Vibration Reduction in Rolling Piston-Type Compressors through Motor Torque Control. Basic Study on Theoretical Analysis and Computer Simulation.

In this paper an in-flight tracking control system minimizing vibratory loads at the frequencies 1/rev and 2/rev using steady deflections of active trailing-edge flaps is examined. The control system is based on the relaxed HHC algorithm and uses the Moore-Penrose pseudoinverse of a symmetrized transfer matrix to calculate the control commands for vibration reduction. The focus of the current investigation is on symmetrization effects of the transfer matrices used for controller design on the performance of the control system. In a theoretical pre-flight analysis bounds for the stationary solution of the state-space representation of the closed loop control system are derived on the basis of the Kalman decomposition controller in the frequency domain is calculated. This analysis shows the vibration reduction by the controller using the symmetrized transfer matrices to be close to the optimally achievable reduction. Subsequent, flight tests on a full-scale experimental helicopter in open and closed loop configuration not only verify the functionality of the in-flight tracking control system, but also validate the insignificance of the degradation in control performance due to transfer matrix symmetrization predicted by the theoretical analysis.

In view of the surplus torque and complexity of controlled plant in passive electrical load system, a novel approach based on single neuron PID adaptive control and repetitive control for repetitive periodic load control system is proposed. Radial basis function (RBF) neural network is used to identify the system on-line for the single neuron PID controller to adjust its weights and PID parameters by self- learning and self-adapting based on the desired output. The dynamic state performance can be improved by the single neuron adaptive PID control and the steady state performance is also improved by modified repetitive control. Computer simulation results show that the force/position hybrid control system can effectively reduce the surplus torque and improve the loading precision, and also it has fine dynamic and steady state performance and good robustness. The reliability of whole system is further improved.

Induction motors are robust and inexpensive machines and are widely used for variable speed control because of recent development of electronic technique. In the case that loads of the motors are compressors, pumps, and so on, the constant V/F control of the induction motors is usually employed because it is difficult to install speed sensors and accurate speed control is not required. In such loads, the rotational speed of the motors is considerably fluctuated because the load torque is pulsated. When frequency of the torque pulsation is close to the resonant frequency of the mechanical system, large vibration and acoustic noise are produced especially in low frequency region.In this paper, authors propose a method to suppress the variation of the rotational speed of the V/F controlled induction motor with a fluctuated load by feedforward compensation using a timing sensor of 1 pulse/rev. considering that the load torque varies periodically. The feedforward data by a period for the compensation is obtained by the learning control based on the repetitive control in which the motor speed is controlled by periodically reflecting the past speed error on the present V/F input to the inverter. Effectiveness of the proposed method is confirmed by approximate analysis, simulations and experiments.

This paper introduces a new method to improve the characteristic of an active magnetic bearing (AMB) control system by flux time derivative. The theoretical analysis and computer simulation results show that this method can improve the phase margin effectively, and simplify the design and realization of the compensation device. >

The utilization of inverters for the interconnection of distributed generators to the grid requires application of control systems capable of regulating the active and reactive output current, ensuring high power quality levels and achieving relative immunity to grid perturbations. This paper proposes a simple current control scheme, based on the combination of deadbeat and PI control, for a three-phase voltage source inverter connected to the grid via an LCL filter. The control system is analyzed in the frequency domain and an analytical expression for the harmonic content of the output current is derived. Theoretical analysis and computer simulation results validate the stability, fast transient response and robustness of the proposed system to network disturbances and variations in filter parameters.

