Visual observer for multi-link mechanical system

Abstract Commonly contact-type sensors are used in mechanical systems. The state variables of the system, which can not be measured by contact-type sensors should be estimated by an observer or a differentiator. However, some mechanical systems can not be measured by contact-type sensors to avoid friction. In other cases, contact-type sensors may not be mounted spatially. Inevitably a visual measurement system is necessary. In this paper, we propose a visual observer for multi-link mechanical systems. With the proposed observer, the state estimation can be achieved by using one camera while the plant model and camera parameters are known. Moreover we can estimate the state vector in the same way by using two, three or more cameras. Therefore it can be applied even if the occlusion problem occurs.