D R . T A R E K A . T U T U N J I

M I C R O C O N T R O L L E R S Y S T E M S

P H I L A D E L P H I A U N I V E R S I T Y

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Controllers Overview

Control Systems

The control system is at the heart of mechatronic systems and its selection is arguably the most critical decision in the design process.

The controller selection involves two inter-dependent parts:

The control method (i.e. software)

The physical controller (i.e. hardware)

O P E N V S . C L O S E D L O O P C O N T R O L

P R O C E S S V S . M O T I O N C O N T R O L

T R A N S I E N T A N D S T E A D Y S T A T E S P E C I F I C A T I O N S

Basic Control Concepts

Open-Loop Control

[Ref] Kilian

Closed-Loop Control

[Ref] Kilian

Control Systems Classification

Control systems are classified by application.

Process control usually refers to an industrial process being electronically controlled for the purpose of maintaining a uniform correct output.

Motion control refers to a system wherein things move. A servomechanism is a feedback control system that provides remote control motion of some object, such as a robot arm or a radar antenna.

Motion Control Examples

[Ref] Kilian

CNC Machine Robot Manipulator

Process Control Example

[Ref] Kilian

General Control System

First Order Systems

2nd Order Systems: Performance Criteria

T A R E K A . T U T U N J I

Control Methods

Dr. Tarek A. Tutunji

Control Techniques / Strategies

Classical Control

Advanced Control

Intelligent Control

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Classical Control

Classical control design are used for SISO systems.

Most popular concepts are:

Bode plots

Nyquist Stability

Root locus.

PID is widely used in feedback systems.

Classical Control: On-Off Control

This is the simplest method of control. The control action has three possible outputs: on; off; no change. This method is usually used for slow-acting operations (such as a refrigeration unit).

The advantage is its ease of design and low cost. However, it cannot vary the controlled variable with precision.

On-Off Control Example

Classical Control: PID

Dr. Tarek A. Tutunji

Proportional-Integral-Derivative (PID) is the most commonly used controller for SISO systems

dt

)t(deKdt)t(eK)t(eK)t(u DIp

Analog PID Implementation

[Ref] Kilian

Digital PID Control

Digital

Analog

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Digital PID Realization

Required Operations: •Multiplication •Addition •Delay

Discrete PID Implementation

Digital Control Block Diagram

Intelligent Control

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Intelligent controllers are used for high-level control

Intelligent controllers are also used when the system must make decisions (from several alternatives) based on input data from sensors.

Intelligent Control is usually used when the mathematical model for the plant is unavailable or highly complex.

The most two commonly used intelligent controllers are

Artificial Neural Networks

Fuzzy Logic

Intelligent Controllers Applications

[Ref] Tunstel

Intelligent Controller Application

•Low Level PID Control for velocity control •High Level Intelligent Control:

•Fuzzy for Decision making •Neural nets for Image Analysis

D R . T A R E K T U T U N J I

Hardware Controllers

Analog vs. Digital Control Systems

Analog Digital

Time variable Continuous Discrete

Time equations Differential equations Difference equations

Frequency transforms Laplace Z-Transform

Stability Poles on LHS Poles inside unit circle

Controller Hardware: Op-Amps Software: None

Hardware: Microcontroller Software: Program

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Criteria for Choosing Controller

Price Size and Weight Number of Digital Inputs and Outputs Number of Analog Inputs and Outputs Speed Required Interrupt Required hardware Communication Interface Reliability Memory Programming Capability Software Support

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Hardware Controllers

Microcontroller

PLCs

DSPs

PC with DAQ

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Microcontrollers

Microcontroller is a special type of small computer that can perform a specific job

Microcontrollers

The microcontroller is a computer-on-chip. It is an integrated circuit that contains microprocessor, memory, I/O ports and sometimes A/D converters. It can be programmed using several languages (such as Assembly or C/C++). It can be used in manufacturing lines, but requires additional hardware. Microcontrollers are mainly used in engineering products such as washing machines and air-conditioners.

Dr. Tarek A. Tutunji

Microcontrollers Companies

Microcontroller Market Share

PIC16F84

PIC16F877

Arduino

Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software.

The hardware consists of a simple open source hardware board designed around an 8-bit Atmel AVR microcontroller, though a new model has been designed around a 32-bit Atmel ARM

Arduino Uno

Arduino Uno

UNO vs. MEGA

PLCs

A Programmable Logic Controller (or PLC) is a specialized digital controller that can control machines and processes. it monitors inputs, makes decisions, and controls outputs in order to automate machines and processes

Programmable Logic Controller

PLC’s are a user-friendly, microprocessor-based, specialized computer that is used for process control. It contains input/output (I/O) modules for appropriate sensors/actuator interfaces. It is mainly used in automated manufacturing lines. The PLC is usually used for simple logic operations. It is considered reliable and easy to program (using ladder diagrams, instructions, or function blocks).

Dr. Tarek A. Tutunji

PLC Manufacturers

PLC vs. Microcontroller

Usually PLCs are used in an industrial environment, where as the microcontrollers are smaller and well suited for embedded situations.

PLCs are programmed with ready made blocks or programming elements, whereas in Microcontrollers a programming language must be used to write a programming code

PLC Advantages

They are highly reliable, fast and flexible.

They can handle severe conditions such as dust, humidity etc.

They can communicate with other controllers.

They are easy to program and troubleshoot.

They include display units.

Digital Signal Processors

Digital Signal Processing (DSP) is the arithmetic processing of discrete-time signals. A/D is needed for analog signals

Digital signal processors (DSP) are specialized

microprocessors with advanced architectures (such as multiple buses, parallel processing, hardware multipliers and fast sampling rate) that are designed to reduce the number of instructions and operations necessary for efficient processing.

DSP chips enable developers to implement complex

algorithms and perform computationally efficient and fast algorithms. DSP are preferred over microcontrollers when the need for complex and

iterative control algorithms is required.

Dr. Tarek A. Tutunji

Digital Signal Controllers Manufacturers

Texas Instruments.

TMS320C2000™ DSP Platform

Microchip.

dsPIC30F3010

Motorola

Custom made DSP Engines

Personal Computers

Personal computers are used when extensive signal processing and in-depth analysis is required.

This will require Data Acquisition Cards (DAQs) to interface

the I/O power and signals between the PC and the environment.

Advantages include superior graphical and software

flexibility. However, the cost is high and, therefore, they are not suitable

for a large number of products Another disadvantage is the speed

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PCs and DAQs

Summary

The selection of the controller is arguably the most important issue of the mecahtronics system

This choice can be divided into two parts:

1. Software/Firmware algorithm On-Off, PID, Adaptive, Robust, Optimal, and Intelligent

2. Hardware system Microcontroller, PLC, DSP, FPGA, and PC-DAQ

Dr. Tarek A. Tutunji