A novel actuator-internal micro/nano positioning stage with an arch-shape bridge type amplifier

This paper presents a novel actuator-internal two degree-of-freedom (2-DOF) micro/nano positioning stage actuated by piezoelectric (PZT) actuators, which can be used as a fine actuation part in dual-stage system. To compensate the positioning error of coarse stage and achieve a large motion stroke, a symmetrical structure with an arch-shape bridge type amplifier based on single notch circular flexure hinges is proposed and utilized in the positioning stage. Due to the compound bridge arm configuration and compact flexure hinge structure, the amplification mechanism can realize high lateral stiffness and compact structure simultaneously, which is of great importance to protect PZT actuators. The amplification mechanism is integrated into the decoupling mechanism to improve compactness, and to produce decoupled motion in X- and Y- axes. An analytical model is established to explore the static and dynamic characteristics, and the geometric parameters are optimized. The performance of the positioning stage is evaluated through finite element analysis (FEA) and experimental test. The results indicate that the stage can implement 2-DOF decoupled motion with a travel range of 55.4×53.2 μm2, and the motion resolution is 8 nm. The stage can be used in probe tip-based micro/nano scratching

Contact force sensing and control for inserting operation during precise assembly using a micromanipulator integrated with force sensors

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

Kinematic calibration in local assembly space of a six-axis industrial robot for precise assembly

The research on the calibration of industrial robots mainly focuses on the global workspace, but it is difficult to ensure that industrial robots have good absolute positioning accuracy in the workspace. This paper proposes a kinematic calibrating method of industrial robot in local assembly space to improve the positioning accuracy. The kinematic error model of industrial robot is established based on modified Denavit-Hartenberg (MDH) model. The influence of redundant error parameters on kinematic parameter identification is analyzed. The method used in kinematic parameters identification is improved by using correlation tolerance and matrix singular value decomposition. Then, simulation and experimental test are carried to investigate the performance of the calibrating method. The experimental results indicate that the positioning accuracy inside the workspace is significantly reduced from 1.716 mm to 0.149 mm

A dual-driven high precision rotary platform based on stick-slip principle

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