Machine tools are called mother machine in the meaning of the machine for producing various machines. Demands for nanometer scale machining accuracy of large and hard-to-cut materials have increased in a wide range of industries. Actual research and development activities on innovative mother machines have been recently performed in industries and academia over the world. In order to meet such extreme industrial requirements, however, it is necessary and indispensable to establish and systematize the machine tool engineering. This paper presents (1) definition of machine tool engineering and general design flow of machine tools, (2) characteristic features and systematization of machine tool engineering, (3) engineering problems to be solved and their classifications, and (4) future evolution trends of machine tool engineering and mother machine.
Manufacturing industries are facing severe competition to achieve products with high quality and low price. It is important to establish a new approach of creating value-added products like objects of craftwork or applied arts, different from traditional way of achieving products with high quality and low price. For the making of soft objects such as rubber, the mold is usually employed. However, fabrication of the mold is not suitable for small lot production. On the other hand, it is difficult to precisely machine soft objects which have completely different characteristics compared to metals generally machined by machine tools. Thus, the study deals with the first trial of creating an artistic product shape of soft objects by employing an aqueous solution of sodium acetate to fix a workpiece and to improve the stiffness. As a result of conducted experiments, it is found that the usage of the aqueous solution of sodium acetate has the potential of realizing “Dexterous Machining” of soft objects.
Decision of the workpiece setting is an important issue in process planning for both 5-axis and multi-tasking machine tools. However, it is difficult to decide the workpiece setting properly and a huge amount of time and effort is required for trial-and-error verifications of NC programs using a virtual machining simulation. Still, in the worst case, the workpiece re-setting is needed to complete machining operation. In order to reduce the trial-and-error verifications, it is important to decide the workpiece setting properly first. In this study, a machinable space derivation method to find the suitable workpiece setting position is proposed. For this purpose, the reachable space of cutting tool tip is calculated based on the relative motion between the cutting tool and the machine table. In the case of 5-axis control machining, the reachable space of cutting tool tip, which changes according to the tool posture, can be visualized. Then, the machinable space can be represented by overlaying the reachable spaces obtained for different tool postures. The machinable space derived is help full to decide the workpiece setting properly at the early stage in the process planning. In the case studies for both 5-axis and multi-tasking machine tools, it is verified that the workpiece setting is decided effectively to complete machining operation by referring the machinable space.
In drilling of Carbon Fiber Reinforced Plastics (CFRP)/titanium alloy stacks, the chip flow should be controlled to finish the hole without any damages on the surface of the CFRP layer. A step drill is applied to drilling of Ti-6Al-4V stacked CFRP for improvement of the surface finish and reduction in the production time. The cutting force and the chip flow are simulated by the energy approach, in which the chip flow angle is determined to minimize the cutting energy. The diameter of the pre-machined hole and the wedge angle of the step edge are discussed with the chip flow angle on the end of the lips, which finish the surface in the hole, and the chip flow velocities. The geometry of the step drill is designed to flow the chip of Ti-6Al-4V upward with the cutting simulation. The designed step drill is verified to finish scratch-free surfaces inside of the holes.
Close-packed structures of fine particles can be self-assembled along specified path by dispensing suspension that contains particles on a substrate and drying it. By using imprinting process, the assembled particles can be transferred to another substrate coated with resin while keeping same edge height of the particles. This study aims to make clear the factors affecting on the assembly width of such patterning process in which spreading and shrinkage of the suspension fluctuates the width and location, including the subsequent replication process. Based on experiments and model analysis, the appropriate conditions were made clear for these processes. Then, the transferred structure was applied to polishing tool as trial where silica particles of 1 μm diameter were assembled along spiral pattern and then transferred on a glass plate using phenolic resin. The tool was pressed against another glass plate while applying rotational motion to carry out machining test. Smooth grooves were obtained on the workpiece though uniform or even engagement was not accomplished.
In order to achieve flexible and autonomous milling operation, a system called Digital Copy Milling (DCM) was developed in our previous studies. Additionally, tool motion control, in which Voxel information of removal volume Voxel model is referred, is performed on the DCM. In this study, a feed speed control function and a tool posture control function are integrated to the DCM by referring feed speed and tool posture parameters stored in Voxel properties of removal volume Voxel model. It is assumed that these parameters change gradually as a diffusion phenomenon to determine Voxel properties automatically using diffusion equation. In order to calculate diffusion equation, Voxel in removal area corresponds to a calculation grid of diffusion equation not just as storage of feed speed and tool posture parameters. In the experimental verification, feed speed and tool posture parameters were determined automatically, and the tool motion was controlled independently of tool path generation successfully to perform milling operation.
