Non-conventional materials are the emerging demand for machine tool structures, while smooth operations have been hindered due to vibration and thermal deformation of machine tool structures, especially in precision machining. This paper attempts to review and summarize the key developments in the area of non-conventional materials for machine tool structures over the last two decades. Many beneficial properties of the machine tool structural materials are compared with the conventional cast iron. To support the ever-rising working speeds made possible by the development of tools and machining processes, the increasing requirements concerning the surface finish of the machined workpieces and the fabrication cost of the machine tool structures exerted the impetus to find alternatives to cast iron. Based on the results of previous studies, composite materials may be the paragon.

View full abstract

A method to solve a complex nonlinear vibration system is proposed by using both substructure synthesis method (SSM) and perturbation method to save computation cost. The system is divided into some components and those are approximately transformed to modal coordinates. The perturbed equations are synthesized to the overall system and the solution for the overall system is obtained. Sensitivity is defined with varying the nonlinear parameter and corresponding design variable to evaluate the effect of component nonlinearity. This method is applied to the dynamic analysis of nonlinear rotor-casing system as a large mechanical structure system. In order to illustrate the accuracy and computation efficiency of the proposed method, the results of responses are compared with those obtained by the finite element method. The effects of nonlinearity between rotor and bearing to the overall system are also observed by evaluating the sensitivity of nonlinearity.

View full abstract

The fact that material degradation can be calculated by measuring nonlinear acoustic effect has been proposed by previous studies. They reported that the most conventional method to measure nonlinear acoustic effect is to measure the absolute magnitude of the fundamental and 2nd order harmonic frequency component in the propagated ultrasonic wave. For this aim, power spectral analysis technique has been used widely. However, there is a fatal disadvantage in using power spectrum in that the gaussian additive noise superimposed in the wave signal remains in the power spectrum domain. Moreover, the magnitude of the 2nd order harmonic frequency component generated by nonlinear effect is so small that it may be suppressed by the noise remaining in the power spectrum domain. This paper proposes the bispectrum analysis method to overcome this problem. In order to evaluate the performance of our proposed bispectrum method, several sham signals with different SNR (Signal-to-Noise Ratio) were generated in a computer based on the nonlinear wave signal model, and the nonlinear parameter β was estimated in both methods of power spectrum and bispectrum to compare the accuracy. Simulation results showed that the bispectrum method was more stable and could estimate closer nonlinear parameter to the true value than the power spectrum method. Also, in order to verify that our method is applicable to the actual signal, the bispectrum method was applied to the actual experimental signals that were obtained from the transmission test in several SS41 specimens with different degrees of degradation.

View full abstract

In this study we investigate the impulse performance of self-acting semi-spherical air bearings. Parameters affecting the performance of the air bearing are the clearance between the rotor and stator and stator groove depth. Rotation speed is changed from 13000 rpm to 23000 rpm. Rotor impulse displacement, impulse siffness and allowable impulse are selected as axial impulse performance factors. Experimental results show that rotor impulse displacement and impulse stiffness decrease when the speed as well as the groove depth increase and the clearance decreases. Allowable impulse does not change significantly with changes in the clearance, and has a maximum value at a certain groove depth.

View full abstract

The effects of thickness variation, shear deformation and rotary inertia of annular plates are studied by deriving the equations of motion. To solve the differential equation governing the motion of annular plates the Chebyshev collocation method is employed. The dimensionless frequencies are evaluated for different values of taper constant, thickness ratio, radii ratio and power. The results of an experimental investigation are also presented, and the agreement between the experimental values and the predicted values in theory is remarkably good. As a result of this study, it is found that the effects of rotatory inertia and shear deformation reduce the natural frequencies of annular plates for three boundary conditions. This study also showed that the natural frequencies of annular plates with thickness expressed by the nth power function are higher than those by the (n-1)th power function for positive values of taper constant, and vice versa for negative values of taper constant for three boundary conditions.

