Arnold Lumsdaine

Topology Optimization of Constrained Damping Layer Treatments

The aim of this research is to determine the optimal shape of a constrained viscoelastic damping layer on an elastic beam by means of topology optimization. The optimization objective is to maximize the system loss factor for the first resonance frequency of the base beam. All previous optimal design studies on viscoelastic lamina have been size or shape optimization studies, assuming a certain topology for the damping treatment. In this study, this assumption is relaxed, allowing an optimal topology to emerge. The loss factor is computed using the Modal Strain Energy method in the optimization process. Loss factor results are validated by using the half-power bandwidth method, which requires obtaining the forced response of the structure. The ABAQUS finite element code is used to model the structure with two-dimensional continuum elements. The optimization code uses a Sequential Quadratic Programming algorithm. Results show that significant improvements in damping performance, on the order of 100% to 300%, are obtained by optimizing the constrained damping layer topology. A novel topology for the constraining layer emerges through the optimization process.Copyright

Dynamic modeling and analysis of a transmission-based robot servoactuator

This paper addresses aspects of the feasibility of extending high performance brushless DC motor torque-speed capabilities by using multi-speed transmissions. Initial dynamic modeling and simulation results show that a transmission-based electrical servo actuator can have similar load capabilities with widely used hydraulic actuator in robot manipulators.

Design and testing of a prototype transmission-based robot servoactuator

A novel actuator concept has been developed and prototyped. By integrating a multi-speed transmission with a high performance permanent magnet DC servomotor, it has been shown that an electrical drive can provide power/torque density and physical size that approaches the capabilities of electrohydraulics. Preliminary experimental tests of the prototype are encouraging and the first steps toward verifying the concept.

Topology Optimization of a Piezoelectric Actuator on an Elastic Beam

The purpose of this study is to investigate the optimal topology of a piezoelectric actuator in reducing the tip deflection of a static cantilever beam under a concentrated tip load. Optimized topologies are obtained for both statically loaded and harmonically excited cases. The beam is modeled using the commercial finite element code ABAQUS, and a proportional control law is implemented through modification of the stiffness matrices. Parameter studies varying the gain and volume of the piezoelectric material are conducted. Optimal topologies show substantial improvement over equivalent uniform piezoelectric layers. This study also demonstrates the possibility of using a commercial FE code for studying structural control with piezoelectric materials.

Design of Constrained Layer Damping Topologies

The aim of this research is to determine the optimal topologies for viscoelastic lamina used for vibration damping. The optimization objective is to maximize the system loss factor for the first resonance frequency of a base structure. Previous optimal design studies examining viscoelastic lamina have been size or shape optimization studies, assuming a certain topology for the damping treatment. In this study, the topology is optimized to maximize vibration damping levels. The loss factor is computed using the Modal Strain Energy method in the optimization process. For the initial and optimal topologies, the loss factor results are validated by using the half-power bandwidth method, which requires obtaining the forced response of the structure. The ABAQUS finite element code is used to model the structure with two-dimensional, plane stress, continuum elements. The optimization code uses a Sequential Quadratic Programming algorithm. This study extends the results of a previous study by Lumsdaine (2002) by examining the effects of a number of parameters on the optimal damping levels and the optimal topologies. The parameters examined include the total elastic and viscoelastic material fractions and the base beam thickness. Results show that significant improvements in damping performance, over 300% in some cases, are obtained by optimizing the constrained damping layer topology.© 2003 ASME

