Automated Wheelchair Done By HARIHARAN L KARTHIKEYAN S P NARESH S LAKSHMI V Guided By Mr. RATHINAM A Senior lecturer SRM Engg. College
Introduction Mechanical design Selection of motors Circuit design Software Conclusion Future scope
Battery 2 Battery 1 M G wheel chair supplyprocessor plank Control circuit M 40 cm 80 cm 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 = 9.81xWxR where V => Linear Velocity Pw => Power of Motor Tw => Torque of the Wheel Shaft D => 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) = kg (approx 200 kg) Speed of wheel (Nw)= 50rpm Diameter of wheel (D)= 32cm Linear Velocity (V)= 3.14 x 32 x 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 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 Condition Voltage Applied (V) Current Drawn (A) Wheel Speed (RPM) No Load Reading During Straight run During Turning Load Reading During Straight run During Turning
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 Horn Head lamp
Control box Port C 8085 Microprocessor Port A & B Control circuit 8255 interfaced with processor
Control Logic Algorithm Flow Chart
Step1:Configure Peripheral Programmable Interface (PPI-8255) as the following: Port A => Output Port Port B => Output Port Port C => Input Port Step2: Initialize Stack Pointer Step3: 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 inputs Else Go to Step1 Step5: Check whether Forward Key is pressed. If pressed Go to Forward subroutine Else Go to next step
Step6: Check whether Reverse Key is pressed. If pressed Go to Reverse subroutine Else Go to next step Step7: Check whether Left Key is pressed. If pressed Go to Left subroutine Else Go to next step Step8: Check whether Right Key is pressed If pressed Go to Right subroutine Else Go to next step Step9: Go to Step3 for scanning inputs again
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.