View full abstract

A method for measuring a pinion type cutter using a coordinate measuring machine is proposed. In this method, the cutting edge profile of the cutter is indirectly measured as the intersecting curve between the flank of tool and the cutting face. Left and right side flanks of the cutter are considered to be the tooth surfaces of two different involute helical gears. The coordinates of many points on the tooth surface and the face are measured using a coordinate measuring machine. The tooth surface and the face are estimated from the measured data by the method of least squares. The cutting edge profile is calculated from the estimated tooth surface and the face. The cutting edge is moved helically and it forms the tooth surface of the actual imaginary gear. A pressure angle of this gear can be calculated. Pressure angle error of the pinion type cutter is that of the imaginary gear.

View full abstract

An electromagnetic-type vibratory feeder of is a typical transportation device used in automatic weighers. As existing feeders are driven by feedforward control, the so-called “firing angle control”, the driver cannot negate sudden disturbances. In this study, we consider applying a feedback control for such a feeder system. First, we give the two details of modelings for the vibration part and for the electromagnetic force part. Next, a feedback control system is constructed for the electromagnetic vibration feeder for which we propose a two-degrees-of-freedom proportional plus integral plus derivative (PID) controller with nonlinear elements. Next, we apply the feedback control to the feeder with a standard trough. Finally, we consider a method compatible with many varieties of troughs by adjusting a nonlinear element. On the basis of the results of some experiments, we confirm that the two-degrees-of-freedom PID control is more effective than the conventional firing angle control.

View full abstract

PID controllers have been widely used in many chemical processes. Because they have only three control parameters and their physical meanings can be easily grasped. However, it is difficult to tune those parameters practically, since the process dynamics often change due to operating conditions or various disturbances. For this problem, a design method of robust PID controllers has been already proposed by the authors in order to guarantee the stability of the control system. However, as that control method is conservative, the desirable setpoint response can not be always obtained. In this paper, a design scheme of a self-tuning pre-filter is proposed to supplement the robust PID controller based on the two-degree-of-freedom control scheme. According to the proposed scheme, the transient property for the setpoint response can be improved keeping the robust stability. Finally, the proposed scheme is experimentally evaluated on an air pressure control system.

View full abstract

In this paper, a stereo vision-based robot servoing control approach is presented for object grasping. Firstly, three-dimensional projective reconstruction with two free-standing CCD cameras and homogeneous transformation are used to specify the goal grasping position and orientation of a robot hand. Secondly, a stereo vision-based servoing problem is formulated, and a stereo vision-based servoing control algorithm which is independent of robotic dynamics is proposed. Using this algorithm, a set of velocity reference inputs can be obtained to control the motions and velocities of the robot hand during the visual servoing. Thirdly, the methods for coping with the time delay of image processing and the CCD camera calibration are put forward. Lastly, the effectiveness of the present approach is verified by carrying out several experiments on object grasping using a 6 degrees of freedom robot. Its stability and robustness as well as flexibility are also confirmed by the experimental results.

View full abstract

To elucidate the skill formation mechanism in a complex force precision task mimicking cello bowing movements, three-dimensional joint orientations and changes in bowing force are measured for 2 novice and 2 expert subjects. A rigid link model of the human upper limb is constructed in order to calculate changes in joint moment, potential energy and structural inductivity of motion during bowing, and the motions are compared kinetically. Results show that the novices generate low-in-potential energy bowing motion, but not suitable for skillful control of the bow. In contrast, the experts can fulfill a task requirement by skillfully coordinating the musculo-skeletal system, but the motion is not easy as that of the novices. It is suggested that the transition from a novice to an expert may be difficult due to the ease in the initially generated motion, which obstructs the search for the optimal skillful motion.

View full abstract

Simulation of a controlled multibody mechanical system, with a nonstiff mechanical subsystem and a stiff control subsystem, usually suffers from long run time. In this paper, a hybrid integration scheme combined with the constraint stabilization method is proposed to overcome this difficulty. The dynamic equations of motion of a constrained multibody mechanical system is a mixed differential-algebraic equation (DAE). The constraint stabilization method proposed by Baumgarte is used to integrate this equation. Correct choice of the α and β coefficients used in the constraint stabilization method is found. The hybrid integration scheme consists of two parts: a nonstiff integration algorithm for the mechanical subsystem and a stiff integration algorithm for the control subsystem. Simulation results show the computational efficiency of the proposed integration scheme.

