Department of Electrical Engineering

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IIT Jodhpur

Active vibration control is an important problem in structures. One of the ways to tackle this problem is to make the structure smart, adaptive and self-controlling. The main objective of active vibration control is to reduce the vibration of a system by automatic modification of the system's structural response. This work features the modeling and design of a robust decentralized controller for a smart flexible system using periodic output feedback control technique when there is a failure of a system component to function (say, a sensor or a actuator). The entire structure is modeled in state space form using FEM by dividing the master structure into 8 finite elements and placing the sensor / actuator pair at finite element positions 2, 4, 6 and 8. Robust decentralized POF controllers are designed for the various models of the plant by retaining the first two vibratory modes. The effect of the failure of one of the piezo patch is observed. In this proposed control law, the control inputs to each actuator of the multimodel flexible system is a function of the output of that corresponding sensor, only and the gain matrix has got all off-diagonal terms zero. The designed robust controller provides satisfactory stabilization of the multimodel smart structure system.

World University root node

Proceedings of SPIE - The International Society for Optical Engineering

Fault tolerant control of flexible smart structures using robust decentralized periodic output feedback technique

Active Vibration Control is an important problem in structures. One of the ways to tackle this problem is to make the structure smart, adaptive and self-controlling. The objective of active vibration control is to reduce the vibration of a system by automatic modification of the system's structural response. This work features the modeling and design of a robust decentralized controller for a smart flexible system using fast output sampling feedback control technique when there is a failure of a system component (say, a actuator) to function. In this proposed control law, the control inputs to each actuator of the multimodel is a function of the output of that corresponding sensor only and the gain matrix has all off-diagonal terms zero. The designed robust controller provides satisfactory stabilization of the multimodel smart structure system.

2004 5th Asian Control Conference

Fault tolerant control of flexible smart structures using robust decentralized fast output sampling feedback technique

A method is presented to design a spatial control system of a large pressurised heavy water reactor (PHWR) with the constraint that the closed loop system be stable even if one sensor or actuator has failed. Linear state models are obtained corresponding to the normal operating condition and different failure modes of the reactor. Each model is found to possess the two time scale property. Using similarity transformation each two time scale model is converted into a block diagonal form by which two subsystems, namely a fast subsystem and a slow subsystem, are easily obtained. State feedback is designed separately for the slow and the fast subsystems for each model. Then a composite state feedback gain is obtained from the state feedback gains computed for the slow and fast subsystems separately for each model. The composite state feedback so designed assigns the poles at arbitrary locations for the respective models. These composite state feedback gains are realised simultaneously by fast output sampling gains. Thus the states of the system are not needed for feedback purposes. An LMI formulation is used to overcome the undesired effects of poor error dynamics and noise sensitivity which are encountered if state feedback is realised exactly.

IEE Proceedings: Control Theory and Applications

Fault-tolerant spatial control of a large pressurised heavy water reactor by fast output sampling technique

The paper presents a method for output feedback sliding mode control for permanent magnet (PM) stepper motor which is known to be differentially flat system. Discretization of continuous time model of the stepper motor has been carried out and linearizing outputs are selected. Discrete state variables and control inputs are obtained in terms of linearizing outputs and their higher order differences. Linearized equations for the system are thus obtained and auxilary control is designed using reaching law approach. Then the actual control is obtained in terms of flat output and state variables. It has been shown that this can be expressed in terms of the flat output samples only. The control when applied to nonlinear system will give the same result as that of the state feedback case. © 2004 IEEE.

Proceedings of the IEEE International Conference on Control Applications

Multirate output feedback sliding mode control of permanent magnet stepper motor using flatness property

This paper presents a novel type of lateral series microwave switch on a silicon-on-insulator (SOI) substrate with a coplanar waveguide (CPW) configuration. It is built with a cantilever beam at the side of the gap of the microwave t-line and laterally driven by electrostatic force. The mechanical structures are made of single-crystal-silicon and fabricated by deep reactive ion etch (DRIE) technology. Evaporated aluminum serves as contact material. The fabrication process only needs one mask. The measured result shows up to 26.5 GHz the isolation of the switch is over 18 dB. The threshold voltage is about 12 volts. © 2003 IEEE.

