Visual resolvability and intersection space of view of a binocular microscopic vision system (MVS) in microassembly systems have influences on each other via analyzing theoretically. According to requirements of various microassembly tasks, it is an explicit problem how to find the best compromise between the visual resolvability of binocular MVS and its intersection space of view in three-dimensional space. A Pareto optimization-based method to make the trade-off between the visual resolvability and the intersection space of view of binocular MVS with relevant fixed parameters in microassembly systems is proposed. Through modeling and analyzing on the visual resolvability and intersection space of view of a binocular MVS, the topology and optical magnifications of two MVSs are considered as the key parameters to optimize its physical properties. A multiobjection optimization model based on a Pareto optimization method is formulated and used to find the Pareto optimal cure, namely the Pareto front, which represents the best trade-off between the visual resolvability and the intersection space of view of a binocular MVS. On these bases, the physical properties of a binocular MVS with structural parameters corresponding to the optimization solutions are numerically simulated. Accordingly, a binocular MVS with different parameters is established on an automatic microassembly system with a single manipulator with five degree-of-freedom and experimentally tested. The simulation and experimental results indicate that all of the optimal solutions, which locate on the Pareto front, are the best trade-off between the visual resolvability and the intersection space of view of a binocular MVS. According to the Pareto front, physical parameters of a binocular MVS can be chosen to get the optimal visual resolvability with a certain intersection space of view and vice versa.
The existing vibration energy harvesters can only harvest the vibration energy with single sensitive axial and narrow band, which lead to the problems of low efficiency and high level requirements for installation. This paper proposes a piezoelectric energy harvester for six-degree-of-freedom (six-DOF) vibration energy harvesting utilizing a six-DOF parallel mechanism with cubic configuration. It consists of a proof mass as the upper platform, six flexible legs with two spherical joints connected by a single-degree-of-freedom (single-DOF) harvester, and a foundation support. Compared to the conventional energy harvester, the proposed six-DOF vibration energy harvester has six sensitive axes and broader bandwidth for the proper designed six adjacent natural frequencies, so higher efficiency of energy harvesting can be expected. To investigate the characteristics of the proposed energy harvester, analytical developments and numerical simulations on its natural frequency and modes of vibration are carried out. These results show that the proposed six- DOF vibration energy harvester can harvest six-DOF vibration energy.
In order to realize a six-degree-of-freedom (six-DOF) piezoelectric energy harvester through integrating six single-degree-of-freedom (single-DOF) piezoelectric energy harvesters into a parallel mechanism, which has six sensitive axes and broader bandwidth, a single-DOF piezoelectric energy harvester utilizing a clamped beam configuration is proposed in this paper. It consists of a proof mass and a corrugated clamped beam covered by piezoelectric patches, where the proof mass is mounted at the center of the beam. Compared to the conventional energy harvester, the proposed single-DOF vibration energy harvester has two parallelism mounting planes at the support of the beam and the mass, separately, and can be easily integrated into the parallel mechanism. The stiffness equation of the single-DOF piezoelectric energy harvester is established and analyzed. On this basis, the natural frequency and stress distribution of the harvester are investigated through analytical developments and numerical simulations. These results show that the proposed single-DOF vibration energy harvester has output with the excitation along its axis, while no outputs with the excitation perpendicular to the axis, and the natural frequency and stress distribution can be accurate estimated by the established theoretical models.
High-intensity focused ultrasounds (HIFUs), as a novel non-invasive surgery technology, have been used effectively for cancer therapy. In order to ensure the HIFU treatment safety, the acoustic pressure distributions and the size of the focal regions of HIFU fields need to be measured accurately. In this paper, the lateral sensitive and tip-sensitive all-silica fiberoptic Fabry–Perot ultrasonic hydrophone systems and the corresponding experimental setups are established to measure HIFU fields, respectively. The acoustic pressure distributions of the HIFU field along the X-axis, Y-axis, and Z-axis are compared in the degassed water by the lateral sensitive and tip-sensitive fiber-optic Fabry-Perot ultrasonic hydrophones. Experimental results show that the tip-sensitive configuration can measure the acoustic pressure distribution in the focal region with high accuracy than the lateral-sensitive configuration.
Accurately measuring the acoustic pressure distributions and the size of the focal regions of high-intensity focused ultrasound (HIFU) fields, as well as the temperature induced by the HIFUs, are significant for ensuring the efficiency and safety of treatments. In our previous work, a tip-sensitive all-silica fiber-optic Fabry–Perot (TAFOFP) ultrasonic hydrophone for measuring HIFU fields is developed. In this paper, we explore the possibility that utilizing the TAFOFP ultrasonic hydrophone to simultaneously measure the acoustic pressure of HIFU fields and the induced temperature. The TAFOFP ultrasonic hydrophone for simultaneously measuring the acoustic pressure and temperature is developed and the experiment setup for measuring the HIFU fields based on the developed TAFOFP ultrasonic hydrophone is established. The developed TAFOFP ultrasonic hydrophone is experimentally tested in the degassed water and tissue phantom to verify the possibility of simultaneously measuring the acoustic pressure and temperature. Experimental results show that the sensing system can simultaneously measure the acoustic pressure and temperature.
