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The structures of Sm8.3Fe85.2B2.0Ti4.5 and Sm9.4Fe84.1B2.0Ti4.5 alloys, which show superior properties as isotropic permanent magnets after a hydrogenation–disproportionation–desorption–recombination (HDDR) process followed by a nitridation, have been investigated by transmission electron microscopy, and electron and X-ray diffraction, paying particular attention to the structural changes induced by the HDDR process. It is found that a hexagonal Th2Ni17-type structure, observed in both alloys, with an approximate composition Sm(Fe,Ti)9.5 before the HDDR process, transforms to a rhombohedral Th2Zn17-type structure with a composition Sm(Fe,Ti)8.5 after the HDDR process. The Ti content in the hexagonal Th2Ni17-type structure is higher than that in the rhombohedral structure. The hexagonal Th2Ni17-type and rhombohedral Th2Zn17-type structures in the Sm9.4Fe84.1B2.0Ti4.5 alloy have lattice parameters a=0.85103(3) nm and c=0.83820(5) nm, and a=0.85549(3) nm and c=1.24826(9) nm, respectively, and show the relationship ahex 1/3crhomb.

Quantitative measurements of the (00 · 2) pole density distribution (PDD) of hexagonal CoCrTa alloy thin films on different kinds of substrates under different sputtering conditions have been performed using the X-ray diffraction method. The sputtering conditions, e.g. the ultimate vacuum pressure, and the kind of substrate, influence the preferred orientation (PO) of the Cr underlayer and the (00 · 2) PDD of CoCrTa. It is also proposed that to form films with a high coercive force, the suppression of the normal component of (00 · 2) PDD is important.

A scheme for the speed control of rolling mill drives is presented. The proposed speed controller is based on a two degree of freedom (TDF) structure and uses an observer-based state feedback compensator for the major control loop. The control method yields a robust system with respect to system uncertainties and modeling errors and is very effective for vibration suppression. Experimental verification is carried out on a prototype rolling mill mini-model system. The experimental drive system has a three-mass-model structure (motor-gear-load) connected by low stiffness shafts. The mechanical resonances and the inertia ratios between the motor, gear, and load are comparable to those of an actual rolling mill system (resonant frequencies are at 17.4 Hz and 51.32 Hz). The proposed scheme is compared to the conventional proportional plus integral controller, and the performance of each scheme is presented. A high closed loop speed bandwidth was obtained with the proposed TDF speed controller. >

This paper proposes a fast and robust speed controller for electric motor drive systems having torsional loads and containing a gear backlash. The controller is designed using the state feedback technique combined with state variable observers and is implemented on a digital signal processor. Analysis, simulation and experimental results of a prototype variable speed drive system are presented and discussed. It is shown that the proposed speed controller yields a robust system with respect to system uncertainties and modeling errors and is very effective for the suppression of mechanical vibrations. >

The authors describe the control problems associated with rolling mill drive systems and propose a robust speed controller for the suppression of the torsional vibrations. The undesirable mechanical vibrations inherent in a rolling mill drive system impose severe limitations on the dynamic performance of the speed control loop. Plant parameter variations uncertain dynamics, and load torque disturbances are among the major factors which must be addressed to guarantee the system stability and the high-performance operation of the system. To solve these problems, a robust speed controller based on a state feedback control structure is developed. The control law is derived using the loop transfer recovery design methodology, where plant and disturbance uncertainties are incorporated in the design to achieve a robust speed control loop. The design steps of the state controller and the state observer are described, and the constraints imposed on the system are discussed. Analysis and simulation results of the total speed drive system are presented. >