Compound Parallelogram Flexure Research Articles

Design of a New XY Flexure Micropositioning Stage With a Large Hollow Platform

This paper presents the design of a new flexure-based xy micropositioning stage with a large hollow platform, which is suitable for practical use with a microscope. The designed mechanism has a parallel-kinematic structure and is actuated by two voice coil motors. By employing multistage compound parallelogram flexures, the stage is designed as a four-layer structure, which produces a motion output platform with a large hollow space and large range of motion. Analytical modeling was carried out for parametric design of the stage. Evaluation results show that the designed xy stage exhibits a large safety factor and high natural frequency. Moreover, the large hollow platform is well-suited for practical applications with a microscope.

Design, analysis and testing of a novel decoupled 2-DOF flexure-based micropositioning stage

This paper presents the design, analysis and testing of a novel decoupled 2-DOF flexure-based micropositioning stage driven by piezoelectric-actuators (PZTs). In order to enlarge the travel range, a Scott-Russell mechanism and leverage mechanism are arranged in series, constituting a two-grade displacement amplifier to conquer the small displacement of the PZT. The design micropositioning stage is composed of symmetrically distributed flexure modules and each flexure module comprises compound parallelogram flexure beams serving as input decoupling, which allows the output decoupling by employing the tridimensional double compound parallelogram flexure mechanism. Based on the analytical model of both the amplifier and the XY stage established in static and dynamic analysis, the dimensions and performance of the stage has been conducted, which are verified by finite element analysis with ANSYS Workbench and prototype experiment with the fabricated prototype of the designed stage. It can be seen that the workspace of the developed stage is m with the maximum output coupling errors of 0.693% and 0.637% in the y and x directions. The experimental results demonstrate that the proposed micropositioning stage possesses good performance in trajectory tracking and can achieve a wide range of precise positioning.

Design of a PVDF-MFC Force Sensor for Robot-Assisted Single Cell Microinjection

Robot-assisted cell microinjection is an important approach to modern biological applications. Micro-force sensor is a crucial device to facilitate a precise injection of biological cells. Majority of existing film-based force sensors are designed as a cantilever structure for cell injection application. However, such kind of force sensor has inherent disadvantages in terms of unstable transmission of injection force, bigger puncturing wound, and operation inaccuracy. In this paper, a novel 1-D force sensor is designed by using polyvinylidene fluoride (PVDF) and macro fiber composite (MFC) films as fixed-guided beams to construct a multistage compound parallelogram flexure mechanism. It enables both capabilities of force sensing and stable cell holding. A prototype is fabricated, calibrated, and applied to crab egg embryo injection. The transverse strain effect of the fixed-guided sensing beams has been quantitatively measured by experiments. Comparison investigation reveals the great potential of MFC film over PVDF film for force sensing in cell microinjection application. The MFC force sensor offers the resolution, sensitivity, and measuring range of 0.80 mN, 1.23 mV/mN, and 100 mN, respectively. Microinjection experiments demonstrate that the developed force sensor faithfully reveals the process of cell injection and measures the puncturing force of 27 mN for crab eggs in real time.

Design and Experimental Research of a Novel Stick-Slip Type Piezoelectric Actuator

A linear piezoelectric actuator based on the stick-slip principle is presented and tested in this paper. With the help of changeable vertical preload force flexure hinge, the designed linear actuator can achieve both large travel stick-slip motion and high-resolution stepping displacement. The developed actuator mainly consists of a bridge-type flexure hinge mechanism, a compound parallelogram flexure hinge mechanism, and two piezoelectric stacks. The mechanical structure and motion principle of the linear actuator were illustrated, and the finite element method (FEM) is adopted. An optimal parametric study of the flexure hinge is performed by a finite element analysis-based response surface methodology. In order to investigate the actuator’s working performance, a prototype was manufactured and a series of experiments were carried out. The results indicate that the maximum motion speed is about 3.27 mm/s and the minimum stepping displacement is 0.29 μm. Finally, a vibration test was carried out to obtain the first natural frequency of the actuator, and an in situ observation was conducted to investigate actuator’s stick-slip working condition. The experimental results confirm the feasibility of the proposed actuator, and the motion speed and displacement are both improved compared with the traditional stick-slip motion actuator.

Design of a Large-Stroke Bistable Mechanism for the Application in Constant-Force Micropositioning Stage

To overcome the constraint of conventional tilted beam-based bistable mechanism, this paper proposes a novel type of bistable structure based on tilted-angle compound parallelogram flexure to achieve a larger stroke of negative stiffness region while maintaining a compact physical size. As an application of the presented bistable mechanism, a flexure constant-force micropositioning stage is designed to deliver a large stroke. The constant force output is obtained by combining a bistable flexure mechanism with a positive-stiffness flexure mechanism. To facilitate the parametric design of the flexure mechanism, analytical models are derived to quantify the stage performance. The models are verified by carrying out nonlinear finite-element analysis (FEA). A metal prototype is fabricated for experimental study. Results demonstrate the effectiveness of the proposed ideas for a long-stroke, constant-force compliant mechanism dedicated to precision micropositioning applications. Experimental results also show the appearance of two-stage constant force due to the manufacturing errors of the bistable beams.