View full abstract

A simple methodology of designing robust tracking controllers using sliding mode technique is proposed in this paper for a class of nonlinear dynamic systems. This control scheme contains a simple perturbation estimation process embedded in the controller, so that the robustness of system’s stability can be maintained without knowing the upper bound information of perturbation itself and the estimation error of it. The perturbation estimator can be implemented by using a simple high pass filter. The tracking accuracy of control can be adjusted through two stages. The first stage is done by refining the perturbation estimation process. The second stage is done by adjusting the parameter of controller. Chattering phenomenon will never occur under this control scheme. The comparison between the proposed control scheme and the traditional sliding mode control in the frequency domain is given. A numerical example and a practical experiment are demonstrated for showing the applicability of the proposed control scheme.

View full abstract

The filtered-x LMS algorithm which needs a reference signal to provide advanced information about primary disturbances has been commonly used for active noise control in the form of the feedforward control. Therefore, for an effective feedforward control, high correlation between primary disturbance and reference signal is required. However a real system is usually out of this condition. Because there are many cases that have no space for locating the reference sensor in the system while setting the reference sensor, there may be a problem of low correlation between the primary disturbances and the reference signal. This study proposes a hybrid controller, which is an assembled form of feedforward controller and feedback controller to emphasize the strong points of the feedforward controller and overcome its faults. The feedforward controller attenuates the primary disturbances highly correlated with the reference signal, while the feedback controller cancels noises that is unobserved by the reference signal but observed by the error sensor (plant noise). The fact that the intensive periodic components of noise are commonly intended for control makes the narrowband noise canceling of the feedback controller useful beyond its limits in reduction of broadband noise. This study proved the superiority of the hybrid algorithm by making a comparison between feedforward filtered-x LMS algorithm and hybrid filtered-x LMS algorithm in the same excitation condition at the duct system of which the wave motion is a one dimensional plane wave flow. The hybrid filtered-x LMS algorithm is even more effective when the plant noise unobserved by the reference sensor is intense.

View full abstract

This paper presents a sequential approximation method that combines a back-propagation neural network with a search algorithm for nonlinear discrete-variable engineering optimization problems with implicit constraints. This is an iteration process. A back-propagation neural network is trained to simulate the feasible domain formed by the implicit constraints. A search algorithm then searches for the “optimal point” in the feasible domain simulated by the neural network. This new design point is checked against the true constraints to see whether it is feasible, and is added to the training set. Then the neural network is trained again. With more design points in the training set, information about the whole search domain is accumulated to progressively form a better approximation for the feasible domain. This iteration process continues until the approximate model insists the same “optimal” point in consecutive iterations. In each iteration, only one evaluation of the implicit constraints is needed to see whether the current design point is feasible. No precise function value or sensitivity calculation is required. Several engineering design examples are used to demonstrate the practicality of this approach.

View full abstract

In this paper, under assumptions that the linear nominal singular system is regular, impulse-free and asymptotically stable, a sufficient condition is proposed to preserve the assumed properties when the time-varying structured parameter uncertainties are added into the nominal singular system. The corresponding region of preserving the assumed properties, that is obtained by using the proposed sufficient condition, in the parameter space is not necessarily symmetric with respect to the origin of the parameter space. When we consider the standard state-space systems, the proposed sufficient condition becomes a simplified form which coincides with the one reported in the literature.

View full abstract

Several algorithms, namely the Output Error (OE), the Equation Error (EE), the Prediction Error (PE), and the Instrumental Variable (IV), for parameter estimation of Wiener-Hammerstein models, are derived. Monte Carlo simulation results are provided showing the effectiveness, and comparing the performance of these algorithms.

