Dimensional optimisation and an inverse kinematic solution method of a safety-enhanced remote centre of motion manipulator.

BACKGROUND: With the expansion of minimally invasive surgery (MIS) applications in surgery, the remote centre of motion (RCM) manipulator requires a more flexible workspace to meet different operation requirements. Thus, the mechanical structure and motion control of the RCM manipulator play important roles. METHODS: A multi-objective genetic algorithm was exploited to maximise the kinematic performance and obtain a compact structure of the RCM manipulator. An inverse kinematic solution method is proposed to meet task accuracy and kinematic singularity avoidance constraints for safety motion control. RESULTS: Simulation results demonstrate that there are significant improvements in the reachable workspace inside the abdominal cavity, the flexibility of the workspace, kinematic performance, and compactness of the RCM manipulator. Experiments verify the feasibility of the prototype and the validity of the proposed inverse kinematic solution method. CONCLUSIONS: This enhances the adaptability and safety of the RCM manipulator and provides potential prospects for MIS application.

Preoperative planning method based on a MOPSO algorithm for robot-assisted cholecystectomy.

PURPOSE: Surgical robots have multiple manipulators with complex mechanisms and need to work in a narrow space in the patient's body. Therefore, for robot-assisted minimally invasive surgery (RMIS), it is very important to develop a reasonable preoperative planning before surgery. METHODS: A preoperative planning method based on the premise of no collision between surgical instruments and endoscope, an evaluation index with visibility, operability and hand-eye coordination was proposed in this paper. To consider the balance relationship of global optimization index, a multi-objective particle swarm optimization (MOPSO) algorithm was adopted. Because the physical characteristics of each patient are different, the method can determine the selectable area of the incision based on the relevant knowledge of anatomy. RESULTS: The simulation taking the cholecystectomy as an example was performed on a minimally invasive surgical robotic system. The analysis result showed that the proposed preoperative planning method based on the MOPSO could provide surgeons with a reasonable and effective preoperative planning. CONCLUSIONS: The proposed preoperative planning method based on the MOPSO is suitable for patients with different physical characteristics, and can provide a guidance for surgeons and effectively reduce the preoperative planning time and improve the safety and efficiency of the operation, especially a novice surgeon who lacks robot-assisted minimally invasive surgery experience.

Heading tracking control with an adaptive hybrid control for under actuated underwater glider.

The underwater glider changes its direction to follow the preset path in the horizontal plane only by flapping its vertical rudder. Heading tracking control plays the core role in the navigation process. To deal with non-linear flow disturbance and saturation in actuator, a new hybrid heading tracking control algorithm was presented, which integrated an adaptive fuzzy incremental PID (AFIPID) and an anti-windup (AW) compensator to improve the adaptability and robustness of underwater glider's heading control. The dynamic model of an underwater glider named as Petrel-II 200 was modeled to serve as a controlled plant. The proposed heading tracking control algorithm was described in detail, where the rudder angle, a control quantum to the controlled plant were calculated to get forces and moments required for the desired glider heading. A closed loop motion control system with desired heading angle as input and actual heading angle output was put forward, which included the dynamic model of the Petrel-II 200 and the given heading tracking control algorithm. The simulations followed three typical mathematical signals and the experimental tests were carried out by taking in the dynamic parameters of the controlled plant. And the effectiveness of the proposed control algorithm was assessed and verified.

External force estimation and implementation in robotically assisted minimally invasive surgery.

BACKGROUND: Robotically assisted minimally invasive surgery can offer many benefits over open surgery and laparoscopic minimally invasive surgery. However, currently, there is no force sensing and force feedback. METHODS: This research was implemented using the da Vinci research kit. An external force estimation and implementation method was proposed based on dynamics and motor currents. The dynamics of the Patient Side Manipulator was modeled. The dynamic model was linearly parameterized. The estimation principle of external force was derived. The dynamic parameters were experimentally identified using a least squares method. RESULTS: Several experiments including dynamic parameter identification, joint torque estimation, and external force estimation were performed. The results showed that the proposed method could implement force estimation without using a force sensor. CONCLUSIONS: The force estimation method was proposed and implemented and experimental results showed the method worked and was feasible. This method could be used for force sensing in minimally invasive surgical robotics in the future.

A fuzzy neural network sliding mode controller for vibration suppression in robotically assisted minimally invasive surgery.

