Rotor Speed
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Agriculture ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1038
Author(s):  
Hao Zhang ◽  
Lijun Qi ◽  
Junjie Wan ◽  
Elizabeth M. Musiu ◽  
Jiarui Zhou ◽  
...  

The accurate setting of input parameters in the numerical simulation of downwash airflow from a UAV sprayer is important for acceptable simulation results. To provide real data of simulation parameters (rotor speed and pitch angle) for the numerical simulation of downwash airflow, a wireless simulation parameter measurement system (WSPM-System) was designed and tested in this study. The system consists of hardware and software designed based on Arduino and LabVIEW, respectively. Wireless communication was realized by nRF24L01. The lattice Boltzmann method (LBM) was applied for the numerical simulation of downwash airflow. The results showed that the valid communication distance of the WSPM-System was 100 m, with a packet loss rate of less than 1%. While hovering, the rotor speed dropped by about 30% when the load of the UAV sprayer changed from 16 kg to 4 kg, which resulted in the maximum vertical downward velocity (VVD) on the horizontal detection surface dropping by about 23%. Under forward flight, the rotor speed in the front (n1, n6) and rear (n3, n4) of the UAV sprayer, respectively, showed a negative linear correlation and positive linear correlation with flight speed (R2 > 0.95). Meanwhile, the rotor speed in the middle (n2, n5) was consistent with the rotor speed while hovering under the same load; the pitch angle showed a positive linear correlation with flight speed (R2 > 0.94). A correlation analysis of measured and simulated values of the VVD revealed that the numerical simulation of downwash airflow with the parameters provided by the WSPM-System was reliable (R2 = 0.91). This study confirmed that the input value of the rotor speed in the fluid software needed to be determined according to the application parameters of the UAV sprayer, thus providing a feasible method and system for obtaining real simulation parameters.


2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Amber Israr ◽  
Eman H. Alkhammash ◽  
Myriam Hadjouni

The purpose of this paper is to develop a fixed-wing aircraft that has the abilities of both vertical take-off (VTOL) and a fixed-wing aircraft. To achieve this goal, a prototype of a fixed-wing gyroplane with two propellers is developed and a rotor can maneuver like a drone and also has the ability of vertical take-off and landing similar to a helicopter. This study provides guidance, navigation, and control algorithm for the gyrocopter. Firstly, this study describes the dynamics of the fixed-wing aircraft and its control inputs, i.e., throttle, blade pitch, and thrust vectors. Secondly, the inflow velocity, the forces acting on the rotor blade, and the factors affecting the rotor speed are analyzed. Afterward, the mathematical models of the rotor, dual engines, wings, and vertical and horizontal tails are presented. Later, the flight control strategy using a global processing system (GPS) module is designed. The parameters that are examined are attitude, speed, altitude, turn, and take-off control. Lastly, hardware in the loop (HWIL) based simulations proves the effectiveness and robustness of the navigation guidance and control mechanism. The simulations confirm that the proposed novel mechanism is robust and satisfies mission requirements. The gyrocopter remains stable during the whole flight and maneuvers the designated path efficiently.


Author(s):  
Amira Amamou

Floating ring bearings have been widely used, over the last decades, in rotors of automotive turbochargers because of their improved damping behavior and their good emergency-operating capabilities. They also offer a cost-effective design and have good assembly properties. Nevertheless, rotors with floating ring bearings show vibration effects of nonlinear nature induced by self-excited oscillations originating from the bearing oil films (oil whirl/whip phenomena) and may exhibit various nonlinear vibration effects which may cause damage to the rotor. In order to investigate these dynamic phenomena, this paper has developed a nonlinear model of a perfectly balanced rigid rotor supported by two identical floating ring bearings with consideration of their vibration behavior mainly governed by fluid dynamics. The dimensionless hydrodynamic forces of floating ring bearings have been derived based on the short bearing theory and the half Sommerfeld solution. Using the numerical continuation approach, different bifurcations are detected when a control parameter, the journal speed, is varied. Depending on the system’s physical parameters, the rotor can show stable or unstable limit cycles which themselves may collapse beyond a certain rotor speed to exhibit a fold bifurcation. Bifurcation analysis is performed to investigate the occurring instabilities and nonlinear phenomena. Such results explain the instabilities characteristics of the floating ring bearing in high-speed applications. It has also been found that the selection of the bearing modulus plays an important role in the characterization of the rotor stability threshold speed and bifurcation sequences. An understanding of the system’s nonlinear behavior serves as the basis for new and rational criteria for the design and the safe operation of rotating machines.


