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[en] In Sliding Mode Control (SMC), the control action can be split into two regions- the reaching phase and the sliding phase. Considerable research attention has been given to improve the reaching time so as to best utilize the benefit of robustness property of sliding mode motion. Attention has also been on alleviating and/or eliminating chattering during sliding mode motion so that smooth control is obtained which will not hinder practical applications. Exponential Reaching Law (ERL) is one of the methods reported in the literature for alleviating chattering in sliding mode. This paper proposes a Power Rate Exponential Reaching Law (PRERL) whereby substantial improvement both in reaching time and chattering alleviation are achieved compared to ERL. With ERL, the states do not settle at its desired position due to high frequency low magnitude chattering, thus limiting its practical utility. This drawback has been overcome in the PRERL method. Thus the benefits of the proposed method is many fold: reducing reaching time, improving chattering alleviation and ensuring settling of the states at its final position with considerable improvement in speed of response.
[en] Directional couplers for transverse electric (TE) modes are described which selectively pick one mode from a mode mixture in an overmoded circular waveguide system. Unwanted modes are statistically nulled out in the coupling waveguide. Mode selectivity and directivity oscillate up and down with an increasing number of holes and finally reach approximately the 20 dB mark. A directional coupler for the TE02 mode (28 GHz, 63.4 mm circular waveguide) with 41 holes and a length of 1.6 m shows a directivity of 68 dB and suppresses TE01 with 58 dB, TE03 with 28 dB, TE04 with 34 dB, TE22 with 37 dB, and further modes TEsub(lm)(l<5, m<6) with 17 dB to 34 dB. (orig.)
[en] Short mode selective directional couplers for transverse electric (TE) modes travelling in overmoded circular waveguides are described. Directivity is achieved by pairs of holes with destructive interference in backward direction, unwanted modes are suppressed by destructive interference in either directions of the coupling guide. A 28 GHz narrow directional coupler for the TE01 mode (63.4 mm waveguide diameter) with 16 holes and a length of 230 mm shows a directivity of 55 to 100 dB between 27.9 and 28.1 GHz, suppressing the TE02 mode with 35 to 80 dB, the TE03 mode with 30 to 65 dB, and the TE22 mode with 30 to 70 dB. (orig.)
[en] Multihole couplers showing insufficient suppression of single modes or insufficient directivity can be improved by adding holes of a shifted coupler structure of the same kind. A shifted structure improving the directivity also enhances suppression of unwanted modes propagating in backward direction. On the other hand marked suppression of a single unwanted backward mode also improves suppression of the other backward modes as well as directivity. (orig./AH)
[en] Chattering is a known issue in sliding mode control (SMC) and much research has been carried out to mitigate the chattering and its effects. In this work the chattering and stability analysis of the inverse hyperbolic function (IHF) based reaching law (RL) has been carried out. The work mathematically formulates the reaching time and calculates the describing function (DF) for the IHF based RL, which is used to formulate the conditions for chattering avoidance. The bound for the gain of RL has been calculated that will result in the chattering avoidance. Finally the proposed scheme has been used to control the speed of DC motor. Experimental results show avoidance of chattering and reduction in the reaching time.
[en] This comment is to point out to mistakes made in the paper (Ni et al. in Nonlinear Dyn 89:2065–2083, 2017). It is shown that the proofs of the stability of reaching and sliding phases given in the mentioned paper are not acceptable. Furthermore, the reported simulation results contradict with fractional calculus. This is evidenced by resimulating the example 1 of the paper.
[en] For a microwave source according to the gyrotron principle a beam conductor surrounds the electron beam and is used to conduct it. In order to damp undesired wave modes within the beam conductor a number of damping openings are required. The characteristic dimension of these openings is dependent on the wave length of the modes to be damped. 4 figs
[en] A design for a 90 degrees bend for the TE01 mode in overmoded circular waveguide is presented. A pair of septa, symmetrically placed perpendicular to the plane of the bend, are adiabatically introduced into the waveguide before the bend and removed after it. Introduction of the curvature excites five propagating modes in the curved section. The finite element field solver YAP is used to calculate the propagation constants of these modes in the bend, and the guide diameter, septum depth, septum thickness, and bend radius are set so that the phase advances of all five modes through the bend are equal modulo 2π. To a good approximation these modes are expected to recombine to form a pure mode at the end of the bend
[en] The controllability problem of heterogeneous interdependent group systems with undirected and directed topology is investigated in this paper. First, the interdependent model of the heterogeneous system is set up according to the difference of individual characteristics. An extended distributed protocol with the external sliding-mode control is designed, under which it is shown that a heterogeneous interdependent group system is controllable when the corresponding communication topology is controllable. Then, using the network eigenvalue method, the driving individuals are determined for a heterogeneous system with undirected topology. Under directed topology, the maximum match method is utilized to confirm the driving individuals. Some sufficient and necessary conditions are presented to assure that the heterogeneous interdependent group system is structurally controllable. Via theoretical analysis, the controllability of heterogeneous interdependent systems is related to the interdependent manner and the structure of the heterogeneous system. Numerical simulations are provided to demonstrate the effectiveness of the theoretical results. (paper)
[en] In order to design a controller which can take both ride comfort and road holding into consideration, a hybrid model reference sliding mode controller (HMRSMC) is proposed. The controller includes two separate model reference sliding mode controllers (MRSMC). One of the controllers is designed so as to force the plant to follow the ideal Sky-hook model and the other is to force the plant to follow the ideal Ground-hook model; then the outputs of these two controllers are linearly combined and applied to the plant as the input. Also, since the designed controller requires a knowledge of the terrain input, this input is approximated by the unsprung mass displacement. Finally, in the simulation section of this study, the effect of the relative ratio between the two MRSMCs and the knowledge of the terrain on the performance of the controller is numerically investigated for both steady-state and transient cases