Design and control of an ultrasonic motor capable of generatingmulti-DOF motion

A multi-degree-of-freedom (DOF) ultrasonic motor consisting of a bar-shaped stator and a spherical rotor was developed. It can generate 3-DOF rotation of the rotor around perpendicular axes using the bending vibration and longitudinal vibration of the stator, which is designed using the finite element analysis. From the simulated driving characteristics, a control method for the ultrasonic motor is proposed. Following this, the driving characteristics of the motor under both open-loop and closed-loop controls were measured experimentally. The multi-DOF position control of the rotor was achieved successfully using the proposed control method     

一种新型旋转超声电机驱动控制试验系统

介绍了一种新型旋转超声电机即压电定子和压电转子振型嵌合式旋转超声电机驱动控制试验系统。系统以LabVIEW作为开发平台,通过DAQ板卡和外围电路的设计进行输入输出采集与控制。该系统能输出幅值、频率、相位可调节信号,通过光电编码器检测超声电机转子位置反馈给系统用以保证电机下次启动时保持定转子振型嵌合位置关系。试验结果表明,该试验系统完全满足此新型旋转型超声电机驱动控制试验要求。     

Sensorless position control of induction motors-an emergingtechnology

Concepts for the sensorless position control of induction motor drives rely on anisotropic properties of the machine rotor. Such anisotropies can be incorporated as periodic variations of magnetic saliencies in various ways. The built-in spatial anisotropy is detected by injecting a high-frequency flux wave into the stator. The resulting stator current harmonics contain frequency components that depend on the rotor position. Models of the rotor saliency serve to extract the rotor position signal using phase-locked loop techniques. A different approach makes use of the parasitic effects that originate from the discrete winding structure of a cage rotor. It has the merit of providing high spatial resolution for incremental positioning without sensor. The practical implementation of sensorless position identification and of a high-accuracy position control system are reported     

Sensorless field orientation control of induction machines based ona mutual MRAS scheme

A mutual model reference adaptive system (MRAS) is proposed to implement a position sensorless field-orientation control (FOC) of an induction machine. The reference model and adjustable model used in the mutual MRAS scheme are interchangeable. Therefore, it can be used to identify both rotor speed and the stator resistance of an induction machine. For the rotor speed estimation, one model is used as a reference model and another is the adjustable model. Pure integration and stator leakage inductance are removed from the reference model, resulting in robust performance in low and high speed ranges. For the stator resistance identification, the two models switch their roles. To further improve estimation accuracy of the rotor speed and stator resistance, a simple on-line rotor time constant identification is included. Computer simulations and experimental results are given to show its effectiveness     

Characteristics and control of a bidirectional axial gap combinedmotor-bearing

Introduces the design characteristics of a bidirectional axial gap combined motor-bearing where the flat disc motor has both rotation and axial position control capability. This motor consists of a disc rotor with a stator on each side of the rotor. The axial motion of the rotor is actively controlled while the other axes are constrained by additional passive or active radial magnetic bearings. Each stator produces a rotating magnetic flux in the air gap, to generate the motor torque. The axial force is controlled by changing the amplitude of the rotating flux. Both permanent-magnet motor and induction motor versions were analyzed theoretically and tested experimentally. The results demonstrated the capability of providing both the functions of a motor and a magnetic bearing     

Design and control of a permanent magnet spherical wheel motor

We present a permanent magnet–based spherical wheel motor that can be used in omnidirectional mobility applications. The proposed motor consists of a ball‐shaped rotor with a magnetic dipole and a hemispherical shell with circumferential air‐core coils attached to the outer surface acting as a stator. Based on the rotational symmetry of the rotor poles and stator coils, we are able to model the rotor poles and stator coils as dipoles. A simple physical model constructed based on a torque model enables fast numerical simulations of motor dynamics. Based on these numerical simulations, we test various control schemes that enable constant‐speed rotation along arbitrary axes with small rotational attitude error. Torque analysis reveals that the back electromotive force induced in the coils can be used to construct a control scheme that achieves the desired results. Numerical simulations of trajectories confirm that even without explicit methods for correcting the rotational attitude error, it is possible to drive the motor with a low attitude error (<5°) using the proposed control scheme.     

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.     

