Simple Robots and Microprocessors

I. Introduction

A robot is a virtual or mechanical artificial agent. In practice, it is usually an electro-mechanical machine which is guided by computer or electronic programming, and is thus able to do tasks on its own. Another common characteristic is that by its appearance or movements, a robot often conveys a sense that it has intent or agency of its own. While A microprocessor incorporates most or all of the functions of a central processing unit (CPU)on a single integrated circuit (IC).

II. Microprocessor

A microprocessor incorporates most or all of the functions of a central processing unit on a single integrated circuit (IC)The first microprocessors emerged in the early 1970s and were used for electronic calculators, using binary-coded decimal (BCD) arithmetic on 4-bit words. Other embedded uses of 4- and 8-bit microprocessors, such as terminals, printers, various kinds of automation etc, followed rather quickly. Affordable 8-bit microprocessors with 16-bit addressing also led to the first general purpose microcomputers in the mid-1970s

Computer processors were for a long period constructed out of small and medium-scale ICs containing the equivalent of a few to a few hundred transistors. The integration of the whole CPU onto a single chip therefore greatly reduced the cost of processing capacity. From their humble beginnings, continued increases in microprocessor capacity have rendered other

forms of computers almost completely obsolete (see history of computing hardware), with one or more microprocessor as processing element in everything from the smallest embedded systems and handheld devices to the largest mainframes and supercomputers.

III. When It Comes Into Existance:

It is interesting to note thatthe microprocessorhad existed for only 10 years prior to the creation of the PC. Intel inventedthe microprocessorin 1971; the PC was created by IBM in 1981. Now more than 20 years later, we are still using systems based more or less on the design of that first PC. The processors powering our PCs today are still backward compatible in many ways with the 8088 that IBM selected for the first PC in 1981.

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November 15, 2001 marked the 30th anniversary ofthe microprocessor, and in those 30 years processor speed has increased more than 18,500 times (from 0.108MHz to 2GHz).The 4004 was introduced on November 15, 1971 and originally ran at a clock speed of 108KHz (108,000 cycles per second, or just over one-tenth a megahertz). The 4004 contained 2,300 transistors and was built on a 10-micron process. This means that each line, trace, or transistor could be spaced about 10 microns (millionths of a meter) apart. Data was transferred 4 bits at a time, and the maximum addressable memory was only 640 bytes. The 4004 was designed for use in a calculator but proved to be useful for many other functions because of its inherent programmability. For example, the 4004 was used in traffic light controllers, blood analyzers, and even in the NASA Pioneer 10 deep space probe!

In April 1972, Intel released the 8008 processor, which originally ran at a clock speed of 200KHz (0.2MHz). The 8008 processor contained 3,500 transistors and was built on the same 10-micron process as the previous processor. The big change in the 8008 was that it had an 8-bit data bus, which meant it could move data 8 bits at a timetwice as much as the previous chip. It could also address more memory, up to 16KB. This chip was primarily used in dumb terminals and general-purpose calculators.

The next chip in the lineup was the 8080, introduced in April 1974, running at a clock rate of 2MHz. Due mostly to the faster clock rate, the 8080 processor had 10 times the performance of the 8008. The 8080 chip contained 6,000 transistors and was built on a 6-micron process. Similar to the previous chip, the 8080 had an 8-bit data bus, so it could transfer 8 bits of data at a time. The 8080 could address up to 64KB of memory, significantly more than the previous chip.

It was the 8080 that helped start the PC revolution because this was the processor chip used in what is generally regarded as the first personal computer, the Altair 8800. The CP/M operating system was written for the 8080 chip, and Microsoft was founded and delivered its first product: Microsoft BASIC for the Altair. These initial tools provided the foundation for a revolution in software because thousands of programs were written to run on this platform.

In fact, the 8080 became so popular that it was cloned. A company called Zilog formed in late 1975, joined by several ex-Intel 8080 engineers. In July 1976, it released the Z-80 processor, which was a vastly improved version of the 8080. It was not pin compatible but instead combined functions such as the memory interface and RAM refresh circuitry, which enabled cheaper and simpler systems to be designed. The Z-80 also incorporated a superset of 8080 instructions, meaning it could run all 8080 programs. It also included new instructions and new internal registers, so software designed for the Z-80 would not necessarily run on the older 8080. The Z-80 ran initially at 2.5MHz (later versions ran up to 10MHz) and contained 8,500 transistors. The Z-80 could access 64KB of memory.

RadioShack selected the Z-80 for the TRS-80 Model 1, its first PC. The chip also was the first to be used by many pioneering systems, including the Osborne and Kaypro machines. Other companies followed, and soon the Z-80 was the standard processor for systems running the CP/M operating system and the popular software of the day.

