A Physical Layer Algorithm for Estimation of Number of Tags in UHF RFID Anti-Collision Design

A priori knowledge of the number of tags is crucial for anti-collision protocols in slotted UHF RFID systems.The number of tags is used to decide optimal frame length in dynamic frame slotted ALOHA(DFSA)and to adjust access probability in random access protocols.Conventional researches estimate the number of tags in MAC layer based on statistics of empty slots,collided slots and successful slots.Usually,a collision detection algorithm is employed to determine types of time slots.Only three types are distinguished because of lack of ability to detect the number of tags in single time slot.In this paper,a physical layer algorithm is proposed to detect the number of tags in a collided slot.Mean shift algorithm is utilized,and some properties of backscatter signals are investigated.Simulation results verify the effectiveness of the proposed solution in terms of low estimation error with a high SNR range,outperforming the existing MAC layer approaches.

Application of Fuzzy Logic for Autonomous Bay Parking of Automobiles

In this paper, we investigate the control problem of autonomous bay parking system. We choose a referenced parking lot and define a suitable parking spot based on some measurements at various places. A kinetic model is set up for the convenience of analysis and simulation. The pose of the car during the parking procedure can be determined by the initial pose, the backward speed, and the steering angle of the wheel. Then, both a fuzzy speed controller and a fuzzy steering controller are designed for the bay parking. Finally, simulation results show the effectiveness of our designed controllers.

A Systematic Approach for Instrumentation of a Mechatronic System

This paper deals with instrumenting a mechatronic system,through the incorporation of suitable sensors,actuators,and other required hardware.Sensors(e.g.,semiconductor strain gauges,tachometers,RTD temperature sensors,cameras,piezoelectric accelerometers)are needed to measure(sense)unknown signals and parameters of a system and its environment.The information acquired in this manner is useful in operating or controlling the system,and also in process monitoring;experimental modeling(i.e.,model identification);product testing and qualification;product quality assessment;fault prediction,detection and diagnosis;warning generation;surveillance,and so on.Actuators(e.g.,stepper motors,solenoids,dc motors,hydraulic rams,pumps,heaters/coolers)are needed to"drive"a plant.Control actuators(e.g.,control valves)perform control actions,and in particular they drive control devices.Micro-electromechanical systems(MEMS)use microminiature sensors and actuators.MEMS sensors commonly use piezoelectric,capacitive,electromagnetic and piezoresistive principles.MEMS devices provide the benefits of small size and light weight(negligible loading errors),high speed(high bandwidth),and convenient mass-production(low cost).The process of instrumentation involves the identification of proper sensors,actuators,controllers,signal modification/interface hardware,and software with respect to their functions,operation,parameters,ratings,interaction with each other,so as to achieve the performance requirements of the overall system,and interfacing/integration/tuning of the selected devices into the system,for a given application.This paper presents the key steps of instrumenting a mechatronic system,in a somewhat general and systematic manner.Examples are described to illustrate several key procedures of instrumentation.

The critical pressure for driving a red blood cell through a contracting microfluidic channel

When a red blood cell （RBC） is driven by a pressure gradient through a microfluidic channel, its passage or blockage provides a measure of the rigidity of the cell. This has been developed as a means to separate RBCs according to their mechanical properties, which are known to change with pathological conditions such as malaria infection. In this study, we use numerical simulations to establish a quantitative connection between the minimum pressure needed to drive an RBC through a contracting microfluidic channel and the rigidity of the cell membrane. This provides the basis for designing such devices and interpreting the experimental data.

Design and fluid-structure interaction analysis for a microfluidic T-junction with chemo-responsive hydrogel valves

Due to the deformation ability even under small loads, hydrogels have been widely used as a type of soft materials in various applications such as actuating and sensing, and have attracted many researchers to study their behaviors. In this paper, the behavior of hydrogel micro-valves with reverse sensitivity to the p H inside a T-junction flow sorter is investigated. With the fluid-structure interaction(FSI) approach, the effects of various parameters such as the inlet pressure and the p H value on the stress and deformation of the micro-valves are examined, and the results with and without FSI,including the flow rate and the closure p H, are compared. In order to reduce the response time of hydrogels, the effects of three different patterns on the performance of the microvalves are explored. Eventually, it is concluded that FSI is a key influential factor in designing and analyzing the behaviors of hydrogels.