The theoretical analysis and the prototype testing of the integrated relative displacement self-sensing magnetorheological damper (IRDSMRD) indicate that the controllable damping force performance and the relative displacement sensing performance influence each other for varying applied currents. Aiming at verifying the feasibility and capability of the IRDSMRD to constitute semi-active shock and vibration control systems, this study presents a single-degree-of-freedom (SDOF) shock and vibration control system based on the IRDSMRD. The mathematical model of the IRDSMRD, including the control damping force and the linearity of the integrated relative displacement sensor (IRDS), is established, and the governing equation for the SDOF system based on the IRDSMRD is derived. A skyhook control algorithm is utilized to improve the shock and vibration control performance of the SDOF semi-active control systems. The simulated control performances of the SDOF systems individually using the IRDSMRD without any extra-set dynamic sensor, the conventional MR damper with a linear variable differential transformer (LVDT), and the passive damper, under shock loads due to vertical pulses (the maximum initial velocity is as high as 10 m/s), and sinusoidal vibrations with a frequency range of 0-25 Hz, are evaluated, compared, and analyzed.
The principle and structural configuration of an active controlled microfluidic valve with annular boundary is presented in this paper. The active controlled flowrate model of the active controlled microfluidic valve with annular boundary is established. The prototypes of the active controlled microfluidic valves with annular boundaries with three different combinations of the inner and outer radii are fabricated and tested on the established experimental setup. The experimental results show that: (1) The active controlled microfluidic valve with annular boundary possesses the on/off switching and the continuous control capability of the fluid with simple structure and easy fabrication processing; (2) When the inner and outer diameters of the annular boundary are 1.5 mm and 3.5 mm, respectively, the maximum flowrate of the valve is 0.14 ml/s when the differential pressure of the inlet and outlet of the valve is 1000 Pa and the voltage applied to circular piezoelectric unimorph actuator is 100 V; (3) The established active controlled flowrate model can accurately predict the controlled flowrate of the active controlled microfluidic valves with the maximum relative error of 6.7%. The results presented in this paper lay the foundation for designing and developing the active controlled microfluidic valves with annular boundary driven by circular piezoelectric unimorph actuators.
The principle of a fiber optic Fabry–Perot (F–P) accelerometer (FOFPA) system using the laser emission frequency modulated phase generated carrier (FMPGC) demodulation scheme is first described and experimentally demonstrated. The F–P cavity, which is constituted by placing the end face of a gradient-index lens in parallel with the reflector on the inertial mass, directly translates the inertial mass’s displacement generated by the measured acceleration into phase shifts of the interference output from the F–P cavity. An FMPGC demodulation scheme based on the arctangent (Arctan) algorithm is adapted to demodulate the phase shifts. The sensing model for the FOFPA system using the FMPGC–Arctan demodulation scheme is established and the sensing characteristics are theoretically analyzed. On these bases, the FOFPA is designed and fabricated and a prototyping system is built and tested. The results indicate that: (1) the nonlinearity of the FOFPA system using the FMPGC–Arctan demodulation scheme is less than 0.58%, (2) the resonant frequency, on-axial sensitivity, and resolution are 393 Hz, 13.11 rad/g , and 450 μg/Hz 1/2 , respectively, and (3) the maximum deviation of the phase sensitivity of the FOFPA within the temperature range of 30 to 80°C is 0.49 dB re 1 rad/g .
Recently, prosthetic knees in the developing stage are usually tested by installing them on amputees’ stumps directly or on above-knee prostheses (AKPs) test platforms. Although amputees can fully provide the actual motion state of the thigh, immature prosthetic knees may hurt amputees. For AKPs test platforms, it just can partly simulate the actual motion state of the thigh with limitation of the motion curve of the thigh, the merits or demerits of newly developed bionic above-knee prosthetic knees cannot be accessed thoroughly. Aiming at the defects of two testing methods, this paper presents a bio-inspired AKPs test system for bionic above-knee prosthetic knees. The proposed bio-inspired AKPs test system is composed of a AKPs test platform, a control system, and a bio-inspired system. The AKPs test platform generates the motion of the thigh simulation mechanism (TSM) via two screw pairs with servo motors. The bio-inspired system includes the tester and the bio-inspired sensor wore by the tester. The control system, which is inspired by the bio-inspired system, generates the control command signal to move the TSM of the AKPs test platform. The bio-inspired AKPs test system is developed and experimentally tested with a commercially available prosthetic knee. The research results show that the bio-inspired AKPs test system can not only ensure the safety of the testers, but also track all kinds of the actual motion state of the thigh of the testers in real time.
