Use of magnetic bearings for high-speed rotor and application in clean environment or in special circumstance have been gradually increasing. This article overviews research trends and application presented before the Eighth International Symposium on Magnetic Bearings (ISMB-8). Interesting research topics are the combined realization of motor and magnetic bearing, low loss magnetic bearings and self-sensing techniques. New application fields include small spindles for data storage devices, energy storage flywheels, and artificial heart pumps. Various new technologies are reported related to these new application fields.

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Meanwhile the bearingless motor technology offers a lot of mechanical and electrical design variants for various kinds of applications. A comparison of switched reluctance motor, asynchronous motor and permanent magnet motor technology shows advantages and disadvantages with regard to different technical requirements. Especially for small motor applications with large air gaps the permanent magnet motor is of great importance. This is confirmed by a comparison of electromagnetic and permanent-magnetic pole designs. Based on bearingless permanent magnet motors with integrated winding systems for levitation as well as torque generation reliability and fault-tolerant design studies are carried out. It is shown that with an appropriate motor design a failure of an arbitrary phase can be compensated by the motor itself. In such a case there is no need for failure detection in order to switch over to special auxiliary control algorithms. A further advantage of the integrated winding system is the high grade of copper utilization independent of the ratio of radial force and torque loads.

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Aiming at small high-speed rotating machines, this paper proposes a Lorentz force type self-bearing motor, where a new four-pole winding configuration is used to make it function both as a synchronous permanent-magnet motor and as a magnetic bearing. Due to using Lorentz force dominantly, the proposed motor has some good points such as linearity of control force and facility of design and analysis. And compared with the 8-pole type previously developed, it is advantageous at high speed. Focusing on the feasibility of the proposed motor, this paper introduces a prototype, which is manufactured in disk type with an outer rotor and successfully run up to 12600rpm without contact. Static and dynamic characteristics of the prototype are examined.

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Robust stability and closed loop performance of a Lorentz-type self bearing servomotor test rig are presented. Previous work has identified the existence of multiple destabilizing terms in the servomotor force-torque characteristic. These terms are treated as modeling errors and accounted for using structured uncertainty. A set of decoupled PD controllers is designed and the stability robustness of the system is evaluated via µ-analysis. Experimental results confirm that the resulting controllers provide stable levitation and angular pointing of the rotor over all uncertainties. The closed loop bearing stiffness for the servomotor was measured as 502N/mm and the closed loop angular position stiffness was measured as 17.7N-m/rad. The angular pointing accuracy of the servomotor was also measured and found to be <30µrad.

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Recently, bearingless motors have been developed to enhance motor drive systems with magnetic suspension. Several types of motors have been proposed as bearingless motors, such as induction, surface mounted permanent magnet, inset permanent magnet, interior permanent magnet, buried permanent magnet, homopolar, hybrid, and switched reluctance bearingless motors. Permanent magnet bearingless motors have been attracting more interests in these years because of the high efficiency. In this paper, a consequent-pole bearingless motor is proposed. A rotor has buried permanent magnets, of which polarities are like. The radial force of a consequent-pole bearingless motor is generated by dc current. Thus, rotational angular position is not needed in a magnetic suspension controller. Radial force variations caused by a rotor rotation are minimized by improving arrangement of stator suspension conductors. A prototype bearingless motor and its controller are built. In experiment, principles of magnetic suspension in the proposed consequent-pole bearingless drive are confirmed.

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While electromagnetic actuators have been proven in many precision motion control applications, their stray fields constrain their use in systems that require high stability of charged particle beams. Fringing fields from these actuators should be sufficiently small to have minimal influence on the trajectory and focusing properties of the charged beams. We have built a levitation linear motor that is designed to have significantly reduced fringing fields. The design achieves large far field attenuation because of parallel opposing multipole placement in the synchronous motor bearing. The design is suitable for future generations of electron beam lithography, where the allotted error to stage fringing field may be less than 1nm. The low fringing field design attains very strong fields at the stator, where force is generated, while the fringing fields fall very rapidly. Whereas fields for a dipole fall off as radius^-3, the paper presents a prototype synchronous motor magnet array with fields that fall off largely as radius^-10 in the far field. The stator has fields that fall off as radius^-5. The novel permanent magnet array and coil array technologies can be implemented in stage designs where the fringing field is designed to have negligible influence on the electron beam in a lithography machine. The stator and magnet array have a sufficiently low field to allow placement of the arrays unusually close to the electron beam. This allows a compact, high resonant frequency stage structure. A precision motion control stage based on the low fringing field magnetic bearing is thus shown to be feasible for next generation electron beam lithography.

