Microchip Technology MCP6 series Instrukcja Użytkownika Pobierz pdf

 2004 Microchip Technology Inc. DS00900A-page 1

AN900

INTRODUCTION

Previous Microchip authors (Parekh and Yedamale)

have described the implementation of a 3-phase AC

induction motor (ACIM) control with PICmicro

devices. The first application note (AN843) detailed

ACIM control with the PIC18F452. More recently, ACIM

control has been implemented with the PIC16F7X7

family of devices (AN889).

This application note describes how the PIC18F4431

may be used to control an ACIM using open and

closed-loop V/f control strategies. The application code

is built incrementally and demonstrates the following

control methods:

1. Voltage-frequency (V/f) control

2. Voltage-frequency control with current feedback

3. Voltage-frequency control with velocity feedback

and PID control

The PIC18F4431 incorporates a set of innovative

peripherals, designed especially for motor control

applications. The utility of these peripherals is demon-

strated in both open and closed-loop three-phase

ACIM motor applications.

It is assumed that the reader is already familiar with the

theory and nomenclature of AC induction motors. For an

excellent introduction to the basic concepts of induction

motors control, please refer to Microchip’s application

note AN887, “AC Induction Motor Fundamentals”

(DS00887).

USING THE PIC18F4431 FOR MOTOR

CONTROL

Before getting into actual control applications, we

should understand what distinguishes the PIC18F4431

from other Microchip devices used for motor control.

The core is a set of unique peripherals that simplify

external hardware requirements and also enable

higher levels of motor control capability than the

PIC18F452 or PIC16F7X7.

The three peripherals and their features are:

1. Power Control PWM (PCPWM) module:

• Up to 8 output channels

• Complimentary PWM outputs

• Two hardware Fault protection inputs

• PWM resolution up to 14 bits

• Edge-aligned or center-aligned operation

• Flexible dead time

• Simultaneous update of duty cycle and

period

2. Motion Feedback Module (MFM), comprised of

a Quadrature Encoder Interface (QEI) and an

Input Capture module (IC):

• Standard quadrature encoder inputs (QEA,

QEB and Index) (QEI)

• High and Low Resolution Position

Measurement modes (QEI)

• Velocity Measurement mode using Timer5

(QEI)

• Interrupt with configurable priority on event

detection (QEI)

• Pulse Width Measurement and Period

Measurement modes (IC)

• Edge and state change capture (IC)

3. High-Speed Analog-to-Digital Converter

(HSADC):

• Two independent sample-and-hold circuits

• Single or multi-channel selection

• Sequential or Simultaneous Conversion

modes

• Four-word FIFO result buffer with flexible

interrupts

As we shall see, each of these features provides a

distinct advantage in implementing more sophisticated

motor control applications.

Author: Jon Burroughs

Microchip Technology Inc.

Controlling 3-Phase AC Induction Motors Using

the PIC18F4431

1 2 3 4 5 6 ... 23 24

Podsumowanie treści

Strona 1 - INTRODUCTION

 2004 Microchip Technology Inc. DS00900A-page 1AN900INTRODUCTIONPrevious Microchip authors (Parekh and Yedamale)have described the implementation of

Strona 2 - SYSTEM OVERVIEW

AN900DS00900A-page 10  2004 Microchip Technology Inc.DRIVE FREQUENCY CALCULATION FOR V/f CONTROL WITH VELOCITY FEEDBACKThe microcontroller uses the A

Strona 3 - STRATEGIES

 2004 Microchip Technology Inc. DS00900A-page 11AN900PID CONTROL FIRMWAREPID is a well-known, commonly used method of feed-back control. As seen in t

Strona 4

AN900DS00900A-page 12  2004 Microchip Technology Inc.FIGURE 9: CONCEPTUAL BLOCK DIAGRAM FOR CLOSED-LOOP SPEED AND SLIP CONTROL COMPARING MICROCONTROL

Strona 5 - FIRMWARE OVERVIEW

 2004 Microchip Technology Inc. DS00900A-page 13AN900CONCLUSIONThe combination of PIC18 architecture and thoughtfullydesigned peripherals make the PI

Strona 6 - Fault Service

AN900DS00900A-page 14  2004 Microchip Technology Inc.APPENDIX A: PICDEM™ MC BOARD OVERVIEWA PICDEM MC demonstration board was used todevelop, test an

