In this paper, a mathematical model is developed to describe the dynamics of the drum-level of a natural circulation boiler. A boiler-drum is divided into two parts; the upper part contains saturated steam while the lower part contains a steam/water mixture. The ratio of the steam in that mixture is defined in this work as the steam volumetric ratio. On the other hand, balance equations are applied to the drum. The resulting equations are used to model the drum-level. The importance of the resulting model comes from the direct modeling of drum level which is usually computed off-line with the aid of empirical formulas and assumptions. Safe operation of boilers requires perfect level controller which cannot be designed without proper modeling. Simulation of the water level dynamics for step changes in heat rate and steam demand are compared with those in the literature. The results show that the drum level can be obtained from the basic balance equations.

This paper deals with the servo system design for hard disk drives using the approaching index switching algorithm introduced in [1]. The index represents a closed loop measure of the closeness of the system output to the reference set value. A switching algorithm is designed to switch between two different control sets according to the value of the index. The first control set is supposed to be suitable to drive the system output fast enough towards the required set value while the other control set should have enough damping to reach the final destination without overshoot. The simulation results using a mathematical model of a voice-coil-motor VCM actuator of a hard disk drive show that this approach is very effective. Giving rise to faster rise time, minimal overshoot, and a limited control signal compared to a conventional PID controller.

The vibration of a single link flexible manipulator is attenuated using the Active Constrained layer damping (ACLD) treatment. The ACLD treatment consists of a viscoelastic layer sandwiched between two piezo-electric layers acting as constraining layers with sensing and actuation capabilities. The shear deformation of the visco-elastic layer is controlled to enhance the energy dissipation mechanism and attenuate the vibration of the flexible manipulator. A finite element model is used to describe the dynamics of the system. A third order polynomial is used to describe the lateral displacement of the manipulator and a second order polynomial is used to describe the longitudinal displacements of the different layers of the manipulator. An appropriate control law is used to control the system. The Coupled Modal Strain energy technique is used to compute the equivalent viscous damping ratios for the elastic layer using the loss factor data of the material. The theoretical predictions of the model are compared with the experimental performance of a manipulator fully treated with a Dyad 606 visco-elastic layer sandwiched between two layers of polyvinylidene fluoride (PVDF) piezo-electric films. The results obtained clearly demonstrate the attenuation capabilities of the Actively-Controlled Constrained Layer Damping.

This paper presents a comparison between the approaching index switching algorithm (AISA) and a fuzzy controller for attitude control in a nanosatellite in 3-axes. AISA is designed to switch between two different controls based on an index value. The first controller accelerates the system to reach the desired angle. The other controller is decelerating the system before approaching the desired angle. A reaction wheel (RW) is used to provide the torque required to rotate the satellite about its axis. The purpose of the controller is to change the rotational speed of the RW so that the satellite points in the correct direction. This comparison reveals that the AISA controller is much more efficient in maneuvering and accurate in contrast to fuzzy control. The control effort is preserved by 66% compared to the fuzzy control effort. This shows that the use of this type of intelligent control system represents a significant advantage over the conventional control systems currently used for satellite attitude control.

No abstract