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A repulsive magnetic bearing system equipped with a piezoelectric actuator for the motion control of permanent magnets is studied experimentally. In this system, the radial motions of the rotor are passively supported by repulsive forces between permanent magnets. The motion in the axial direction is stabilized by moving the permanent magnets for radial suspension with a piezoelectric actuator. In the experiments, a piezoelectric actuator with a stroke of 200µm was installed first. PD and I-PD controllers were applied to achieve levitation without any mechanical contact. It was experimentally shown that the dynamic characteristics of the levitation system could be adjusted by pole assignment. Next the actuator was replaced by an actuator with a stoke of 90µm. Experimental results demonstrated that the rotor can follow stepwise command signal whose magnitude was within ±20µm.

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Electromagnetic suspension is an essential technique commonly used in industrial transport system without mechanical contacts. The reduction of the energy consumption in mover side is significant. Authors have proposed a 4-pole electromagnet with three-degrees of freedom in its control, which works well for independent levitation stabilization of a single electromagnet. They also proposed a linear synchronous drive, in which the attractive force produced by armature flux of a linear motor is used as levitation force, for realizing a completely passive mover. The principle of the simultaneous control of levitation force and thrust is based on the separation of d- and q-axis current components. The basic idea, and simulation results are described as well as its successful experimental verification.

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Magnetic bearings (MBs) are complex machines in which sensors and controllers must be used to stabilize the rotor. A standard MB requires active control of five motion axes, imposing significant complexity and high cost. In this paper we report a very simple MB and its experimental testing. In this MB, the rotor is stabilized by active control of only one motion axis. The other four motion axes are passively stabilized by permanent magnets and appropriate magnetic circuit design. In rotor radial translational motion, which is passively stabilized, a resonant frequency of 205Hz is achieved for a rotor mass of 11.5×10^-3kg. This MB features virtually zero control current and zero rotor iron loss (hysteresis and eddy current losses). Although the rotational speed and accuracy are limited by the resonance of passively stabilized axes, the MB is still suitable for applications where cost is critical but performance is not, such as cooling fans and auxiliary support for aerodynamic bearings.

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This paper describes newly developed superconducting magnetic bearings (SMBs) assisted by self-sensing active magnetic bearings (AMBs). The self-sensing AMBs detect the gaps between rotor and electromagnets. The principle of the self-sensing sensors is based on a differential transformer. The sensitivity in liquid nitrogen is almost equal to that in the air. The sensor is found to be useful in liquid nitrogen at 77K(-196°C). Moreover, the sensors are applied to the SMBs. In this paper, dynamics of the SMBs with self-sensing AMBs are discussed. From the results, it is found that the system is useful and promising.

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Closed-form design equations for magnetic bearings are desirable for design optimization of sophisticated electrical mechanical systems such as artificial hearts. We develop asymptotic approximations to force and stiffness characteristics of magnetic bearings formed from concentric permanent magnet rings having rectangular cross sections. The equations are well adapted to spreadsheets and facilitate an efficient numerical optimization process. The method was applied to the development of the HeartQuest^TM VAD (ventricular assist device), which achieved remarkable compactness and stable operation.

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The aim of this paper is to realize a sliding mode control system using robust hyperplane based on fuzzy model for the active magnetic bearing system with gyroscopic rotation. A fuzzy model of the active magnetic bearing system is built from the input and output data of the actual turbo-molecular pump by using the fuzzy neural network. The sliding mode controller has a switching hyperplane using µ-synthesis theory which has a powerful robustness and can suppress spillover phenomena. The ultra high-speed operation test of the actual turbo-molecular pump which reached the rated operation 45000rpm has been done by using the proposed controller. The good experimental results have been obtained. Therefore, it has been clarified that the proposed scheme is very useful strategy for the active magnetic bearing system.

