MAKING OF MICROMOUSE
P.Raghavendra Prasad Final Yr EEE
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INTRODUCTION
Micromouse is an autonomous robot designed to reach p the center
of an unknown maze in shortest possible time and distance .
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LEFT MOTOR MOTOR DRIVER RIGHT MOTOR
M I C R O C O N T R O L L E RSENSOR ELECTRONICS
SESNSORS
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Basic components of Micromouse: pSensors Motors Microcontroller
Batteries
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SENSORSYour mouse is going to need sensors to tell it about
itself and its environment. These are used to detect the presence
or absence of walls and to verify your position in the maze. They
will also be important in ensuring that the mouse maintains an
appropriate path without hitting any walls
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SensorsCommonly used sensors in the field of robotics IR Di i l
sensors Digital IR analog sensors
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IR Digital sensors TransmitterIR led connected to 38KHz
oscillator
ReceiverTSOP1738
AdvantagesDetects an obstacle at a distance more than 1meter if
tuned perfectly. No ambient light effect. Easy to use.
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Designing a transmitter :Use IC 555 in Astable mode
For approximate 50% duty cycle take Ra = 1 k ohm
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Receiver :
IR Analog sensors TransmitterIR LED
ReceiverIR Photodiode Advantages: Can measure distance up to 15
cm. Disadvantages: Responds to IR rays present in ambient light.
Intensity of reflected rays is non-linear with respect to distance
of obstacle
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IR Analog sensor
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Modulate IR rays to avoid Ambient light effect :Astable
oscillator at frequency greater than 1KHz Transmitter IR led
ADC of Microcontroller
Peak ea Detector
High pass filter Cut-off filt , C t ff freq more than 300Hz
Receiver ece ve IR Photodiode
obstacle
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High-Pass filter : g
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Peak Detector:
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Errors involved in mouse movement :Forward error:
Forward errors begins when a mouse is either too close or too
far from the wall ahead
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Errors involved in mouse movement :Offset error :
Offset errors, which happens often, is caused by being too far
to the left or to the right as you pass through a cell
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Errors involved in mouse movement :Heading error:
Heading error is known as pointing at walls rather than down the
middle of the cell
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Commonly used Sensor arrangement :
Top Down Side Looking
SENSORS
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Top Down
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Side looking sensors :
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Initialize ADC
Select ADC channel
Start ADC
N0
ADC conversio n complete
Yes
Read ADC value
Stop
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Side lookingSample code for ADC conversion in AVR controllers :
Unsigned int left_adc; left_adc = adc(0xE0); unsigned int
adc(unsigned int temp) { ADMUX = temp; //selects ADC channel ADCSRA
|= 0x40; | 0 40 //starts ADC // t t while(conversion_not_over());
//waits till ADC conversion completes ADCSRA |= 0x10; // clears
ADIF flag return(ADCH); return(ADCH) // returns ADC result } int
conversion not over(void) conversion_not_over(void) { unsigned int
temp; temp = ADCSRA; p ; temp = temp & 0x10; // checks for ADIF
flag return(!temp); }
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Reducing error using PD controller :
Error
PD controller
Motors
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Error calculating:If wall is on both sides err = left adc right
adc left_adc right_adc; If err is +ve Mouse is near to left wall
and as a correction it has to move towards right wall If wall is
only on leftside err = left_adc reff_value; If err is +ve Mouse is
near to left wall and as a correction it has to move towards right
wall If wall is only on rightside err = right_adc reff_value; If
err is +ve Mouse is near to right wall and as a correction it has
to move towards left wall
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Implementing PD controller:
err_d = err err_past; adj = err * kp + err_d * kd ; kp is
proportional controller constant kd is derivative controller
constant The value of adj is used to either speed up or speed down
one of the wheel .www.raghu.co.nr
DC MotorDC Motors are small, inexpensive and powerful motors
used widely. These are widely used in robotics for their small size
and high energy out. t A typical DC motor operates at speeds that
are far too high speed to be useful, and torque that are far too
low. Gear reduction is the standard method by which a motor is made
useful . Gears reduce the speed of motor and increases the
torque
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Choosing a DC Motor gDC M t with G Motor ith Gear head h d
Operating voltage 12V Speed Depends on our application Some
available speeds in market 30 RPM 60 RPM 100 RPM 150 RPM 350 RPM
1000 RPM
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Drive basics of DC MotorRed wire Positive Negative Black wire
Negative Positive Direction of rotation Clock wise Anti clock
wise
Logic 1 0
Logic 0 1
Direction Clock Anti clock
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Bi-Direction Bi Di i control of DC M l f MotorH-Bridge H Bridge
Ckt using transistors for bidirectional driving of DC motor
Direction Clock wise Anti Clock wise Pulse to A and C B and D
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H-Bridges IC s H Bridges in ICs to reduce the drive circuit
complexity The most commonly used H-Bridges are L293D and 9 L298
L293D has maximum current rating of 600ma g L298 has maximum
current rating of 2A Both has 2 H-Bridges in them g These are
designed to drive inductive loads such as relays, solenoids pp Can
be used to drive 2 DC motors or 1 stepper motor
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PWM
STEPPER MOTORSTEPPER MOTOR is a brushless DC motor whose rotor
rotates in discrete angular increments when its stator windings are
g g energized in a programmed manner. Rotation occurs because of
magnetic interaction between rotor poles and poles of sequentially
energized stator windings. The rotor has no electrical windings,
but has salient and/or magnetized poles poles.
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4 Lead stepper
5 Lead stepper
6 Lead stepper
8 Lead stepper
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Full Step driving of Stepper Motor p g ppFull step wave
drive
4 1 0 0 0
3 0 1 0 0
2 0 0 1 0
1 0 0 0 1
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Full Step driving of Stepper Motor p g ppFull step 2 phases
active
4 1 0 0 1
3 1 1 0 0
2 0 1 1 0
1 0 0 1 1
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Half Step driving of stepper motor
4 1 1 0 0 0 0 0 1
3 0 1 1 1 0 0 0 0
2 0 0 0 1 1 1 0 0
1 0 0 0 0 0 1 1 1
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Choosing a Stepper motor12 V or 5 V operating voltage p g g 1.8
degree step 6 Lead 250 to 500 ma of current or Coil resistance of
20 ohms to 40 ohms Size and shape depends on application p In most
of the robotics cube shaped motors are preferred with frame size of
3.9 to 4 cm
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Commonly used ICs for driving Stepper motor IC s ULN2803 It has
8 channels It channel has maximum current rating of 500ma can be
used to drive 2 unipolar stepper motors L293d L297 & L298
UDN2916
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ULN2803
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Bi Polar driving of Stepper Motor g pp
A 1 0 0 1
B 1 1 0 0
C 0 1 1 0
D 0 0 1 1
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4 Lead stepper
5 Lead stepper
6 Lead stepper
8 Lead stepper
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Sample programfor(p=0;p
