The aim of this project was to make a bot that can sketch any given curve on a plane surface.
There is no handy product in the market to sketch or plot curves on large scale canvas.
The previous version of this bot-Curve Sketching Bot (Srishti 2018) traverses using differential chassis. It was disadvantageous since it was slow and had to change its orientation every time to move along the curve.
Hence we came up with the idea of making an advanced version of the bot that is faster, moves in a locked orientation, and with other possible advanced features.
- 5x 58mm plastic omni-wheel.
- 3x 300rpm DC motors.
- 2x Rotary Encoders.
- 1x Arduino Mega.
- 2x Cytron motor drivers.
- 1x Gyroscope(MPU 9250).
- 1X 5V Regulator(7805).
- 1x 9V Regulator(7809).
- 2x Linear Bearings.
- 2x switches.
- 3d printed parts.
- 1x Full Bread board.
- Jumper wires.
- Aluminium square channels+plates.
- 1x 11.1V 2200mAh LiPo battery.
- 1x Pen.
- 1x Spring.
It is an equilateral triangle-shaped, 3 wheeled Omni drive bot that can be easily manufactured. Omni drives are really fast, it can move in any direction without changing its orientation i.e., in locked orientation and the wheels always stay in contact with the ground even if the surface is uneven.
The chassis is made up of square aluminum channels. It reduces the overall weight of the bot and hence reducing the load on motors.
Three Johnson 300rpm motors are used, to get the required torque. They are coupled with Omni wheels using 3D printed couplers and the shaft of the motor is passed through radial ball bearing. The bearing block is mounted on the chassis holding the wheel assembly and chassis together. The three wheel assemblies are mounted on the three vertices of the triangular chassis i.e., at 120° to each other.
Two encoders are mounted mutually perpendicular to each other on the triangular chassis with their axes intersecting at the centroid of the chassis. And two free wheels are attached to these encoders to get feedback from the 'x' and 'y' axes. This encoder assembly is mounted on the chassis using a hinge so that all five wheels can have proper contact with the surface.
It is a 3D printed cylindrical holder that is placed at the centroid of the chassis. It can hold only one pen at a time and the size of the holder is fixed and hence the pen diameter is fixed.
All electronic components are placed on the top of the chassis with cardboard as the base to reduce weight and to avoid short circuits as aluminum is an electric conductor.
- All actuations are done with appropriate velocities which are calculated by dividing the curve into small distances.
- Feedbacks are obtained from encoders and MPU9250.
- PID mechanism is the control loop mechanism here. It changes the velocities according to the obtained feedback.
- This process is done in a loop until the curve is fully plotted.
Arduino Mega 2560 R3 is used as the microcontroller board.
- MPU9250 is used to get the angular motion feedback of the bot. It is directly connected to SDA/SCL sockets of the Arduino Mega board through male headers as wires interrupt serial communication.
- Two Rotary Encoders are used to get linear motion feedback from x and y axes.
- Jhonson 300rpm motors are used for traversal actuation which is controlled by Cytron motor driver.
- IC LM7809 and IC LM7805 for converting 11.1V DC to 9V DC and 5V DC respectively
- Two switches are used-One for motor drivers and another for the rest of the bot.
- 11.1V LiPo battery is used as the power source.
- Motors are directly powered from the battery.
- Arduino Mega board is powered with 9V converted output of the battery.
- Encoders are powered with 5V converted output of the battery.
- MPU9250 is powered with 5V Vcc of Arduino.
| Components | Cost(INR) |
|---|---|
| Wheels | 5*450 |
| Linear Bearing | 2*100 |
| Gyroscope(MPU 9250) | 1*450 |
| Motors | 3*500 |
| Motor Drive | 2*2500 |
| Arduino Mega | 1*650 |
| Bread Board | 1*100 |
| 11.1V LiPo Battery | 1*750 |
| Aluminium square channels | 1*100 |
| Total | 11,000 |
It can be used to plot any continuous curve on plane canvas of any scale.
- It cannot be used to plot discontinuous curves.
- The pen size is fixed.
- It can plot only in one color.
- A servo motor can be attached to the pen holder to make it possible for the bot to plot discontinuous curves.
- Pen holder design can be changed to hold multiple pens to make the bot plot in multiple colors.
- The code can be improved to plot images using G-code.
- Ruchika Atul Guntewar
- Sanjeev Krishnan R.
- Vijai Kumar R.
- Ujjwal Baranwal
- Vedant Neekhra
https://www.google.com/amp/s/amp.livescience.com/40103-accelerometer-vs-gyroscope.html