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The chatter stability of a rigid milling spindle levitated by five-axis active magnetic bearings (AMBs) is studied for its chatter free cutting, as the control gains of AMBs vary. The characteristic equation for regenerative chatter loop with a delay element is described by a linear differential-difference equation, accounting for the dynamics of the AMB controllers, the uncut chip thickness equation and the cutting process as well as the rigid spindle dynamics itself. An efficient chatter stability analysis method is then proposed to predict the stability lobes and chatter frequency in milling. The analytically predicted stability lobes are found to be in good agreement with the lobes generated by other methods available in the literature. Using the proposed method, parametric study is also performed to investigate the influences of the damping and stiffness coefficients of AMBs on the chatter free cutting conditions, as they are allowed to vary within the stable region formed by the AMB control gains.

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In this paper we propose an unbalance compensation method, which is able to work through a wide range of rotational speed. Actually the vibrations due to unbalance or eccentricity on the rotor contain the direct synchronous rotational speed signal. It is not reasonable using an extra rotational sensor to measure the rotational speed. Thus a resolver-like evaluation of rotational speed is proposed to serve as the necessary synchronous rotational speed signal. The speed of rotation is directly evaluated from the unbalance driven compensation signal. The unbalance compensation without using a rotational sensor are realized successfully on a test rig with 25 kg-rotor from 0 to 28000 rpm. Moreover, a speed control using the evaluated speed signal is also implemented.

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Shock and vibration testing of an Active Magnetic Bearing (AMB) supported energy storage flywheel is presented. The flywheel is under development at the University of Texas-Center for Electromechanics (UT-CEM) for application in a transit bus. The flywheel is gimbal mounted to reduce the gyroscopic forces transmitted to the magnetic bearings during pitching and rolling motions of the bus. The system was placed on a hydraulic terrain simulator and driven through pitch, roll and shock motions equivalent to 150% of maximum expected bus frame values. Although the AMB control approach was originally developed specifically to ensure rotordynamic stability, relative rotor/housing motion was typically less than half of the backup bearing clearance under all tested conditions. Test results are presented and compared to analytical predictions for the 35000rpm nominal operating speed. The impact of the AMB control algorithm is discussed relative to the input forcing function.

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Research into multibody dynamics has long been done in Japan. In this paper, recent developments are surveyed from the conference proceedings and the transactions of the engineering societies of Japan. The D&D Conference proceedings and the transactions of the JSME are mainly focused on and the activities of the workshops and the technical committees in the JSME are reported on. Some reviews of other research in the world are also given. The software developments of multibody dynamics in Japan are briefly reviewed.

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In this paper, the research background and current activities of multibody researchers in Korea are briefly reviewed. The research trend and the future of the multibody dynamics field in Korea are also predicted. In Korea, there are 36 Korean journals and 4 English journals in the field of mechanical engineering. Searching a database of these journals, one can find more than 100 papers using the keyword ‘multibody'. Recent trends in and applications of multibody dynamics in Korea are summarized from those papers published during the period from the late 1980s to the present. Since most Korean researchers in the field of multibody dynamics obtained their doctoral degrees from universities in the United States of America, the DADS program and the ADAMS program have been used in Korean industries and universities since the 1980s. However, in the 1990s, two multibody dynamics codes (i. e., the RecurDyn program and the AutoDyn7 program)were developed by Koran researchers. These codes are explained, and the ADAMS program and the DADS program are also briefly reviewed.

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A new methodology for dynamical analyses applicable to a very large class of rigid and flexible multibody systems is presented. It is based on a variable-gain error correction method with scaling, and has the following distinctive features: (i)All kinds of holonomic and nonholonomic equality constraints can be treated in a plain and unified manner; (ii)Stability of the constraints is always attained; (iii)The formulation has an order N computational cost in terms of both the constrained and unconstrained degrees of freedom, regardless of the system topology; (iv)Unlike the traditional recursive order N algorithms, it is quite amenable to parallel computation; (v)Since no matrix operations are involved, it can be implemented to very simple general-purpose simulation programs. Versatility, dynamical validity and efficiency of the approach are checked through numerical studies of several particular systems.

