The energy method for analyzing the piezoelectric electroacoustic transducers

Experimental confirmation of the possibility of real-time measurement of the internal (deep) temperature of a biological object by thermal acoustic radiation with an accuracy of at least 0.2 °C using an acoustic thermometer implementing the modified zero modulation method is obtained. The model of a single-channel passive noninvasive focussed acoustic thermometer based on a plate piezoceramic electro-acoustic transducer, acoustic elliptical lens and blocks of two serial voltmeters is developed. Electronic switching of the output signals of the noise simulator and the equivalent circuit of the focused piezoelectric transducer is proposed, when resistance generates thermal noise with an intensity equal to the sum of intensities of acoustic radiation of the biological object and natural noise of the piezoelectric transducer. This circuitry solution made it possible to exclude the mechanical modulator (shutter) unit used in analogs from the acoustic thermometer circuit. When developing the original switching and detection unit, it was proposed to use the key mode of n-channel field-effect transistors to perform modulation of the input noise signal. Calculation of equivalent circuits of the piezoelectric electroacoustic transducer and noise simulator, which are connected circuits with a bandwidth in which the average noise voltage level is determined by the noise voltage at the electric resonance frequency of the piezoelectric element, is performed. The possibility of using the model of the single-channel passive noninvasive focussed acoustic thermometer, constructed according to the circuit implementing the modified zero modulation method, for measuring noise voltages in the range from 5 to 30 μV is proved. Since the process of manufacturing or operating a piezoceramic electroacoustic transducer may lead to a deviation of its parameters from theoretically calculated, a method is developed to measure the frequency response of the active and reactive components of electrical impedance. Using the proposed method, the assembly quality of the focused piezoelectric electro-acoustic transducer is monitored and the temperature dependence of electric noise voltage at the electrodes of the focused piezoelectric receiver is obtained.

In the article highlights the infusion of additional structural elements into the characteristics of a piezoelectric electroacoustic transducer, leading to the breakdown of the structure, as well as their straightness diagrams. The major tasks of ultrasonic measuring systems are sound waves concentrated sending to the controlled object and reflected waves receiving. Electro-acoustic transducer is an oscillating system with a sufficiently high quality factor and contains an asymmetric bimorph element. The considered butts of improving the sensitivity of the central beam of the electroacoustic transducer added to the design volumetric resonator. Directional effect of concentration can be obtained using the irradiator as Helmholtz resonator consisting of bimorph piezoelectric resonator and tube of required length and diameter, which orients sound beam on the acoustic axis of the electroacoustic transducer. An example of improving the selectivity of the central lobe electroacoustic transducer is adding additional cavity resonator to the construction of the piezoelectric transducer. Further research can be carried out directly based on mathematical models for various design circuits of piezoelectric transformers. Important tasks in the design and development of the main components of ultrasonic vibrating devices are considered. The main advantages and shortcomings of the ultrasonic signal-receiving path have analyzed, in which electroacoustic converters combined with additional structural elements for ultrasonic vibrating systems to ensure autonomous vicination specification of the design parameters and military technology in open areas and intersections.

In this paper, we further investigate the construction of a phase space dividing surface (DS) from a normally hyperbolic invariant manifold (NHIM) and the sampling procedure for the resulting dividing surface described in earlier work ( Wiggins , S. ; J. Chem. Phys. 2016 , 144 , 054107 ). Our discussion centers on the relationship between geometrical structures and dynamics for 2 and 3 degree of freedom (DoF) systems, specifically, the construction of a DS from a NHIM. We show that if the equation for the NHIM and associated DS is known (e.g., as obtained from Poincaré-Birkhoff normal form theory), then the numerical procedure described in Wiggins et al. ( J. Chem. Phys. 2016 , 144 , 054107 ) gives the same result as a sampling method based upon the explicit form of the NHIM. After describing the sampling procedure in a general context, it is applied to a quadratic Hamiltonian normal form near an index-one saddle where explicit formulas exist for both the NHIM and the DS. It is shown for both 2 and 3 DoF systems that a version of the general sampling procedure provides points on the analytically defined DS with the correct microcanonical density on the constant-energy DS. Excellent agreement is obtained between analytical and numerical averages of quadratic energy terms over the DS for a range of energies.

