High Frequency Analysis of a Dynamically Coupled Parallel Plate System

The behavior of a system comprised of two parallel plates coupled by a discrete, linear spring and damper is studied. Classical Modal Analysis (CMA) is used to illustrate this behavior, while specifically observing the effects of varying the stiffness and damping ratio of the coupling elements. Conditions under which the coupling may be approximated as rigid are identified. Additionally, conditions under which the coupling displacement reaches its maximum and minimum values are identified. This work also lays the groundwork for extending Asymptotic Modal Analysis (AMA) to systems with discrete, elastic, and dissipative coupling.

Modified Zero Time Delay Input Shaping for Industrial Robot With Flexibility

Although input shaping is an effective approach for vibration suppression in a variety of applications, the time delay introduced is not desired. Current techniques to reduce the time delay can not guarantee zero delay or may cause non-smooth motion, which is harmful for the actuators. In order to address such issue, a modified zero time delay input shaping is proposed in this paper. Experimental results show the advantage of the proposed approach.

Physics-Based Friction Model With Potential Application in Numerical Models for Tire-Road Traction

Good understanding of friction in tire-road interaction is of critical importance for vehicle dynamic control systems. Most of the friction models proposed to describe the friction coefficient between tire-treads and road surfaces have been developed based on empirical or semi-empirical relations that are not able to include many effective parameters involved in the tire-road interactions. Therefore, these models are just useful in limited conditions similar to the experiments, and do not accurately represent tire-road traction in numerical tire models. However, in last two decades, a few theoretical models have been developed to calculate the tire-road friction coefficient theoretically by considering both viscoelastic behavior of tire tread compounds and multi-scale interactions between tire treads and rough road surfaces. In this article, a novel physics-based model proposed by Persson has been investigated and used to develop computer algorithms for calculation of sliding friction coefficient between a tire tread compound and a rough substrate. The viscoelastic behavior of tread compound and the surface profile of rough counter surface are the inputs of this physics-based theoretical model. The numerical results of the model have been compared with the experimental results obtained from a dynamic friction tester designed and built in the Center for Tire Research (CenTire). Good agreement between numerical results of theoretical model and experimental results has been found at intermediate range of slip velocities considering the effect of adhesion and shearing in the real contact area in addition to hysteresis friction due to internal energy dissipation in the tire tread compound.

Detection of Vehicle Tripped and Untripped Rollovers by a Novel Index With Mass-Center-Position Estimations

This paper presents a novel mass-center-position (MCP) metric for vehicle rollover propensity detection. MCP is first determined by estimating the positions of the center of mass of one sprung mass and two unsprung masses with two switchable roll motion models, before and after tire lift-off. The roll motion information without saturation can then be provided through MCP continuously. Moreover, to detect completed rollover statues for both tripped and untripped rollovers, the criteria are derived from d’Alembert principle and moment balance conditions based on MCP. In addition to tire lift-off, three new rollover statues, rollover threshold, rollover occurrence, and vehicle jumping into air can be all identified by the proposed criteria. Compared with an existing rollover index, lateral load transfer ratio, the fishhook maneuver simulation results in CarSim® for an E-class SUV show that MCP metric can successfully predict the vehicle impending rollover without saturation for untripped rollovers. Tripped rollovers caused by a triangle road bump are also successfully detected in the simulation. Thus, MCP metric can be successfully applied for rollover propensity prediction.

Real-Time Optimization of Wind Farm Energy Capture With Delay Compensated Nested-Loop Extremum Seeking Control

Real-time optimization of wind farm energy capture for below rated wind speed is critical for reducing the levelized cost of energy (LCOE). Performance of model based control and optimization techniques can be significantly limited by the difficulty in obtaining accurate turbine and farm models in field operation, as well as the prohibitive cost for accurate wind measurements. The Nested-Loop Extremum Seeking Control (NLESC), recently proposed as a model free method has demonstrated its great potential in wind farm energy capture optimization. However, a major limitation of previous work is the slow convergence, for which a primary cause is the low dither frequencies used by upwind turbines, primarily due to wake propagation delay through the turbine array. In this study, NLESC is enhanced with the predictor based delay compensation proposed by Oliveira and Krstic [1], which allows the use of higher dither frequencies for upwind turbines. The convergence speed can thus be improved, increasing the energy capture consequently. Simulation study is performed for a cascaded three-turbine array using the SimWindFarm platform. Simulation results show the improved energy capture of the wind turbine array under smooth and turbulent wind conditions, even up to 10% turbulence intensity. The impact of the proposed optimization methods on the fatigue loads of wind turbine structures is also evaluated.

