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Tran, Thuong Ngoc-Cong,Nguyen, Ha Xuan,Park, Jae Wan,Jeon, Jae Wook Institute of Electrical and Electronics Engineers 2019 IEEE transactions on industrial electronics Vol.66 No.7
<P>This paper proposes a method to improve the accuracy of an absolute magnetic encoder by using harmonic rejection (HR) and a dual-phase-locked loop (DPLL). The encoder consists of two permanent magnets: an edge-located multipolar magnet (MPM) and a center-located bipolar magnet, in which the signal-processing accuracy of the MPM is crucial for achieving high accuracy of the entire encoder. However, the MPM signals are disturbed by nonidealities such as dc offsets, amplitude mismatch, low- and high-order harmonics, and random noises. In this paper, the HR approach investigates the characteristics of nonidealities of the phase detector and rejects them by using gradient descent. In addition, the DPLL remains robust by maintaining a zero steady-state error during a phase jump, a constant frequency, and a ramp frequency. The proposed method is simulated with MATLAB software and implemented in ARM STM32F407ZG. The obtained results demonstrate efficient performance. This method can be applied to any use of quadrature sinusoidal signals, such as in power grids and in permanent-magnet synchronous motor phase detection.</P>
Nguyen, Ha Xuan,Tran, Thuong Ngoc-Cong,Park, Jae Wan,Jeon, Jae Wook Institute of Electrical and Electronics Engineers 2019 IEEE transactions on industrial electronics Vol.66 No.6
<P>Absolute magnetic encoders (AMEs) use two magnets: a ring multipolar magnet (MPM) generating high-resolution and improving the accuracy for the encoder, and a bipolar magnet in the center calculating the number cycle of MPM signals. The phase outputs of these AMEs are tracked from the sinusoidal signals of the MPM. However, these sine/cosine signals are disturbed by amplitude differences, offsets, phase-shift, harmonic components, and random noise. In order to solve this problem, this paper presents an adaptive linear neuron based on a third-order phase-locked loop (ALN-PLL) to improve the accuracy of AMEs. The proposed approach consists of two main parts: The first part is an ALN algorithm that uses the phase feedback of the third-order PLL in order to build the mathematical model of input signals, and then reject the disturbances. The second part is a third-order PLL that is designed based on a dominant pole approximation algorithm. The proposed PLL can reduce noise and eliminate dc-error during the phase step, frequency step, and frequency ramp. The simulation and experimental results demonstrate the effectiveness of the proposed approach.</P>
Improve Efficiency Multi-Turn Magnetic Encoder that uses Gear System
Jae Wan Park,Ha Xuan Nguyen,Thuong Ngoc-Cong Tran,Jae Wook Jeon 제어로봇시스템학회 2017 제어로봇시스템학회 국제학술대회 논문집 Vol.2017 No.10
This paper presents a method for the improvement of the performance of a gear-system-based battery-less multiturn absolute magnetic encoder (BLMA-ME). these encoders, the magnetic absolute encoder requires several subshafts and gear systems for the detection of multiple rotations. This paper describes some of the problems of the encoder for which a gear system is used, and a method to increase the resolution and accuracy.
Dynamic Modeling and Control of Production/Inventory System
Hwan-Seong Kim,Xuan-Thuong Tran 한국항해항만학회 2011 한국항해항만학회 학술대회논문집 Vol.2011 No.추계
This paper presents the system dynamics methodology for modeling and control the production/inventory system. Under system dynamics point of view, we can apply some production/inventory policies as if we use the control laws for dynamics systems, then the behavior of system is analyzed and evaluated to improve the performance of production/inventory system. We also utilize the hybrid modeling method for the dynamic of production system with the combination of Matlab/Simulink and Matlab/Sateflow. Finally, the numerical simulation results are carried out in Matlab/Simulink environment and compare with the results from other works. It is shown that our approach can obtain some good performances (such as operational cost, stability of inventory, customer service level).
Study on robust controller for underwater vehicle using LQG/LTR approach
Hwan Seong Kim,Xuan Thuong Tran,Sam Sang You 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.6
Underwater vehicle is more and more attracted by many researchers due to the widely applications in a lot of fields such as ocean explore, resource exploitation, underwater pipe system inspection,…Control the underwater vehicle is a challenging problem because the effect of underwater environment changes overtime and also is unknown. Thus, it is needed to design a robust controller to guarantee the robust stability and performance of system under unknown disturbances. In this paper, we present an approach to the design of robust controllers using the LQG/LTR (Linear Quadratic Gaussian/loop-transfer recovery) design methodology. It is based on the fact that the linear quadratic regulator (LQR) using state variable feedback has certain guaranteed robustness properties. First, the full-state variable feedback was designed and then the observer or Kalman filter provides the state estimates for feedback purposes. The observer allows full recovery of the guaranteed robustness properties of the LQ regulator with state feedback. To verify the designed controller, the numerical simulation was implemented with the design of autopilot of ROV in depth and pitch control.