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Geonhee-LEE / mpc_ros

Differential Wheeled Mobile Robot - Nonlinear Model Predictive Control based on ROS
https://www.youtube.com/watch?v=5IqFGBmDGjU
Apache License 2.0
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What is the meaning of d and η in the path tracking model? Can you explain it? Thank you!!! #46

Open MandyZhang4869 opened 5 months ago

MandyZhang4869 commented 5 months ago

What is the meaning of d and η in the path tracking model? Can you explain it? Thank you!!!

MandyZhang4869 commented 5 months ago

and what is the meaning of θt* ？

Geonhee-LEE commented 5 months ago

Hi, @MandyZhang4869 Did you read the paper "Path Tracking with Nonlinear Model Predictive Control or Differential Drive Wheeled Robot" written by Korean? In this paper, the "d" term means the lateral error b/w robot's position and reference path's position and the "η" term means the angle error b/w robot's orientation and reference path's orientation. Finally, the "θt" term means time variable robot's orientation.

Thanks.

MandyZhang4869 commented 5 months ago

Having just read your paper, I still have a few questions. (I am relatively new to this field and still absorbing a lot of information, so my questions might be numerous and my understanding of your paper might be somewhat skewed.)

  1. According to your interpretation, should d and η in the figures be reversed? Additionally, I am a bit unsure about which points the error refers to. Is it the error between the point on the reference line at time t and the vehicle center B at time t?
  2. Based on the graphs presented in your video, is the green curve the reference trajectory for y given by the polynomial fitting curve g(xt)?
  3. Is xt in g(xt) the current position of the vehicle measured at time t? But if so, I am puzzled about what g(xt) is. It doesn't make sense to directly substitute the current position into the fitting curve of the reference trajectory, right?
  4. I am not quite clear about the right-hand side of the equation for dt+1. Especially what does vt·sinη·dt mean? Looking forward to your reply！！！Thank you very much！！！

[image: 1705902718191.png]

On Mon, Jan 22, 2024 at 8:21 AM Geonhee @.***> wrote:

Hi, @MandyZhang4869 https://github.com/MandyZhang4869 Did you read the paper "Path Tracking with Nonlinear Model Predictive Control or Differential Drive Wheeled Robot" written by Korean? In this paper, the "d" term means the lateral error b/w robot's position and reference path's position and the "η" term means the angle error b/w robot's orientation and reference path's orientation. Finally, the "θt" term means time variable robot's orientation.

Thanks.

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