From MAE/ECE 148 - Introduction to Autonomous Vehicles
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Project Overview

Our project was to integrate OpenCV into donkeycar in order to try and improve training time and robustness of the model. We used OpenCV to pre-process images in order to extract edges and highlight the white and yellow lanes. We wanted to see if using those images as a combined 3-D image (edges, white lane, yellow lane) would improve training time and robustness of the model compared to the original default donkeycar model which trained using RGB images.

Team Members

  • Cyrus Shen - ECE
  • Chenfeng Wu - ECE
  • Maximilian Stadler - CSE (UCSD Extension)
  • Isabella Franco - MAE


Mechanical Design

Our mechanical design is relatively simple. We designed a baseplate to be fitted onto the four mounting points originally meant to fix the chassis. A large slot in the middle gives us the necessary space for the cables. All the other things are fixed on the plate using Velcro. In retrospective, it would have been better to use screws drilled through the baseplate to do so. Inertia effects are large in the corners causing the parts to come loose. This is a problem, especially on the outdoor track.

To keep our recorded images valid, we fixed the camera right from the beginning with four screws. The camera design itself is rather simple but provides sufficient housing for the lens. We used two iterations as the first camera mount's inclination was too flat which lead to images mainly focusing on the parts of the track right in front of the car. Therefore, we changed the inclination in the second iteration leading to - at least by human inspection - better-looking recordings.

Design images are shown in the following.


3D model of baseplate
baseplate dimensions

Camera Mount

3D model of camera mount used

Car Circuitry

The circuity follows the descriptions given in class. As we do not have additional hardware, no further changes were necessary. For unsafe situations, a wireless relay acts as an emergency switch by deactivating the PWM outputs. Therefore, set outputs are not active, i.e. not sent to the motors for example, which leads to the desired effect of stopping the car without resetting anything in the running driving lop on the Jetson. A LED-indicator shows the status of the car: a red light indicates a stopped car while a blue light indicates that the car is in the 'driving' state. Since we use the default circuitry, we do not give further details but only append our layout for an overview.

circuit layout of car

Aspect Ratios and Cropping

The original configuration suggested the recording of images with the size of 160x120 pixels resulting in a 4 by 3 aspect ratio and doubling the resolution for the outdoor setting, i.e. to 320x240. The used camera is itself a 2 MP camera being capable of recording FHD images. Thus its native resolution is 16 by 9. To allow for easy comparison, we decided to record indoor and outdoor images at the same resolution. We furthermore tried different aspect ratios to find how much information, especially in the corners, is lost due to cropping. We modified the framework such that only the height and the aspect ratio are specified in the configuration files. The image width is derived. We tested 1 by 1, 4 by 3, and 16 by 9. We concluded that the native wide angle resolution gives us the most information in the corners, which seemed to be prone to errors in the beginning anyway.

   # newly added flags for aspect ratio and image sizes
   IMAGE_W = None
   IMAGE_H = 144

track / aspect ratio 1x1 4x3 16x9
Team6 1x1 1.jpg
Team6 4x3 1.jpg
Team6 16x9 1.jpg
Team6 1x1 2.jpg
Team6 4x3 2.jpg
Team6 16x9 2.jpg

Integrating OpenCV

The Donkeycar-Framework is coded in a relatively rigid fashion. Many hard-coded sections and in-line definitions make any customization hard. Our goal was to compare the original models with models using visual primitives as priors, namely edges and lane segmentations. While these primitives can be easily computed using OpenCV, coding had to be done carefully to keep the code modular and allow an easy comparison of the original version without any code changes and the OpenCV-based models. Furthermore, to allow flexible modifications, our code was kept parametric which resulted in several additions to config.py allowing for customizable preprocessing.

Our code-changes support different "modes". Each mode implements the abstract _OpenCvPreProcessor. Depending on the specification in the config file, the corresponding preprocessor is initialized and used. More details about the different modes are given in the next section.