Intel released the 8085, its follow-up to the 8080, in March 1976. Even though it predated the Z-80 by several months, it never achieved the popularity of the Z-80 in personal computer systems. It was popular as an embedded controller, finding use in scales and other computerized equipment. The 8085 ran at 5MHz and contained 6,500 transistors. It was built on a 3-micron process and incorporated an 8-bit data bus.

Along different architectural lines, MOS Technologies introduced the 6502 in 1976. This chip was designed by several ex-Motorola engineers who had worked on Motorola’s first processor, the 6800. The 6502 was an 8-bit processor like the 8080, but it sold for around $25, whereas the 8080 cost about $300 when it was introduced. The price appealed to Steve Wozniak, who placed the chip in his Apple I and Apple II designs. The chip was also used in systems by Commodore and other system manufacturers. The 6502 and its successors were also used in game consoles, including the originalNintendo Entertainment System(NES) among others. Motorola went on to create the 68000 series, which became the basis for the Apple Macintosh line of computers. Today those systems use the PowerPC chip, also by Motorola and a successor to the 68000 series.

All these previous chips set the stage for the first PC processors. Intel introduced the 8086 in June 1978. The 8086 chip brought with it the original x86 instruction set that is still present in current x86-compatible chips such as the Pentium 4 and AMD Athlon. A dramatic improvement over the previous chips, the 8086 was a full 16-bit design with 16-bit internal registers and a 16-bit data bus. This meant that it could work on 16-bit numbers and data internally and also transfer 16 bits at a time in and out of the chip. The 8086 contained 29,000 transistors and initially ran at up to 5MHz.

The chip also used 20-bit addressing, so it could directly address up to 1MB of memory. Although not directly backward compatible with the 8080, the 8086 instructions and language were very similar and enabled older programs to quickly be ported over to run. This later proved important to help jumpstart the PC software revolution with recycled CP/M (8080) software.

Although the 8086 was a great chip, it was expensive at the time and more importantly required expensive 16-bit board designs and infrastructure to support it. To help bring costs down, in 1979 Intel released what some called a crippled version of the 8086 called the 8088. The 8088 processor used the same internal core as the 8086, had the same 16-bit registers, and could address the same 1MB of memory, but the external data bus was reduced to 8 bits. This enabled support chips from the older 8-bit 8085 to be used, and far less expensive boards and systems could be made. These reasons are why IBM chose the 8088 instead of the 8086 for the first PC.

IV. Simple Robots

The International Organization for Standardization gives a definition of robot in ISO 8373: “an automatically controlled, reprogrammable, multipurpose, manipulator programmable in three or more axes, which may be either fixed in place or mobile for use in industrial automation applications.”

The Robotics Institute of America (RIA) uses a broader definition: a robot is a “re-programmable multi-functional manipulator designed to move materials, parts, tools, or specialized devices through variable programmed motions for the performance of a variety of tasks”.

According to Encyclopedia Britannica, a robot is “any automatically operated machine that replaces human effort, though it may not resemble human beings in appearance or perform functions in a humanlike manner” Merriam-Webster describes a robot as a “machine that looks like a human being and performs various complex acts (as walking or talking) of a human being”, or a “device that automatically performs complicated often repetitive tasks”, or a “mechanism guided by automatic controls”.

V. Line Follower Robot As Simple Robot

I have taken the example of line follower robot as the simple robot and is shown in fig

Line follower robot is an autonomous mobile robot that can follow a path. The path can be a white pah on a black surface or a black path on a white surface. Line follower robots are usually entertainment hobby robots. However, they can be improved and used in industry in order to carry some loads on a definite path or in markets and cafes for similar purposes. The important point of building a line follower robot is a good control that is sufficient to follow the path as fast as possible

A. The circuit

All we need is an IR source, an IR photo-transistor and a couple of resistors! Here are the resources:

IR emitters and detector pairs: UK – Maplins,CH10L and CH11M, or SFH409 and SFH309. Obviously the line following robot will need to see the line, therefore we require an light detector of some sort. We also would like it if the line following robot could do this regardless of the ambient conditions (is the room dark or light? is it lit by sunlight or artificial light?). So the robot will also need its own illumination source. The weapon of choice here will be Infra Red light. To make this easy for ourselves the light only needs to be constant. if a white line is present then it will reflect a lot of IR from our source. If the line is black then we see the opposite effect.

