AStandard actuator

1. Control algorithm(Open-loop or closed-loop

Paradigm shift

AStandard actuator

1. Control algorithm (Open-loop or closed loop)2. Condition monitoring3. Fault detection and isolation

1. Microelectronics2. Digital system3. Distributed control4. Open standards

A standard actuator in its basic form only possesses the control algorithm. However, an advanced or smart actuator is much more than this. It integrates auxiliary features such as condition monitoring, fault detection and isolation scheme, digital technology, microelectronic and nevertheless the open system standards

Voltage/Curtent measurement device

Temprature sensor

Hall device Encoder

CurrentVoltage/

Speedtemprature magnic field

(Data Fusion) Fault analysis based on comparision of characteristicand physical parameters usinf measurements

Knowledge base

Perception

Validation modes (Fault types)

Torquemeter

Torque

(Characteristic and Physical parameters)

Performance can be improved by monitoring the condition of the actuators on-line. Condition monitoring attempts to identify faults. Motors can be monitored by the use of physical parameters, such as voltage, current, speed, magnetic flux, armature resistance/inductance, magnetic flux, viscous friction, dry friction etc.

Pneumatic actuators have been used for servo applications even as axes of numeric control machine systems. The motion sequence of a Numerically-Controlled (NC) axis in a packaging system in which bottles are to be inserted into a container consists of various positions to which the NC axis moves. Figure illustrates a typical application in a packaging system.

CYLINDER

I/O card inside

Feedback Devices

Valve

Control Algorithm

control signal

feedback signal

piston

pressure sensors

encoder

inlet supply pressure

switches

LOAD

Principal elements of a typical pneumatic actuator system

The actuator is interfaced with three major elements; controller, feedback sensors and a valve.

PositionController

Speed Controller

PowerController MOTOR

+

- -+ +

- Torque

Position

Speed

Current

Figure shows the basic feedback system configuration of a servo motor control system. It is seen that the basic concepts of motor control systems falls under three categories, namely; torque control, speed control and position control. The position and speed information are usually obtained from the encoder. The current information is obtained from the current sensors.

Joints (Actuator)

Controller

B A S E

End effector

Arm

Interface

Controller

End effector

Infrared sensor

Wheels

Vehicle Body

CAMERA

An industrial robot is a re-programmable, multifunctional manipulator designed to move materials, parts, tools or special devices through variable programmed motions for performing a variety of tasks. There are various types of robots in the practical field of application. One of the classifications is based on whether they are fixed or mobile.

Source of Information

Source of Energy

Robot

Workspace

Source of Information

Source of Energy

Robot

Workspace

CPUOperational

Unit

Computer Controller

Control Element

Process

Measurement Devices(sensors)

The central processing unit is concerned with data processing. The operational unit is the physical robot itself. It takes action on the workspace by using, transforming and/or acquiring energy from the suitable source(s) and reacting to the signals and commands are provided by the sensory systems and central processing unit.

communication system

human visual system

human input

human input (joystic)

Communication system ( operator)

OPERATOR

ENVIRONMENT

Adaptive

Filter

perception

KBperception

KB

perception

KB

perception

KB

perception

KB

perception

KBperception

KB

perception

KB

TV

Laser scaner

Ultrasonic sensor

Battery monitoring

another sensor

Guidance wireantenna safety sensor Pulse encoder

Action

consequence

Navigation rough path

Behaviour base

Pre-defined routing planing

Obstacleavoiding

Position holdder

Wheel control

Movementcommands

Strategic levelHuman Intellect

Servo drive Level

Tactical Level

Mobile robots sometimes called Autonomous Guided Vehicle (AGVs) are currently used for transporting material in industry, warehouses and underground mining and are also

developed for exploration of the oceans and space, etc. AGV architectural view in the control context is shown in this slide

N3

N8 N9 N10

N2

indicating lamps

N5N4

Battery charger

N7

N1

Servo

PCM

Servo

PCM

N6

Servo

PCM

Protection relays etc.(Emergency stop,laser scanner,safety edge strip,fixture, anti-jamprotection etc.

antenna

PC

Panel

Digital signalAnalog signal

N1 = Node for driving hight and rotational movement of fixture; N2 = Indicating lamp node; N3 = Antenna nodeN4 = Battery charger node; N5 = PC node; N6 = Vehicle control node; N7 = Digital signal node; N8 = Analog signal node; N9 = Membrane pannel node, N10 = Safety equipment monitoring node

The control system in the AGV is essentially distributed according to the physical location of the devices and control software. That is the complete vehicle is based on a distributed control design concept. The figure illustrates the schematic diagram of components in a DCS conformant AGV control architecture.

START

Reset the system(Bring to initial position)

run the motor

is PCB at the workbench ?

yes

no

1. bring x-axis and y-axis rollers to the middle of the workbench2. drill the PCB as per specification

job done ? yes

no

drill the PCB as per specification

A three-axis platform for drilling the PCB board was chosen for giving an example of another mechatronic system. The platform has three axes; x, y and z. Z-axis holds the needle to drill holes on the PCB board. The PCB boards are passed to the workbench through a conveyor system driven by an AC motor. When the PCB board reaches at the

right position called station the gripper rigidly holds the board so that the z-axis of the platform will be able to do its job properly i.e., doing drilling operation without any shaking.

x-controllerN1

y-controllerN2

interfacing circuits

interfacing circuits

z-controllerN3

interfacing circuits

encoder encoderencoder

motor-controllerN4

interfacing circuits

gripper-controller

N3

interfacing circuits

switch proximity sensor

CONTROL NETWORK

LCA Object ServerNetBuild componentNetInstall componentNetMonitor componenytWindowsNTVisualBasic

Host Computer

Network cardfrom Echeloninside

The control system for three-axis platform has a generic set of essential requirements in terms of co-ordination, synchronization, acknowledgement, timing etc. A DCS network with five nodes has been designed for the operation of the drilling machine.

