Parallel Micromanipulator Research Articles

Dynamic modeling and optimization of mechanical drift for compliant parallel micromanipulation driven by V-shape linear ultrasonic motors

Designing micro-mechanisms that satisfy large strokes, high precision, and multiple degrees of freedom has consistently been a research focus and challenge in the field of micromanipulation systems. Linear ultrasonic motors (LUMs), with advantages such as millimeter-level travel, nanometer-level motion resolution, and power-off self-locking, significantly contribute to the advancement in the mechanism design of micromanipulation systems. However, the challenge of mechanical drift lacks a comprehensive theoretical analysis to explain its cause and limits its application. This paper presents a mechanical drift modeling method for a compliant parallel micromanipulation (CPM) driven by a LUM. The model primarily focuses on the creep characteristics of the flexure clamp element in the LUM. Based on the stiffness matrix analysis method of the compliant parallel mechanism kinematics, the mechanical drift dynamics model of the CPM is established. The influence of the main structural parameters on the CPM mechanical drift is investigated. The research indicates that the creep of flexure clamps in the CPM is the main factor leading to the mechanical drift. Optimization of mechanical drift is achieved by choosing flexure clamps with higher tangential stiffness for LUM and flexure hinge joints with greater flexibility for CPM. Finally, experimental studies reveal that under equivalent conditions, the mechanical drift of the optimized CPM was significantly reduced than before, proving the rationality of the theoretical model and optimization method.

Compliance and Kinetostatics of a Novel 2PRS-2PSS Compliant Parallel Micromanipulator: Modeling and Analysis.

A novel 2PRS-2PSS (P represents the prismatic pair, R represents the revolute hinge, S represents the spherical hinge) compliant parallel micromanipulator with two translational DOFs and two rotational DOFs is presented, and its compliance model and kinetostatic model are sequentially developed and analyzed. Initially, an analytical model used to describe the compliance of this micromanipulator was developed using the compliance matrix method (CMM). Through a comparison with finite element analysis, the accuracy of this analytical model is confirmed, and the influence of various dimensional and structural parameters on the compliance behavior is investigated. Subsequently, the micromanipulator is treated as an equivalent spring system, allowing for the derivation of its governing equation based on the established compliance model. From this equation, a kinetostatic model relating input forces to output displacements is derived. Validation of this model is performed by comparing analytical results with finite element simulations under specific motion trajectories, revealing a maximum relative error of 6.18%. This close agreement verifies the accuracy of the kinetostatic model. Finally, the impact of the parameters of the flexure hinge on the mapping matrix is examined to offer insights into minimizing undesired displacements, providing valuable guidance for optimizing the micromanipulator's performance.

A Modeling Method for a 6-SPS Perpendicular Parallel Micro-Manipulation Robot Considering the Motion in Multiple Nonfunctional Directions and Nonlinear Hysteresis

Abstract Precision motion systems that call for an ultrahigh resolution are widely used in ultrahigh-precision engineering applications. In this article, a 6-SPS perpendicular compliant parallel micro-manipulation robot is presented. It is difficult to establish the mapping relationship between the applied voltage and end-effector pose due to the existence of compliant joints and piezoelectric actuators. A modeling method for a 6-SPS perpendicular compliant parallel micro-manipulation robot considering the motion in nonfunctional directions and hysteresis effect is proposed to reflect the characteristic from input voltage to output pose. The motion of the spherical compliant joint is regarded as a spatial six degrees-of-freedom mechanism. This method considers the motion errors in multiple nonfunctional directions of the compliant joints. The internal force and torque are also taken into account based on the spatial force and moment balance condition. The slow, fast dynamic modes, and hysteresis nonlinearity behavior are described using a series and parallel hybrid model structures. The kinematic model and compliance model without considering the motion in nonfunctional directions are conducted for comparison. Simulation results show that the presented modeling method has higher modeling accuracy. Finally, experiments on a 6DOF compliant parallel micro-manipulation robot reveal the fine modeling performance of the developed method for the precision motion systems in the presence of intrinsic hysteresis effect and motion error of compliant joints.

Optimal Design for 3-PSS Flexible Parallel Micromanipulator Based on Kinematic and Dynamic Characteristics.

