Volume 4 Issue 1
Authors: Wang Jian-hong; Zhu Yong-hong
Abstract: The problem of designing two-feedback controllers for an unknown plant is studied based on input-output measurements within a linear setting. The virtual reference feedback tuning control is a direct method that aims at minimizing a control cost of the 2-norm type by using a set of data about the plant. No model identification of the plant is needed. For the optimization problem in designing controllers, an iterative separable least-squares identification method is proposed by means of the separable principle. The identification method not only searches for the global optimum solution of the designed criterion with respect to the parameter vectors, but also reduces the possibility of convergence to a local minimum. When applied the virtual reference feedback tuning to a two-degrees of freedom control system, the extension of the filter expression used to reprocess the input-output measurement data is derived. Based on this filter , we can prove the equivalence between our virtual reference feedback tuning control and the model reference adaptive control Finally the simulation example results confirm the theoretical results.
Keywords: Virtual Reference Feedback Tuning; Nonlinear Least-Squares Method; Global Optimum
Authors: Yazdan Bavafa-Toosi
Abstract: The contribution of the article is threefold. In the first part of this article the literature is surveyed for simple computation-free criteria for the verification of stability/instability of discrete-time systems. Numerous results are reported which are missing in standard texts on discrete-time control systems. In the second part new results in the same spirit are presented. They are in terms of necessary or sufficient conditions, free from computational burden, and thus much appealing to the systems and control community. These criteria are derived using the Rouche’s theorem which although has found numerous applications in systems and control theory is not unanimously known by engineering academicians. The third part of this article is a concise introduction to this theorem. The literature is also surveyed for its applications in the field and several ways of its manifestation are reported and classified.
Keywords: Discrete-Time Systems; Robustness; Rouche’s Theorem; Stability Criteria
Authors: Mallela Rajesh Babu; P.S.V. Kishore; Yannam Ravi Sankar
Abstract: In this paper, a pulsation current optimization control method is proposed for reducing torque ripple in brushless dc drives using Genetic Algorithm based Proportional Integral control (GA-PI). In general torque ripple occur due to pulsation current and input voltage in the brushless dc drive during commutation intervals. This torque ripple is function of the input voltage which is applied to the electronic commutation circuit in the brushless dc drive. Based on this, a novel control method has been proposed to reduce the torque ripple during the commutation intervals. With this method, the pulsation current is controlled by employing GA-PI to reduce the torque ripple by controlling the input voltage during the commutation intervals. The proposed method primarily reduced the torque ripple in comparison to conventional methods during commutation intervals. Simulation results are presented to validate the proposed method in comparison with the conventional methods.
Keywords: Brushless DC Motor; Current Ripple; Torque Ripple; Genetic Algorithm (GA); Z-N Method; PI Controller; Percentage of Ripples; Ripples Per Second (RPS);Maximum Peak Overshoot
Authors: Min Zeng; Cheng-Zu Hu; Peng-Fei Hu
Abstract: In some application situations, a stepper motor acceleration on a specific curve does not make full use of its acceleration performance. By analysing the motion characteristic of a stepper motor, this paper introduced an acceleration curve control algorithm suited to the torque-frequency characteristic of stepper motors. Compared to traditional S-curve acceleration, the new algorithm consisted of three movement stages: exponential increasing acceleration, constant acceleration, and decreasing acceleration. Simulations of the presented algorithm and the S-curve acceleration algorithm were conducted in MATLAB/Simulink, and the two algorithms were compared to each other in aspects of speed, acceleration, angular displacement, and number of steps. The simulation results showed that the presented acceleration curve control algorithm brought the driving capability of the stepper motor into full play, reduced starting time, and provided a favourable dynamic response. Under the control of the developed algorithm, the stepper motor accelerated faster in unit time when starting at 100 Hz and ending at 1200 Hz. The smooth curves of velocity and acceleration can avoid falling out of step, curb overshoot of the stepper motor, and reduce mechanical flexible impact.