The Karhunen-Loeve expansion method has been utilized in the decomposition of random forcing auto-covariance functions. A recent study by the authors provided proof that such a decomposition could be used to nd the response of a SDOF system to non-stationary loading. In this study, the authors are modifying the method to be further generalized and applicable to multi degree of freedom systems. As a rst step the existing method is modi ed by switching from continuous to piecewise constant basis functions. Such a change allows the method to be applied to any covariance function and can demonstrate superior e ciency over continuous functions where the eigenvectors of the covariance function are not well known. The modi cations implemented have been applied to a single degree of freedom system studied previously by the authors and also simple 2DOF systems to keep the derivation process clear. Response due to non-correlated forcing caused by a variety of covariance functions are presented and validated with an analytical solution.

<div class="htmlview paragraph">Many manufacturers utilize statistical methods to control product characteristics during processing. Often traditional x charts are utilized. This method is appropriate when examining characteristics with one degree of freedom. For features with two or more degrees of freedom, traditional x charts may be misleading. Techniques for controlling characteristics with multiple degrees of freedom, however, have not been developed.</div> <div class="htmlview paragraph">The purpose of this paper is to present a method of statistical analysis using radial type charting techniques for characteristics with multiple degrees of freedom. Included in this paper is a detailed discussion of the steps to prepare and interpret radial type charts. These techniques are applied to true position measurements as a specific example.</div>

In this paper we discuss the partial feedback linearization control of underactuated mechanical systems. We consider an n degree of freedom system having m actuated, or active, degrees of freedom and l=n-m unactuated, or passive, degrees of freedom. It is known that the portion of the dynamics corresponding to the active degrees of freedom may be linearized by nonlinear feedback. In this paper we show, alternatively, that the portion of the dynamics corresponding to the passive degrees of freedom may be linearized by nonlinear feedback under a condition that we call strong inertial coupling. We derive and analyze the resulting zero dynamics which are crucial to an understanding of the response of the overall system. Simulation results are presented showing the performance of two link underactuated robots under partial feedback linearization control. >

The DEKA training protocol we developed includes training in skilled unilateral movements with the prosthesis. This approach represents a shift away from prosthetic rehabilitation programs that focus solely on use of the prosthesis as an assist. our view is that an advanced prosthesis, like the DEKA arm, should assume the role of a nondominant limb, which is capable of skilled activity, though generally less adept than the dominant limb. INTRODUCTION There is a scarcity of literature on rehabilitation training protocols for upper-limb prosthesis use. Seminal textbooks and articles describe protocols for training individuals to use conventional body-powered, myoelectric, or passive prosthetic devices and were written prior to the introduction of multifunction prosthetic hands and more advanced prosthetic technologies [1-3]. Furthermore, detailed descriptions of training protocols for individuals with shoulder disarticulations or forequarter amputations are particularly limited, with little emphasis on this level of amputation [4]. Two case studies described rehabilitation at this amputation level using cosmetic or body-powered prostheses with single degree of freedom (DOF) terminal devices [5-6]. In 2008, Smurr et al. published an updated training protocol for people with upper-limb amputation that highlighted the process of controls training for body-powered and myoelectric prosthesis users by level of amputation [7]. Stubblefield et al. presented an occupational therapy training protocol specific to patients undergoing targeted muscle reinnervation surgery [8]. Previously published prosthetic rehabilitation protocols do not address prosthetic training with the advanced prostheses that have become available and include multifunction hands, powered prostheses with multiple DOFs, and/or powered shoulder joints. The most widely tested advanced, multifunction prosthesis to date is the DEKA Arm, developed through the Defense Advanced Research Projects Agency's (DARPA's) Revolutionizing Prosthetics program. The DEKA Arm is now in its third generation prototype (Gen 3) and was recently approved by the Food and Drug Administration for commercial marketing. The DEKA Arm is modular and can be configured for three levels: radial configuration (RC) for people with transradial amputation, humeral configuration (HC) for people with transhumeral amputation, and shoulder configuration (SC) for people with transhumeral amputation with very short residuum and persons with amputations at the shoulder disarticulation and interscapulothoracic (forequarter) level. Features of the SC DEKA Arm with end-point control and foot controls were described in detail in three articles [9-11]. The SC Arm is shown in figure 1. Briefly, the SC Arm has 10 powered DOFs and additional passive DOFs. Prosthetic movements are customized for the user and can employ a combination of foot controls, myoelectric controls, pneumatic bladders (provided by DEKA), or other commonly available prosthetic input elements. All levels of the DEKA Arm use control inputs for the and wrist. The control scheme has dual modes enabling the user to switch between a hand mode of operation for fine motor use and an arm mode of operation to control larger gross movements of the prosthetic arm. Gross movements are operated through endpoint control, which allows simultaneous, coordinated movement of multiple joints to move the terminal device (the end point) to a desired position in space. The Department of Veterans Affairs (VA) has led a study to optimize the DEKA Arm (Optimization Study) since 2008 and is currently leading a study of home use of the device. A synopsis of the general training protocol used in the Optimization Study was presented in two articles [12-13]. Another article describing the virtual reality environment (VRE) portion of the training protocol for the DEKA Arm second generation prototype (Gen 2) reported that VRE training was particularly valuable for people with upper-limb amputation who must master a large number of controls and for those who need a structured learning environment [14]. …

