PID implementation Turtlesim

Goal to Goal

Task

Model the motion from initial pose ( ) to goal pose ( ) in the following 3 parts as shown in figure and use PID controllers separately on the 3 parts:

1. Turn by
2. Move straight for
3. Turn by

turtlesim_pid3.mp4

Usage

Clone this repository in catkin source directory

cd ~/catkin_ws/src
git clone https://github.com/ABD-01/ros_pid.git

Build the package in catkin workspace

cd ~/catkin_ws && catkin_make

To start ROS Master

roscore

To start a turtlesim simulator

rosrun turtlesim turtlesim_node

Run the PID simulator with command line arguments for final pose.

rosrun ros_pid turtlesim_pid.py [-h] -x X -y Y -t THETA

Input final pose

optional arguments:
  -h, --help            show this help message and exit
  -x X, --x X           Final x position
  -y Y, --y Y           Final y position
  -t THETA, --theta THETA
                        Final angle (in degrees)

For eg:

rosrun ros_pid turtlesim_pid.py -x 1 -y 1 -t 120

Start the rqt graph for visualization

rqt_plot /plot/error/data[0] /plot/error/data[1]

Tuning coefficients Kp, Ki, Kd

Custom coefficient values and loop rate can be passed while creating the PID class instance.

  pid = PID(
      final_pose,
      Krot1=K(4, 0, 2),
      Ktrans=K(0.5, 0.001, 0.02),
      Krot2=K(1, 0.0, 0.01),
      loop_rate=10
  )

Path Planning

Task

Same as above but to be done in single step rather than 3 individual steps.

Method

Used Hermite curve to generate a trajectory for the turtle given the initial and final conditions.

Usage

Run the PID simulator with command line arguments for final pose.

rosrun ros_pid turtlesim_cubic.py [-h] -x X -y Y -t THETA

Input final pose

optional arguments:
  -h, --help            show this help message and exit
  -x X, --x X           Final x position
  -y Y, --y Y           Final y position
  -t THETA, --theta THETA
                        Final angle (in degrees)

For eg:

rosrun ros_pid turtlesim_cubic.py -x 1 -y 1 -t 120

Trajectory_hermite.mp4