The hydraulic actuation of multi-body structures through large scale motions. Part 1: Development and validation of system model
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Modern engineering design is leading towards structures that are complex and lightweight. These structures often contain flexible and rigid components actuated through large displacements by a non-linear hydraulic system. Due to the increased system complexities, there is a need to define structural models that can be easily coupled to models of the hydraulic system for use in the design of suitable controllers. The current paper develops a modular system model composed of rigid and flexible structural components coupled directly to a non-linear hydraulic system. The resulting model allows for changes to be made to the hydraulic and structural components in an independent manner such that the entire system may be incorporated in a single simulation domain. A structural damping matrix is introduced that allows a control system designer to assign realistic modal damping ratios to well established modes, and higher damping to modes with significant uncertainty. This allows for increased steady-state accuracy and model run-time efficiency, which is beneficial to the controller design process presented in Part 2. The system modelling approach is applied to a hydraulically actuated experimental rig for validation purposes.Keywords:
Structural system
Damping matrix
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Damping matrix
Identification
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Damping still remains one of the least well-understood aspects of general vibration analysis. In this paper, a new experimental damping identification method, which can be able to identify both viscous and structural damping in the dynamic system, is proposed. The proposed method is a direct method and gives explicit structural and viscous damping matrices. The proposed method requires prior knowledge of accurate mass and stiffness matrices. So, experimental viscous-structural damping is identified in two steps. In the first step, mass and stiffness matrices are updated and subsequently viscous and structural damping matrices are identified using updated mass and stiffness matrices obtained in Step 1. The identified viscous-structural damping matrices are both symmetric and positive definite. The effectiveness of the proposed structural damping identification method is demonstrated by numerical and experimental examples. First, two numerical study of lumped mass system and fixed-fixed beam are presented which is followed by an experimental example of cantilever beam. The effects of coordinate incompleteness and different level of damping are investigated. The results have shown that the proposed method is able to identify accurately both viscous and structural damping in the dynamic system.
Damping matrix
Viscous damping
Structural system
Added mass
Identification
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Modular development is paid more and more attention to,which can bring distinctive advantages,but it also has some limitations,so the imminent question is how to utilize modularity equitably and make its merit maximum.This paper tries to survey modularity from modular product and modular organization.The paper analyzes the relationship of modular product,modular organization and innovation,measures the relationship of modular cost and modular profits and gives the essential conditions of modular development in the view of innovation.Then the modular analysis framework is built in order to provide theoretical direction for modularity practice.
Modularity
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Damping matrix
Mode (computer interface)
Matrix (chemical analysis)
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Natural frequency
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The paper presents a linear matrix inequality (LMI)-based approach for the simultaneous optimal design of output feedback control gains and damping parameters in structural systems with collocated actuators and sensors. The proposed integrated design is based on simplified H 2 and H ¿ norm upper bound calculations for collocated structural systems. Using these upper bound results, the combined design of the damping parameters of the structural system and the output feedback controller to satisfy closed-loop H 2 or H ¿ performance specifications is formulated as an LMI optimization problem with respect to the unknown damping coefficients and feedback gains. Numerical examples motivated from structural and aerospace engineering applications demonstrate the advantages and computational efficiency of the proposed technique for integrated structural and control design. The effectiveness of the proposed integrated design becomes apparent, especially in very large scale structural systems where the use of classical methods for solving Lyapunov and Riccati equations associated with H 2 and H ¿ designs are time-consuming or intractable.
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Modular and reconfigurable robotic systems have been designed to provide a customized solution for the non-repetitive tasks to be performed in a constrained environment. Customized solutions are normally extracted from task-based optimization of the possible manipulator configurations but the solution are not integrated, for providing the modular compositions directly. In this work, in the first phase, a strategy of finding unconventional optimal configurations with minimal number of degrees-of-freedom are discussed based upon the prescribed working locations and the cluttered environment. Then, in the second phase, design of the modular and reconfigurable architecture is presented which can adapt these unconventional robotic parameters. Rather than generating and evolving the modular compositions, a strategy is presented through which the unconventional optimal configurations can be mapped directly to the modular compositions. The generated modular composition is validated using Robot Operating System for the motion planning between the prescribed working locations in a given cluttered environment.
Self-reconfiguring modular robot
Modularity
Robot manipulator
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Modular Machine Tool is a specialized machine tool which is composed of general-purpose and special-purpose components. It is easy to operate, has high efficiency and is widely used in mass production. The main general accessory of the Modular machine tool is the dynamic slipway which is used to achieve feed motion. It can accomplish machining such as boring and milling by combining the dynamic slipway and different purposes spindle heads. There are two slipways of the dynamic slipway which are the mechanical slide and the hydraulic slide. Hydraulic sliding table is to transform hydraulic energy provided by pump station into mechanical energy, which can realize sliding table movement.Modular Machine Tool hydraulic system requires the smooth speed changing-over, stable feed rate, rational power-utilization, also it can be improved basic on the specific conditions of the enterprise.
Machine tool
Table (database)
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Damping matrix
Matrix (chemical analysis)
Modal matrix
Mass matrix
Damping ratio
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Damping still remains one of the least well-understood aspects of general vibration analysis. In this paper, a new experimental damping identification method, which can be able to identify both viscous and structural damping in the dynamic system, is proposed. The proposed method is a direct method and gives explicit structural and viscous damping matrices. The proposed method requires prior knowledge of accurate mass and stiffness matrices. So, experimental viscous-structural damping is identified in two steps. In the first step, mass and stiffness matrices are updated and subsequently viscous and structural damping matrices are identified using updated mass and stiffness matrices obtained in Step 1. The identified viscous-structural damping matrices are both symmetric and positive definite. The effectiveness of the proposed structural damping identification method is demonstrated by numerical and experimental examples. First, two numerical study of lumped mass system and fixed-fixed beam are presented which is followed by an experimental example of cantilever beam. The effects of coordinate incompleteness and different level of damping are investigated. The results have shown that the proposed method is able to identify accurately both viscous and structural damping in the dynamic system.
Damping matrix
Viscous damping
Structural system
Added mass
Identification
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