Automatons

1. automatons

2. WHAT IS A ROBOT
The Three Laws Of Robotics
(ISAAC ASIMOV)
A robot may not injure a human being, or, through inaction,
allow a human being to come to harm.
A robot must obey the orders given it by human beings
except where such orders would conflict with the First Law.
A robot must protect its own existence as long as such
protection does not conflict with the First or Second Law.

3. An autonomous robot is simply a self-contained robot
that receives no assistance from outside, not even power.
WHAT IS AN AUTONOMOUS ROBOT

4. THE BUILDING BLOCKS OF A ROBOT
Mechanical Blocks
Electronics
Computer Code Or Firmware
Intelligence
Shall we start …

6. CHASSIS DESIGN
ACTUATORS
MOTORS-DC AND STEPPERS
WHEELS
CASTORS
MATERIALS FOR CHASSIS DESIGN AND TOOLS
WEIGHT AND POWER CONSIDERATIONS
BUILDING SMALL ROBOTS

7. CHASSIS DESIGN
TRICYCLE
FOUR WHEELED DRIVE
TRACKED PLATFORMS

8. TRICYCLE

9. FOUR WHEELED DRIVE

10. TRACKED PLATFORMS

11. ACTUATORS
An actuator is a transducer that will convert one form
of energy to mechanical movement.
For example a motor, hydraulic cylinders, solenoids etc

12. MOTORS
A motor converts electrical energy to rotational movement.
TYPES OF MOTORS USEFUL FOR A ROBOT
DC MOTORS
STEPPER MOTORS

13. Consists of two wires externally.
Turn clockwise or anticlockwise when either wire
is at a higher potential than the other.
Normally have to be geared to provide working torque.
Robots that work autonomously should restrict
speeds over 100 rpm for driving motors.
More In The Electronics' Part Of Dc Motors…

14. These are motors that rotate in steps up on an
external command.
Excellent when accurate positioning is required.
Have very minimal torque and hence design
of the robot becomes critical
But are a good alternative to DC motors
They can consume larger currents as compared to DC
motors of comparable sizes.
More In The Electronics' Part Of Steppers…..

15. The next most important part of the robot is its wheels.
Wheels determine the pulling force of the robot, its speed, and
actually its height.
A back of the hand formula is that the larger the wheel the lower
the available force and higher the speed.
Select the lowest possible wheel diameter for the task at hand

16. The simple calculation comes from the torque formula
F=r x T
So a larger wheel calculates to a high speed but a low pulling force

17. WHEEL MATERIALS
Aluminium
Advantages
Looks very professional and robot looks neat.
Highly load bearing and stiff
Does not get corroded easily and will not sag or swell like wood.
Disadvantages
A little bit expensive but wheels last long.
Slightly difficult to work with and hence have to be machined
(actually bad when things fall off on last day)
Slightly heavy and have to be spoked to reduce weight.

18. NYLON
Advantages
Gives a clean look
Load bearing and stiff
Does not get corroded easily and will not sag or swell like wood.
Affordable and light weight.
Has to be machined

19. WOOD
Absolute no no!!

20. CASTORS
A castor is a free wheel that can rotate in any
direction in one plane
A castor is a wheel that normally attached to trolleys,
cabinets etc.
Such a wheel provides a third point of balance in tricycle
type chassis and turns in any direction thus allowing
smooth turns

21. MATERIALS FOR CHASSIS DESIGN
ALUMINIUM
Available in various cross sections.
Can be easily visualised in the requisite shape.
But can be time consuming and demanding to cut, drill and bend.
Chassis is very lightweight and durable.

22. ACRYLIC
Available in sheets of various thickness and sizes.
Can be cut, drilled very easily.
Cheap material for good design.
Brittle and not very strong.
Leaves irritating shavings after work.

