This paper presents a novel piezoelectrically actuated dual-axis micro manipulator with an asymmetric compliant structure. The mechanical design of the micro manipulator is first presented. A novel guiding bridge (GB)-type mechanism was proposed and utilized in the left part of the micro manipulator to improve the dynamic performance of the micro manipulator. The analytical model has been established based on pseudo-rigid-body (PRB) model and matrix-based compliance modeling (MCM) method. The kinematic and the precision of the micro manipulator have been analyzed, and the input and output couplings have been investigated. The prototype of the micro manipulator has been fabricated by wire electro discharge machining (WEDM). Then, open-loop experimental tests have been performed. The experimental results match well with the analytical calculation, and the amplification ratios are 11.12 and 4.64 for the left part and right part, respectively. Proportional-integral (PI) controller has been used to regulate the output displacement and grasping force, and a series of closed-loop experiments have been conducted to investigate the performance of the micro manipulator. The results show that the position resolution for both the right and left parts is 0.15 μm, and the force resolution is 4 mN.

To realize high precision rotation angle adjustment in micro/nano manipulation, a novel monolithic 2- degree of freedom (DOF) pure rotation platform is designed, fabricated and tested in this paper. The rotation platform is driven by two piezoelectric (PZT) actuators. Rotation decoupling is realized based on three Hooke's joints and a large rotation range is obtained based on two bridge-type mechanisms. Compared with other rotation platforms, the developed 2-DOF pure rotation platform has the advantages of fewer actuators due to rotation decoupling design and larger working frequency range due to compact structure and monolithic fabrication. An analytical model is established to calculate transmission ratio and input stiffness. The dominant parameters are determined based on sensitivity analysis. Finite element analysis (FEA) is conducted to investigate the characteristics of the rotation platform. Experimental tests are carried out to investigate the performance of the rotation platform. Decoupling test results show the maximum rotation angles in X- and Y- axes are 2.04 mrad and 2.12 mrad, respectively, and the X- and Y- axes relative coupling errors are 2.03% and 2.09%, respectively. Closed loop control results show that the settling time is 40 ms and the resolutions in X- and Y- axes are both 5 μrad.

Aiming at the realization of high precision angle adjusting, this article proposed a rotary platform based on stick-slip principle, which adopted a dual-driven working mode to realize large circular motion stroke and high loading capacity. Based on flexure hinges, a symmetrical flexible mechanism with two driving feet was designed to generate coupled driving displacement. By actuating the piezoelectrics alternatively, the proposed dual-driven working principle was described in detail, which could effectively suppress the back-off phenomenon and improve loading capacity. The theoretical analysis and finite element simulation were conducted to investigate the characteristic of flexible driving unit. The dynamic model of dual-driven working mode was established and simulated in MATLAB/Simulink, and the influence of preloading coefficient and initial preloading force were investigated, which provided a guidance for the design and optimization of stick-slip actuator. Additionally, a prototype was fabricated, and a series of experiments were conducted. The results indicated that the maximum rotary speed and loading capacity of rotary platform were 48.3 mrad/s and 98.8 mN·m, respectively.

This paper proposes a novel contact force sensing and control method for the inserting operation during precise assembly process, which is based on a micromanipulator integrated with force sensors. At first, theoretical analysis is carried out to calculate the admissible contact force between the gripped holes and the pegs. The contact force thresholds which are smaller than the admissible contact forces are adopted in the control algorithm to avoid the rotating of the gripped holes during assembly process. The force sensors are calibrated using an ATI force sensor and the conversing coefficients are calculated. The admissible contact forces are tested when different contact distance and preload force are adopted. The performance of the proposed contact force sensing and control method is verified by carrying out the task of applying contact force on the surface of the gripped holes with different contacting speeds. The results indicate that the contact force can be adjusted to be smaller than the threshold 1 and the peg-in-hole assembly can be completed successfully. Note to Practitioners—This paper proposes a novel contact force sensing method during the inserting operation. Compared with the traditional contact force sensing method, this paper adopts the force sensor integrated into the micromanipulator instead of commercial force sensor to detect the contact force between two parts. To ensure the assembling precision, the theoretical analysis is conducted to calculated the admissible contact force to avoid the sliding and rotating of the gripped micro part during assembling. This work efficiently simplifies the contact force sensing and control process, where complex calibration process needn’t to be carried out to eliminate the influence of the mass of the micromanipulator on the testing results. In addition, the assembling costs are reduced by replacing commercial force sensors with strain gauges.

This article reports the design, modeling, and experiments of a novel retinal surgery robot based on spatial variable remote center-of-motion (RCM) mechanism. The general design criteria for parallel mechanisms are proposed, and the planar five-bar mechanisms are evaluated and selected. The planar-spatial evolution process, including the parallel connection of the planar mechanism and the equivalent substitution of joints, is adopted to develop a spatial variable RCM mechanism and then the robot. The mobility and singularity of the robot are analyzed, and the forward/inverse kinematics and workspace are modeled. Dimension optimization is conducted based on a comprehensive performance indicator that characterizes the motion range of linear actuators and the global dexterity performance index of robot. The prototyped robot is fabricated and assembled, and the kinematic calibration is performed. The position error of end-effector is within 34 μm, and both the position error and deviation of the RCM point are within 23 μm. The robot is demonstrated to reach the desired position and execute the RCM motion with high precision simultaneously.