基于扭纵复合型超声电机动力学模型的模拟计算

基于动力学原理，利用一种新的扭纵复合型超声电动机的动力学模型，模拟计算了扭纵复合型超声电动机的转速、转矩、效率和响应时间等特性。计算结果揭示了预压力、定子两路振动振幅等输入参数对负载特性的影响。此外，转子运转的响应时间与负载力矩间的关系也可由模拟计算导出。利用该模型对所研制的复合型超声电机实验样机进行的计算结果与实际测量结果基本相符，验证了该模型及相应数值计算方法的可靠性。利用该模型首次计算出定，转子接触与分离点的不对称特性。     

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     

Analysis of direct torque control in permanent magnet synchronousmotor drives

This paper describes an investigation of direct torque control (DTC) for permanent magnet synchronous motor (PMSM) drives. It is mathematically proven that the increase of electromagnetic torque in a permanent magnet motor is proportional to the increase of the angle between the stator and rotor flux linkages, and, therefore, the fast torque response can be obtained by adjusting the rotating speed of the stator flux linkage as fast as possible. It is also shown that the zero voltage vectors should not be used, and stator flux linkage should be kept moving with respect to the rotor flux linkage all the time. The implementation of DTC in the permanent magnet motor is discussed, and it is found that for DTC using available digital signal processors (DSPs), it is advantageous to have a motor with a high ratio of the rated stator flux linkage to stator voltage. The simulation results verify the proposed control and also show that the torque response under DTC is much faster than the one under current control     

Novel rotor position extraction based on carrier frequency component method (CFCM) using two reference frames for IPM drives

In this paper a novel interior permanent-magnet (IPM) motor's rotor position extraction method from the carrier-frequency component signal, derived from pulsewidth-modulated (PWM) inverter switching, using two reference frames is presented. This method has been utilized for IPM motor vector control without a mechanical rotor position detector, extracting rotor position angle from the switching carrier-frequency (10 kHz) component current. It is effective for IPM motors, which have magnetic saliency, sinusoidal distributed stator winding, and are supplied by a PWM voltage-source inverter. The performance of two IPM motors' vector control without mechanical rotor position detector utilizing this method has been investigated. Experimental results demonstrating good dynamic and steady-state performance achieved are presented and discussed.     

Sensorless torque control of SyncRel motor drives

This paper describes a direct self-control (DSC) scheme for synchronous reluctance motor drives. The presented DSC scheme develops a new torque control methodology that does not require any position transducer to synchronize the stator current vector with the rotor. Such a control strategy differs from the conventional DSC approach in order to fit some specific requirements of synchronous reluctance (SyncRel) machines. First, torque and rotor position are controlled instead of torque and stator flux as in a conventional DSC scheme. Second, the operating sector is selected according to the actual position of the current vector rather than the position of the stator flux. The proposed methodology allows simplifying implementation of the torque control on SyncRel drives and reducing the global cost for medium-performance electric drives. Simulations and experimental tests on a 1.5-kW motor drive are provided to evaluate the consistency and the performance of the proposed control technique     

Online Stator and Rotor Resistance Estimation Scheme Using Artificial Neural Networks for Vector Controlled Speed Sensorless Induction Motor Drive

This paper presents a new method of online estimation for the stator and rotor resistances of the induction motor for speed sensorless indirect vector controlled drives, using artificial neural networks. The error between the rotor flux linkages based on a neural network model and a voltage model is back propagated to adjust the weights of the neural network model for the rotor resistance estimation. For the stator resistance estimation, the error between the measured stator current and the estimated stator current using neural network is back propagated to adjust the weights of the neural network. The rotor speed is synthesized from the induction motor state equations. The performance of the stator and rotor resistance estimators and torque and flux responses of the drive, together with these estimators, are investigated with the help of simulations for variations in the stator and rotor resistances from their nominal values. Both resistances are estimated experimentally, using the proposed neural network in a vector controlled induction motor drive. Data on tracking performances of these estimators are presented. With this speed sensorless approach, the rotor resistance estimation was made insensitive to the stator resistance variations both in simulation and experiment. The accuracy of the estimated speed achieved experimentally, without the speed sensor clearly demonstrates the reliable and high-performance operation of the drive     

Advanced simulation model for IPM motor drive with considering phase voltage and stator inductance

This paper proposes an advanced simulation model of driving system for Interior Permanent Magnet (IPM) BrushLess Direct Current (BLDC) motors driven by 120-degree conduction method (two-phase conduction method, TPCM) that is widely used for sensorless control of BLDC motors. BLDC motors can be classified as SPM (Surface mounted Permanent Magnet) and IPM motors. Simulation model of driving system with SPM motors is simple due to the constant stator inductance regardless of the rotor position. Simulation models of SPM motor driving system have been proposed in many researches. On the other hand, simulation models for IPM driving system by graphic-based simulation tool such as Matlab/Simulink have not been proposed. Simulation study about driving system of IPMs with TPCM is complex because stator inductances of IPM vary with the rotor position, as permanent magnets are embedded in the rotor. To develop sensorless scheme or improve control performance, development of control algorithm through simulation study is essential, and the simulation model that accurately reflects the characteristic of IPM is required. Therefore, this paper presents the advanced simulation model of IPM driving system, which takes into account the unique characteristic of IPM due to the position-dependent inductances. The validity of the proposed simulation model is validated by comparison to experimental and simulation results using IPM with TPCM control scheme.     

