A nonlinear speed observer for permanent-magnet synchronous motors

The application of vector control techniques in AC motor drives demands accurate position and velocity feedback information for the current control and servo control loops. The authors describe a speed observer system suitable for use with permanent magnet synchronous motors as a software transducer. The observer is developed from the dq model of the machine. Design considerations for the observer are discussed. The nonlinearities in the machine model present a problem to the observer design, so a state detection technique is used to achieve global stability and consistent convergence of the observer system. The simulations show that the performance of the observer is robust against noise and parameter uncertainties     

On speed and rotor position estimation in permanent-magnet ACdrives

This letter deals with rotor position and speed estimation of permanent magnet AC drives. Two reduced-order observers, a linear (AO) and a nonlinear one (NLO), are compared, an adaptive speed estimation scheme is also considered, analysis and simulations show that the NLO has better performance and demands less computational load than the AO plus the adaptive scheme     

Hybrid rotor position observer for wide speed-range sensorless PM motor drives including zero speed

This paper addresses the problem of wide speed-range sensorless control of a surface-mount permanent-magnet (SMPM) machine including zero-speed operation. A hybrid structure integrating a flux observer and signal-injection techniques is proposed, which results in a rotor position signal independent of motor parameters at low and zero speed. Although the SMPM machine typically has a very low geometric saliency, the injection technique is effective in tracking the saturation-induced saliency produced by the stator flux. Experimental results are presented showing an excellent performance for both the sensorless speed and position control using an off-the-shelf SMPM machine.     

Flux observer with online tuning of stator and rotor resistancesfor induction motors

This paper proposes an adaptive flux observer for induction motors, where stator and rotor resistances are estimated in online environments. The variation of motor parameters during operation degrades the performance of the controller and the flux observer. Among the parameters of induction motors, rotor resistance is a crucial one for flux estimation, and stator resistance also becomes critical in the low-speed region. Under the persistent excitation condition, the proposed method estimates the actual values of stator and rotor resistances simultaneously, which guarantees the exact estimation of the rotor flux. The persistent excitation condition is not satisfied when the electric torque of an induction motor is absent due to the lack of rotor currents. Even in this case, the proposed method achieves the correct estimation of the rotor flux. Simulations and actual experiments show that the rotor flux is estimated in all operating conditions and that both resistances converge to their actual values when the electrical motor torque exists     

A general algorithm for speed and position estimation of AC motors

A computationally efficient speed and position estimation algorithm, generally applicable to AC motor drives, is designed and analyzed. Applications include: (a) sensorless permanent-magnet and reluctance synchronous motor drives using the fundamental excitation as information source; (b) sensorless drives using saliency and signal injection; and (c) sensored drives using resolvers. Particular attention is given for case (a). Low parameter sensitivity in the entire speed range (except at low speeds for the reluctance motor)-implying a small position estimation error-and good dynamic properties at nominal speeds are verified     

A state observer for the permanent-magnet synchronous motor

An identity state observer for the permanent-magnet synchronous motor is derived which reconstructs the electrical and mechanical states of the motor from current and voltage measurements. The observer operates in the rotor frame and estimates direct and quadrature stator currents, rotor velocity, and rotor position. Since the rotor position is estimated, the rotor reference frame is approximated using the latest rotor position estimate. The motor dynamics and the transformation into the estimated rotor frame are nonlinear, and thus the observer and observer error dynamics are nonlinear. Therefore, stability is analyzed using a linearized error model. Simulations including realistic measurement disturbances are used to investigate the global stability and accuracy of the observer     

A novel, robust DSP-based indirect rotor position estimation for permanent magnet AC motors without rotor saliency

This paper proposes and implements a novel rotor position sensorless technique for PM AC motor drives, which allows acceleration from standstill and can operate under various practical operating conditions including transient speed changes. The technique developed here relies on the measurement of the phase voltages and currents of the motor. It uses the incremental values of flux linkage, and the back-EMF functions to estimate incremental rotor position. Using a phase-locked loop (PLL) algorithm, an internal closed-loop correction algorithm can correct rotor position estimation drift, which may be due to the motor parameter variations or measurement inaccuracies. The method is implemented in closed-loop using a digital signal processor (DSP), and details of the implementation are provided in the paper. To demonstrate accuracy, robustness and reliability of the position estimation scheme, the paper presents a number of real-time experimental results, including dynamic operating conditions.     

Mechanical sensorless speed control of permanent-magnet AC motors driving an unknown load

A new sensorless scheme for high-performance speed control of permanent-magnet ac motors (PMACMs) driving an unknown load is proposed. This scheme uses an extended nonlinear reduced-order observer to estimate the induced electromotive force (EMF) and load torque. From the estimated variables, the rotor position, the rotor speed, and the position derivative of flux are calculated and are used to close the control loop. In order to improve the drive performance, the estimated load torque is incorporated as a feedforward signal in the closed control loop. In addition, the proposed sensorless PMACM drive allows the torque-ripple and copper-loss minimization for motors with an arbitrary EMF waveform. Simulation and experimental results to validate the proposal are presented in this paper.     

