Medical robotics

Medical robots are robots that assist surgeons to access surgical areas convincingly during an operation using more precise and less invasive methods. They usually are tele-manipulators; a surgeon operates the tele-manipulator at one side, and the end-effector tool executes tasks at the other side. Medical robots revolutionize traditional medical treatments into advance new healthcare techniques and theory of medical science and it expand conventional robotic applications and bring new challenges to robotics significantly. The study on medical robotics is multidisciplinary. To develop vital technologies for design and operations of medical robots, it is essential to combine robotics with medical science, biomechanics, mechanics, machine theory, materials science, mathematics, computers graphics, and information technology. Developing new advanced robots for numerous healthcare applications is an emerging research trend in the field of robotics globally. The advancement of medical robots has led to a number of commercialized robotic systems for many applications such as surgical operations, planning and simulation, minimal damage precise positioning, noninvasive diagnosis and detection, and new types of surgery treatments. This special issue aims at gathering original research articles as well as review articles that will support and stimulate continuous effort to understand the theories and enabling technologies of medical robotics, as well as the related applications. A total of 10 articles have been accepted after a strict peer review process. From the article type, two articles are review articles and eight articles are research articles. Among them, six articles distribute in the topics relating rehabilitation robot and two articles in the topics relating minimally invasive surgical robot, reflecting the main concerns in medical robot currently. Robot in prosthodontics and orthodontics and tele-nanomanipulation system for nano-level probe operation are also concerned with two articles, respectively.

In the area of rehabilitation robot, in the article “Design and evaluation of a motor imagery electroencephalogram-controlled robot system,” Bao-guo Xu et al. design an brain–computer interface (BCI)–based online robot control system, which is made up of electroencephalogram (EEG) amplifier, acquisition and experimental platform, feature extraction algorithm based on discrete wavelet transform (DWT) and autoregressive model (AR), linear discriminant analysis (LDA) classifier, robot control board, and Rhino XR-1 robot. The performance of the system has been tested by 30 participants, and satisfactory results are achieved with an average error rate of 8.5%. Moreover, the advantage of the feature extraction method is further validated by the Graz dataset for BCI competition 2003, and error rate of 10.0% is obtained. This method provides a useful way for the research of BCI system and lays a foundation for BCI-based robotic upper extremity rehabilitation therapy. The article “A multi-posture locomotor training device with force-field control” by Jian-feng Sui et al. introduces a multi-posture locomotor training device with a closed-loop control scheme based on joint-angle feedback, which is able to overcome various difficulties resulting from mechanical vibration and the weight of trainer to achieve higher accuracy trajectory. A series of trajectory accuracy experiments in various angles demonstrate a satisfactory performance of the active-constrained mode. The article “Modeling and simulation to muscle strength training of lower limbs rehabilitation robots” by Ke-Yi Wang et al. proposes a training method of muscle strength based on closed-force loop according to the construction of lower limb rehabilitation robot and training pattern. The relationship between output acting force of robot and wires’ tension is analyzed. It indicates the validity of force planning of lower limb rehabilitation robot. The tracing performance of force control of simple wire has met the request of rehabilitation training. The article “Identification of motion trend of lower limbs based on near-infrared spectroscopic technology” by Chun-guang Li et al. detects hemoglobin information in cerebral cortex simultaneously during the process of upstairs, downstairs, sit-down, and standup movements. The statistical results in the premotor cortices in the right hemisphere region confirm that motion trend of two lower limbs could be identified. And the statistical results in the premotor cortices in the left hemisphere region could be used for distinguishing upstairs and downstairs movements. This is beneficial to providing a favorite reference movement for a walking-assisted device. The article “Robotic neurorehabilitation system design for stroke patients” by Bao-guo Xu et al. proposes a new approach to offer recovery training for stroke patients. The feasibility of integrating robotic rehabilitation with motor imagery–based BCI is investigated. Pattern recognition algorithm for upper limb movement imagination EEG is realized. Mental imagination of upper limb movement is detected to trigger the Barrett WAM Arm to manipulate the impaired upper limb to perform rehabilitation training. Fuzzy-based proportional–derivative (PD) position control strategy is used to control the WAM Arm to move along predefined trajectories for passive recovery exercise. The article “Recent development of rehabilitation robots” by Zhi-qin Qian and Zhu-ming Bi conducts a critical review on the development of rehabilitation robots to identify the limitations of existing studies and clarify some promising research directions. The demands of assistive technologies for elderly and people with disabilities are discussed, the issues involved in the development of rehabilitation robots are investigated, some representative robots in this field by leading research institutes are introduced, and a few of critical challenges in developing advanced rehabilitation robots are identified.

In the area of minimally invasive surgical robot, the article “Dimensional optimization of a minimally invasive surgical robot system based on NSGA-II algorithm” by Wei Wang et al. presents the mechanical design of an abdominal minimally invasive surgical manipulator. From the perspective of the optimization, two evaluation indexes are proposed to maximize the motion range of the mechanical arms’ remote center of motion point and to minimize the interference possibility among the mechanical arms. The Non-dominated Sorting Genetic Algorithm-II (NSGA-II) is employed to calculate the length of the kinematics links of the manipulator. The optimal dimension of the mechanical arms is selected based on the actual requirements. The optimization methodology outlined in this article can be used and extended in the design process of the similar minimally invasive surgical robot. The article “Design and experimental study of joint torque balance mechanism of seed implantation articulated robot” by Yong-de Zhang et al. establishes mathematical models of multi-needle puncture prostate using nonlinear spring-damper model. The displacement simulation for prostate is performed based on Adams/motion module, and simulation results indicate that the multi-needle puncture mechanism could reduce prostate displacement in the Y/Z direction. A revolute–revolute–translational (RRT) type prostate seed implantation robot with three-dimensional (3D) transrectal ultrasonography (TRUS) navigation is designed. An elastic balance mechanism is designed to realize the complete balance of cantilever weight. Static drive torque simulation of 2R tandem cantilever structure is performed.

In the area of robot for prosthodontics and orthodontics, the article “A review on robot in prosthodontics and orthodontics” by Jin-gang Jiang et al. conducts a critical review on the development of application of robot in prosthodontics and orthodontics to identify the limitations of existing studies and clarify some promising research directions in this field. The main problems in its development are analyzed, the development trend is foreseen, and the future research is discussed.

In the area of tele-nanomanipulation system for nano-level probe operation, the article “OpenCV-based nanomanipulation information extraction and the probe operation in scanning electron microscopy” by Dong-jie Li et al. designs a classifier of nanowires and probe with OpenCV. The probe and nanowires in scanning electron microscopy (SEM) images can be automatically identified and located by the system. The operator employs the operation strategies and makes the virtual probe conduct expected movement, and then an optimal path can be obtained. The results show that the corresponding method has achieved the expected effect.