Contact wires used in feeding system for electric railroad are insulated by insulators. However, insulation of an insulator sometimes breaks down by surface dirt of an insulator and contact with a bird. The insulator breakdown derives a ground fault in feeding system. Ground fault will cause a human electric shock and a destruction of low voltage electric equipment. In order to prevent the damage by ground fault, an S-type horn has been applicable as equipped on insulators of negative feeder and protective wire until present. However, a concrete pole breaks down at the time of the ground fault because a spark-over voltage of the S-type horn is higher than a breakdown voltage of a concrete pole. Farther, the S-type horn installed in the steel tube pole does not discharge a case, because the earth resistance of a steel tube pole is very small. We assumed that we could solve these troubles by changing the power frequency spark-over voltage of the S-type horn from 12kV to 3kV. Accordingly, we developed an attachment gap that should be used to change the power frequency spark-over voltage of the S-type horn from 12kV to 3kV. The attachment gap consists of a gas gap arrester and a zinc oxide element. By the dynamic current test and the artificial ground fault test, we confirmed that the attachment gap in the S-type horn could prevent a trouble at the time of the ground fault.
Stand-alone power systems are widely used in islands and remote areas. With the rapid advances in the new energy technology, stand-alone power systems have got a rapid development. However, their overload capability is very poor. In this paper, a novel method to improve the overload performance of the stand-alone power system is proposed by using a flywheel induction motor. The flywheel induction motor is composed of a flywheel disk connected to a squirrel cage induction motor. It is controlled to supply the overload power of the stand-alone power supply by charging and discharging. The proposed system is characterized by the following three points: 1) Simple configuration; The flywheel induction motor is directly connected to the inverter-controlled load without any converters. 2) Simple frequency control; The expected active power flow is realized by a small change of the stand-alone power side inverter's output frequency. 3) Low cost system; A decreased power capacity demand for the stand-alone power supply is realized by adding a low cost flywheel induction motor. Experimental results are provided to verify the proposed system.
In this paper, we propose a high-speed frequency detection method for a single phase utility interactive inverter. Distributed power systems are considered to be a solution to environmental problems. As the use of distributed power systems spreads, the stability and reliability of utility interactive systems become important. In a utility interactive system, it is necessary to synchronize an internal phase of controller to a utility voltage. In the case of a single phase system, it is difficult to detect the instantaneous phase angle of the utility voltage. In this paper, we describe a new high-speed frequency detection method. In this method, a quasi dq transformation is applied by using an FPGA-based hardware controller. The quasi dq transformation is applied to develop PLL control. In this PLL control method, multiple samples can be processed in parallel by adopting an FPGA implementation. The hardware implementations are demonstrated by performing simulations and experiments.
Consensus algorithms enable nodes on a Laplacian graph to dynamically reach an agreement-consensus on certain values, such as the average of initial conditions or local inputs. In this paper we propose a different kind of algorithm, the scaled consensus algorithm based on weighted digraphs. This algorithm enables nodes to track different values which are functions of a common consensus value, depending on the weights of the graph. We employ this algorithm for asymmetric multilateral teleoperation, which requires scaled force reflection and position tracking. More specifically; we generalize the four-channel based multilateral teleoperation architecture for various network configurations, taking the scalings into consideration as well. We also show that the algorithm can be applied to micro-macro teleoperation systems.
In this paper, we present a novel type of feedback compensation for achieving robust vibration suppression of resonant modes in mechatronic systems by the use of allpass filters. In most mechactronic systems, residual vibration must be sufficiently suppressed during precise positioning. In order to achieve the required vibration suppression, the proposed feedback compensation realized using allpass filters is adopted to stabilize the resonant modes without attenuating the gain and to improve the sensitivity characteristics around the resonant modes even when the plant system has high-order vibration modes and time-delay characteristics. The effectiveness of the proposed approach has been verified by carrying out numerical simulations and performing experiments using a prototype.
A new type of circular semiconductor position sensitive detector (PSD) called multi electrode circular PSD (ME-CPSD), which consists of a photosensitive region, a resister line, and 16 electrodes, is presented. The photosensitive region is in the shape of a ring, which is formed by the radial arrangement of long and narrow photodiodes. The outer ends of the photodiodes are connected to the continuous resistor line. Photoexcited carriers generated in the photodiode flow to the resistor line and are extracted by the multi electrode, which divides the resistor into 16 equal parts. The angular position of the light spot is calculated from the output current of the selected electrodes. Compared to conventional circular PSDs, the reliability of angular measurement is better, this is because the ME-CPSD does not have an undetectable region caused by unavoidable discontinuities in the structure of conventional circular PSDs. This device can not only measure the absolute angular position but also carry out a more precise angular measurement by selecting narrower electrode intervals. This device has the capability of realizing a high-precision noncontact angular measurement system with a simple construction.
The conventional demand for robots in industrial fields has increased mainly to mass production; however, the demand nowadays is diverse in meeting high-variation and low-quantity production. To meet the trend, we have proposed a reconfigurable robot that can change its configuration easily. This paper deals with the control algorithm for a reconfigurable robot system. It is necessary that the algorithm should possess flexibility for the changes in robot configurations and tasks. Firstly, the basic structure of a reconfigurable robot consisting of local and central intelligence is described. Secondly, a control algorithm suited for the change in the robot configuration is explained. Then, the authors propose a function-based decentralized control system for reconfigurable robots and refer to the validity of the proposed system for the task change. Finally, the effectiveness of the proposed system is confirmed by several experimental results.
For the commercial production of a claw-teeth motor with three-dimensional powder magnetic cores, the design of motors with high-density and high-strength powder magnetic cores were verified by a test motor. The high strength is to focus on the shaping stress of the press die, and employ the stress values of every part to obtain the design of motor core shapes that can guarantee the desired mold's life that is shown by the relation between stress and mold life according to the material's endurance strength distribution. Furthermore, the high strength, which is obtained by the high-strength process, can make sure that the strength of the flat claw-teeth core that has a complicated shape is at a high level to meet the requirements of factory work. With these considerations, the test motor with the designed claw-teeth cores meets all the design requirements.
Novel frequency doubler ZCS (Zero Current Switching) high frequency inverter applied for high frequency induction heating with non-magnetic material load is developed. The frequency doubler ZCS operation modes are elucidated and experimented by a representative mimic load.
This paper proposes a speed servo system based on a space voltage vector modulation (SVM) inverter with the mixed voltage limitation method considering acceleration torque and voltage saturation for AC servo motor. The servo system realizes both a quick speed response and a small value of total harmonic distortion (THD) in steady state. The experimental results of surface permanent magnet synchronous motor drive confirm that the proposed method achieves the fine speed and current performance.