Jean W. Zu

A Magnetoelectric Generator for Energy Harvesting From the Vibration of Magnetic Levitation

Vibration-based energy harvester has been widely studied during the past years. In order to improve the power-generating ability and enlarge the frequency range of energy harvesters, this paper presents the design and analysis of a new magnetoelectric energy harvester that uses Terfenol-D/PZT/Terfenol-D laminate to harvest energy from nonlinear vibrations created by magnetic levitation. The mathematical model of the proposed harvester is derived and used in a parametric study. Time-domain numerical results of the systems mechanical and electrical responses are obtained and discussed. It is shown that, due to the high energy density and strong magneto-mechanical coupling effect of magnetostrictive material, the proposed harvester is capable of generating very high voltage and power at low frequency ranges.

Design and Analysis of a Hybrid Mobile Robot Mechanism With Compounded Locomotion and Manipulation Capability

This paper presents a novel design paradigm as well as the related detailed mechanical design embodiment of a mechanically hybrid mobile robot. The robot is composed of a combination of parallel and serially connected links resulting in a hybrid mechanism that consists of a mobile robot platform for locomotion and a manipulator arm for manipulation. Unlike most other mobile robot designs that have a separate manipulator arm module attached on top of the mobile platform, this design has the ability to simultaneously and interchangeably provide locomotion and manipulation capability. This robot enhanced functionality is complemented by an interchangeable track tension and suspension mechanism that is embedded in some of the mobile robot links to form the locomotion subsystem of the robot. The mechanical design was analyzed with a virtual prototype that was developed with MSC ADAMS software. The simulation was used to study the robots enhanced mobility characteristics through animations of different possible tasks that require various locomotion and manipulation capabilities. The design was optimized by defining suitable and optimal operating parameters including weight optimization and proper component selection. Moreover, the simulation enabled us to define motor torque requirements and maximize end-effector payload capacity for different robot configurations. Visualization of the mobile robot on different types of virtual terrains such as flat roads, obstacles, stairs, ditches, and ramps has helped in determining the mobile robots performance, and final generation of specifications for manufacturing a full scale prototype.

Enhanced buckled-beam piezoelectric energy harvesting using midpoint magnetic force

Aiming to improve the functionality of a buckled-beam piezoelectric energy harvester, a midpoint magnetic force is utilized to enable snap-through motions under low-frequency (<30 Hz) small-amplitude (0.2 g–0.8 g) excitations. The noncontact midpoint magnetic force is introduced through a local magnetic levitation system created by neodymium magnets and is capable of triggering the second buckling mode that helps the beam easily snap through between equilibriums when subjected to excitations. Significant enhancements, along with distinct nonlinear phenomena, are observed at low frequencies in terms of large-amplitude voltage output and extended frequency bandwidth. Frequency tuning is also achievable by adjusting the separation distance between magnets.

Design and development of a broadband magnet-induced dual-cantilever piezoelectric energy harvester

In this article, a broadband magnet-induced dual-cantilever piezoelectric energy harvester is designed and developed. The dual-cantilever structure consists of an outer and an inner beams with magnets attached to the tips. The magnets generate nonlinear repulsive force between the two beams and make the structure bistable. In the theoretical model, each beam is considered as a single-degree-of-freedom system with magnetic force applied at the free end. From the simulation results, chaotic motion is observed in a wide frequency range. A prototype of the harvester is built and verified with the simulation results. The simulation and experimental results show good agreement with respect to the power bandwidth and amplitude. The distance between magnets is adjusted to observe its effect on the power response of the harvester. The inner and outer beams are simulated and tested independently first to observe the performance of each beam. Finally, an interface circuit is designed to combine all piezoelectric plates to acquire the overall performance. By comparing with the traditional piezoelectric energy harvester, the new design is shown to provide a significant improvement in bandwidth.

Design, simulations and optimization of a tracked mobile robot manipulator with hybrid locomotion and manipulation capabilities

This paper presents a new mobile robot design based on hybridization of the mobile platform and manipulator arm as one entity for robot locomotion as well as manipulation. The novel mechanical design is described in detail. To analyse the design, a virtual prototype tool was developed with ADAMS software for multi-body dynamic motion simulations of the complete robotic system. The simulation results were used to study the robots mobility characteristics through animations of different possible tasks that require various locomotion and manipulation capabilities. The ability to visualize and validate various robot mobility cases and to study its functionality in the early design stages aided in optimizing the design and hence dramatically reduce physical prototype development time and cost. The design optimization process also involved proper components selection. Moreover, the simulations enabled us to define motor torque requirements and maximize end-effector payload capacity for different robot configurations.

