Transactions of the Institute of Measurement and Control

Bacciotti, A.; Mazzi, L.

doi: 10.1177/0142331208095427pmid: N/A

Given a finite or countable family of continuous vector fields {fi(x)}i∈ I , we show that there exists a feedback k : Rn → I such that the switched system x = fk(x)(x) is globally asymptotically stable whenever there exists a smooth control Liapunov function V such that for all x ≠ 0, ∇V(x)fi(x)<0, for some i ∈ I.

Blanchini, Franco; Viaro, Umberto

doi: 10.1177/0142331208095434pmid: N/A

A switched-control technique for fluid distribution systems is presented. It is based on a compartment model of the distribution network consisting of a number of interconnected reservoirs. The unforced flows among reservoirs and environment only depend (non-linearly) on the stored water levels (state variables), which are also influenced by the water demands (disturbances) and by the forced flows of the water pumped into or out of the reservoirs (controlled variables). The control objective is to drive the system to the equilibrium state and keep it there. This goal can be achieved by means of a state-feedback control, which entails switching the controlled inputs among given values according to the current system state. Necessary and sufficient stabilizability conditions are provided. The global asymptotic stability of the overall control system is proved by resorting to a suitable control-Lyapunov function. An experiment is worked out to show the performance of the adopted control policy.

Junyan Yu, ; Long Wang, ; Guangming Xie,

doi: 10.1177/0142331208095428pmid: N/A

Several disturbance rejection problems for switched continuous-time/discrete-time systems with saturating actuators are addressed. We focus our attention on the synthesis of feedback control laws to reject the disturbance for the systems under the designed switching signals, and sufficient conditions are derived for disturbance rejection. Furthermore, we consider switched continuous-time/discrete-time systems with time-varying uncertainties, and design robust switched control laws to reject the disturbance for any time-varying uncertainties. Two numerical examples are worked out to demonstrate the effectiveness of the proposed design technique.

Li, Li-li; Jun Zhao, ; Dimirovski, Georgi M.

doi: 10.1177/0142331208095429pmid: N/A

This paper focuses on the problem of robust H∞ control for a class of switched non-linear systems with neutral uncertainties. The multiple Lyapunov function approach and the common Lyapunov function approach are exploited respectively for the cases whether states are measurable or not. Uncertainties are allowed to appear in channels of state, control input and disturbance input. Conditions for the solvability of the robust H∞ control problem and design of both hybrid state feedback and dynamic output feedback controllers are presented. As an application, a hybrid state feedback strategy is proposed to solve the standard robust H∞ control problem for non-linear systems when no single continuous controller is effective.

Readman, Mark C.; Corless, Martin; Villegas, Carlos; Shorten, Robert

doi: 10.1177/0142331208095430pmid: N/A

With active vehicle suspension, one can tailor a vehicle’s response to load and inertial disturbances without affecting the vehicle response to road disturbances. This decoupling is achieved using a filtered combination of measured signals. These filters, which we call Williams filters, require exact knowledge of certain vehicle parameters including vehicle mass to achieve the desired decoupling. However, vehicle parameters, such as mass, are subject to abrupt variations as vehicle load changes. Here we propose an adaptive Williams filter that does not require knowledge of vehicle parameters.

Yanyan Yuan, ; Yupeng Qiao, ; Daizhan Cheng,

doi: 10.1177/0142331208095431pmid: N/A

The problem of static state feedback linearization of switched non-linear systems is investigated. First, we consider the regular state feedback linearization. In this case, the single-input switched system is considered first. A necessary and sufficient condition is provided, which contains an uncertain single variable function. Then the result is extended to a multiple input case. Secondly, the problem of non-regular static state feedback linearization is considered. Using semi-tensor product, some easily verifiable sufficient conditions are obtained. Then some examples are presented to illustrate the linearization process.

Zhendong Sun, ; Yuping Peng,

doi: 10.1177/0142331208095432pmid: N/A

In this paper, we develop a unified constructive design approach for continuous-time/discretetime switched linear control systems, which is analogous to the standard design mechanism of linear time-invariant systems. First, we prove that any switched linear system admits a system canonical decomposition with clear controllability structures. Then, we show that any controllable single-input switched linear system can be converted into a normal form by means of a state feedback transformation and a co-ordinate change, while a controllable multiinput system is feedback reducible to a controllable single-input system via non-regular state feedback. Next, based on the system normal form, we present constructive design procedures for quadratic and non-quadratic feedback stabilization for switched linear control systems. Finally, illustrative examples are carried out to exhibit the effectiveness of the proposed design method.

Zhijian Ji, ; Hai Lin, ; Gang Feng, ; Xiaoxia Guo,

doi: 10.1177/0142331208095562pmid: N/A

The paper presents two different approaches, which enable a state transformation for system equations of switched linear systems to controllability canonical forms. The approaches are based on a constructive basis selection procedure for the controllability subspace and a controllability Kalman-type rank condition of switched linear systems. The results contribute to clarify the switched system structure to a certain degree under complete controllability.

Lijuan Zhao, ; Zhigang Sun, ; Tatibouët, Jacques; Jen, Cheng-kuei

doi: 10.1177/0142331209355075pmid: N/A

The melting and thermo-mechanical degradation of poly(ethylene terephthalate) (PET) samples with different moisture levels were investigated in an internal mixer under different processing conditions. The investigation used an ultrasonic diagnosis system and a torque rheometer. The experiment results showed that: 1) a PET sample with a lower humidity level was more stable than that having higher water content under the same processing conditions; 2) higher temperatures and blade speeds accelerated melting and degradation rates. However, the transition point from a partially melted state of a PET sample to a completely melted state could only be identified by ultrasound and the onset of degradation was evident from the ultrasonic measurement as opposed to the torque measurement.