A robust controller of wind turbine pitch angle is designed by using the quantitative feedback theory based on the analysis of wind power system model in this paper. The controller design methodology ...is to select the system parameters quantitatively at different wind speed disturbances in order to optimize the response time and the output stability. Theoretical analysis and simulation results demonstrate that the controller can control the speed stability of wind power system with strong robustness to uncertain disturbances of the system parameters when the wind speed fluctuates randomly.
This paper describes the overspeed control of a vertical-axis wind turbine (VAWT) without an electric control system or mechanical brakes. To improve its performance with straight blades, a VAWT with ...a variable-pitch mechanism consisting of a four-bar linkage was designed. This wind turbine exhibits directivity to the wind, which is able to make use of rotational speed control in a VAWT. This wind turbine can achieve passive yaw control by means of tail vanes, which are installed on the eccentric link lever. The yaw angle characteristics of the tail vanes were measured in an open-circuit wind tunnel and in field tests. The yaw angle variations from the numerical analysis are in good agreement with the experimental data from the wind tunnel tests. It was found that overspeed prevention by means of tail vanes is useful in protecting a VAWT from strong winds without using mechanical brakes.
An application of contra-rotating rotors, in which a rear rotor is in tandem with a front one and these rotors rotate in theopposite direction to each other, has been proposed for higher specific ...speed axial flow pump. Then the superiority of efficiencyand cavitation performance of contra-rotating type has been clarified from experimental comparison with the conventionaltype in addition to the difficulty of high performance design of it. In the present study, the possibility of performanceimprovement of contra-rotating axial flow pump by rotational speed controls of front and rear rotors were experimentallyinvestigated. The substantial improvement of pump efficiency was achieved from the partial to the over flow rateby the rotational speed control of rear rotor and was achieved at the lower flow rates by that of front rotor.
An application of contra-rotating rotors has been proposed against a demand for developing higher specific speed axial flow pump. In the present paper, the advantage and disadvantage of using ...contra-rotating rotors are described in comparison with conventional type of rotor-stator, based on theoretical and experimental investigations. The advantages are as follows： （1） The pump is inherently designed as smaller sized and at lower rotational speed. （2） A stable head-characteristic curve for flow rate with negative slope appears. （3） As the rear rotor rotational speed is varied as independent control of front rotor, the wider range of high performance operation is obtained by rear rotor speed control in addition to front rotor speed control. The disadvantages are as follows： （1） The structure of double shaft system becomes complex. （2） The pump performance is inferior at over flow rate as the rear rotor loading is weakened. （3） The blade rows interaction from rear rotor to front rotor more strongly appears. Then the rear rotor design is a key to achieve higher pump performance. Some methods to overcome these disadvantages will be discussed in more details toward wider usage of contra-rotating axial flow pump in various industrial fields.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This paper describes the design of a rotational speed-control system and an angular position-control system for a fluid-driven bi-directional motor. The fluid-driven bi-directional motor has a ...driving principle similar to that of the fluid-driven spindle, which is designed for use in ultra-precision machine tools. The fluid-driven bi-directional motor was designed so that it is driven by low viscosity oil flow power. In this paper, the rotational speed controller for the motor is first discussed. In order to reduce the influence of external load torque on the rotational speed, a conventional disturbance observer is combined with the rotational speed-control system. The angular position-control system, which possesses the rotational speed feedback loop with the disturbance observer in the angular position feedback loop, is then discussed. The designed rotational speed and angular position-control systems are conventional I—P control and proportional control systems, respectively. The performance of the designed rotational speed-control system and the angular position-control system is studied via simulations and experiments. The performance of the designed control system is tested by the step response method as well as by the frequency response method, respectively. The simulation and experimental results show that the rotational speed and the angular position of the motor can be controlled by the rotational speed controller and angular position controller, respectively. In addition, the influence of the external load torque acting on the motor is successfully compensated for by means of the disturbance observer. The experimental result shows that the designed angular position-control system suppresses the steady-state positioning error to less than 0.02°, even if external constant load torque acts on the motor.
Small-sized axial fans are used as air cooler for electric equipments. But there is a strong demand for higher power of fans according to the increase of quantity of heat from electric devices. ...Contra-rotating rotors were proposed for the improvement of the performance of small-sized axial fans and the advantages of it on the point of view of the performance were confirmed. On the other hand, the contra-rotating small-sized axial fan is operated at off design flow rates and the performance deteriorates at off design flow rates. Therefore, rotational speed control of each front and rear rotor is proposed for the improvement of the performance at off design flow rates in this research. In the present paper, the performance of the contra-rotating small-sized axial fan under the rotational speed control is shown and the internal flow conditions of each rotational speed control method are clarified by the numerical analysis results.
Abstract
A water-driven spindle was developed for use in ultra-precision machine tools. Features of this spindle are: (a) it utilizes water flow power to spin the spindle rotor and (b) it utilizes ...the water pressure to support the rotor. Bend flow channels are formed in the cross-sections of the spindle rotor so that the power of the water flow can be converted into driving power for spinning the rotor. This paper proposes a spindle structure similar to that of the water-driven spindle. A feature of the proposed spindle is that it can be driven in either rotational direction by switching the supply ports. By virtue of the feature of the proposed spindle, angular position control will become achievable by designing an appropriate control system. Prior to developing the angular position-controllable spindle, a testing device, named the fluid-driven bi-directional motor, was developed.
This paper deals with the modelling of the motor that will be needed for designing the angular position control system. The derived mathematical model is then evaluated by comparison with the experimental results. It is then verified that the derived mathematical model is capable of representing the static as well as dynamic characteristics of the motor.
Fuel has been one of the most important nonrenewable energy in our lives, but it will reduce from year to year. Wind energy is a clean alternative source compared to fuel consumption which can cause ...smoke pollution. In this research, the objective is to model and simulate a vertical wind turbine model based on several blades to be analysed in terms of velocity, friction, and pressure first before proceeding to develop and incorporate it in the simulation stage. The innovation acts as the foundation of vitality through wind turbines. Compared to horizontal wind turbines, vertical wind turbines have more advantages and benefits. Horizontal wind turbines require taller masts and blades which are more difficult to transport and construct. With higher required velocity, the wind turbine configuration ensures that higher velocity means the rotor rotates the fastest and delivers the best possible energy. The modelling of the vertical wind turbine is categorised into Darrieus and Savonius wind models using SolidWorks. Based on the simulated results, the best wind turbine model is Savonius with 2 blades. This model has the highest velocity, which displays 15.8991 m/s, compared to the 3 blades of the Savonius wind turbine. The 2-bladed Darrieus wind turbine produces a larger velocity, which is 11.3341 m/s, compared to the 3-bladed Darrieus wind turbine, which is 11.2147 m/s. The investigation of the outcomes shows the viability of the developed model which can be utilized to anticipate the presentation of the vertical wind turbine generator framework.
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