Elliptical gears are widely used in the fields of aerospace and automation equipment due to their excellent variable speed characteristics and compact structure. To reveal the control mechanism of phase angle on the motion characteristics of two-stage elliptical gear transmission system (TSEGTS) and improve its stability under variable speed loading, this paper proposes a modeling method that integrates two-dimensional tooth profile envelope method and image processing technology to extract tooth profile and analyze system motion characteristics. By introducing the fluctuation coefficient as a stability indicator, the system studied the effects of phase angle, input speed, and load torque on angular velocity, angular acceleration, and torque. The results indicate that the phase angle has a significant periodic modulation effect on the motion characteristics of the system. The angular velocity and acceleration of intermediate shaft B and output shaft C, as well as the torque of output shaft C, exhibit a distribution with 90° as the axis of symmetry within the range of 0°–180°. The average torque fluctuation coefficients of input shaft A and intermediate shaft B in the range of 0°–90° are 4.02 and 3.03, respectively, which are significantly higher than the 3.46 and 1.99 coefficients in the range of 90°–180°. As the input speed increases from 5π to 20π rad/s, the torque fluctuation coefficients of shafts A, B, and C increase from 2.87, 1.37, and 0.53 to 22.54, 14.19, and 8.43, respectively. When the load torque increases from 2 to 8 N·m, the fluctuation coefficients of the three axes decrease from 11.33, 7.12, and 4.22 to 3.51, 1.91, and 1.05, respectively. The increase in load torque effectively suppresses fluctuations and improves meshing stability. The experimental and simulation results are consistent, verifying the effectiveness of the model. The research results can provide theoretical basis for parameter optimization and dynamic performance control of TSEGTS.

Authors have proposed a method to detect a slip frequency of a three phase squirrel-cage induction motor from rotor slot harmonics in earlier paper. In this paper, a method of torque and speed control of the induction motor using the proposed slip frequency detector is presented. The torque and speed control system is implimented considering characteristics of the slip frequency detector. Experimental results show that the proposed slip frequency detector realizes precise control of the rotor speed and torque over a wide range of the rotor speed (200–300 to 2500 rpm) exept for a low speed region.

This paper proposes a frequency separation type current control system for a grid-connected single-phase five-level inverter. The proposed control system realizes high tracking performance and high disturbance suppression performance. To obtain high tracking performance to the sinusoidal reference signal, a repetitive controller is applied to the current controller. The current controller with a repetitive controller is capable of tracking to fundamental frequency, without the steady-state error. The disturbance observer using a notch filter (notch type disturbance observer) is used to obtain the high disturbance suppression performance. Using the notch type disturbance observer, the frequency components except for the fundamental frequency are suppressed. The proposed control system is configured by combining the current controller with a repetitive controller and a PI controller, and adding a notch type disturbance observer. Numerical simulation results and experimental results confirm that the proposed control system effectively reduces the output current distortion. The THD of the output current is reduced by 15.5 % when using the proposed control system.

A repetitive control theory is proposed to solve the synchronization problem between the wafer stage and reticle stage. A macro-micro control method is used based on a macro-micro control structure in which a linear motor is combined with a voice coil motor. A synchronization controller of the reticle stage is added base on the conventional PID control system. The repetitive controller is designed based on the repeated movement of the reticle stage and the wafer stage during the scan and exposure period, and the effects of synchronization control system can be improved because of the repetitive control can effectively track and inhibit the periodicity excitation signal. The repetitive control system effectively reduces the synchronization error during the scan and exposure period，in the meanwhile keep the tracking accuracy and dynamic characters. Simulation results show that the synchronization error can be reduced effectively.

During real-time operation of electric vehicles, motor parameter variations can significantly effect and deteriorate control performances of electric traction drives. For an open-loop torque control system, the parameter mismatch between the electric motor and the controller results in large steady-state error of the output torque response. This paper presents an adaptive torque controller based on Model Reference Adaptive Control technique for Interior Permanent Magnet Synchronous Motor drive systems. The proposed adaptive torque control scheme incorporating with a low-pass filter based torque estimator can provide the robustness against motor parameter variations. The simulation results show that the proposed torque control system using SVPWM-based vector control scheme can meet torque tracking requirements, and minimize steady-state error caused by parameter variations.

