Creating PID Tuning Graphs
From wikidb
Contents
Overview
This page documents a Python program designed to graph the first few seconds of power applied to the motors and robot speed. It is used to help calibrate PID parameters. I didn't know how to configure rqt_plot to display snapshots.
Message Additions to the Motor Controller
Code
A "wheels" message of type Float64MultiArray is published in the setMotorPower function. It has five elements.
- data[0]: time is seconds since the motor controller was started.
- data[1]: wheel 0 speed in m/sec
- data[2]: percent of full power applied to wheel 0
- data[3]: wheel 1 speed
- data[4]: wheel 1 power
Wheel published global declaration
ros::Publisher wheel_pub_; ros::Time beginning_time_;
Publisher initialization in the main.
wheel_pub_ = n.advertise<std_msgs::Float64MultiArray>("wheels", 100);
Initializing beginning time in InitMotorPower
beginning_time_ = ros::Time::now();
Publishing a wheel status message in setMotorPower
std_msgs::Float64MultiArray wheel_data; wheel_data.data.clear(); ros::Time odom_time(odom_.header.stamp.sec, odom_.header.stamp.nsec); ros::Duration elapsed_time = odom_time - beginning_time_; wheel_data.data.push_back(elapsed_time.toSec()); wheel_data.data.push_back(wheel0_speed); wheel_data.data.push_back(power_wheel0_); wheel_data.data.push_back(wheel1_speed); wheel_data.data.push_back(power_wheel1_); wheel_pub_.publish(wheel_data);
Message Reference
General
- General Messages Primitive Data Types in Messages
- Common Messages ROS Specific Messages
- Standard Messages Primitive Data Messages
Float Array Specific
- 64 bit float array messages Message Detail
- Array message layout
- Array message example
Time
The Python Plot Code
Plot termination Criteria
There are two termination criteria 1) cnt-c and 2) time. After one of the criteria is met, the graph is drawn.
Plotly Graphing Tools
Installing
sudo apt-get install python-pip sudo pip install plotly
Authentication
See authentication file in
~/.plotly/.credentials
Coding
Working around a bug in iplot. Change it to plot.