Schedule of Events

Week
1 2 3

Date
7 Mar 14 Mar 21 Mar

Content
Introduction Design Process System Modelling and Control

Assignment Notes

Mtrx 1701: Introduction to Mechatronics

Actuators

4
5 6

28 Mar
4 Apr 11 Apr

Actuators
Sensors Computer Hardware Assignment 1 Due

BREAK
7 8 9 10 11 12 13 14 25 Apr 2 May 9 May 16 May 23 May 30 May 6 June Public Holiday: ANZAC Day Active Sensing Systems Computer Software Digital vs. Power Electronics Case Study I Case Study II Guest Lecture Spare Major Assignment Due Assignment 2 Due

Mtrx 1701: Introduction to Mechatronics

Slide 1

Mtrx 1701: Introduction to Mechatronics

Slide 2

What is an actuator?
A mechanical device for moving or controlling something Electric Motors and Drives Hydraulic Drives Pneumatic Drives Internal Combustion hybrids Actuators of the future

Electric Actuators and Drives

Electrical energy transformed to mechanical energy

DC Motors
AC Motors Linear Motors Stepper Motors
Slide 3 Mtrx 1701: Introduction to Mechatronics Slide 4

Mtrx 1701: Introduction to Mechatronics

DC-Motors
Rotary actuators Power range: Fractions of watts to 100s of Kw. Power supply by grid, diesel generator, or batteries Easy to control accurately
Mtrx 1701: Introduction to Mechatronics Slide 5

Basic Operating Principle

Mtrx 1701: Introduction to Mechatronics

Slide 6

Basic Operating Principle

DC-Motors
Apply a voltage to armature Armature rotates in magnetic field Speed control by:

=K.V

Armature voltage Field Strength

Speed proportional to Voltage Torque proportional to current Power=Speed x Torque

Mtrx 1701: Introduction to Mechatronics Slide 7 Mtrx 1701: Introduction to Mechatronics Slide 8

DC Motors: Basic Rules I

Torque proportional to current

DC Motors: Basic Rules II

Ra R a ia Va Vb Voltage Balance in Armature

T = KT ia
Torque Constant Current flowing in Armature

Ra ia + Vb = Va Ra ia + K b = Va

Voltage generated by motion of armature in field (like a Generator)

Mtrx 1701: Introduction to Mechatronics Slide 9

Back EMF Constant

Slide 10

Mtrx 1701: Introduction to Mechatronics

DC Motors: Basic Rules III

Torque and Speed

DC Motors Behaviour I
Equations of Motion: Torque Drives a Load

T = KT ia

No-load Speed

Ra ia + K b = Va

T T
Stall Torque
Slide 11

B
J

T=

KT Va K b KT Ra Ra
+

T=J

Ra 1 T+ Va K b KT Kb

d + B dt

K K d +B+ b T dt Ra

KT Va = Ra
Slide 12

Mtrx 1701: Introduction to Mechatronics

Mtrx 1701: Introduction to Mechatronics

DC Motors: Behaviour II
J d K K K + B + b T = T Va dt Ra Ra
1 0.9 0.8 0.7 0.6 Output

DC Servo Motors
Power range: few W to few kW: for disc drives, X-Y recorders, instruments, robot arms Speed: very low to very high 10000 rpm (use gear boxes) Time-constants (ms): Electrical, Mechanical and thermal Friction: Coulomb, viscous, stiction Often in-built encoders or tachometers
Mtrx 1701: Introduction to Mechatronics Slide 14

d (t ) + K1(t ) = K 2V (t ) dt
(t ) = K 2 e K1tV (t )

0.5 0.4 0.3 0.2 0.1 0

0.5

1.5

2.5 Time (s)

3.5

4.5

Step response of motor speed with varying load

Mtrx 1701: Introduction to Mechatronics

Slide 13

Permanent Magnet DC Motors

Many DC Servos are now brushless PM-DC motors because of advances in:
1. High energy ceramic and rare earth magnets 2. Development of high power switching semiconductors

Digital Control of DC Motors

Pulse-Width-Modulated (PWM)
Output Voltage Sample Period Output is average over sample period

No field windings Result is motors which are smaller and linear Motor is inside-out (magnets rotate).
Mtrx 1701: Introduction to Mechatronics Slide 15

Pulse-Rate-Modulated (PRM)
Output Voltage Constant pulse length Output is average Over all periods
Slide 16

Mtrx 1701: Introduction to Mechatronics

When to use a DC Motor

Some Examples
Consumer Products:
CDs, disk drives Fans, drills, etc

Accurate position or velocity control Low noise, high efficiency Cost not too critical Speed and power payoff (gearing)

Manufacturing
Robots CNC machines

Aerospace
Sensor pointing Fly-by-wire inputs

Cars:
Windscreen wipers Fuel management
Mtrx 1701: Introduction to Mechatronics Slide 17 Mtrx 1701: Introduction to Mechatronics Slide 18

