Yasuo Suga

A new approach to fuzzy modeling of nonlinear dynamic systems with noise: relevance vector learning mechanism

This paper presents a new fuzzy inference system for modeling of nonlinear dynamic systems based on input and output data with measurement noise. The proposed fuzzy system has a number of fuzzy rules and parameter values of membership functions which are automatically generated using the extended relevance vector machine (RVM). The RVM has a probabilistic Bayesian learning framework and has good generalization capability. The RVM consists of the sum of product of weight and kernel function which projects input space into high dimensional feature space. The structure of proposed fuzzy system is same as that of the Takagi-Sugeno fuzzy model. However, in the proposed method, the number of fuzzy rules can be reduced under the process of optimizing a marginal likelihood by adjusting parameter values of kernel functions using the gradient ascent method. After a fuzzy system is determined, coefficients in consequent part are found by the least square method. Examples illustrate effectiveness of the proposed new fuzzy inference system

Autonomous mobile robot in pipe for piping operations

An autonomous mobile robot that can move autonomously in a horizontal pipe, a vertical pipe and an elbow joint with bending angle of 90/spl deg/. Furthermore, the robot has a vision sensor and an operating arm in front of the robot body, and accordingly it has functions to execute piping operations, such as inspection of pipe surface, welding of the pipes and so on. The robot is constructed by several units with four wheels connected by universal joints each other. The robot is controlled by a host personal computer and one-chip microcomputers. As the results of operating experiments, the effectiveness of the robot system in autonomous movement in a pipe and an elbow joint and automatic tracking of a welding line was confirmed.

Macrostructure and temperature distribution near the weld interface in friction welding of cast iron

t. Friction welding of FC250 common grade cast iron was carried out to examine the weldability and temperature distribution near the weld interface during welding. The joint strength of both solid and pipe joints was evaluated by tensile tests. The highest tensile strengths in the solid joints and pipe joints were 317 MPa (79% joint efficiency) and 381 MPa (95% joint efficiency), respectively. A fine-grained interfacial layer of FC250 formed near the axial center at the weld interface in the solid joints, whereas there was no fine-grained interfacial layer in the pipe joints. The welding material temperature at the axial center was higher than that at the periphery in the solid joint. There was little difference in the temperature distribution between the solid joints and pipe joints.

Omnidirectional vision-based ego-pose estimation for an autonomous in-pipe mobile robot

This paper describes the omnidirectional vision-based ego-pose estimation method of an in-pipe mobile robot. An in-pipe mobile robot has been developed for inspecting the inner surface of various pipeline configurations, such as the straight pipeline, the elbow and the multiple-branch. Because the proposed in-pipe mobile robot has four individual drive wheels, it has the ability of flexible motions in various pipelines. The ego-pose estimation is indispensable for the autonomous navigation of the proposed in-pipe robot. An omnidirectional camera and four laser modules mounted on the mobile robot are used for ego-pose estimation. An omnidirectional camera is also used for investigating the inner surface of the pipeline. The pose of the in-pipe mobile robot is estimated from the relationship equation between the pose of a robot and the pixel coordinates of four intersection points where light rays that emerge from four laser modules intersect the inside of the pipeline. This relationship equation is derived from the geometry analysis of an omnidirectional camera and four laser modules. In experiments, the performance of the proposed method is evaluated by comparing the result of our algorithm with the measurement value of a specifically designed sensor, which is a kind of a gyroscope.

Friction Welding of AZ31 Magnesium Alloy

The authors have previously shown that the joint strength of friction-welded similar joints produced from ferrous materials, including friction-welded 6061 and 5056 aluminium alloy friction-welded joints, can be evaluated by the deformation heat input in the upset stage and upset loss. 2, 3 To validate this previously proposed evaluation method, i t is necessary to extend its application to other types of materials. It is also necessary to use the method to investigate not only similar joints but dissimilar joints as well. Studies of the latter joints are currently proceeding in parallel with investigations of similar joints. This article describes an investigation of AZ31 magnesium alloy similar joints. Magnesium alloys featuring a low specific gravity and good specific strength are extensively used in the manufacture of aircraft and industrial machinery components to exploit these characteristics. In terms of worldwide resources – ample raw material reserves being available in sea water and the earth’s crust – magnesium alloys are regarded as having viable applications in industry. Magnesium alloys, which also feature a number of other characteristics, such as good heat conduction, high coefficient of linear thermal expansion and ease of oxidation are regarded as difficult to join, although recent advances in joining technology have changed their status to joinable materials. In particular, previous joining difficulties can be easily overcome by friction welding as a solid-phase welding technique to provide easy joining. Friction welding of magnesium alloys was previously regarded as difficult, 7 whereas an AWS publication now describes them as joinable. This technological development may well be due to the effect of differences in welding conditions. Asahina et al have described the performance of friction-welded joints in argon gas to prevent oxidation and combustion, obtaining 90% joint efficiency. This article describes a study of AZ31 magnesium alloy friction-welded joints produced in air under a wide variety of friction welding conditions, investigating the possibility of the deformation heat input in the upset stage and upset loss being used to evaluate joint performance. The tensile strength properties of joints are also examined as joint performance parameters.

