This paper proposes the mixed lì synthesis for active suspension problems. With this method, a robust compensator that achieves nominal performance and meets robust stability specifications can be designed. Moreo...
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In this paper PI and PID controllers augmented by a Smith predictor structure are compared to ordinary PI and PID controllers, for plants with medium and great time delays. The comparison is based an a systematic eval...
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In this paper PI and PID controllers augmented by a Smith predictor structure are compared to ordinary PI and PID controllers, for plants with medium and great time delays. The comparison is based an a systematic evaluation method, where both robustness and performance aspects in different frequency regions are taken into account. The results show that a Smith predictor increases performance somewhat for a PID controller when the time delay is moderate. For great time delays, however, the improvement is insignificant. An important remark is that it is necessary to include the predictor structure in the design to get acceptable robustness properties. For a PI controller the benefits from a predictor are mostly small or negligible independent of time delay. Most important is, however that a derivative part obviously will bring significantly greater improvement than a Smith predictor to a system with a PI controller. This result is somewhat surprising, since Smith predictors are normally used together with PI and not with PID controllers. Furthermore, it is sometimes argued that it is no use to include derivative action for plants with significant time delay.
This paper presents a software engineering process that includes family-based aspects for aero-engine control software. The process uses a "family capability" derived from family analysis of the embedding sy...
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A Robot vision system was designed using a silicon retina, which has been developed to mimick the parallel circuit structure of the vertebrate retina. The silicon retina used here is an analog CMOS very large-scale in...
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Repetitive processes are a distinct class of 2D systems of both practical and theoretical interest. Their essential characteristic is repeated sweeps, termed passes, through a set of dynamics defined over a finite dur...
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Repetitive processes are a distinct class of 2D systems of both practical and theoretical interest. Their essential characteristic is repeated sweeps, termed passes, through a set of dynamics defined over a finite duration with explicit interaction between the outputs, or pass profiles, produced as the process evolves. Experience has shown that these processes cannot be studied/controlled by direct application of existing theory (in all but a few very restrictive special cases). This fact, and the growing list of applications areas, has prompted an on-going research programme into the development of a `mature' systems theory for these processes for onward translation into reliable generally applicable controller design algorithms. It has long been considered that Volterra operator techniques should have a key role to play in this general area. In this paper, we first present the necessary properties of a Volterra operator representation for the very important sub-class of so-called discrete linear repetitive processes and then use them to develop a characterization of stability in this setting.
A reusable launch vehicle control problem during ascent and descent is addressed via multiple-time scaled continuous sliding mode control. The proposed sliding mode controller utilizes a two-loop structure and provide...
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A reusable launch vehicle control problem during ascent and descent is addressed via multiple-time scaled continuous sliding mode control. The proposed sliding mode controller utilizes a two-loop structure and provides robust decoupled tracking of both orientation angle command profiles and angular rate command profiles in the presence of bounded external disturbances and plant uncertainties, including aerodynamic surfaces and engine failures. Sliding mode control causes the angular rate and orientation angle tracking error dynamics to be constrained to linear, decoupled, homogeneous, and vector valued differential equations with desired eigenvalues. The dual-time scale sliding mode controller was designed for the X-33 technology demonstration sub-orbital launch vehicle in the ascent and descent modes. Simulation results show that the designed controller provides robust, accurate, decoupled tracking of the orientation angle command profiles in ascent and descent in presence of external disturbances and vehicle inertia uncertainties. The designed robust controller is to significantly reduce the time and cost associated with flying to new orbits, with new payloads, and with modified vehicles.
In the paper,we exhibit the usefulness of nonlinearity in two aspects:analysis of nonlinear dynamics and nonsmooth feedback *** illustrative examples are given to show how the new bifurcation p
In the paper,we exhibit the usefulness of nonlinearity in two aspects:analysis of nonlinear dynamics and nonsmooth feedback *** illustrative examples are given to show how the new bifurcation p
This paper weighs up the pros and cons of three different tracking controllers for a pneumatic muscle actuator: robust backstepping, adaptive backstepping and sliding-mode. Robustness is assured for three controllers ...
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This paper weighs up the pros and cons of three different tracking controllers for a pneumatic muscle actuator: robust backstepping, adaptive backstepping and sliding-mode. Robustness is assured for three controllers in the presence of model uncertainties and external perturbations. Ultimate boundedness is proved for the robust and adaptive backstepping tracking controller. Exponential stability is proved for the sliding-mode tracking controller. The tracking is well achieved by the sliding-mode and the adaptive controller. On the contrary, the robust backstepping shows a noticeable tracking error. The sliding-mode leads to a high-frequency switching control law.
We present a methodology using Kessler's formula that potentially improves the system order reduction techniques based on system balancing. The formula is simple and easy to use. We show how to refine the balancin...
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We present a methodology using Kessler's formula that potentially improves the system order reduction techniques based on system balancing. The formula is simple and easy to use. We show how to refine the balancing order reduction techniques for single-input single-output systems by using Kessler's formula that produces the equivalent time constant of the neglected part of the system. Using Kessler's formula all the neglected stable system time constants, either fast or slow, can be approximated by only one time constant, which preserves valuable information about the neglected part of the system. The balancing truncation and residualization techniques can be improved by adding in parallel a first order equivalent fast system that approximates the neglected fast dynamics, and the reversed residualization techniques can be improved by adding in parallel a first-order slow system that approximates the neglected slow subsystem.
This paper characterizes the integrated gate commutated thyristor (IGCT) device under the zero-current-transition (ZCT) soft switching condition for the first time. The test results show that ZCT soft switching can dr...
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This paper characterizes the integrated gate commutated thyristor (IGCT) device under the zero-current-transition (ZCT) soft switching condition for the first time. The test results show that ZCT soft switching can dramatically reduce the turn-off loss, turn-on loss of the IGCT switch and also alleviate the reverse recovery stress of the diode. The ZCT circuit is therefore suitable for increasing the current handling capabilities of IGCT devices.
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