1. DESIGN OF AUTOMATION SYSTEMS
ERT 457
DESIGN OF AUTOMATION SYSTEMS
Munira Mohamed Nazari
PPK Bioproses
UniMAP
Powerpoint Templates

2. Lecture 3: Actuators and Drivers

3. Course Outcome
CO 2
Ability to design (C5) automation system for agricultural and biological production system.

4. Course Outline Introduction Pneumatic & Hydraulic Actuation Systems
Electrical Actuation Systems
Mechanical Actuation Systems

5. introduction

6. Why we automated systems in agricultural area?
To fulfill requirement of modern farming.
Reduce labor work and cost.
Reduce time.
Help you to improve your agricultural application to be even more productive and comfortable to use.

7. Actuators in agriculture
Actuator solutions in spreaders adjusting the amount of fertilizers.
Sprayer, actuator control height and angle of outlet nozzle.
In chopper, actuator used to adjust the outlet direction.
Electric actuators – used to improve ergonomics and comfort in a number of applications such as adjustment of steering wheels, seats and ventilation.

8. Sensor vs Actuator A sensor An actuator
monitors the variable such as pressure and temperature and send a signal to a transmitter or indicator.
An actuator
Hardware devices that convert a controller command signal into a change in a physical parameter.
The change is usually mechanical (eg: position or velocity).
An actuator is a transducer because it changes one type of physical quantity into some alternative form.
An actuator is usually activated by a low-level command signal, so an amplifier may be required to provide sufficient power to drive the actuator.

9. Actuation Systems
Practically every industrial process requires objects to be moved, manipulated, held, or subjected to some type of force.
The most commonly employed methods for producing the required forces/motions are:
Air – Pneumatics
Liquids – Hydraulics
Electrical – motors, solenoids.
Mechanical

10. A Brief System Comparison
The task considered is how to lift a body by a distance x mm. such tasks are common in manufacturing industries.

12. Electric Actuators - motor

13. Drives & Control Engineering for Actutors
Energy (Medium)
Control
Drive
Actuator Type
Electrical
- Electrical current
Contactor and relay control
Digital and analog control
Wired program
Freely programmable system
Power contactor
DC motor
AC motor
Stepper motor
Solenoid
Pneumatics
- Compressed air from compressor
Digital control
Conventional valve technology
Pneumatic logic
Directional valve
Flow control valve
Motors
Cylinders
Tools-gripper
Hydraulics
- Hydraulic fluids using pump
Mechanical driven
Manual driven
Special valve

14. Pneumatic & hydraulic actuation systems

15. Actuate large valve & high-power control device
PNEUMATIC
SIGNALS
Compressibility of air
More high-power control device - expensive
HYDRAULIC
SYSTEMS
Oil leaks – causes hazard

16. Pneumatic Vs Hydraulic
Application
Hydraulics are used for power and precision.
Pneumatics are used for light weight and speedy applications.
Material used in the construction of the components.
Hydraulic components are mainly made from steel.
Pneumatic components are made from plastic and mom-ferrous materials.
However, the materials used in the system may have to withstand some of the following conditions:
Heat
Cold
Mechanical damage
Dust
Chemical attack

17. Pneumatic Vs Hydraulic
When either pneumatic or hydraulic systems are equally for an application the following should be considered.
Hydraulics generally calls for a greater capital outlay.
Hydraulic power generally cheaper on an energy basis.
Installation of hydraulic equipment generally requires a power pack for each machine.
Hydraulics with multiple machines generally requires a power pack for each machine.
Pneumatic machinery can be plugged into a ring main.

18. Pneumatic Vs Hydraulic
Comparison Table
HYDRAULIC
PNEUMATIC
ENERGY SOURCE
Electric motor
Int. combustion engine
ENERGY STORAGE
Accumulator
Air receiver
DISTRIBUTION SYSTEM
Very localized
Ring main
FLEXIBILITY
Not easy to expand
Easy to modify and change
CAPITAL COST
High
Lower
ENERGY COST
Medium
Higher
ROTARY ACTUATOR
Low speed
Good control
High speed
Control - difficult
LINEAR ACTUATOR
High force
Medium force

19. Pneumatic Vs Hydraulic
Comparison Table (con’t…)
HYDRAULIC
PNEUMATIC
CONTROLLABLE FORCE
High degree of control and precision with high forces.
Control difficult with high forces.
MAINTENANCE
Expansive
Fluid replacement/top up
Cheaper
No fluid replacement
SAFETY
Oil may leak
Fire hazard
Chemical/environmental
Explosive failure
Noisy

20. Hydraulics Definition
Is the science of transmitting force and/or motion through the medium of a confined liquid.
Power is transmitted by pushing on a confined liquid.