AC-MOTORS: An Introduction
1

AC-MOTORS: An Introduction

~V

Single or three phase motors 100 Watts MW High power high torque applications Brushless, durable, easy to maintain Now fully digital vector controlled
Slide 19 Mtrx 1701: Introduction to Mechatronics Slide 20

Mtrx 1701: Introduction to Mechatronics

AC-MOTORS: Main Features

Brush free full digital control Requires sophisticated algorithms to control speed (hence recent) Frequency control via power converter (field control) Suitable for high speed and/or high power applications Complex structure, heavy weight
Mtrx 1701: Introduction to Mechatronics

Multi-phase AC servo motors

Drive voltages out of phase Multi-phase induction Better control and power density Transfer function is second order
r
vc = k s ( m s + 1)
Mtrx 1701: Introduction to Mechatronics Slide 22

vm = Vmcost ~

vc = kVm sint

Slide 21

When to Use an AC Motor

High power required Complex control profiles:
Point to point Velocity

Applications of AC Drives
Large Cranes or material handling systems Belts or conveyors High Speed Trains Electric Drive Haul Trucks (930E)

Load Demand
High duty cycle Efficiency Reliable
Mtrx 1701: Introduction to Mechatronics Slide 23

Mtrx 1701: Introduction to Mechatronics

Slide 24

Stepper Motors
Motors that cause angular shift correspondence to a number of pulses
1st method: providing a fixed number of pulses, motion proportional to number of pulses 2nd method: synchronising rotations with the input pulse frequency
Mtrx 1701: Introduction to Mechatronics Slide 25

Stepper Motors
PM type: permanent magnets rotor VR (variable reluctance) type: salient poles rotor, torque is generated from difference of magnetic resistance Applications: Electronic typewriters and printers, magnetic disk drives

Mtrx 1701: Introduction to Mechatronics

Slide 26

Voice Coil
Voice coil is an actuator based on similar principles to a motor current appplied to coil induces magnetic field Uses closed loop feedback servoing to dynamically position heads in a computer hard drive Name voice coil comes from resemblance to technology used to drive audio speaker
Mtrx 1701: Introduction to Mechatronics Slide 27

Computer Hard Drive

Hard drive uses 3 phase AC motor to turn disk Originally used stepper motors to position read head Modern hard drives use voice coil to position read head

Mtrx 1701: Introduction to Mechatronics

Slide 28

Linear Motors: Brief Introduction

Slider (rotor), stationary part (stator), and gap are extended in a straight line Linear DC motors, stepping motors, induction motors, etc. Relatively expensive and large for power output
Mtrx 1701: Introduction to Mechatronics

Linear Motors: Brief Introduction

Miniature & simple structure, low power factor & efficiency Linear DC motors: rare earth PMs, two yokes, moving coil Linear induction motors: eddy current is developed in a good electrical conductor to obtain thrust

F = iB
Slide 29

Mtrx 1701: Introduction to Mechatronics

Slide 30

Summary of Electric Motors

Servo Motor
DC servo motor:

Hydraulic Systems and Actuators

Hydraulics: Use of fluids to transmit power:
Pumps are power generators Inverse pumps or cylinders are power drain Valves used for control Pump or Rotary motor Linear Actuator (Cylinder)

Advantages
Easy to use, Low priced control device No brush maintenance

Disadvantages
Brush replacement. Has restrictions in respect of operating environment Control device is expensive due to its complexity Detector is necessary

Applicable capacity
0.1 - few 100 Watts

Brushless motor (PM synchronous) Synchronous motor (vector control) Induction motor (vector control) Stepping motor

from few W to few kW

Excellent environment resistivity Durable construction Open loop control, large static torque

Complicated control system Dropped out of step. Large weight/capacity ratio

More than few W Below few 10 W

Traditionally High Power applications Now use integrated electronics and sensing
Slide 31 Mtrx 1701: Introduction to Mechatronics Slide 32

Mtrx 1701: Introduction to Mechatronics

Hydraulic Circuits
Hydraulic Power Units: Pumps Accumulators (fluid capacitors) Check valves to isolate hydraulic systems Reservoirs Piping and Fittings Proportional/servo valves Hydraulic actuators
Mtrx 1701: Introduction to Mechatronics Slide 33

Rotary Hydraulic Pumps and Motors

General Operating principles:
Fluid is compressed by pump on which mechanical work is done Fluid does work in motor producing mechanical power

Two Types:
Vane/gear pumps Piston/swash-plate
Mtrx 1701: Introduction to Mechatronics Slide 34

Hydraulic Motor

Piston and Swash-plate Pumps/Motors

Pistons connected to swash plate Swash plate is angled
Swash plate rotates and pumps fluid Fluid flow rotates swash plate