This paper proposes two optimal design schemes for improving the kinematic and dynamic performance of the 3-PSS flexible parallel micromanipulator according to different application requirements and conditions. Firstly, the workspace, dexterity, frequencies, and driving forces of the mechanism are successively analyzed. Then, a progressive optimization design is carried out, in which the scale parameters of this mechanism are firstly optimized to maximize the workspace, combining the constraints of the minimum global dexterity of the mechanism. Based on the optimized scale parameters, the minimum thickness and the cutting radius of the flexure spherical hinge are further optimized for minimizing the required driving forces, combined with constraints of the minimum first-order natural frequency of the mechanism and the maximum stress of the flexure spherical hinge during the movement of the mechanism. Afterward, a synchronous optimization design is proposed, in which the scale parameters are optimized to maximize the first-order natural frequency of the mechanism, combined with the constraints of a certain inscribed circle of the maximum cross-section of the workspace, the maximum stroke of the selected piezoelectric stages, and the maximum ultimate angular displacement of the flexure spherical hinge. The effectiveness of both optimization methods is verified by the comparison of the kinematic and dynamic characteristics of the original and optimized mechanism. The advantage of the progressive optimization method is that both the workspace and the driving forces are optimized and the minimum requirements for global dexterity and first-order natural frequency are ensured. The merit of the synchronous optimization method is that only the scale parameters of the mechanism need to be optimized without changing the structural parameters of the flexible spherical hinge.

POMDP-Based Real-Time Path Planning for Manipulation of Multiple Microparticles via Optoelectronic Tweezers.

With high throughput and high flexibility, optoelectronic tweezers (OETs) hold huge potential for massively parallel micromanipulation. However, the trajectory of the virtual electrode has been planned in advance in most synchronous manipulations for multiple targets based on an optically induced dielectrophoresis (ODEP) mechanism, which is insufficient to ensure the stability and efficiency in an environment with potential collision risk. In this paper, a synchronously discretized manipulation method based on a centralized and decoupled path planner is proposed for transporting microparticles of different types with an OET platform. An approach based on the Kuhn-Munkres algorithm is utilized to achieve the goal assignment between target microparticles and goal positions. With the assistance of a visual feedback module, a path planning approach based on the POMDP algorithm dynamically determines the motion strategies of the particle movement to avoid potential collisions. The geometrical parameters of the virtual electrodes are optimized for different types of particles with the goal of maximum transport speed. The experiments of micropatterning with different morphologies and transporting multiple microparticles (e.g., polystyrene microspheres and 3T3 cells) to goal positions are performed. These results demonstrate that the proposed manipulation method based on optoelectronic tweezers is effective for multicell transport and promises to be used in biomedical manipulation tasks with high flexibility and efficiency.

Design and analysis of a novel large-range 3-DOF compliant parallel micromanipulator

Compared with the traditional rigid mechanism, the flexible mechanism has more advantages, which play an important role in critical situations such as microsurgery, IC (integrated circuit) fabrication/detection, and some precision operating environment. Especially, there is an increasing need for 3-DOF (degrees-of-freedom) compliant translational micro-platform (CTMP) providing good performance characteristics with large motion range, low cross coupling, and high spatial density. Decoupled topology design of the CTMP can easily realize these merits without increasing the difficulty of controlling. This paper proposes a new three DOF compliant hybrid micromanipulator which have large range of motion up to 100 μm × 100 μm × 100 μm in the direction in the dimension of 90 mm × 90 mm × 50 mm, smaller cross-axis coupling (the max coupling only 2.5%) than the initial XY compliant platform in XY axial.

Dynamic Modeling and Frequency Characteristic Analysis of a Novel 3-PSS Flexible Parallel Micro-Manipulator.

Dynamic modeling and frequency characteristic analysis of a novel 3-PSS (three-prismatic-spherical-spherical) flexible parallel micro-manipulator with three translational DOF in space were investigated in this paper. Firstly, the kinematics analysis was developed based on the pseudo-rigid body model. The Jacobian matrix and the relationship between the micro angular deformation of the flexible spherical hinge and the end pose of mobile platform were respectively obtained by employing vector closed-loop method and coordinate transformation method. Then, taking into account the elastic strain energy of the flexible spherical hinge, dynamic model of this mechanism was established via Lagrange equations, and the expression of natural frequency was further derived. Combined with a set of given parameters, natural frequencies of the system were calculated by using MATLAB software. For the comparison purpose, a simulated modal analysis of the mechanism with the same parameters was also performed by employing finite element ANSYS software. Results from numerical calculation and finite element simulation indicated that maximum error of their natural frequencies was 2.71%, which verified the correctness of the theoretical dynamic model. Finally, variations of natural frequencies with changes of the basic parameters were analyzed. Analysis results show that natural frequencies increase with the increase of the bending stiffness kbm of flexible spherical hinge and the difference in radius Er between static platform and mobile platform, while decrease with the increase of the length l of the link rod and the masses of the main components of mechanism. Besides, it can be further drawn from these obtained results that the natural frequencies increase with the increase of the angle θl between the link rod and the z axis of reference coordinate system. Considering that the increase of the stiffness kbm and the angle θl will reduce the scope of working space, it is recommended in designing the structure to choose a set of larger stiffness kbm and angle θl as much as possible under the premise of satisfying the working space.