Welding of AZ31B Magnesium Alloy by YAG Laser/ TIG Arc Hybrid Welding Process

Recently, magnesium alloy is in the limelight as ECological material with high ability of recycling and lightweight property. Especially, because of outstanding properties as a structural material, the magnesium alloy is in great demand. Under these circumstances, the technical researches and developments of welding process for magnesium alloy welding have great significance to expand industrial application of magnesium. In magnesium alloy welding, arc welding process is generally used. However, heat input by the welding arc affects the magnesium alloy plates, and as the result it makes wide heat affected zone and large distortion of the welded joint. As one of the possible means to improve quality of the welded joint, application of laser welding process may be recommended. However, the low boiling point of magnesium generates some weld defects, such as porosity and solidification cracking. Furthermore, the small laser beam diameter is very sensitive to edge preparation in butt joint. Accordingly, application of laser/ arc hybrid welding process to magnesium alloy welding was proposed. The laser/ arc hybrid welding process is a new process combining the laser beam and the arc as welding heat source. The laser beam and arc influence and assist one another. By application of hybrid welding, synergistic effects are achievable, and disadvantage of the respective processes can be compensated. In this study, welding of AZ31B magnesium alloy thin plates using YAG laser/ TIG arc hybrid welding process was investigated. In order to confirm the properties of the welded joints, tensile testing was performed.

Estimation of temperature distribution in the friction weld of carbon steel by the finite element method

Abstract A new method which applied the finite element method (FEM) was proposed to estimate the precise temperature distribution in the friction weld. With this method, the heat input at the weld interface was estimated by the friction torque measured by the experimental method. The calculation was performed as a non-stationary heat conduction problem of two-dimensional axis symmetry. The calculation method takes heat loss by heat transfer and emission from the side wall of the material into consideration. The heat conduction coefficient and the specific heat of the material are automatically changed in the calculation with increases in temperature of the weld. The system also has functions to change heat input distribution at the friction interface with increases in temperature of the interface. The main results obtained are summarised as follows. A calculation system to estimate the temperature distribution of the friction weld using the FEM, in which the heat input data was calculated from the frictio...

An ultrasonic testing method for detecting delamination of sprayed ceramic coating

The adhesion strength of thermal sprayed coatings is relatively low, and they sometimes tend to delaminate from the substrate during operation. In particular, sprayed ceramic coatings for thermal barriers, such as ZrO2, often delaminate because of thermal shock; therefore, ceramic coatings are often submitted to thermal shock tests. A nondestructive inspection method using ultrasound to detect the delamination of sprayed coating was proposed. In this study, a coating model was made with acrylic plates, and an ultrasonic test was applied to investigate the precision of detecting delamination by the ultrasonic testing method. Results indicate that delamination more than 1mm in diameter can be detected by the ultrasonic testing method. Moreover, the delaminating process of sprayed coatings under thermal shock tests can be detected by this method.

Monitoring of Backside Image of Molten Pool during Aluminum Pipe Welding Using Vision Sensor

This paper proposes an image sensing system for the TIG (Tungsten Inert Gas) welding process of aluminum pipe. In automatic welding process, it is important to recognize the molten pool during the welding process. The use of CCD camera as vision sensor obtains the information of molten pool. The research was conducted for welding of aluminum alloy Al6063S-T5 with controlled welding speed and the AC welding polarity. Firstly, histogram analysis and range of brightness threshold was established. Secondly, by using the differential value of brightness of molten pool, the edge of molten pool can be detected. Finally, to overcome the unsteady detected edge, the ellipse approximation was used to obtain the image parameters, which are width, length and area. From the experiments it is shown that the recognition of molten pool using vision sensor is an effective method.

Evaluation of joint strength of friction welded carbon steel by heat input

The friction welding process is used in various applications because of its many advantages, not least of which is its optimum suitability for joining dissimilar metals. However, in this process the heat source is the self-heat generation caused by friction and the heat generating surface directly becomes the friction weld interface; consequently the friction welding factors subtly influence the friction coefficients and the friction weld interface shows complex features. Thus fundamental issues yet remain, such as the difficulty in establishing appropriate welding conditions depending upon the test specimen materials and variation in the optimum welding conditions with different friction welding machines. Up till now, experimental results had been taken into account in deciding upon the parameters for the welding conditions in studies concerning conventional friction welding; however, it is difficult to adjust the welding conditions to achieve general characteristics solely by means of the above. Recently, Shinoda and others have energetically attempted to influence the joint strength using the heat input model. On the other hand, an attempt has been made by the authors to control the joint strength using the heat input measured during friction welding. Such a study is considered as a means of achieving the tasks described above.