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The paper presents a multiport model of flexible multibody systems by analogy with a connection multiport in electrical circuit theory. First we introduce a concept of a fundamental pair, that is, a pair of a mechanical joint and its adjacent body to recognize the flexible multibody system as an interconnected system of such fundamental pairs. Second we employ a finite element model to describe flexible deformations associated with large overall motions using moving frames and we also model various kinematical and dynamical relations of the fundamental pair such as geometric nonlinear effects associated with the flexible deformations and kinematical constraints due to the mechanical joint by nonenergic multiports together with dual connection matrices. Finally it is shown that the interconnection of the nonenergic multiports with physical elements provides a multiport model of the fundamental pair and also that the equations of motion of the flexible multibody system can be systematically formulated by the present approach.

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An efficient method for constraint force analysis of specified joints has been developed in a serially connected open chain multibody system. In the method, the system equations of motion are derived using the recursive formulation, but constraint forces are computed non-recursively for specified joints. The efficiency of the proposed formulation has been compared with the recursive Newton-Euler formulation by the operational counting and the CPU time measure. To validate solution accuracy of the proposed method, the 7 d. o.f RRC robot arm simulation has been carried out. Essentially the same simulation results are obtained from the proposed method and from the commercial dynamics analysis program DADS.

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This paper proposes a new method for solving the inversion of the system matrix that appears in the process of numerical integration of matrix dynamic equation. The singular value decomposition (SVD) has been widely known to solve the inversion of the matrix or to solve the Riccatti type matrix equation. The prominent advantage of using the SVD method resides in the fact that it provides singular values of the system matrix. However its low convergence rate hampers it to be used in the applications that handle a large-scale system matrix or in the real time control. The fast similarity factorization (FSF) proposed in this paper is one kind of SVD in a sense that it consists of many times orthogonal transformations. But the FSF provides fast and stable singular value decomposition. The simulation shown in this paper reveals its overwhelming convergence rate compared to the conventional SVD algorithms.

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A new time integration method is proposed, which is a kind of extension of the Wilson-θ method. It has good accuracy, unconditional stability and numerical dissipation. The algorithm and characteristics for linear systems are shown. Also, an application method for non-linear systems is described. For analyzing multibody systems, a formulation of elastic link systems consisting of two dimensional truss, beam and scalar elements is indicated. Some examples such as a stiff vibration system, a double pendulum system, and a four link system are calculated by the present method, which demonstrates that it is useful and available for analyzing multibody systems.

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This paper deals with nonlinear analyses of sheet flutter in a narrow passage caused by fluid-structure interaction. Attention is paid to the behavior of sheet when flow velocity exceeds critical flow velocity. With discretization, the sheet is modeled as a combination of mass less beam elements, springs and discrete mass particles, in which the mass of each particle and spring coefficients are calculated based on the beam model. Nonlinear fluid forces acting on the mass particles are formulated then coupled with equations of motions of structure. After that the behavior of large-amplitude vibration of cantilevered sheet is simulated using numerical computation, showing that vibration of sheet grows into a limit cycle oscillation then becomes unstable with increasing flow velocity.

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Solar array panels of a satellite must be locked at an intended position in order to perform its mission successfully as the electric power source of a satellite. To deploy the solar panels completely, it is necessary to design the deployment mechanism which has high precision and reliability. Consequently, the analysis on the dynamic characteristic of the deployment mechanism must be done at an initial design stage. Moreover, various the mission of a satellite has made the size of solar panels got bigger, so elastic effect has to be considered seriously to get more practical and precise analysis. In this paper, the dynamic analysis methods to predict solar panels' deployment motions are proposed. First, the method of evaluating the dynamic property of solar panels' deployment mechanism using SEH (Strain Energy Hinge) that has nonlinear buckling property is presented. Second, the analysis procedure for the multibody dynamic system with redundant constraints is also proposed. Therefore, these two proposed methods are applied to the analysis of the solar panel deployment. In addition, the reliability of proposed methods is verified by experiments.

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Investigating disturbance properties of reaction wheels (RWs), a key component in attitude control system of spacecraft, is important for health monitoring of RWs, exploration of new RWs, designing attitude control systems, and so on. In this paper, we first present a recently developed disturbance detector and experiment results for practical RWs. The new detector enables detecting low-frequency disturbances, which was difficult for previous detectors. Next, we will describe dynamics simulation results. In this simulation, we investigate the effects of imperfections such as misalignment, sizing error, and mass imbalances.

