This post is about understanding how a self driving deep learning network decides to steer the wheel.
NVIDIA published a very interesting paper(https://arxiv.org/pdf/1604.07316.pdf), that describes how a deep learning network can be trained to steer a wheel, given a 200x66 RGB image from the front of a car.
This repository(https://github.com/SullyChen/Nvidia-Autopilot-TensorFlow) shared
a Tensorflow implementation of the network described in the paper, and
(thankfully!) a dataset of image / steering angles collected from a
human driving a car.
The dataset is quite small, and there are much larger datasets available like in the udacity challenge.
However
it is great for quickly experimenting with these kind of networks, and
visualizing when the network is overfitting is also interesting.
I ported the code to Keras, trained a (very over-fitting) network based on the NVIDIA paper, and made visualizations.
I
think that if eventually this kind of a network will find use in a real
world self driving car, being able to debug it and understand its
output will be crucial.
Otherwise the first time the network decides
to make a very wrong turn, critics will say that this is just a black
box we don’t understand, and it should be replaced!
First attempt : Treating the network as a black box - occlusion maps
The
first thing we will try, won’t require any knowledge about the network,
and in fact we won’t peak inside the network, just look at the output.
We”l
create an occlusion map for a given image, where we take many windows
in the image, mask them out, run the network, and see how the regressed
angle changed.
If the angle changed a lot - that window contains information that was important for the network decision.
We then can assign each window a score based on how the angle changed!
We
need to take many windows, with different sizes - since we don’t know
in advance the sizes of important features in the image.
Now we can make nice effects like filtering the occlusion map, and displaying the focused area on top of a blurred image:
链接(需翻墙)：
http://jacobcv.blogspot.jp/2016/10/visualizations-for-regressing-wheel.html
代码链接：
https://github.com/jacobgil/keras-steering-angle-visualizations
原文链接：
http://weibo.com/5501429448/EeBRKc9pl?ref=collection&type=comment