Design and kinematics of a 3-DOF compliant triglide micromanipulator

This paper proposes a novel 3-degrees of freedom (DOF) compliant parallel micromanipulator. The design of the mechanism is based on triglide parallel manipulator. The compliant version of the triglide is prepared by making use of flexure joints. Displacement amplifiers are incorporated in the design to increase range of motions. The pseudo-rigid-body modeling technique is then used to formulate and solve the inverse kinematic problem for the design. To check the correctness and accuracy of the analytical kinematic model FEA simulations are performed in Abaqus-6.14 environment. Simulation results reveal that the proposed micromanipulator can perform different motions very effectively. Additionally, it is found that results predicted by the analytical model conform very closely to the simulation outcomes. The errors are very low, and the motions involve negligible parasitic motions.

Modeling and prototype experiment of a monolithic 3-PUU parallel micromanipulator with nano-scale accuracy

This paper presents the design and experimental investigation of a piezo-driven monolithic compliant 3-PUU (1 prismatic joint (P-joint) and 2 universal joints (U-joints)) XYZ micro/nano manipulator with a high bandwidth frequency and a large workspace. The manipulator is manufactured using a 3D-printing technique, thus a monolithic structure is guaranteed. This feature allows the manipulator to work smoothly with high resolution, accuracy, and repeatability, and simultaneously, it avoids all the deficiencies of non-monolithic designs such as backlash, wear, and friction. Analytical and computational studies are conducted to investigate and confirm the performances of the manipulator. Additionally, an experimental study is performed to verify the analytical and computational results. The workspace is calculated using the three methods, and their relative errors along each axis are shown to validate the accuracy of the results. The tracking performances of the manipulator are validated in a feedback control strategy. Moreover, the proposed manipulator demonstrates the motion resolution of 23 nm, 24 nm, and 18 nm along X, Y, and Z axes, respectively. Finally, the experimental frequency test supports the computational results and confirms the manipulator’s high bandwidth frequency.

An XYZ micromanipulator for precise positioning applications

A three-degrees-of-freedom (3-DOF) monolithic compliant parallel micromanipulator with bridge-type displacement amplifier is presented in this paper. The research aims are to design a monolithic mechanism with capability of working in three translational axes and having a high resonant frequency. As a result of being precise in rotation, circular flexure hinges are adopted in the structure of the proposed mechanism and its corresponding mathematical modeling is investigated. A finite element analysis (FEA) model is developed to perform analysis and predict the behaviour of the proposed mechanism and the utilized amplifier, and thus establish the computational Jacobian, workspace and amplification ratio. The stress-strain relationship of the proposed mechanism is investigated by applying safety factor and the results are presented. Finally, an experimental study is conducted to evaluate the dynamic and tracking performances of the proposed flexure-based spatial mechanism. A feedback Proportional-Integral (PI) control methodology is implemented to enhance the mechanism positioning performance and eliminate hysteresis effect inherent in piezoelectric actuators. Based on the designed parameters, the proposed manipulator can have a large workspace, high band-width frequency, and fine tracking resolution along each working axes.

Programmable Collective Behavior in Dynamically Self-Assembled Mobile Microrobotic Swarms.

Collective control of mobile microrobotic swarms is indispensable for their potential high‐impact applications in targeted drug delivery, medical diagnostics, parallel micromanipulation, and environmental sensing and remediation. Without integrated electronics for sensing and actuation, current microrobotic systems should rely on physical interactions among individual microrobots for local communication and cooperation. Here, it is shown that mobile microrobotic swarms with well‐defined collective behavior can be designed by engineering magnetic interactions among individual units. Microrobots, dynamically self‐assembled from magnetic microparticles into linear chains, locomote on surfaces in response to a precessing magnetic field. Control over precessing magnetic field allows engineering attractive and repulsive interactions among microrobots and, thus, collective order with well‐defined spatial organization and stable parallel operation over macroscale distances (≈1 cm) and through confining obstacles. The design approach described here addresses programmable assembly, propulsion, and collective behavior of dense mobile microrobot swarms simultaneously by engineering magnetic interactions and dynamic actuation of microrobots. The presented approach will advance swarm microrobotics by enabling facile and rapid formation of self‐organized and reconfigurable microrobotic swarms with programmable collective order and stability.