View full abstract

Cardiomechanics deals with the motion and functioning of the heart. How the heart performs as a pump depends largely on the contractile activity of its wall muscle, the myocardium. The mechanical properties of myocardial fibers depend highly on their fibrous structures and activity status. Considered the myocardial fiber orientation, a three-dimensional finite element mechanical model of human left ventricle is constructed based on composite theory and an electrical model of heart, and the computing issues of the active force and after-load are discussed. Finally the mechanical response of the left ventricle subjected to the normal active force is simulated, and the results are compared with solutions obtained from MR tagging images and those from other models. It proves that the given model can be used to study the mechanical function of the left ventricle, and it lays a good foundation for construction of virtual heart with electro-physiological and mechanical properties.

View full abstract

This study applies Lyapunov’s direct method to verify the stability of permanent magnet synchronous motors under singular perturbation control designs. The position and velocity controller designed herein does not require the current information of the motor for feedback purposes (current-sensorless), but the steady-state d-axis current can still be controlled to zero to minimize power dissipation. Combining Lyapunov’s linearization stability analysis, the relation between overall closed-loop stability and control gains of this controller is also revealed. Experimental results demonstrate the effectiveness of this current-sensorless controller. In addition, the performance of this current-sensorless controller is compared with that of a full-state feedback controller. Clearly, the proposed current-sensorless controller can achieve zero positioning error within the resolution of an optical encoder. However, the same result is less easy to achieve using a full-state feedback controller due to the noise effect on the current measurements.

View full abstract

The fuzzy gain scheduling (FGS) control scheme based on TS (Takagi-Sugeno) fuzzy model is an effective approach to control nonlinear systems whose dynamics change with different operating condition. However, when the TS-model-based FGS control scheme is adopted to the stabilization/tracking control problem, a considerable amount of approximation errors between the nonlinear system and fuzzy approximation system apparently affect the control performance. Besides, when the LQR (linear quadratic regulator) method is employed to design local linear controllers, it is necessary to adjust the weighting matrices in performance index of the LQR for getting minimum performance index. Hence, in order to reduce the aforementioned approximation errors and enhance the dynamic performance of the TS-model-based FGS control scheme, a systematic and optimal reasoning method, named as Taguchi-MHGA (Taguchi-modified-hierarchical-genetic-algorithm) approach, is proposed in this paper to search for the optimal fuzzy centers (the linearization points) of the fuzzy regions, the optimal set of membership functions, and the weighting matrices of the LQR method. Furthermore, for ensuring that the closed-loop FGS system at any arbitrary operating point is asymptotically stable, two new sufficient conditions are presented. Finally, computer simulations are performed to demonstrate the effectiveness of the TS-model-based FGS control scheme designed by Taguchi-MHGA method. It is shown that the satisfactory performances have been achieved by such designed optimal TS-model-based FGS control scheme.

View full abstract

CAD systems offer a variety of techniques for designing and rendering models of static 3D objects and even of mechanisms, but relatively few tools exist for interactively specifying arbitrary movements of rigid bodies through space. Such tools are essential, not only for artistic animation, but also, for planning and demonstrating assembly and disassembly procedure of manufactured products. Although, any two positions may be interpolated by an infinity of motions, we chose the screw motion for its relative generality and its computational advantages. The paper covers original algorithms for computing the screw motions from interpolated positions and the envelopes of swept regions generated during the motions. We will also discuss why the formulation of a rigid motion in terms of a sequence of screw motions is more advantageous than other more general motion formulations for computing envelopes of swept regions and for predicting collisions.

View full abstract

Cross-coupled controller has been proposed for improved contouring accuracy of a multi-axis Cartesian system. This paper evaluated the cross-coupled controller in a non-orthogonal multi-axis system. As well known, the contour errors increase when increasing the contour feedrate. The adaptive cross-coupled weighting controller proposed herein maintains low contours at different feedrates. Experiments undertaken on a 3-PRPS stewart platform demonstrate the effectiveness of the proposed adaptive weighting cross-coupled controller.

