To improve the practicability of investigating devices composed of a body with D_∞ symmetry, aiming at safe and sound operation, the electroelastic field was investigated for a strip with finite thickness subjected to a shear stress distribution that models a mechanical load input to such a device. An analytical technique constructed previously and the Fourier transformation technique with respect to the in-plane coordinates were employed. Then, the three-dimensional distributions of the electroelastic field quantities, such as displacement, electric potential, electric field, strain, stress, and electric displacement, were determined. Through the use of numerical calculations in which it is assumed that the device receives a mechanical load input and produces an electric signal output, the structure of the electroelastic field was investigated. It was found that the precise determination of electric displacement as an electric signal output required three-dimensional analysis considering the electroelastic coupling effect, whereas the stress-strain relation was substantially elastic. Then, it was found that the effect of finite thickness on the field needed to be considered for a relatively thin strip with a thickness comparable to, or less than, the effective width of the surface shear distribution. Moreover, from an application viewpoint, the results suggested that the optimal thickness to maximize an electric signal output exists.

Vibration is one of the significant problems in crane operation. In the rotary crane, the boom is a flexible structure. The vibration in this crane is occurred at the boom and the hoisted load. This research proposed a control strategy for designing the optimal trajectory of the rotary crane with a flexible boom, which can suppress the vibration in the mechanism. In the proposed approach, the simplified dynamics model of the flexible rotary crane was introduced for designing the control trajectory. The boom’s flexibility was modeled with mass-spring systems. The constant-velocity access control method and the point-to-point access control method were used to design the vibrationless trajectory. To estimate the efficiency of the proposed model, the numerical simulation and experiment on the laboratory-scale flexible crane were conducted to measure the motion of the boom tip and hoisted load. The results were compared with those from the vibration control model that did not include the boom’s flexibility. The simulation and experiment results illustrated that the proposed control model with the flexibility of boom was able to suppress the vibration of both boom and hoisted load. Furthermore, the proposed model showed a better vibration suppression than the model that neglected the boom’s flexibility when the crane was driven at high acceleration.

Meshless methods inherently do not require mesh topologies and are practically used for solving partial differential equations in continuum mechanics. However, these methods generally tend to have a higher computational load than conventional mesh-based methods because calculation stencils for spatial discretization become large. In this study, a novel approach for the use of compact stencils in meshless methods is proposed, called the mesh-constrained discrete point (MCD) approach. The MCD approach introduces a Cartesian mesh system to the background of a domain. And the approach rigorously constrains the distribution of discrete points (DPs) in each mesh by solving a dynamic problem with nonlinear constraints. This can avoid the heterogeneity of the DP distribution at the mesh-size level and impose compact stencils with a fixed degree of freedom for derivative evaluations. A fundamental formulation for arrangements of DPs and an application to unsteady Stokes flows are presented in this paper. Numerical tests were performed for the distribution of DPs and flow problems in co-axial and eccentric circular channels. The proposed MCD approach achieved a reasonable distribution of DPs independently of the spatial resolution with a few iterations in pre-processing. Additionally, solutions using the obtained DP distributions in Stokes flow problems were in good agreement with theoretical and reference solutions. The results also confirmed that the numerical accuracies of velocity and pressure achieved the expected convergence order, even when compact stencils were used.

This paper presents a layout optimization method of the spot locations of pencil beam scanning for particle beam cancer therapy. With the pencil beam scanning technique, the particle beam is scanned from spot to spot in the tumor by using scanning magnets. To provide clinically ideal dose distributions and less-invasive treatment to the patients, both the spot locations and the number of particles given to each spot should be optimized. However, the spot layout is fixed with a lattice pattern in many prior studies. We propose the optimization method to derive the non-lattice spot layout to realize an acceptable dose distribution with a reduced number of spots. With the proposed method, a large enough number of spots were located densely at the initial state, and then the spots with the smallest contribution were removed one by one through iterations. The number of particles given to each spot was determined by solving a quadratic problem. Furthermore, we also propose the idea to accelerate the optimization process by simultaneously removing multiple spots. The algorithm was confirmed by numerical examples of both two-dimensional and three-dimensional cases. The dose quality with the optimized spot layout was better than that with the conventional lattice spot patterns, with all tested cases. In the optimized spot layout, the spots were located on the closed lines which were concentric to the target contour. We also confirmed the proposed method of multiple-remotion can accelerate the optimization process without violating the dose quality.

In order to synthesize a human-friendly flexible machine with a simple structure, the flexibly constrained pair (FCP), which is a passive kinematic pair with a flexible kinematic constraint in multiple directions, has been proposed as a novel type of a kinematic pair (Kimura et al, 2021a). However, structures of robots with FCPs must be limited to only closed-loop mechanisms because the FCP is a passive kinematic pair. As a novel kinematic pair to solve this problem, the active flexibly constrained pair (AFCP) is proposed in this paper. This kinematic pair is used as an underactuated active joint mechanism antagonistically driven with several active elastic elements. As active elastic elements for the AFCP, reeled elastic wires with linear elasticity are used to simplify its design and control. In order to design it, a method to optimally arrange reeled elastic wires between the links of the underactuated joint based on a transmission index is proposed. Besides, a method to specify the stiffness required to perform the task in active degrees of freedom (DOF) and the stiffness to balance both flexibility and motion accuracy in passive DOF is proposed. In addition, a method to analyze the kinetostatic motion between the links is proposed to evaluate the motion accuracy of the designed AFCP. As examples, the AFCP with 1-axial main rotation and the AFCP with 1-axial translation along the specified trajectory are designed and analyzed. Finally, they are prototyped, and their performances are examined by experiments.