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DESKBOT UPDATE 3

Scene Segmentation and Object Detection


The robot has to know its environment before taking an action, a sensor is required is to perceive the environment and know what things exist. In our case, we use a 2D camera to know where and how the objects and the robots are positioned. We use Mask R-CNN to perform instance segmentation and object detection or use YOLO for object detection. 
Mask R-CNN is divided into two modules, first, it estimates the regions where the objects can exist on the input image. Second, based on the initial estimation it identifies the class of the object and generates a mask in the pixel level. In the initial step, the RPN (Residual Pooling Network) scans all FPN (Feature Pyramid Network) in a top-bottom approach and estimates where the objects exist on the input image. Once the estimation is done a bounding box is assigned to the anchor (anchors are a set of boxes with predefined locations). RPN helps in the anchor to decide where in the feature map an object and bounding box should be located. In most scenarios after processing the downsized, therefore we need to up-sample the so that the objects in the original image and features are not messed around. After estimating the location of the objects in the first stage, in the second stage, specific areas of the feature map are scanned and generate objects classes, bounding boxes and masks. Below is an illustration on Mask RCNN structure. As mentioned below in Figure 3. we have two stages and how they process the image.
Simple Understanding of Mask RCNN - Xiang Zhang - Medium


                Figure 3 Illustration of Mask RCNN Structure


YOLO

The YOLO framework (You Only Look Once), deals with object detection in a different way. It takes the entire image in a single instance and predicts the bounding box coordinates and class probabilities for these boxes. The biggest advantage of using YOLO is its superb speed – it’s incredibly fast and can process 45 frames per second. YOLO also understands generalized object representation. This is one of the best algorithms for object detection and has shown a comparatively similar performance to the R-CNN algorithms. 

Here is a link that shows all the classes that YOLO can detect by default: https://github.com/pjreddie/darknet/blob/1e729804f61c8627eb257fba8b83f74e04945db7/data/9k.names

Examples of few images: 






Next update it will be streamlined to detect the classes required for our project such as pens, books eraser etc. 

References:- https://pjreddie.com/darknet/yolo/
  1. https://pjreddie.com/darknet/yolo/
  2. https://github.com/pjreddie/darknet/blob/1e729804f61c8627eb257fba8b83f74e04945db7/data/9k.names
  3. https://medium.com/@jonathan_hui/real-time-object-detection-with-yolo-yolov2-28b1b93e2088

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