View full abstract

The authors attempted to apply traction drive to a constant-speed servomechanism for Numerically Controlled (NC) machines. High-precision servomechanisms require high-resolution encoders to detect rotary position, whereas conventional high-resolution encoders cannot rotate at high speed. Therefore, the authors attempted to solve the problem of resolution and maximum rotary speed using a nonsinusoidal-wave quadrature Phase-Locked Loop (PLL). Using this nonsinusoidal-wave quadrature PLL for interpolating the tracking error, a very high-resolution detection of rotary angle at high-speed rotation was achieved even when using inexpensive encoders whose output is nonsinusoidal wave. Traction drive damps the high-frequency torque ripple, but transmits torque ripple of low frequency. Most of the torque ripple of low frequency is due to the eccentricity of rollers. As the rotary speed of rollers becomes high, the torque ripple has a frequency at which it cannot be eliminated either by traction drive or feedback control. Because the mechanism of torque ripple is very complicated, it is difficult to compensate by detecting roller eccentricity. Therefore, the authors used repetitive control to reduce the position error associated with roller rotation, and obtained high-accuracy rotation in the experiments. In this paper, the interpolation method of tracking error using a nonsinusoidal-wave quadrature PLL and the reduction method of tracking error using repetitive control are presented.

View full abstract

We have developed an index for evaluating the force transmission characteristics in N degree-of-freedom (dof) in-parallel wire-driven mechanisms (PWDMs) with N+1 wires. The relationship between input force and output force in an N-dof in-parallel actuated mechanism with only rigid links was used for defining the transmission index for a PWDM. The index was compared with the magnitude of tensile force caused by external forces. And it was used to kinematically synthesize a six-dof spatial PWDM with seven wires. The results of these comparison and kinematic synthesis are shown to support the proposed index.

View full abstract

A wheeled inverted pendulum (WIP), which is unstable, nonholonomic, and has two servo-driven wheels, is fabricated and used to confirm the proposed method for controlling its position and orientation. First, a WIP control system equipped with sensors such as a piezoelectric gyro to detect the tilt angle and two semiconductor photosensing devices to detect the position and orientation, is constructed. By using a distance variable, the system dynamics is decoupled and an optimal regulator with integral action is constructed to reduce the influence of disturbances. Algorithms are proposed to cope with the singularity problem included in the feedback control. Finally, the WIP is effectively controlled starting from various initial positions and orientations to a specified final state.

View full abstract

The characteristics of angle transmission mechanisms exert a great influence on the servo performance in the robotic or mechatronic mechanism. Especially, the backlash of angle transmission mechanism is preferable the small amount. Recently, some new types of gear reducers with non-backlash have been developed for robots. However, the measurement and evaluation method of the backlash of gear trains has not been considered except old methods which can statically measure at only several meshing points of gears. This paper proposes an overall performance testing method of angle transmission mechanisms for the mechatronic systems. This method can measure the angle transmission error both clockwise and counterclockwise. In addition the backlash can be continuously measured in all meshing positions automatically. This system has been applied to the testing process in the production line of gear reducers for robots, and it has been effective for reducing the backlash of the gear trains.

View full abstract

The purpose of this study are to ensure reliability of the power transmission gears, and to predict operating condition of high speed gears especially with regard to temperature distribution in teeth and blanks. The experiments were carried out using power circulating gear testing machine (1100 kW) under ultra high pitch line velocity (∼150 m/s) and temperature distribution in teeth and blanks were measured. By the experiments, the following facts are known. By increasing line velocity, the temperature of teeth increase parabolically and the distribution of bending stress become nonuniform along face width.

View full abstract

Currently in industries, high-speed turbo machineries such as compressors and steam or gas turbines are required to have increased power capacities. Due to this, a large gear size is required which leads to nonuniform temperature distribution. As the result of nonuniform temperature distribution, nonuniform thermal distortion occurs. Change in load distribution due to this thermal distortion is considered to be closely related to scoring and pitting failures. In order to ensure reliability of high-speed gear units, it is necessary to improve the following techniques. (1) The method of predicting the temperature rise of gears and thermal distortion. (2) Tooth correction against thermal distortion. In this paper, a three-dimensional model for calculating the temperature of teeth surfaces and blanks is presented. This model includes the effects of convective cooling by lubricating oil and the change in load distribution due to mechanical deformation. The calculated results of gear teeth temperature and bending stress are in reasonable agreement with the experimental results. It is confirmed that the analytical method is practical and useful.

