6.Computing Mecatrónica

8/9/2019 6.Computing Mecatrónica

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1540 Introduction To Mechatronics: Slide 1Stefan Williams

Introduction to MechatronicsMech-1540

Computers


Schedule of Events

MID SEMESTER BREAK

Spare19/614

Due 13/6Major Assignment12/613

Case Study : Unmanned Air/Land/Sea Vehicles5/612

Case Study : Formula SAE29/511

Active Sensor Systems (Graham Brooker)22/510

Due 16/5Assignment 2 - Control and Modelling15/59

Q 3 of Assign 2System Modellingand Control8/58

Q 2 of Assign 2Computer – Software and Design Tools1/57

6

5

4

3

2

1

Week

17/4

10/4

3/4

27/3

20/3

13/3

Date

Computer – Hardware

Assignment 1 –Design Exercise

Sensors

Actuators

Design Process

Introduction

Content

Q 1 of Assign 2

Due 11/4

Q 3 of Assign 1

Q 2 of Assign 1

Q 1 of Assign. 1

Assignment Notes


Computing: Summary

1. Embedded Computing Systems

2. Embedded Systems Processors3. Input and Output

4. Communications

5. Real-time algorithms


Mechatronics and Computers

Embedded computing Characteristics:

• Real-time systems• Safety and Integrity

• Real-World Interfaces

• Sensors/Actuators

• Algorithms for “intelligence” and control


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Typical System Structure

Control

Computer [µ p]

D/A

A/D

Digital

Sensor

Analog

Sensor Actuator

Off/On

Sensor

Off/On

Actuator

Analog

Digital

Parallel


Typical Processors

• Programmable Logic Controller (PLC)• Micro-controllers (µp)

• General purpose processors (PC)

• Digital Signal Processors (DSP)

• Field Programmable Gate Array (FPGA)


Programmable Logic

Controllers

• Workhorse of the automation industry

• Uses Relay Logic:

If A and B then output XIf X and not Y then signal 23

• Inputs/Outputs are physical relays

• High degree of isolation and ruggedness


PLC Structure

• A PLC consists of:

– A CPU

– Memory areas,

– Appropriate circuits to receive input/output data.


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PLC Components

• INPUT RELAYS physically exist and receive signals fromswitches, sensors

• INTERNAL UTILITY RELAYS simulated relays dedicatedto performing only one task

• COUNTERS simulated pulse counters possibly hardwarehigh-speed counters

• TIMERS come in many varieties and increments.

• OUTPUT RELAYS physically exist, are connected to theoutside

• DATA STORAGE-registers assigned to store data.Usually temporary, also used to store data when power isremoved


PLCs

• A PLC can be considered as a box full of

hundreds or thousands of separate relays,counters, timers and data storage locations.

• Counters, timers, etc. do not all physicallyexist instead they are simulated in softwarethrough bit locations in registers.

•http://www.plcs.net/contents.shtml

•http://www.wodonga.tafe.edu.au/eemo/EA160/over.htm


PLC Example

• Manufacturers: Omron, Allan Bradley, GEC

Input Unit

Output Unit

CPU(s)

Power Supply(s)

Remote Coms.


PLC Components

Block and Remote

I/O units

PLC Network


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When to use a PLC

Applications that:

• Are repetitive sequences of events

• Require high reliability in execution

• Placed in a rugged environment

• Do not require flexiblity

• Do not require complex algorithms

• Focus on event sequences


µ processors

• Used extensively inconsumer products

• Low cost, highflexibility,

• As much integrated onchip as possible

• Low-level programmingis typical

http://www.microchip.com/ PIC Processor


Example Intel-ARM

Processor

Low-power

Real Time Clock On-Chip Memory

External BIT

Serial/USB Comms 1540 Introduction To Mechatronics: Slide 16Stefan Williams

ARM Processing Core

– Intel SA-1 core

– 16-Kbyte instructionand 8-Kbyte datacache,

– memory-management units,

– read and writebuffers


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ARM System ControlModule

28 GP I/O ports,

real-time clock,

watchdog,

interval timers,

power management

interrupt controller,

reset controller,

two on-chip oscillators.1540 Introduction To Mechatronics: Slide 18Stefan Williams

ARM Peripheral ControlModule

DMA controller,LCD controller,UART Serial ,IrDA serial port,USB end point,codec interface


When to Use aµP

• Wide Application inconsumer products

• Particularly mobile

phones and high-endapps.

• Low cost, reliable

• Programming istypically in C


General Purpose Processors

• Single high-speed processor

• General arithmetic (floating point)

• Cache data pipeline etc.

• Example include

• 80486, Pentium and derivatives

• M68030, Power PC, and derivatives

• RISC processors


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Example: PC104

• 486/586 processor

• Standard form factor • Standard pin connectors

• Large I/O is typical

• On-board battery-backed ram etc.