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In this paper a vibration control technique is proposed for a flexible body moving along the axial direction such as plates or wire rods in a mill, and the effect is verified by numerical simulation. The dynamic characteristics of the cantilever beam moving along the axial direction are examined by using Lagrange's equation of motion. It is shown that the vibration of the cantilever beam moving along the axial direction is caused by self-excited vibration, and that optimal damper-spring properties at the beam support point are obtained by examining the stability of a simple vibration model.

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A new reduced-order modeling method for flexible multibody systems is proposed in this paper. This model is designed using the property of mode shapes, natural frequencies and modal mass, as well as real mass, real moment of inertia and center of gravity instead of material properties such as mass density, module of elasticity and volume. To represent elastic deformation during large translational motion and large rotational motion, the momentum and angular momentum of each vibration mode are considered. Because state differential equations are obtained from the equations of motion of multibody systems, all coupling terms are included. Therefore, a highly accurate state-space model can be obtained. As an example of this approach, the application to elastic vehicles to suppress vibration of a car body is studied.

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In this paper, the nonlinear dynamic modeling methods for the virtual design of tracked vehicle are investigated by using multibody dynamic simulation techniques. The results include high oscillatory signals resulting from the impulsive contact forces and the use of stiff compliant elements to represent the joints between the track links. Each track link is modeled as a body which has six degrees of freedom, and two compliant bushing elements is used to connect track links. The efficient contact search kinematics and algorithms in the context of the compliance contact model are developed to detect the interactions between track links, rollers, sprockets, and ground for the sake of speedy and robust solutions. In order to validate the developed nonlinear multibody dynamic model against the experimental measurements, several empirical techniques are suggested and applied to the physical proving ground tests of the high mobility tracked vehicle. In this empirical validations, positions, velocities, accelerations and forces of the chassis and the track sub-systems are correlated accordingly.

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Multi-body Dynamics simulation of tracked vehicles is very useful not only for the analysis of dynamic behaviors, but also for the performance evaluation of the chassis controllers. The track tension is closely related to the maneuverability of tracked vehicles and the durability of tracks and suspension systems. In order to minimize the excessive load on the tracks and to prevent the peal-off of tracks from the sprocket, the track tension needs to be maintained at the optimum level throughout the maneuver. In this paper, a co-simulation tool is developed such that the performance of the track tension control system can be investigated for various maneuvering tasks. The MBD (multi-body dynamics) vehicle model for tracked vehicles is very complicated (189 bodies, 36 revolute joints, 152 bushing elements and 954 degrees of freedom) and cannot be easily implemented in commercial software. Besides, the track tension controller based on fuzzy logic can be easily constructed in the commercial control software. Therefore, co-simulation methodology is proposed so that the designed tension controller is interfaced into the MBD simulation software. The performance of the tension control system is verified through the proposed co-simulation tool.

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This paper introduces an economical and effective full-scale driving simulator for study of human sensibility and development of new vehicle parts and its control. Real-time robust control to accurately reappear a various vehicle motion may be a difficult task because the motion platform is the nonlinear complex system. This study proposes the sliding mode controller with a perturbation compensator using observer-based fuzzy adaptive network (FAN). This control algorithm is designed to solve the chattering problem of a sliding mode control and to select the adequate fuzzy parameters of the perturbation compensator. For evaluating the trajectory control performance of the proposed approach, a tracking control of the developed simulator named PNUVDS is experimentally carried out. And then, the driving performance of the simulator is evaluated by using human perception and sensibility of some drivers in various driving conditions.

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This study is concerned with the motion and vibration control strategy for a flexible-link mechanism composed of smart structures in order to achieve the high performance and stability. Reducing vibration and making positioning time faster are simultaneously required in this system. Technology of smart structures is introduced in the flexible-link system to achieve the vibration reduction. The smart flexible-link is composed of the flexible-link and the piezoelectric film which has the sensor/actuator functions for itself, and so its mechanism is extremely suitable for controlling the vibration. Modeling and control strategy are presented to enhance the motion and vibration control performance.

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A numerical study is made of flow of air in human breathing. A permanent magnet is placed on the nose to create a magnetic field. The permanent magnet is modeled as a coil in which electric current flows, and the passage of air in the human body is modeled as a circular pipe. Airflow is induced by the applied pressure difference between the interior and exterior of the human body. An inhalation flow of constant pressure difference (model I) and a flow of pulsating pressure difference (model II) were examined for unsteady developments of flow, temperature and oxygen concentration, by numerical techniques. Transient responses are affected by both the temperature and oxygen concentrations. Flow of inhalation is enhanced under a magnetic field. High-temperature air, with a low oxygen-concentration, in the passage is repelled from the magnet toward the interior by the magnetizing force, and exhalation is suppressed by a similar mechanism. Suppression in the exhalation overwhelms enhancement in the inhalation, and this tendency is pronounced as the amplitude of pressure oscillation increases.