Keywords: Acceleration Curve Control Algorithm; Acceleration Performance; S-curve Acceleration; Stepper Motor
Authors: Jian-hong Wang; Yan-xiang Wang; Yong-hong Zhu
Abstract: A data-driven method is used to detect anomalies in the formation of multi-UAVs from input and output data sequences corresponding to each UAV. As this special method does not require prior structural information of the UAV, it avoids the complexity introduced by multi-hypothesis testing and probability inequalities. The established nonlinear unknown form corresponding to each UAV can be well approximated by basis functions and converted to a linear regression form which includes one multiplication operation between a regression and a parameter vector. The parameter vector is identified by the least square method; one anomaly detector is then constructed based on the derived residuals. When only the inputs are included in this nonlinear form, the anomaly detector using the consistent parameter estimations demonstrates improved performance. However, when the inputs and outputs are all included simultaneously, the parameter estimations derived by the least square method are all biased. These biased estimations seriously affect the final anomaly detector. In order to avoid this bias, the bias compensated terms are added into the bias estimations. Furthermore, this paper also proves the specified expressions representing the derived bias compensated terms and the consistent property. A method to replace some of the matrices in the bias compensated terms is also proposed. Finally, results of an example simulation confirm the theoretical identification results.
Keywords: Multi-UAV Formation; Anomaly Detection; Nonlinear System Identification; Bias Compensated Estimation
Authors: Yan-xiang Wang; Yong-hong Zhu; Zhi-feng Xiao; Jian-hong Wang
Abstract: In this paper, the identification accuracy of unknown parameters are analyzed in one second order system. The asymptotic covariance expressions about unknown parameters are derived by using the matrix inversion formula. When one or two parameters are known, the asymptotic covariance expressions corresponding to other parameters are derived. By comparing these asymptotic covariance expressions, we find that the identification accuracy of other parameters did not show any improvement if one parameter is known previously. Also, if each parameter of the other three is known, the identification accuracy of other parameters improves. Finally, the efficiency of the proposed strategy can be confirmed by the simulation example results.
Keywords: Second Order System; Prior Parameter; System Identification; Accuracy Analysis
Authors: Anup Kumar Gogoi; Venkata Ramana Kasi; Somanath Majhi
Abstract: An online relay test is performed to obtain process model parameters of an underdamped system with delay. Measurements made on the limit cycle response curve are used to identify the system dynamics. It is difficult to obtain the required limit cycle data during load disturbance due to the asymmetric limit cycle. A Dual Input Describing Function (DIDF) is used to extract the limit cycle data with and without load disturbances. The effectiveness of the identification technique is tested in the presence of load disturbances. A proportional-integral-derivative (PID) controller is designed for the identified underdamped system using the direct synthesis method.
Keywords: Asymmetric Limit Cycle; Dual Input Describing Function; Measurement Noise; Relay
Authors: Faisal S. Al-Kamali; Abdullah A. Qasem; Samah A. Abuasbaa; Gehan A. Qasem
Abstract: Orthogonal frequency division multiple access (OFDMA) and Single carrier frequency division multiple access (SC-FDMA) systems are new systems, which have become a preferred choice for current and future wireless communications. This is attributed to their advantages such as the use of frequency domain equalizers. In this paper, the issue of the wireless image transmission over OFDMA and SC-FDMA systems is investigated over a frequency selective channel for different modulation and subcarriers mapping schemes. Experimental results show that efficient wireless image transmission over OFDMA and SC-FDMA systems is possible. It is found that the interleaved systems greatly enhance the clarity of the received image and their performances are better than that of the localized systems. Results also show that the SC-FDMA system provides better performance than the OFDMA system when the 16QAM modulation scheme is used and a worse performance than the OFDMA system when the QPSK modulation scheme is used.
