This paper proposes an innovative vibration testing method for membrane structures based on impulse response excited by laser. Non-contact impulse force is generated by irradiating a high power pulse laser to a structure. The laser excitation makes a precise measurement of the frequency response in wide frequency range possible because an ideal impulse force is applied to a point on the structure. Using a laser Doppler vibrometer to detect a response of the structure, both non-contact laser excitation and measurement are achieved in the vibration testing system. Furthermore, a vibration measurement of the membrane structure in vacuum environment is effectively conducted by using the proposed vibration testing method with a vacuum chamber. The validity of the present vibration testing system is verified by evaluating the measured data of the membrane structure in the vacuum chamber.
High-polymer piezoelectric films are flexible sheet-like element and are attractive materials to construct super lightweight flexible structure in which sensor and actuator elements, and thus active damping abilities are contained in the structure itself. However, active multimodal vibration damping of flexible beams using distributed piezoelectric film sensors/actuators is difficult due to the interaction between structural system and electrical system, and so on. In this paper, a noncollocated vibration control method of a flexible beam, in which piezoelectric film sensors and actuators were shaped using different shaping functions, was investigated. Fundamental equations were summarized and were transformed into the modal space. By considering phase characteristics and polarity of the distributed control systems in high order modal frequencies, multimodal control will be implemented. Finally, preliminary results using a manufactured simply supported beam were shown.
A multidisciplinary design optimization method is presented to improve performance of vibration control for smart laminated composites. The smart structure consists of a graphite-epoxy laminated plate and piezoelectric (PZT) actuators. Design variables of the multidisciplinary design optimization method are actuator placements, weight parameters in the H_2 control system, and lamination parameters which describe lay-up configurations of plates in simple form. A genetic algorithm method is employed as an optimizer. The results of the multidisciplinary design optimization agree well with the results of the real-time control experiment, and the present results indicate improved performance in vibration control whey they are compared to the plates composed of typical lay-up configurations.
This paper describes a new method to improve the equivalent stiffness ratio of a piezoelectric element attached to a beam using negative stiffness composed of negative capacitance and another piezoelectric element. The bending stiffness of the beam wherein the piezoelectric elements is attached is reduced by the negative stiffness. The optimum height of the spacers of the piezoelectric element for vibration suppression was theoretically formulated including the effect of the negative stiffness. The condition that the negative stiffness device yields damping effect was also theoretically investigated. The effectiveness of the proposed method was verified through simulations and experiments.
Our novel invention: "digital self-powered autonomous" vibration controller using a digital micro-processor is presented. The invented unit is a completely self-powered control system that does not require any external power-supply at all. Nevertheless, this digital, self-directive, and self-powered approach enables the system to be programmable and thus versatile in control scheme. The digital-autonomous controller is much more advanced and progressive than conventional analog-autonomous ones that are clumsy and awkward. This digital system can be implemented in multiple-input multiple-output systems to suppress even complicated structural vibrations. This is quite useful for various applications to energy-saving or energy-shortage systems, such as large space structures, artificial satellites, and isolated lunar bases, which all are vulnerable to long night-time without solar-power.
Smart structures technology that uses piezoelectric element etc. is effective for the vibration control of small devices. However, for micro devices, it is difficult experimentally to measure and evaluate the vibration control characteristics of the system with control. Namely, it is not realistic to install an external exciter or to apply the excitation force with an impulse hammer. Therefore, in this study, the vibration property is measured and evaluated by using the noncontact excitation technology using laser ablation and the noncontact measurement with Laser Doppler Velocimeter. Since both input excitation and output measurement are made without contact of apparatus and the excitation force has a high reproducibility in the present system, the efficiency and the reliability of the measurement can be improved.
An energy regenerative active vibration control method using piezoelectric actuators, class D drivers, output filters and sliding mode controllers is proposed by the authors. DC voltage sources are used as power sources in the previous study and capacitors which can store regenerated energy also can be used as power sources. Class D drivers and output filters consist of switches and passive electric elements. Therefore, systems using capacitors as power sources can be considered as semi-active systems. Voltages of capacitors used as power sources are not constant because the capacitors are charged and discharged in control processes. An advantage of the proposed method is that characteristics of closed-loop systems are independent from voltages of power sources when systems are in sliding mode conditions. The advantage is suitable for systems using capacitors as power sources. The validity of the semi-active control method based on the proposed method is shown by numerical simulations of a SDOF model.
