Automated Wheelchair
description
Transcript of Automated Wheelchair
Automated WheelchairAutomated WheelchairDone By
HARIHARAN LKARTHIKEYAN S P
NARESH SLAKSHMI V
Guided ByMr. RATHINAM ASenior lecturer
SRM Engg. College
IntroductionMechanical designSelection of motorsCircuit designSoftwareConclusionFuture scope
Battery 2
Battery 1
MG
wheel
chair
supply processor
plank
Control circuit
M
40 cm
80 c
m
Proper Weight balance
Dead weight = 50 kg
Plank size: 80 x 40 cm
gear
Gears
Back wheel setup
Front wheel setup
Formulae Used/
Calculation
Braking
Spur Gear
Bevel Gear
Worm Gear
V = 3.14xDxNw/60 Pw =2x3.14xNwxTw/60 Tw = 9.81xWxRwhere
V => Linear Velocity Pw => Power of MotorTw => Torque of the
Wheel ShaftD => Diameter of
wheel Nw => Speed of wheel
Radius of the wheel Shaft Rw = 9mm
Maximum Weight that it can withstand Wmax
= 17.18/(0.9x10-2x9.81) = 194.59 kg (approx 200 kg)
Speed of wheel (Nw) = 50rpm
Diameter of wheel (D) = 32cm
Linear Velocity (V) = 3.14 x 32 x 10-2 x 50 / 60 = 0.837m/s (3Kmph)
Power of Motor (Pw) = 120W
Speed of the motor shaft =3000rpm
Diameter of Motor Shaft(d) = 9mm
Maximum Torque in Motor shaft = 0.382Nm
Assuming 75% efficiency for the worm wheel gear, a gear ratio of 1:60,
Torque of the Wheel Shaft Tw = 60 x 0.382 x 0.75 = 17.18Nm
Worm Gear -Serves Dual Purpose
Property:Torque improvement
Irreversibility
Instantaneous braking
Reasons for selecting PMDC Reasons for selecting Servo Motor
Motor Ratings Vehicle Testing
Reasons for selecting PMDC
Efficiency of PMDC > Efficiency of DC Motor
Smaller size of PMDC than DC for same Power
Less voltage => Less noise
Less Radio or TV interference
Lower manufacturing cost
Reasons for selecting Servo Motor
Low inertia due to the fact that armature mass is less
Fast torque response
Step change in armature voltage or current produces quick change in position or speed of the rotor
PMDC
Voltage: 24V
Current: 7A
Power Rating: 120W
Speed: 3000rpm
SERVO MOTOR
Voltage: 24V
Current: 1.25A
Torque: 1.5KgCm
Loading ConditionVoltage Applied
(V)
Current Drawn
(A)
Wheel Speed(RPM)
No Load Reading
During Straight
run
24
4.5
60
During Turning
24
5.5
50
Load Reading
During Straight
run
24
7
50
During Turning
24
9
40
H-Bridge Control of Motor
Control Box
Block Diagram
8085 Based Relay Control Circuit
Forward Direction
Supply (positive)
relay3 – motor – relay4
Supply (negative)
Reverse Direction
Supply (positive)
relay1 – motor – relay2
Supply (negative)
Start/Stop
Forward
Reverse
Left Right
HornHead lamp
Control box
Port C8085
Microprocessor
Port A & B
Control circuit
8255interfaced
withprocessor
Control Logic
Algorithm
Flow Chart
Port C (Input port) Operation
C7 C6 C5 C4 C3 C2 C1 C0
HEX
CODE
Stop 1 (01) H
Forward 1 (02) H
Reverse 1 (04) H
Left 1 (08) H
Right 1 (10) H
Step1:Configure Peripheral Programmable Interface (PPI-8255) as the following:
Port A => Output PortPort B => Output PortPort C => Input Port
Step2: Initialize Stack PointerStep3: Begin scanning the commands issued by the user.Step4: Check for the position of the start/stop switch
If in Start position Begin scanning other inputsElse Go to Step1
Step5: Check whether Forward Key is pressed.If pressed Go to Forward subroutineElse Go to next step
Step6: Check whether Reverse Key is pressed.If pressed Go to Reverse subroutineElse Go to next step
Step7: Check whether Left Key is pressed. If pressed Go to Left subroutineElse Go to next step
Step8: Check whether Right Key is pressedIf pressed Go to Right subroutineElse Go to next step
Step9: Go to Step3 for scanning inputs again
Start
Initialize stackpointer
Is forwardkey pressed?
Is reversekey pressed?
Is left keypressed?
Is right keypressed?
Is mainswitch off?
Stop
Switch ‘OFF’ fwd.relays and switch ‘ON’reverse relays
Switch ‘OFF’ reverserelays and switch‘ON’ fwd. relays
Check keydebounce
Check keydebounce
‘ON’ leftrelaysmomenta-rily
‘ON’ rightrelaysmomentarily
Y
Y
Y
Y
Y
N
N
N
N
N
Note:
Main Switch
=>ON
Other Operations carried out
Some salient features about our vehicle are
User friendly.Proper direction control (automatic steering system).Additional manual steering.Designed to withstand a weight of a normal human being.Designed to run at an average speed of 3kmph.Compact design (hind wheel set up is fitted underneath the plank).A horn facility (as in any normal vehicle).
Some of the additional features that can be implemented are
Replace Microprocessor by Microcontroller.Remote control to operate from anywhere.Predefined motion to facilitate parking etc.A light dependent headlight (for easy propagation in the dark as well) and Obstacle detector.Replace batteries by a Solar Panel.