Controlling the contact force on workpieces is a challenging task for industrial deburring operations. To solve this issue, a novel constant force mechanism (CFM) based on the combination of positive ...and negative stiffness mechanism is proposed by using folding beam and bi-stable beam mechanisms. Without using any additional sensors and control algorithms, the proposed CFM can produce a travel range in constant force manner. In this paper, the design concepts, analytical model, finite element analysis (FEA) simulation and experimental studies are presented and discussed. Firstly, a novel spatial CFM is proposed and the pseudo rigid body (PRB) method is used to establish the mathematical model of the whole mechanism. Then, the FEA simulation is performed to validate the correctness of theoretical analysis. In addition, to eliminate the force variation, particle swarm optimization (PSO) method is utilized to find optimal architectural parameters solutions of the CFM. Finally, the experimental tests are performed to verify the performance of the designed CFM. The configuration design and parameter optimization proposed in this paper can be further applied to the design of other types of CFM mechanisms for polishing operations as well.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This article aims to present a minimum-jerk trajectory planning approach to address the smooth trajectory generation problem of 3-prismatic-universal-universal translational parallel kinematic ...manipulator. First, comprehensive kinematics and dynamics characteristics of this 3-prismatic-universal-universal parallel kinematic manipulator are analyzed by virtue of the accepted link Jacobian matrices and proverbial virtual work principle. To satisfy indispensable continuity and smoothness requirements, the discretized piecewise quintic polynomials are employed to interpolate the sequence of joints’ angular position knots which are transformed from these predefined via-points in Cartesian space. Furthermore, the trajectory planning problem is directly converted into a constrained nonlinear multi-variables optimization problem of which objective function is to minimize the maximum of the joints’ angular jerk throughout the whole trajectory. Finally, two typical application simulations using the reliable sequential quadratic programming algorithm demonstrate that this proposed minimum-jerk trajectory planning approach is of explicit feasibility and appreciable effectiveness.
A hybrid kinematic machine (HKM) tool with the respective advantages of serial and parallel mechanism is a significant direction for the innovation and development of current advanced sophisticated ...manufacturing equipment. This paper considers the configuration design, kinematics analysis and dynamics analysis of a 1-translational-3-rotational (1T3R) parallel manipulator, which acts as the main movement module of a novel 6-DOF reconfigurable HKM. The key parallel manipulator with 4 DOFs is composed of one middle
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RU kinematic chain and three identical
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US kinematic chains. First, complete kinematics characteristics, including position, velocity, acceleration and jerk, are deeply analyzed by a vector analysis approach. Reachable position workspace and orientation workspace were derived through the workspace boundary search method. Furthermore, complete inverse dynamics model of the 3
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US-
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RU parallel manipulator was formulated by virtue of the virtual work principle with considering the inertial and gravitational properties of struts. Finally, a driving power and energy consumption model of each actuated motor under the prescribed trajectory were obtained, resulting in the decouple contribution of each motion part correspondingly. This systematic and rigorous methodology aims at laying a solid theoretical and technical foundation for configuration design and performance analysis of this homologous type HKM.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Based on the background of atomic force microscope (AFM) driven by piezoelectric actuators (PEAs), this paper proposes a sliding mode control coupled with an inverse Bouc⁻Wen (BW) hysteresis ...compensator to improve the positioning performance of PEAs. The intrinsic hysteresis and creep characteristics degrade the performance of the PEA and cause accuracy loss. Although creep effect can be eliminated by the closed-loop control approach, hysteresis effects need to be compensated and alleviated by hysteresis compensators. For the purpose of dealing with the estimation errors, unmodeled vibration, and disturbances, a sliding mode control with perturbation estimation (SMCPE) method is adopted to enhance the performance and robustness of the system. In order to validate the feasibility and performance of the proposed method, experimental studies are carried out, and the results show that the proposed controller performs better than a proportional-integral-derivative (PID) controller at 1 and 2 Hz, reducing error to 1.2% and 1.4%, respectively.
With flexure-based micro-positioning stages (MPSs) being in high demand for high-precision applications, the performance and cost of flexure-based MPSs are two issues that urgently need to be ...addressed. In addition, the current MPSs are being developed toward complex spatial configurations, which further precludes monolithic fabrication. To address the aforementioned issues, modular MPSs using designed standardized modules are introduced in this paper. Firstly, the motivations are described, followed by the modular design. In addition, a new assembly concept analogy with composing compounds is proposed for guiding module assembly, including some proposed planar and spatial configurations. For validation, the static and dynamic performances of modular MPSs with respect to different modules and materials are presented as case studies. The proposed modular MPSs can provide better flexibility and functionality for further applications.
