I. Introduction
With rapid development of computer science and image disposure and robot technology, more and more applications for robots were designed in many areas such as military affairs, astronautics, industry, agriculture and medicine in last decades. In such areas, the medical robot technology is one of the most thriving and the fastest-developing research fields [1]. Surgical robots have been developed to assist surgeons in performing a wide range of procedures, such as laparoscopic surgery [2]–[4], prosthetic joint replacement surgery [5], [6], neurosurgery [7], and telesurgery[8], [9]. The health care system in the United States costs 16% of gross domestic product [10]. Medical robotic products are under current development in order to improve the quality of our health care system by: 1) inventing new diagnostic capabilities, 2) developing new therapies, and 3) creating technologies that improve the overall quality and cost effectiveness of our health care delivery system [11].