11 votes

How do the PID parameters (Kp, Ki, and Kd) affect the heading of a differential driving robot when they are increased individually?

Proportional term: this controls how quickly to turn the steering when the heading is not at the set value. A low P will lead to sluggish steering, reacting only slowly to set heading changes. It may ...
  • 1,021
6 votes

Inverse kinematics for differential robot knowing linear and angular velocities

Your linear velocity should be the average of both wheel values. Assuming there's some wheel radius of WHEEL_RADIUS, as you've stated, then you should get each ...
  • 15.1k
4 votes
Accepted

Adjusting the PWM frequency and duty cycle to achieve the desired angular velocity in differential drive robots

At first, I did not go trough your code to check for errors in the formulas but from a high level perspective this seems ok. Therefore, your position controller is fine. What you lack is a lowlevel ...
3 votes

Understanding differential drive

Your instincts are correct if you are talking about rotating both wheels forward (or reverse) with the same rotational speed. In that case, the robot would move linearly forward (or backward), just ...
  • 4,346
3 votes
Accepted

How to find kinematics of differential drive caster robot?

Kinematics of mobile robots For the figure on the left: I = Inertial frame; R = Robot frame; S = Steering frame; W = Wheel frame; $\beta$ = Steering angle; For the figure on the right: L = ...
3 votes
Accepted

How to perform odometry on an arduino for a differential wheeled robot?

I would add a few lines after you check that theta is between +/- 2pi: ...
  • 15.1k
3 votes
Accepted

Changing tank drive (differential) mode to single joystick drive mode

In order to do this, you need to have something on the robot that can intercept your "single joystick" signal from the remote control and translate it to left/right wheel speeds. Your arduino might ...
  • 10.9k
3 votes

Plotting location using wheel encoder data

A few things: I took a look at your data set. Did you make sure you used the time column correctly? The first entry is "1429481388546050050" without the decimal. To make it in seconds, it should be ...
  • 960
3 votes

Extended Kalman filtering for IMU and Encoder

EKF sensor fusion is achieved simply by feeding data streams from different sensors to the filter. So all you need to do is setup your implementation to accept both encoder and IMU data. This is ...
  • 1,276
2 votes

Plotting location using wheel encoder data

Thanks for the update. Now it looks like $x_c$ and $y_c$ denote the origin/starting position, and $\theta$ is positive, measured CCW from the positive x-axis. Now I am even more concerned about the ...
  • 15.1k
2 votes
Accepted

Understanding differential drive

The answer is very simple; Steer drive is what you know from a car where one motor powers both the wheels (either the front or the rear wheels) and then steering is achieved by turning the front ...
  • 136
2 votes

How do the PID parameters (Kp, Ki, and Kd) affect the heading of a differential driving robot when they are increased individually?

Andy's response is good, and he hits all of the important points but to fully understand PID control in the context of a differential drive robot, it might be useful to take a step back and consider ...
  • 926
2 votes

What is difference between 2 wheels and 4 wheels and tracked differential mobile base kinematics?

The short answer is that the equations/models for these different vehicle should be different but there is no value in using more accurate equations. All these equations are approximations that make ...
  • 4,255
2 votes
Accepted

Arduino for mobile robot

It depends what Arduino you are going to use. I don't think that you can use Arduino Nano/Micro for this because you will not have enough I/O and memory. You can use Arduino Mega (maybe UNO) but you ...
  • 161
2 votes

Advantage of Kalman filter in differential drive planar robot

It seem that your are missing some intuition about the function of a Kalman filter type filtering method. To a large degree the working principle of the Kalman filter is combining information from ...
2 votes

Motor acceleration and position with PID control

I believe the resource https://robotics.stackexchange.com/a/21571/6941 already pretty much answers your question. In essence, both the following approaches are valuable and can be combined together: ...
2 votes
Accepted

How to make my robot move parallel to edge of the table?

I can't use any line-following method. Actually, you are quite wrong, the way I understand the problem. It is a line-following. It is just that the line is not painted (like on the road). The line is ...
  • 301
2 votes

How to make my robot move parallel to edge of the table?

The problem you are describing is quite similar to line following from a controls perspective, there is a difference in how the line is detected. Line following robots use a wide variety of ways to ...
  • 6,497
2 votes

How to handle motor stall zones in differential drive point-forward go to goal algorithm?

For a similar problem (TT motors can't start the bot rolling on a carpet) I have been toying with the idea of setting up PID control for the angular velocity. If it stays stuck, the integral term ...
  • 1,236
2 votes

How to choose closest angle when crossing -180 degrees

This looks like a common angle wrapping mistake. I am assuming you're defining your angles between -180° ($-\pi$) to +180° ($\pi$). Let's say your current heading is -170°. And you desired heading is ...
  • 166
2 votes

Drive unicycle kinematics equations through the geometry

tl;dr: don't worry about it Your system really operates in continuous time, described by differential equations. It's a convenient, even necessary, approximation to use discrete time and difference ...
  • 1,236
2 votes
Accepted

Center line steering with differential drive

Based on the suggestion “look into PID”l controller” I did some more research on that for line following and that’s exactly what I was looking for. Funny in some ways my naive algorithm already uses a ...
1 vote
Accepted

Going from Spline to Differential Drive Command

If you have the path you want the robot to stay on, it sounds like you need Pure Pursuit. In this simple algorithm, you steer the robot to some look-ahead point on the path. The gist of it is ...
  • 5,465
1 vote
Accepted

How to drive mecanum wheels robot: code or algorithm

I've built one and added the code here: https://github.com/charlch/MecanumBot/blob/master/MecanumBot.ino The core of the maths is this: Firstly turn the 1000 to 2000 input into -1.0 to 1.0 ...
1 vote

how to implement autonomous navigation using lidar and hector?

http://wiki.ros.org/amcl You should try this and take a look at http://wiki.ros.org/turtlebot_navigation/Tutorials/Autonomously%20navigate%20in%20a%20known%20map It provides the code to use amcl and ...
  • 481
1 vote

Motor encoders randomly start counting backward, then go back to normal

What kind of motors are you using? Because the behaviour you describe makes me think of a brushless motor, due to the fact that you have a rotating magnetic field having the rotor spin. But in the ...
  • 66
1 vote

4 Wheel Differential Drive Robot with different speeds

Dynamic friction is always lower than static friction. If you are purposefully putting your wheels into a slip mode, then you are putting the wheels into a condition where they have less traction. ...
  • 15.1k
1 vote

ROS Gazebo Odometry Issue

this may be a bit late to answer, but i hope it may be of help for people learning ros in the future. First, in the URDF model, mu1 and ...
1 vote

calculating differential drive robot ICC position

OK, I'm going to work on the assumption that you are trying to calculate the Instantaneous Centre of Curvature, and that the values of $R$ and $\theta$ that you have been given are the distance from ...
  • 1,009
1 vote

How to find kinematics of differential drive caster robot?

Well, if it is truly a caster wheel with two differential drives, then I'd just assume that the castor is not a constraint at all! It's a freely rotating wheel that should just follow the direction ...

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