Because electro-magnetic actuators have both functionalities of actuation and sensing, they have potentials of sensorless vibration control as piezoelectric elements do. This paper discusses an implementation of a digital virtual impedance circuit with a R or RC circuit optimally designed by a theory of passive dynamic damper. The digital virtual impedance circuit, which consists of a computer and a controlled voltage source, can realize an arbitrary impedance. Using the virtual impedance concept, the optimally designed resistive component which might have negative value can be realized, even though conventional electro-magnetic shunt damping suffers from performance degradation.The experimental results demonstrate the effectiveness of the method.
In this paper, it is clarified by experimental results that the impedance of a piezoelectric structure changes depending on experimental conditions such as the temperature and the relative humidity. Therefore, a new electrical model,that takes the resistance variance of a piezoelectric structure into consideration's proposed. The electrical impedance model of a piezoelectric structure is derived by using the proposed electrical model. Linear and nonlinear least squares methods are proposed for parameter estimation of piezoelectric elements based on impedance measurement. The parameter estimation experiment that uses the impedance analyzer is performed. The proposed electrical model is compared with the conventional electrical model, and it is verified that the frequency response of the model obtained by using the proposed electrical model shows a good agreement with that of the measured impedance. Moreover, it is confirmed by the value of the obtained parameters that relative humidity affects the resistance variance of a piezoelectric structure.
In the previous authors' study, the vibration energy harvester of the piezoelectric bimorph cantilever type was proposed for vibration condition monitoring applications of rotating machinery. Proposed energy harvester consists of the surface bonded two Macro-Fiber Composites (MFCs). In this study, theoretical maximum energy transfer efficiency was derived from the energy balance equation during the natural period of the proposed vibration energy harvester. The maximum AC power through 227.3 Kilo-Ohm resistor which includes instruments internal resistances experimentally obtained 246.1 microwatt when subjected to vibration source input magnitude of 0.71(mm/s rms) at the resonant frequency of the harvester (29.31 Hz). The impedance matching between MFCs and the electrical resistive load was effective for maximizing both AC and DC power transfer of the vibration energy harvester. Theoretical maximum energy transfer efficiency was 18.25%. However, the theoretically estimated energy transfer from mechanical system to electrical system did not obtain the good agreement with the experimentally evaluated maximum AC power during the natural period of the vibration energy harvester.
Bolted joints are widely used in mechanical and architectural structures. However, many serious accidents occur because of loosening in bolted joints. The conventional methods of the bolt loosening inspection require the use of special measurement equipment and human operation. It is difficult to conduct inspections in dangerous places, such as atomic power plants, space stations and bridges. In this study, a smart washer was proposed to detect the bolt loosening without human involvement and to achieve continuous monitoring. The smart washer which consists of the flexible cantilever beam enables to detect bolt loosening by using self-sensing and actuation functions of piezoelectric material. The subject of this paper is the power supply system of the health monitoring by using the smart washer. Applying energy harvesting system by piezoelectric vibration is proposed in this paper. Experimentation was performed to evaluate the charge characteristic by piezoelectric vibration power generator. This paper describes some conditions of piezoelectric vibration power generation when the use of a smart washer on the bridge.
This study concerns a electromagnetic vibration energy harvester with a nonlinear oscillator. The nonlinear oscillator can have multiple stable steady-state responses in resonance band typically the large and small amplitude solutions depending on the initial condition. We introduce a self-excitation circuitwith a variable resistance which varies from negative to positive as function of the induced voltage in order to enable the oscillator entrained by the excitation only in the large amplitude solution. This controlled resistance enables the oscillator to be entrained by the excitation in a large amplitude solution. In this paper, the matching condition of the load resistance for the nonlinear vibration energy harvester is mainly discussed. It is shown that the optimal load resistance is derived in a simplified form based on the approximated solution obtained by the averaging method.
Authors have applied the skyhook control that does the controlled variable proportional to the road displacement in feed-forward to the electric preview active stabilizer suspension system that is called eActive2 so far, and have verified the performance. Moreover, authors examine the preview control that is the means to make amends for the response delay of actuator by calculating the controlled variable based on road information forward, and have verified the effectiveness. Authors applied the preview control verified with eActive2 to eActive3, which became possible to control three modes by having made actuator in the rear of eActive2 become independent, and verified the ride comfort performance. As a result, the ride comfort performance of the roll direction achieved the effect of equal eActive2. In addition, vibration transmissibility to the body in rear and Rear load-deflection have been improved. The ride comfort performance of the in case for the road displacement to control the preview with eActiveS was verified.
