Damping properties of viscoelastic materials modeled by the fraction Kelvin-Voigt constitutive law are discussed in detail.The uniqueness and superiority of the material damping were stressed when compared with the materials described by the ordinary Kelvin-Voigt model.The initial conditions for the governing fractional differential equation are obtained and manipulated carefully.A new characteristic index, viscosity / elasticity ratio, was introduced to serve as a comparison criterion for the discussion of damping performance.The dynamic behaviors associated with some initial conditions, particularly those which were previously unavailable, are studied.The results obtained, along with the abundant data, form the basis for understanding the dynamic behaviors of these kinds of viscoelastic materials and may initiate the development of a new generation of the viscoelastic materials based on silicone gel in industry.

View full abstract

Difficulty in controlling the vibration of a distributed-parameter structure lines in an infinite number of structural modes it has, causing spillover destabilization of the control system.To overcome this problem, this paper propose a novel active vibration control methodology termed"cluster control"that permits the suppression of all structural modes belonging to the cluster of interest.First, it is mathematically verified that every eigenfunction of a two-dimensional structure can be expressed in a form of the"(m, n)modes", m and n being modal indices.Then, a cluster filtering method is introduced, whereby all eigenfunctions are divided into a finite number of groups(clusters), each member of the group retaining the same characteristics in common.By verifying the reciprocity of sensing and actuation of a structure, a cluster actuation method is then introduced, enabling excitation of the eigenfunctions of a targeted cluster without affecting any repercussion on the other clusters.Moreover the cluster control method consisting of both the cluster filtering and actuation is presented, allowing suppression of all structural modes of the targeted cluster without causing instability of the control system .Finally, an experiment demonstrates the validity of the proposed method for suppressing all vibration modes of a cluster.

View full abstract

A large-scale structural-acoustic analysis using sub-space superposition, in which a cavity is divided into several acoustic fields has been developed.This system uses a transfer-function mehtod to solve the acoustics efficiently.By solving simultaneous equations using the Gaussian-elimination method for each pair of neighboring acoustic sub-fields in sequence, calculation time and memory requirements are reduced.Calculation accuracy is the same as when calculating the entire acoustic field without dividing it.We created a closed acoustic model (a cavity model) and used it to numerically simulate acoustics.The simulation results show that the developed large-scale structural-acoustic analysis effectively reduces calculation resources.

View full abstract

To determine the suitable thickness of sound absorber which maximize the sound absorption effects in the rectangular enclosure, the analytical study identifies the interior sound field characteristics of cavity with foamed aluminum lining and the experimental verification is performed with random noise input.By using a two-microphone impedance tube, we measure experimentally the absotrption coefficient and the acoustic impedance of simple sound absorbing materials.Measured acoustical characteristics of the foamed aluminum sheet absorber are compared to recycled rubber and sponge absorbers in order to identify corresponding best-effective frequency range.Measured acoustical parameters of the test samples are applied to the theoretical analysis to predict sound pressure field in the cavity.Measured sound absorption effects are compared to predicted ones in both cases with and without foamed aluminum lining at the bottom of the cavity of the rectagular enclosure.By using the selected foamed aluminum sheet absorber, the sound absorption effects of the exterior sound field is investigated experimentally for the structural-acoustic coupled enclosure with the foamed aluminum lining in the cavity.

View full abstract

An effective method for improving the signal-to-noise ratio from measurements of bearing housing vibration is presented.The method is based on the conventional adaptive noise cancelling (ANC) technique principle;it varies the main signal input and reference signal input.Since the main and reference inputs signals are collected at different times, this method is called asynchronous adaptive noise cancelling (AANC).It can improve the signal-to-noise ratio, as in the case of the detecting bearing faults when vibration signals of machinery are collected under low-frequency noise condition.In combination with AANC, statistical analysis, enveloping spectrum analysis techniques are used for detection of bearing fault and diagnosis.Experimental result has shown that these techniques can be made more effective only after AANC has reduced the background noise from the diagnostic signals.A new approach is proposed to the traditional fault detecting for self-aligning roller bearings when the shaft speed is low (250rpm) or high (1000rpm) condition.