2021 ◽  
Vol 11 (19) ◽  
pp. 9324
Author(s):  
Yien Xu ◽  
Hongmei Wang ◽  
Dejian Yang

The increasing level of wind power penetration is seriously threatening the frequency stability of the power system. In this article, we suggest an enhanced frequency response strategy of a doubly fed induction generator (DFIG) based on over-speed de-loaded curve using a novel power function to boost the frequency nadir and settling frequency and reduce the maximum rate of change of frequency (ROCOF) with more efficiency. To achieve this objective, the reference power increases to the torque limit at the de-load operating point and then decreases with the rotor speed toward the maximum power point tracking operating conditions. The simulation results on various wind power penetrations clearly demonstrated that the enhanced frequency response strategy is beneficial to boosting the frequency nadir and settling frequency and reduce the ROCOF.


Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6277
Author(s):  
Chengkun Lv ◽  
Ziao Wang ◽  
Lei Dai ◽  
Hao Liu ◽  
Juntao Chang ◽  
...  

This paper investigates the control-oriented modeling for turbofan engines. The nonlinear equilibrium manifold expansion (EME) model of the multiple input multiple output (MIMO) turbofan engine is established, which can simulate the variation of high-pressure rotor speed, low-pressure rotor speed and pressure ratio of compressor with fuel flow and throat area of the nozzle. Firstly, the definitions and properties of the equilibrium manifold method are presented. Secondly, the steady-state and dynamic two-step identification method of the MIMO EME model is given, and the effects of scheduling variables and input noise on model accuracy are discussed. By selecting specific path, a small amount of dynamic data is used to identify a complete EME model. Thirdly, modeling and simulation at dynamic off-design conditions show that the EME model has model accuracy close to the nonlinear component-level (NCL) model, but the model structure is simpler and the calculation is faster than that. Finally, the linearization results are obtained based on the properties of the EME model, and the stability of the model is proved through the analysis of the eigenvalues, which all have negative real parts. The EME model constructed in this paper can meet the requirements of real-time simulation and control system design.


Author(s):  
Mohamed Abbes ◽  
Souad Chebbi

This paper presents the design procedure of a high-performance sensorless control strategy for the widely used brushless DC (BLDC) motors. Generally, conventional sensorless techniques are based on detecting the zero-crossing instants (ZCP) of the back electromotives forces (back-EMFs) of the three phases. These methods, although widely adopted and marketed on an industrial level, involve many limitations such as filtering delays, difficulty to operate at low speeds and immunity against Electromagnetic Interferences (EMI). In this paper, the main objective is to develop a sensorless control technique integrally independent from the zero-crossing points of the back-EMFs. In the proposed method, a zero-delay adaptive filter was used to extract the fundamental and the quadrature components of the line-to-line voltage of the motor. Then, the Synchronous Reference Frame Phase Locked Loop (SRF-PLL) is used to estimate the electrical angle of phase-to-phase back-EMF along with the rotor speed. The conventional SRF-PLL was implemented using a second-order loop filter (type-3 PLL) in order to improve synchronization performances and for better rejection of voltage spikes induced in motor phases during commutations. The benefits of the control technique are brought to light through simulation results. An experimental prototype was designed to confirm the validity of the proposed method.


2021 ◽  
Vol 9 ◽  
Author(s):  
T.Venkateswara Rao ◽  
◽  
Ananth D.V.N. ◽  

The brushless DC motor (BLDC) is a low cost, reliable and efficient motor for low power applications. In general, the speed, torque and current of the BLDC motor are controlled using a well tuned PI controller in the inner and outer control loops. This controller will be effective in reducing the dynamic speed error, but will produce large current ripples. This reference current when given to the inner control loop and controlled using hall-effect position sensing technique, leads to comparatively large ripples in the torque. Because of large dynamic behavior of dc link voltage when nominal rating capacitor is used, there will be torque ripples and reduction in rotor speed from the reference current value. Hence, to mitigate this torque ripples in BLDC motor a fast acting adjustable dc link voltage like chopper is generally used. The effective dc link voltage control with voltage boosting and controlling action is observed with Y-source converter and is compared with a Z-source converter in this paper. The Y-source converter is designed in such a way that, it will effectively control the speed and also produces lesser current ripples reference. Further, the inverter topology uses a six switch basic configuration but with a new switching strategy. The results are compared with a Z-source converter with the proposed Y-source converter under variable load torque and variable speed cases in MATLAB/ SIMULINK environment. It is found that, the torque ripples are reduced effectively without much change in the reference speed. Also, even at higher rotor speeds, the torque ripples and surges are also lesser.