• Many peripheral boards

• http://www.pc104.com


PC-104 Advantages

• Conventional PC hardware:• Code that runs on the desk-top will run on

embedded system (RT-OS may be necessary)

• Uses commodity chip sets and is thus cheap

and benefits from the latest technology

• Can be made in robust packaged form.


CPU Elements

• ALU

– often microprogrammed

→ CISC – hardwired, with

instruction cache

→ RISC

• program counter (PC)

– stores address of next

instruction

• registers

– instruction register

– general registers – address and data

registers (buffers)

• control unit

– controls on-chip and

external memory


CPU Block Diagram


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Peripheral IC Examples

(on-board)

• UART - Universal AsynchronousReceiver/Transmitter (UART, USART, etc)

• SIO - (Synchronous) Serial I/O

• PIO - Parallel I/O (PPI, etc)

• CTC - Counter/Timer (PIT, etc)

• A/D - Analogue to Digital Converter

• D/A - Digital to Analogue Converter


PC104 Stacks

• CPU Board

• Power Supply

• I/O drivers

• Control relays

• DSP Slave

• Etc

• Many add-ons

are available


When to use a PC104

• Large, complex calculations or system

sophistication

• Large, sensor and/or interface requirements

• Possibly requiring a conventional-type userinterface

• Robustness is not main aim of system (canbe made reliable)

• Quick to develop new applications


Digital Signal Processor (DSP)

• Very high speedrepetitive computation

• Speech, image or radar

processing• Uses vector processingand instruction pipe-line

• Usually used as co-processors

• Often used in arrays


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SHARC Internals:


SHARC Statistics:

• Static Superscalar architecture optimizedfor Telecom Infrastructure

• 2 billion 16-bit Memory Access Cycles at250 MHz

• 12 GBytesper second of internal memorybandwidth for data and instructions

• 600 MFLOPS (to 10 GFLOPS) processingpower (PC=10-20 MFLOPS)


When to use a DSP

• Used when large repetitive computationsmust be performed in real-time.

• Normally a DSP or array of DSPs are hostedby a PC or micro-controller

• Applications are mainly signal processing:speech, vision, radar.

• http://www.analog.com/industry/dsp/overview /index.html


ASIC Chips

• “Application Specific Integrated Circuit”

• Perform a very specific function in hardware

• Often combine the functionality of a number

of other components in a single package

• Can be used to lower production cost for highvolume applications

• Hardware implementations are significantlyfaster than operations in software


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Example ASIC : Entertainment

• To lower productioncosts, the CPU,

graphics and audioprocessors arecombined into a singleASIC.

• The ASIC is acustomized chip createdto manage all of thecomponents that wouldotherwise be handled bythree separate chips.


Example ASIC : Multimedia

• Provides highly-integratedsolutions for high-quality

decoding of MPEG-1 andMPEG-2

• Positioned as a cost-effectivesolution for streaming videoclients, set-top boxes, mediagateways and video endpoints,enabling manufacturers toeasily incorporate streamingvideo, DVD playback, video-on-demand and video over IP intotheir products


Example ASIC : Avionics

• Analog ASICs used inavionics systems forEurofighter Typhoon. TheASIC realises the function

of a dual LVDT receiver(Linear Variable DifferentialTransformer).

• About 60 ASICs per aircraftare used in the FlightControl Computers and inthe pilot sticks to measurevarious mechanicalpositions and movements.


Field Programmable Gate Arrays

(FPGA)

• FPGAs consist of a (large) array of logicgates.

• FPGAs are programmed by connectingsequences of gates together to provide

required computation.

• Programs consist of multiple threads of logic

elements.

• FPGA is then clocked, so running all gateseither in parallel or as a pipeline.


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An Array of Logic Gates:

http://www.altera.com


Logic Array Block

• The logic array containslogic array blocks(LABs) composed of 10logic elements (LEs)

• Communicate through afully populated localinterconnect structure.


FPGA Performance Figures

Table 1: FLEX6000 Performance

Benchmark Gates -1 Speed

Grade

-2 Speed Grade -3 Speed Grade

16-bit loadable counter 16 172 MHz 153 MHz 133 MHz

16-bit accumulator 16 172 MHz 153 MHz 133 MHz

24-bit accumulator 24 136 MHz 123 MHz 108 MHz

16-to-1 multiplexer 10 12.1 ns 13.4 ns 16.6 ns

16 x 16 multiplier, 4 -stage pipeline 592 84 MHz 67 MHz 58 MHz

8- bit, 16- tap parallel finite impulse response (FIR) filter 599 94 MSPS 80 MSPS 72 MSPS

8-bit, 512 point fast Fourier transform (FFT) 1,166 75 µS63 MHz

89 µS53 MHz

109 µS43 MHhz

a16450 universal asynchronous receiver/transmi tter (UART) 478 36 MHz 3 0 M Hz 25 MHz

PCI bus target with one wait state 398 56 MHz 49 MHz 42 MHz


When to use an FPGA

• FPGAs are used as a low-volume ASIC

(application specific integrated circuit)

• High-speed implementation of repetitive

functions (I/O,signal processing,etc)• Parallel implementation of a range of

functionalities.

