A structural optimization method of subsystems to realize desired SEA parameters was proposed by the authors in the past studies. This method is based on a combination of SEA and FEM calculation, calculating repeatedly until satisfying the value of objective functions under arbitrary constraints. As a result of applying the proposed method to a simple structure consisting of two flat plates connected in an L shaped configuration, the design variable is taken as the thickness of the FEM element, a subsystem structure with the desired value of the CLF or power flow between subsystems for the one frequency band or multi frequency bands were constructed. However, it is difficult to apply the optimum results to real machine structure because of setting the thickness of the FEM element as the design variable. In this paper, the method is also validated through numerical analyses, using a finite element method, of a flat plate, the plate is grouped into a plural elements, and the each grouped element is set as a design variable, which should take a discrete value, the total mass is taken as a constraint function in order to minimize the vibration power at one frequency band. As a result, in comparison with experimental data, numerical analysis results are qualitatively accurate.
Work in the fields of agriculture, forestry, civil engineering, and disaster relief requires the ability to move on irregular terrain including slopes, and a vehicle-type robot is required to achieve a certain payload. Since the vehicle has a stable movement function on the slope direction and contour line direction, it is possible to generate an arbitrary trajectory on uneven terrain, and the traveling work performance can be improved even in an environment where there are many objects such as obstacles to avoid. The purpose of our study is to establish a vehicle-type robot technology that can move in such an environment. We propose a vehicle-type robot that can move on side slope, which can move along the contour line, just like the switchback of a mountain railway. In order to secure an enough stability margin on the lower side of side slope, a 4-axis link mechanism was applied to the suspension mechanism of each wheel. Adapting on rough surface, couples of diagonal wheels are moved opposite direction with passive mechanism. In this paper, we will discuss the principle of mechanism, the mechanical design, the control, and the results of our experiments.
Rolling bearings are used in various machines. Generally, the rotating speed varies in conformity with operational situation and the fatigue life is calculated using the average rotating speed. Furthermore, there is an intended end-usage in which CW and CCW rotations are repeated at short times. In such end-usage, since the rotating speed becomes zero when the direction of rotation changes, the moment in which the lubricant film is unformed exists. In the case of repeated change of direction of rotation, it can be considered that the wear and rise of vibration can be easy to result in comparison with the case of no direction change of rotation. However, study on the rise of vibration in the use conditions for repeated change of direction of rotation is very few. Therefore, this research deals with the effect of repeated direction change of rotation to rise of vibration by measuring the vibration of small ball bearing in the endurance test. In consequence, it was clarified that the bearing vibration increased with larger rate of acceleration in the moment of direction change of rotation and running track at the raceway surface was distinguished.
The time-averaged airflow around a mileage competition vehicle was analyzed using computational fluid dynamics in order to optimize the body design to reduce aerodynamic drag and achieve lower fuel consumption. The design parameters were the minimum ground clearance h, the radial clearance of the wheels Sr, and the axial clearance of the wheels Sz. The speeds of the inlet airflow and the ground, relative to the vehicle at rest in the computational domain, were both set to 30 km/h based on the running conditions in the mileage competition. The rotation speed of the wheels was also included in the simulation. The drag exhibits a sharp minimum for a particular minimum ground clearance, hmin, where a remarkable pressure recovery and a decay in the vorticity behind the vehicle body are found. Having optimized the Sr value to achieve a lower drag, the Sz value was then adjusted to keep the steering range of the front wheels. Finally, the pressure drag and friction drag per unit span at the spanwise center were calculated. The pressure drag on the rear body is also found to be minimized at hmin. The validity of the friction drag for the vehicle was confirmed by approximate calculations based on theoretical equations for a turbulent boundary layer above a flat plate.
The gas cutting process is one of the main methods used for cutting steel sheets. Gas cutting produces molten steel and it cools down and adheres strongly to the back of the steel material. This adhered matter is called slag and is difficult to remove. In this study, we tried to reduce the viscosity of steel and improve the peelability by applying carbon paste to the steel surface. As a result, it did not contribute to the improvement of the peelability, but the effect of the carbon paste improved fluidity of molten steel and reduced the volume of slag that strongly adhered to the steel sheet. When the carbon concentration of the adhered slag was measured, no carbon remained in the adhered slag, but it was proved that the amount of the adhered slag was reduced by the effect of the carbon paste.
Rapid heating cycle molding (RHCM) that actively controls the mold temperature during plastic injection molding (PIM) is an effective approach for weldline reduction. On the other hand, the higher the mold temperature is, the longer the cycle time is. In addition, the warpage should be taken into account for high dimensional accuracy. For high product quality and high productivity, it is important to minimize the weldline, the warpage and the cycle time simultaneously. In this paper, process parameters in RHCM are numerically optimized for minimizing the weldline, the warpage and the cycle time. Numerical simulation in PIM is generally so intensive that sequential approximate optimization that response surface is repeatedly constructed and optimized is used to identify the trade-off among the objectives. The mold temperature during heating time is maximized for the weldline reduction, whereas the warpage and the cycle time are minimized. Through the numerical result, the trade-off among the weldline, the warpage and the cycle time is clarified.
3D models are designed using 3D CAD software, but 3D direct modeling method using sensor or image processing is still developing research. In this paper, we suggest the 3D direct drawing and modeling system with ARToolKit, and develop the required solid creating method and drawing support tools. The method is creating solid algorithm using projective methods, and the algorithm is converting from intersection of multiple drawing polygonal prisms into the solid model. The support tools are straight segment absorbing ruler and plane absorbing ruler. They make the drawing trajectories (point clouds) absorbed to themselves, because the polygonal surfaces should be drawn from over 2 directions. After that, we investigate the functionality of the solid modeling methods and drawing tools using the Taguchi method (quality engineering), and estimate the optimal condition of the solid modeling methods and drawing tools.