Yttria-stabilized tetragonal zirconia polycrystal is promising ceramic for artificial implants despite its difficult-to-cut feature. Thus, a machining method that enhances the process performance is required. We proposed UV laser-assisted machining of Y-TZP. In the process, the laser beam is utilized to ablate the material as well as to heat it. First, the optimal wavelength of the laser was determined by considering the fluence threshold for the ablation. In order to obtain the fluence threshold, we measured the absorption coefficient of Y-TZP against optical beam with various wavelength, and also experimentally determined the energy density required to induce the ablation. From the discussion regarding the optimal wavelength, we decided to adopt the wavelength of 355 nm. A series of the laser assisted machining were performed on Y-TZP to evaluate the machinability. During the experiments, specific cutting force, surface roughness and tool wear were evaluated. The results revealed that the specific cutting force reduced by approx. 60 % at maximum, the surface roughness was also reduced and the tool wear was suppressed in the proposed method.
Many researches on measurement and evaluation method of rotational accuracy of machine tools' spindles has been carried out, since it greatly affects machining accuracy. However, major factor influencing directly on the machining accuracy is behavior of rotational motion of the tool axis and then it can be said that the on-machine measurement and evaluation of the behavior is very important. In this study, therefore, the measurement principle and error factors are considered in design of the device for measuring the axis motion behavior of the rotational tool with various shapes. The results obtained here are as follows. (1) Measurement principle of behavior of the rotational axis motion of the tools with various shapes could be proposed. (2) The proposed principle is applicable to various types of rotary tool such as end mills and drills. (3) It is also applicable to the measurement of tool wear. (4) The allowable range of error factors in designing and making of the device was made clear.
In order to answer the needs for high accuracy and efficiency of machine tools in recent years, thermal deformation has become an important issue. Therefore many studies for suppressing, estimating and compensating the thermal deformation have been carried out. Moreover, the establishment of accurate and efficient measurement and evaluation method of the thermal deformation is also strongly demanded. In the present study, the method to evaluate independently and efficiently the thermal displacement characteristics due to the linear motion of each axis was considered for machining centers. As a result, we have concluded as followed. (1) We could propose All Axis Motion Test (AAMT) method that can evaluate independently and simultaneously the thermal displacement characteristics due to the movement of the each linear axis. (2) AAMT method can be said to be valid, since the experimental results based on this method agrees well with the test result from the single axis motion test. (3) Significantly high efficiency of the measurement and evaluation of thermal displacement of the machining centers is possible by AAMT method
The purpose of this study is to clarify the relationship between the dynamic motion error of feed drive systems and the finished surface generated by simultaneous multi-axis controlled motions. To achieve the purpose, finished surface of cone frustum which is typically used for evaluating machining accuracy of 5-axis controlled machine tool is investigated. In this study, tool motion trajectory and tool orientation by considering dynamic characteristic are simulated by model of feed drive systems of a 5-axis controlled machine tool. The finished surface of cone frustum is predicted based on the simulated results. In order to clarify the validity of simulation result and influence of motion error in each axis on finished surface, actual cutting test is also carried out. In the cutting tests, control parameters of the machine tool were intentionally changed to obtain the motion errors. As the results, it is clarified that the proposed simulation method can predict the machined surface. The influence of motion error in each axis on finished surface is also discussed based on the results of cutting tests and simulations.
This study discuss the dynamic stiffness of guideways of a ultra-precision machine tools. V-V roller guideways have been employed in ultra-precision machine tools, as they can provide very smooth motion and good straightness. Recently, general linear ball guideways are also employed in ultra-precision machine tools. In the design of the machines, it is necessary to obtain the stiffness of these guideways. Therefore an identification method of the guideway stiffness is verified in this paper. In this method, the guideway stiffness is identified from the natural frequency of the moving body. First, the impact test is carried out for an ultra-precision machine tool to obtain the vibration mode of its moving body. Next, a simple vibration model is developed based on the obtained vibration mode to identify the equivalent stiffness of the guideways. Then, the static stiffness of the guideways is measured for the verification of the identified equivalent stiffness. For further verification, natural frequencies of the moving body are calculated by FEM with the identified equivalent stiffness and compared with the measured natural frequencies. The identified equivalent stiffness agreed well with the measured static stiffness. Furthermore, the natural frequencies were calculated almost correctly with the identified equivalent stiffness.
Powder jet deposition (PJD) is a coating process using accelerated particles. In this process, accelerated ceramic particles are impacted on a substrate, and fractured particles partly adhere to it. We have proposed to apply this process to dental treatment. In this study, the effects of the diameter (dg) and the velocity (vg) of a hydroxyapatite particle on PJD process to human enamel were investigated by using a smoothed particle hydrodynamics (SPH) method. Optimized conditions were clarified through the SPH simulations, and PJD experiments were conducted under the obtained conditions. It was found that the surface of the enamel substrate was partly removed when the mean particle diameter dg = 4.65 μm and the mean particle velocity vg = 250 m/s, and coated layers were formed on the human enamel substrates when dg = 4.65 μm and vg = 200 m/s, or dg = 3.18 μm and vg = 200, 250 m/s.
In a control method of a manipulator, it is important that an end effector can softly touch a subject. In order to realize a control for flexibility of a hand, a control with an artificial muscle actuator has been executed. However, the artificial muscle actuators are known to have a problem in controllability because they have nonlinear viscoelastic properties. This study shows simultaneous control of manipulator posture and joint stiffness using the artificial muscle actuators. It is realized by using a simple feedback control system. We also deal with the method to obtain the ellipse that indicates the stiffness characteristic of the end effector. Moreover, the control method is used for leg control of a walking robot. The control performance of the proposed method is verified by simulation.
Concerned with the flow oscillations in a collapsible tube, Starling resistor type oscillations have been widely investigated. This report describes the flow vibrations in the rubber tube which is locally squeezed by a kind of clamp. The parameters of the phenomena in a collapsible tube are material and size of a tube, kind of fluids, flow rate, internal pressure, external pressure, and so on. Although the external pressure is held atmospheric, the tube cross section can assume the typical forms like circular or elliptic or dumbbell, according to the transmural (internal minus external) pressure difference, and the fluid vibration behaviors are explained. The changes of the pressure and the cross section in the tube are measured in the decompression process of the reservoir, and some wave forms with flat phase in the pressure variations are related with those characteristics.
In continuous metal strip processing lines, such as pickling, annealing, and surface treatment lines, lateral instability is a common problem. We have developed the simulation tool based on multibody dynamics (MBD). We divided a strip in the traveling direction, and combined them based on the beam theory. In consideration of the difference between a beam and a thin strip, the torsional rigidity was corrected by FEM analysis. To verify the strip traveling action, the MBD simulation was compared with the experiment in the cases of an inclined roll and a steering roll. The inclined roll controls a lateral strip movement by pushing the strip with an angle, and the steering roll controls a lateral strip movement by inclining itself. The results of the simulation and the experiment were well in agreement in each case. This simulation tool will help us to clarify lateral dynamics, improve performance of lateral control devices.
Finishing processes are performed on a wide variety of products in various quantities by workers on a piece-by-piece basis. Accordingly, the accuracy of the product depends on the worker's skill. To solve this problem, a bilateral control system is applied to a machining support system. The aim of this research is to develop a machining support system via the bilateral control system which can accept various machining theories and to reflect the operation force into the machining geometry. This system has the construction which makes it possible to change the input force to the master and the slave robot based on symmetrical bilateral controller. This construction is useful to change the feature of the system according to the machining condition dynamically. At this time, the operation scale is changed according to the machining condition as well. They are performed based on the new arbitraliy valiable, FID coefficient defined by the authors in this research. The effect of this system is shown by simulations and experimental results.
In this research, we study on posture control of a rotating link system with a torque unit under the condition of viscous friction. The torque unit is a module which consists of an electric motor and a reaction wheel. The friction arising from the presence of a viscous environment can not be ignored in the real system. We consider the influence of the viscous friction on the posture control of a one-link system. Then, we propose a control scheme that utilizes the viscous friction to achieve the posture control of the one-link system and the reaction wheel unloading. As a case study, we deal with a posture control problem of a water floating robot under the condition of viscous friction between the floating robot and the surrounding water. Then the effect of the proposed scheme is evaluated through several experiments.
This paper presents development and evaluation of a mechanical regulator and a robot motion control scheme for a human-robot cooperative task system. There are contact stability problems that a control system becomes unstable when the robot using impedance control comes into contact with a stiff environment in human-robot interactions. The proposed robot motion control system enables stable contact with the stiff environment by the proposed regulator. The proposed regulator is developed to adjust the dynamical interference between object inherent dynamics and robot dynamics, and it provides dynamics transparency to a human operator in human-robot dynamics cooperation. The regulator is composed of mechanical load adjuster to transmit the human force to the robot and motion measuring system that detects relative positional deviation data between the human arm tip and a tip of the robot. To confirm the stability of the proposed control system, stability analysis simulations and verification experiments using an arm robot are performed. A human-robot cooperative experiment shows that effectiveness of the proposed system for increasing the stability and the dynamics transparency in human-robot physical interactions.
Electric-powered personal vehicles have been used as a convenient transportation device. A front-drive-type personal vehicle STAVi, that is easy for elderly but also disabled persons, to climb on from a bed has been focused on. However, front-drive-type personal vehicles are difficult to operate because their over-steering characteristic is strong owing to free casters. If the vehicle can be driven by an easy joy-stick operation, it will be a comfortable function for all users. In previous studies, we proposed a simple modeling error compensator which achieves a desired driving characteristics using a simple reference model, and the effectiveness was evaluated by simulations. In this paper, we propose a control system for STAVi using a modeling error compensator with a non-linear reference model to realize a comfortable under-steering characteristics. At first, the advantage of proposed controller is summarized. The STAVi's over-steering characteristic is modified to be under-steering one by proposed controller. As an experimental result, the additional assistance is necessary for a beginner. The phase-lead compensator for beginners is designed to adjust the maneuverability depending on the skill level. The maneuverability is evaluated by driving experiments on the slope.
A cooperative transporting control method is proposed for two 7-DOF manipulators and one human in this paper. This control method is based on an impedance control law. An object is transported in any direction according to the force added by the human. The force is measured with a 6-DOF force sensor installed at the wrist of the manipulator. When the manipulators cooperate with the human to transport the object, the manipulators should not only support the human but also avoid some obstacles around them. The manipulators avoid the obstacles by utilizing the kinematic redundancy of the manipulator. The virtual force generated by virtual impedance is used in avoiding action. The virtual impedance is set between the manipulators and the obstacles. The effectiveness of the proposed methods is verified through simulations.
This paper introduces the Support Vector Machine (SVM) to classify finger motion patterns from surface EMG (Electromyography). Surface EMG (sEMG) contains several signals from different muscles around the electrode, which make it difficult to estimate actually produced motions. To enhance the classification performance, we investigated which feature of EMG signals is more effective of the following six: raw data, integrated EMG, voltage level difference, power spectrum, FFT peak frequency, or wavelet coefficient. Next, we also considered the selection of SVM's kernel and its parameters. We experimentally demonstrated that the “Voltage level difference” provides 95% or more correct identification rate when the radial basis function (RBF) is utilized as the kernel. Changing the parameter values of the RBF, 98% correct classification rate was obtained in our experiment from three subjects.
In this paper, we propose a new display system consisting of a high-speed vision and high-speed projector, which has remarkable features. First of all, this system generates projection images using simple image processing, because the projection image is controlled without three dimensional shape of an object. Secondary, in this system the projection image is controlled based on errors on the image plane with visual servoing techniques. By using this technique, this system can project images regardless of the pose of the object to be projected. Moreover, there is no need for precise calibration between the projector and camera. The last feature is that it utilizes high-speed vision. This feature makes it possible to control projected image in real time. Having these features, our proposed display system can project images not only on stable fixed screen but also on other objects such as deformable screens and moving screens. To validate the proposed system, we experimented by projecting on a moving screen as well as a bending screen.
A no-backlash drive control technique in which two motors drive a load axis, as one is for a plus direction and another is for a minus direction, has two problems :1) the 1st natural frequency of the drive system may cause a backlash, 2) the drive system has a remarkable power loss. For the former problem, we introduce a notch filter, with its inverse notch filter in some cases, against the 1st natural frequency, which improves the no-backlash drive range, into the simulation. This method is robust, because the 1st natural frequency of the drive system is not related to the load inertia, and related to the motors inertia and the spring stiffness of the drive line. For the latter problem, we employ a torque crossover method, in which a part of torque reference of the drive-side motor gives to the driven-side motor and the resulted torque reference of the driven-side one is reduced. Our experiments showed the total motor current was reduced by half.
The derailment mechanism for when earthquakes occur has been verified in vibration bench tests and simulations in the past. However, in the past full-scale vibration bench tests including ours, the wheels did not rotate. The aims of this study are to verify the derailment mechanism in case that the railway vehicle running at a high speed is vibrated by a large lateral displacement of track during earthquakes, and to reconfirm the past other verifications. In order to realize this aim, we conducted the full-scale vibration tests with an actual series N700 bogie on roller rigs by use of the rolling stock field test simulator. This apparatus enables to simulate running tests with one or half rolling stock on roller rigs which can experience a considerable degree of horizontal displacement. As a result of this vibration test with an actual bogie on roller rigs, we were able to confirm the influence of wheel rotation on the wheel lift motion, the anti-derailing guard rail acting on a rotating wheel, and so on.
Anticipating hazards regarding pedestrians dashing to roadways is potentially a key idea to reduce the number of pedestrian accidents in unsignalized intersections. The objective of this research is to construct a hazard-anticipatory braking assistance system for preventing pedestrian collisions in unsignalized intersections. To realize the objective, this paper mainly focuses on the modeling a reference velocity profile based on actual expert driver behavior data, and the design of an automatic braking control system to realize the reference safe velocity profile. The automatic braking control system uses an AC-servo motor. The AC-servo motor is designed to pull the brake pedal which is connected with a wire and idlers. Finally the feasibility of the proposed braking assistance system is verified by experiments using the experimental vehicle.
This paper deals with the gear rattle of helical gear system. Introducing the mesh stiffness variation and the tooth profile error into the equation of motion of one pair of helical gear system, the effects of the mesh stiffness variation, tooth profile error, and torque variation on the rattle are studied by numerical analysis. As a result, the followings were made clear. (1) Higher-harmonic resonances occur because of the torque variation, however, in the small torque variation, those vibrations are caused by the interaction of the tooth profile error and torque variation. (2) In the region where the meshing frequency is a little lower than the twice of the natural frequency, the large amplitude chaos occurs because of the interaction of the tooth profile error and torque variation. (3) In the higher-harmonic resonance of the helical gear with tooth profile error, gear rattle involves short interval impacts, different from the one without tooth profile error. (4) There is a possibility that the gear rattle is improved by the tooth profile error, but the amplitude of displacement becomes large depending on the tooth profile error.
In this paper, author show a flexible bipedal soft robot which consisted of a SMA(shape memory alloy) and a thin polyethylene plate with nail and stopper. Author proposed to the flexible biped robot which consisted of a SMA(shape memory alloy) and a thin polyethylene plate. This robot can move to front, the back, and a horizontal direction using nail by attaching a nail such as a beetle at the tip of a robot's legs (FFP actuator) of a drive. And the combination it is possible walking by making ON-OFF signal timing of output and input combination. Therefore, in order to realize a flexible biped robot, a mechanism and signal timing need to be harmonized. The ON-OFF switching timing, central to the control strategy to achieve walking behavior, is determined through experiments. The resulting soft walking robot weighs a mere 4.7g (with a height of 67mm, length of 109mm,breadth of 58mm). The experimental results demonstrate the viability and utility of the soft biped walking robot based on FFP actuator and the control strategy to achieve walking behavior.
In the city traffic flow, it is observed that a new additional road causes more terrible traffic jam although the new road was constructed for improving the traffic jam. The aim of this study is to determine the road that causes the traffic jam from the traffic data of the traffic simulator. The problem is formulated as the optimization problem in which the traffic amount is maximized with respect to the configuration of the road network. The present algorithm is applied to the simple numerical example. The simulation result shows that the present algorithm can determine the road link that causes the traffic jam.
In recent years, it has been increasingly necessary that patients, medicines and small precision parts should be carried smoothly and quietly by carts with advanced casters. This paper presents experimental and simulational results of a cart with an active controlled caster to reduce cart's crashes and vibrations. First, the active controlled caster is introduced, which has a mechanical low-crash structure based on the idea of center of percussion. Next, the dynamical model of the cart with the caster is derived to study the caster control of the low crashes and vibrations. This model also includes the road model with a bump and the actuator model for the control. Then we show some experimental results of the cart with the controlled caster, compared to the simulation results. The proposed control is verified to effectively reduce the impulsive crashes and vibrations of the cart. Finally, we in brief discuss the control effect from the view point of the transfer functions and Bode gain diagrams of the cart model.
Injection molded plastics have been used as replacements for metals in optical pickup cases. These plastics are short fiber reinforced composite materials, so the mechanical properties of the pickup case are heterogeneous and anisotropic. We have developed a method for predicting the position deviation of the beam spot on the detector for optical pickups. This method can be used to quantitatively assess to what extent the orientation distribution of short fibers in the pickup case affect the displacement and tilt of optical parts with change in temperature. The sequence for considering the orientation distribution of short fibers in the pickup case is: first divide the pickup case into multiple regions, then define the three-dimensional fiber orientation state as the degree of orientation in each region, and finally set the mechanical properties as a function of the degree of orientation in every region. The degrees of orientation were evaluated by second-order tensor based on cross-sectional observation of the pickup case using a scanning electron microscope. The mechanical properties were obtained by homogenization in three steps. The difference between the calculated result and the measured result for the beam spot deviation at an ambient temperature of 60 °C decreased to one fourth of its previous value by considering the orientation distribution of short fibers in the pickup case.
In spacecraft development, acoustically induced vibration of spacecraft equipment panel is one of the critical design consideration. The prediction of the vibroacoustics is necessary to specify the environment during spacecraft launch. Joint acceptance which is based on the integral calculus with the mode shape has been proposed for the prediction method by the authors. However, the prediction accuracy of the approach is poor for the complex structure in high frequency because of the uncertainty in the mathematical model. This paper is concerned with the approach using simplified joint acceptance employing radiation efficiency and spacecraft panel mass, not based on the integral calculus. The approach is applied to diffuse acoustical excitation of spacecraft panel, and is compared with the results of acoustic excitation test, conventional approach of joint acceptance and SEA. It is shown that the result provide good predictions in high frequency.
We propose a state estimator-based ramp disturbance suppression technique for the predictive functional control (PFC). On the basis of the augmented system including both the plant and disturbance states, we build a predictiontype estimator for the augmented model which estimates the ramp disturbance as well as the plant states. The state estimator enables us to compute the optimal control input sequence in the presence of ramp disturbances. Also, analyzing the structure of the proposed PFC system and controller poles, we prove that the estimator-based PFC system has actually two integral actions. Finally, numerical simulation tests are conducted to check the effectiveness of the proposed method.
Previously, Discrete Wavelet Transform(DWT) is widely used as the image processing method. Some of the DWT, Complex Discrete Wavelet Transform(CDWT) and Complex Wavelet Packet Transform(CWPT) have directional selection that can detect the directional edges from the high frequency components. This property is expected to be used for shape and texture analysis such like a circuit pattern images. However, the principle of directional selection is still unclear. Therefore, fundamental properties such as the detect direction and detection angular range(resolution) are also still unclear. Thus, it is difficult to apply the defect detection that has the directional shape and textures. In this research, we firstly consider the principle of directional selection and we proposed the evaluation method of directional selection based on the consideration result. Proposed evaluation method can make clear the detect direction and resolution quantitatively. Finally we apply the directional selection to defect recognition of semiconductor wafer circuit in combination with Kmeans method. As the result, directional selection of 2D-CDWT and 2D-CWPT achieved highest recognition rate and lowest miss recognition rate compared with previous DWT and FFT.
In this paper, characteristics of subjective force perception are investigated based on the estimation of muscle force activity. Experimental analysis of human force perception characteristics relating to steering operation has revealed that the force perception depends on the angle of the steering wheel and the direction of the load added to the wheel. Our investigation suggests that the muscle activity the subject exerts to conduct a task influences the subjective force perception. Taking this into consideration, we develop a force perception model based on the estimation of the muscle activity by using a 3D musculoskeletal model. The experimental results show that the developed model can generate the angle- and load direction-depending characteristics of the force perception.
This paper deals with active noise control problem for blade passing frequency noise of vacuum motor. In order to make the system inexpensive, we propose a digital synthesis method of a rectangular reference signal with 25% duty ratio whose fundamental period is approximately 1/8 to rotational period by using a counter and interrupt processing on digital hardware (proposed method 1). Furthermore, an anti-aliasing filter is integrated into the previous method in order to reduce aliasing components in sampled reference signal (proposed method 2). These methods are examined by control experiments with inexpensive hardware (dsPIC): First for simplicity of experiment, only the 1st blade passing frequency noise is considered as control target, and an open-loop control system is examined where the controller's coefficients are tuned manually so that error microphone output is minimized. The resultant coefficients are strongly dependent on the vacuum motor's load, which indicates that adaptive control algorithm which uses error microphone information is necessary to consider load change; Second, an adaptive control system is examined based on the standard filtered-x LMS algorithm. The similar performance to the open-loop control is obtained regardless of load change, which indicates that the optimal coefficients are automatically obtained by adaptive control; Finally, the 1st and 2nd blade passing frequency noises are both considered as practical situation. By comparing experimental results for both methods, it is shown that the aliasing components in error signal by proposed method 1 is remarkably attenuated by proposed method 2, which concludes that the proposed method is available to realize inexpensive active noise control system for blade passing frequency noise of vacuum motor.
Aim of this research is to create a mechano-mechanism model of cell's reaction from macro viewpoint. In other words, the purpose is to build a base for mechanical system encapsulating knowledge processing. In this paper, a flow comparison valve using two circular cones and a string has been designed. This valve is used by putting its circular cones in two pipes, in which flow rate are different. It shut off the flow in the pipe, when flow rate is higher than the flow rate in the other pipe. The flow rate calculator in pipes of arbitrary circuit has been programmed and the circuit was putted into the graph as the mathematical model. Due to the calculator and the model, the conditions of current direction in pipes were derived. It has been proposed that how to decide the circuit structure, in which current direction is controllable, by changing the graph according to the condition. The circuit model of the paramecium's ciliary reversal reaction has been determined by the method. This circuit has been made by the pomp, the flow comparison valve, plastic blanched pipes and tubes. The water has been circulated in the pipes of this circuit, and it has been observed that the flow state of the circuit changed by the application of a stimulus. Due to the observation, it has been shown that this circuit model was correct as the model of the paramecium's ciliary reversal reaction.
In this study, the hunting characteristics of a new-type independently rotating wheelset(IRW) with negative tread conicity is verified experimentally. In order to improve curving performance of low-floor light rail vehicles(LRVs), the new-type IRW has been proposed. In previous study conducted by Prof. Suda et al., it has been demonstrated with numerical simulation that unstable hunting motion whose frequency decreases as the running velocity increases occurs in the new-type IRW. In addition, it has been proved that the hunting stability of the new-type IRW can be improved with longitudinal stiffness. In this investigation, experimental equipment with scaled-model roller rig is developed to clarify those characteristics of the new-type IRW. It is demonstrated that the new-type IRW used in experimental vehicle has same hunting characteristics of the simulation model. Furthermore, improvement of hunting stability of the new-type IRW with longitudinal stiffness is proven.
This paper deals with a new magnetic bearing in order to decrease a rotor eccentricity. The proposed bearing system consists of moving frames, suspensions, permanent magnets, electromagnets and Zero Power controller. The system enables to avoid rotor touchdowns. A clearance between a rotor and our proposed bearing may be increased compared to conventional electromagnetic bearings, since permanent magnets are used in new bearings. However, if Zero Power controller is applied to magnetic bearings, a severe problem emerges. When a levitating rotor is subjected to external steady force, to keep equilibrium between external force and magnetic force, a position of levitating rotor may be changed. To overcome this difficulty, this paper proposes a new magnetic bearing structure with moving frames and suspensions. The structure enables to decrease a rotor eccentricity, and a risk of contacting touchdown bearings with fixed frames is reduced. The paper shows the experimental results to verify the system.
We have been researching on an information gathering robot. Before a rescue team enters to save the people who encountered the damage in a disaster and the terrorism spot safely, this robot searches for a safe course for the rescue team, dangerous equipment and the victim. We decided a concept to make a small and light weight to have can potable and enter narrow space, and designed robot to comply with it. The total height of robot that makes it for trial purposes is small with 0.12[m]. Moreover, mass is light with 0.6[kg]. We let you run this robot which you produced experimentally on a road surface of various situation including gravel and step and RSF. We have grasped maneuver performance on this robot by comparing with the theoretical value computed beforehand. Devised to improve the traveling performance and a coupling of multiple robots was also confirmed that performance is better to go the step by.
This paper presents a sliding mode controller of semi-active suspension systems. The sliding mode controller is designed by the describing function method so that the switching function is enforced into a desired limit cycle instead of a perfect sliding mode. Although the proposed sliding mode controller cannot generate the limit cycle as desired because of the passive constraint of controllable dampers, restricting the switching function in the vicinity of the origin can suppress the deterioration due to the passive constraint, such as increase of jerk of the sprung mass system. Finally, simulation results show the effectiveness of the proposed controller.
The lightweight racket with handle-light configuration and large head size is recent tendency of high-tech tennis rackets, increasing power or post-impact ball velocity with an increasing racket swing speed. This paper investigated the performance of lightweight balanced racket with super-large head size with 120 square inches in terms of feel or comfort. It predicted the effect of the mass and mass distribution of super-large head sized rackets on the impact shock vibrations of the racket handle and the player's wrist joint when a player hits a flat forehand drive. The prediction is based on the identification of the racket characteristics, the damping of the racket-arm system, equivalent mass of the player's arm system and the approximate nonlinear impact analysis in tennis. A lightweight balanced racket (mass: 292 g, the center of gravity LG: 363 mm from the butt end) and a conventional weight and weight balanced racket (349 g, LG: 323 mm) are selected as representatives. These two super-large head sized rackets made of carbon graphite have the same head size and same geometry. The result showed that the shock vibration of the lightweight balanced racket with super-large sized head is much larger than that of the conventional weight balanced type racket. It also showed that the sweet area of the former in terms of the shock vibration shifts from the center to the topside on the racket face compared to the latter. This is because the location of the grip on the racket handle is further from the location of the node on the handle of the first mode of lightweight balanced racket than that of the conventional weight balanced racket.
Cooperative control algorithms for a finger-arm robot composed of a 3-DOF finger and 6-DOF arm have previously been proposed based on the movement of the human hand-arm system. In these algorithms, a finger-arm robot completes a constrained task by integrating admittance and impedance control with manipulability control of the finger. The finger manipulability is controlled both by an approximate global search, i.e., the top search method, and by a local optimization method. In this paper, these methods are developed further by relating them to dynamic movement. We also discuss the feasibility of virtual dynamics and clarify the dynamic characteristics in terms of the control algorithms. The dynamic characteristics are verified with virtual external force as shown in experiments with a redundant multi-finger-arm robot. Experimental results are presented for a multi-finger-arm robot to simultaneously achieve manipulability control and admittance control in a three-dimensional space. The developed methods responded to more dynamic movement.
In the previous report, we presented a self-powered digital system for vibration control. The self-powered system automatically measures the displacement of vibrating structure and digitally calculates the vibration state. Then it regulates its electric switches and achieves effective vibration suppression. Especially, it harvests electrical energy from structural vibration and utilizes the energy for activating itself. Some experiments with the self-powered digital system were reported in the previous report, which showed good results only in the steady-state condition. In this note, we demonstrate how the system works in the transient-state. These experiments clearly show the processor's transition between the wake-up and the sleep modes according to the vibration amplitude.
This paper describes newly developed suede pads for final polishing of glass that employ epoxy resin to improve the stagnation properties of the abrasives. From contact and sliding angle measurements on resin films, it was found that epoxy resin exhibited higher hydrophilicity than urethane or fluorine resin. In an attempt to improve the polishing performance of commercially-available polyurethane suede pads, various types of resin films were deposited on them, and glass polishing tests were carried out. It was found that an epoxy-coated pad exhibited a two times higher removal rate than an untreated pad, whereas the fluorine resin coating actually reduced the removal rate. Suede pads containing epoxy resin were then fabricated using a wet solidification method. A Fourier transform infrared analysis indicated that the resin remained in the fabricated pads. The resin containing pads exhibited significantly higher performance than conventional polyurethane suede pads. The removal rate when polishing glass was found to increase with epoxy resin content. The surface waviness was also improved using the new pads. High polishing performance could be maintained even after a 3 h polishing test.
Cloud services have provided application interfaces consisting of software programs and hardware resources through the net. The cloud services have created a trend in the industry - making ownership of software and hardware products for their system unnecessary. Accordingly, web services are developed through combining these interfaces leased from the cloud. However, this trend has also highlighted the gaps between design and operation. The permeation of virtualization technologies for servers and storages require developers to focus on resources as they become design choices. Likewise, operators are required to have concern over application components as the cloud service interfaces enable rapid prototyping and staging of web applications. However, both parties are not able to combine the application logic and resources as each is supervised by the other party. To address this issue, this paper focuses on resource modeling. This approach enables separation and integration of both application logic and resources in design, test, and operation phases, and it is carried out as follows. The first method enables reasonable requirement definitions while run-time resources in the cloud are referred and adapted to fit. The second one streamlines architectural design of both software and virtualized resources comprehensively, in accordance with Axiomatic Design, DSM and Design-for-X. The third enables independent test of functionality of applications and non-functional requirements, e.g. security and performance, by separating logic and resources of the target web service. The last method enables run-time resource management by determining non-functional requirements. These methods are verified through a prototype, making management of the service lifecycle easier.
Distinctive mechanical behavior of bolted joints is caused by the helical shape of thread geometry. Mathematical expression of the helical thread geometry of a single-thread screw has successfully been derived in the previous study. Using the derived equations, finite element models were constructed by taking account of the effect of the helix, and it is clarified how the stress distributes along the thread root and where the maximum stress occurs. Meanwhile, there are various thread forms other than a single-thread triangular screw. In this study, mathematical expressions of the helical thread geometry and the cross sectional area of multiple-thread screws, trapezoidal thread and pipe thread are derived in the same manner as in the case of a single-thread screw. Using the equations thus obtained, finite element models with multiple-thread screws are constructed, and its tightening process by torque method is analyzed. Numerical results show that the stress distribution patterns are basically identical along all helixes for each multiple-thread screw. It is also found that the maximum Mises stress occurs at the first bolt thread root and it increases as the lead of multiple-thread screw increases.
A linear-motor-driven table sustained by constant-flow hydrostatic water bearings has been developed. The table, which is supported by single-sided recess type bearings, is preloaded by its weight and the attractive force arising from permanent magnets of the linear-motor. Due to periodic change of the magnet polarity, the amplitude of the attractive force changes according to the table position. As a result, pitching motion of the table is generated during the table-feed motion. This paper investigates the influence of air bubble contained in hydraulic fluid on static stiffness and dynamic behavior of the table. Damping ratio and natural frequency of the table become smaller under larger volume of containing air. When natural frequency of the table pitching motion coincides with the frequency of the attractive-force change, the largest pitching motion is observed.
CFRP (Carbon Fiber Reinforced Plastics), which is increasingly applied to airplanes, automobiles, production equipment for electronic device, and so on, is machined after molding process. Grinding is often used for edge finishing of CFRP parts. This paper deals with the influence of grinding atmosphere on grinding characteristics of CFRP by the experimental investigation of ground surface characteristics, surface finish, grinding force, grinding temperature, etc. in surface grinding of unidirectional CFRP using a vitrified bond diamond wheel with the water soluble coolant and the liquid nitrogen in addition to dry grinding. The grinding temperature has been measured by a developed thermocouple system using carbon fibers being made up CFRP and a constantan wire setting between CFRP specimens. The grinding temperature at wheel contact area on CFRP is higher than the glass-transition temperature of CFRP at larger setting wheel depth of cut. The wet grinding prevents in worsening ground surface of CFRP and increasing grinding force that occur in dry grinding of CFRP. The liquid nitrogen makes some effect on prevention in wheel loading and delamination of carbon fibers in dry grinding of CFRP, however the grinding force supplying liquid nitrogen becomes larger than that in dry grinding because of an increase in hardness of CFRP by freeze up. The bending strength of ground CFRP, which suggests the scale of affected layer, is improved by supplying the water soluble coolant and the liquid nitrogen in grinding process.
For the purpose of developing a new simple estimation method of metal cutting forces, firstly, orthogonal cutting data are examined from the point of view that material constants other than shear stress on the shear plane, which is characteristic of the material used and is not affected by cutting conditions, may exist. As a result, the authors find that the principal cutting force is approximately proportional to the chip thickness in a relatively wide range of cutting conditions. Thus, the principal cutting force is proportional to the unit chip sectional area, and the proportional constant is named “ chip constant ” for convenience in this paper. Then, the concept of the chip constant is introduced into the cutting mechanism of cylindrical turning, and three cutting force components are analyzed. The estimated values of the three components are compared with measured ones in regard to the change of side cutting edge angle. Since only two constants of the material used, i.e., the chip constant and shear stress assumed from the chip hardness, and measurement of the chip thickness are required, this estimation method of cutting forces is simple and handy.