In this work, the conventional vehicle suspension consisted of damper and coil spring is replaced by a colloidal cylinder, which accommodates a colloidal solution obtained as a mixture of lyophobic nano porous silica gel powder and water. Since water is forced to penetrate the nano pores of lyophobic silica gel during compression process, but naturally exudes due to the action of the surface tension during extension process, the restoring force is intrinsically achieved, and the colloidal cylinder works both as a spring and damper. Firstly, the ride comfort was experimentally evaluated on a one-degree of freedom suspension model bench device. Then, the ride comfort and the rolling attitude were experimentally evaluated from random excitation and travel tests on a passenger car. A through comparison between the performances of conventional suspension and the proposed colloidal cylinder was performed.
Recently, unmanned helicopter is widely used for crop-dusting, overhead wiring work, aerial photographing, etc. This paper describes how to control and design parameters for a helicopter slung load system. Recent studies on the system have proposed control methods to suppress the residual vibration. But, in many instances, they used state estimator and accurate modeling of the helicopter and slung load system. We focus on the case that slung load is attached to the helicopter had been designed for a solo flight. The present method gives reference values to the postural control of fuselage to suppress the residual vibration and the reference value calculated by delayed feedback. Therefore, this method needs no state estimator and no accurate system parameters. Further, to design control parameters, we propose a simple design approach based on root locus of a plane model. The effectiveness of the present control method is verified by experiments. The control parameters designed by cut-and-try experimentally correspond to the parameters designed by the presented simple design approach.
The authors have been studying on the method for reduction in contact force fluctuation between catenary and pantograph using active control techniques. The active pantograph presented in this study has a pneumatic cylinder as an actuator, which is controlled to apply a control force to the lower frame of the pantograph so as to suppress the contact force fluctuation based on the impedance control methodology. The pneumatic actuator, however, shows a strong nonlinearity due to the flow characteristics of the flow valve, the friction at the cylinder, etc. This nonlinearity results in an error in the actuator force and degrades the control performance. This paper focuses on suppressing the influence of the nonlinearity on the relationship between command signal and generated force by means of pressure compensation of pneumatic cylinder. The differential pressure in the air cylinder is measured and fed back to the pressure compensator. The compensator calculates the difference between the measured differential pressure and the required one to generate the prescribed force and generates the command signal on the basis of the FED control law. The vibration test for the actively controlled pantograph shows that the contact force fluctuation is obviously suppressed by installing the pressure compensator.
Some conventional railway tracks are subject to lower maintenance criteria, unlike Shinkansen lines. This usually implies large vertical irregularities and/or depressions at the rail joints, which are a known cause of vertical rigid-body-mode vibration of the car body. Since suppressing such vibration is necessary for improving ride comfort, a secondary suspension damping force control system with variable vertical dampers (a vibration control system) is being developed. For improving the performance of vibration suppression of the system, this paper proposed a control technique taking into account forced vibration caused by running through depressions at the rail joints. While the vehicle runs at a constant speed, the frequency of the forced vibration stays constant. Therefore, the weighting functions for controlled variables are set with a large value at the frequency so as to reduce the forced vibration selectively. Numerical simulations using 7-DOF vehicle model with variable secondary vertical damper were carried out, and the proposed algorithm can effectively suppress vertical rigid-body-mode vibration of the car body.
Recently, railway vehicle are becoming lighter since it corresponds not only to the improvement of the running speed but also to the reduction of running cost and noise. However, this causes the increase in a vertical vibration of car body. In addition, the deterioration of riding comfort concerns to this issue, because the natural frequency of the above mentioned vertical vibration overlaps with human's uncomfortable sensitive frequency band (around 6-10Hz). Up to now, there have been many strategies for the vibration suppression, i.e. a method to conduct active control for the secondary suspension system between the body and bogie, and a method to attach visco-elastic layers and constraint layers on the outside sheathing of the car body. The authors introduced the smart structure concept to the active vibration control of the railway body. Stack type piezo-electric actuators were used and good control performances were obtained for elastic vibration by experiments for 1/6 scale model. And rigid body vibration was also controlled by linear actuators. In this study, only air cylinders were used, because normally train system has pneumatic source. Simulation studies and experiments using scale model were conducted, and the effectiveness of the proposed control was confirmed.
