ECE497 Project - Object Detection w/ DNN
Team members: [Paul Wilda, Leela Pakanati]
I'm using the following template to grade. Each slot is 10 points. 0 = Missing, 5=OK, 10=Wow!!
00 Executive Summary 00 Installation Instructions 00 User Instructions 00 Highlights 00 Theory of Operation 00 Work Breakdown 00 Future Work 00 Conclusions 00 Demo 00 Late Comments: I'm looking forward to seeing this. Score: 10/100
We are using tensor flow and Open-CV to detect items in the frame of a web camera. The camera is mounted onto a tilt pan kit to allow us to track the objects in frame as well. Due to the intensive nature of the object detection, we are using a local computation server to process the image and find the objects within it. The computation server returns a processed image and error vector which the Pi coverts to a control vector. It can then display the processed image and adjust its angle to keep the tracked object in the middle of the frame. In order to dramatically decrease the complexity of the project, we would have liked to preform all the processing on the Pi as well however we were unable to get a reasonable response time with either the Pi or the Beagle Bone. The Raspberry Pi takes at least 3 seconds per image to process and the BeagleBone Black at least 5 seconds.
In the spirit of small build, big execution, we created an enclosure for our project using mdf. We CNC'd two pieces that were then glued together, sanded and painted. A notch was cut into the back for the cables to access the Raspberry Pi that was mounted on the underside. The Pi was mounted using 4x 3M plastic standoffs and some 3M screws. The tilt pan kit was mounted on the top piece and a hole was drilled through to allow the servo motor cables access to the Pi.
Below you can see pictures of the assembly:
Bottom of the enclosure
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Theory of Operation
The camera sends the image to the Raspberry Pi over usb. The Pi then sends the image to the web server. The web server processes the image, finds the nearest person it has the highest confidence for, and returns an error vector to the pi of the distance between the identified object and the center of the frame. Using a PID control loop, this error vector is processed by the Pi and converted into a control vector. Finally, the control vector is then turned into PWM signals that are sent to each servo.
This whole process takes anywhere from 100-130 ms. Our greatest bottleneck in this process is the time it take to transfer the image to and from the web server. Despite the delays inherent to file transfer over the internet, this is still significantly faster than trying to do all the processing on the Pi or the Beagle bone. Due to these hardware limitations of the Pi and Beagle bone it took nearly 3 sec on the Pi, and 6 sec on the Beagle to process a single image.
In an effort to further optimize our system we used both cores on the Pi to parallelize some of the tasks. Currently, the image transfer and display is handled on one core, while the control loop runs on the other. This was done to help preserve the timing of the control loop as well as take some load off off the core that was handling the image.
- Getting OpenCV on Pi/Beaglebone (10/28)
- Testing Pi vs Beaglebone operation (10/29)
- Image sending and receiving (11/5)
- Web server configuration (11/5)
- Servo and tilt pan kit assembly (11/10)
- Control loop and tuning for servos (11/14)
- Enclosure design and construction (11/16)
- Documentation (11/19)
- Creating our own libraries to train our model on would be a very interesting addition to this project. This would allow us to detect and recognize individuals and only track certain people.
- Making the tilt pan kit more robust would allow us to mount a nicer camera to the system and would significantly improve the image quality as well as the recognition accuracy.
- Since we are mostly only tracking a single image it would be interesting to look into other object detection algorithms. About 40ms of the delay we are experiencing is from the processing of the image. If, instead of analyzing the whole image to find all the objects, we only searched blobs of the image we could significantly decrease the amount of computation needed. This could perhaps even allow us to run all the computation on the Pi/Beagle
This was a very interesting project overall that introduced a lot of new concepts that neither of us had any experience with. We ran into some difficulties and road blocks largely due to the hardware limitation of the Pi, but this was a good starting point and it gives us a lot to improve on if we decide to continue to improve the system.