View full abstract

This paper presents a new multiple-degree-of-freedom position detection mehtod.The proposed method uses a position detection unit consisting of three two-dimensional angle sensors and a two-dimensional angle grid.The displacements in the x and y directions in addition to the rolling, pitching and yawing of the moving object can be determined from the outputs of the angle sensors.The angle grid and angle sensors are calibrated using a self-calibration method to assure accurate position detection.In addition, simulation results confirming the feasibility of the new method are presented.

View full abstract

This paper examines a new in-process measurement system for the measurement of micro-defects on the surfaces of brittle materials by using the AFM(Atomic Force Microscopy).A new AFM scanning stage that can also perform nano-scale bending of the sample was developed by adding a bending unit to a commercially available AFM scanner.The bending unit consists of a PZT actuator and sample holder, and can perform static and cyclic three-point bending.The true bending displacement of the bending unit is approximately 1.8μm when 80 volts are applied to the PZT actuator.The frequency response of the bending unit and the stress on the sample were also analyzed, both theoretically and experimentally.Potential surface defects of the sample were successfully detected by this measurement system.It was confirmed that the number of micro-defects on a scratched surface increases when the surface is subjected to a cyclic bending load.

View full abstract

This paper addresses the active modal control of a planar structure using the point sensors / actuators designed to replace the distributed sensors / actuators regarded as an ideal sensor / actuator.It is the purpose of this paper to verify the capability of the active modal control system experimentally.First, a modal control system for a general distributed structure based upon point sensors / actuators is designed.Then, the modal control of an isolated mode as well as a degenerate mode is conducted, demonstrating the control effect for suppressing the targeted structural mode while exerting no influence on the the others.It is found that even an over-damping state of the mode of interest is possible without inducing control instability.Moreover, by placing additional"lead"masses onto the planar structure with a view to varying modal parameters of the structure, the robustness in modal filtering, modal actuation and modal control is investigated, demonstrating a significant robustness of the active modal control system.

View full abstract

The paper considers a planar vibrational model of mobile robot vehicle equipped with dynamic vibration absorber.The purpose is first, to determine the dynamic vibration absorber parameters optimal adjustment giving the lowest vibrational displacement of the vehicle body at resonance, when the vehicle is subjected to ground roughness modeled as sinusoidal or periodic rectangular spaced pulse disturbances.Second, the purpose is to determine disturbance frequencies at which the dynamic vibration absorber parameters optimal adjustment fails to ensure the vibration stability of the mobile robot vehicle equipped with the dynamic vibration absorber, and to recommned measures to guarantee the vibration stability at these frequencies.

View full abstract

A low-cost digital control system is developed for self-sensing magnetic suspension using hysteresis amplifiers.A unipolar-type hysteresis amplifer is designed and manufactured for experimental study.Since the switching rate of the hysteresis amplifier is sensitive to the load impedance, the gap between the electromagnet and the suspended object is estimated from the switching signal.In the developed system, the frequency of the switching signal of the amplifier is converted to a digital form by counting by a counter circuit.The converted signal is inputted to a computer calculating control input for stabilization.The developed digitally controlled magnetic suspension system succeeds in actual self-sensing operation.

View full abstract

For step reference input, pneumatic servo systems are designed in such a way that there is a compromise between stability and rise time of the response.For practical use, we have adopted some ideas to improve the response.One example is the operation of a pneumatic on / off valve by electrical power higher than the nominal power for an initial short period of time.Based on the above example, we developed a fuzzy virtual reference generator that can adjust the reference input to the fuzzy controller adaptively by fuzzy rules to improve the rise time of the response.The applicability of the proposed method is confirmed by experiments using vertical pneumatic servo systems.

View full abstract

The coupling and pneumatic compressibility effects cause strong parameter variety in a two-input two-output(TITO) pneumatic control system.Thus, it is difficult to design a controller using conventional control method.In this paper, self-organizing fuzzy control (SOFC) is applied to a TITO pneumatic position control system.By using the concept of decentralized control, a TITO control structure is decomposed into two separate control channels.Each channel is associated with a SOFC for single-axial pneumatic control system and a decoupling SOFC for structure interactions.Experimental results show that the proposed control algorithm can achieve high control accuracy.And, it robust to various operating conditions.