To reduce traditional direct torque control (DTC) system low speed control precision and the large torque ripple in low speed, a fuzzy control system of DTC was proposed. On the basis of conventional PI regulator, a fuzzy speed PI regulator was designed according to speed error and its rate of change, which could adjust the proportional coefficient k <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</inf> and integral coefficient k <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</inf> dynamically to adapt the system to the speed variations, and advanced the self-adaptation of speed. In voltage vector fuzzy controller model, the stator flux angle, the stator flux error, and the torque error are reasonably fuzzified into several fuzzy subsets to optimize selection of the voltage vector and decrease the torque ripple. The experimental results show that the proposed fuzzy control system not only can ensure swift speed response, small overshooting, and high steady speed precision, but also can effectively decrease torque ripple in low speed. Additionally, the system improves the observation precision of the stator flux and enhances the robustness of the whole system.

The physical and chemical changes occurring in blood as a consequence of microbial activity can be used as quantitative indicators of the presence of microorganisms in blood cultures. This paper reports on the theoretical analysis and computer simulation of the changes in the physical and chemical properties of blood expected as a result of the presence of microorganisms and explores the possibilities of spectrophotometric systems for the early detection of pathogens. It is concluded that multi‐wavelength reflectance methods are suitable and that the approach reported herein can lead to considerable simplifications and cost reduction of blood culture systems.

This article analyzes the main directions and principles of developing a mathematical model for creating an intelligent system for vector-frequency control of asynchronous electric motors. Particular attention is paid to the development of a frequency converter structure that allows the implementation of an energy-saving algorithm in a direct torque control (DTC) system to reduce stator current consumption from the power source. This approach guarantees stable operation of the electric motor under various load conditions and voltage changes in the electrical network. The synthesis of a speed control system and current control loops are considered and generalized models of a vector control system are developed using the Matlab software package and the main Simulink library.

Repetitive dynamic matrix control for systems with periodic specifications

The research and development results on the con- trol system design governing by the thermal field into the solid sample are given. The design is based on the following steps: 1) definition of model for thermal field dynamics, 2) prior (in first approximation) spectral decomposition of the field, 3) identifica- tion of field and sample parameters, 4) improved spectral de- composition. Computer simulation and implementation of the control system was performed for 1D sample. The efficiency and high accuracy of control system and control algorithms are demonstrated in details. I. INTRODUCTION The design of systems for control of the fields in distrib- uted samples (e.g., thermal or deformations field, form of wave front etc.) when external perturbations take place is a very complicated problem (even for linear systems). The root is that the system under control has infinite number degrees of freedom while real system can have under the control only finite number of degrees of freedom. So there is a competi- tion between high accuracy of a control and excessive com- plexity . The finding of this problem solution is under the de- tail investigation in this paper. To that end the theoretical modeling, computer simulation and implementation in ex- perimental device of the control over distributed sample have been done and definite recommendations for precision con- trol system design are proposed. A number of methods of analysis, control modeling and engineering implementations were developed for design of control of distributed samples. For example in paper (1) plasmotronic dynamics is investigated. Distributed system is approximated by finite-dimensional system for which regula- tor was synthesized that is helped to decrease transition time up to 3…4 times. In the paper (2) method was proposed for control of distributed systems under the uncertain environ- ment by using so called sliding mode. The specific problem of this kind is the design of control over the space-distributed thermal field when only finite number of heaters concentrated near some space points are in use. In the paper (3) review of physical models and engineering solutions for methods of wave front compensation in optical systems is given. There are many other methods were developed for different kinds of application. But nevertheless the problem of control systems design over the fields is still far from its termination. In our investigation the system for automatic compensation of external thermal disturbances in solid sample is studied which serves for precision control of temperature drops over the sample. This system was named as Control System for Thermo-Gradient Stabilization (CSTGS). Decomposition of the thermal field have been done on the base of harmonics method or in the other terms spectral method (4). The advantages of the spectral method over the finite-difference method are marked out in the papers (5), (6). Parameters of the model (parametric identification) may be calculated (ideal identification) by analysis of model prop- erties. But the most appropriate parametric identification are given by experimental measurements. It is shown in our pa- per that only by this way it is possible to achieve high effec- tiveness and high accuracy of control. In what follows we will refer to experimental realization of CSTGS that was specially designed for the purposes of inves- tigations of the control theory problems mentioned above.