Reusable PID Controller in C

Summary

This project features a reusable PID (Proportional-Integral-Derivative) controller implemented in C. It is designed using a structure that enables multiple instances to be reused effectively. This framework allows for testing code pieces in a C simulation environment, particularly suitable for control and embedded software engineering applications.

Project Overview

The PID controller is a crucial component in control systems, widely used for its simplicity and effectiveness. This implementation focuses on creating a reusable and modular architecture. The project involves:

• Object Model: Simulates an object of mass $m = 10 , \text{kg}$, subject to viscous friction with a coefficient $k = 0.5 , \text{N}\cdot\text{s/m}$, and pushed by a force $F$.
• PID Controller: Implements a PID control loop that adjusts the control input to achieve desired object positioning.

Architecture

The architecture of this program includes:

• Model of an Object:

  • Mass ($m$): 10 kg
  • Viscous friction coefficient ($k$): 0.5 N·s/m
  • Force ($F$): Limited to [-100, 100] N

• PID Controller:

  • Includes a filtered derivative for the derivative term
  • Command saturation and rate limiter
  • Anti-windup technique through back-calculation

Mathematical Model

The model of the object is defined by the differential equation:

$$ m \cdot \frac{d^2z}{dt^2} = F - k \cdot \frac{dz}{dt} $$

Where:

• $z$ is the position of the object in meters
• $v = \frac{dz}{dt}$ is the velocity of the object

Simulation

The simulation environment is implemented in C and tests two slightly different PIDs controlling the position of two identical objects. The main function performs the following tasks:

• Creates structures for two PIDs and objects
• Iterates 1200 times (equivalent to 120 seconds of simulation time, with each step representing 0.1 seconds)
• Generates setpoints: 100 m and 50 m for the first 60 seconds, then changes to 200 m and 150 m
• Executes PID_Step using the previous step's $z$ value
• Executes Object_Step using the command from PID_Step

The simulation results are demonstrated graphically, showcasing the effectiveness of this approach.

Features

• Reusable Architecture: Utilize structures to create multiple PIDs for different control tasks.
• Efficient Simulation: Run simulations with detailed output to analyze PID performance.
• Comprehensive Control: Incorporates derivative filtering, command saturation, rate limiting, and anti-windup.

Usage

To use this PID controller framework:

1. Clone the repository: git clone https://github.com/simorxb/PID-C-Struct
2. Navigate to the directory: cd PID-C-Struct
3. Compile the code using a C compiler: gcc -o pid_simulation main.c
4. Run the simulation: ./pid_simulation

Author

Simone Bertoni

For more information and projects, visit Simone Bertoni Lab.

Contact

For further inquiries and discussions, connect on LinkedIn.

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This project is a practical implementation of PID control theory, emphasizing flexibility and reusability in embedded systems development. It serves as a foundation for experimenting with and understanding control algorithms in a structured environment.