View full abstract

Surface temperature is considered to be an integrated index that is dependent on not only the load and the dimensions at the contact point but also the sliding velocity, rolling velocity, surface roughness, and lubrication conditions. Therefore, the surface durability of rollers and gears can be evaluated more exactly and simply by the use of surface temperature rather than Hertzian stress. In this research, surface temperatures of rollers under different rolling and sliding conditions are measured using a thermocouple. The effects of load P, mean velocity V_m and sliding velocity V_s on surface temperature are clarified. An experimental formula, which expresses the linear relationship between surface temperature and the P^0.86V_s^1.31V_m^-0.83 value, is used to determine surface temperature. By comparing calculated and measured temperature on the tooth surface of a gear, this formula is confirmed to be applicable for gear tooth surface temperature calculation.

View full abstract

The purpose of this study is to investigate the effect on oil film thickness and traction coefficient by the sudden change of loaded torque on traction drives. The experimental measurements of oil film thickness and traction force were performed using the optical interferometic observation method. And the comparison of experimental results with calculations of the two dimensional non-steady thermal elastohydrodynamic lubrication (TEHL) was performed. We obtained that oil film thickness and traction coefficient decrease though the rotating speed of roller and disc increase, and our discussion lead that the reason of the decrease is the effect of the increase of oil film temperature by shear. The consideration of frictional heating improved the accuracy of calculations about oil film thickness and traction coefficient.

View full abstract

Piston motion which interacts with lubrication characteristics including friction force between the piston and cylinder has been measured by means of eddy current displacement sensors in order to prove the oil whirl phenomena in axial piston pump and motor which had been found theoretically in the previous paper, and been compared with the calculated results. It has been verified that the piston has whirled in the cylinder under certain operating conditions and specifications, similar to the oil whirl phenomena in journal bearings as a self-excited vibration. The phenomena have not occurred for large clearance and narrow bearing width between the piston and the cylinder as the predicated results in the previous paper. The period of the piston whirl has coincided with that of friction force variation.

View full abstract

A new viscosity measuring system was designed and set up employing Rayleigh light scattering and the photon correlation technique in which a high-pressure diamond-anvil cell (DAC) was used. Two kinds of experiments were conducted. One was the measurement of a dilute suspension of polystyrene latex spheres in liquid lubricant and W/O emulsion. Correlation functions induced by the Brownian motion of fine spheres in the lubricant were observed and the viscosities were obtained, the measurement time of which was one-tenth shorter than that of the falling-body method. The other experiment was the measurement of 5P4E (polyphenyl ether) and DOP (dioctylphthalate) without mixing polystyrene spheres. Very weak but observable correlation functions related to structural relaxation were observed and the viscosities of solidified lubricants (about 10⁹ Pa·s), obtained in a very short time by introducing a shift factor for relaxation time, were consistent with those extrapolated from data obtained using the falling-body method.

View full abstract

Nano-machining experiments are necessary in order to quantitatively understand the nano-machining process. A unique nano-machining and measurement FFM system, which has a stiff cantilever for processing, has been developed. The system can machine hard material with the removal bit size of 1-100 nm. The experimental results revealed two key characteristics of nano-machining. Firstly, the shape of the trace varies because of the irregularity of the tip shape and the wear of the cutting edge. Secondly, the depth of the trace processed by using area scanning is about 10 times as large as that by linear scanning. To explain this, a model of the processing was proposed, in which the removal efficiency is raised by feeding the scanning line. Measurements of variations of the horizontal forces and the shape of the cutting chips verified the model.