• FPGA can often be used to remove a great

many support chips (even a whole board)

• C++ programming (hardware compilation)


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Other Major Elements

• A/D Converters

• D/A Converters

• Parallel Bus

• Serial Bus


Analog to Digital Converter (ADC)

• Take as input an analog signal• Sample signal and output a digital number

• Key Parameters:

– Digital Resolution (8,10,12,16 bit)

– Sampling frequency (100KHz-10MHz)

• Input ranges normally +/-5 volts (may require

amplification or scaling)


A/D Converters

D0-D7

Clock

SyncWrite

ReadSet

I n t e r f a c e

Sample and Hold ADC

Controller

Data Register

V+ V-

Vref Gnd

Analog In

Data to

Computer


Typical ADChttp://www.national.com/pf/AD/ADC12041.html

On-Board Reference No

Resolution 12 bits

Conversion Time (us) 3.60

Differential Input Yes

Input Sample/Hold Yes

Input Multiplexer 1

Digital Interface Parallel

Software Powerdown Yes

Onboard Controller Yes

Conversion Accuracy (LSB) 1

ADC12041


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ADC Specification

(f CLK

= 12 MHz)

Resolution 12-bits + sign

13-bit conversion time 3.6 µs, max

13-bit throughput rate 216 ksamples/s , min

Integral Linearity Error (ILE) ±1 LSB, max

Single supply +5V ± 10%

VIN

range GND to VA+


Digital to Analog Converter (DAC)

• Take input (from computer) as a digital

number

• Output an analog signal proportional to

digital number

• Key Parameters:

– Digital Resolution (8 bit usually)

– Settling time

• Output range normally 0-5 volts (subsequentscaling and amplification)


DAC

Digital

Input

Vout

GroundDAC

http://www.national.com/ds/DA/DAC0800.pdf


DAC Performance

Parametric Table

Resolution 8-Bit

Settling Time to 1/2 LSB(ns)

100

Number of Channels 1

Digital Interface parallel

Supply Voltage ± 5 V to ± 15 V

•Nonlinearity over temperature:±0.1%•Full scale current drift: ±10

ppm/°C•High output compliance: -10Vto +18V•Complementary currentoutputs•Interface directly with TTLWidepower supply range: ±4.5V to±18V•Low power consumption: 33mWLow cost


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Parallel I/O

• Programmable Interface Chip:

– Bus interface, typically 8-bit

– Control lines - CS, OE, WE, Reset

– A few address lines - A0, A1

– Special-purpose internal registers for controland status

• Direct Memory Access (DMA)


8255 PPI(Programmable Peripheral Interface)


Memory-mapped I/O

• Memory locations appear as I/O ports

• No separate instructions to access I/O

devices

– eg LD operates on memory & I/O• CPU and I/O devices can share memory

D0-D7

A0-A15

R/W

CPU


Serial I/O

• Parallel data words, put out on a clocked

single (serial) line.

Drivers

D0-D7Data

A0-A16

Address

Clock

Serial

Line

Ready

Tx/Rx

S e r i a l Dr i v e r


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Serial I/O

• Many Standards:

– RS232

– RS424

– CAN (automotive)

– USD

• Many implementations:

– Twisted pair

– Fibre

– Coax


Algorithms for Embedded Systems

• Key attributes (differences between

embedded and normal code):

– Real Time

– Interface to real devices

– Robust to component failure

– Robust to self-failure


Real Time

• Able to perform calculations by a time deadline

• Tie calculations to physical external timers

Initialise_Loop();TICK=Sample_interval;

Out_Time=TICK+get_time();Loop:

time=get_time();output=calculations(time);

wait_until(Out_Time);write(output);

Out_Time=Out_Time+TICK;End Loop;


Device Interface

• Device independence (Device Drivers)

• Timing/resource issues with device

Get_address();Format_message();

Loop:Transmit(byte);

Acknowledge();End Loop:

……

Write(Output);

……

User CodeDevice Driver

Hardware and Software Device

Sensor ?


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Component Failure

• Check that components are operational

• Fail in some safe manner

If(write(output)==FAIL) {

apply_brakes(Now);flash_lights(red);

enable_panic_mode();}

Else {flash_lights(green);

pulse(No_Worries);}

Something

Is Broken


Self Failure

• The most common failure mode is software

• Use of heart-beat signal or watch-dog timer

• Heart beat ties all system components together

Loop:

output=calculations(time);wait_until(Out_Time);

write(output);Out_Time=Out_Time+TICK;

Signal_watch_dog(1);End Loop;

System

Power In

NormallyOpen Switch

‘Keep Closed’

Signal


Computing: Summary

1. Embedded Computing Systems

2. Embedded Systems Processors

3. Input and Output

4. Communications

5. Real-time algorithms

Documents

6.Computing Mecatrónica