An induction motor is basically a nonlinear system having three inputs three outputs and in this paper, first, we show that an induction motor can be exactly linearized and decoupled. However, there is the problem that this general exact linearization system is sensitive for parameter variation. So we cope with this problem by using information that is included in approximated linearization system around an equilibrium point. Second, we design an H∞ controller in consideration of parameter variations for exact linearization system. We verify the validity of our proposed design method with respect to both nonlinearity and parameter variation by simulations.
A motorized wheelchair has rear wheels driven by DC motors, and its speed and direction can be maneuvered by adjusting the motor speed. Because its front wheels are in the form of casters, the direction is easily changed by circumstances. This paper presents a study of modeling of motorized wheelchairs. In this paper, we propose on improved model of its body and front wheel dynamics for the smooth and stable control. We examined suitability of this model by digital simulations.
In this paper we propose a new two-dimensional (2-D) spectral estimation method which has high-resolution property even in the case where the measured 2-D data is of short length and at low signal-to-noise ratio. The method combines the iterative filtering method, addressed by the authors, with a data extrapolation technique. The power spectrum is estimated by 2-D periodogram after the data extension based on Burg's AR spectral analysis. The iterative prefiltering reduces noise components embedded in the data, making the following data extrapolation accurate. As a result, we can obtain high-resolution spectral estimates from the extended data. Computational complexty of the method is moderate, because the iterative prefiltering is basically calculated by 2-D FFT algorithm, and the data extrapolation is done based on 1-D Burg's order-update algorithm. Computer simulations show the effectiveness of the method.
Dynamic tracking systems for video tape recorders use a moving-coil head actuator to control the head displacement with respect to the signal on the track. The head is liable to fluctuate at the mechanical resonant frequency. A voltage feedback amplifier is known to effectively reduce the Q factor of the moving-coil's resonance. However, the voltage-displacement gain depends on the coil's resistance, and that resistance is a function of temperature. On the other hand, a current feedback amplifier does not reduce the Q factor, and the gain does not vary with the coil's resistance. In order to obtain fine tracking, both the Q factor and the gain variations need to be reduced. Consequently, a drive circuit having current feedback around the fundamental drive frequency and voltage feedback around the resonant frequency is indicated, and investigated. The experimental results confirm that the Q factor and gain variations have both been reduced.