View full abstract

In the manufacturing process of a mechanical part, many operations with alternatives can be generated. A method for selecting optimum operations from the alternatives, and then sequencing them in order to satisfy some objectives such as the lowest cost or minimum time, is required. This paper proposes a new method for determining operation sequences that minimize the number of tool-changes. First, sub-sets of operations, in each of which operations can be consecutively executed by one tool are determined from the information on tools, and the precedence constraints of operations. Based on the sub-sets of the operations, an integer programming problem is introduced next to determine the operation sequences that minimize the number of tool-changes. Finally, the effectiveness of the method is clarified through a case study.

View full abstract

In this study we consider a resource constrained planning problem of multiple projects with separable activities. This problem provides a plan to process the activities considering a resource availability with time window. We propose a solution algorithm based on the branch and bound method to obtain the optimal solution minimizing the completion time of all projects. We develop three methods for improvement of computational efficiency, that is, to obtain initial solution with minimum slack time rule, to estimate lower bound considering both time and resource constraints and to introduce an equivalence relation for bounding operation. The effectiveness of the proposed methods is demonstrated by numerical examples. Especially as the number of planning projects increases, the average computational time and the number of searched nodes are reduced.

View full abstract

Based on motion and impact analysis, a theoretical model is presented for optimization of grinding performance of a tumbling ball mill. The motion of ball media in the tumbling ball mill is analyzed. The impact parameters of the ball media caused by the falling motion are deduced. The impact and attrition grindabilities are studied. The grinding performance is expressed as the proportion of grindability of all collisions to that of the collisions of ball media in the arc of the shell at a theoretically suitable speed, and is calculated from the point of view of the separation layer. The mathematical model is established and program coding is implemented to optimize grinding performance for the tumbling ball mill. An example of design calculations is given which shows that the grinding performance under the optimized operation parameters is improved significantly.

View full abstract

The aim of this study is to develop an internal magnetic abrasive finishing process for nonferromagnetic complex shaped tubes consisting of straight and bent sections, for which it is considered difficult to achieve a uniform fine finish by conventional technologies. This paper presents the finishing principle and the finishing equipment that provides flexible motion of a finishing unit using a robot. The experiments characterize the differences in the finishing mechanism of the straight section from that of the bent section in view of the difference in geometry. The finishing experiments demonstrate a method to produce nearly uniform internal finishing tubes by a single processing iteration as well as the feasibility of flexible internal finishing in an automated system.

View full abstract

A mathematical formulation for the automated design of parts and assemblies is presented as a numerical algorithm and its accompanying experimental code. A mechanical part is modeled as an assembly of links connected via joints. Constraints are imposed by the designer such that some dimensions are specified as variables while others are allowed to propagate due to a design change. Graph theory is used to model the assembly where the method of cut-joint constraints is used to obtain a spanning tree. Joint constrains between the various links are introduced and their variations are computed. A velocity transformation matrix is introduced and the Jacobian of for each constraint is developed. The Jacobian of the constraint is transformed to joint coordinate space. Finally, because the resulting system of equations has a non-square Jacobian, the Moore-Penrose inverse is used to compute an assembled configuration, hence, redesigning the assembly. The formulation is extended to include various methods for computing an assembled configuration. While the accompanying numerical code is only experimental, the formulation presented herein is believed to form the basis of a new methodology for automated computer-aided design of parts and systems. The significance of this work is characterized by the formulation’s ability to automatically design and redesign parts.

View full abstract

In the design of gear pairs, the designer has to make design trade-off between the geometrical volume and the meshing vibration. It is generally known from experience that the two objectives show conflicting tendency. In this paper, the authors demonstrate the analysis results of the relation between the geometrical volume and the vibration of a gear pair, and propose a design method for cylindrical gear pairs to balance the conflicting objectives by using a goal programming formulation. The design method reduces both the geometrical volume and the meshing vibration of cylindrical gear pairs while satisfying strength and geometric constraints. The validity of the method will be shown through the design results of the four cases of design speeds and the redesign of a helical gear pair currently being used in elevator reduction drive.

View full abstract