Strona 7

 2004 Microchip Technology Inc. DS00900A-page 15AN900FIGURE A-2: BOARD SCHEMATIC, PART 1 (PIC18F4431 MICROCONTROLLER, PCPWM ISOLATORS, CURRENT COMPAR

Strona 8

AN900DS00900A-page 16  2004 Microchip Technology Inc.FIGURE A-3: BOARD SCHEMATIC, PART 2 (PIC18F2431 MICROCONTROLLER SOCKET,USART, CLOCK OSCILLATOR N

Strona 9 - V/f CONTROL FIRMWARE

 2004 Microchip Technology Inc. DS00900A-page 17AN900FIGURE A-4: BOARD SCHEMATIC, PART 3 (SENSOR AND MICROCONTROLLER HEADER CONNECTORS, MONITOR LEDS)

Strona 10 - PWM Waveform Synthesis

AN900DS00900A-page 18  2004 Microchip Technology Inc.FIGURE A-5: BOARD SCHEMATIC, PART 4 (SIGNAL CONDITIONER FOR SENSORLESS BLDC OPERATION)0.1 µF0.1

Strona 11 - CLOSED-LOOP SLIP CONTROL

 2004 Microchip Technology Inc. DS00900A-page 19AN900FIGURE A-6: BOARD SCHEMATIC, PART 5 (3-PHASE INVERTER POWER MODULE AND SHUNT CURRENT MEASUREMENT

Strona 12 - CONTROL APPLICATIONS

AN900DS00900A-page 2  2004 Microchip Technology Inc.SYSTEM OVERVIEWMotor Drive RequirementsPractically speaking, control of a 3-phase AC inductionmot

Strona 13 - REFERENCES

AN900DS00900A-page 20  2004 Microchip Technology Inc.FIGURE A-7: BOARD SCHEMATIC, PART 6 (MOTOR TERMINAL BLOCK AND OPTIONAL CURRENT TRANSDUCER CIRCUI

Strona 14 - BOARD OVERVIEW

 2004 Microchip Technology Inc. DS00900A-page 21AN900FIGURE A-8: BOARD SCHEMATIC, PART 7 (POWER SUPPLY)LNGDC+DC-NCECACA1OCP/FBVCCDGNDS47 µF10 µH10 µH

Strona 15 - PIC18F4431

AN900DS00900A-page 22  2004 Microchip Technology Inc.APPENDIX B: SOFTWARE DISCUSSED IN THIS APPLICATION NOTEDue to size considerations, the complete

Strona 16 - OPTIONAL

 2004 Microchip Technology Inc. DS00900A-page 23Information contained in this publication regarding deviceapplications and the like is intended throu

Strona 17 - CONNECTORS, MONITOR LEDS)

DS00900A-page 24  2004 Microchip Technology Inc.AMERICASCorporate Office2355 West Chandler Blvd.Chandler, AZ 85224-6199Tel: 480-792-7200 Fax: 480

Strona 18 - BLDC OPERATION)

 2004 Microchip Technology Inc. DS00900A-page 3AN900OVERVIEW OF CONTROL STRATEGIESOpen Loop V/f ControlAC induction motors are often operated in open

Strona 19 - CURRENT MEASUREMENT)

AN900DS00900A-page 4  2004 Microchip Technology Inc.V/f Control with Current FeedbackA disadvantage of open-loop V/f control is that themotor can sta

Strona 20 - CURRENT TRANSDUCER CIRCUITRY)

 2004 Microchip Technology Inc. DS00900A-page 5AN900FIRMWARE OVERVIEWIn this section, we will see in greater detail how thethree control approaches d

Strona 21

AN900DS00900A-page 6  2004 Microchip Technology Inc.FIGURE 6: MAIN LOOP, FAULT AND CONTROL SERVICE ROUTINESFault activity?Key activity?InitializeOver

Strona 22 - APPLICATION NOTE

 2004 Microchip Technology Inc. DS00900A-page 7AN900FIGURE 7: INTERRUPT SERVICE ROUTINE Timer0 overflow?ADC ready?Calculate NewTarget VelocityISR Hig

Strona 23

AN900DS00900A-page 8  2004 Microchip Technology Inc.INITIALIZING THE POWER CONTROL PWM MODULE AND HARDWARE FAULT INPUTSThe Power Control PWM module s

Strona 24 - ORLDWIDE SALES AND SERVICE

 2004 Microchip Technology Inc. DS00900A-page 9AN900INITIALIZING THE QUADRATURE ENCODER INTERFACE When implementing closed-loop V/f control, a form o