The flexible functions of a human five finger hand with a palm were studied from the viewpoint of force sensory manipulation, unlike the conventional viewpoint of position based manipulation. It was clear that more than half of human hand work is related to force sensory information. Based on this examination, the degree of freedom of an articulated finger hand is determined to realize such a flexible manipulation as a human hand, so that twenty five degrees of freedom are necessary for a hand with consideration of joints inside the palm which have not been taken into account previously. An artificial finger hand with twenty five degrees of freedom was built for experiments by employing a wire and spring mechanism. Finally, an evaluation concept of three dimensional grasping is presented as a crosssection method by calculating applied forces and moments in a plane virtually cut at arbitrary inclined angles around the center of a grasped object.

ABSTRACTHuman involvement with the manual control of object-tracking tasks, such as manual rendezvous and docking, can enhance the flexibility of the task. The operator is required to make decisions as precisely as possible when a chase vehicle is approaching the target vehicle. As the level of mental workload is intensively increased, the operator's perception and decision-making with tracking error-correcting purposes should be properly identified in multiple degrees of freedom (DOFs). The two experimental studies in this paper were conducted for object-based selective attention in six DOFs and object-pointing manipulation under the zero resistance circumstance, which were correlated with human performance when a chaser approached a target spacecraft; the effects of experience level on the two important factors are presented herein. The experimental results demonstrated that some performance details between the novice and experienced groups were different in terms of the attentional priority of multiple DOFs and lateral/vertical movement for deviation error correction, which could provide a certain reference for a cognitive–behavioural model and assist the operator in obtaining proper or even optimal decision-making or operating instructions to improve their adaptation to selective attention and object-pointing manipulation, for preventing accidental manipulation and performance degradation.

Musculoskeletal modeling is a new computational tool to reverse engineer human control systems, which require efficient algorithms running in real-time. Human hand pronation-supination movement is accomplished by movement of the radius and ulna bones relative to each other via the complex proximal and distal radioulnar joints, each with multiple degrees of freedom (DOFs). Here, we report two simplified models of this complex kinematic transformation implemented as a part of a 20 DOF model of the hand and forearm. The pronation/supination DOF was implemented as a single rotation joint either within the forearm segment or separating proximal and distal parts of the forearm segment. Torques produced by the inverse dynamic simulations with anatomical architecture of the forearm (OpenSim model) were used as the "gold standard" in the comparison of two simple models. Joint placement was iteratively optimized to achieve the closest representation of torques during realistic hand movements. The model with a split forearm segment performed better than the model with a solid forearm segment in simulating pronation/supination torques. We conclude that simplifying pronation/supination DOF as a single-axis rotation between arm segments is a viable strategy to reduce the complexity of multi-DOF dynamic simulations.