23. TOOLS
Hacksaw for both wood and metal.
Small bench vice.
Hand drill with standard bit sizes.
Other tools like hammer, pliers ,spanners etc

24. BUILDING SMALL ROBOTS
All devices are miniaturised
Motors are available in small sizes

25. SOME ADVICE
Mechanic assemblies are a one time investment
Build and machine good wheels and a stiff chassis
The best design is a two motor configuration with two
castors as front wheels
Choose the smallest diameter possible.
The alignment should be very accurate and the robot should not be
correcting itself every time because of misalignment.
Motors have to be dead straight.
Always this is achieved by a professional turner.
Weight of the robot should be as low as possible.

28. SIGNAL REPRESENTATION,BOOLEAN LOGIC
THE PRINTER PORT
DC and stepper motor introduction
Interfacing to motors and sensors
MOTOR INTERFACING METHODS
DC motors
Stepper Motors
SENSORS AND CONFIGURATIONS

29. Programmable Devices
Using Embedded Devices-Processors And Controllers
Introduction To Devices And Design
The Common Controller Families-8051, PIC And AVR
The ATMEGA8535-Controller For Robotic Applications
Features Of This Device And Peripherals
Interfacing To Motors And Sensors
Battery Technology And Regulators

30. SIGNAL REPRESENTATION
AND BOOLEAN LOGIC
Boolean logic is a branch of study that deals with quantities
represented by either yes(1) or no(0).
All decimal numbers can be broken down to digital numbers by using
base 2 computation.
In terms of voltages we assign 5V as logic 1 and 0V as logic 0 in
digital electronics.

31. THE PRINTER PORT
The printer port is a 25 pin female connector found on most
modern computers.
It is possible to command the printer port to set (1)or reset (0)
certain pins by writing a program on the computer. Such pins are
called output pins
It is also possible to read the value of certain pins on the port and
these can also be read by program. Such pins are called input pins
So if we configure the motors to be connected (via a motor driver) to
the output pins and sensors to input pins, and use a certain logic to
control the motors depending on the sensor values, it is possible to
control a robot whose parts are those sensors and motors.

32. THE PRINTER PORT PINS

33. OUTPUTTING VALUES FROM THE PORT
The data port is used as the output port.
The address of the data port is 0x378(base) on most computers.
In C if a command like
Outportb(0x378,4); // base=0x378
Is executed then the value of data port pins will be
(0 0 0 0 0 1 0 0) // binary for 4

34. INPUTTING VALUES FROM THE PORT
There are two input ports on the printer port
status port (base+1) and control port (base+2)
Both have less than 8 pins as inputs and have to be
used in conjunction for more inputs (upto 8)
A statement like
int c;
c=inportb(0x379); // 0x379=base+1
Will read the status port and store the read value in
variable c

36. DRIVING MOTORS
The H-bridge
The H-bridge is a transistor based circuit that can input digital
logic value and switch a connected motor clockwise or anticlockwise.

37. If switches A and D are on then current flow from the supply ,
Switch A ,coil, switch D and ground.
If switches B and C are on then current flow from the supply ,
Switch B ,coil, switch C and ground.

38. THE L293 AND L298
Both these integrated circuits are two H-bridges in a single package.
They have 4 signal inputs that select witch transistor is on and 4
output pins to which we connect motors
Other pins include digital power, motor power, GND pins, inhibit
pins and current limit pins.
L293 is available in DIP package so has a rating of 1 AMP for both
bridges collectively.
The L298 is a beefy version and can have a total rating of 2 AMPS with
a heat sink to be connected externally.

