Development of a Compliant-Based Microgripper for Microassembly
30 Dec 2008-pp 522-527
TL;DR: A combination of pseudo rigid body model (PRBM) and finite element analysis (FEA) has proven to expedite the prototyping procedure which effectively reduces the cost and modeling time and provides a rigorous approach to develop a compliant-based microgripper for performing high precision manipulation of micro-objects.
Abstract: Micro-scaled parts with dimension below 1 mm need to be manipulated with high precision and consistency in order to guarantee successful microassembly process. Often these requirements are difficult to be achieved mainly due to the constraints imposed by the grasping mechanism which will affect the accuracy of the manipulation. Furthermore, the object's texture and fragility imply that small perturbation by the grasping mechanism can result in substantial damage to the object and downgrading its geometry, shape, and quality. Conventional grippers based on rigid hinges are not capable to meet the demand of high precision manipulation and control of micro objects due to prevalent backlash and coulomb friction problems inherited within their joints. An effective way to address these problems is by introducing flexure based joints which will produce fully-monolithic grasping mechanism. This paper provides a rigorous approach to develop a compliant-based microgripper for performing high precision manipulation of micro-objects. A combination of pseudo rigid body model (PRBM) and finite element analysis (FEA) has proven to expedite the prototyping procedure which effectively reduces the cost and modeling time. An electro discharge machining (EDM) technique was utilized for the fabrication of the device. Series of experimental studies were conducted for performance verification and the results were compared with the computational analysis results. A high displacement amplification and maximum stroke of 100 mum can be achieved.
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TL;DR: In this paper, a monolithic compliant SPCA-driven micro-gripper was developed for micro-assembly and described the mechanism design, kinematic model, static model, control strategy and experimental verification of micro gripper.
40 citations
Cites background from "Development of a Compliant-Based Mi..."
...The parallelogram mechanism only exhibits one stable equilibrium position due to the small rotational angle of flexible hinges [34,35]....
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TL;DR: In this paper, an algorithm for designing inexpensive planar parallel robots with prescribed backlash-free workspace is presented. But the method of closing the backlash of the actuators uses preloaded flexible joints to replace the passive joints, which may be made using standard joints with preloaded springs or by using preloaded flexure joints.
Abstract: The precision of parallel robots is limited by backlash in their joints. This paper investigates algorithms for designing inexpensive planar parallel robots with prescribed backlash-free workspace. The method of closing the backlash of the actuators uses preloaded flexible joints to replace the passive joints. These flexible joints may be made using standard joints with preloaded springs or by using preloaded flexure joints. Given a norm-bounded wrench acting on the robot, an algorithm is presented for determining the required preload for the flexible joints in order to guarantee backlash-free operation along a path or within a prescribed workspace. An investigation of the effects of the preloaded flexible joints on the stiffness is carried out using performance measures comparing the same robot with or without preloaded joints. These performance measures use an extended stiffness definition based on three noncollinear vertices on the moving platform. This paper presents simulations of the statics, stiffness, and backlash prevention algorithm, followed by experimental validations. DOI: 10.1115/1.4000522
29 citations
TL;DR: In this paper, the authors analyze the sources of noise and take it into account in dynamic models of micromanipulation systems using millimeter sized cantilevers as end effectors.
23 citations
Cites background from "Development of a Compliant-Based Mi..."
...High precision micromanipulation tasks are required in a wide range of microrobotics applications, for instance microassembly [1], force sensing [2] and surgical operations [3]....
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TL;DR: In this paper, the authors illustrate the design of an adaptive robotic gripper as an engineering example to show the significance and approaches of applying TRIZ in getting the creative conceptual design ideas.
Abstract: Purpose – The essence of the conceptual design is getting the innovative projects or ideas to ensure the products with best performance. It has been proved that the theory of inventive problem solution (TRIZ) is a systematic methodology for innovation. The purpose of this paper is to illustrate the design of an adaptive robotic gripper as an engineering example to show the significance and approaches of applying TRIZ in getting the creative conceptual design ideas.Design/methodology/approach – Gripping and holding of objects are key tasks for robotic manipulators. The development of universal grippers able to pick up unfamiliar objects of widely varying shapes and surfaces is a very challenging task. The requirement for new adaptive grippers is the ability to detect and recognize objects in their environments.Findings – The main aim of this work is to show a systematic methodology for innovation as an effective procedure to enhance the capability of developing innovative products and to overcome the main ...
21 citations
TL;DR: In this article, a microassembly system composed of a Cartesian parallel robot with flexure revolute joints and a modular gripper with metamorphic fingertips, capable of adapting their shape to different micro objects is presented.