Durability of Co-bonded Piezoelectric Transducers

All-digital servo system of shipboard tracking radar based on 2DOF (two degrees of freedom) system theory is designed in the paper. The paper puts forward a method of obtaining the feedforward controller of the two degrees of freedom system based on the step response curve of one degree of freedom system. The mathematical model of the servo system is established using MATLAB/Simulink, the two degrees of freedom velocity loop is designed, and the simulation results show that two degrees of freedom controller structure has significant role of enhancing the dynamic performance of the velocity loop, sensitivity function analysis verifies the robustness of the velocity loop. The hardware and software design of the servo system are Completed based on TMS320F28335 DSP, FOG (Fiber Optic Gyroscope) serves as inertial angular rate sensor of the velocity loop, the digital current loop is realized. Isolation experiment and tracking simulated moving target experiment are carried out, the experimental results show that the servo system has good dynamic performance and good disturbance attenuation capability.

The virtual constraints method is used here to design and control the walking-like trajectory of the 4-link having 4 degrees of freedom: stance angle, 2 knees angles and 1 hip angle and 3 actuators only as the stance leg angle is not actuated. Two different approaches are compared. First, the well-known approach consists in setting virtual constraints as the dependencies of knees and hip angles on the stance leg angle. Therefore there are 3 virtual constraints enforced by all 3 available inputs and reducing thereby overall 4 degrees of freedom to a single degree of freedom unactuated system. Selecting suitable constraints functions, various walking-like trajectories can be designed. Secondly, this three constraints approach is compared with the alternative one developed very recently. Here, only two constraints are imposed being dependencies of knees angles on the hip angle thereby reducing the 4-link to 2 degrees of freedom system with a single actuator at the hip angle. Such a system may be naturally called as the generalized Acrobot. Comparison of both approaches is performed by numerical simulation using 4-link mathematical model of real laboratory equipement. In the future, the most suitable method would be selected for the real implementation, in particular, based on the current comparative study.

