754 research outputs found
Stabilization over power-constrained parallel Gaussian channels
This technical note is concerned with state-feedback stabilization of multi-input systems over parallel Gaussian channels subject to a total power constraint. Both continuous-time and discrete-time systems are treated under the framework of H2 control, and necessary/sufficient conditions for stabilizability are established in terms of inequalities involving unstable plant poles, transmitted power, and noise variances. These results are further used to clarify the relationship between channel capacity and stabilizability. Compared to single-input systems, a range of technical issues arise. In particular, in the multi-input case, the optimal controller has a separation structure, and the lower bound on channel capacity for some discrete-time systems is unachievable by linear time-invariant (LTI) encoders/decoder
Integral control of port-Hamiltonian systems: non-passive outputs without coordinate transformation
In this paper we present a method for the addition of integral action to
non-passive outputs of a class of port-Hamiltonian systems. The proposed
integral controller is a dynamic extension, constructed from the open loop
system, such that the closed loop preserves the port-Hamiltonian form. It is
shown that the controller is able to reject the effects of both matched and
unmatched disturbances, preserving the regulation of the non-passive outputs.
Previous solutions to this problem have relied on a change of coordinates
whereas the presented solution is developed using the original state vector
and, therefore, retains its physical interpretation. In addition, the resulting
closed loop dynamics have a natural interpretation as a Control by
Interconnection scheme.Comment: 8 pages, 2 figure
Large-signal stability conditions for semi-quasi-Z-source inverters: switched and averaged models
The recently introduced semi-quasi-Z-source in- verter can be interpreted as
a DC-DC converter whose input- output voltage gain may take any value between
minus infinity and 1 depending on the applied duty cycle. In order to generate
a sinusoidal voltage waveform at the output of this converter, a time-varying
duty cycle needs to be applied. Application of a time-varying duty cycle that
produces large-signal behavior requires careful consideration of stability
issues. This paper provides stability results for both the large-signal
averaged and the switched models of the semi-quasi-Z-source inverter operating
in continuous conduction mode. We show that if the load is linear and purely
resistive then the boundedness and ultimate boundedness of the state
trajectories is guaranteed provided some reasonable operation conditions are
ensured. These conditions amount to keeping the duty cycle away from the
extreme values 0 or 1 (averaged and switched models), and limiting the maximum
PWM switching period (switched model). The results obtained can be used to give
theoretical justification to the inverter operation strategy recently proposed
by Cao et al. in [1].Comment: Submitted to the IEEE Conf. on Decision and Control, Florence, Italy,
201
On Limitations to the achievable path following performance for linear multivariable plants
In this paper, we consider a problem termed “path
following”. This differs from the common problem of reference tracking, in that here we can adjust the speed at which we traverse the reference trajectory. We are interested in ascertaining the degree to which we can track a given trajectory, and in characterizing the class of paths for which we can generate an appropriate
temporal specification so that the path can be tracked arbitrarily well in an L2 sense.We give various bounds on the achievable performance, as well as tight results in special cases. In addition, we give a numerical procedure based on convex optimization for computing the achievable performance. The results demonstrate that there are situations where arbitrarily good L2 performance may
be achieved even though the origin is not in the convex hull of the positive limit set of the path to be followed
On Limitations to the achievable path following performance for linear multivariable plants
In this paper, we consider a problem termed “path
following”. This differs from the common problem of reference tracking, in that here we can adjust the speed at which we traverse the reference trajectory. We are interested in ascertaining the degree to which we can track a given trajectory, and in characterizing the class of paths for which we can generate an appropriate
temporal specification so that the path can be tracked arbitrarily well in an L2 sense.We give various bounds on the achievable performance, as well as tight results in special cases. In addition, we give a numerical procedure based on convex optimization for computing the achievable performance. The results demonstrate that there are situations where arbitrarily good L2 performance may
be achieved even though the origin is not in the convex hull of the positive limit set of the path to be followed
Numerical Sensitivity of Linear Matrix Inequalities Using Shift and Delta Operators
The numerical sensitivity of linear matrix inequalities (LMIs) arising from discrete-time control with short sampling periods is analyzed using shift and delta operators. The delta operator avoids cancellation problems for short sampling periods, and it includes a system scaling proportional to the inverse of the sampling period. The numerical sensitivity of both these mechanisms is investigated analytically, and verified by numerical examples. The conclusion is that the scaling procedure is (somewhat surprisingly) much more essential for shorter sampling periods than avoiding the cancellation problem
On AIMD Congestion Control in Multiple Bottleneck Networks.
We consider a linear algebraic model of the Additive-Increase Multiplicative-Decrease congestion control algorithm and present results on average fairness and convergence for multiple bottleneck networks. Results are presented for
networks of both long-lived and short-lived flows
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