21. Hydraulic Systems Hydraulic systems schematic diagram.
Smooth out any short term fluctuations – output oil pressure
Release pressure – rise about safe level.
Prevent the oil being back to the pump

22. Hydraulic Systems Hydraulic pumps.
Gear pump – two close meshing gear rotated.
Vane pump – spring loaded sliding vanes.
Piston pump
Radial piston pump - cylinder block is rotate.
Axial piston pump – move axially.

23. Hydraulic Systems Gear pump Advantages Weaknesses Widely used Low cost
Robust
Weaknesses
Leakage
Limit efficiency
Gear wheels rotate in opposite direction.
Fluid forces through pump, become trapped between gear teeth.
Fluid transferred fro the inlet port to be discharged at the outlet port.

24. Hydraulic Systems Vane pump Advantage
Spring loaded sliding vanes slotted in a driven motor.
Rotor rotates – vanes follow contours of the casing.
Fluid trapped between successive vanes and casing.
Transported round from inlet to outlet.
Advantage
Leakage less than gear pump.

25. Hydraulic Systems Radial piston pump Axial piston pump
Cylinder block rotates – hollow pistons with spring return, to move in and out.
Fluid drawn from inlet port.
Fluid transported round for ejection from the discharge port.
Piston move axially in a rotating cylinder block – move by contact with the swash plate.
Shaft rotates – move the pistons.
Air sucks (piston opposite the inlet), air expelled (opposite the discharge port.

26. Hydraulic Systems Piston pump advantages. High efficiency
Can be used at higher hydraulic pressures than gear (below 15 MPa) or vane pumps.

27. Pneumatic Systems Pneumatic systems schematic diagram
Drive a compressor
Increase volume of air
To reduce noise level
To reduce temperature
Provide protection against pressure in the system.
Remove contamination and water

28. Pneumatic Systems Types of an air compressors.
Are ones in which successive volumes of air are isolated and then compressed.
Single acting, single stage, vertical, reciprocating compressor.
Rotary vane compressor.
Screw compressor.

29. Pneumatic Systems
Single acting, single stage, vertical, reciprocating compressor
The descending piston causes air to be sucked into the chamber.
Piston rise again – trapped air forces the inlet valve to close – become compressed.
Air pressure risen sufficiently – spring loaded outlet valve open – trapped air flows into the compressed air system.
After the piston has reached the top dead centre it then begins to descend and the cycle repeat itself.
Piston
Spring loaded inlet valve

30. Pneumatic Systems Rotary vane compressor.
Has a rotor mounted eccentrically in a cylindrical chamber.
Rotation causing the vanes to be driven outwards against the walls of the cylinder.
Air is trapped in pockets formed by the vanes – rotor rotates – pockets become smaller and the air is compressed.
Compressed packets of air thus discharged from the discharge port.

31. Pneumatic Systems Screw compressor.
Screw rotate – air drawn into the space between the screws.
Air trapped – move along the length of the screws and compressed (space progressively smaller), emerging from the discharge port.

32. Valves
Are used with hydraulics and pneumatics systems to direct and regulate the fluid flow.
Two types:
Finite position
To allow or block fluid flow and so can be used to switch actuators on or off.
Can be used for directional control to switch the flow from one path to another and so from one actuator to another.
Infinite position
Able to control flow anywhere between fully on and fully off,
Are used to control varying actuator forces or the rate of fluid flow for a process control situation.