Abstract: Purpose – The purpose of this paper is to report research which led to the realization of a robot for miniaturized assembly endowed with high‐accuracy and high‐operative flexibility.Design/methodology/approach – The proposed solution is a microassembly system composed of a Cartesian parallel robot with flexure revolute joints and a modular gripper with metamorphic fingertips, capable of adapting their shape to different micro‐objects. The fingertips are realized by electro‐discharge machining from a sheet of superelastic alloy. Thanks to its modularity, the gripper can be arranged with two opposite fingers or three fingers placed at 120°. The fingers are actuated by a piezoelectric linear motor with nanometric accuracy.Findings – The experimental results on the prototype are very interesting. The measured positioning accuracy of the linear motors is 0.5 μm; the end‐effector positioning accuracy is lower, due to the non‐perfect kinematics and hysteresis of the flexure joints; however, these effects can be ...
18 citations
References
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589 citations
TL;DR: In this paper, a monolithic compliant-flexure-based micro gripper with piezoelectric actuation was designed and tested using a finite element analysis (FEA).
Abstract: Design, fabrication and tests of a monolithic compliant-flexure-based microgripper were performed. The geometry design and the material stresses were considered through the finite element analysis. The simulation model was used to study in detail profiles of von Mises stresses and deformation. The maximum stress in the microgripper is much smaller than the critical stress values for fatigue. The microgripper prototype was manufactured using micro-wire electrode discharge machining. A displacement amplification of 3.0 and a maximum stroke of 170 μm were achieved. The use of piezoelectric actuation allowed fine positioning. Micromanipulation tests were conducted to confirm potential applications of the microgripper with piezoelectric actuation in handling micro-objects. The simulation and experimental results have proven the good performance of the microgripper.
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TL;DR: The principal conclusion is that the approach of estimating position errors with some analytical functions is practical and generic, and most importantly it is effective enough to improve robot accuracy.
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01 Jan 2006-Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology
TL;DR: In this article, a long-travel piezoelectric-driven linear nanopositioning stage capable of operating in either a stepping mode or in a scanning mode is presented.
Abstract: This study presents a novel long-travel piezoelectric-driven linear nanopositioning stage capable of operating in either a stepping mode or in a scanning mode. In the stepping mode, the stick–slip friction effect between a linear micropositioner and a sliding stage is used to drive the stage step-by-step through an extended displacement range. The straightness precision of the stage displacement is ensured by running the stage along two high-precision cylindrical guide rails as it moves. The developed linear micropositioner delivers a high amplification of the piezoelectric actuator input and ensures minimum angular deviation. In the scanning mode, the micropositioner acts as an elastic deformation-type linear displacement amplification device and drives the stage through displacements in the micrometer level range. In practical applications, the scanning mode can be utilized to compensate for the final stage positioning error introduced during the stepping motion of the stage. In a series of experiments, a laser interferometer is employed to measure the displacement responses of the stage under the application of input driving voltages with various waveforms. The results demonstrate that in the stepping mode, the stage is capable of performing precision positioning over an extended displacement range in incremental step sizes ranging from 70 nm to 35 μm. Meanwhile, in the scanning mode, the stage can perform a scanning motion over a displacement range of 50 μm with a displacement resolution of less than 10 nm. Finally, it is shown that the high-precision cylindrical guide rails ensure a straightness error of the stage displacement of less than 50 nm within 10 mm motion range.
157 citations
TL;DR: In this article, an enhanced sliding mode motion tracking control methodology for piezoelectric actuators to track desired motion trajectories is proposed, which is based on the variable structure control approach.
Abstract: This paper proposes an enhanced sliding mode motion tracking control methodology for piezoelectric actuators to track desired motion trajectories. The proposed control methodology is established to accommodate parametric uncertainties, nonlinearities including the hysteresis effect, and other un-modelled disturbances, without any form of feed-forward compensation. The fundamental concept in this control strategy relies on the specification of a target performance and the formulation of an enhanced sliding mode control law based on the variable structure control approach. The control methodology ensures the convergence of the position tracking error to zero in the presence of the aforementioned conditions. The stability of the control methodology is proven theoretically and a precise tracking ability is demonstrated in the experimental study. One of the most important advantages of this control methodology is that the approach requires only a knowledge of the estimated system parameters together with their corresponding bounds and the bound of the non-linearities and disturbances in the physical realisation. Being capable of motion tracking, the proposed enhanced sliding mode control methodology is very attractive in the field of micro/nano manipulation through which high-precision piezoelectric actuation control applications can be realised.
138 citations