2021 ◽  
Vol 9 ◽  
Author(s):  
Jian Chen ◽  
Qun Lu ◽  
Libing Chen ◽  
Xiaohui Duan ◽  
Boping Yang ◽  
...  

A nonlinear control without using anemometer is proposed to achieve the maximum power of the wind turbine (WT) based on two-mass model in this paper. To track the maximum power points, the optimal tip speed ratio control strategy requiring to know the optimal rotor speed of the WT (ORS) is employed. To achieve the ORS, a torque observer is designed to estimate the aerodynamic torque, then the ORS can be obtained by the corresponding calculations based on the estimated torque. Due to the high nonlinearities of the WT and time-varying wind speed, a nonlinear control based on feedback linearization control (FLC) is adopted to track the ORS. In the FLC, the WT is linearized firstly, then the rotor speed controller is designed via linear control technique. The effectiveness of the proposed control strategy is verified by simulation studies. The simulation results show that, compared with the traditional PI control based on torque estimation and FLC based on wind speed estimation, the proposed control strategy provides better dynamic performances and higher power conversion efficiency.


Author(s):  
Van-Thang Nguyen ◽  
Cheikh Brahim Abed ◽  
Amélie Danlos ◽  
Florent Ravelet ◽  
Richard Paridaens ◽  
...  

Abstract The present study deals with a low pressure-ratio centrifugal compressor consisting of two counter-rotating rotors called a Counter-Rotating Centrifugal Compressor (CRCC). The design method based on the loss model was presented to determine the geometric parameters of the two counter-rotating rotors. According to this method, the rotor of a selected Single Rotor Centrifugal Compressor (SRCC) has been redesigned into two counter-rotating rotors (upstream and downstream rotors) by choosing the value of meridional Length Ratio (LR). The meridional view, the volute shape, and the operating parameters of SRCC are preserved during the design process. In the first step, the counter-rotating mode at a constant rotor speed of 11k rpm has been carried out. The overall characteristics of CRCC are compared to those of SRCC. In the second step, the map-characteristic of CRCC is established for seven speed ratios. The results show that CRCC increases up to 4,6% for the pressure ratio and 3.5% for the efficiency compared to SRCC at the same tip-speed. In addition, CRCC can operate at a lower tip-speed by about 2k rpm to produce the same characteristics as SRCC, with better efficiency over a wide range of flow rates. However, the surge margin of the CRCC is shifted to higher flow rates. This disadvantage of the CRCC was solved by choosing the adequate pair of the rotational speeds of the two rotors that will be presented in other publication.


Author(s):  
Clemens Zeile ◽  
Thomas Rauwolf ◽  
Alexander Schmeisser ◽  
Jeremi Kaj Mizerski ◽  
Rüdiger C. Braun-Dullaeus ◽  
...  

AbstractA promising treatment for congestive heart failure is the implementation of a left ventricular assist device (LVAD) that works as a mechanical pump. Modern LVADs work with adjustable constant rotor speed and provide therefore continuous blood flow; however, recently undertaken efforts try to mimic pulsatile blood flow by oscillating the pump speed. This work proposes an algorithmic framework to construct and evaluate optimal pump speed policies with respect to generic objectives. We use a model that captures the atrioventricular plane displacement, which is a physiological indicator for heart failure. We employ mathematical optimization to adapt this model to patient specific data and to find optimal pump speed policies with respect to ventricular unloading and aortic valve opening. To this end, we reformulate the cardiovascular dynamics into a switched system and thereby reduce nonlinearities. We consider system switches that stem from varying the constant pump speed and that are state dependent such as valve opening or closing. As a proof of concept study, we personalize the model to a selected patient with respect to ventricular pressure. The model fitting results in a root-mean-square deviation of about 6 mmHg. The optimization that considers aortic valve opening and ventricular unloading results in speed modulation akin to counterpulsation. These in silico findings demonstrate the potential of personalized hemodynamical optimization for the LVAD therapy.


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