Development of a 2D Vibration Stage for Vibration-assisted Micro-milling

Vibration-assisted machining(VAM) has the advantages of extending tool life,reducing cutting force and improving the surface finish.Implementation of vibration assistance with high frequency and amplitude is still a challenge,especially for a micro-milling process.In this paper,a new 2D vibration stage for vibration-assisted micro-milling is developed.The kinematics of the milling process with vibration assistance is modeled,and the effects of vibration parameters on the periodic tool-workpiece separation(TWS) is analyzed.The structure of the vibration stage is designed with flexure hinges,and two piezoelectric actuators are used to drive the stage in two directions.An amplifier is integrated into the vibration stage,and the dynamics of the whole vibration system are identified and analyzed.Micro-milling experiments are conducted to determine the effects of vibration assistance on cutting force and surface quality.

基于MAS的CWE计算框架的设计与实现

Cutter/workpiece engagement(CWE)计算是加工仿真中的一个重要问题。针对基于B-rep模型的CWE计算效率不高的特点,采用面向对象的分析方法,综合CWE计算中各Agent结构与功能的特点,进行了Agent对象与几何实体对象认定,给出了CWE计算的Agent对象层次结构,在此基础上实现了基于MAS的CWE计算框架体系,并运用JNI技术实现了与平台无关的CWE计算引擎DCE(Distributed CWE Engine)。

Fabrication and testing of polymer-based capacitive micromachined ultrasound transducers for medical imaging

The ultrasonic transducer industry is dominated by piezoelectric materials.As an emerging alternative,capacitive micromachined ultrasound transducers(CMUTs)offer wider bandwidth,better integration with electronics,and ease of fabricating large arrays.CMUTs have a sealed cavity between a fixed electrode and a suspended metalized membrane.Manufacturing cost and sensitivity are limiting factors in current CMUTs that depend on the fabrication equipment and,especially,on the materials used.For widespread use of CMUTs,a much lower fabrication cost that uses inexpensive materials,which maintain or improve upon existing sensitivity,is needed.Herein,a new fabrication process is described for polymer-based CMUTs(polyCMUTs)using the photopolymer SU-8 and Omnicoat.The first ultrasound B-mode image of a wire phantom created with a 64-element linear array using synthetic aperture beamforming techniques is presented.A 12 VAC signal superimposed on a 10 VDC signal was used on the transmission side,and only a bias-tee,with no amplifiers,was used on the receiving side.The low operational voltage and high sensitivity of this device can be partially attributed to a pre-biasing condition on the membrane.By using a novel sacrificial layer combined with a top electrode embedded inside the membrane,we demonstrated that SU-8 can be used to manufacture CMUTs inexpensively.Moreover,the fabrication used relatively simple equipment,and the number of fabrication steps was reduced compared to traditional CMUT fabrication.This new fabrication process has the potential to increase the use of CMUTs in the ultrasound market,including the market for wearable transducers.

Microscopic dynamic observation of adhesion hysteresis friction and exploration of the influence of different pressures on friction transmission

The mechanism of adhesive friction between viscoelastic materials is a key question.In this study,the friction process of the adhesive interface between a friction lining and a wire rope is dynamically observed in real time to analyze the adhesion hysteresis friction intuitively and quantitatively.The adhesion is determined by the state of motion,while the relative displacement of the wire rope and lining is used to find the magnitude of the adhesive friction.The hysteresis friction is reflected by the internal deformation of the lining.The magnitude of the hysteresis friction is determined by the displacement difference(Ax)in the sliding direction of two marked points at different distances from the contact surface.The results show that the adhesion friction is proportional to the loss modulus and the hysteresis friction is proportional to the ratio of the loss modulus to the square of the storage modulus(E"/(E'^(2))).The frictional vibration first decreases and then increases with the increase in pressure.The K25 lining has the highest adhesion hysteresis friction and minimal frictional vibration.The result provides a simple and intuitive method for research into the friction transmission and vibration of viscoelastic materials.

Gain-scheduling control of a floating offshore wind turbine above rated wind speed

This paper presents an application of gain-scheduling(GS) control techniques to a floating offshore wind turbine on a barge platform for above rated wind speed cases. Special emphasis is placed on the dynamics variation of the wind turbine system caused by plant nonlinearity with respect to wind speed. The turbine system with the dynamics variation is represented by a linear parameter-varying(LPV) model, which is derived by interpolating linearized models at various operating wind speeds. To achieve control objectives of regulating power capture and minimizing platform motions, both linear quadratic regulator(LQR) GS and LPV GS controller design techniques are explored. The designed controllers are evaluated in simulations with the NREL 5 MW wind turbine model, and compared with the baseline proportional-integral(PI) GS controller and non-GS controllers. The simulation results demonstrate the performance superiority of LQR GS and LPV GS controllers, as well as the performance trade-off between power regulation and platform movement reduction.