BACKGROUND: It is very important for robotically assisted minimally invasive surgery to achieve a high-precision and smooth motion control. However, the surgical instrument tip will exhibit vibration caused by nonlinear friction and unmodeled dynamics, especially when the surgical robot system is attempting low-speed, fine motion. METHODS: A fuzzy neural network sliding mode controller (FNNSMC) is proposed to suppress vibration of the surgical robotic system. Nonlinear friction and modeling uncertainties are compensated by a Stribeck model, a radial basis function (RBF) neural network and a fuzzy system, respectively. RESULTS: Simulations and experiments were performed on a 3 degree-of-freedom (DOF) minimally invasive surgical robot. The results demonstrate that the FNNSMC is effective and can suppress vibrations at the surgical instrument tip. CONCLUSIONS: The proposed FNNSMC can provide a robust performance and suppress the vibrations at the surgical instrument tip, which can enhance the quality and security of surgical procedures.

A zero phase adaptive fuzzy Kalman filter for physiological tremor suppression in robotically assisted minimally invasive surgery.

BACKGROUND: Hand physiological tremor of surgeons can cause vibration at the surgical instrument tip, which may make it difficult for the surgeon to perform fine manipulations of tissue, needles, and sutures. METHODS: A zero phase adaptive fuzzy Kalman filter (ZPAFKF) is proposed to suppress hand tremor and vibration of a robotic surgical system. The involuntary motion can be reduced by adding a compensating signal that has the same magnitude and frequency but opposite phase with the tremor signal. RESULTS: Simulations and experiments using different filters were performed. Results show that the proposed filter can avoid the loss of useful motion information and time delay, and better suppress minor and varying tremor. CONCLUSIONS: The ZPAFKF can provide less error, preferred accuracy, better tremor estimation, and more desirable compensation performance, to suppress hand tremor and decrease vibration at the surgical instrument tip. Copyright © 2016 John Wiley & Sons, Ltd.

Force sensing of multiple-DOF cable-driven instruments for minimally invasive robotic surgery.

BACKGROUND: Force sensing for robotic surgery is limited by the size of the instrument, friction and sterilization requirements. This paper presents a force-sensing instrument to avoid these restrictions. METHODS: Operating forces were calculated according to cable tension. Mathematical models of the force-sensing system were established. A force-sensing instrument was designed and fabricated. A signal collection and processing system was constructed. RESULTS: The presented approach can avoid the constraints of space limits, sterilization requirements and friction introduced by the transmission parts behind the instrument wrist. Test results showed that the developed instrument has a 0.03 N signal noise, a 0.05 N drift, a 0.04 N resolution and a maximum error of 0.4 N. The validation experiment indicated that the operating and grasping forces can be effectively sensed. CONCLUSIONS: The developed force-sensing system can be used in minimally invasive robotic surgery to construct a force-feedback system.

Control design and implementation of a novel master-slave surgery robot system, MicroHand A.

BACKGROUND: Compared with conventional minimally invasive surgery and open surgery, robotic-assisted minimally invasive surgery can overcome or eliminate drawbacks caused by operator restrictions, motion limitation by the trocar and the image system, such as fatigue, trembling, low precision, constrained degree-of-freedom, poor hand-eye coordination and restricted surgical vision. In this paper, a novel partly tendon-driven master-slave robot system is proposed to assist minimally invasive surgery and a master-slave control architecture is developed for abdominal surgical operations. METHODS: A novel master-slave surgery robot system named MicroHand A has been developed. A kinematic analysis of master and slave manipulators was conducted, based on screw theory and vector loop equation. The relationships of the tendon-driven multi-DOF surgical instrument among Cartesian space, actuator space and joint space were derived for control purposes. The control system architecture of the MicroHand A was designed with intuitive motion control and motion scaling control. Llewellyn's absolute stability criterion and the transparency of the one-DOF master-slave system are also analysed. RESULTS: Intuitive motion control under dissimilar kinematics in master-slave manipulations and motion scaling control were accomplished to solve absonant hand-eye coordination, kinematic dissimilarity and workspace mismatch of master-slave manipulator problems. A series of tests and animal experiments were carried out to evaluate system performance. The experimental results demonstrate that the system could accomplish intuitive motion control and motion scaling control, and that the control system is stable and reliable. CONCLUSIONS: The experiments performed on the MicroHand A robotic system yielded expected control results. The system satisfies the requirements of minimally invasive surgery. Intuitive motion control and motion scaling control under different kinematics for the master and slave have been implemented.