Are self-balancing robots old? No! not at all for all the enthusiast available out there.It is amazing to see these bot struggling to balance. Actually, I have already made this bot once but that was without PID. This version has a PID embedded in it with less coding complexity.
1. DC Motors or better be servo motors or better be stepper motors
3. 0.1uF X 4 Ceramic Capacitors
4. Bluetooth Module HC05
5. 0.1 uF Ceramic Capacitor
6. Hot Glue
7. Arduino (Any version of your hobby box)
8. GY-521 Gyro+Accelerometer
Step 1: What Is This Actually ?
I 'll be straight. You have a stick. You are holding it vertically on your palm. It starts falling on one side and you move your hand to that direction to maintain its balance. This is done to maintain the center of gravity within the vertical line.The top and bottom of the stick are the limit points. If COG lies outside the line joining this line then it will lose balance. To maintain its balance it what we are gonna do.
Step 2: Building
I have used a breadboard to assemble the circuitry. You are free to choose yours. I am using ceramic capacitors to filter out the noise from DC Motors. You must attach two ceramic capacitors across the 5v and 36V terminals of L293D for more noise filter. This is necessary as the noise may turn off your MPU6050 or HC05 or may even reset your Arduino.
I have used HC05 to upload my sketches wirelessly. Serial Monitor can also be accessed wirelessly.
If you are using servos having low RPM then use larger wheels. If you are using DC motors with high RPM then you can use smaller wheels.
Step 3: Make Your Robot Frame
Apply Glue to bot motors. Then use the Acrylic sheet to join them. I have painted them white.
Step 4: Add All the Electronics.
Mount the weight on top if possible. Mount your Gyro along the axis to motors. This is done because linear acceleration is least at that point.
Step 5: PID Tuning.
1. Set P = 0, I = 0, D = 0.
2. The increase P until your bot starts oscillating. It may oscillate wildly or even swiftly. It should be between these two.
3. Increase D to reduce the oscillations.
4. Increase I to increase its response. Higher is the I value, quicker is the response time when it's out of balance. Larger the I value, less is the inclination limit.
Step 6: Source Code
Working of the Bot
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It appears that Github script and Instructable.com are rivals. Some spaces are missing in the code. Please take care of it.
The only reason why my bot is 98% stable and not 99% is because of backlash error. 100% is not possible since not balance bot can stand still. For a better stability use gripped rubber wheels. Mine had plane surface rubber wheels. Gripped with cut type wheel will increase your stability since stability depends not only on an algorithm or MPU readings but also on better physical characteristics of the robot.
Here is the link if you want for formatted code Code