ROS packages for Dynamic Time Warping

Dynamic Time Warping (DTW) is a method to align two sequences under certain constraints. For instance, two trajectories that are very similar but one of them performed in a longer time. The alignment should be is such way that minimizes the distance between these two sequences. Here I have done DTW between two-time series with python. I found a good c++ library for Fast Dynamic Time Warping and I developed my wrapper to make a ROS package for that. Here you can download my code at GitHub.

The number of possible warping paths through the grid is exponentially explosive. The image is taken from [1].

A good wrapping function should have following characteristics:

  • monotonicity: The alignment path does not go back in “time” index.

    The image is taken from [1]

  • continuity: The alignment path does not jump in “time” index.

    The image is taken from [1]

  • boundary conditions: The alignment path starts at the bottom left and ends at the top right.

    The image is taken from [1].

  • warping window: A good alignment path is unlikely to wander too far from the diagonal.

    The image is taken from [1].

  • slope constraint: The alignment path should not be too steep or too shallow.

    The image is taken from [1].

  • References: [1]

 

References: [1]

 

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