Recent light-weighted railway vehicle carbodies tend to have complicated three dimensional vertical elastic vibrations and such vibrations affect riding quality. In particular, the modes similar to the first bending mode of free supported elastic beam ("B mode") and diagonal distortion mode ("D mode") are important because natural frequencies of the two modes are around lOHz which is known to be a sensitive frequency range for human. A method to reduce the two elastic vibrations simultaneously with two active mass dampers (AMDs) was proposed in our previous researches and the validity was confirmed. As a next step, we are trying to develop a more practical AMD system with smaller and lighter actuators and more effective control law. In order to study the specification of actuator, such as maximum force and maximum stroke, a number of numerical simulations in time domain have to be carried out, therefore, we need a compact numerical model of a railway vehicle including AMDs. In this paper, examined a method to obtain reduced model with small DOF by using modal analysis is proposed, and the accuracy of the modal is examined by comparing with measurement results. By using the reduced model, the suitable specifications for the practical AMDs are studied numerically.
This paper deals with a non-contact transportation system using ultrasonic levitation. It is the purpose of this paper to realize the two-dimensional non-contact transportation using a transversely infinite plate. To perform the precise positioning of a target object, both the levitation and transportation forces are essential. With an aim to generate these forces, if a finite plate is excited at ultrasonic frequency, a lot of vibration modes are then likely to be activated, and hence a traveling wave indispensable to the transportation force may not be generated. If an infinite plate is excited, the vibration modes do not give rise to, however the deflection amplitude of the panel is too small to generate the levitation force. To overcome this problem, a rectangular plate which has a pair of simply supported edges and a pair of anechoic boundaries is employed, thereby the transportation of the target object becomes viable due to a large amplitude of levitation force gained because of the boundary condition setup. To this end, a vibration analysis of an infinite plate is conducted, revealing the power flow emerging in the vibration field. Furthermore, control forces are introduced for the purpose of transporting the target object along the designated direction. With a non-contact transportation system designed which consists of a transversely infinite plate and four Langevin transducers, an experiment on the position control of the target object is carried out, demonstrating the validity of the proposed method.
It is clarified to be able to separate by using the jump of the object with different contact surface's gap by using the Elliptical vibration that exceeds the jump limit by a current research. We examined that influence given to the jump, the transportation speed, and the stability of transportation of the object by changing driving frequency. Because the resonance is used in a past experiment machine, driving frequency cannot be changed. First, we produced the new experiment machine that was able to generate the elliptical vibration by desired driving frequency. Next, we examined the influence of driving frequency given to the stability of separation, by measuring the behavior of the separation when driving frequency is changed. Then, we examined the influence of driving frequency given to transportation speed, by measuring transportation speed of the object when driving frequency is changed. Finally, we try the stabilization of the separation and transportation of small electronic parts of the size by changing driving frequency.
To use elliptical vibration, we can supply and separate the work which material and shape is similar at the same time. When the vertical vibration of elliptical vibration is larger than 1.0G, works jump and the characteristics of transportation change considerably. But some works don't jump because negative pressure is caused on contact face. As a result, it is possible to separation and transportation by the presence of jump. However, it is difficult to separate works with little difference or tiny works. The present study shows that optimal driving condition of these works. First, we examined that the influence of driving frequency on jump for stabilized separation. Next, we examined relationship between the state of contact face and characteristics of transportation for separate more quickly. From a result of these examinations, we get optimal driving condition of the tiny work with little difference in the face side and reverse side. In this condition, we could separation and transportation a lot of works at fast and stable using elliptical vibration.
This paper deals with an active wave control of a two-dimensional flexible structure. The objective of this paper is to present the feedback wave control for a rectangular panel and to theoretically lay out the characteristics of the control system. Firstly, the transfer matrix method is extended to the Laplace domain. Next, control laws for suppressing a wave propagating between a disturbance point and control point and corresponding characteristic equations are derived. Moreover, the control effects of the control system are presented from a viewpoint of a numerical analysis. It is found that the proposed method can eliminate the designated wave. Finally, the stability of the control system is clarified by Nyquist diagram,.