33. Directional Control Valves
To direct the flow of fluid through a system.
Not intended to vary the rate of fluid flow but are either completely open or completely closed.
Example: on/off devices.
widely used to develop sequenced control systems.
Might be activated to switch the fluid flow direction by means of mechanical, electric or fluid pressure signals.
Common types:
Spool valve
Poppet valve

34. Directional Control Valves
Spool valve.

35. Directional Control Valves
Poppet valve.

36. Directional Control Valves
Valve symbols
Consists of a square for each of its switching positions. (eg: poppet valve – two position valve – two squares)
Port labels:
1 or P = pressure supply
3 or T = hydraulic return
3 (R) or 5 (S) = pneumatic exhaust
2 (B) or 5 (A) = output
Flow path
Flow path – indicate the direction of flow in each of the position.
Blocked off lines indicating closed flow lines
Initial connections – valve have 4 ports
Initial connections ( 4ports)
Flow shut-off

37. Directional Control Valves
Valve actuation symbols.

38. Directional Control Valves
Symbol for two port, two position poppet valve.
Can be describe as a 2/2 valve.
Number of positions
Number of ports
Output port
Spring
Push button
Pressure supply port

39. Directional Control Valves
Single-solenoid valve.
How many port and position??
Answer: 3/2

40. Directional Control Valves
Symbol for a 4/2 valve.
Output port
Output port
Solenoid
Spring
Pressure supply port
Pneumatic
exhaust

41. Directional Control Valves
Lift system.
A simple example of an application of valves in a pneumatic lift system.

42. Directional Control Valves
Pilot-operated Valve
To overcome a problem of too large force required to move the ball or shuttle in a valve for manual or solenoid operation. One valve (pilot valve) is used to control a second valve (main valve).
Pilot pressure
line
Pilot valve – used to allow the main valve to be operated by the system pressure.
Pilot + main valves can be operated by two separate valves but they are often combined in a single housing.
Small capacity & can be operated manually or by a solenoid.

43. Directional Control Valves
Directional Valves
Free flow can only occur in one direction through the valve.
The ball being pressed against the spring. Flow in other direction is blocked by the spring forcing the ball against its seat.

44. Pressure Control Valves
3 main types.
Pressure-regulating valves
To control the operating pressure in a circuit and maintain it at a constant value.
Pressure-limiting valves
As safety device.
The valve opens and vents to the atmosphere, or back to the sump if the pressure rises above the set safe value.

45. Pressure Control Valves
Pressure sequence valves.
used to sense the pressure of an external line and give a signal when it reaches some preset value.
The valve switching on when the inlet pressure reaches a particular value and allowing the pressure to be applied to the system that follow.

46. Cylinders
Pneumatic and hydraulic cylinder is an example of linear actuator.
Same principles, differences in term of size as hydraulic required high pressure.
Consists of a cylindrical tube along which a piston/ram cam slide.
2 basic types:
single acting cylinder and
double acting cylinder.

47. Cylinders Single acting cylinder.
Used when the control pressure is applied to just one side of the piston, a spring often being used to provide the opposition to the movement of the piston. The other side is open to the atmosphere.

48. Cylinders
Control of a single-acting cylinder with (a) no current through solenoid, (b) a current through the solenoid.
As a consequence, the spring returns the piston back along the cylinder.
When a current passes through the solenoid, the valve switches position and pressure is applied to move the piston along the cylinder.
When the current ceases, the valve reverts to its initial position and the air is vented from the cylinder.

49. Cylinders Double acting cylinder.
Used when the control pressure are applied to each side of the piston. A differences in pressure between the 2 sides, results in motion of the piston. The piston being able to move in either direction along the cylinder as a result of high-pressure signals.

50. Cylinders
Control of a double-acting cylinder with solenoid, (a) not activated, (b) activated.
Current through one solenoid causes the piston to move in one direction with current through the other solenoid reversing the direction of motion.