New Flexure Parallel-Kinematic Micropositioning System With Large Workspace

Flexure-based micropositioning systems with a large workspace are attractive for a variety of precision engineering applications. In this paper, a new idea of multistage compound parallelogram flexure is proposed for the mechanism design of a novel parallel-kinematic XY micropositioning system, which has a motion range larger than 10 mm along with a compact structure. The established quantitative models and the stage performances are validated by conducting finite-element analysis (FEA) and experimental studies. Moreover, an enhanced model-predictive control (EMPC) is presented for positioning control of the system, which has a nonminimum-phase plant. It is shown that the EMPC is capable of producing a low magnitude of output tracking error by imposing an appropriate suppression on the control effort. Simulation and experimental studies reveal that the EMPC scheme outperforms the conventional proportional-integral-derivative (PID) and MPC methods in terms of transient response speed and steady-state accuracy. The idea that is presented in this paper is extendable to design and control of other micro-/nanopositioning systems with either minimum- or nonminimum-phase plants.

A Novel Piezoactuated XY Stage With Parallel, Decoupled, and Stacked Flexure Structure for Micro-/Nanopositioning

This paper presents the design and manufacturing processes of a new piezoactuated XY stage with integrated parallel, decoupled, and stacked kinematics structure for micro-/nanopositioning application. The flexure-based XY stage is composed of two decoupled prismatic-prismatic limbs which are constructed by compound parallelogram flexures and compound bridge-type displacement amplifiers. The two limbs are assembled in a parallel and stacked manner to achieve a compact stage with the merits of parallel kinematics. Analytical models for the mechanical performance assessment of the stage in terms of kinematics, statics, stiffness, load capacity, and dynamics are derived and verified with finite element analysis. A prototype of the XY stage is then fabricated, and its decoupling property is tested. Moreover, the Bouc-Wen hysteresis model of the system is identified by resorting to particle swarm optimization, and a control scheme combining the inverse hysteresis model-based feedforward with feedback control is employed to compensate for the plant nonlinearity and uncertainty. Experimental results reveal that a submicrometer accuracy single-axis motion tracking and biaxial contouring can be achieved by the micropositioning system, which validate the effectiveness of the proposed mechanism and controller designs as well.

A Totally Decoupled Piezo-Driven XYZ Flexure Parallel Micropositioning Stage for Micro/Nanomanipulation

This paper reports the design and development processes of a totally decoupled flexure-based XYZ parallel-kinematics micropositioning stage with piezoelectric actuation. The uniqueness of the proposed XYZ stage lies in that it possesses both input and output decoupling properties with integrated displacement amplifiers. The input decoupling is realized by actuation isolation using double compound parallelogram flexures with large transverse stiffness, and the output decoupling is implemented by employing two-dimensional (2-D) compound parallelogram flexures. By simplifying each flexure hinge as a two-degree-of-freedom (2-DOF) compliant joint, analytical models of kinematics, statics, and dynamics of the XYZ stage are established and then validated with finite-element analysis (FEA). The derived models are further adopted for optimal design of the stage through particle swarm optimization (PSO), and a prototype of XYZ stage is fabricated for performance tests. The nonsymmetric hysteresis behavior of the piezo-stage is identified with the modified Prandtl-Ishlinskii (MPI) model, and a control scheme combining the inverse model-based feedforward with feedback control is constructed to compensate the plant nonlinearity and uncertainty. Experimental results reveal that a submicron accuracy 1-D and 3-D positioning can be achieved by the system, which confirms the effectiveness of the proposed mechanism and controller design as well.

Design and Analysis of a Totally Decoupled Flexure-Based XY Parallel Micromanipulator

In this paper, a concept of totally decoupling is proposed for the design of a flexure parallel micromanipulator with both input and output decoupling. Based on flexure hinges, the design procedure for an XY totally decoupled parallel stage (TDPS) is presented, which is featured with decoupled actuation and decoupled output motion as well. By employing (double) compound parallelogram flexures and a compact displacement amplifier, a class of novel XY TDPS with simple and symmetric structures are enumerated, and one example is chosen for further analysis. The kinematic and dynamic modeling of the manipulator are conducted by resorting to compliance and stiffness analysis based on the matrix method, which are validated by finite-element analysis (FEA). In view of predefined performance constraints, the dimension optimization is carried out by means of particle swarm optimization, and a prototype of the optimized stage is fabricated for performance tests. Both FEA and experimental studies well validate the decoupling property of the XY stage that is expected to be adopted into micro-/nanoscale manipulations.