View full abstract

This paper deals with the design problem of decentralized PID control systems.An automatic tuning algorithm based on the partial model matching on the frequency domain for the decentralized PID controller is presented.In the tuning scheme, the partial model marching between the loop transfer function of the control system and a desired open-loop model at some frequency points is considered.The introduction of compensators, a parallel feedforward compensator (PFC) and a pre-compensator, is also considered in order to guarantee the stability of the decentralized control system.It is shown that the diagonal-dominance, which is necessary to realize a stable decentralized contorl system, can be relaxed by introducing a PFC.Further, robust stability of the resulting control system is analyzed and a guiding principle for the design of the decentralized PID control system will be proviede.

View full abstract

An optical novelty filter based on the two-wave mixing in a photorefractive BaTiO₃ crystal is applied to motion detection for the purpose of its application to the robot vision.A simple method is proposed to mimic the reflex vision system that a human being possesses.Our method uses a photo-detector array to detect the output from the optical novelty filter, and the detector element that obtains the highest signal is selected.By simulations using a simple animation, it is shown that the large or the faster objects can be detected at a higher probability than smaller or slower ones.Tracking a moving object is demonstrated with a 2×2 photo-transistor array and a selective circuit including an exclusive gate circuit.

View full abstract

This paper describes a method for building three-dimensional deployable truss structures from the viewpoint of deployment reliability.In this regard a method is proposed for designing a closed-loop deployable truss structure for future large space antennas through a kinematic degree-of-freedom analysis of the mechanical system.Using this method, it is possible to attain a truss structure with the appropriate constraints.We have designed and fabricated a prototype and achieved successful deployment under a microgravity environment yielded by parabolic aircraft flight.Hence, the results have demonstrated the effectiveness of deployable truss design using kinematic degree-of-freedom analysis.

View full abstract

In this paper, the decentralized stabilization problem of uncertain large-scale systems with time-delays in subsystem interconnections is investigated.An observer-based controllers is developed using the Lyapunov method.For robust stability of the system, a sufficient condition is derived in terms of linear matrix inequalities (LMIs) which are solved by convex optimization algorithm.A numerical example is given to illustrate the proposed technique.

View full abstract

In this paper, we present a robust observer-based controller for perturbed time-delay systems, in which the full state cannot be measured.Lyapunov method with linear matrix inequality (LMI) technique is used for synthesis of the control law to stabilize the system.The time-varying perturbations are assumed to be within a given compact set.

View full abstract

In this paper we are concerned with the estimation of the operating deflection shapes (ODSs) of a system in an unsteady state.It is usually difficult to identify the ODSs, because the responses under operating conditions are not always in a steady state.Therefore, the adaptive identification scheme of the ODSs for non-stationary signals is necessary.In this paper we present a new type of subspace method that can identify well-excited frequencies and the ODSs corresponding to those frequencies.In order to prove the adaptability of this scheme for time-varying signals, we demonstrate its performance using artificially generated responses.Then we use the responese of an actual structure and show the effectiveness of this scheme with actual data.The results are in good agreement with the analytical ones and lead us to belive that the proposed scheme can be successfully used for the identification of time-varying signals

View full abstract

An experimental for determining frequency response functions accurately is presented.Input noise is greatly reduced by using a new hammer impact apparatus with a fixed hammer pivot.With the new impact hammer apparatus and other methods, accidental errors have been reduced.Bias errors cannot be removed by statistical methods, the examples of which are mentioned here and improvements suggested.

View full abstract

This contribution considers the application of the recently proposed technique for analyzing the robust stability of plants having a rational transfer function with independent parametric uncertainty structure controlled by a first order controller, known as the sixteen plant theory (SPT), to time delay systems.The case study is a heat exchanger represented by a first order plus time delay (FOPTD) model controlled by a proportional-integral (PI) controller.It has been demonstrated that the SPT is a very useful tool for analyzing the robust stability of single input single output (SISO) time delay systems which are commonly found in chemical process control problems.The SPT has also been used to compare the robustness of three popular controller tuning methods which clearly demonstrate its versatility.The computational effort required by the SPT can be significantly reduced by using symbolic computation.

