Frequency-domain Optimization Technique Research Articles

Boundary control of partial differential equations using frequency domain optimization techniques

We present a frequency domain based H∞-control strategy to solve boundary control problems for systems governed by parabolic or hyperbolic partial differential equation, where controllers are constrained to be physically implementable and of simple structure suited for practical applications. The efficiency of our technique is demonstrated by controlling a reaction–diffusion equation with input delay, and a wave equation with boundary anti-damping.

Wideband RF Self-Interference Cancellation Circuit for Phased Array Simultaneous Transmit and Receive Systems

With the growing demand for spectrum utilization, the concept of full duplex transceivers has become attractive. These simultaneous transmit and receive systems (STAR) are attractive as they double bandwidth utilization. To realize STAR, we must suppress self-interference (SI) between transmit and receive antennas. Doing this across a wide bandwidth presents an even greater challenge. Further, for antenna arrays, SI can be higher due to mutual coupling among neighboring elements. In this paper, we achieve 100 dB isolation for practical STAR, across a large 500 MHz bandwidth. Specifically, four stages of the self-interference cancellation are proposed. In addition to high isolation cross-polarized array elements, we employ multi-tap filters at the transceiver RF front-end for interference cancellation. These filters emulate direct SI coupling using frequency-domain optimization techniques. Measured results show an average of 25 dB filter cancellation is possible across 500 MHz.

Optimal controller design for a matrix converter based surface mounted PMSM drive system

This paper proposes a new control algorithm for a matrix converter permanent magnet synchronous motor (PMSM) drive system. First, a new switching strategy, which applies a backpropagation neural network to adjust a pseudo DC bus voltage, is proposed to reduce the current harmonics of the permanent magnet synchronous motor. Next, a two-degree-of-freedom controller is proposed to improve the system performance. The parameters of this controller are obtained by using a frequency-domain optimization technique. The controller design algorithm can be applied in an adjustable speed control system and a position control system to obtain good transient responses and good load disturbance rejection abilities. The controller design procedures require only algebraic computation. The implementation of this kind of controller is only possible by using a high-speed digital signal processor. In this paper, all the control loops, including current-loop, speed-loop, and position-loop, are implemented by a 32-b TMS320C40 digital signal processor. The hardware, therefore, is very simple. Several experimental results are shown to validate the theoretical analysis.

A novel two-degree-of-freedom controller design for a permanent magnet linear synchronous motor control system

This paper proposes a novel two-degree-of-freedom optimal controller design for a permanent magnet linear synchronous motor position-control system. The param-eters of the controller are obtained by using a frequency-domain optimization technique. A systematic design of the controller and the detailed implementation of the proposed system are discussed. The closed-loop control system possesses good transient responses and good load disturbance responses. In addition, the system has a good tracking ability. Several experimental results are provided to validate the theoretical analysis.

A novel two-degree-of-freedom controller design for a permanent magnet linear synchronous motor control system

This paper proposes a novel two-degree-of-freedom optimal controller design for a permanent magnet linear synchronous motor position-control system. The parameters of the controller are obtained by using a frequency-domain optimization technique. The systematic design of the controller and the detailed implementation of the proposed system are discussed. The closed-loop control system exhibits good transient responses and good load disturbance responses. In addition, the system has a good tracking ability. Several experimental results are provided to validate the theoretical analysis.

White noise approach for estimating the passive electrical properties of neurons.

1. The passive electrical properties of whole cell patched dentate granule cells were studied with the use of zero-mean Gaussian white noise current stimuli. Transmembrane voltage responses were used to compute the first-order Wiener kernels describing the current-voltage relationship at the soma for six cells. Frequency domain optimization techniques using a gradient method for function minimization were then employed to identify the optimal electrical parameter values. Low-power white noise stimuli are presented as a favorable alternative to the use of short-pulse current inputs for investigating neuronal passive electrical properties. 2. The optimization results demonstrated that the lumped resistive and capacitive properties of the recording electrode must be included in the analytic input impedance expression to optimally fit the measured cellular responses. The addition of the electrode resistance (Re) and capacitance (Ce) to the original parameters (somatic conductance, somatic capacitance, axial resistance, dendritic conductance, and dendritic capacitance) results in a seven-parameter model. The mean Ce value from the six cells was 5.4 +/- 0.3 (SE) pF, whereas Re following formation of the patch was found to be 20 +/- 2 M omega. 3. The six dentate granule cells were found to have an input resistance of 600 +/- 20 M omega and a dendritic to somatic conductance ratio of 6.3 +/- 1.1. The electronic length of the equivalent dendritic cylinder was found to be 0.42 +/- 0.03. The membrane time constant in the soma was found to be 13 +/- 3 ms, whereas the membrane time constant of the dendrites was 58 +/- 5 ms. Incorporation of morphological estimations led to the following distributed electrical parameters: somatic membrane resistance = 25 +/- 4 k omega cm2, somatic membrane capacitance = 0.48 +/- 0.05 microF/cm2, Ri (input resistance) = 72 +/- 5 omega cm, dendritic membrane resistance = 59 +/- 4 k omega cm2, and dendritic membrane capacitance = 0.97 +/- 0.06 microF/cm2. On the basis of capacitive measurements, the ratio of dendritic surface area to somatic surface area was found to be 34 +/- 2. 4. For comparative purposes, hyperpolarizing short pulses were also injected into each cell. The short-pulse input impedance measurements were found to underestimate the input resistance of the cell and to overestimate both the somatic conductance and the membrane time constants relative to the white noise input impedance measurements.

Implementation of AC servo controllers employing frequency-domain optimization techniques

The design and implementation of a permanent magnet synchronous motor drive based on H/sub 2/ and H/sub infinity / optimal control theory are presented. A mathematical model of the drive is introduced. Based on appropriate assumptions, the model is reduced to a second-order, linear time-invariant system so that the H/sub 2/ and H/sub infinity / optimization techniques are applicable. H/sub 2/ and H/sub infinity / controllers are derived on the basis of the simplified model. A stability analysis is conducted, and stability regions based on controller tuning parameters and sampling periods are constructed. The relationship between closed-loop bandwidth and sampling period due to discretization effect is investigated. Implementation of the controllers and experimental results are described. A multiprocessor-based, fully digital control system is used to realize and experimentally verify the H/sub 2/ and H/sub infinity / control algorithms. Controller performance is evaluated in terms of speed and position responses, and closed-loop and sensitivity frequency responses.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Computer-aided discretization and simplification of continuous control systems

An iterative method for discretization and model reduction of continuous control systems is presented in this paper. The proposed method utilizes a frequency-domain optimization technique to find the optimal simplified z-transfer functions for a given higher order s-transfer function. The optimum values for the parameters of the prespecified reduced order discrete model are obtained as a result of minimizing the sum of magnitude-squared error function. Examples are considered to illustrate the application of this method, compared to other methods, in system identification, discretization, and model reduction, for both small and large sampling rates.