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The aim of the present study is to obtain a better understanding of skull-brain interface conditions and the influence of the neck region when the finite element human head model under impact loading is constructed. The three-dimensional finite element head model consisting of skin, skull, CSF and neck is constructed based on MRI and CT data. The material properties are adopted from the literature previously published and are homogeneous and isotropic. Next, a crash test is carried out by crashing an iron block impactor on the occipital region of the physical human head neck model in which water is filled and intracranial pressure and head acceleration are measured. The result of the numerical calculation is compared with the result of the experiment for verification of the computer model and good agreement is obtained. The result shows that the tied-type interface condition is preferable than the slide-type condition in order to represent the phenomenon in the physical model. The presence of the neck is important for analysis but the stiffness of the neck seldom affects the intracranial response.

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The natural synovial joints have excellent tribological performance known as very low friction and very low wear for various daily activities in human life. These functions are likely to be supported by the adaptive multimode lubrication mechanism, in which the various lubrication modes such as elastohydrodynamic lubrication, weeping, boundary and gel film lubrication appear to operate to protect articular cartilage, depending on the severity of the rubbing conditions. In this paper, various protective roles of synovial fluid, cartilage surface layer, extracellular matrix and chondrocyte to severe loading are described. In the first part, the protective mechanism by adsorbed films and underlying gel films was described on the basis of the frictional behaviors of articular cartilage against articular cartilage or glass. It was discussed that the replenishment of gel film removed during severe rubbing is likely to be controlled by supply of proteoglycan from the extracellular matrix, where the chondrocyte plays the main role in the metabolism. In the second part, the time-dependent local deformation of biphasic articular cartilage under constant total compressive strain condition was evaluated in the finite element analyses. The importance of clarification of actual stress-strain in chondrocyte was indicated in relation to the tribological property of articular cartilage.

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This paper describes the effects of shear stress and exposure time on the prediction method for the Index of Hemolysis using computational fluid dynamics (CFD) with a modified turbulence model in an orifice-pipe blood flow, which is a simple model of turbulent shear stress induced hemolysis in a high-speed rotary blood pump. Using CFD with the partially patched modified k-ε model (LK (Launder-Kato) Zonal model), the results of the flow field in the orifice-pipe flow are compared with those of standard low Reynolds number k-ε model at whole region (standard model: STD), and it is found that the shear stress by the LK Zonal model is predicted more precisely than that by STD model by comparing the pressure loss in the orifice and the reattachment length in the experiments. As for hemolysis, from the computational data of orifice-pipe flow, the index of hemolysis is estimated using (1) only shear stress, and (2) shear stress and exposure time, and it is found that the prediction method using only shear stress is more accurate than the method using shear stress and exposure time. From these results, the most suitable estimation method to predict hemolysis is the prediction considering only shear stress and constant exposure time using CFD in rotary blood pumps.

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The authors have proposed a simulation approach for estimating a ski turn and have numerically obtained various useful results on the ski turn using the simulation approach. A coupled motion between the ski and snow slope is caused by a skier's ski control during the ski turn. In the simulation approach the coupled motion must be analyzed. In the present study, a numerical approach to the coupled motion is justified by comparing the numerical results with the experimental ones. In the first experiment, the ski's motion due to an impact force is measured in order to consider the repeatability of the experiment and the justification of the numerical approach. In the second and last experiments, the ski's motion due to the skier's ski control is considered in order to justify the numerical approach to the coupled motion. Furthermore, the edging force applied to the ski by the skier during the ski control is measured.

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Deployment behavior of modularized structures is numerically analyzed from the viewpoint of synchronism. Elastic panels with single and double accordion folding patterns are examined as examples of modularized structures. Through computer simulations, it is shown that asynchronous deployments are caused by inertia forces. To improve the synchronism of the deployment, an autonomous distributed control method is introduced. Because the control method uses only local information, some advantages are expected; parallel processing, flexible extensibility and fault-tolerance. The control rule is derived by the analogy of heat conduction. Stable characteristic of heat conduction implies stability of the control method. Furthermore physical sense of control parameters can be understood intuitively because the control method is based on real physical phenomenon. It is confirmed that the autonomous distributed control can improve the synchronism of the deployment.

