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A major deficiency of piezoelectric actuators is that their open-loop control accuracy is seriously limited by hysteresis. In this paper, a novel mathematical model is proposed to describe hysteresis precisely and a new parameter called turning voltage is introduced. It was found experimentally that the shapes of hysteresis curves are decided by the value of the turning voltage. A computer-based inverse control approach under open-loop operation based on the mathematical model was applied to suppress the inherent hysteresis to within ±1% full span range of a stack piezoelectric actuator and the performance of the piezoelectric actuator is noticeably improved.

This paper mainly focuses on dynamic modelling and real-time control for a parallel manipulator with flexible link. The Lagrange principle and assumed modes method (AMM) substructure technique is presented to formulate the dynamic modelling of a two-degrees-of-freedom (DOF) parallel manipulator with flexible links. Then, the singular perturbation technique (SPT) is used to decompose the nonlinear dynamic system into slow time-scale and fast time-scale subsystems. Furthermore, the SPT is employed to transform the differential algebraic equations (DAEs) for kinematic constraints into explicit ordinary differential equations (ODEs), which makes real-time control possible. In addition, a novel composite control scheme is presented; the computed torque control is applied for a slow subsystem and the H∞ technique for the fast subsystem, taking account of the model uncertainty and outside disturbance. The simulation results show the composite control can effectively achieve fast and accurate tracking control.

For the RRRR motion chain, a kind of sub-problem which can be described as rotating about four not intersecting axes to a given point and adjacent axes are parallel or vertical intersecting or vertical skew is proposed. By combining analytic geometry and screw theory exponential product method, the inverse kinematics solution of the RRRR motion chain is derived, and joint axes relations of motion chain being fit for the method are presented. The multi-solutions is analyzed and the geometric meanings is explained. The method has obvious geometric meanings and the solution can be verified by with the help of drawing. Using the method 6-R manipulator inverse solution is analyzed, and feasibility of this method is validated through the instance with exact parameters.

The paper proposes a real-time tracking algorithm for a moving object with mobile robot based on vision using adaptive color matching and Kalman filter. The adaptive color matching can limit the region containing moving object on vision image plane. It can adjust color matching threshold to reduce the influence of lighting variations in the scene. Kalman filter is used as our prediction module to calculate motion vectors of moving object in the robot coordinate system. A view window containing the position of moving object estimated by Kalman filter is determined on image plane to reduce the image processing area. Color matching threshold can adjust itself adaptively in view window, which is used as an updating module. Experimental results show that the algorithm can adapt to lighting variations and has good tracking precision. It can also be implemented in real time.

Broken bones precise repositioning and distal hole's locking of intramedullary nails are major challenges in orthopaedic surgery. This paper proposes a novel fluoroscopy guided robot-assisted orthopaedic surgery system which called HIT-RAOS to assist the surgeons to do this work. In the system, a parallel robot is used to imitate the tact of traditional clinic treatment in long bone fracture reposition, and a serial robot is employed to guide the surgeons to accomplish the locking of intramedullary nails, which are usually used to fix the broken bones in orthopaedic surgery now. All these are going under the guiding of fluoroscopy images, provided by a precise C-Arm X-Ray machine. And a teleoperating system, a surgeon console, control software are also developed in HIT-RAOS. The major goals are to assist surgeons to reposition broken bones, to guide the surgeon locking nail, to reduce the surgeon's working time under C-Arm, to do surgery planning and teaching, to improve the accuracy of reposition and rates of successfully locking of intramedullary nails, and so on. All these are realized in this system, which already been proved in clinic body sample trials.

Telesurgery systems have long been suffering variable and unpredictable Internet commutation time delay, operation fatigue, and other drawbacks. Based on virtual reality technology, a teleprogramming scheme combined with semi-autonomous control is introduced to guarantee the robustness and efficiency of teleoperation of HIT-RAOS, a robot-assisted orthopedic surgery system. In this system, without considering time delay, the operator can just interact with virtual environment which provides real-time 3D vision, stereophonic sound, and tactile and force feedback imitated by a parallel master manipulator. And several tasks can be managed simultaneously via semi-autonomous control. Finally, the method is experimentally demonstrated on an experiment of locking of intramedullary nails, and is shown to effectively provide stability and performances.