IR emmiters and detector pairs: US – Solarbotics QRD1114 (this has both in one package)

On top of these, it would be nice if the signal that we get could be TTL (on or off, 0V, 5V). So to do this we will also require our favourite BEAM chip, the 74AC240, heres the circuit:

Circuit operation is simple…. no line to follow put the input to the inverter high, and therefore the inverter outputs a low, line detection turns on the transistor (or photodiode) and thus the inverter gets a low and outputs a high. If your robot is following a black line on a white page, then add another invereter after or before the first. So what should the values for R1 and R2 be? and how do I set up the 74AC240 chip exactly….. The value for R1 affects the source IR brightness, for maximum brightness we set R1 to give the maximum allowable forward current for the IR led. The chip setup is simple too… ground pins 1, 10 and 19, put 5V onto pin 20. Now choose a pin to input your signal to, if you look at the74AC240 datasheeton page 1, you will see a connection diagram, any pin with an I is an input, follow it across to find its output. Pins 1 and 19 are the enable pins, which we have grounded to permanently enable the inputs on both side of the chip, this leaves you free to use any of the input pins. For example (in case I haven’t spelt it out enough already)… input your signal at pin 4 and take the ouput from pin 16.

The output signal could be used to directly drive your motor… just connect one side of the motor to the ouput, and the other side to ground. If you do this for two motors (2 sets of line detectors will require two sets of emitters and detectors, but only one 74AC240 chip), then you have a basic line follower already. The left detector should be used to drive the right motor and vice versa .The behaviour of this robot as it stands will be too turn a motor on IF a line is present, if both detectors are over the line then it will drive straight, if the left detector goes of the line, it will turn off the right motor causing the robot to turn back onto the line, if the right detector goes off the line then it will turn off the left motor and again go back onto the line. If both detectors come off the line (end of line) then the robot will stop altogether

Electronic

VI. Microprocessor And Simple Robotics

I have taken the example of line follower for simple robot. As shown in the fig. it consists of three units i.e. input, control, and output unit

The control unit comprises of microprocessor. The function of all the units is given below:

A. Input unit

Input units consist of the sensors that detect the white path on black surface or the black path on white surface. QRD1114 IR reflective line/object sensor and CNY70 reflective optical sensor are the most commonly used sensors for line follower robots.
The CNY70 is a reflective sensor that includes an infrared emitter and phototransistor in a leaded package which blocks visible light.
The emitted IR of CNY70 reflects on the surface back to the phototransistor part and affects the base of the phototransistor. The black or white colour of the IR reflection surface causes different analog signals on the output of CNY70. To convert the analog output signals of CNY70 into digital signals in order to transport them to the microprocessor, 74HC14 Schmitt Triger can be used. When CNY70 sensor detects white, the analog signal is 5 V and 74HC14 converts it into logic 1. When CNY70 sensor detects black, the analog signal is 0 V and 74HC14 converts it into logic 0.

The QRD1113/14 reflective sensor consists of an infrared emitting diode and an NPN silicon photodarlington mounted side by side in a black plastic housing. The on-axis radiation of the emitter and the on-axis response of the detector are both perpendicular to the face of the QRD1113/14. The photodarlington responds to radiation emitted from the diode only when a reflective object or surface is in the field of view of the detector.

B. Output unit:

For a line follower robot two dc geared motors are enough. The motor driver circuit can be prepared by using darlington transistor on a H bridge motor driver circuit or by using an integrated motor driver circuit like L293D or L298. The diagram shows the driving of the motors.

C. Microprocessor as control unit

The control unit is the microprocessor part of the robot. The microprocessor, also known as the central processing unit (CPU), is essentially what makes a computer work. The microprocessor forms the heart of the computer, along with the memory.

The balance of the computer — keyboard, monitor and mouse — is known as peripherals. While peripherals are important for users to be able to work with a computer, they are useless without a functioning microprocessor. Same is the case in case of robotics. There will be no use of input and output unit until microprocessor is not there ac control unit. As in case of computer it takes input control the execution of instruction similarly in Line Follower the microprocessor takes the input signals from the sensors, use them in its program and make decision of the next movement of the line follower robot to follow the path. The output signals are transferred to the motor driver parts of robot. The most commonly used microprocessors are the pic microprocessors produced by microchip.

VII. Application

• Software control of the line type (dark or light) to make automatic detection possible.
• “Obstacle detecting sensors” to avoid physical obstacles and continue on the line.
• Distance sensing and position logging & transmission
• Industrial automated equipment carriers
• Automated cars.
• Tour guides in museums and other similar applications.
• Second wave robotic reconnaissance operations.

VIII. Recent Discovery In Robotics

Till now we were trying to discover the robots which can help the human being in different ways like in medical science in industries, in defence etc. But now robot has become itself scientist. Recently in April 2009 the Robot Scientist has discovered its first discovery. Now ADAM is the first robot—but maybe not the last—to have independently discovered new scientific information, according to scientists who recently built themselves the mechanical colleague. So in future scope of robotics is quite bright.

IX. Reference:

http://en.wikipedia.org/wiki/Robotics

http://en.wikipedia.org/wiki/Microprocessor

http://eces.colorado.edu/~prasadae/LFR

http://news.nationalgeographic.com/news/2009/04/090402-robot-scientists.html

http://www.robotiksistem.com/linefollower.html