View full abstract

This paper presents a new tuning bilinear approximation method together with the interval arithmetic operation to convert a continuous-time (descrete-time) uncertain system to an equivalent discrete-time (continuous-time) uncertain model.Based on the bilinear approximation method, we induct one parameter for tuning the error bound between the exact and approximate uncertain system matrices.The bounds of interval system matrices via the proposed interval tuning bilinear approximation method are narrower than those of the existing interval bilinear and the interval pade approximation methods⁽1).The resulting interval models (the enclosing interval models) are able to tightly enclose the exact uncertian models.Also the approximate discrete-time interval solution is able to tightly enclose the exact interval solution of the continuous-time uncertain state-space equation.The proposed method will be helpful for analysis and synthesis of uncertain systems.

View full abstract

Collision Warning / Collision Avoidance (CW / CA) systems have been an active research and development area as the interests and demands for active safety of road vehicles increase.A road-adaptive CW / CA algorithm has been proposed in this paper.The algorithm consists of a tire-road friction estimator, a distance warning decision algorithm and a brake control algorithm for collision avoidance.Since it would be useful to incorporate the tire-road friction information into a vehicle collision warning / collision avoidance algorithm, a real-time tire-road friction estimation method and a new CW / CA algorithm using the estimated tire-road friction have been developed.A'Hardware-in-the-Loop'(HiL) simulation system for the CW / CA system has been designed and used to test the algorithm, radar sensors, controllers, and warning displays under realistic operating conditions in the laboratory.

View full abstract

An optical servo system, which can be used in hazardous environments, is a novel and attractive control system.In our previous paper, we proposed an analytical model of a tested optical servo system which consists of an optical servo valve and a small pneumatic cylinder in order to improve the position control performance.This paper describes an extension of the optical servo system to a more normal scale system using a normal pneumatic rodless cylinder with a full stroke of 600mm.First, two kinds of opto-pneumatic servo system using the rodless cylinder are explained briefly.Second, the control performance of the first system which uses two flow amplifiers in the market is investigated.Finally, the optical servo valve is designed and improved by using the analytical model proposed previously.And the control performance of the second system using the improved valve is investigated.As a result, it is shown that the improved optical servo valve is more useful in a normal scale control system compared with the flow amplifier.

View full abstract

A dynamic analysis of link structures, including elastic vibrations, is presented.The two-node element including large displacement is developed.This element is based on the theory of finite rotation and includes the geometric stiffiness.The stiffness matrix and the inertia matrix are obtained from FEM model by the theory of Guyan's reduction including large displacement motion.In this paper, we explain the theory of this element and show some examples of analysis.

View full abstract

A new discrete deconvolution procedure is developed that uses the wavelet packet based system decomposition.The system is decomposed into subsystems using the wavelet packet transform and the inversion of each subsystem is derived approx imately.We show how to select the wavelet packet bases to mitigate the effects of ill-posedness due to the narrow bandwidth of the system.A new wavelet bases family with the optimal transition band performance is generated to surpress the approximation error.Futhermore we introduce the soft thresholding into our procedure to reconstruct temporal inhomogenious signals more efficiently.

View full abstract

This paper presents a novel concept of self-organizing collective robots with morphogenesis in a vertical plane.For physical reconfiguration of a swarm of robots against gravity, new types of mechanisms and control strategies are proposed and demonstrated.Basic feasibility of the mechanisms was confirmed through an experiment adopting four prototype robots.Each robot is composed of a body and a pair of arms.The body is equipped with permanent magnets for bonding with another robot.The arms change the bonding configuration by rotating and sliding motions.As for the control strategies, we proposed algorithms which can generate specific global formations of robots from local and minimum interactions between neighboring robots.It is shown that the proposed algorithms can successfully conduct the swarm of robots to the predetermined configurations.

