Mechanical Design ID-21

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.