The estimation of steering characteristics such as steer feeling by using only computer simulation technology is extremely difficult. In this paper, to solve this problem, we consider the reproduction of behavior of steering wheel and the control method with developed computer simulation and steering simulator when the road surface condition changed suddenly. Considering the sudden change of the road surface condition to be disturbance, the disturbance compensator for suppression control is designed. In addition, we propose a controller design procedure for electric power steering (EPS) systems to develop the control method efficiently. First, we analyze the behavior by steering simulator or actual car and construct the human model for the computer simulation of EPS systems. Next, we design outline of the disturbance compensator by the computer simulation using the human model. The disturbance compensator is also designed in detail with experiments of the steering simulator, and it will be designed finally by experiments of the actual car.
This paper describes a method for estimating the crosswind disturbance and the transverse slope affecting a passenger vehicle that is travelling in a straight line. It also discusses a compensation control system that uses electric power steering to provide steering assistance to the driver. Under ordinary driving conditions, the aerodynamic sideslip angle remains small, and therefore, the center of pressure remains reasonably stable. In this study, a constant center of pressure is assumed, and a lower-order disturbance observer is designed so as to reduce the computational cost of the implementation. The transverse slope is estimated independently of the crosswind, and the compensation torque of the electric power steering system is determined by the crosswind component. Vehicle dynamics simulations confirmed that the yaw rate could be reduced by using the proposed quartic disturbance observer.
In this study, a vehicle dynamics controller for an active steering vehicle is designed using the concept of Smith compensation to mitigate the effect of the driver' s response time to the lane following characteristics. The design method is based on the explicit consideration of the response time so that the proposed controller is suitable for an aged driver who tends to react sluggishly. Numerical simulation results are provided to show the robustness of this approach to the modeling error of the response time. The behavior of the driver-vehicle system remains almost unchanged even when the controller is tuned for an aged driver and the vehicle is steered by a younger person who responds promptly within a typical dead time.
Operations of hydraulic excavators require high operation skill and operators have possibilities to work in unsafe environment. To solve these problems, automatic digging control is often studied, but there are few studies focused on improvement of efficiency. A high efficiency digging algorithm for a hydraulic excavator has not been established because the relationship between digging parameters and digging performance is complex. A simulation model which is able to consider interaction between soil and machine would uncover a digging algorithm for improving energetic efficiency. In this paper, an example for improvement of digging efficiency is shown by our developed distinct element method (DEM) simulation. First, validity of digging performance evaluation with developed simulation is shown by developed digging test device. The device reproduces excavation by driving soil packed container with three motors and by rotating bucket with a motor. And it can measure digging resistance by force sensors and calculate digging energy. Digging simulations are conducted by our suggested automatic digging algorithm. Varying control parameters, influences of control parameters are estimated. Our research evaluates effectiveness of model-based development for automatic digging which enhances productivity.
In this investigation, hunting stability of new-type independently rotating wheelset (IRW) which has negative tread conicity for improving curving performance is discussed. To this end, equations of motion of IRW with negative tread conicity are derived and used for the stability analysis. It is demonstrated that unstable hunting motion occurs in this type of wheelset and the hunting frequency decreases as the speed increases, which is totally different characteristics from those of the conventional wheelset. The cause of such unique vibration characteristics are investigated from an energy point of view, and the effect of coupling terms resulting from the wheel/rail creep forces on the stability of the hunting motion is discussed using the equations of motion in a block diagram form. Furthermore, hunting stability of one-axle IRW truck with negative tread conicity is discussed. It is presented that the truck hunting motion can be stabilized by adequate choices of primary suspensions.
In this paper, the front-steering assist control is designed to stabilize a motorcycle during braking. The rider-motorcycle system with its pitching motions is linearized around an equilibrium point of quasi-steady state straight running with a constant deceleration. From the viewpoints of eigenvalues and frequency responses, the linearized model is analyzed and a reduced-order model is obtained to design the control system by using H_∞ control theory. By carrying out simulations during braking, it is demonstrated that the control system can stabilize a motorcycle when receiving a sudden disturbance from the front wheel and is robust against parameter variations and several braking situations.
Collision Mitigation Brake (CMB) is a part of Pre-Crash Safety System that can recognize the possibility of collision and assist brake operation to reduce the impact or mitigate damage to the driver and passengers during vehicle collisions. In this study, the effects of CMB in head-on collision on curved road are investigated and the influences of the correction in radar direction are studied. A vehicle dynamic simulation model was constructed and simulation was carried out with different velocity, curve radius, Time-to-Collision (TTC) and steering angle. In addition, differences of collision speed reduction between vehicle with correction in radar direction and vehicle without correction in radar direction were evaluated.
