PTZ Camera Tampering Correction Using IMUs

Sammanfattning

The Pan-Tilt-Zoom (PTZ) camera is a type of camera that covers large areas, up to 360°, in addition to zoom. Some of these cameras are susceptible to tampering, which means that an additional angle measurement feedback is necessary to detect such attempts. This thesis has evaluated the possibility of using MEMS-based IMUs to solve this problem. An advantage of such a system over other solutions, such as optical and magnetic encoders, is the decreased cost and complexity. The difficulty of using IMUs is that they are susceptible to drift in horizontal rotations in pan and require advanced signal processing to be reliable in demanding environments. Results showed that it was possible to correct tampering by using two IMUs, one on the fixed part of the camera and one on the moving part of the camera. It was then possible to track and correct tampering attempts with an average error of 1.0◦ in pan and 0.7◦ in tilt. The solution works when the camera is mounted on both fixed and moving objects. Notably, the solution proved to be much cheaper than alternative methods. Additionally, it proved to be robust against vibrations and shocks and within the performance requirements of the tested model. Additional methods were suggested for the system to track absolute orientation, for example, to be able to move the camera to pre-set positions. However, further work is needed to increase robustness in applications where the camera is mounted on objects that can rotate in roll or pitch.