DTIP 2003 - Design, Test, Integration and Packaging of MEMS/MOEMS 2003

An approach of lateral RF MEMS switch for high performance

In this paper a method is presented to design a controller for discrete two time scale system based on fast output sampling technique. Using similarity transformation the two time scale system is converted into a block diagonal form which is then partitioned into two subsystems, namely, a fast subsystem and a slow subsystem. Now state feedback controls are designed separately for the slow subsystem and the fast subsystem. Then a composite state feedback control is obtained from the state feedback controls designed for subsystems to assign the eigenvalues of the entire system at arbitrary locations. This composite state feedback gain is realized by using fast output sampling feedback gain. Thus the states of the system are not needed for feedback. But in practice there are two problems in realizing the state feedback gain exactly viz. poor error dynamics and noise sensitivity. So a linear matrix inequality formulation is used to overcome these undesired effects. The method has been applied to a large pressurized heavy water reactor (PHWR) for control of xenon induced spatial oscillations. A particular grouping of the state variables has been considered to decompose the system into the slow subsystem and the fast sub-system. Then fast output sampling fedback gains have been calculated. The efficacy of the control has been demonstrated by simulation of transient behavior of the nonlinear model of the PHWR.

IEEE Transactions on Nuclear Science

Spatial Control of a Large Pressurized Heavy Water Reactor by Fast Output Sampling Technique

Power system stabilisers (PSS) are added to excitation systems to enhance the damping of low-frequency oscillations. The design of PSS for a single machine connected to an infinite bus using periodic output feedback is proposed. The non-linear model of a machine is linearised at different operating points and 16 linear plant models are obtained. For each of these plants an output injection gain is obtained using the LQR technique. A robust periodic output feedback gain which realises these output gains is obtained using an LMI approach. This robust periodic output control is applied to a non-linear plant model of the machine at different operating (equilibrium) points. This method does not require the complete set of states of the system for feedback and is easily implementable.

IEE Proceedings: Communications

Design of power system stabiliser for single-machine system using robust periodic output feedback controller

Power system stabilizers (PSS) are added to excitation systems to enhance the damping during low frequency oscillations. In this paper, the design of PSS for single machine connected to an infinite bus using fast output sampling feedback is proposed. The non-linear model of a machine is linearized at different operating points and 16 linear plant models are obtained. For all of these plants a single stabilizing state feedback gain, F is obtained. A robust fast output sampling feedback gain which realizes this state feedback gain is obtained using linear matrix inequalities approach. This method does not require state of the system for feedback and is easily implementable. This robust fast output sampling control is applied to non-linear plant model of one machine at different operating (equilibrium) points. This method gives very good results for the design of PSS. © 2003 Elsevier Science B.V. All rights reserved.

Electric Power Systems Research

Design of power system stabilizer for single machine system using robust fast output sampling feedback technique

A systematic procedure for design of variable structure model following load frequency controller for a single-area power system has been presented. The variable structure model following control (VSMFC) technique presented in this paper not only guarantees invariance to a class of parameter variations and disturbances but also possesses other attractive features of variable structure systems (VSS) such as robustness to unknown disturbances, simplicity in design, and reduced order dynamics when in sliding mode. The simulation results of the variable structure model following control strategy to load frequency control are presented by changing all parameters by 30% to 50% from their nominal values. These results show that systems performance is robust to parameter variations and disturbances.

Systems Science

Robust variable structure model following controller for load frequency control

The advent of electronic controllers in the field of gas turbine control has allowed the implementation of sophisticated control algorithms. This paper proposes one such method, to design a controller using piecewise constant periodic output feedback, which has multifarious advantages, and because the states are not required for feedback, complete pole-assignability is guaranteed and the method is easily implementable.