An investigation on kinematics and dynamics performance of a novel 3-PRC-compliant parallel micromanipulator

This article proposes a 3-PRC compliant parallel micromanipulator with 3 degrees of freedom. The piezoelectric actuator is adopted to drive the mechanism, and to compensate the stroke of the piezoelectric actuator, a new type of secondary lever amplification mechanism is designed. The kinematics model of the 3-PRC parallel micromanipulation platform is derived using vector method, and the forward and inverse kinematics solutions of a 3-PRC parallel micromanipulation stage are emphatically analyzed and then the Jacobian matrix of kinematics model and workspace are derived. Finally, the dynamic model is established by Lagrange equation, and the natural frequency of the mechanism is calculated. The modal analysis is carried out using finite element method. The results showed that the mechanism has a favorable performance on kinematics and dynamics, and this micromanipulator can achieve micro/nano level motion with high accuracy.

Design and Analysis of a New High Precision Decoupled XY Compact Parallel Micromanipulator

With the development of nanotechnology that contains automatic control, precision machinery and precise measurement, etc., micro/nano manipulation has become a new research direction in recent years. This paper presents the design and analysis procedures of a new high precision XY decoupled compact parallel micromanipulator (DCPM) for micro scale positioning applications. The DCPM is made up of the decoupler, two-stage amplifier and the piezoelectric translator (PZT) actuators, which utilizes the characteristics of flexure hinges. In this paper, firstly, a new two-stage bridge-principle amplifier is proposed by a serial connection of two fundamental bridge amplifiers in order to increase the ratio of amplification. It is pivotal for designing the micromanipulator. Then, the kinematic modeling of the micromanipulator is carried out by resorting to stiffness and compliance analysis via matrix method. Finally, the performance of the micromanipulator is validated by finite-element analysis (FEA) which is preliminary job for fabricating the prototype and designing the control system of the XY stage that is expected to be adopted into micro/nano manipulations.

An automated focusing method for a parallel micro-manipulator alignment

In this work, particle swarm optimization (PSO) algorithm is employed to align spot array and judging image sharpness with auto-focusing (AF) image evaluation function. To satisfy the requirement of optical alignment system, a high precision manipulator has to be developed. Applied parallel manipulator that consists of four 2-degree of freedom (DOF) decoupled actuator gives chances to provide 6-DOF independence motion, and has strength in high accuracy. This paper covers the follows: Firstly, motivation of this development for the digital mirror device (DMD) based maskless lithography system to introduce spot array method in maskless digital exposure process. Secondly, in order to precisely control moving platform, applying a redundant parallel micro-manipulator. Thirdly, proposing a suitable error model of the system and applying the PSO and Z axis auto-focusing algorithm to align spot array concerning position correction. Finally, we designed experiment which is applied a vision sensor and alignment unit to verify proposed positioning algorithm. Experimental result will be shown that proposed can solve the alignment problem by reducing the position error of the system.

Design and Experimental Testing of an Improved Large-Range Decoupled XY Compliant Parallel Micromanipulator1

There is an increasing need for XY compliant parallel micromanipulators (CPMs) providing good performance characteristics such as large motion range, well-constrained cross-axis coupling, and parasitic rotation. Decoupled topology design of the CPMs can easily realize these merits without increasing the difficulty of controlling. This paper proposes an improved 4-PP model on the basis of a classical 4-PP model and both of them are selected for manufacturing and testing to verify the effectiveness of the improvement. It has shown from experimental results that there is a large improvement on the performances of improved 4-PP compliant parallel manipulator (CPM): large range of motion up to 5 mm × 5 mm in the unidirection in the dimension of 311 mm × 311 mm × 24 mm, smaller compliance fluctuation (only 36.63% of that of the initial 4-PP model), smaller cross-axis coupling (only 28.10% of that of the initial 4-PP model generated by a single-axis 5 mm actuation), smaller in-plane parasitic yaw (only 57.14% of that of the initial 4-PP model generated by double-axis 5 mm actuation).