Vibrations and Stability of an Axially Moving Rectangular Composite Plate

The vibrations and stability are investigated for an axially moving rectangular antisymmetric cross-ply composite plate supported on simple supports. The partial differential equations governing the in-plane and out-of-plane displacements are derived by the balance of linear momentum. The natural frequencies for the in-plane and out-of-plane vibrations are calculated by both the Galerkin method and differential quadrature method. It can be found that natural frequencies of the in-plane vibrations are much higher than those in the out-of-plane case, which makes considering out-of-plane vibrations only is reasonable. The instability caused by divergence and flutter is discussed by studying the complex natural frequencies for constant axial moving velocity. For the axially accelerating composite plate, the principal parametric and combination resonances are investigated by the method of multiple scales. The instability regions are discussed in the excitation frequency and excitation amplitude plane. Finally, the axial velocity at which the instability region reaches minimum is detected.

Simulations of transverse vibrations of an axially moving string: a modified difference approach

A modified finite difference approach to simulate transverse vibrations of an axially moving string is presented. The stress is treated as a new unknown in discretization of the spatial variable. A set of differential-algebraic equations is established based on the discreted governing equation and the constitutive relation. For linear vibrations, a conserved functional is employed to test the algorithm, and the 1, 2, 3, 4-term truncated modal analytical solutions are compared with the numerical solution. For the free nonlinear vibration, a new conserved functional is used to check the algorithm. Effects of the transport speed on the free and forced nonlinear vibrations are numerically investigated.

Nonlinear vibration of parametrically excited viscoelastic moving belts. Part II : Stability analysis

The amplitude and existence conditions of nontrivial limit cycles are derived in the companion paper by the use of the method of multiple scales. In this paper, the stability for parametrically excited viscoelastic moving belts is studied. Stability boundaries of the trivial limit cycle for general summation parametric resonance are obtained. The Routh-Hurwitz criterion is used to investigate the stability of nontrivial limit cycles. Closed-form expressions are found for the stability of nontrivial limit cycles of general summation parametric resonance. It is shown that the first limit cycle is always stable while the second limit cycle is always unstable for the viscoelastic moving belts. The effects of viscoelastic parameters, excitation frequencies, excitation amplitudes, and axial moving speeds on stability boundaries are discussed.

Modeling of dry stiction in micro electro-mechanical systems (MEMS)

Stiction, a term commonly used in micro electro-mechanical systems (MEMS) to refer to adhesion, is a major failure mode in MEMS. Undesirable stiction, which results from contact between surfaces, can severely compromise the reliability of MEMS. In this paper, a model is developed to predict the dry stiction between uncharged micro parts in MEMS. In dry stiction the interacting surfaces are assumed to be either hydrophobic or placed in a dry environment. In this condition the van der Waals (vdW) and asperity deformation forces are dominant. Here a model is developed for the vdW force between rough micro surfaces, and the new model is combined with a newly developed multiple asperity point model for the elastic/plastic deformation of rough surfaces in contact to solve the equilibrium condition of the forces. This in turn will yield the equilibrium distance between micro surfaces, using which the apparent work of adhesion can be found. The theory result is compared with the available experimental data from the literature. The developed model can be easily used for design purposes. If the topographic data and material constants are known, the desirable adhesion parameters can be quickly found from the model.

Integrated control of active suspension system and electronic stability programme using hierarchical control strategy: theory and experiment

Integrated vehicle dynamics control has been an important research topic in the area of vehicle dynamics and control over the past two decades. The aim of integrated vehicle control is to improve the overall vehicle performance including handling, stability, and comfort through creating synergies in the use of sensor information, hardware, and control strategies. This paper proposes a two-layer hierarchical control architecture for integrated control of the active suspension system (ASS) and the electronic stability programme (ESP). The upper-layer controller is designed to coordinate the interactions between the ASS and the ESP. While in the lower layer, the two controllers including the ASS and the ESP are developed independently to achieve their local control objectives. Both a simulation investigation and a hardware-in-the-loop experimental study are performed. Simulation results demonstrate that the proposed hierarchical control system is able to improve the multiple vehicle performance indices including both the ride comfort and the lateral stability, compared with the non-integrated control system. Moreover, the experimental results verify the effectiveness of the design of the hierarchical control system.