The Preisach model is a typical scalar mathematical model used to describe the hysteresis phenomena, and it attracts considerable attention. However, parameter identification for the Preisach model ...remains a challenging issue. In this paper, an improved particle swarm optimization (IPSO) method is proposed to identify Preisach model parameters. Firstly, the Preisach model is established by introducing a Gaussian-Gaussian distribution function to replace density function. Secondly, the IPSO algorithm is adopted to Fimplement the parameter identification. Finally, the model parameter identification results are compared with the hysteresis loop of the piezoelectric actuator. Compared with the traditional Particle Swarm Optimization (PSO) algorithm, the IPSO algorithm demonstrates faster convergence, less calculation time and higher calculation accuracy. This proposed method provides an efficient approach to model and identify the Preisach hysteresis of piezoelectric actuators.
Micro-positioning stages, which are capable to meet the emerging industrial trend for performing various kinds of micro-manipulation and micro-assembly tasks are the crucial tools to miniaturize the ...products under ultra-high precision. The current main practice is to specifically tailor a monolithic positioning stage design for one kind of micro-manipulation application. However, the design and fabrication of such a specific flexure-based micro-positioning stage are expensive in both the time and financial investment. In order to increase the flexibility and functionality of micro-positioning stages, this paper proposes a novel reconfigurable planar micro-positioning stages platform based on different function modules. A functional model-based approach is developed to divide one micro-positioning stage into a set of functionally independent sub-models, which allows flexible composition resulting in an adjustable new stage. The robustness of the proposed platform is demonstrated using some typical micro-positioning stages benchmarking cases. The effectiveness of assembly using flexible function modules is verified to show the benefits of the proposed design platform for reconfigurable micro-positioning stages.
The flexure-based fast tool servo, which is well adopted to manufacture non-circular section parts, has attracted many researchers’ attention for its cutting-edge characteristics in non-circular ...turning operation in terms of large output displacement, high bandwidth frequency, and fine surface processing. The geometric design and corresponding parameters configuration of the flexure hinge are deterministic to the performance of fast tool servo. In order to achieve a well-balanced stroke and natural frequency of the fast tool servo, this article proposes a harmony search–based multi-objective optimization method for setting of design parameters. Referring to the Lagrange method, the relationship between parameters of the flexure hinges and stiffness of the mechanism is derived and analyzed. Finite element analysis method is performed which demonstrates a fine agreement between the results from simulations and that from the proposed analytical solutions.
To solve the problem of insufficient constant-force stroke of the compliant constant force mechanism (CFM), a FEA-based optimization method based on structural parameters is proposed in this paper. ...Firstly, a flexure-based constant force module (FBCFM) combined with a Z-shaped beam and a bi-stable beam is designed. By analyzing the force-displacement relationship of the two kind beams, the architectural parameters related to the constant force characteristic of the FBCFM are derived. Then, the initial constant-force stroke with 2.2 mm and output constant force with 13.8 N of the FBCFM are obtained by experimental studies. Furthermore, to explore the parametric effects for the designed FBCFM, parametric evaluation is conducted via MATLAB. Finally, the optimal solution set of architecture parameters is obtained with FEA-based optimization method. Through experimental verification, the constant-force stroke of the optimized FBCFM is 4.5 mm with constant force 8.5 N. The optimization results show the effectiveness and feasibility of the proposed FEA-based optimization method.
This paper proposes a FEA-based optimization method for a typical FBCFM, which can obtain the optimal constant force property of the FBCFM under the optimization goal of a larger constant-force stroke. the validity and reliability of the FEA-based optimization method are verified by experimental setup. The research results can play a positive role in promoting the research on parametric optimization and expanding application of CFM. Display omitted
•AZ-type positive stiffness mechanism with good linearity is proposed.•Using FEA based optimization method can obtain optimal solutions more efficiently.•The 3D response surfaces and sensitivity relationship are derived.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The realizing of variable output constant force has received wide attention. To achieve a force regulation in an economic way, a configuration of the constant force mechanism (CFM) referring to ...positive and negative stiffness combination method is proposed in this paper. By adjusting preloading displacement applied on positive-stiffness structure of the CFM, the variable constant force output can be realized. The force–displacement expression of the CFM in the non-preloaded condition is deduced by the established analytical models. Furthermore, parametric sensitivity analysis with several architectural parameters are conducted for optimizing physical structures. Finally, the correctness of the proposed principle is verified by experimental studies. The observed experimental results show that the CFM under different preloading displacements can provide required output constant force, which is consistent with proposed hypothesis.
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