Design and fabrication of optimal constrained layer damping topologies

Of the many methods available for achieving effective vibration damping, adding viscoelastic lamina constrained by a stiff elastic materials is an inexpensive, space efficient means for achieving significant damping levels. Recently, the desire to apportion this material in a way that will take the greatest advantage of its dissipative characteristics has led to studies in optimization1-7. The aim of this research is to determine the optimal shape of a constrained viscoelastic layer on an elastic beam used for vibration damping by means of topology optimization and to experimentally verify these results. The optimization objective is to maximize the system loss factor for the first resonance frequency of the base beam. All previous optimal design studies on viscoelastic lamina have been size or shape optimization studies assuming a certain topology for the damping treatment (with the exception of Lumsdaine8 and Lumsdaine and Pai9, of which this work is an extension). In this study, this assumption is relaxed, allowing an optimal topology to emerge. The loss factor is computed using the Modified Modal Strain Energy Method10 in the optimization process. It is observed that a novel topology emerges from the optimized result. From this computational result, a topology is interpreted that can be reasonably manufactured, and this topology is custom fabricated to experimentally validate the computational result. The experimental results show that significant improvement in damping performance, over 300%, is obtained by optimizing the constrained damping layer topology.

Active vibration control with optimized piezoelectric topologies

This paper investigates the optimal topology of an actively controlled piezoelectric actuator bonded to an elastic cantilever beam under steady-state harmonic loading. The actuator is discretized using finite elements, and control is applied to the actuator based on the sensors degrees of freedom using proportional control. This study investigates the optimal distribution of actuator material for one and five layers of finite elements. The optimized actuator topology shows substantial improvement over initial piezoelectric topologies and over traditional actuator placement.

Design of a piezoelectric actuator using topology optimization

This study investigates the optimal topology for a piezoelectric actuator mounted on a cantilever beam under a concentrated static load at the tip. The project consists of two major parts: implementation of the control law into the commercial finite element code ABAQUS and studies in topology optimization. The first part gives a derivation and explanation of the implementation of static feedback control. The result is compared with a derived analytical solution. The second part examines the results of topology optimizations with different geometries and constraints. Thus, this study develops fundamental understanding of advantageous shapes for optimal performing piezoelectric actuators.

Analysis and Optimization of Partial Constrained Damping Layers

Topology optimization has been used to maximize the damping performance of constrained damping layer structures with viscoelastic core [1-3]. Studies show that using nanotubes as reinforcements in polymer material might improve the damping and stiffness properties [4,5]. Experimental investigations using nanotube reinforcements in constrained damping layers showed a significant improvement in damping properties of the structure [6]. Optimizing the topology of structures involving nanotube reinforcements can further enhance the damping properties by making optimal use of the nanotubes as reinforcements. In preliminary studies performed with volume fraction of nanotubes as a design variable in the optimization [7,8] substantial improvements in the damping properties were observed. In this work, the topology of a cantilever beam structure involving nanotube reinforced polymer layers is optimized with the objective of maximizing the system loss factor for the first resonance frequency of the base beam. The volume fractions and orientations of the nanotubes in each finite element and the material fraction of the nanotube reinforced polymer (NRP) and the elastic material are the design variables in the optimization process. ABAQUS is used for the finite element modeling and an optimization code NLPQL which uses a sequential quadratic programming algorithm is used for the optimization.Copyright

Determination of Optimal Orientations and Volume Fractions of Nanotubes in a Polymer for Vibration Damping

Topology optimization has been used to maximize the damping performance of constrained damping layer structures with viscoelastic core [1-3]. Studies show that using nanotubes as reinforcements in polymer material might improve the damping and stiffness properties [4,5]. Experimental investigations using nanotube reinforcements in constrained damping layers showed a significant improvement in damping properties of the structure [6]. Optimizing the topology of structures involving nanotube reinforcements can further enhance the damping properties by making optimal use of the nanotubes as reinforcements. In preliminary studies performed with volume fraction of nanotubes as a design variable in the optimization [7,8] substantial improvements in the damping properties were observed. In this work, the topology of a cantilever beam structure involving nanotube reinforced polymer layers is optimized with the objective of maximizing the system loss factor for the first resonance frequency of the base beam. The volume fractions and orientations of the nanotubes in each finite element and the material fraction of the nanotube reinforced polymer (NRP) and the elastic material are the design variables in the optimization process. ABAQUS is used for the finite element modeling and an optimization code NLPQL which uses a sequential quadratic programming algorithm is used for the optimization.Copyright