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An autonomous distributed control has been presented as novel control methods for complex or large systems. In this paper, it is applied to the position control of variable geometry trusses, which have high redundancy. It is shown that the fault-tolerance of the system is easily realized through this control method. Additional behavior for obstacle avoidance is also accomplished easily. Furthermore, the area of avoidable obstacles can be extended through the cooperation of each agent. Compared with a conventional control method using inverse kinematics, the proposed method is shown to be more effective from the viewpoint of calculation time.

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In this paper, model reference adaptive control of a cantilevered flexible beam with Kelvin-Voigt damping and unknown spatially varying coefficients is investigated. Any mechanically flexible robots/structures are inherently distributed parameter systems whose dynamics are described by partial, rather than ordinary, differential equations. Adaptation laws are derived by the Lyapunov redesign method on an infinite dimensional Hilbert space. To show the well-posedness of a coupled nonlinear system, combined state error and parameter estimation error equations are constructed as an initial value problem of an infinite dimensional evolution equation in weak form. It is then shown through the Lyapunov redesign approach that the state error actually converges asymptotically to zero. With an additional persistence of excitation assumption, the parameter estimation errors are shown to converge to zero as well.

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For a linear system with matched uncertainties, a variable structure model following controller using output feedback is developed in this paper. Although the system contains an uncertain term, a novel reduced-order observer proposed in this work can effectively estimate the system states. Based on the estimated states and the observer model, although the system exists matched uncertainties, the proposed controller can satisfy the reaching and sliding condition after some finite time. Moreover, when the system is in sliding mode, it can be shown theoretically that the tracking error decreases asymptotically to zero. Finally, a numerical example is given to demonstrate the feasibility of the proposed scheme.

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The present paper investigates the impact vibration in a single degree-of-freedom system having symmetric two-sided stops subjected to harmonic excitation. Periodic asymmetric two-impact/one-period motion, three-impact/one-period motion and symmetric four impact/one-period motion are determined analytically and numerically, and the corresponding stabilities are analyzed. Regions of stable periodic motion are given in the δ-Ω plane, where δ denotes the clearance between the mass and the stop at the rest and Ω denotes the frequency of harmonic excitation. Bifurcation diagrams relating the impact-velocity and a system parameter are also presented. Period-doubling bifurcations, fold bifurcations, grazing bifurcations and chaotic motion are obtained. The grazing bifurcation is peculiar to the vibro-impacting system. In addition, the invariant curves for the system parameters for which chaotic motions arise are presented.

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A double cantilever sandwich-beam method is proposed for the evaluation of the frequency dependence of the dynamic elastic modulus and material loss factor of rubber materials. The flexural vibration of a double cantilever sandwich-beam specimen with an inserted rubber layer was studied using a finite element simulation in combination with a sine-sweep test. Effects of the rubber layer length on the dynamic characteristics were also investigated such that reliable values were measured when the length of the inserted rubber layer was larger than or equal to 50% of the effective specimen length. The values were compared with those obtained by dynamic mechanical analysis and a simple resonant test. The relationships of the dynamic characteristics of rubber materials with frequency could be determined using the least squares estimation method.

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A theoretical model was studied to describe the sound radiation created by surface vibration of in-service tires. The tire is modeled as a circular ring model. The effects of normalized frequency and the structural loss factor are included. The radiation sound power is calculated as a function of the normalized frequency and the structural loss factor through numerical integration of the sound pressure. The basic sound radiation mechanism is shown to be a damped progressive wave field on the structure in the vicinity of the applied force. The result indicates that the potential sound reduction might be obtained if the values of the normalized frequency and structural loss factor are determined.