Development of a Mechatronics Course Integrated With Lab

This paper reports the development of an introductory mechatronics course in Mechanical Engineering (ME) undergraduate program at Georgia Southern University. This an updated version of an existing required course in the ABET accredited BSME program. The course covers three broad areas: mechatronic instrumentation, computer based data acquisition and analysis, and microcontroller programming and interfacing. This is a required 3-credit course in the ME program with updated computing application specific content reinforcing theoretical foundation with hands-on learning activities of the existing course. The course has four contact hours per week with two hours of lecture and two hours of interactive session of problem solving and laboratory experiment. For each topic covered, students get the theoretical background and the hands-on experience in the laboratory setting. Both formative and summative assessment of the students’ performance in the course are planned. Both direct and indirect forms of assessment are considered. The paper reports the details of the course materials.

Parametric Resonance of Electrostatically Actuated MEMS Cantilever Resonators Using Method of Multiple Scales and Homotopy Perturbation Method

This paper investigates the dynamics governing the behavior of electrostatically actuated MEMS cantilever resonators. The cantilever is held parallel to a ground plate (electrode) with an AC voltage between the plate and the electrode causing the electrostatic actuation (excitation). For the purposes of this paper this is soft excitation. The frequency of the excitation is near the natural frequency of the cantilever leading to what is known as parametric resonance. The electrostatic force in the problem investigated throughout the paper is nonlinear in nature and includes the fringe effect. Two methods are used in investigating this problem: the method of multiple scales (MMS) and the homotopy perturbation method (HPM). The two methods work well for small non-linearities and small amplitudes. The influence of voltage, fringe, damping, Casimir, and Van der Waals parameters will be investigated in this paper using MMS and HPM as a means of verifying the results obtained.

An Inductive, Design-Centric Approach to Control Engineering Education With a Competitive Atmosphere

Control engineering is a cornerstone of most undergraduate engineering programs in colleges and universities around the world. The analysis and synthesis of automatic controllers, in particular, the PID controller, is a central focus of these courses and modules. However, due to its highly abstract nature, students usually find the content challenging and difficult to comprehend. This is aggravated by the employment of traditional lecture/recitation deductive teaching formats as means of delivery of the content. Here, an inductive-based week long design activity strategically held in the middle of the semester was conceived to introduce and motivate the notion of feedback control. During the course of the week, students in teams design, analyze and synthesize automatic controllers to enable a standardized differential wheeled robotic platform to traverse a line circuit autonomously. The strategy to achieve this capability is intentionally left to be open-ended, and students have the design freedom to select and position sensors needed to sense the track, as well as implement and troubleshoot the programming required to enable autonomous control. The activity culminates with a pulsating head-to-head single elimination tournament to decide the overall champion.

A Framework of Control-Oriented Reaction-Based Model for Trajectory-Based HCCI Combustion With Variable Fuels

A novel combustion control, i.e. the trajectory-based combustion control, was proposed previously. This control is enabled by free piston engines (FPEs) and utilizes the FPE’s controllable piston trajectory to enhance thermal efficiency, reduce emissions and realize variable fuels applications. On top of that, a control-oriented model was also developed aimed to implement the trajectory-based combustion control in real-time. Specifically, a unique phase separation method was proposed in the model, which separates an engine cycle into four phases (pure compression, ignition, heat release and pure expansion) and employs the minimal reaction mechanism accordingly. In this paper, the framework of the previous control-oriented model is extended to variable fuels, such as methane, n-heptane and bio-diesel. Such an extension is reasonable since the separated four phases are representative in typical combustion processes of all fuels within an engine cycle. Besides, a least-squares optimization is formulated to calibrate the chemical kinetics variables for each fuel. At last, simulation results and the related analysis show that all the derived control-oriented models have high fidelity and much lighter computational burdens to represent the HCCI combustion of each fuel along variable piston trajectories.

Under-Actuated Humanoid Model With Elastomeric Springs

This paper presents the mechanical modifications and simulation of a bipedal humanoid system actuated with linear springs to produce a standing equilibrium position. The original humanoid system is comprised of two leg assemblies connected by a hip bracket. Eleven pairs of springs were attached to the system in locations designed to simulate the muscles and tendons in a human body. The next evolution of the LUIGEE project is the inclusion of three servo motors per leg and a series of elastomeric springs. Although servo motors have been introduced, it is desired to maintain the passive, static aspect of the previous prototype. This paper reports on part modifications to accommodate servo motors and the introduction of polymeric springs that guarantee static stability. ABS plastic and photopolymer resin was used to produce the new model. Due to the size of the motors, some parts of the original robot were redesigned. The new design iteration was stimulated using SimWise 4D®, where the hysteretic effect of rubber was modelled with an equivalent viscous damping.