Jen-te Yu

Model-Free Predictive Current Control for Interior Permanent-Magnet Synchronous Motor Drives Based on Current Difference Detection Technique

A model-free predictive current control (PCC) of interior permanent-magnet synchronous motor (IPMSM) drive systems based on a current difference detection technique is proposed. The model-based PCC (MBPCC) of IPMSM requires knowledge of parameters such as resistance, q-axis inductance, and extended back EMF. This paper develops a new model-free approach that alleviates the need for excessive prior knowledge about the system and only utilizes the stator currents as well as the current differences corresponding to different switching states of the inverter. Despite the salient difference of the proposed approach, it adopts a measure similar to that in the MBPCC approach to obtain the next switching state of the inverter by minimizing a cost function. It is noteworthy that the proposed method is easy to implement due to its simplicity and free of any multiplication operation. For comparison purposes, a digital signal processor, TMS320LF2407, is used to execute the two aforementioned current control techniques. Several experimental results show that the proposed method can significantly improve the current-tracking performance.

An Optimal Compensation Framework for Linear Quadratic Gaussian Control Over Lossy Networks

In this technical note, we study the compensation problem of LQG control over two lossy networks under TCP-like protocols and propose a new static and latest-control based compensation framework. Compared to two popular strategies, the zero-input and hold-input compensators and the recent generalized hold-input compensator by Moayedi et al. our new one is more general. The contribution of the new framework is in three aspects. Firstly, it takes the problem of LQG control over lossy networks to a new level by suggesting that the original problem should be more properly posed as a two-variable instead of a one-variable optimization problem. Secondly, it links the compensator gain selection and the minimization of quadratic cost together and bridges the gap between the two by providing an optimal gain selection. Thirdly, it incorporates the above three classes of compensators as special cases. The issue as to why none of the zero-input and hold-input compensation strategies can be claimed to be better than the other is to a great extent settled. Performance comparisons of the proposed method and the predictive outage compensator by Henriksson et al. and the generalized hold-input strategy by Moayedi et al. are made through numerical examples.

Design and Control of Phase-Detection Mode Atomic Force Microscopy for Reconstruction of Cell Contours in Three Dimensions

Atomic force microscopy (AFM) is capable of producing accurate 3-D images at nanometer resolution. As a result, AFM is widely used in applications related to cell biology, such as the diagnosis and observation of tumor cells. This paper proposes phase-detection mode atomic force microscopy (PM-AFM) for the 3-D reconstruction of cell contours. The proposed three-axis scanning system employs two piezoelectric stages with one and two degrees of freedom, respectively. Accurately rendering the contours of delicate cells required a multi-input multi-output (MIMO) adaptive double integral sliding mode controller (ADISMC) in the xy-plane to overcome uncertainties within the system as well as cross-coupling, hysteresis effect, and external disturbance. An adaptive complementary sliding-mode controller (ACSMC) was installed along the z axis to improve scanning accuracy and overcome the inconvenience of conventional controllers. Phase feedback signals were also used to increase the sensitivity of scanning, while providing faster response times and superior image quality. A comprehensive series of experiments was performed to validate the performance of the proposed system.

A sensorless position control for four-switch three-phase inverter-fed interior permanent magnet synchronous motor drive systems

In this paper, a sensorless position control for four-switch three-phase (FSTP) inverter-fed interior permanent magnet synchronous motor (IPMSM) drive systems is proposed and studied. Unlike traditional sensorless position controls that are based on zero-voltage switching mode generated by a six-switch three-phase (SSTP) inverter, the proposed method utilizes the nature of the FSTP inverter; that is, only four active-voltage switching modes are generated. Using basic circuit theory, the relationship between the rotor position and the current-slope differences can be derived and expressed as 24 transformation matrices. The current-slope differences are calculated by two stator current slopes corresponding to the two different active-voltage switching modes. By reducing the number of power switches and using the proposed method to eliminate the encoder, a cost-effective FSTP inverter-fed sensorless IPMSM drive system is developed. Moreover, no additional hardware circuits and no switching strategy change are required for existing drive systems. Simulation results are shown to demonstrate the feasibility and effectiveness of the proposed method.

Synthesis of static output feedback SPR systems via LQR weighting matrix design

In this paper we propose an approach using linear quadratic regulator (LQR) weighting matrices to synthesize strictly positive real (SPR) systems by static output feedback. The systems being considered are linear time-invariant (LTI). We first recall full state feedback LQR design. The two weighting matrices for state and control input respectively in the performance index are then used as two free parameters to design the SPR controller. By connecting strictly positive realness with full state feedback LQR through the algebraic Riccati equation associated with the latter and imposing well-posed condition in terms of positive definiteness on the weighting matrices, we show that the proposed formula for weighting matrices in this paper can render the resulting closed loop system SPR. The stabilizing static output feedback gain which is designed to make the closed loop system SPR becomes readily available once the two LQR weighting matrices are determined. Moreover, from the derived explicit form of control gain, we can achieve SPR synthesis even when system matrices are partially known. We provide in the end a numerical example to validate the approach.