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A set of theoretical models has been prepared which describes the noise generated by tire/road interaction. The mechanisms are considered to be air pumping and carcass vibration. The models begin with a set of thin shell equations describing the motion of the belt of a radial ply tire, as derived by Böhm. The structural quantities required for these equations are derived from the material properties of the tire. The rolling shape of a tire is computed from the steady-state limit of these equations. Air pumping (monopole radiation from head voids) is calculated by assuming that tread elements move passively on the deformed tire. The vibration response of the tire is treated using full time-dependent shell equations. The force input at the tire/road interface is calculated on the basis of tread geometry and the distribution of contact patch pressure. This input is physically equivalent to the impulse distribution models widely used in the tire industry for tread pitch randomization. The subsequent radiation of sound is calculated by a Raleigh integral. These models have been embodied into a unified set of computer programs. Using the programs, the effect on noise of various tire design variations is determined and discussed. Trends that lead to low-noise design are identified. A series of experiments are planned which will test the validity of the models and provide a basis for their refinement before final documentation and dissemination.

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Finite element structural dynamic models are typically validated using data obtained from a modal testing. Although it is known that test variability may affect the verification, the test variability is typically ignored in the verification process. This paper describes the sensitivities of cross orthogonality check to the test variability. The cross orthogonality check is one of correlation techniques which is gaining acceptance in the structural dynamics community, because of its improved accuracy over the standard modal assurance criterion. Then an uncertainty index of the cross orthogonality check is proposed based on the fact that the sensitivities are much dependent on sensor placement. The results of some artificially generated test cases are presented to demonstrate the applicability of the proposed approach.

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In this paper, we propose an intelligent control method in which IMC control is combined with neural networks (NN). Internal model control (IMC) has a number of advantages for enhancing control performance. IMC can minimize disturbance greatly. IMC is attractive for industrial users because it has only one tuning parameter. The IMC is significant because the stability and robustness properties of the structure can be analyzed and manipulated in a transparent manner, even for nonlinear systems. On the other hand, NN is used to get the suitable control parameter when the plant contains non-linear elements. We apply the proposed intelligent control method for a pneumatic servo system which usually contains non-linearity. The effectiveness of the proposed design method is confirmed by experiments using the existent pneumatic servo system.

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This paper investigates the stability robustness of linear continuous/discrete-time systems with output feedback controllers as well as both time-varying structured and unstructured parameter uncertainties by directly considering the mixed quadratically-coupled uncertainties in the problem formulation. Based on the Lyapunov approach and some essential properties of matrix measures, some new sufficient conditions are proposed for ensuring that the linear output feedback systems with both time-varying structured and unstructured parameter uncertainties are asymptotically stable. Three numerical examples for continuous-time and discrete-time systems are given to illustrate the application of the presented sufficient conditions, and for the case of only considering time-varying structured parameter uncertainties, the proposed sufficient conditions are shown to be less conservative than the existing ones reported in the literature.

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This research develops a reliable and systematic low-order controller design method for solving model-matching problem of linear discrete time-invariant multi-input multi-output system. Using the coprime factors and properties of discrete outer function, the low-order controller design is reformulated as a convex optimization problem. The solutions are obtained using linear matrix inequality techniques. An IEC turbofan engine is used to illustrate the model-matching design algorithm.

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The iterative learning control (ILC) learns the unknown information from repeated control operations. The tracking error from previous stages is used as the correction factor for the next control action. Therefore, the ILC controller can make the system tracking error converge to a small region within the limited numbers of iterations. In this paper, a proportional-valve-controlled hydraulic cylinder system with repeated external loads is built to perform the position tracking control experiments. The PID and ILC controllers are implemented in these experiments and the results are compared. The P-type update law with delay parameter is used for its position tracking control. Experimental results show that the ILC controller can effectively controls the system to track the repetitive position trajectory, especially in transient response that traditional control methods can't follow appropriately. Therefore, in this application, the control performance of the ILC is superior to the traditional PID controller.

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Design optimization has been performed for the suspension system of high speed train. Neural network and design of experiment (DOE) have been employed to build a meta-model for the system with 29 design variables and 46 responses. A combination of fractional factorial design and D-optimality design was used as an approach to DOE in order to reduce the number of experiments to a more practical level. As a result, only 66 experiments were enough. The 46 responses were divided into four performance index groups such as ride comfort, derailment quotient, unloading ratio and stability index. Four meta-models for each index group were constructed by use of neural network. For the learned meta-models, multi-criteria optimization was achieved by differential evolution. The results show that the proposed methodology yields a highly improved design in the ride comfort, unloading ratio and stability index.

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