This paper investigates effects of a step skew structure in an interior permanent magnet synchronous motor (IPMSM) to improve the output power in the field weakening control area. In this paper, effects of the step skew during the field weakening control are evaluated by three-dimensional finite element analysis (3D-FEA) as a basic investigation. On the other hand, 3D-FEA is required to reveal characteristics of skew structures, but it is time-consuming. Therefore, we constructed a design procedure for reducing development term until a suitable skew structure is obtained although 3D-FEA is performed. Additionally, the final model developed based on the constructed design procedure can achieve a large reduction in both total harmonic distortion (THD) and torque ripple under the field weakening control compared to the typical step skew models. Furthermore, it is found that the final model can suppress the voltage and has a possibility to improve the output power, especially in the field weakening control area.

Magnetic levitation pumps can feed liquid cleanly without mechanical contact by magnetically suspending the rotor shaft integrated with the impeller. However, surfaces of the rotor and the stator need to be protected by resin bulkheads, and then the magnetic gap length is larger than generally electrical machine. Therefore, it is difficult to generate large suspension force for 1-axis active control type magnetic levitation pumps that passively stabilize the rotor in the radial direction with repulsive force of permanent magnets (PMs). This paper proposes a new structure of the repulsion PM which can generate high suspension force even wide gap length. Five structures of the repulsion PM are investigated, and the structure that is optimized for a 1-axis active control type is analyzed with 3-dimentional finite element method (3D-FEM).

This paper proposes a novel voltage control method for cooperative-autonomous switching control. In power systems, the presence of a large number of photovoltaic (PV) systems in a small district leads to deviations in voltage from the upper limit of the specified voltage range. Autonomous active power control leads to inequalities of the PV generation power on the same distribution line. Cooperative active power control improves the inequality, whereas the power is significantly curtailed. In this paper, the proposed method is based on the setting of a reference value to decrease the curtailment power of cooperative active power control, which will decrease the curtailment power. The control method will be changed to autonomous active power control when the curtailment power reaches a predetermined reference value. Several computer simulations have been performed on the distribution line in order to test the performance of cooperative-autonomous switching control. The total energy of the proposed method increases to 13.71 kWh compared to cooperative active power and cooperative reactive power control. The maximum PV energy disparity decreases to 1.38 kWh compared to that of autonomous active power and cooperative reactive power control.

In this paper, we propose a distributed routing method for multiple mobile robots under uncertain motion delays. The feature of the proposed method is that each AGV subsystem creates the routing to minimize the sum of the transportation time and the penalty for collision avoidance constraints taking into account motion delay disturbances for other AGVs. The computational results show that the total transportation time obtained by the proposed method is shorter than that of the conventional method under various type of motion delay disturbances.

We propose a distributed routing system for multi-robot cooperative transportation using parallel multiple processors with asynchronous data exchange. In the proposed method, each robot generates a routing to minimize each objective function comprising of traveling time and the penalty for violating constraints of cooperation with other robots. A near optimal routing is generated by repeating the generation of each routing and data exchange among the robots. Asynchronous data exchange is adopted to reduce the computation time. In order for the solution not to be trapped in a local optimum, the weighting factors violating the constraints are updated with a time-dependent method during parallel computation. The proposed method is applied to motion planning for cooperative transportation of an experimental 4 real robots system. The effectiveness of the proposed method is investigated on various types of experimental conditions.

For the transportation in semiconductor fabricating bay, route planning of multiple AGVs (Automated Guided Vehicles) is expected to minimize the total transportation time without collision and deadlock among AGVs. In this paper, we propose a distributed route planning method for multiple mobile robots using Lagrangian decomposition technique. The proposed method has a characteristic that each mobile robot individually creates a near optimal route through the repetitive data exchange among the AGVs and the local optimization of its route using Dijkstra's algorithm. The proposed method is successively applied to transportation route planning problem in semiconductor fabricating bay. The optimality of the solution generated by the proposed method is evaluated by using the duality gap derived by using Lagrangian relaxation method. A near optimal solution within 5% of duality gap for a large scale transportation system consisting of 143 nodes and 15 AGVs can be obtained only within five seconds of computation time. The proposed method is implemented on 3 AGVs system and the route plan is derived taking the size of AGV into account. It is experimentally shown that the proposed method can be found to be effective for various types of problems despite the fact that each route for AGV is created without considering the entire objective function.