The Closed-loop Networked Control System Based On Internet And Visual Feedback

Networked control system (NCS) which is integrated with communication technology and control theory has drown wide attention for it's advantages in many aspects such as information sharing, remote controlling and cost controlling, and the NCS is the research focus in the field of Control. Many problems appear when the network was brought into NCS and the performance of the control system was degraded obviously, the most important one is the network-induced delay. The network-induced delay depends on the network chosen. Within all of the networks, the Internet is considered for its worldwide distribution and low access cost, but the network-induced delay of the Internet is the most complicate too, so it is necessary to do research on the NCS which is based on the Internet. There're two structures of the NCS: the direct structure and the hierarchy structure. The NCS with hierarchy structure is called teleoperation system, and the NCS with direct structure is just called NCS. This thesis studied both structures of the NCS base on the Internet and a 2-DOF manipulator.The first part of the work was about a manipulator teleoperation system based on the Internet, a camera was installed in the work area of the manipulator. On the one hand, an Image compression method was designed and the compression ratio reached 16:1 or higher. In order to monitor the work area, the images were compressed and sent through the Internet; the remote operator received the image date, decompressed and displayed it. On the other hand, a chess-type Calibration target was used to calibrate the camera, and then the image of the work area was processed to obtain the image coordinate of the manipulator's end-executor. With the image coordinate and the result of the camera calibration, the actual coordinate of the manipulator's end could be calculated. The coordinate was sent to the remote controller to compensate the coordinate of the track point. The manipulator has a semi-closed loop, and possesses some ability to act independently, and the whole-closed-loop was established with visual feedback and the method of Look-Move. The experiments of image processing and four-rose curve drawing were made, and the results were listed.The second part of the work was building an experimental Platform of NCS with direct structure based on the Internet and 2-DOF manipulator. The Motion Control Card of the manipulator was forced into open-loop by disable the closed-loop; then two remote controllers were designed and connected to the manipulator in order to control the joint motors. The local computer measure the angles of the joint motors with a sample period of 10ms, then sent them to the remote controller through the Internet. The remote controllers calculate the control values based on the feedback data and expecting values. The control values were sent to the local computer to control the joint motors. The experimental Platform realized the direct control of the manipulator and the measuring of the network-induced delay, and the experiment results were listed.