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To identify the parameters of variable flux reluctance machines (VFRMs), the input voltage value is usually obtained from the reference voltage indirectly. However, the reference and actual voltages may be different due to the nonlinearity of the open winding inverter when using zero-sequence current, leading to the inaccuracy of parameter identification. To solve this problem, this paper proposes an equivalent nonlinearity voltage error model of the open winding inverter to compensate for the input voltage of VFRM during the online parameter identification. Since in the proposed method the phase current direction is not required, the calculation time can be reduced. Moreover, in the developed parameter identification model of VFRM the derived equivalent nonlinear voltage error is used to correct the input of the identification model so as to improve the accuracy of parameters. Finally, the experimental results on the prototype VFRM are presented for verification. [ABSTRACT FROM AUTHOR]

In order to improve the power density of the wave power generation system, a magnetic lead screw (MLS) is introduced in this paper as a speed-increasing device in a wave energy converter (WEC), which converts low-speed linear wave motion to high-speed rotational motion. Then, several types of MLSs with different topologies, which were optimized, are described. Finite element analysis (FEA) was used to investigate and evaluate their electromagnetic performances, such as the thrust force, torque, air gap magnetic density, etc. The optimized MLS prototype was manufactured, and the measurements verify the FEA results. Finally, a magnetic lead screw hybrid generator (MLSHG) for application to the WEC is proposed. This MLS significantly improved the power density under different wave conditions. When the moving speed v = 0.15 m/s, the output power of the MLSHG and outer-PM linear tubular generator were 923 W and 87 W, respectively, when the load resistance was 5 Ω. The output power of the MLSHG was more than 10 times compared to that of the outer-PM linear tubular generator in a fair comparison. Here, it is shown that the power density and output power of were MLSHG increased greatly. [ABSTRACT FROM AUTHOR]

A reluctance lead screw (RLS) is proposed in this paper which consists of a rotor and a translator, forming a magnetic device that is able to transfer low-speed linear motion into high-speed rotational motion. Permanent magnets (PMs) are only installed in the rotor, making it more suitable for long-stroke applications. The design aspects are assessed by finite element analysis (FEA) and the performance is evaluated. In addition, the thrust force per magnet volume is presented for evaluating the utilization rate of the PMs. The simulation results show that RLS has an advantage in terms of the PM utilization rate. A new method for realizing spiral magnets has also been developed which can not only reduce the manufacturing difficulties, but also ease the installation work. Finally, based on the simulations and analyses, two RLS prototypes designed for wave energy converters (WECs) are presented to show the potential applications of this novel topology. [ABSTRACT FROM AUTHOR]

A new bi-directional, simple-structured solenoid actuator for active locomotion capsule robots (CRs) is investigated in this paper. This active actuator consists of two permanent magnets (PMs) attached to the two ends of the capsule body and a vibration inner mass formed by a solenoidal coil with an iron core. The proposed CR, designed as a sealed structure without external legs, wheels, or caterpillars, can achieve both forward and backward motions driven by the internal collision force. This new design concept has been successfully confirmed on a capsule prototype. The measured displacements show that its movement can be easily controlled by changing the supplied current amplitude and frequency of the solenoid actuator. To validate the new bi-directional CR prototype, various experimental as well as finite element analysis results are presented in this paper. [ABSTRACT FROM AUTHOR]

To maximize the generated output power under random waves, the control strategy of maximum power point tracking (MPPT) is incorporated in point-absorbing type wave energy converter (WEC) system. However, due to the influence of mutative wave conditions, the curve of the maximum average power appears in multiple peaks, adding complexity to the tracking process. This paper proposes a new MPPT control technique for a wave power generation system, by using the flower pollination algorithm (FPA) instead of the conventional hill-climbing method. Compared with the hill-climbing method, this method has advantages of achieving a smaller peak-to-average ratio and capturing the more average power under the same sea state. The verification has been carried out through the simulations and the experimental results on a lab test bench. [ABSTRACT FROM AUTHOR]