MECHANICAL DESIGN: OVERHAUL

“SAVIOUR THAT REDEFINES TERRITORY”

Robot Chassis

Grippers

Lifting and

Lowering

Mechanism

Participants:

1. B S Sachin 3. Akshay G H

2. Kartik Nayak 4. Kishore Kumar

College: BMS College of Engineering, Bangalore.

CHASSIS DESIGN

A metal chassis and a wooden chassis of

dimensions 18cm x 12.5cm is used for our design. The

lower side of metal chassis houses four wheels which is

used for locomotion and the upper side of metal

chassis contains required electronic circuits PIC18

development board and L293D H-bridge driver board.

The upper chassis houses two motors which are used

for lifting mechanism.

MECHANISMS USED:

Traversal Mechanism.

Lifting and Lowering Mechanism

Grasping Mechanism

TRAVERSAL MECHANISM:

COMPONENTS USED:

2 sets of wheels of diameter 10.25cm

4 DC motors of 60rpm/12V

2 H-bridge L293D ICs

PIC18 Microcontroller

WORKING

The required signals are selected through the

switches and sent to a PIC microcontroller

near the switches. The Information is encoded

and sent to an on board PIC microcontroller

through UART. This reduces the number of

wires from 8 to 3. The three wires are 12V,

UART and Ground. Along with reduction in

number of wires to be used, this method of

encoding information allows to have a better

locomotion than when the motors are

connected to the switch directly. The

Locomotion is controlled by the switches and

the microcontroller controls the motors

accordingly by varying the Pulse Width

Modulation (PWM). The signal from Microcontroller is increased to 12V or 0V based on the logic

levels by using H-bridge. The connections of motors are fitted with a spring in order to have better

suspension in rough terrain. The various values of PWM of the motors are given in the following

diagram.

LIFTING AND LOWERING MECHANISM:

COMPONENTS USED:

2 DC motors: 10rpm/12V and 30rpm/12V

1 H-bridge

Pulley

Nylon Thread

WORKING:

This mechanism requires two DC motors. The 10rpm

motor is placed at the rear end of the bot while the

30rpm motor is placed at the middle of the chassis.

The 10rpm motor controls the motion of the shaft

mounted on it and has a pulley placed on it. The 30rpm motor controls the length of the nylon

thread that is extend over the shaft of 10rpm motor and pulley. The lower end of the thread

contains the grasping mechanism. In the below, diagram, the brown colour represents the

30rpm and 10 rpm motors, orange represents the chassis, brown represents the shaft, blue

represents the pulley and green represents the motors used for locomotion.

The below diagram shows the working mechanism of 10rpm motors. The position of the shaft

can be changed with the 10 rpm motors.

The below diagram shows the working mechanism of the 30rpm motor. The length of the thread

can be changed using the 30 rpm motors.

GRASPING MECHANISM:

COMPONENTS USED:

1 SERVO motor 1Kg Torque

Gears

WORKING:

The grasping mechanism is used to grasp the victims or the bridge and is placed at the end of the

nylon thread across the pulley. A Servo motor is used to control the gears of the plastic hands so

as to grasp the victim or the bridge and also release whenever required. The servo motor gets

the required PWM signal i.e. 1ms to 2ms signals from the PIC18 microcontroller. The below

diagram shows the working of the grasping mechanism.