Marian J. Blachuta

On zeros of pulse transfer functions

The famous /spl Aring/strom-Hagander-Sternby theorem (1984) on limiting zeros of the pulse transfer function is extended by determining the accuracy of the asymptotic results for both the discretization and the intrinsic zeros when the sampling interval is small. Closed form formulas are derived that express the degree of the principal term of Taylor expansion of the difference between the true zeros and asymptotic ones as a function of the relative degree of the underlying continuous-time system and the value of the corresponding coefficient itself. Certain known results on asymptotic zeros are shown to be particular cases of the result presented.

On zeros of sampled systems

The Astrom-Hagander-Sternby theorem (1984) on asymptotic zeros of the pulse transfer function is extended by determining the accuracy of the asymptotic results for both the sampling and the intrinsic zeros when the sampling interval is small. Closed form formulae are derived that express the degree of the principal term of Taylor expansion of the difference between the true zeros and asymptotic ones as a function of the relative degree of the underlying continuous-time system, and the value of the corresponding coefficient itself. The results are illustrated by an example.

DESIGN OF ANALOG AND DIGITAL AIRCRAFT FLIGHT CONTROLLERS BASED ON DYNAMIC CONTRACTION METHOD

In the paper the feasibility of the Dynamic Contraction Method for the design of the aircraft motion analog and digital controllers is studied. The control task is formulated as a tracing problem for Euler angles, where decoupled output transients are accomplished in spite of incomplete information about varying parameters of the system and external disturbances. A resulting output feedback continuous-time controller has a simple form of a combination of three low-order linear dynamical systems and a matrix whose entries depend nonlinearly on certain known process variables. The resulting continuous-time controller is then digitally redesigned. The pseudo - continuous - time model of a control loop with a pure time delay is used to calculate parameters of a digital controller.

Antidepressant- and Anxiolytic-Like Effects of New Dual 5-HT1A and 5-HT7 Antagonists in Animal Models

The aim of this study was to further characterize pharmacological properties of two phenylpiperazine derivatives: 1-{2-[2-(2,6-dimethlphenoxy)ethoxy]ethyl}-4-(2-methoxyphenyl)piperazynine hydrochloride (HBK-14) and 2-[2-(2-chloro-6-methylphenoxy)ethoxy]ethyl-4-(2- methoxyphenyl)piperazynine dihydrochloride (HBK-15) in radioligand binding and functional in vitro assays as well as in vivo models. Antidepressant-like properties were investigated in the forced swim test (FST) in mice and rats. Anxiolytic-like activity was evaluated in the four-plate test in mice and elevated plus maze test (EPM) in rats. Imipramine and escitalopram were used as reference drugs in the FST, and diazepam was used as a standard anxiolytic drug in animal models of anxiety. Our results indicate that HBK-14 and HBK-15 possess high or moderate affinity for serotonergic 5-HT2, adrenergic α1, and dopaminergic D2 receptors as well as being full 5-HT1A and 5-HT7 receptor antagonists. We also present their potent antidepressant-like activity (HBK-14—FST mice: 2.5 and 5 mg/kg; FST rats: 5 mg/kg) and (HBK-15—FST mice: 1.25, 2.5 and 5 mg/kg; FST rats: 1.25 and 2.5 mg/kg). We show that HBK-14 (four-plate test: 2.5 and 5 mg/kg; EPM: 2.5 mg/kg) and HBK-15 (four-plate test: 2.5 and 5 mg/kg; EPM: 5 mg/kg) possess anxiolytic-like properties. Among the two, HBK-15 has stronger antidepressant-like properties, and HBK-14 displays greater anxiolytic-like activity. Lastly, we demonstrate the involvement of serotonergic system, particularly 5-HT1A receptor, in the antidepressant- and anxiolytic-like actions of investigated compounds.

Data Fusion Algorithm for the Altitude and Vertical Speed Estimation of the VTOL Platform

An approach to the autonomous of the realization VTOL platform take-off and landing significantly simplifies the operator labor to control such device. At the same time, implementation of these control scenarios allows to perform these tasks under failure conditions (for example communication breakdowns). One condition of proper operation of the vertical movement control system is the ability to provide reliable information about the altitude of the controlled platform. In this paper one of the solutions for obtaining estimate of the altitude based on sensor data fusion is presented. Proposed scheme uses information obtained from pressure sensor, inertial measurement unit, ultrasonic sensor and GPS, all of these instruments are nowadays very often mounted on VTOL platforms.

On approximate pulse transfer functions

A systematic approach to a class of approximations to the pulse transfer function of a system consisting of a zero-order hold and a linear continuous-time plant is presented. It is based on the asymptotic result of Astrom, Hagander, and Sternby (1984) on zeros of sampled systems at high sampling rates, and on the bilinear transformation. Since the number of intrinsic parameters does not change in the discretization process, model matching control, robust control, and identification are suggested as possible areas of application. Superiority of the approximations considered over a /spl delta/-operator based truncated approximation is shown. The results are illustrated by an example.

Modeling and identification of electric propulsion system for multirotor unmanned aerial vehicle design

The propulsion system plays a key role in each unmanned aerial vehicle. Considering different multirotor platforms we may observe that mostly the dynamics and performance of the particular vehicle is strictly depended on the drive unit. In this paper we focus on the problem of modeling and identification of the propulsion system consisting of an electronic speed controller, electric brushless direct current motor and propeller. We propose a multiple-input and multiple-output nonlinear model of the propulsion unit based on the block oriented modeling with the static nonlinearities at the input and linear dynamical part at the output. Such model enhanced with the aerodynamics theory of a propeller should be suitable and detailed enough to provide the simulation, control algorithms prototyping and solution verification under the circumstances of designing the vertical take-off and landing unmanned platform.

On fast sampling zeros of systems with fractional-order hold

The aim of the paper is to extend the methodology of Blachuta, (1998, 1999) applied there to systems with ZOH and FOH to systems with FROH in order to determine the accuracy of the limiting formulas of both the intrinsic and discretization zeros at high sampling rates. The results can be applied to investigate the accuracy of certain approximate pulse transfer functions based on limiting zeros or their Pade approximation as it was done in Blachuta (1999).

Dynamics and Optimal Control of Quadrotor Platform

This article is devoted to development of a mathematical model of quadrotor and its applications in the control system of such platform. It shows consecutive steps in developing the equations constituting the model. Various aerodynamic phenomena, such as Vortex Ring State or blade flapping are mentioned and taken into account. The assumptions and reasoning behind are discussed. The structure of a control system is presented. Justification of optimal LQ regulator is made. Simulation tests of control system performance are conducted. Simple way of creating flight trajectories is shown. The conclusions are stated about the level of insight necessary in the creation of a control-oriented and useable model of quadrotor platform.

Are anti-aliasing filters really necessary for sampled-data control?

In the paper the role of anti-aliasing filters is revised based on control quality assessment of various setups of analog filters used prior to sampling, or their lack. Numerical results show that contrary to common belief possible benefits gained from anti-aliasing filters are very restricted.