Mtrx 1701: Introduction to Mechatronics

Slide 35

Mtrx 1701: Introduction to Mechatronics

Slide 36

Hydraulic Cylinder Actuators

Piston in cylinder acted on by hydraulic pressure Force generated by rod: Single acting Double acting Double cylinder Double rod Efficiency governed by friction, Small internal leakage: hold static load

Hydraulic Valves
Three main valve types:
On/off valves for manual control Proportional valves: Control of volume flow rate Servo valves: Accurate control of flow and pressure

Pressure Force

Fc = PA c Area
Friction
Slide 37

Control Mode: Electric over hydraulic Hydraulic over hydraulic (pilot) Manual
Mtrx 1701: Introduction to Mechatronics Slide 38

Mtrx 1701: Introduction to Mechatronics

Digital Flow Control

Integrated Valve

Electro-hydraulic System Example

Integrated Manifold Fully Digital Controller

Mtrx 1701: Introduction to Mechatronics Slide 39 Mtrx 1701: Introduction to Mechatronics Slide 40

10

When to use Hydraulics

Large Force, High Power applications High power density Accurate control Rugged environments (explosive, dusty,etc) Now use integrated electronics and sensing Wide range of applications:
www.moog.com www.rexroth-hydraulics.com
Mtrx 1701: Introduction to Mechatronics Slide 41

Applications of Hydraulic Systems

Heavy Plant
Steel press Large-scale precision motion tables

Mobile Systems
Steering, brakes Propulsion and transmission

Aerospace
Aerolon actuation in aircraft Fin actuation in missiles/rockets
Mtrx 1701: Introduction to Mechatronics Slide 42

Pneumatic Systems
Many of the same principles as hydraulics except working fluid is compressed air Compressed air widely available and environmentally friendly, Piping installation and maintenance is easy Explosion proof construction Major disadvantage is compressibility of air, leading to low power densities and poor control properties (usually on/off) Pneumatic systems are suitable for light and medium loads (30N-20kN) with temperature -40 to 200 degrees Celsius
Mtrx 1701: Introduction to Mechatronics Slide 43

Pneumatic Actuators

Oscillating actuator (Rack and pinion type)

Air motors (multi-stroke radial piston type)

Slide 44

Mtrx 1701: Introduction to Mechatronics

11

Modern Pneumatic Systems

Dual check valves Linear drive

When to use Pneumatics

Low cost and easy to install Clean and easy to maintain Low power densities Only on/off or inaccurate control necessary

Servovalve offers closed loop control of acceleration, velocity, positioning and force

Angular Toggle Gripper

Twin cylinder piston vacuum pump or compressor 250 W motor developing 2.8 bar with flow to 8.7 m3/hr

Mtrx 1701: Introduction to Mechatronics

Slide 45

Mtrx 1701: Introduction to Mechatronics

Slide 46

Pneumatic Applications
Manufacturing
Robot grippers Movement of parts Assembly operations

Internal Combustion Engine

Fuel energy transformed to mechanical energy

Medical Systems
Drills/cutting tools Suction and clamping

Robotics
Animatronics Grippers Subsea
Mtrx 1701: Introduction to Mechatronics Slide 47

Petrol Engine Diesel Hybrid

Mtrx 1701: Introduction to Mechatronics

Slide 48

12

Internal Combustion Engine

Hybrid Electric Drives - Parallel

Both gas engine and electric motor connected to drivetrain Improved fuel economy and reduced emissions Regenerative braking supplements battery charging

Mtrx 1701: Introduction to Mechatronics

Slide 49

Mtrx 1701: Introduction to Mechatronics

Slide 50

Hybrid Electric Drives - Series

Charge batteries with combustion engine and generator Combustion engine efficiency increased by operating at a single optimised speed Energy density of fuels higher than current battery technologies
Mtrx 1701: Introduction to Mechatronics Slide 51

Future Actuators...
Actuators using functional materials Piezoelectric element actuator Ultrasonic Motors Actuators of shape memory alloys Plasma motors Bio-actuators ..and many more !
Mtrx 1701: Introduction to Mechatronics Slide 52

13

Piezo Micro Actuators

Shape Memory Alloys (SMA)

SMA=TiNi alloy Height 160mm Weight 0.06kg Changes shape on (electric) heating

http://www.piezo.com/bendedu.html
Mtrx 1701: Introduction to Mechatronics Slide 53 Mtrx 1701: Introduction to Mechatronics Slide 54

And finally.MEMs

Summary
There are many types of actuators available today Selecting the right actuators is a critical part of the design cycle Requires an understanding of
Type of motion Precision of motion Magnitude of motion Operating conditions

Mtrx 1701: Introduction to Mechatronics

Slide 55

Mtrx 1701: Introduction to Mechatronics

Slide 56

14

Questions?

Mtrx 1701: Introduction to Mechatronics

Slide 57

15