For semi-active shock and vibration mitigation systems using magnetorheological energy absorbers (MREAs), the
minimization of the field-off damper force of the MREA at high speed is of particular significance because the damper
force due to the viscous damping at high speed becomes too excessive and thus the controllable dynamic force range that
is defined by the ratio of the field-on damper force to the field-off damper force is significantly reduced. In this paper, a
bi-annular-gap MREA with an inner-set permanent magnet is proposed to decrease the field-off damper force at high
speed while keeping appropriate dynamic force range for improving shock and vibration mitigation performance. In the
bi-annular-gap MREA, two concentric annular gaps are configured in parallel so as to decrease the baseline damper
force and both magnetic activation methods using the electromagnetic coil winding and the permanent magnet are used
to keep holding appropriate magnetic intensity in these two concentric annular gaps in the consideration of failure of the
electric power supply. An initial field-on damper force is produced by the magnetic field bias generated from the inner-set
permanent magnet. The initial damper force of the MREA can be increased (or decreased) through applying positive
(or negative) current to the electromagnetic coil winding inside the bi-annular-gap MREA. After establishing the
analytical damper force model of the bi-annular-gap MREA using a Bingham-plastic nonlinear fluid model, the principle
and magnetic properties of the MREA are analytically validated and analyzed via electromagnetic finite element analysis
(FEA). The performance of the bi-annular-gap MREA is also theoretically compared with that of a traditional single-annular-
gap MREA with the constraints of an identical volume by the performance matrix, such as the damper force,
dynamic force range, and Bingham number with respect to different excitation velocities.
KEYWORDS: Bridges, Probability theory, Information fusion, Data fusion, Artificial neural networks, Associative arrays, Silicon, Information technology, Data modeling, Optoelectronics
As the damage diagnosis of bridge structure is highly nonlinear in nature, it is difficult to develop a comprehensive model taking into account all of the independent variables, such as the structural and environmental properties, using conventional modeling techniques. In this study, a method was introduced for damage diagnosis of bridge structure by integration of BP artificial neural network (ANN) and information fusion based on D-S evidential theory. The basic probability assignment functions for data fusion were constructed according to the demand of the damage diagnosis and the real conditions of the bridge structure. And an application example of the proposed method was demonstrated. The results showed that the integration of the two strategy can remove the shortcoming of BP ANN with remaining of its advantages and promote the identified veracity of the whole diagnosis system.
A closed-form dynamic model of a 6-UPS (universal-prismatic-spherical) Stewart platform suitable for modeling and analyzing the vibration damping of the 6-UPS Stewart platform based systems is developed through Newton-Euler dynamic approach. In the formulation, the external excitations on the base-platform of the 6-UPS Stewart platform are considered and the developed model is in a closed form, so the model can not only be used to model and analyze the vibration damping of the 6-UPS Stewart platform based systems when the base-platform is exerted external excitations, but also can be used to design the control algorithms of the 6-UPS Stewart platform based systems to realize the feedback control of the vibration damping. The dynamic formulation is implemented for the modeling and analyzing of the vibration damping of a 6-UPS Stewart platform based system and some numerical simulation results are also presented.
In this paper, a novel method to make MR dampers self-sensing based on the electromagnetic induction and the working principle of an electromagnetic integrated relative displacement sensor (IRDS) integrated into a commercial available MR damper are presented. The IRDS mainly comprises an exciting coil wound on the piston head and an induction coil wound on the nonmagnetic cylinder, which is covered by a cylindrical cover made from the materials with high magnetic permeability. In this way, a novel relative displacement self-sensing MR damper (SSMRD) comprising an IRDS and an MR damper is developed. In order to validate and optimize the performance of the IRDS and the SSMRD, the modeling and analyzing with the finite element mathod based on ANSYS are carried out and the simulation results are presented.
KEYWORDS: Control systems, Fluid dynamics, Signal attenuation, Motion models, Actuators, System integration, Systems modeling, Control systems design, Safety, Vibration control
It is one of effective ways to increase the running speed of
railway vehicles to make the railways more competitive with air
transport while providing better safety. However, the high speed
of the train would cause significant car body vibrations, which
induce the following problems: the ride stability, the ride
quality, and the cost of track maintenance. Thus various kinds of
railway vehicle suspensions, which can be categorized as passive,
active, and semi-active types, have been designed to cushion
riders from vibrations. In this paper, it is aimed to investigate
semi-active suspension systems using magnetorheological (MR) fluid
dampers for improving the ride quality of railway vehicles. A
full-scale railway vehicle model with seventeen degrees of freedom
is proposed to cope with lateral, yaw and roll motions of the car
body, trucks and wheelsets. The governing equations of the railway
vehicle integrated with MR fluid dampers in the secondary
suspension are developed and the LQG control law using the
acceleration feedback is adopted, in which the state variables are
estimated from the measurable accelerations with the Kalman
estimator. The performance of the semi-active suspension system
exploiting MR fluid dampers is compared with those of the active
suspension system with linear and unconstraint actuators and the
passive suspension system with springs and oil dampers. The
results show that the semi-active suspension system with MR fluid
dampers possesses a good ride quality improvement ability.
KEYWORDS: Teeth, Signal processing, Mathematical modeling, Control systems, Computing systems, Analog electronics, Rubidium, Digital electronics, Precision optics, Manufacturing
This paper puts forward an in-process measuring new method for large-scale gears'' profile with a straight-line basis the mathematical models relative to the new method and the experimental researching work having been done.
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