A Testbed for Vision-Based Networked Control Systems

With the availability of low-latency wireless communication and low-delay video communication solutions, vision-based networked control systems (NCS) become feasible. In this paper, we describe an NCS testbed which is suitable for the evaluation of the interplay of computer vision algorithms, network protocols and control algorithms under a delay constraint. The system comprises an inverted pendulum which is monitored by a video camera. The h.264-encoded video is sent over a network to an image processing computer. This computer extracts the angle of inclination of the pendulum from the decoded video and sends it over a wireless link to the pendulum. The pendulum uses the angle in a control algorithm to keep itself in a vertical position. We provide a detailed description of the system including the control algorithm and the image processing algorithms, and analyse the latency contributors of the system. The build instructions and source code of the testbed are publicly available. As the testbed is based on standard low-priced components, it is particularly suitable for educational purposes.