39. L298

40. STEPPER MOTORS
TYPES OF STEPPER MOTORS
Unipolar Motors(5 Wire Or 6 Wire)
Bipolar Motors(4 Wire)
All the above motors just about have the same internal windings
but the difference come in the way they are driven
Unipolar motors can be driven by either discrete transistors or H
bridges
Bipolar motors are exclusively driven by H-bridges

41. A stepper motor has four phase windings named
A B C D
When a phase is excited it means that that
phase has current flowing through it
A particular phase sequence imparts rotation
to the motor
The two excitation sequences are
HALF WAVE AND FULL WAVE

42. HALF WAVE EXCITATION
The phase sequence for a particular direction of rotation is
A-B-C-D-A-B-C-D-A-B …………
To reverse the direction of rotation the sequence is
D-C-B-A-D-C-B-A ……..
FULL WAVE EXCITATION
The phase sequence for a particular direction of rotation is
A- AB- B- BC- C- CD- D- DA- ……
To reverse the direction of rotation the sequence is
D- CD- C- BC- B- AB- A- ……

43. The ULN2803
This is an IC that contains 8 Darlington's with diode protection
This is used to control only an unipolar stepper motor
It is rated for 500mA and 36 V.
The cheapest solution to drive a stepper motor.
Every phase has to be individually set or reset.

44. UCN 5804
This IC has in built logic to drive an unipolar stepper motor.
The only inputs that are required are clock, direction
and whether the excitation is full or half wave.
Expensive.

45. SPEED CONTROL OF MOTORS
DC MOTORS
Speeds of dc motors can be controlled by using
Pulse width modulation or PWM
STEPPER MOTORS
Speed control can be done by changing the time
Interval between two successive steps.

46. SENSOR INTERFACING
The types of sensors are
Active and Passive
Depending on the type the configuration of the sensor
changes
For passive sensors the most common configuration is of a
potential divider.

47. LIGHT SENSORS
INFRARED SENSORS
These are two pin devices available in pairs-transmitter and receiver
the transmitter is forward biased and the receiver is reversed biased.
When the receiver is irradiated with infrared light its resistance
decreases.
PHOTOTRANSISTORS
These are three pin devices of which only two pins are used .
The configuration is same but this sensor is “blind” to infrared light
It has sensitivity to visible light

48. ROBOT CONTROL USING PRINTER PORT

49. LOOKING BACK

51. MICROPROCESSORS AND
MICROCONTROLLERS
A microprocessor is a device that does sequencing of
instruction that is written to its associated memory.
A microcontroller is same as a microprocessor but has its
memory and other peripherals associated with it in a single IC
package.
We will concentrate on microcontrollers but will dwell a little bit
into microprocessors.
Example 8085

52. COMMON MICROCONTROLLER
FAMILIES
8051
First microcontroller to be launched.
Very used and hence lots of programming resources.
8051 derivatives are also available with multiple
Features.
Not a good choice for robotics applications.
Messy programming interface.
Still in use today for embedded applications.

53. PIC-PERIPHERAL INTERFACE CONTROLLER
Good microcontroller family
Programming resources also available
Programmer mode is ICSP (In Circuit Serial Programmer)
One programmer fits all devices
Available in variety of cost and features
Suited for small robotic applications.
Never used it !!!

54. FEATURES OF ATMEGA8535
8 bit microcontroller with RISC architecture
On board 10 bit 8 channel ADC with highest sampling upto
15 kHz
Onboard UART with independent receive and transmit
registers
4 ports with high drive capability
8kb of on chip flash memory with ISP programmability
One programmer fits all devices
512 byte of SRAM and 512 bytes of EEPROM
3 timers with PWM function

55. PROGRAMMER SCHEMATIC FOR AVR

56. BATTERY TECHNOLOGY
OPTIONS FOR BATTERIES
SEALED LEAD ACID OR SLA BATTERIES
Ni-Cd BATTERIES
Ni-MH BATTERIES

57. CELL CHARACTERSTICS

58. VOLTAGE
REGULATORS
These are three pin devices whose output voltage is approximately a
constant over a large range of input conditions.
The 78XX series of voltage regulators is popular. The XX stands for
the output voltage that a certain device will deliver. For e.g.
A 7805 voltage regulator will deliver output voltage at 5 volts.
These devices at least need input voltage about 2 volts
higher than the output.
A 7805 regulator is required to provide constant voltage for
logic circuitry.