A control systems engineering approach, employing a two-level overall system architecture and different but compatible formalisms for system representation on the upper and lower levels, has been investigated in detai...
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This paper extends some of the basic results in the area of Lyapunov (asymptotic) and finite time and practical stability to linear, discrete, time invariant time-delay systems, New definitions have been established f...
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The high practical significance of the I 1 T d -plant approximations has been shown by the perhaps most frequently used method for controller tuning by (Ziegler and Nichols, 1942), modified later for sampled data syst...
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The high practical significance of the I 1 T d -plant approximations has been shown by the perhaps most frequently used method for controller tuning by (Ziegler and Nichols, 1942), modified later for sampled data systems by (Takahashi et al ., 1971) and by many other authors. This paper extends previous works by developing plant approximations based on the single and double integrator models with dead time. These approximations are then used for tuning of the minimum time pole assignment P- (PD-) controllers designed for single (double) integrator with constrained input.
The aim of this paper is to present a new method for the nonlinear controller design. The underlying theory evolves from the introduced transfer function of nonlinear systems, that can be used in similar way as transf...
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The aim of this paper is to present a new method for the nonlinear controller design. The underlying theory evolves from the introduced transfer function of nonlinear systems, that can be used in similar way as transfer functions of classical linear systems. The presented algebra of transfer functions is the same as the linear one. Therefore, the controller design can follow the linear system synthesis. The paper shows, how to design a nonlinear PID controller using the direct method synthesis and also shows that the nonlinear state controller following the pole-placement method is equivalent to the exact linearization method. Since the presented method leads to results identical with the exact linearization method, it has been denoted as the exact velocity linearization method.
Disturbance rejection performance is usually the most important aspect in designing controller in the process and the chemical industries. On the other hand, such tuned control loop may exhibit large overshoots on ref...
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Disturbance rejection performance is usually the most important aspect in designing controller in the process and the chemical industries. On the other hand, such tuned control loop may exhibit large overshoots on reference tracking. The only way to decrease overshoot is to use two-degrees-of-freedom (2-DOF) controllers. Unfortunately, reducing the overshoot usually results in slower tracking response when using some of the most common 2-DOF controller structures. This paper suggests using additional first-order filter on the set-point of the PI controller in order to improve tracking performance. The calculation of compensator's parameters is straightforward and can be easily performed in practice. Several examples confirmed the efficiency of the proposed approach.
In this paper a non-linear fuzzy autopilot for ship track-keeping is presented. The proposed autopilot has four inputs (actual and desired heading, rate of change of heading and offset from the desired path) and one o...
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In this paper a non-linear fuzzy autopilot for ship track-keeping is presented. The proposed autopilot has four inputs (actual and desired heading, rate of change of heading and offset from the desired path) and one output (command rudder angle). The track-keeping problem is decomposed into two subtasks: (i) followthe desired heading, and (ii) bring the ship onto the desired path and keep tracking. Internally, the autopilot consists of two autopilots that fulfil these tasks simultaneously. The proposed control scheme has been verified using a non-linear model of a Mariner-class vessel and steering mechanism under the influence of wave and current disturbances. Results presented show how such a control strategy enables improved tracking performance.
Traditional approaches to controller designs that guarantee fast compensation of load torque and reference variations result in design iterations and most of the time in poorer response for load torque variations. In ...
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Traditional approaches to controller designs that guarantee fast compensation of load torque and reference variations result in design iterations and most of the time in poorer response for load torque variations. In this paper a reference model for desired drive behavior generation and optimization methods has been applied to achieve controller integral time constant lower than the maximum time constant of the PM brushless DC motor drive. Presented simulation results show that using reference model for desired drive behavior generation, it is possible to determine optimal controller parameters for faster (10 time) and better (2 time) load torque compensation than in the case of traditional design of speed controller parameters. Response due to reference input with constrained overshoot has been achieved using a filter in the servosystem input. Thereby, the proposed method demonstrates the design of a speed controller that is optimal for both load torque and reference variations and its verification with simulation are accomplished for a permanent magnet brushless dc motor drive.
This paper extends some of the basic results in the area of Lyapunov (asymptotic) and finite time and practical stability to linear, discrete, time invariant time-delay systems. New definitions have been established f...
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This paper extends some of the basic results in the area of Lyapunov (asymptotic) and finite time and practical stability to linear, discrete, time invariant time-delay systems. New definitions have been established for the latter concept of stability. Sufficient conditions for this type of stability, concerning the particular class of linear discrete time-delay systems are derived. More over the generalization of some previous results, in the area of Lyapunov stability for the same class of systems has been also established and proved.
Driven by the demand on more flexibility in manufacturing and process automation systems. investigations are made in the field of wireless communication. In the R-FlELDBUS project a new wireless physical layer type wa...
Driven by the demand on more flexibility in manufacturing and process automation systems. investigations are made in the field of wireless communication. In the R-FlELDBUS project a new wireless physical layer type was added to an existing fieldbus system. The resulting R-FIELDBUS systems allow adaptive architectures with mixed wired and wireless segments. To be able to analyse the functional and time behaviour of different configurations, a simulation model of the fieldbus system was also extended by the wireless behaviour. This paper describes the used simulation method. the models of the communication protocol as well as the new added wireless medium type as well as providing some first simulation results.
Si(100)4×3−In reconstruction is essentially a superlattice of magic (identical-size) Si7In6 nanoclusters. Using scanning tunneling microscopy (STM) observations, we have found that under appropriate growth condit...
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Si(100)4×3−In reconstruction is essentially a superlattice of magic (identical-size) Si7In6 nanoclusters. Using scanning tunneling microscopy (STM) observations, we have found that under appropriate growth conditions up to 35% of these clusters can be modified; namely, two Si atoms in the cluster can be replaced by two In atoms, thus forming a Si5In8 cluster. This modification can be considered as a doping of the magic cluster, as it changes the electronic properties of the cluster from semiconducting towards metallic. The doped cluster is less rigid than the ordinary one and swings in the electrical field of the STM tip. The atomic structure and stability of the doped magic cluster have been examined using first-principles total-energy calculations.
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