Comparison study on motion characteristics of three 2-DOF pointing devices

Two degree-of-freedom (DOF) manipulators have been widely applied in pointing devices. Besides the commonly used gimbal platforms, two different kinds of parallel platforms base on parallel manipulators are presented as real applications in this paper. In a situation, a pointing device acquires and tracks a remote target via optical sensors amounted on the device. As the authors' recent research, there are image distortions caused by deflected camera axis while the pointing device changing its attitudes. The paper refers the phenomena to the self-motion characteristics as the 2-DOF platforms rotate around the fixed platform axis. Basic image distortion principles of the three platforms are illustrated and discussed. Relationship between the self-motion and revolution are analyzed via the graphic approach and simulated on the software. Results indicate that these different phenomena are due to the different inherent characters of the platform's freedom lines and freedom disks. Conclusions revealed in this paper would help the engineers with the type selections and applications, especially for the remote virtual reality devices which can provide realistic images for the human eyes. This work will facilitate the image processing and improve the measuring accuracy for the pointing devices.