*Stop the Motor*Detect Colour of the Object*Send the colour code to the robot*Run the Motor

Job Done ?

Start

* Power suply to the motor, colour sensor, robot and interfacing circuts* Initialise node* Initialise robot

Run the Motor

Is CV value of the temp. sensor > 75 % ?

YesNo

Is Switch1 True ?

Stop the Motor

Yes

No

Pick the Object and place it at the appropriateplace according to the colour code

Yes

The material handling is the movement, protection, storage of materials and products throughout the process of their manufacture, assembly and distribution. The above figure illustrates the control flow chart of a typical conveyor based material handling system.

Windows98

LCA Object Server (LNS)

NetBuild, NetInstall, NetMonitor

Visual Basic

PC with PCI Network

card (inside)

LonWorks Network

Motor

interfacing

circuits

switches

N1

interfacing

circuits

colour sensor

PRODUCTION LINE CONVEYOR SYSTEM

objects

interfacing

circuits

temperature

sensor

N3

(control loop)

IF temp >= T

and CV >= cv%

stop motor

N2

pick and place robot

Robot Controller

Packing

Box

smart

switch

Supply Side

PRODUCTION CELL

DELIVER Y

Interfacing

control components such as, a single phase AC motor, a temperature sensor, two microswitches an a colour sensor. The demonstration application involves the loading of product from the conveyor into defined containers.

Figure shows the schematic diagram of this conveyor-based material handling system and control. It includes conveyor belt, Pick-and-Place robotic workstation,

Run the motor

Has the product in the colour inspection zone ?

Yes

No

Stop the conveyor

Start inspection

Inspection finished ?

Yes

Assign a colour code

1. Sensor fusion technique2. Use of CV LEVEL3. Indentification and Isolation of sensor validation modes4. Audio Alarm

Validated Inspection

A device is considered intelligent if it has the capability of producing some sort of validation pointer. An illustration of validated inspection.

Light

Filters

phototransisters

Colour Sensor

Latch

Latch

Latch

phototransisters

phototransisters

Filters

calibration

Validated colour

Fusion technique-based colour sensor validation

When identical devices at least triplex in configurations are verified by comparing the measured value at a given instant and the failure/validation modes are isolated by majority voting it is then referred to as fusion technique.

No

YesAVM-2

AVM-1

If switch-2 is true start motor validation algorithm

Is motorrunning ?

No

No

No

Yes

Yes

Yes

Calculate speed

Compare the speed with the nominal speed

AVM-3 AVM-4

AVM-6

AVM-5

speed< nominal speed speed> nominal speed

Is temp.>= Th.?

speed= nominal speed

No fault

Is supplyvoltage OK ?

Shut down motor

Test current

Is current flowing ?

A typical but simple validation implementation with regard to electric motor type actuator, used for driving conveyor based material handling system.

Ne

two

rk

ProductLight

Filters Detectors

Colour Sensor

A/D Converter

Gizmo-3 Board

Channel-1Channel-2Channel-3

NEURON

CHIP

I/O

PORT

Communication

Port

Processors

Some interfacing circuits for color sensor used in the Conveyor-based material handing system.

1

2

3

4 5

6

7

8LF 351 N

(+V)

Out

non-inverting

inverting

- 5 V

+ 5 V

1 K

10 K

1 M

OUTPUT

Phototransister PT 510

Some interfacing circuits for color sensor used in the

Conveyor-based material handing system.

Parallel Port

Game Port

Network

Pick and Place Robot

Robot Controller (PC)

TURBO PASCAL 7

Interface Board

Neuron Chip I/O Port

Processors

Communication Port

Container

Conveyor

Product holders

Some interfacing circuits for RTX robot. The interfacing between the RTX controller (PC) and LON system was achieved through USB (A game port is a port that is incorporated into a computer conventionally using a 15-pin D-style connector) of the PC

Network

Manual Start/Stop

Auto Forward-Manual Reverse

RelaysMotor

Gear system and Shaft connected to Belt

PowerSupply Board

10 rev./min.

NEURON

CHIP

I/O

PORT

Communication

Port

Processors

NEURON

CHIP

I/O

PORT

Communication

Port

Processors

Temperature sensor

Encoder

Decoder

Sensor fusion

Supply detection Circuit armature

currentdetection circuir

Interface circuit for motor node is illustrated in the figure. The motor can be started and emergency stopped manually by pressing the manual buttons. The motion can also be reversed when required.

- 0 V

Neutral

- 240 VEarth

+ 24 DC

GND

Run

Dir

Manual/Auto

Run (Manual)

Run (Auto)

Direction (manual)

Manual

Auto

Run

EARTH

The circuit diagram of the Relay Box can be seen in this figure. The relays are equipped with diodes in order to prevent high-voltage spikes in the Relay Box terminals, which cloud destroy the LON nodes connected to it.