   class _OpenCvPreProcessor:
       Abstract class of image processor
       Implement framework of shutdown and run function as required by 
       Donkey car framework.
       def __init__(self, cfg):
           self.cfg = cfg
       def shutdown(self):
       def run(self, image_arr):
           raise NotImplementedError
   class OpenCvPreProcessor:
       preprocessor-manager defining kind of pre-processing based 
       on a string-argument loads corresponding class in init
       def __init__(self, cfg):
           self.cfg = cfg
           if cfg.CV_PREPROCESSOR_TYPE == 'canny':
               assert cfg.CV_TARGET_IMAGE_DEPTH == 1
               self.processor = OpenCvCanny(cfg)
           elif cfg.CV_PREPROCESSOR_TYPE == 'segmentation':
               assert cfg.CV_TARGET_IMAGE_DEPTH == 1
               self.processor = OpenCvColorSegmentation(cfg)
           elif cfg.CV_PREPROCESSOR_TYPE == 'combined':
               assert cfg.CV_TARGET_IMAGE_DEPTH == 3
               self.processor = OpenCvCannyAndSegmentation(cfg)
           elif cfg.CV_PREPROCESSOR_TYPE == 'combined_with_gray':
               assert cfg.CV_TARGET_IMAGE_DEPTH == 3
               self.processor = OpenCvCannySegmentationAndGray(cfg)
               raise NotImplementedError
       def run(self, image_arr):
           if image_arr is None:
               return None
           processed_image = self.processor.run(image_arr)
           return processed_image
       def shutdown(self):

Newly Added Configuration Settings

To achieve easy changes to our cv-framework, we kept all parameters modular and added corresponding flags to the configuration. The newly added configuration possibilites are given here.

   USE_OPENCV = False # boolean flag for whether images are preprocessed using opencv
   CV_STORE = False  # whether to store raw-image or pre-processed image (TRUE == store cv-processed image)
   CV_PREPROCESSOR_TYPE = 'combined_with_gray' # describes type of pre-processing (canny | segmentation | combined | combined_with_gray)
   CV_STORE_INF = False # whether to store "inference-input" during ai-mode for testing
   CV_COLOR_MODE = 'indoor'  # mode for color segmentation (indoor | outdoor)
   # WHITE
   CV_WHITE_LOWER_IN = [140, 140, 140]
   CV_WHITE_UPPER_IN = [255, 255, 255]
   CV_YELLOW_LOWER_IN = [25, 110, 30]
   CV_YELLOW_UPPER_IN = [70, 160, 70]
   # WHITE
   CV_WHITE_LOWER_OUT = [170, 170, 170]
   CV_WHITE_UPPER_OUT = [255, 255, 255]  
   CV_YELLOW_LOWER_OUT = [5, 100, 70]
   CV_YELLOW_UPPER_OUT = [20, 180, 170]
   CV_CANNY_MIN = 50
   CV_CANNY_MAX = 125
   CV_ROI_TYPE = 'crop'                # type of roi-operation (crop | mask | None)
   CV_GAUSSIAN_SIGMA = 0.0  # might be unnecessary at all, if 0 is being used

Changes to manage.py

To include the preprocessor during running the car, we mainly modified the sections of the code where image preprocessing already takes place (cropping and normalization). We introduced an if-else branch to include the new pipeline. Furthermore, we changed several other lines of code to allow storing preprocessed images or the inference input for debugging purposes.

   if "coral" in model_type:
       inf_input = 'cam/image_array'
   # new OPENCV-flag: insert preprocessor between cropping and normalize
   # therefore splitting the normalize_and_crop function was necessary
   # default-code in else-branch
   elif cfg.USE_OPENCV:
       from opencv.preprocessor import OpenCvPreProcessor
       if cfg.CV_ROI_TYPE == 'crop':
                 outputs=['cam/image_array_cv'], threaded=False)
                 outputs=['cam/image_array_cv'], threaded=False)
       inf_input = 'cam/normalized/cropped'
       inf_input = 'cam/normalized/cropped'

Changes to train.py (mainly in donkeycar.utils)

Also, changes in the training-loop were necesary to include the preprocessor on loading the training images. Herefore, mainly changes in the load_scaled_image functino were necessary - besides several small changes in the training loop.

   def load_scaled_image_arr(filename, cfg, cv_preprocessor=None):
       load an image from the filename, and use the cfg to resize if needed
       also apply cropping and normalize
       import donkeycar as dk
           img = Image.open(filename)
           if img.height != cfg.IMAGE_H or img.width != cfg.IMAGE_W:
               img = img.resize((cfg.IMAGE_W, cfg.IMAGE_H))
           img_arr = np.array(img)
           # new OPENCV-flag
           # run preprocessor before loading training image_arr
           if cfg.USE_OPENCV:
               img_arr = crop(img_arr, cfg)
               img_arr = cv_preprocessor.run(img_arr)
               img_arr = normalize(img_arr)
               img_arr = normalize_and_crop(img_arr, cfg)
           croppedImgH = img_arr.shape[0]
           croppedImgW = img_arr.shape[1]
           # account for canny image
           if cfg.CV_TARGET_IMAGE_DEPTH == 1:
               img_arr = img_arr.reshape(croppedImgH, croppedImgW, 1)
           elif img_arr.shape[2] == 3 and cfg.IMAGE_DEPTH == 1:
               img_arr = dk.utils.rgb2gray(img_arr).reshape(croppedImgH, croppedImgW, 1) 
       except Exception as e:
           print('failed to load image:', filename)
           img_arr = None
       return img_arr

Lane Finding with OpenCV

HSL Colors for Lane Detection

In order to single out the white and yellow lanes from the rest of the image, we used HSL color-space to threshold the image for the colors white and yellow. The RGB image taken by the camera was converted to HSL using OpenCV's COLOR_RGB2HLS and then thresholded so that only white and yellow colors in the image were kept.