This paper discusses the feasibility of a longitudinal and lateral direction integrated flight control system for UAV (Unmanned Aerial Vehicle). From the numerical simulation results, the UAV with the flight control system designed based on a longitudinal and lateral directions decoupled linearized model indicates strong cross-coupling effect between the motions in longitudinal and lateral directions as the angle of attack increases in rolling phase. Therefore it is desirable to design a flight control system considering the cross-coupling effect between the motions in longitudinal and lateral directions. In order to cross the coupling effect, a longitudinal and lateral direction integrated linearized model is designed and a robust control technique based on H_∞. control method is employed to design the longitudinal and lateral direction integrated flight control system. The designed flight control system is applied to the UAV and the performance is verified through the six-degree-of-freedom nonlinear simulation at high angle-of-attack in rolling phase. The designed flight control system demonstrates satisfactory performance that cannot be achieved by the controller designed in a decoupled manner.
A kind of an air cushion vehicle (ACV) is known as a hovercraft which carries out a cruise by blowing off the air from the bottom of the body. The ACV has many advantages, such as amphibian vehicle, large payload, and so on. However, the ACV has drawbacks such as its drivability is bad. An improvement of the drivability is effective for the control of the ACV and the disturbance rejection performance of the controller is very significant. In this research, the position of the ACV is estimated with the image recognition using external maker by ARToolKit. Information on the marker is registered beforehand, the distance is requested from the size of the marker seen from the camera, and posture is requested from the shape of the marker. When the ACV runs on the straight and arc, the ACV is kept on the path by the designed controller. The usefulness of the designed controller is confirmed through the simulation and an experiment.
This paper describes an application of unmanned flying observation robot which can be used to survey disaster area and transmit real time video image to distanced headquarter. In addition, the field experiment was successfully performed in the experimental disaster area.
This paper presents control system design for occupant lower extremity protection in the event of a frontal car crash. A semi-active knee bolster is used to protect occupant lower extremities. The semi-active knee bolster varies the damping coefficient of the knee bolster. The control system design of the semi-active knee bolster is based on a design method of an active knee bolster. LQI (Linear Quadratic Integration) control with an initial value compensation input is applied. We obtain an optimal reference signal of the contact force between the knees and the instrument panel by considering characteristics of the semi-active actuator and the closed loop control system. The control system of the semi-active knee bolster follows the reference signal of the contact force. The protective control system with the semi-active knee bolster is effective for reducing the femur load, verified by carrying out simulations.
It is important to verify seismic capacity in recent years. Seismic vibration test using actual structures is most effective way to verify seismic capacity. However, a huge structure, for example atomic power plant, is difficult to do the seismic vibration test using the actual structure. So, we develop new seismic experimental system applying HILS (Hardware In the Loop Simulation) concept to vibration test. In this way, shaking table test and a computational response analysis are combined on a real time basis. This HILS dynamic test system use only a part of structures to analyze vibration response. This paper verifies stability of HILS dynamic test system in simulation.
In sampled-data positioning control systems, the positioning control system must avoid exciting mechanical resonances around the sampling frequency. To solve this problem, we have developed the control method that can suppress the residual vibrations above the Nyquist frequency in the sampled-data control system. The mechanical vibrations in the sampled-data control system are affected by the sampler and hold. As a result, we cannot estimate the amplitude of the vibration in steady-state characteristics. Therefore, this study has been based on shock response spectrum (SRS) analysis that handles the transient-state characteristics of mechanical resonances. The control method uses multi-rate notch filters that modify the acceleration input signals. The results of SRS analysis show that the multi-rate notch filter can decrease the amplitude of residual vibrations caused by the mechanical resonances around the sampling frequency.
This paper proposes a controller design method of 2-degree-of-freedom system by Model Bridge Control. Model bridge control is the Multi-Freedom control theory and can compensate for each control problem, e.g. robust stability, reference input and disturbance responses. In this paper, we applied a robust controller design method using Model Bridge Control to resolve a spillover problem. It is important to resolve the spillover problem which an ignored elastic mode becomes unstable in. By Model Bridge control, an un-modeled dynamics is treated as a model error and is compensated by an error compensator which is designed based on gain and phase of the model error. We verified from simulations that Model Bridge Controller with the error compensator has a high robust stability. On the other hand, a control system without the error compensator became unstable owing to the spillover effect under the same condition. Therefore, the effectiveness of the proposed method is clarified.