Torque-ripple minimization with indirect position and speed sensingfor switched reluctance motors

A torque-ripple-minimization controller is realized along with indirect position and speed sensing for switched reluctance motors (SRMs). The position and speed estimations are derived from a sliding-mode observer that requires terminal measurements of only phase voltages and currents. The research shows that position- and speed-sensorless observers can be reliably used for control of an SRM. Experimental results using a four-phase, 8/6 SRM and the TMS320C30 digital signal processor are presented. The results demonstrate position- and speed-sensorless closed-loop operation of a torque-ripple-minimized SRM drive     

Error analysis in indirect rotor position sensing of switchedreluctance motors

The phase excitation pulses of a switched reluctance motor (SRM) drive need to be properly synchronized with the rotor position for optimum torque production. Accuracy of this position information determines the efficiency and smoothness of the drive operation. This paper presents a method of analyzing the errors inherent to indirect rotor position sensing schemes. The error analysis in this paper breaks down the position error to its fundamental components in the position sensing system. As an illustration, the method is applied to two different indirect position sensing schemes. The same basic approach can be applied to evaluate other SRM position sensing schemes. The results are helpful in comparing the various sensing schemes, as well as focusing improvement efforts on the appropriate segment of the system     

New sensorless vector control using minimum-order flux state observer in a stationary reference frame for permanent-magnet synchronous motors

This paper proposes a new sensorless vector control method that can be applied to both of salient-pole and nonsalient-pole permanent-magnet synchronous motors (PMSMs). The proposed method estimates the phase of a rotor flux by a newly developed state observer in a stationary reference frame for sensorless vector controls of PMSMs. The flux state observer has the following attractive features: 1) it requires no steady-state conditions for the dynamic mathematical model of the motor; 2) its order is the minimum second; 3) a single observer gain is simply constant over a wide operating range and can be easily designed; 4) it utilizes motor parameters in a very simple manner; and 5) its structure is very simple and can be realized at a very low computational load. The proposed speed-estimation method, which exploits the inherent physical relation of integration/derivation between phase and speed, is very simple and can properly estimate rotor speed. The usefulness of the proposed method is examined and confirmed through extensive experiments.     

Nonlinear control of mechatronic systems with permanent-magnet DC motors

The current trends in development and deployment of advanced electromechanical systems have facilitated the unified activities in the analysis and design of state-of-the-art motion devices, electric motors, power electronics, and digital controllers. This paper attacks the motion control problem (stabilization, tracking, and disturbance attenuation) for mechatronic systems which include permanent-magnet DC motors, power circuity, and motion controllers. By using an explicit representation of nonlinear dynamics of motors and switching converters, we approach and solve analysis and control problems to ensure a spectrum of performance objectives imposed on advanced mechatronic systems. The maximum allowable magnitude of the applied armature voltage is rated, the currents are limited, and there exist the lower and upper limits of the duty ratio of converters. To approach design tradeoffs and analyze performance (accuracy, settling time, overshoot, stability margins, and other quantities), the imposed constraints, model nonlinearities, and parameter variations are thoroughly studied in this paper. Our goal is to attain the specified characteristics and avoid deficiencies associated with linear formulation. To solve these problems, an innovative controller is synthesized to ensure performance improvements, robust tracking, and disturbance rejection. One cannot neglect constraints, and a bounded control law is designed to improve performance and guarantee robust stability. The offered approach uses a complete nonlinear mechatronic system dynamics with parameter variations, and this avenue allows one to avoid the conservative results associated with linear concept when mechatronic system dynamics is mapped by a linear constant-coefficient differential equation. To illustrate the reported framework and to validate the controller, analytical and experimental results are presented and discussed. In particular, comprehensive analysis and design with experimental verification are performed for an electric drive. A nonlinear bounded controller is designed, implemented, and experimentally tested.     

Accurate rotor position detection and sensorless control of SRM for super-high speed operation

Based on the general nonlinear magnetizing model (GNMM) from our previous research work, an improved method of detecting rotor position for sensorless control of SRMs in super-high speed operation has been developed. With minimum input data, the approximated GNMM is obtained and the rotor speed estimated. Then the rotor position is detected by the motion equation. To remove rotor position error, the proposed scheme updates the reference at critical points using the flux observation. Further, the GNMM is adaptively tuned based on the updated information. The improved rotor position detection method has been implemented by fully exploring the computation power of the modern DSP. Laboratory verification on different types of SRMs with sensorless control up to 20000 rpm is accomplished.     

