

12. A2 A1 vB p2 p1 v0 Q Calculation of cylinders maximum load friction forces inertial forces slow motion, can be often neglected Outward: Backward: ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

13. Ff 1 2 3 ηc outwards inwards v Δp Calculation of cylinders • Stick-slip • Transition • Normal behaviour Hydraulic cylinders should be possibly operated in the 3rd region for smooth operation. If the cylinder is new, the leakage losses are negligibly small so that: ηc = ηmech at higher pressures ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

14. Procedure for determining the safe piston rod calculation: The two most relevant formulae used in determining the column strength of piston rod are: Euler’s formula: Johnson’s parabolic formula: • Pc = Critical or Buckling load, Kgf • η = Coefficient of end condition • E = Young’s modulus of the material • of piston rod, Kgf/mm² • a = Area of C/S of piston rod, mm² • L = Column length, mm • r = Least radius of gyration of • piston rod, mm • σy = Yield stress of the material of piston • rod, Kgf/mm² • I = Moment of inertia of piston rod • section, mm4 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

15. Cylinder wall thickness calculation C1= The tolerance on wall thickness S = Factor of safety (1.5 to 4 can be used) k = Yield strength (minimum) 36 kg/mm² for SE52 d = Inside diameter of tube, mm p = Pressure, kg/cm² ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

16. Major applications • Aerospace and Military • Manufacturing and Industry • Construction Hydraulics • Oil & Gas Hydraulics • Agricultural Hydraulics • Mining Hydraulics • Marine Hydraulics • Rescue http://www.ctgltd.co.uk/rte_img55.jpg http://www.ultra-msi.com/images/mobile_main_photo.jpg ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

17. Major Specifications • In general, hydraulic actuators are commonly specified by: • Linear/rotary • Fluid type • Piston rod diameter • Bore diameter • Maximum Operating Pressure • Operating Temperature • Force bandwidth • Mounting style • Stroke ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

18. Limitations • Unsuitable for high speed applications • Difficult to reduce in size • Unsuitable for specific position control that requires high precision • Cylinder stroke length has certain limits • Fluid type requirements, cannot use pressurized fluids • Fluid leaking may result in significant performance drop down ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

19. Interesting Applications • Diesel powered, hydrostatic drive motorcycle: http://www.hydraulicinnovations.com/index.htm • NASA World record lifting/weighing project: http://www.buffalohydraulic.com/projects.html?pjid=1 • Hydraulic Hybrids vehicles: http://www.nextenergy.org/industryservices/Hybrid__Hydraulics.asp ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators