PCB (Printed Circuit Board)s are designed in various sizes and shapes, use variety of processes and materials, and perform a variety of electrical, structural, and some times thermal functions. The major elements of PCBs are the fabric, the resin, and the metal foil (usually copper). The auxiliary elements are the adhesion promoters or treatments that are applied to the fabric and to the copper to assure maximum adhesion of the resin to the fabric and to the copper. Each copper layer has complicated and different pattern to correctly operate for its mission. In that case, the stiffness of PCBs are affected by the copper layers. By reasoning of this complicated copper layer pattern, it is difficult to determine the PCB stiffness. SAR (Solar Array Regulator) for Korea Leo Earth Observation & Science Satellites Program uses two PCBs of different types and sizes. These PCBs are composed of the resin system and copper layers, and not used the fabric. For this study, arm converter board applied to the SAR components is considered. In this study, the methodology of calculation of the PCB stiffness for SAR component is suggested considering the concept of simplified representative volume element and this property will be correlated with the vibration test results.
In the field of mechanical engineering, a large number of systems exhibit time delays caused by, for example, viscoelastic deformation, plastic deformation, cutting, grinding, and wear. These time delays often cause unstable vibrations during the operation of these systems. Such phenomena occur as the chattering of machine tools and as the pattern formation phenomena in contact rotating systems. In the present report, the authors investigate the property of a new stability analysis developed for unstable vibration in contact rotating systems and apply it to a system with a time delay of one half of a rotation period. As a typical example, a prevention method used to change the structural design is formulated for two- and three-DOF systems. The validity of the present method is confirmed by the results of numerical computations.
We have proposed a magnetic levitation control system for a sheet steel and confirmed the realization by a digital control experiment. However, because of the strong nonlineality of the attractive force of the electromagnet and the various uncertainties in the circuit current such as changes in the resistance due to heat generation of the electromagnet, stability of levitation has not been sufficiently ensured. In this study, we aim to develop a noncontact support system for thin steel plates with high robustness using sliding mode control, which is tolerant to factors such as disturbances within control signals and external forces affecting the system. As a result, it was verified that the suppressive effect of the sliding mode control on disturbances is sufficient, and that the application of the continuous model provides the construction of a system with robustness to the disturbance of the external forces.
Robotic systems have been used to automate assembly tasks in manufacturing and in teleoperation. Conventional robotic systems, however, have been ineffective in controlling contact force in multiple contact states of complex assemblythat involves interactions between complex-shaped parts. Unlike robots, humans excel at complex assembly tasks by utilizing their intrinsic impedance, forces and torque sensation, and tactile contact clues. By examining the human behavior in assembling complex parts, this study proposes a novel geometry-independent control method for robotic assembly using adaptive accommodation (or damping) algorithm. Two important conditions for complex assembly, target approachability and bounded contact force, can be met by the proposed control scheme. It generates target approachable motion that leads the object to move closer to a desired target position, while contact force is kept under a predetermined value. Experimental results from complex assembly tests have confirmed the feasibility and applicability of the proposed method.
The main purpose of tunnel ventilation system is to maintain CO pollutant concentration and VI (visibility index) under an adequate level to provide drivers with comfortable and safe driving environment. Moreover, it is necessary to minimize power consumption used to operate ventilation system. To achieve the objectives, the control algorithm used in this research is reinforcement learning (RL) method. RL is a goal-directed learning of a mapping from situations to actions without relying on exemplary supervision or complete models of the environment. The goal of RL is to maximize a reward which is an evaluative feedback from the environment. In the process of constructing the reward of the tunnel ventilation system, two objectives listed above are included, that is, maintaining an adequate level of pollutants and minimizing power consumption. RL algorithm based on actor-critic architecture and gradient-following algorithm is adopted to the tunnel ventilation system. The simulations results performed with real data collected from existing tunnel ventilation system and real experimental verification are provided in this paper. It is confirmed that with the suggested controller, the pollutant level inside the tunnel was well maintained under allowable limit and the performance of energy consumption was improved compared to conventional control scheme.
Rhönrad is a gymnastic equipment that is interesting in terms of dynamics and control. The control method of the Spiral motion by the mass motion in the Rhönrad was clarified. First, the condition for a steady Spiral motion with arbitrary mass position was obtained. Then, by using the linearized equation of motion, the control method to control the attitude of the Rhönrad by the mass motion in it was derived. This control method allows the state of the Rhönrad to be changed from one steady Spiral motion to another steady motion.
This paper presents a backstepping control implementation on magnetic suspension actuators to demonstrate a ball and beam system performance. A magnetic suspension actuator is located on side of the beam for up and down operation to control the ball position. Characteristics on the magnetic suspension actuator are studied from the design concept to construct a ball and beam system. The mathematical model of the system was derived via the Lagrangian function. The magnetic force as a function of position and coil current was measured and modeled by a quadratic function. A control law was developed following backstepping control procedures. To implement this ball and beam system, a linear feedback sensor and control circuit is designed and fabricated using a single chip microprocessor with basic electronic circuits as the control kernel. The ball and beam system is tested on both static and dynamic performance, especially in oscillatory stabilization and sinusoidal tracking.
In this paper, an adaptive sliding controller is developed for controlling a vehicle active suspension system. The functional approximation technique is employed to substitute the unknown non-autonomous functions of the suspension system and release the model-based requirement of sliding mode control algorithm. In order to improve the control performance and reduce the implementation problem, a fuzzy strategy with online learning ability is added to compensate the functional approximation error. The update laws of the functional approximation coefficients and the fuzzy tuning parameters are derived from the Lyapunov theorem to guarantee the system stability. The proposed controller is implemented on a quarter-car hydraulic actuating active suspension system test-rig. The experimental results show that the proposed controller suppresses the oscillation amplitude of the suspension system effectively.
In this study, we propose an object-handing robot system with a multimodal human-machine interface which is composed of speech recognition and image processing units. Using this multimodal human-machine interface, the cooperator can order the object-handing robot system using voice commands and hand gestures. In this robot system, the motion parameters of the robot, which are maximum velocity, velocity profile peak and handing position, can be adjusted by the voice commands or the hand gestures in order to realize the most appropriate motion of the robot. Furthermore, the cooperator can order the handing of objects using voice commands along with hand gestures. In these voice commands, the cooperator can use adverbs. This permits the cooperator to realize efficient adjustments, because the adjustment value of each motion parameters is determined by adverbs. In particular, adjustment values corresponding to adverbs are estimated by fuzzy inference in order to take into consideration the ambiguities of human speech.
In this paper, we propose a non-analytical but effective self-organizing modeling method, where system dynamics of interest are constructed in a polynomial affine formation with high granularity. The conventional data mining technique has the assessment scheme for representativeness of the developed model. However, if the model is applied to extract the desired values without considering the structural peculiarities such as input pattern used for constructing the dynamics, hardware specification used for data acquisition, and so on, it possibly shows substantial margin of modeling error. In order to correspond this type of control paradigm, we define the permissible set of state and input variables in order to characterize the data used for developing the model. The developed model is then applied to the programming based optimal control scheme where the optimal inputs are selected among the permissible set of the input variable, considering all the limitations specified by linear inequalities.
For a maneuvering unmanned autonomous helicopter, it is necessary to design a proper controller for each flight mode. In this paper, the overall helicopter dynamics is derived and a hovering model is linearized and transformed into a state-space form. However, since it is difficult to obtain parameters for stability derivatives in the state-space directly, a linear control model is derived by a time-domain parametric system identification method with real flight data of a model helicopter. Then, two different controllers (a linear feedback controller with the proportional gain and a robust controller) are designed and their performances are compared. The simulation results show outstanding performance. The validated controllers can be utilized to enable autonomous flight of a RUAV (Rotorcraft-based Unmanned Aerial Vehicle).
Mobile robot teleoperation is a method for a human user to interact with a mobile robot over time and distance. Successful teleoperation depends on how well images taken by the mobile robot are visualized to the user. To enhance the efficiency and flexibility of the visualization, an image retrieval system on such a robot’s image database would be very useful. The main difference of the robot’s image database from standard image databases is that various relevant images exist due to variety of viewing conditions. The main contribution of this paper is to propose an efficient retrieval approach, named location-driven approach, utilizing correlation between visual features and real world locations of images. Combining the location-driven approach with the conventional feature-driven approach, our goal can be viewed as finding an optimal classifier between relevant and irrelevant feature-location pairs. An active learning technique based on support vector machine is extended for this aim.
The shape control methods of cable-network structures are investigated. A cable-network structure is a structure that consists of networks of many cables. Novel control methods based on the concept of self-equilibrated stresses are proposed. The self-equilibrated stresses of cable-network structures with nominal or objective shape are calculated by the force density method. Control inputs are determined from these self-equilibrated stresses. This method is applied to reconfigurable antennas consisting of cable networks. The shape control of the antennas is carried out by the proposed or conventional method. The efficiencies of these control methods are compared by numerical simulation. An adequate shape control is achieved without the iteration step by the proposed method. The shape control results obtained by the proposed method are better than those obtained by the conventional method. It is clarified from the comparison that shape control using the proposed method is efficient.
This paper investigates the application of neural networks (NNs) to conventional model reference adaptive control (MRAC) for controlling the real plant of the nonlinear magnetic levitation system. In the conventional MRAC scheme, the controller is designed to realize the plant output convergence to the reference model output based on the assumption that the plant can be linearized. This scheme is effective for controlling a linear plant with unknown parameters in the ideal case. However, it may not be assured to succeed in controlling a nonlinear plant with unknown structures in the real case. We incorporate a neural network in the MRAC to overcome this problem. The control input is given by the sum of the output of the adaptive controller and the output of the NN. The NN is used to compensate for the nonlinearity of the plant that is not taken into consideration in the conventional MRAC. We developed an efficient method for calculating the sensitivity of the plant that is utilized in the NN to perform the backpropagation algorithm very efficiently. The plant of the magnetic levitation system has inherent strong nonlinearities due to the natural properties of the magnetic fields and uncertainties. Therefore, to confirm the effectiveness of our proposed controller, we implemented our proposed controller in real time on an experimental test bed of a magnetic levitation system. Finally, experimental results verified that the proposed control strategy has the advantages of tracking desired output perfectly and reducing the error.
It is difficult for an ultra-sonic motor (USM) to derive a plant model based on the physical analysis. It is well-known that PID control can be constructed even if there is no plant model. In practice, many PID controllers for USM have been proposed. However, there are limitations of control performance on the conventional fixed-gain type PID control because USM causes serious characteristic changes of the plant during operation and contains non-linearity caused by frictions. It is well-known that a model reference adaptive control (MRAC) is very effective to compensate characteristic changes of the plant. However it is not useful for non-linearity of the plant. Then we propose an improved design scheme of MRAC combined with neural networks (NN). The feature of the proposed design scheme is that an improved architecture of the NN is adopted, as a result a simple calculation expression of the Jacobian is derived.
In this paper, a new algorithm for bi-directional evolutionary structural optimization (BESO) is proposed. In the new BESO method, the adding and removing of material is controlled by a single parameter, i.e. the removal ratio of volume (or weight). The convergence of the iteration is determined by a performance index of the structure. It is found that the new BESO algorithm has many advantages over existing ESO and BESO methods in terms of efficiency and robustness. Several 2D and 3D examples of stiffness optimization problems are presented and discussed.
In this study, we conducted a subjective evaluation experiment of a dual manipulator, which exhibits different motion characteristics. There are three motion characteristics: two of which are age-related, and the third is a robot motion characteristic and is newly added to these two motions. The motions are evaluated from motion areas and motion velocities. Subjects are elderly and young people, and the impressions of the motions are compared in two of the different age groups by the Semantic Differential (SD) method. The obtained results indicate that there are age differences in the evaluation of three manipulator motion areas. The elderly people show a higher reliability and a higher familiarity in a robot motion area than in the other two motions. The elderly people seem to be more affected by the manipulator motion than the young people. Therefore, a careful consideration is required when planning the motion of a manipulator for elderly people.
Kinematic calibration of Gough-Stewart platform using a new measurement device is presented in this paper. The device simultaneously measures components of position and orientation using commercially available gadgets. Additional kinematic parameters are defined to model the sources of inaccuracies for the proposed measurement device. Computer simulations reveal that all kinematic parameters of the Gough-Stewart platform and the additional kinematic parameters of the measurement device can be identified with the partial pose measurements from the proposed device. Results also show that identification is robust for the initial errors in the parameters and the noise in measurements. The device is general and can be used for other parallel manipulators. The measurement procedure can easily be automated with the proposed measurement device.
It is well known that the constant velocity of the fluid in a pipe which makes the lowest natural frequency zero is called critical velocity. The pipe becomes unstable when the fluid in a pipe is faster than the critical velocity. If the velocity of the fluid in a pipe varies with time, however, the instability of a pipe will occur even though the mean velocity of the fluid is below the critical velocity. In this paper, a new method for the stability analysis of a pipe conveying fluid which pulsates periodically is presented. The finite element model is formulated to solve the governing equation numerically. The coupled effects of several harmonic components in the velocity of fluid to a pipe is discussed. A new unstable region is shown in this paper which will not appear in the stability analysis of single pulsating frequency. The results of the stability analysis presented in this paper are verified by the time domain anlysis.
This paper presents the development of the scheduling software to adjust the Hexapod Circular Fixator (HCF), which has 6 degrees-of-freedom. HCF is an instrument to correct complex skeletal deformities by using the patient’s X-ray image. HCF scheduler evaluates each lengthening/shortening data of the HCF’s struts to correct the bone deformity. HCF scheduler is implemented in C++ as a window-based application program. Proposed scheduling program is verified through bone model test and showed its usefulness through many cases.
The accurate measurement of strain and stress in a tooth is important for the reliable evaluation of the strength or life of gears. In this research, a strain measurement method which is based on image processing is applied to the analysis of strain near the tooth fillet. The loaded tooth is photographed using a CCD camera and stored as a digital image. The displacement of the point in the tooth flank is tracked by the cross-correlation method, and then, the strain is calculated. The interrogation window size of the correlation method and the overlap amount affect the accuracy and resolution. In the case of measurements at structures with complicated profiles such as fillets, the interrogation window maintains a large size and the overlap amount should be large. The surface condition also affects the accuracy. The white painted surface with a small black particle is suitable for measurement.
In this paper, we investigate the effect of cutting speed on flank wear, crater wear and finished surface roughness during hobbing using an uncoated tool, and TiN- and (Al, Ti)N- coated tools with a minimal quantity lubrication (MQL) system. The experiments were conducted by simulating hobbing by fly tool cutting on a milling machine. The results helped clarify the following points. (1) With the uncoated tool and the TiN-coated tool, the flank wear increases upon increasing in the cutting speed from 47m/min to 86m/min. Conversely, flank wear decreases at the higher speed of 117m/min. It was impossible to cut at 159m/min owing to the failure of the cutting edge. With the (Al, Ti)N-coated tool, the flank wear showed nearly the same small value, irrespective of cutting speed. (2) The cutting speed also has a large effect on crater wear, particularly for the TiN-and (Al, Ti)N-coated tools. The cutting speed of 117m/min is suitable for decreasing crater wear. (3) The finished surface roughness is small for all the tools used in this test for cutting speeds less than 86m/min, after which it becomes large because of the adhesion of deposited metal at cutting speeds more than 117m/min. When using the TiN- and (Al, Ti)N-coated tools, there is a critical cutting groove length, at which the surface roughness decreases rapidly.
A controllable ball joint mechanism with three rotational degrees of freedom is proposed in this paper. The mechanism is composed of three bevel gears, one of which rotates with respect to a fixed frame and the others rotate with respect to individual floating frames. The output is the resultant motion of the differential motions by the motors that rotates the bevel gears at the fixed frame and the floating frames. The mechanism is capable of a large rotation, and the structure is potentially compact. The necessary inverse and forward kinematic analyses as well as the derivation of kinematic singularity are provided according to the kinematical equivalent structure described in this paper.
In this paper, an experimental study of measuring the dynamic meniscus force and the contact force when hemispherical glass sliders bounce on stationary magnetic disks is presented. We prepared hemispherical glass sliders with radii of 1.0 and 2.0mm supported by slender cantilever beams and magnetic disks with 0-, 1-, 2-, and 3-nm-thick lubricant layers with and without ultraviolet (UV) irradiation. In the case of a 1-mm-radius slider with a surface roughness of 1.7nm in Ra, we found that an adhesion force can be clearly observed at the instant of separation under any lubricant condition except the one case of 1-nm-thick lubricant with UV. Typical data of displacement, velocity and acceleration of bouncing motion prove that the adhesion force originates from meniscus force rather than from van der Waals force. We also found that the maximum dynamic adhesion force is close to the static meniscus force. However, in the case of 3-nm-thick lubricant without UV, the dynamic adhesion force increases significantly, probably because of the effect of a squeeze film acting as a viscous fluid. In contrast, the smooth 2-mm-radius slider does not show a clear adhesion force at an impact velocity higher larger than 1.5mm/s. We also found that the maximum contact force versus penetration depth can be estimated well using the Hertz contact theory for the contact between a smooth sphere and a flat.
In this study, we propose a method of determining the coefficient of friction between a tool flank and a sheared surface in shearing. In this method, the vertical force and horizontal force need to be measured after completion of the separation process, after which the coefficient of friction is defined as the ratio of vertical force to horizontal force. In this study, the influences of punch speed, kinematic viscosity of lubricating oil and clearance on the coefficient of friction were investigated. Using the proposed method, a coefficient of friction of about 0.35 was obtained when ordinary lubricating oil was used. The coefficient of friction between the tool face and the material surface was also determined from sliding friction tests. The results of Finite Element Method taking into account the coefficients of friction obtained by the method showed good agreement with experimental results for the piercing of small holes.
Thermal effect on machine tools is a well-recognized problem in an environment of increasing demand for product quality. The performance of a thermal error compensation system typically depends on the accuracy and robustness of the thermal error model. This work presents a novel thermal error model utilizing two mathematic schemes: the grey system theory and the adaptive network-based fuzzy inference system (ANFIS). First, the measured temperature and deformation results are analyzed via the grey system theory to obtain the influence ranking of temperature ascent on thermal drift of spindle. Then, using the highly ranked temperature ascents as inputs for the ANFIS and training these data by the hybrid learning rule, a thermal compensation model is constructed. The grey system theory effectively reduces the number of temperature sensors needed on a machine structure for prediction, and the ANFIS has the advantages of good accuracy and robustness. For testing the performance of proposed ANFIS model, a real-cutting operation test was conducted. Comparison results demonstrate that the modeling schemes of the ANFIS coupled with the grey system theory has good predictive ability.
Recently, some activities for environmental protection have been attempted to reduce environmental burdens in many fields. The manufacturing field also requires such reduction. Hence, a prediction system for environmental burden for machining operation is proposed based on the Life Cycle Assessment (LCA) policy for the future manufacturing system in this research. This system enables the calculation of environmental burden (equivalent CO2 emission) due to the electric consumption of machine tool components, cutting tool status, coolant quantity, lubricant oil quantity and metal chip quantity, and provides accurate information of environmental burden of the machining process by considering some activities related to machine tool operation. In this paper, the development of the prediction system is described. As a case study, two Numerical Control (NC) programs that manufacture a simple shape are evaluated to show the feasibility of the proposed system.
As environmental issues have become serious, the inverse manufacturing concept is discussed to establish a sustainable society. To realize the inverse manufacturing system the prime problem is how to improve the rate of reusing the product modules. Therefore analyzing the life-time of the disassembled modules is very important before reassembling process. In this paper, a cumulative damage model is proposed to discuss the quality of the product that is assembled by reuse modules. It is supposed that modules suffer damages due to shocks and fails when the cumulative damage level exceeds the failure level. Then maintenance cost will be analyzed in order to minimize the expected maintenance cost-rate by optimal maintenance time T and optimal number of damages N in this cumulative damage model. The probable safe life-time of module reuse will be explored. Finally numerical examples are given to confirm the validity of the proposed model.
This paper describes a diamond turning fabrication system for a sinusoidal grid surface. The wavelength and amplitude of the sinusoidal wave in each direction are 100µm and 100nm, respectively. The fabrication system, which is based on a fast-tool-servo (FTS), has the ability to generate the angle grid surface over an area of φ 150mm. This paper focuses on the improvement of the local fabrication accuracy. The areas considered are each approximately 1 × 1mm, and can be imaged by an interference microscope. Specific fabrication errors of the manufacturing process, caused by the round nose geometry of the diamond cutting tool and the data digitization, are successfully identified by Discrete Fourier Transform of the microscope images. Compensation processes are carried out to reduce the errors. As a result, the fabrication errors in local areas of the angle grid surface are reduced by 1/10.
In 5-axis control machining, it is important to reduce the processing time of generating interference-free tool path between a tool and a workpiece. Thus, the paper describes a method to determine interference-free tool posture, based on not every cutting point but every path. The system generates a ruled surface between an offset curve from cutting points and a parametric curve on an interference surface. Rotation of the ruled surface by moving control points on it allows a boundary tool locus, which does not interfere with a workpiece. Tool postures corresponding to a cutting point curve are rapidly determined by appropriately selecting the curve within the area surrounded by two ruled surfaces. The effectiveness of the proposed method is demonstrated by making a cutting experiment of an impeller.
A solid freeform fabrication (SFF) system using selective laser sintering (SLS) is currently recognized as a leading process and SLS extends the applications to machinery and automobiles due to the various materials employed. In order to develop a more elaborate and rapid system for fabricating large objects compared to existing SLS, this study employs a new selective dual-laser sintering (SDLS) process. It contains a 3-axis, dynamic focusing scanner system for scanning large areas instead of the existing fθ lens used in commercial SLS. Therefore, the unique scanning path generation is necessary to eliminate the factors of quality deterioration in case of fabricating larger objects. Also, this paper will address development of an SFF system which employs the dual laser system and the unique scanning device. Experiments were performed to evaluate the effect of a scanning path and fabrication parameters on sintering process and to fabricate the various 3D objects using polymer powder.
The paper describes a robust optimization method to account for the tolerance of design variable and the variation in problem parameter. The proposed post-optimization effort is initiated from the deterministic optimum as a baseline. The successive process to find search directions and step sizes toward the robust optimum is conducted by determining the worst design that has the highest level in constraint violation. During the selection of the worst design, an orthogonal array table in the context of design of experiemtns (DOE) is used to reduce the constraint function evaluations especially for higher dimensionality problem. The analysis of means (ANOM) is adopted in a case where the variation in problem parameter is considered. The measurement criterion to select the worst design is based on the degree of cumulative constraint violation. A mathematical function problem is first conducted to examine the tolerance of design variable. A cantilever beam problem described by four design variables and a bracket problem with seven design variables are subsequently explored by considering both tolerance of design variable and variation in problem parameter.
A new method of recyclability evaluation is proposed. The recyclability of a product is given by summing up recyclability of all units to which the product is manually disassembled. The recyclability of a unit is calculated if all names and amounts of materials of which the unit is composed are known. The recyclability of a disassembled unit consisting of multiple materials is judged on the grounds of removability of impurities, miscibility and marketability of polymer blends. Recyclability of a long-lifetime product can be estimated from recyclability of units, which are modeled as probabilistically distributed degradation of materials. The proposed method is applied to recyclability evaluation for a refrigerator with several scenarios of disassembly levels. The practical disassembly scenarios limit the maximum recyclability rate of the product. Therefore, recyclability rates calculated based on the proposed method are considerably lower than those of the recyclable materials of which the product consisted.