HSL description

white lange segmentation orange lange segmentation final segmentation result
Segmented lane white screenshot 10.12.2019.png Segmented lane orange screenshot 10.12.2019.png Result screenshot 10.12.2019 segmentation.png

Canny Edge Detection

To outline the lanes, we used OpenCV's canny function which shows edges in an image.

Result screenshot 10.12.2019 canny.png

Combined 3-D image

We combined the white, yellow, and canny edge images into a 3-D image and trained on that instead of the original RGB image.

combined combined with grey-scale
Result screenshot 10.12.2019 combined.png Result screenshot 10.12.2019 combined with gray.png
canny edges (blue)
white segmentation (green)
yellow segmentation (red)

gray-scale image (blue)
canny edges (green)
white and yellow segmentation (pink)



In order to compare our OpenCV model to the current default model, we trained both models on the same images. For the indoor models, we trained separate models on 1000, 5000, 10000, 20000, and 30000 clockwise training images from the indoor track. For the outdoor models, we only trained on 1000, 5000, and 10000 clockwise training images from the outdoor track.

None of the clockwise models worked when driving counterclockwise.

For outdoor training images, we tried to keep the car in the middle of the track as best as possible (following the orange lines) during image collection.

We tested each model based on the following criteria:

  1. Training time
  2. Local Angle completion of 3 clockwise laps on the respective track
  3. Autonomous completion of 3 clockwise laps on the respective track
  4. Able to drive when environment is brighter or darker than the trained images?

A brief video comparing our 5000 OpenCV model to the 5000 default model

Indoor Track Model Results

For the 1000, 5000, and 10000 indoor images, they were taken with the Makerspace doors closed so the images of the track in front of the door were darker. When we tried testing those 3 models with the Makerspace doors open, brightening the area of the track in front of the doors, none of the 3 default models could pass that part of the track. However, the OpenCV 10000 model could pass that part of the track most of the time which is significantly better than the default 10000 model which passed it 0 times. This is a good sign that our OpenCV model works better than the default under brighter track conditions.

At 20000 and 30000 train images, both default and OpenCV models could pass that part of the track which could be due to overfitting.

Example of model failing with doors below:

Our OpenCV models trained on average 1 minute faster than the default models and could run autonomously on 5000 train images while the default model required 10000 training images.


Criteria \ Images Trained 1000 5000 10000 20000 30000
Training Time (min:sec) 02:23 06:10 09:35 N/A N/A
Local Angle Completion Χ Χ
Autonomous Completion Χ Χ
Brighter Environment Χ Χ Χ


Criteria \ Images Trained 1000 5000 10000 20000 30000
Training Time (min:sec) 01:24 05:20 08:21 N/A N/A
Local Angle Completion Χ
Autonomous Completion Χ
Brighter Environment Χ Χ

Outdoor Track Model Results

Our OpenCV outdoor models performed significantly better than the default outdoor models. The 5000 and 10000 OpenCV models completed the 3 laps around the outdoor track while the 5000 and 10000 default models could not finish half of the track, failing on the curves.

During the third week of class, we trained a default outdoor model with ~20000 images and it successfully completed 3 laps on the track (so we know that the default model can be used on the outdoor track). With our OpenCV preprocessing, we significantly reduce the amount of training images needed from ~20000 to 5000 at minimum.

In order to test criteria 4, we also tested the model at 5pm when the sun was setting so the track was darker than the train images used. Unfortunately, none of the models worked when the track was darker although our OpenCV models did get farther on the track than the default models.


Criteria \ Images Trained 1000 5000 10000
Training Time (min:sec) 00:55 04:19 06:56
Local Angle Completion Χ Χ
Autonomous Completion Χ Χ Χ
Darker Environment Χ Χ Χ


Criteria \ Images Trained 1000 5000 10000
Training Time (min:sec) 01:19 03:45 6:30
Local Angle Completion Χ
Autonomous Completion Χ
Darker Environment Χ Χ Χ

Software Code

OpenCv image processing code.

Modified donkeycar framework.

Project Video

OpenCV image processing allows our car to drive autonomously with as little as 5k training images. Watch video here