The Application of Electrode Design in Vibrating Piezoceramic Plate for Energy Harvesting System

The energy harvesting system of piezoceramic plate is studied on the electrode configuration to improve the electromechanical transferring efficiency. The piezoceramic plate is used to perform the vibration characteristics by experimental measurements and finite element method (FEM). Thereafter, the dynamic characteristics and the electromechanical coupling efficiency of the piezoelectric energy harvesting system are studied by the electrode design method of the piezoceramic plate. Several experimental techniques are used to measure the dynamic characteristics of piezoceramic plate. First, the full-filed optical technique, amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI), can measure simultaneously the resonant frequencies and mode shapes for out-of-plane and in-plane vibrations. Second, the pointwisely measuring system, laser Doppler vibrometer (LDV), can obtain resonant frequencies by dynamic signal swept-sine analysis. Third, the correspondent in-plane resonant frequencies and anti-resonant frequencies are obtained by impedance analysis. The experimental results of vibration characteristics are verified with numerical calculations. Besides the dynamic characteristics of piezoceramic plates are analyzed in converse piezoelectric effect, the direct piezoelectric effect of piezoceramic plates are excited by shaker to generate the electric voltage. It has excellent consistence between resonant frequencies and mode shapes on the vibration characteristics by experimental measurements and finite element numerical calculations. In this study, the Electrical Potential Gradient (EPG) calculated by FEM is proposed to evaluate the electromechanical coupling efficiency of piezoceramic plate on the specific vibration mode. The correspondent electrode configuration, which is designed by EPG, can produce the best electromechanical transfer both in direct and converse piezoelectric effects. It is concluded that the vibration characteristics of piezoelectric materials have excellent consistence determined by experimental measurements and FEM.

Damage Identification in Collocated Structural Systems Using Structural Markov Parameters

This paper presents a novel approach to damage identification in a class of collocated multi-input multi-output structural systems. In the proposed approach, damage is identified via the structural Markov parameters obtained from a system identification procedure, which is in turn exploited to localize and quantify damage by evaluating relative changes occurring in the mass and stiffness matrices associated with the structural system. To this aim, an explicit relationship between structural Markov parameters versus mass and stiffness matrices is developed. The main strengths of the proposed approach are that it is capable of quantitatively identifying the occurrence of multiple damages associated with both mass and stiffness characteristics in the structural system, and it is computationally efficient in that it is solely based on the structural Markov parameters but does not necessitate costly calculations related to natural frequencies and mode shapes, making it highly attractive for structural damage detection and health monitoring applications. Numerical examples are provided to demonstrate the validity and effectiveness of the proposed approach.

Centroidal Area-Constrained Partitioning for Robotic Networks

We consider the problem of optimal coverage with area-constraints in a mobile multi-agent system. For a planar environment with an associated density function, this problem is equivalent to dividing the environment into optimal subregions such that each agent is responsible for the coverage of its own region. In this paper, we design a continuous-time distributed policy which allows a team of agents to achieve a convex area-constrained partition of a convex workspace. Our work is related to the classic Lloyd algorithm, and makes use of generalized Voronoi diagrams. We also discuss practical implementation for real mobile networks. Simulation methods are presented and discussed.

The Dubins Traveling Salesperson Problem With Stochastic Dynamics

Motivated by applications in which a nonholonomic robotic vehicle should sequentially hit a series of waypoints in the presence of stochastic drift, we formulate a new version of the Dubins vehicle traveling salesperson problem. In our approach, we first compute the minimum expected time feedback control to hit one waypoint based on the Hamilton-Jacobi-Bellman equation. Next, minimum expected times associated with the control are used to construct a traveling salesperson problem based on a waypoint hitting angle discretization. We provide numerical results illustrating our solution and analyze how the stochastic drift affects the solution.

Polymer Flow Control in Continuous Gravimetric Blenders

In this paper, the design of a plastic flow control system for continuous gravimetric blenders used in polymer extrusion processes is discussed. The considered plant is a blending machine that mixes four different polymers, bulks and additives. In order to pursue the desired behavior, three control objectives are considered: plastic flow estimation based on weight and screw speed measurements, plastic flow regulation for each meter and control of the recipe with mass constraints such that the mixer can always satisfy the plastic flow variation needed by the extruder. Simulation results are used to show the effectiveness of the proposed approach.

