Haiwei Lu

A Miniature Short Stroke Linear Actuator—Design and Analysis

We report a newly developed miniature short stroke tubular linear permanent-magnet actuator for robotic applications. Compared to a rotary-to-linear mechanism, the linear actuator has the advantages of efficiency, thrust control, and compact size in generating linear motion. We optimized the electromagnetic force of the actuator analytically by selecting appropriate dimensions and then predicted the force produced by the winding currents by the finite-element method under the brushless dc excitation scheme. We analyzed the actuation performance by dynamic modeling of the actuator. We constructed and tested a prototype on a specially designed test bench to verify the design. Finally, we analyzed and measured the end effect on the magnetic force due to the limited length of the stator core and translator.

Modeling and Simulation of Direct Torque Controlled PMSM Drive System Incorporating Structural and Saturation Saliencies

The direct torque controlled (DTC) permanent magnet synchronous motor (PMSM) drive has become competitive compared with other types of drive systems because of its simple and sensorless control algorithm. The application of the system, however, is handicapped by the difficulty of starting under full load due to the unknown initial rotor position. This paper presents a nonlinear model of PMSMs which incorporates both the structural and saturation saliencies to enable the numerical simulation of initial rotor position detection algorithms. In this model, the phase inductances are expressed by Fourier series as functions of the stator current and rotor position. The inductances of a surface mounted PMSM is measured with different rotor positions and DC offset currents, which emulate the effect of the three phase stator currents. By using the proposed model, the DTC PMSM is simulated and the results are compared with those obtained by the PMSM model in the Simulink library. With the model, an initial rotor position estimation scheme using voltage pulses is investigated by numerical simulation. The scheme is also experimentally tested and the results are compared with the inductance variation to verify the validity of the method. The effectiveness of the scheme to estimate the initial rotor position for the testing SPMSM is analyzed and verified by numerical simulation before physical implementation

Vector characterization of soft magnetic materials

A three-dimensional (3D) magnetic property testing system has been completed and successfully used to measure 3D hysteresis loci of soft magnetic material. This paper presents the techniques to characterize soft magnetic materials under 3D magnetic excitations in detail. Using three couples of excitation coils controlled by a computer to generate the magnetic fields in three orthogonal axes, various types of flux density loci, such as circular or elliptical rotating vectors of flux density with any given orientations in 3D space, can be obtained. Based on 3D finite element analysis and a comparative study, a sandwich arrangement comprising a sample, guard pieces, and search coils with double-layer structure was proposed. Compared with the conventional surface search coils, this arrangement can significantly improve the accuracy of measurement. The comprehensive calibration process and the experimental results of the 3D hysteresis loci of soft magnetic composite materials are also presented.

A Permanent Magnet Linear Motor for Micro Robots

Linear micro motors play a key role in micro robotic systems. They can greatly simplify the drive mechanisms and this is crucial for micro systems. By using permanent magnets, much higher force-to-volume ratios can be acquired than using electromagnets and better drive performance can be obtained. This paper describes the development of a tubular permanent magnet linear motor for the actuation of micro robots. Important design criteria are established by analytical method and numerical method is applied to obtain detailed characteristics of the micro motor. The performances of the micro motor are analyzed and predicted by the finite element analysis and dynamic modeling. The derived motor model is implemented in SIMULINK and is capable of being extending to complex robotic applications. The simulation of the motor operation shows that the dynamic performance is quite satisfactory

A PMSM model incorporating structural and saturation saliencies

Sensorless permanent magnet synchronous motor (PMSM) drive systems have become very attractive due to their advantages, such as the reduction of hardware complexity and hence the reduced system cost and increased reliability. In order to accurately determine the rotor position required for correct electronic commutation, various methods have been proposed. Among them, the most versatile makes use of the structural and/or magnetic saturation saliencies of the PMSM. This paper presents a non-linear model for PMSMs with the saliencies. The phase inductances of a PMSM are measured and expressed by Fourier series at different rotor positions according to their patterns. The dynamic performance of the PMSM is simulated and compared with that based on a model without considering saliency to verify the effectiveness of the proposed model.

Study of A PMSM Model Incorporating Structural and Saturation Saliencies

Sensorless permanent magnet synchronous motor (PMSM) drive systems have become very attractive due to their advantages, such as reduction of hardware complexity and hence the system cost and increment of system reliability. In order to correctly obtain the rotor position information required for the appropriate control, various methods have been proposed. Among them, the most versatile method makes use of the structural and magnetic saturation saliencies of the PMSM. This paper presents a non-linear model of PMSMs considering the saliencies. The phase inductances of a PMSM are measured and expressed in Fourier series versus stator winding currents and rotor positions according to the inductance pattern. The simulated dynamic performance is compared with that based on a model without considering saliency to verify the effectiveness of the proposed PMSM model

Design of SMC motors using hybrid optimization techniques and 3D FEA with increasing accuracy

This paper presents the design and analysis of a three-phase three-stack permanent magnet claw pole motor with soft magnetic composite (SMC) stator core. 3D finite element analysis (FEA) of magnetic field is performed to accurately calculate key motor parameters and performance. Combined optimization techniques and 3D FEA with increasing accuracy are applied to effectively reduce the computational time. The designed motor has been fabricated and tested. The theoretical calculations are validated by the experimental results on the prototype.

Design and Analysis of a Permanent Magnet Claw Pole/Transverse Flux Motor with SMC Core

This paper presents the design and analysis of a claw pole/transverse flux motor (CPTFM) with soft magnetic composite (SMC) core and permanent magnet flux-concentrating rotor. Three-dimensional magnetic field finite element analysis is conducted to accurately calculate key motor parameters such as winding flux, back electromotive force, winding inductance, and core loss. Equivalent electric circuit is derived under optimum brushless DC control condition for motor performance prediction, and computer search techniques are applied for design optimization. All these computations and analyses have been implemented in a commercial software ANSYS for development of the SMC CPTFM prototype

A tubular linear motor for micro robotic applications

Linear micro motors play a key role in micro robotic systems. They can greatly simplify the drive mechanisms, which is crucial for micro systems. By using permanent magnets, much higher force-to-volume ratios can be acquired than using electromagnets and better drive performance can be obtained. This paper describes the development of a tubular permanent magnet linear motor for the actuation of micro robots. Important design criteria are established by both analytical and numerical methods. The performances of the micro motor as well as the entire actuation system are analyzed and predicted by the finite element analysis and kinetic modeling. The results show that the proposed linear motor has the quite satisfactory force capability and kinetic performance.

A study on characteristics of electromagnetic and piezoelectric micro actuators

Electromagnetic actuators are dominant in the macro field. Although there are several hindrances, electromagnetic actuators still have some advantages in the application of micro systems. Piezoelectric actuator is also an attractive drive principle for micro systems due to its large force and simple structure, but some drawbacks inevitably exist. This paper presents a comparative study of both drive principles and a better understanding of the basic performances and limitations of the both principles for the system design.