A new compensation framework for LQ control over lossy networks

In this paper we study the compensation problem of LQ control over lossy networks under TCP-like protocols. The system we consider is discrete, linear, and time-invariant. Firstly, a general framework for static compensation is proposed. Secondly, using dynamic programming and optimization method we are able to get governing equations for the controller and the compensator gains that are optimized. Under the new framework, the two popular compensators: zero-input and hold-input appear to be special cases of the proposed one, and the issue as to why none of the above two commonly adopted compensation strategies can be claimed to be better than the other is to a great extent clarified. An iterative algorithm is also presented to solve the governing equations for the optimal gains obtained in the paper. Following that we provide two numerical examples to validate the new approach.

Model-free predictive current controller for four-switch three-phase inverter-fed interior permanent magnet synchronous motor drive systems

In this study, a model-free predictive current controller (MFPCC) for four-switch three-phase (FSTP) inverter-fed interior permanent magnet synchronous motor (IPMSM) drive systems is proposed. A new method, using the stator current and its difference is proposed to predict the next stator current. The advantages of the proposed MFPCC are low computation, simple to realize, and insensitive to parameter variations. The switching state that minimizes a defined cost function, which is used to evaluate the current error at the next switching state, is obtained to control the drive signals of the FSTP. Due to its simplicity and powerfulness, the proposed method provides an alternative current controller for the FSTP inverter-fed IPMSM drive system. For comparison purpose, the MFPCC and a traditional hysteresis current controller (HCC) for a FSTP inverter-fed IPMSM drive system have been implemented using a digital signal processor, TMS320LF2407. The experimental results show that the proposed MFPCC outperforms the traditional HCC in both steady-state and transient current tracking responses.

An improved predictive current control for interior permanent magnet synchronous motor drives based on current difference detection

An improved predictive current control for interior permanent magnet synchronous motor (IPMSM) drive systems using current difference detection technique is proposed in this paper. First, a conventional model-based predictive current control for IPMSM is introduced, which needs the information of the resistance, q-axis inductance, and extended back-EMF of IPMSM to predict the future current. To remove the usage of all these parameters in the conventional predictive current control algorithms, a new method that only uses the stator current and the current difference is proposed to predict the future stator current at the end of the next switching interval for all possible switching states. Then, the voltage vector that minimizes a defined cost function, which is used to evaluate the current error at the next switching state, is obtained to control the drive signals of the inverter. Also, the proposed method is very simple and can be effectively implemented due to its low computation without using any multiplication operation. A digital signal processor, TMS320LF2407, is used to execute the predictive current control algorithm. Several experimental results show that the proposed method can effectively improve the system performance in terms of current tracking compared to conventional methods.

Model-based predictive current control for four-switch three-phase inverter-fed IPMSM with an adaptive backstepping complementary PI sliding-mode position controller

In this paper, we propose a model-based predictive current control (MBPCC) scheme for four-switch three-phase (FSTP) inverter-fed interior permanent magnet synchronous motor (IPMSM) drive systems based on a three-phase extended back-EMF estimation method. First, we estimate the three-phase extended back-EMFs of IPMSM using the information of the stator currents, the q-axis inductance, and the stator voltages. After that, the future stator currents are predicted for four possible switching states generated by the FSTP inverter. By defining a cost function which is related to current errors, one can select a switching state that minimizes the cost function. Then, the future switching state of the FSTP inverter at the next sampling time can be determined to directly control the drive signals of FSTP. In addition, to improve the performance of the closed-loop system, an adaptive backstepping complementary PI sliding-mode (ABCPISM) position controller is proposed. The stability of the closed loop system is proven by Barbalats lemma. Simulation results are provided to validate the proposed method.

Passivity-based adaptive sliding-mode speed control for IPMSM drive systems

A passivity-based adaptive sliding-mode control is proposed for speed tracking of interior permanent magnet synchronous motor drive systems. Firstly, a nonlinear model of the IPMSM is given with uncertainties embeded. Through adaptive feedback passivation design, the closed-loop system is shown to be feedback equivalent to a strictly passive system with a designated input. The unknown system parameters are dealt with by designed adaptation laws in parallel with the design of the controller. Maximum torque per ampere condition is met through the design of d- and q-axis currents, which serve as the inputs to the motor. Asymptotic stability of closed loop system is proven by passivity theorem and Barbalats lemma. Simulation results show good speed tracking response and good performance.