This paper investigates a feedforward control technique for saving the operating energy of a 2-DOF flexible manipulator with a point-to-point (FTP) motion, in which the residual vibration also can be suppressed. The 2-DOF manipulator has one prismatic joint and one revolute joint. In order to obtain a mathematical model properly, the flexible manipulator is modeled by considering the axial displacement due to large bending deformation. The Lagrangian approach in conjunction with the assumed modes method is applied to derive the equations of motion of the manipulator system. For the FTP motion task, the trajectory of the translational motion is set to a cycloidal motion. On the other hand, the trajectory of the rotational motion is designed to simultaneously minimize the residual vibration and the operating energy. In the present method, we attempt to express the trajectory of the joint angle by an artificial neural network (ANN), and then a vector evaluated particle swarm optimization (VEPSO) algorithm, which is a multi-objective optimization algorithm, is used for learning the ANN. By operating the manipulator along the trajectory obtained by the proposed method, the residual vibrations can be suppressed under the minimum energy condition. The numerical simulation results are compared with the experimental results; this comparison reveals the applicability and effectiveness of the proposed method.
The 5-DOF self-bearing motor possesses the functions of a motor, two radial AMBs, and an axial AMB. Therefore, it is possible to miniaturize the AMB system with maintaining high performance. In this paper, interior permanent magnet (IPM) type 5-DOF self-bearing motor is proposed. The IPM rotor generates bias fluxes to not only the radial direction but also the overhanging stator direction without side surface permanent magnets. Optimum configuration of permanent magnet is analyzed using 3 dimensional finite element method. The results showed the feasibility of the more compact and high reliable 5-DOF self-bearing motor.
This paper describes a 2 DOF magnetic suspension system for an iron stick type object using a rotary geared motor and a disk magnet. In this system, the suspension force is provided by a disk-type permanent magnet and is controlled by a magnetic flux path control mechanism. This suspension system must control two degrees of freedom of an iron stick for complete noncontact suspension. A vertical displacement and a horizontal rotation of the object should be controlled. This paper proves the feasibility of the noncontact suspension system for such a system by controlling these two movements simultaneously. A theoretical analysis will be done on the model of this suspension system and a numerical simulation validate the feasibility of the system.
Series magnetic suspension is applied to force measurement. In a double series magnetic suspension system, two floators are suspended with a single electromagnet. The attractive force of the electromagnet directly acts on the first (upper) floator in which a permanent magnet is installed. The motion of the second (lower) floator is controlled indirectly through the attractive force of the permanent magnet. When PID control is applied to the second floator, the first floator displaces proportionally to external force acting on the second floator. Therefore, the force can be estimated for the displacement of the first floator. When the parameters are set appropriately, even small force leads to large displacement so that the proposed measurement method is suitable for noncontact measurement of micro force. An apparatus was fabricated for experimental study on the proposed measurement method. Its effectiveness was demonstrated experimentally.
Recently, many magnetic machine elements are developed for industrial use. Magnetic bearing, which enabled rotation machines to support a rotor without contact, is also developed and applied. For such a practical use, miniaturization can be necessary for magnetic bearings. In this paper, we designed 3-pole magnetic bearing with permanent magnet to shorten both bearing length and bearing outside diameter. With this bearing, we experimented and succeeded in perfect levitation and rotation at 7200rpm. Then, we designed 3-pole self-bearing motor in order to further miniaturize bearing length. This self-bearing motor can rotate a levitated rotor in itself without exterior motor unit.
As modern society becomes increasingly more elderly, developing specialized equipment to help assist this growing population in everyday tasks becomes more and more important. Here we have developed a passive gravity balanced arm support system. It was designed to assist the arm motion of elderly people with disabilities. The system consists of the joints and the link and the gas springs. This is a very simple and low cost structure. The arm support system constitutes of the support arm that protects the wrist part and the swing arm that protects the elbow. Rather than being done after recovery from paralysis as a functional disorder, rehabilitation that is undertaken by elderly impaired people using the arm balancer is often undertaken with the goal of self-support of active daily living (ADL) at an activity limit level. We evaluate the arm support system for rehabilitation.
