A Novel Marker Tracking Method Based on Extended Kalman Filter for Multi-Camera Optical Tracking Systems

In the Robotics Assisted Surgical System, the position and orientation of the surgical tools must be estimated precisely in real time. In order to decrease the possibility of the occlusion of line-of-sight, the multi-camera optical tracking system prototype is developed. Based on this hardware platform, a novel multi-marker tracking algorithm using Extended Kalman Filter (EKF) for multi-camera tracking systems is proposed, which makes full use of the redundant information of multi-camera. The marker target movement model can benefit from multiple views by performing a special EKF updating 3D state by 2D projection observations on the image planes. This method has the advantage to estimate the movement of a 3D point more accurately by directly using the actual observations from multiple views rather than the non-continuous and possibly error-prone 3D reconstructed point. The experimental results indicate that the presented tracking algorithm is able to track the 3D trajectories of multiple targets simultaneously, and the estimated 3D positions by EKF are in agreement with the actual measurements by stereo triangulation.

I. Introduction

During the surgical operation for the spinal injury or fractures, the surgeons have experienced the technical difficulties to locate the surgical tools precisely [1]. It is caused by the unstable human handling and the long time operation fatigue. on the other hand, this operation demands high safety and accurate positioning because the spinal area is distributed with major blood vessels and nerves. In order to help surgeons improve tool insertion accuracy in spinal surgery, it is of importance to take advantage of the emerging techniques such as positioning, navigation and robotics [2], [3]. The Robotics Assisted Surgical System (RASS) is a promising technique for the spinal surgery. In most procedures of the spinal surgery, there are many delicate operations involving inserting the tools accurately and precisely in a confined workspace. Although there are several positioning techniques, the optical tracking technique is a suitable choice to provide continuous and real-time position and orientation in the RASS. Additionally, the optical tracking system can also be applied to the rehabilitation robotic system to obtain the accurate motion information of stroke patient [4], [5]. Fig. 1. Spine surgical robot system