A prototype magnetically levitated stepping motor using highTc bulk superconductors

A magnetically levitated stepping motor using high T_c superconductors has been newly developed. The levitated stepping motor consists of a cylindrical rotor with superconductors and a stator with eight electromagnets. The rotor measures 10 mm in diameter, 46 mm in length, and 18 g in mass. The superconductors of the rotor are field-cooled in liquid nitrogen. The levitated rotor is driven by an eight-phase excitation. The rotor spins as the excitation phases of the electromagnets shift one by one. The rotation angle by each step is 45°. The experimental result shows that the rotor speed is limited to about 400 rpm by axial displacements. During the rotation, the radial displacement of the rotor is less than 0.4 mm. Magnetic flux density in the superconductors is studied before and after continuous rotations. These show that there is a possibility that the levitated stepping motor will be realized     

Modeling and control of a new horizontal-shaft hybrid-type magneticbearing

This paper reports on the development of a new horizontal-shaft hybrid-type magnetic bearing system. The bearing system will be used for a horizontal-shaft machine. The rotor is levitated due to the repulsive force between a stator and a rotor permanent magnet (PM). A lower cost and higher radial stiffness have been achieved by using a strontium-ferrite magnet on the rotor and an Nd-Fe-B PM above and below the rotor magnet. A finite-element analysis was performed to calculate the levitation force and radial stiffness. An upper stator magnet subtending an angle of 45° provides the best compromise between a large levitation force and radial stiffness. A model for the horizontal-shaft hybrid magnetic bearing system has been developed and includes the effect of the rotor dynamics and the electromagnetic forces. An integral servocontroller was designed to stabilize the axial position. The controller has been implemented in a digital signal processor. Experimental results performed on a prototype system are in agreement with the theoretical results     

A sensorless initial rotor position estimation scheme for a direct torque controlled interior permanent magnet synchronous motor drive

In direct torque control (DTC) scheme, the requirement of the continuous rotor position sensor and coordinate transformation is eliminated since all the calculation is done in stator reference frame. However, the DTC scheme requires the position sensor to determine the initial position of the rotor at starting. Elimination of the shaft-mounted position encoder is a very desirable objective in many applications since this sensor is often one of the most expensive and fragile components in the entire drive system. This paper presents a sensorless method of determining the initial rotor position of a direct torque controlled interior permanent magnet (IPM) synchronous motor drive. The method consists of injecting a high frequency voltage to the windings and examining the effects of the saliency on the amplitude of the corresponding stator current components. This method does not depend on the level of static load and on any motor parameters. The magnet polarity of the rotor at its initial position is also identified using the effect of saliency. Modeling and experimental results verify the effectiveness of the proposed method.     

Unified sensorless vector control of synchronous and induction motors

In this paper, a unified theory for sensorless flux estimation and vector control of induction motors and nonsalient permanent-magnet synchronous motors (PMSMs) is developed. It is shown that an estimator and vector controller for one of the motor types can also be applied to the other, with only minor modifications necessary. Two candidate estimators are considered: a variant of the well-known "voltage model" (VM) and a phase-locked-loop-type speed and position estimator. These are applied to both motor types, and evaluated experimentally. For the nonsalient PMSM, an important result is that synchronization can be guaranteed from any initial rotor position.     

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.     

行波型超声波电机等效电路建模

该文在深入分析超声电机运行机理的基础上,从定子、接触区域和转子3方面建立了超声电机等效电路模型。综合现有超声电机等效电路模型的优缺点,考虑摩擦耦合对超声电机的影响,并结合转子振动方程,提出了摩擦层与转子的等效电路模型;对转子侧等效模型进行优化,使其与定子模型结合成完整的电机模型。基于所建立的模型理论,对等效电路进行仿真,仿真结果表明了转子对整个电机电气特征的影响。通过对实际超声电机的测试及其与仿真波形的对比,验证了所提出的行波型超声波电机等效电路模型的正确性,为进一步开展超声电机驱动器和控制器的设计提供了模型基础。