Disinfectant Spraying Robot

Abhimanyu Khadka, Asim Maharjan, Saju Khakurel
Funded by Nepal Academy of Science and Technology (NAST) during Covid-19

The bot is a purely remote-controlled device. With Arduino as the main processing unit of the robot, it offers varieties of controls and motion to the robot. Our mobile application facilitates users with full control over the robot so that the user can effortlessly move the robot and spray disinfectant with just a touch finger. Also, the wireless connection makes it super easy to operate too.
The whole system of the robot can be divided into two parts. One is the base part and the other is the robot’s arm, the upper part. The base part of the robot consists of 4 dc motors and wheels, which are responsible for the movement of the robot as a whole. This part is a 24V supply using two 12V lipo batteries in series.
The upper part of the robot is responsible for the movement of the nozzle for spraying. It has 2 degree freedom of movement and operate using two motors, a stepper, and a servo. Each of the motors is responsible for a degree of movement and operates in a 12V power supply from a lead acid battery. All the components in the robot can be used simultaneously.

The robot uses a simple differential drive for movement and is equipped with four 24V DC motors, with each motor controlling the rotation of a single wheel. The robot uses the Arduino Mega 2560 microcontroller for controlling the motor drivers and Bluetooth signals.
The DC Motors are controlled using an H-bridge motor driver L298N which enables the motors to be operated both clockwise and counterclockwise. The motor driver is given a PWM input from Arduino according to which the speed and direction of the motors are controlled.
The 2-axis arm for spraying the disinfectant is made from wood and is controlled by a stepper motor, NEMA 17 for horizontal rotation and a servo motor MG995, for vertical movement. The stepper motor is controlled by a stepper driver A4988 which allows for precise movement of the arm. We also attached two proximity sensors to control the movement of the stepper motor.
A 12 V DC water pump is used for spraying the disinfectant. The water pump is made controllable by using a simple on/off relay switch.

The robot is also equipped with two proximity sensors which are mounted on the front and the back of the robot. The proximity sensors are used to detect obstacles in the path of the robot and signal the controller if any obstacle is detected .
The robot also has a Raspberry Pi Model 3B+ which is used primarily for video streaming. The video is captured through a Raspberry Pi Camera, which the raspberry pi broadcasts through WiFi to the mobile app.
The robot is controlled by a mobile app. The mobile app uses Bluetooth to establish communication with the robot. For this, the robot comes equipped with the HC-05 Bluetooth module. The mobile app was created using Flutter and comes with an interface for controlling the robot as well as for viewing the video that is captured by the robot.
The power supply for the robot is divided into two parts. One part is for powering the DC motors of the robot while the other part powers all the other components. The motors are isolated from the other components as the motors were found to be very noisy and it affected the operation of other components of the robot. The isolation is done using optocouplers.