Turtle_go

Turtlesim c++ package for drawing

This project has 3 Packages:

• turtle_go position control used to send cmd_vel to turtlesim and recive pose of the robot i implement this with oop to avoid working with nasty global variable
• turtle_sub_cmdvel* just used to subscribe for cmd_vel and print it out

Hardpoint coordinates

I used GeoGebra to determine hardpoints of letters like following

Record the slope from vector and length from segment for each line.

Terminal output

RQT Graph

PID configuration

Playing with configuration parameters should be done with caution, as they can cause instability.

/******************************************************************************
 * Configuration
 *******************************************************************************/
#define VEL                              0.5
#define SWITCHING_VEL                    2
#define POSE_TOLERANCE                   0.1
#define DISTANCE_TOLERANCE               0.0001
#define ANGLE_TOLERANCE                  0.0001
/* PID linear velocity output constrain */
#define PID_MIN_LINEAR_VEL               -5
#define PID_MAX_LINEAR_VEL               5
/* PID angular velocity output constrain */
#define PID_MIN_ANGULAR_VEL             -2
#define PID_MAX_ANGULAR_VEL              2
/* PID param of Distance  */
#define PID_LINEAR_KP                    10
#define PID_LINEAR_KI                    0
#define PID_LINEAR_KD                    8
/* PID param of Angle  */
#define PID_ANGLE_KP                     10
#define PID_ANGLE_KI                     0
#define PID_ANGLE_KD                     9

There are some problems I took into consideration while implementing PID, like output constraints and integral windup (output saturation).

Future work

• Make anther node with python (Matplotlib) to plot data in runtime
• Add derivative filter for PID
• Runtime configuration for PID parameters
• Implement discrete PID

Referance

• https://github.com/ros/ros_tutorials/tree/821a8ae33c6da1a70e21453392f6980380f670f8/turtlesim
• http://motion.cs.illinois.edu/RoboticSystems/CoordinateTransformations.html

turtle-draw