Arduino PID Cotroller Ball Balance

Arduino PID Cotroller - Ball Balance

PID Controller - A proportional–integral–derivative controller (PID controller or three-term controller) is a control loop mechanism employing feedback that is widely used in industrial control systems and a variety of other applications requiring continuously modulated control.

Objective - To balance a ping-pong ball in the center of a beam using an arduino & communicating the results to a raspberry pi via a Bluetooth connection

Control System Breakdown

• P [Process] - The Ping-Pong Ball position
• S_p [Setpoint position] - Arduino programmed desired middle position
• F_p [Feedback position] - Ultrasonic Distance Sensor real position based on distance reading
• E [Error]- E = S_p - F_p

NOTE : Error is the difference between the desired ping-pong ball position (S_p) and the actual ping-pong ball position measured by the sensor (F_p).

• PID_p = K_p * E
• PID_i = PID_i + K_i * E

NOTE : The integral is based on the sum of error over time. So at t₀ the will be the integral constanct * the error, but this will grow and decrease gradually over time as the error changes.

• PID_d = K_d * (E_c - E_p /Δt)

NOTE : For the derivitave calculation we consider the ping-pong ball velocity. Which is the change in position (displacement) divided by the change in time. Δx/Δt, where Δx is the current Error (E_c) - the previous error (E_p).

Major Components

• Arduino Uno
• HC-05 Bluetooth Module
• Sg90 Micro Servo
• Ultrasonic Distance Sensor

Desired features

1. The Arduino should be able to provide the position of the ping-pong ball by reading the ultrasonic distance sensor.
2. The Arduino should be able to actuate the servo to pivot a balance beam left and right quickly.
3. The Arduino should be able to both receive commands from a raspberry pi & return results over a bluetooth connection using the hc-05 bluetooth module.

NOTE: The main result would be the time needed to balance the ping-pong ball.

4. The Control System should be able to balance the ping-pong ball from any starting point of the ping-pong ball along the balance beam and from any starting position of the balance beam (i.e. starting at an angle that is not 0 degrees; parallel to the base).
5. The Control System should be able to accept PID parameter values (K_p, K_i, K_d) sent to it from the Raspberry Pi.
6. Upon power up, the balance beam should have a default start position.
7. The Arduino should be able to set specific balance beam position/angles to start at (i.e. -20 degrees or 30 degrees).
8. The Arduino should have a general response message for verifying bluetooth communication with the Raspberry Pi. (i.e. Pi sends: "?", Arduino response: "!")