基于反电势观测器和锁相环的无刷直流电机霍尔位置误差补偿方法研究

针对无刷直流电机采用低分辨率霍尔传感器进行转子位置估计存在角度误差问题,提出基于反电势观测器和锁相环的误差补偿方法。根据霍尔传感器测量电角度原理,分析电角度固有安装误差和算法估算误差的原因,提出了结合反电势观测器重构角度误差,采用锁相环进行相位计算,实现对电角度误差进行补偿。在48V无刷直流电机上进行实验,通过对补偿后电角度和相电流响应比较,证明新方法能够有效的改善霍尔传感器角度误差问题,改善电流响应,实现对转矩脉动的抑制,能获得高效控制性能。     

An optimal speed controller for permanent-magnet synchronous motordrives

An optimal control system synthesis method which can achieve vector and speed control simultaneously for permanent-magnet synchronous motor (PMSM) drives is proposed in this paper. A state-space multiple-input-multiple-output (MIMO) model for PMSM is first developed and the compensation for the nonlinearities in this model is discussed. A pseudo-linearized PMSM model is dynamically constructed through the state detection, and subsequently an optimal speed controller is developed based on this linearized model. The integral control technique is incorporated to eliminate possible speed offsets. A speed observer is further developed to eliminate the speed sensor from the drive     

Automatic disturbances rejection controller for precise motion control of permanent-magnet synchronous motors

A highly robust automatic disturbances rejection controller (ADRC) is developed to implement high-precision motion control of permanent-magnet synchronous motors. The proposed ADRC consists of a tracking differentiator (TD) in the feedforward path, an extended state observer (ESO), and a nonlinear proportional derivative control in the feedback path. The TD solves the difficulties posed by low-order reference trajectories which are quantized at the sensor resolution, and the ESO provides the estimate of the unmeasured system's state and the real action of the unknown disturbances only based on a measurement output of the system. Simulations and experimental results show that the proposed ADRC achieves a better position response and is robust to parameter variation and load disturbance. Furthermore, the ADRC is designed directly in discrete time with a simple structure and fast computation, which make it widely applicable to all other types of derives.     

Neural speed filtering for induction motors with anomalies and incipient faults

Effective sensorless speed estimation is desirable for both on-line condition monitoring and assessment, and for efficiency calculation of induction motors running off the power supply mains. In this paper, a sensorless neural adaptive speed filter is developed for induction motors operating under normal and anomalous conditions, such as supply imbalance, as well as incipient faults, such as electrical, electromechanical, and mechanical faults. The filter is demonstrated by comparisons with experimental speed measurements and spectral speed estimates. In addition to nameplate information required for the initial setup, the proposed neural speed filter uses only measured motor terminal currents and voltages. Initial training of the speed filter is accomplished off-line, using rotor slot harmonic-based speed estimates. The developed speed filter is scalable and it has been used for speed estimation of induction motors with varying power ratings. Incremental tuning is used to further improve filter performance and reduce filter development time significantly.     

An extended electromotive force model for sensorless control of interior permanent-magnet synchronous motors

During the last decade, many sensorless control methods have been proposed for surface permanent-magnet synchronous motors (SPMSMs) based on the estimation of electromotive force (EMF) in which the motor's position information is contained. However, these methods cannot be applied to interior PMSMs (IPMSMs) directly, because the position information is contained in not only the EMF, but also the inductance of stators. In this paper, a new mathematical model for IPMSMs is proposed and an extended EMF is defined, which includes both position information from the EMF and the stator inductance. By using the newly proposed model, sensorless controls proposed for SPMSMs can easily be applied to IPMSMs. As an example, a disturbance observer is studied and the experimental results show that the proposed method on the proposed model is very effective.     

Implementation and experimental investigation of sensorless speed control with initial rotor position estimation for interior permanent magnet synchronous motor drive

In this paper, a new approach to sensorless speed control and initial rotor position estimation for interior permanent magnet synchronous motor (IPMSM) drive is presented. In rotating condition, speed and rotor position estimation of IPMSM drive are obtained through an extended Kalman filter (EKF) algorithm simply by measurement of the stator line voltages and currents. The main difficulty in developing an EKF for IPMSM is the complexity of the dynamic model expressed in the stationary coordinate system. This model is more complex than that of the surface PMSM, because of the asymmetry of the magnetic circuit. The starting procedure is a problem under sensorless drives, because no information is available before starting. The initial rotor position is estimated by a suitable sequence of voltage pulses intermittently applied to the stator windings at standstill and the measurement of the peak current values of the current leads to the rotor position. Magnetic saturation effect on the saliency is used to distinguish the north magnetic pole from the south. To illustrate our work, we present experimental results for an IPMSM obtained on a floating point digital signal processor (DSP) TMS320C31/40 MHz based control system.     

Robust speed control algorithm with disturbance observer for uncertain PMSM

This article suggests a robust cascade speed control algorithm for a permanent magnet synchronous motor (PMSM) combining the classical feedback linearising (FL) method and the disturbance observers (DOBs) without the integrators. The contributions of this method are twofold. The first one is to provide the simple DOBs for not only guaranteeing the closed-loop performance recovery property but also removing the steady-state errors without the integrators with respect to the tracking errors. The second one is to prove that the inner and outer loops are stabilised by the proposed cascade-type controller, simultaneously. The simulation and experimental results reveal that the proposed method maintains the speed tracking performance to be satisfactory for a wide operating region with the fixed control gain despite a plant-model mismatch where a 3-kW interior PMSM is utilised.