A Comparison of the Simulated Dynamics of Various Models Used to Predict Undeformed Chip Thickness in High-Speed Low-Radial-Immersion Milling Processes

Various models have been proposed to estimate the undeformed thickness of chips produced by a CNC milling tool, in order to calculate the forces acting on the tool. The choice of model significantly affects the simulated dynamics of the tool, thereby affecting the dynamic stability of the simulated process and whether or not chatter occurs in a given cutting scenario. Simulations of the dynamics of the milling process can be used to determine the conditions at which chatter occurs, which can lead to poor surface finish and tool damage. The dynamics of a traditional model and a more detailed numerical model are simulated here with particular emphasis on the differences in their chatter bifurcation points. High-speed, low-radial-immersion milling processes are simulated because of their application in industrial high-precision machining.

Interaction Control for Rehabilitation Robotics via a Low-Cost Force Sensing Handle

This paper investigates the possibility of implementing force-feedback controllers using measurement of interaction force obtained through force-sensing resistors (FSRs), to improve performance of human interacting robots. A custom sensorized handle was developed, with the capability of simultaneously measuring grip force and interaction force during robot-aided rehabilitation therapy. Experiments are performed in order to assess the suitability of FSRs to implement force-feedback interaction controllers. In the force-feedback control condition, the applied force for constant speed motion of a linear 1DOF haptic interface is reduced 6.1 times compared to the uncontrolled condition, thus demonstrating the possibility of improving transparency through force-feedback via FSRs.

Detection of Contact-Type Damages by Utilizing Nonlinear Piezoelectric Impedance Modulation of Self-Excited Structures

This paper presents an improvement of a nonlinear piezoelectric impedance modulation (NPIM)-based damage detection method, a damage-sensitive, baseline-free structural health monitoring technique proposed by the authors, by introducing self-excited oscillation. The NPIM-based damage detection utilizes the modulation of high-frequency wave field of structures caused by the contact acoustic nonlinearity at the damaged part. In this study, the high-frequency wave field is induced as a self-excited oscillation of the structure by positively feed-backing the strain signal measured by a surface-bonded piezoelectric sensor, followed by a phase-shift in 90 degrees and a nonlinear element consisting of a saturation element and a negative linear gain. The induced self-excitation can have multiple stable limit cycles at certain eigenmode frequencies, and one can switch among them by inputting an auxiliary excitation signal into the feedback loop. The current flowing through the piezoelectric sensor is measured to detect its modulation due to the stiffness fluctuation due to the existence of the contact-type damage. Experiments using a specimen with a simulated damage are conducted to examine the performance of the self-excitation circuit and its applicability to the NPIM-based damage detection method.

Maximum Power Estimation of Lithium-Ion Batteries Accounting for Thermal and Electrical Constraints

Enforcement of constraints on the maximum deliverable power is essential to protect lithium-ion batteries from over-charge/discharge and overheating. This paper develops an algorithm to address the often overlooked temperature constraint in determining the power capability of battery systems. A prior knowledge of power capability provides dynamic constraints on currents and affords an additional control authority on the temperature of batteries. Power capability is estimated using a lumped electro-thermal model for cylindrical cells that has been validated over a wide range of operating conditions. The time scale separation between electrical and thermal systems is exploited in addressing the temperature constraint independent of voltage and state-of-charge (SOC) limits. Limiting currents and hence power capability are determined by a model-inversion technique, termed Algebraic Propagation (AP). Simulations are performed using realistic depleting currents to demonstrate the effectiveness of the proposed method.

Theoretical Development and Experimental Validation of an Adaptive Controller for Tremor Suppression at Musculoskeletal Level

Tremor is a rhythmical and involuntary oscillatory movement of a body part. Mechanical loading via wearable exoskeletons is a non-invasive tremor suppression alternative to medical treatments. In this approach, the challenge is attenuating the tremor without affecting the patient’s intentional motion. An adaptive tremor suppression algorithm was designed to estimate and restrict motion within the tremor frequency band. An experimental setup was designed and developed to simulate the dynamics of a human arm joint with intentional and tremorous motion. The required orthotic suppressive force was applied via a pneumatic cylinder. The algorithm was implemented with a real-time controller and experimental results show tracking of the tremor frequency and a 97% reduction of tremor amplitude at the fundamental frequency.