We have been developing an omnidirectional walker (ODW) to provide safe and convenient walking support service to the people suffering from walking disabilities. In walking support, the ODW need to follow the user's directional intention to support the user's movement, making it necessary for the ODW to understand the user's directional intention. Jji this paper, we propose a novel interface to recognize the user's directional intention according to the forearm pressures. The forearm pressures exerted to the ODW by the user with wrists and elbows are measured by 4 force sensors which are embedded in the ODW's armrest. The relationship between directional intention and forearm pressure was extracted as fuzzy rules and an algorithm was proposed for directional intention identification based on distance-type fuzzy reasoning method. We conduct a path tracking experiment using the proposed method. The results show that the algorithm is applicable to the ODW's direction control in walking support.
Walking is a basic function in daily life. Walking rehabilitation is vital for recovery of walking ability from various injuries and illnesses. Training machines for walking rehabilitation in order to realize early recovery are under development in our study. A seated walking training machine is proposed for people who cannot stand up to perform walking rehabilitation. However, during training or other movement using this training machine, a path tracking error occurs due to the center-of-gravity shift caused by the user. In this paper, an adaptive control method is proposed and verified in simulations. First, the kinematics and kinetics of the seated walking training machine are derived. Second, the adaptive control strategy is proposed. Finally, path tracking simulations are carried out using the proposed method. Comparison with proportional-integral-derivative (PID) control in the simulations demonstrates the feasibility and effectiveness of the proposed adaptive control method.
In order to make the power assist suit into practical use, the movable range of arm and the rotational range of the spine must be extended. In this study, the space between the unit and the wearer's shoulder was extended and the spine of the back unit was setback from the shoulder unit, so that the movable range of arm and the rotational range of the spine were extended. By introducing a parallel link mechanism as the elbow joint of the arm unit, and by storing airbags more compact, new compact and powerful arm unit was realized. The number of the joints constructing the shoulder unit was decreased and the configuration of the joints of the arm unit was improved in fitting with the wearers arm.
The aim of this study is the development of the neurosurgical training system with force feedback device based on finite element analysis. Authors implemented several functions necessary for the training system to simulate microscopically-controlled surgery. These were the selection function of the surgical instruments, the zoom function of the operative field and the display function of the reaction force indicator which displays the real time applied force to the cerebellar tissue. Authors implemented the regional detailed model which were three-dimensional surface models of neurovascular systems to the developed training system. In this study, not only visual view of the surgical scene similar to the surgical field but also tactile sensation due to intraoperative interaction between brain tissue and surgical instruments were successfully demonstrated. Our next goal is to implement a three-dimensional finite element model of the neurovascular system in order to perform surgical tasks on the vessels and cranial nerves as microvascular decompression which exist in the root exit zone just after the cerebellar retraction.
This paper deals with maneuvering experiment of a tricycle-type personal mobility vehicle (PMV). The new type PMV has one wheel at a front side and two wheels at a rear side. A feature of the PMV is to steer by difference wheel speed between right and left wheels. At first, the PMV mechanism is explained and then, steering characteristics is explained. Next, an improved steering mechanism which makes easy to maneuver the PMV is suggested and the mechanism is explained. Finally, maneuvering experiment which was chosen as the slalom course was performed for a verification of the proposed mechanism effect.
This paper describes analysis and evaluation of timbre using Fourier analysis. Sample 37 sounds such as natural sounds and instrument sounds are analyzed by short time Fourier transform (STFT) focusing on time variation of sound. Time variation of frequency component on the basis of STFT result is extracted. In order to analyze rough time variation of frequency component, a low pass filter to time variation of frequency component is used. 3D spectrogram of the timbre from time variation of frequency component is plotted in three dimensional spaces. Using time variation of 3D spectrogram, we conduct mapping of timbre. As a result, sounds are classified into five areas in the map.
A high-accuracy measurement technique for plate tension distribution on the process line would potentially lead to improved steel, aluminum and copper plate qualities. We propose an identification method by using natural frequencies and vibration modes, which are related to tension distributions of thin plate. In this paper, a new tension identification method in a thin plate using characteristics of vibration is investigated. We develop a 2-D dynamic model of thin plate, and tension distribution modeling by springs. A 2-D model spring constants are obtained by the least-squares method to minimize the difference between a 2-D model modal parameters and the given values. We apply the proposed identification method to a thin aluminum plate based on FEM analysis results. As a result, it is shown that identified tension distributions well corresponded to the FEM results.