Modeling and experimental study of a novel 3-RPR parallel micro-manipulator

We propose a novel planar micro-manipulator, which uses a 3-RPR parallel mechanism. The micro-manipulator is characterized by parallel mechanism, monolithic and compliant structure and piezoelectric (PZT) actuation. The structure and characteristics of the 3-RPR micro-manipulator are presented and the relationships between actuation displacements, driving forces, PZT inputs and the end pose are derived. Based on the derived model, the micro-manipulator workspace is analyzed. To increase the accuracy of the prototype, an experimentally calibrated open-loop model is proposed. Finally, we carried out experiments on planar translational and rotational trajectories to demonstrate the prototype performance. The result shows the high accuracy of the proposed micro-manipulator and its promising application prospects in micro/nano-engineering. We proposed a novel 3-RPR parallel micro-manipulator driven by PZT actuators.The kinematics of 3-RPR mechanism and single RPR chain are studied.The relationship between PZT displacement and end-pose is derived.Experiment shows the ability to achieve trajectories with high accuracy.

Feedback control for noise-aided parallel micromanipulation of several particles using dielectrophoresis.

The paper describes a novel control strategy for simultaneous manipulation of several microscale particles over a planar microelectrode array using dielectrophoresis. The approach is based on a combination of numerical nonlinear optimization, which gives a systematic computational procedure for finding the voltages applied to the individual electrodes, and exploitation of the intrinsic noise, which compensates for the loss of controllability when two identical particles are exposed to identical forces. Although interesting on its own, the proposed functionality can also be seen as a preliminary achievement in a quest for a technique for separation of two particles. The approach is tested experimentally with polystyrene beads (50 microns in diameter) immersed in deionized water on a flat microelectrode array with parallel electrodes. A digital camera and computer vision algorithm are used to measure the positions. Two distinguishing features of the proposed control strategy are that the range of motion is not limited to interelectrode gaps and that independent manipulation of several particles simultaneously is feasible even on a simple microelectrode array.

Performance analysis and optimization of a five-degrees-of-freedom compliant hybrid parallel micromanipulator

There are generally two main directions for the investigation and development of parallel manipulators, namely macro/meso stream and micro/nano stream, in which the former one has been thoroughly investigated in recent decades, while the latter one still remains many performance related open issues that significantly affect their application potentials in critical situations such as high-precision automated cell manipulation. Improving the overall performance of parallel manipulators is the bridge to connect the academia and industry for the great development and real-world application. This research is to develop a novel methodology called performance decomposition and integration for governing the design optimization process of complicated micromanipulator. A new five degrees-of-freedom (DOF) compliant hybrid parallel micromanipulator which is configured with five identical PSS limbs and one constraining UPU limb is proposed as a case study. The performance visualization, finite element analysis, and dimensional optimization are implemented. The proposed methodology is applicable for the design improvement of different kinds of compliant/parallel mechanisms. Performance is a critical topic for the further improvement of compliant parallel mechanisms.The research attempts to propose a paradigm called performance decomposition and integration to manage the overall performance of these mechanisms in a higher level.A CHPMM is proposed as an example to showcase part of the principle of PDI in the process of design and optimization.The proposed method can be well integrated with the methodology of system hybridization through the specific methods of mechanism hybridization, actuation hybridization and optimization hybridization.For the future work, a physical prototype will be manufactured to further improve the overall performance in aspects of manipulation and control under the guidance of the proposed methods.

Modeling and prototype experiment of a six-DOF parallel micro-manipulator with nano-scale accuracy

This paper presents a high-accurate micro-manipulator featured with monolithic compliant structure, orthogonally arranged parallel mechanism and piezoelectric (PZT) actuation. 6-SPS mechanism is employed to provide six degrees of freedom (DOF), including three linear translations and three rotations. The kinematics and stiffness of the micro-manipulator is studied first in this paper. Then, the relationship between PZT nominal displacement and the end pose is derived. Aiming at achieving trajectories with nano-scale accuracy, a two-step strategy is proposed. Finite element analysis (FEA) is conducted to verify the kinematics and stiffness model. Finally, in order to demonstrate the performance of the micro-manipulator, experiments of typical trajectories are carried out. The experimental result shows that the proposed micro-manipulator is capable of achieving trajectories with nano-scale accuracy.

Kinematics Analysis of a Novel Five-Degree-of-Freedom Spatial Parallel Micromanipulator

A study of the inverse kinematics for a five-degree-of-freedom (DOF) spatial parallel micromanipulator is presented here below. The objective of this paper is the introduction of a structural and geometrical model of a novel five-degree-of-freedom spatial parallel micromanipulator, analysis of the effective and useful workspace of the micromechanism, presentation of the obtained analytical solutions of the microrobot’s inverse kinematics tasks, and verification of its correctness using selected computer programs and computation environments. The mathematical model presented in this paper describes the behaviour of individual elements for the applied 2-DOF novel piezoelectric actuator, resulting from the position and orientation of the microrobot’s moving platform.