Keywords: Image Transmission; OFDMA; SC-FDMA; Subcarriers Mapping Schemes and Modulation Schemes
Authors: Mallela Rajesh Babu
Abstract: In this paper, an industrial paper plant model was approximately modelled as integrator pole time delay zero (IPTDZ) plant model. The IPTDZ model described the dynamics of the steam valve to steam pressure in an industrial paper plant. In this paper, a new set of optimal PID controller parameters were obtained for the IPTDZ plant model for setpoint regulation and disturbance rejection using dimensional analysis and the PSO optimization technique. These control parameters were designed to reject disturbances and take action to force the process variable back toward the desired setpoint whenever a disturbance or load on the process caused a deviation. Dimensional analysis is a problem-solving method that uses any number or expression that can be multiplied by one without changing its value. It is a useful technique for obtaining relationships between PID parameters. Particle swarm optimization (PSO) is a computational method that optimizes problems by iteratively improving a candidate solution with regard to a given measure of quality. This paper showed how to obtain optimal PID controller parameters for load disturbance rejection and setpoint regulation by minimizing integral square time error (ISTE) performance index in an IPTDZ plant model. Simulation results were presented to validate the proposed method in comparison to the Ola Slätteke (OSK) method.
Keywords: PID Controller; Integrator Pole Time Delay Zero (IPTDZ) Model; Integral Squared Time Error (ISTE); Load Disturbance; Ola Slätteke (OSK) Design; Setpoint Regulation; Dimensional Analysis; Particle Swarm Optimization (PSO)
Authors: Bachir Nail; Belkacem Bekhiti; Abdelhakim Dahimene; Kamel Hariche
Abstract: In this paper, a new algorithm based on the theory of matrix polynomials with the help of the kronecker product was proposed, which can assign both block-roots (solvents) and block-eigenvectors in order to achieve desired objectives with latent structure specifications. Two types of control were treated and legibly studied, then numerically are shown to be practical, powerful and effective. They are the state and state-derivative feedback. The method proposed here allows the assignments of block-roots, which can alter both stability and the rate of decay. On the other hand, assignments of the block-eigenvectors determine the relative shape of the response. The necessary condition for the system to have block-assignment is the block-controllability or block-observability.
Keywords: Solvents; State-derivative; Block-roots, Block-eigenvectors; Latent Structure; Matrix Polynomial
Authors: Jian-hong Wang; Yong-hong Zhu; Xiao-yong Guo
Abstract: Here, we construct a new confidence region to test the quality of closed loop system identification. This confidence region with respect to model parameters is derived based on an asymptotic normal distribution of the parameter estimator and its covariance matrix, which are estimated from sampled data. The uncertainty bound of the model parameter is constructed in the probabilistic sense by using the inner product form of the asymptotic covariance matrix. Further, the statistical analysis result is used to design the optimal input signal. Thus, our result in this short paper can extend the breadth of the system identification field. Finally, the simulation example results confirm the theoretical identification results.
Keywords: Closed Loop Identification; Model Uncertainty; Confidence Region Test
Authors: Chitralekha Mahanta; Somanath Majhi; Gargi Baruah
Abstract: In this paper, relay-based auto-tuning of a fractional order proportional integral and derivative (FOPID) controller is proposed for second order plus dead time (SOPDT) plants. The controller is experimentally verified via a coupled tank system (CTS). The process dynamics of overdamped, underdamped, and critically damped plants are first modelled by using an offline relay-based method, where a maximum of four unknown parameters are determined in the simplest possible way. The describing function (DF) is obtained by considering relay with hysteresis. The use of robust features like gain margin and phase margin, as well as iso-damping property to tune the five parameters of the controller greatly improves the controlled system’s performance. A significant advantage of the proposed tuning method is that a priori information of the system’s gain and phase crossover frequencies is not required while tuning the controller. The proposed model is validated through simulation studies in a class of process models, and also verified experimentally on a CTS from Feedback.
Keywords: FOPID; SOPTD; Auto-Tuning; Iso-Damping; Gain Margin; Phase Margin; Gain Crossover Frequency; Coupled Tank System (CTS)