51. Force produced by cylinder
Cylinders
The choice of cylinder, determined by force required to move the load and speed required.
Hydraulic – capable larger force
Pneumatic – capable greater speed
F = Aρ
Working pressure
Force produced by cylinder
FORCE
Cross-sectional area of cylinder
Can’t use for pneumatic !!
-since its speed depends on the rate at which air can be vented ahead of the advancing piston.
HYDRAULIC
FLUID FLOW
Q = Av
Speed

52. Cylinders Cylinder Sequencing
Used as a sequential control of extensions and retractions of the cylinder.
Cylinder – reference letter A, B, C, D,…
State of cylinder – ‘+’ sign = extended, ‘-’ sign = retracted.
So sequence of operation = A+, A-, B+, B-

54. Cylinders Cylinder Sequencing
Valve 1 is pressed – applied pressure to valve 2 – activated limit switch b- - valve 3 is switched to apply pressure to cylinder A for extension.
Cylinder A extends – releasing limit switch a- - cylinder A fully extended – limit switch a+ operates – switches valve 5 – pressure applied to valve 6 – apply pressure to cylinder B – piston extend.
Cylinder B extends – releasing limit switch b- - cylinder B fully extended – limit switch b+ operates – switches valve 4 – pressure applied to valve 3 – applies pressure to cylinder A – piston retracting.
Cylinder A retract – releasing limit switch a+ - cylinder A fully retracted – limit switch a- operates – switches valve 7 – pressure applied to valve 5 – applies pressure to cylinder B – piston retracting.
Cylinder B retracts – releasing limit switch b+ - cylinder B fully retracted – limit switch b- operates to complete the cycle.

55. Servo and Proportional Control Valve
Are both infinite position valves which give a valve spool displacement proportional to the current supplied to a solenoid.
Servo :
have a torque motor to move the spool within a valve.
High precision
Costly
Used in a closed-loop control system.

56. Servo and Proportional Control Valve
Less expensive
Have the spool position directly controlled by the size of current to the valve solenoid.
Used in open-loop control systems.

57. Process Control Valve Used to control the rate of fluid flow.
Common form of pneumatic actuator used with process control valves is the diaphragm actuator.
Consists of a diaphragm with the input pressure signal from the controller on one side and atmospheric pressure on the other. Differences in pressure being termed the gauge pressure.
The diaphragm is made of rubber which is sandwiched in its centre between two circular steel discs.

58. Process Control Valve
Effect of changes in the input pressure.

59. Process Control Valve F = kx kx = PA P = F / A
If the shaft moves through a distance x, and compression of spring is proportional to the force,
and, displacement of the shaft is proportional to the gauge pressure.
So, pressure P,
F = kx
kx = PA
Diaphragm area
P = F / A

60. Process Control Valve Q = Av √ (∆P / ρ) Control Valve Sizing
Procedure of determining correct size of valve body.
Q = Av √ (∆P / ρ)
Flow rate
Density of the fluid
Flow rate
Valve flow coefficient
Pressure drop across the valve
Flow coefficient
Valve size (mm)
480
640
800
960
1260
1600
1920
2560 Cv 8 14 22 30 50 75
110
200
Av x 10 19 33 52 71
119
178
261
474 -5
Table 7.1

61. Process Control Valve A = F / P = 500 / (100 x 10³) = 0.005 m²
Example:
Consider the problem of diaphragm actuator to be used to open a control valve if a force of 500 N must be applied to the valve. What diaphragm are is required for a control gauge pressure of 100 kPA.
A = F / P
= 500 / (100 x 10³)
= m²

62. Process Control Valve Example: Q = Av √ (∆P / ρ) Av = Q√ (ρ /∆P)
Consider the problem of determining the valve size for a valve that is required to control the flow of water when the maximum flow required is m³/s and the permissible pressure drop across the valve at this flow rate is 300 kPa. Density of water is 1000 kg/m³
Q = Av √ (∆P / ρ)
Av = Q√ (ρ /∆P)
= 0.012√ (1000 / 300 x 10³)
= 69.3 x 10 m²
So, the valve size is 960 mm. -5

63. Problem 7.9
A hydraulic cylinder is to be used to move a workpiece in a manufacturing operation through a distance of 50mm in 10 s. A force of 10 kN is required to move the workpiece. Determine the required working pressure and hydraulic liquid flow rate if a cylinder with a piston diameter of 100mm is available.
P = 1.27 Mpa & Q = 3.93 x m³/s -5

64. Problem 7.12
What is the process control valve size for a valve that is required to control the flow of water when the maximum flow required is m³/s and the permissible pressure drop across the valve at this flow rate is 100 kPa? The density of water is 1000 kg/m³.
The process control valve size = 480 mm

65. Thank you..