Torsional vibrations experienced by drill strings can be detrimental to drilling operations. With a goal of understanding torsional vibrations experienced by drill strings and determining means to attenuate undesired vibrations, the authors have studied the effect of adding a sinusoidal modulation to a constant rotation speed of a drill string. A combination of modeling, analysis, and experiments is used to explore the influence of this rotation input modulation on the system response. The drill string is modeled as a modified Jeffcott rotor, which is described by a system with three degrees of freedom. Considering the case of forward whirling of a rotor in continuous contact with a stator, the equations of motion are reduced to a single degree-of-freedom nonlinear oscillator describing the torsional motions. In order to understand the fast time scale and slow time scale components of the motion, the method of direct partitions of motions is used to determine an approximate response to the nonlinear oscillator. The obtained results of the analysis illustrate that with the sinusoidal modulation of the rotor drive speed, the equivalent torsion stiffness can be enhanced and the character of the friction force at the contact can be made smooth. The analyses helps bring forth the stabilizing influence of the added sinusoidal input to the rotor drive speed. Over the considered parameter ranges, the numerical results obtained with the full three degree-of-freedom model and the reduced single degree-of-freedom model are found to be in agreement with each other. Furthermore, the results from these models are found to compare well with those obtained by using the method of direct partition of motions. Experiments with a laboratory scale drill-string arrangement are to be carried out to validate the analytical and numerical findings and further explore the effectiveness of the drive speed modulation on the rotor dynamics. Introduction Slender rotating structures are used in many engineering applications. Drill strings are long rotating slender structures, which are used in drilling operations. A schematic of a rotary drill rig is shown in Fig. 1 (e.g., Liao, Balachandran, Karkoub, and Abdel-Magid, 2011). Drill strings experience different types of vibrations (axial, torsional, and lateral vibrations) that may lead to detrimental failures of a drilling system. Drill-string vibrations have attracted the attention of many researchers, and many models have been developed to understand them. Since drill strings have a large length-to-diameter ratio, typically, the first torsional natural frequency and first lateral natural frequency are close to each other. This frequency proximity and the nature of the system allows for coupling and energy transfer between the associated vibration modes. Here, as a step towards developing further understanding, a drill string is modeled as an extended planar Jeffcott rotor with gravity acting normal to the rotor. Due to the planar motions, no gyroscopic effects are considered. The extended model, which was earlier considered in the work of Vlajic, Liu, Karki, and Balachandran (2014), is shown in Fig. 2. The model is described with three degrees of freedom (DOF), namely, x and y to account for lateral motions, and theta to account for torsional motion. A large number of research efforts have focused on controlling drill-string vibrations by using different feedback control algorithms, which need measurements along the drill string. In this work, the authors propose a different control approach to mitigate whirling motions during continuous rotor-stator contact. This can be compared to a situation of a drill string being in continuous contact with the borehole. The approach is open loop in implementation and this approach is based on adding a high frequency input to the drive speed of the drill string. Given the open-loop nature, the method does not depend on any measurements along the drill string or rotary table, which could be attractive for a practical stand point. Although the current focus is on motions of a rotor with continuous stator contact, it is planned to study stick-slip and non-contact cases in the future. System Modeling, Studies, and Results As previously mentioned, the drill string is modelled as a Jeffcott rotor with three DOF. Proceeding along the lines of the group's prior work (Vlajic, Liu, Karki, and Balachandran, 2014), after some approximations for the continuous rotor-stator contact case, the 3 DOF system is reduced to a single second-order nonlinear differential equation governing the torsional motion. In Fig. 3, for a representative case with a constant drive speed, the torsional state histories obtained for the full model and the reduced model are plotted. It is noted that the final state of the motion is captured quite well. To further analyze the response during forward whirling, the reduced-order model was nondimensionalized and an approximate solution was obtained by using the method of direct partitions. This method allows one to separate slow scale motions from fast scale motions. As discussed, in the group's prior work, this method can be useful to examine whirling motions. The results obtained by directly integrating the full model as well as the reduced-order model have been compared with that obtained by using the method of direct partitions of motions. It is seen that the perturbation analyses is able to provide an approximate solution that compares well with the numerical results obtained through direct integrations. Next, this analysis is used to examine the influence of the addition of secondary frequency component. It is seen that the addition of the secondary frequency, a high-frequency one, helps smooth out the friction coefficient variation with respect to the relative speed at contact. This is found to have a beneficial effect on the motion and helps suppress large-amplitude torsional motions. Stability analysis was also conducted to examine this effect. Concluding Remarks A study has been conducted to examine the influence of sinusoidal modulation of rotor drive speed in a system, wherein the rotor experiences continuous stator contact. A single degree of-freedom reduced model is developed to study the torsion response and it is found that the addition of a high frequency input can be beneficial in attenuating rotor motions. This is believed to be useful for developing open-loop control schemes for attenuating forward whirling motions of drill strings. Results obtained from a lab scale experimental arrangement will be used to examine the effect of this drive speed modulation further and they will be reported in the conference presentation. Future studies could build on the current effort to examine cases of backward whirling. Acknowledgment: The authors would like to gratefully acknowledge the support received from the Qatar National Research Fund for NPRP Project 7-083-2-041, to pursue this collaborative work between the University of Maryland, College Park, MD, USA and Qatar University, Doha, Qatar.

Using a pair of gears in mesh, an experiment is made on the forced torsional vibration of a two degrees of freedom system with a clearance between two rotating bodies. The experiment shows the existence of a phenomenon that two bodies collide with each other multi-times at one side of the clearance during a half cycle of the forced motion. It is suggested that this phenomenon does not occur in a single degree of freedom system but occurs in a system with at least two degrees of freedom. Effects of the dimension of the clearance and the average angular velocity on the strength of the impact force are investigated. A computer simulation is made. The results of the simulation show good qualitative agreements with those of the experiment.