View full abstract

In this study, a robot that utilizes a parallel mechanism at parts of its body is proposed.The robot combines locomotion and manipulation, and consists mainly of four units of three degree of freedom (hereafter called DOF) parallel mechanism with linear actuators and two grippers attached to both sides of its body.The robot has high redundancy with 14-DOF without grippers.The purpose of this study is to realize the"intelligent motion"in the redundant parallel manipulator that performs the basic motion of the proposed robot.The robot determines its motion while considering its redundancy and improves it using actuator information derived from the motion.First, we analyze the kinematics and statics about the parallel manipulator, and show a method to optimize the solution of inverse kinematics that includes the redundancy problem.Next, we discuss the intelligent motion task planning of the parallel manipulator using actuator information.Two methods are proposed based on the optimization of inverse kinematics.One optimizes the motion by iteration.The other optimizes the motion successively in continuous motion tasks.Finally, the effectiveness of the proposed methods is verified experimentally.

View full abstract

ODV9 is a newly designed nonholonomic omni-directional vehicle and proposed as an indoor mobile platform.Such a platform is required to move freely in narrow spaces and to travel on bumpy road surfaces in some measure.ODV9 has four wheel modules, with each wheel module incorporating one motor, one brake and one wheel.The coupling of steering and driving, that results in errors and tire slippage, does not occur in ODV9 intrinsically because each wheel module has only one motor.Compared with other ODVs, the advantages of ODV9 are not limited to the simplicity of its mechanism.Benefiting from using a normal type wheel equipped with a tire, ODV9 is capable of moving in various environments.In this paper the mechanism and the various running modes of ODV9 are discussed, and some experimental results are presented to illustrate its effectiveness.

View full abstract

The Euler-Savary equation is the most fundamental relationship used to determine the relative curvature of a two-dimensional tooth profile which corresponds to relative motion.In this paper, the necessary conditions for gearing were analyzed, when a pair of tooth surfaces mesh continuously with a contact line and the basic relationships between tooth surfaces and their relative motion were derived mathematically.In addition, the relative normal curvature and the geodesic torsion of the tooth surfaces and relative motion were shown to be related to hypoid gears, and the Euler-Savary law was extended to the equation of three-dimensional tooth surfaces for the most general form of gearign.

View full abstract

Epicyclic gear trains used in automatic transmissions are called epicyclic gear mechanisms, which contain at least four coaxial links, no embedded structure, and no redundant links.Using the concept of admissible acyclic graphs, an efficient methodology has been developed to systematically enumerate the displacement graphs of N-link epicyclic gear mechanisms from the catalog of N-vertex admissible acyclic graphs.Using the notation of adjacency matrices, a computer program has been successfully developed for the automatic enumeration of the displacement graphs of epicyclic gear mechanisms.As a result, an atlas of the displacement graphs of epicyclic gear mechanisms with up to ten links have been automatically constructed.The result of this paper is of benefit to the development of multi-speed automatic transmissions.

View full abstract

A new approach on modeling is put forward for fully computer integrated product development.A basic concept of functional model is proposed for embodying this approach.This model is used mainly for explaning and simulating the functions and the efficiencies of various machines composed of many mechnical, fluid-mechanical and electrical parts.All organizations and engineers of various specialties in charge of the product development can collaborate one another using this model.This model can be used in all stages of product development from the initial plan through the design to the prototype testing.Functional models of single degree of freedom mechanical, electrical and fluid-mechanical systems are illustrated, and its validity and usefulness of the proposed approach are demonstrated.

View full abstract

These days, the requirements of machines have become more and more complicated, and many of those requirements have to be satisfied simultaneously.In such cases, it would be rational to carry out multi-objective optimization.However, in conventional decision-making problems, we need to give preference based on local information such as trade-off.Although it is difficult to do so.Providing designer with multiple acceptable designs will be of great help for them to give preference, because the designs will serve as a map of the design space.However, to give multiple Pareto solutions, we need to carry out a large number of scalar optimizations, and this is unrealistic.In order to give multiple acceptable designs by a single optimization process, we simulate adaptation strategies of wildlife combined with genetic algorithms from a previous study.We have succeeded in keeping the variation among populations and directions to give multiple acceptable designs, but have failed in controlling of the number of populations.As a follow-up of the previous study, we focus mainly on adaptation of foraging and try to simulate the evolution of species by changing the searching range of design variables.The goals of the proposed mehtod are to find multiple acceptable designs, to keep the variation among populations and to see the changes of searching range of each objective function, to provide designers with a clear map of the design space.In this study, the proposed method isanalyzed using a simple two-variable, two-objective problem whose analytical solution is available.

View full abstract