State-space Control Model Research Articles

Active vibration control of a cylindrical structure using flexible piezoactuators: experimental work in air and water environments

In the present work, the modal characteristics and vibration control performance of a cylindrical structure in air and water are experimentally investigated, and the results are presented in time and frequency domains. In order to achieve this goal, an end-capped cylindrical shell structure is considered as a host structure, and MFC (macro fiber composite) actuators, which are flexible, are bonded on the surface of the structure. After manufacturing a cylindrical shell structure with aluminum, a modal test is carried out, and the natural frequencies of the proposed structure are obtained and analyzed. To verify the modal test results, a finite element analysis is also performed, and the results are compared with the modal test results. By using the experimentally obtained modal characteristics, a state space control model is established. An optimal controller is then designed in order to control the unwanted vibration and is experimentally realized. It has been shown that the structural vibration can be effectively decreased with the optimal control methodology in both air and water environmental conditions.

Constrained Markov control model and online stochastic optimization algorithm for power conservation in multimedia server cluster systems

This paper presents a novel Markov switching state space control model for dynamically switching resource configuration scheme to achieve power conservation for multimedia server cluster systems. This model exploits the hierarchical dynamic structure of network system and its construction is flexible and scalable. Using this analytical model, the problem of power conservation is posed as a constrained stochastic optimization problem with the goal of minimizing the average power consumption subject to the constraint on the average blocking ratio. Applying Lagrange approach and online estimation of the performance gradient, a policy iteration algorithm is proposed to search the optimal policy online. This algorithm does not depend on any prior knowledge of system parameters, and converges to the optimal solution. Simulation results demonstrate the convergence of the proposed algorithm and effectiveness to different access workloads.

Impact of Feedback Delay on Closed-Loop Stability in Semiconductor Optical Amplifier Control Circuits

Semiconductor optical amplifiers (SOAs) are attractive for integrated photonic signal processing, but because their response is so fast, delays in a controller feedback path can jeopardize performance and stability. Using state-space methods, we quantify the constraints imposed on feedback controllers by closed-loop delay. We first derive a complete nonlinear state-space control model of a SOA with an equivalent circuit containing parasitics and dynamic impedance; the analytical state-space model agrees well with a validated photonic-only control model. Using a linearized version of the model we demonstrate that time delay in the feedback path can destabilize the SOA through phase accumulation. We then apply linear system theory to calculate the best-case stable delay margin for a given controller norm, and find a potentially severe inverse relationship between delay margin and controller norm. Finally, guided by the delay-controller relationship we design a hybrid feedforward-feedback controller to illustrate that good transient and steady-state regulation is obtained by carefully balancing the feedforward and feedback components. Our state-space modeling and design methods are general and are easily adapted to the design and analysis of more complex photonic circuits.

Optimal control of structural vibrations using a mixed-mode magnetorheological fluid mount

In this work, a mixed-mode magnetorheological (MR) mount is proposed and applied to the vibration control of a flexible beam structure subjected to external disturbances. On the basis of non-dimensional Bingham number, an appropriate size of the MR mount is designed and manufactured. After experimentally evaluating the field-dependent damping force of the MR mount, a structural system consisting of a flexible beam and vibrating rigid mass is established. The governing equation of motion of the system is derived and expressed as a state space control model. A linear quadratic Gaussian (LQG) controller is then designed in order to attenuate the vibration of the structural system. The controller is empirically realized and control responses such as acceleration and displacement of the structural system are evaluated and presented in frequency domain.

Vibration Control of a Structural System Using Magneto-Rheological Fluid Mount

In this work, a mixed mode-type magneto-rheological fluid mount (MR mount in short) is devised by considering the nondimensional formulation of Bingham plastic flow, and applied to vibration control of a structural system subjected to external excitations. The structural system consists of a vibrating mass, semi-active MR fluid mount, and passive rubber mounts. The MR mount is installed on the beam structure as a semi-active actuator and supports the vibrating mass, while the flexible beam structure is supported by two passive rubber mounts. After verifying the field-dependent damping force characteristics of the MR mount, the governing equation of the structural system is derived in the modal coordinate and rewritten as a state space control model. The linear quadratic Gaussian (LQG) controller is then formulated in order to attenuate vibration of the structural system. The LQG controller is experimentally realized and control responses such as accelerations and transmitted forces of the structural system are presented in the frequency domain.

Gray Balance Control Loop for Digital Color Printing Systems

Four-color process printers generally use gray balance for achieving color balance. Here we describe a novel gray balance control system which uses multivariable state feedback principles. We show that the system performance is greatly improved and the requirements on number of color measurements per calibration initialization are greatly reduced. A synthesis of a state space control model, feedback controller and TRC smoothing techniques are discussed in detail to achieve good prints after gray balance. Experimental results are shown to validate the approach when used for real-time feedback control of color systems.

Vibration control of a frame structure using electro-rheological fluid mounts

A squeeze-mode electro-rheological (ER) mount has been designed, manufactured, and applied to the vibration control of a frame structure subjected to external excitations. After verifying that the damping force of the ER mount can be controlled by controlling the applied voltage, a frame structure system supported by spring mounts and the proposed ER mounts has been assembled. The governing equation of the structural system is derived in the modal coordinate and is rewritten as a state-space control model. An optimal controller, which consists of the velocity feedback signal of the frame structure and the force feedback signal transmitted from the exciting point to the mount position, is formulated in order to attenuate the imposed excitations. The controller has been optimized experimentally and control responses such as the acceleration of the frame structure and the transmitted force at each mount position are presented in both time and frequency domains.

Force tracking control of a flexible gripper featuring shape memory alloy actuators

This paper presents a robust force tracking control of a flexible gripper using shape memory alloy (SMA) actuators. The governing equation of a partial differential form for the flexible gripper is derived by employing Hamilton’s principle, and a state-space control model is obtained by retaining a finite number of vibration modes. In the formulation of the control model, time constant of the SMA actuator is treated as uncertain parameter. This is adopted due to the fact that the SMA actuator has different time constant at the heating and cooling stage, respectively. The H ∞-controller is then synthesized by treating the uncertain parameter as coprime factor. The specifications of stability margin and steady state error to achieve robust performance are imposed, and the first-order reference model is augmented to avoid excessive overshoot. After analyzing the robust stability of the system using the singular value plot, the controller is experimentally realized and force tracking control responses for step and sinusoidal force trajectories are presented in time domain to demonstrate the effectiveness of the proposed methodology.

Position tracking control of an optical pick-up device using piezoceramic actuator

This paper proposes a piezoactuator-driven optical pick-up for compact disc-read only memory (CD-ROM) drive in order to achieve fine motion control of objective lens. The dynamic model of the proposed optical pick-up consisting of piezoceramic bimorph, wire suspension and objective lens is derived from Hamilton’s principle. A state-space control model is subsequently formulated by considering hysteresis behavior of the piezoactuator and frequency variation of the device as uncertainties. A sliding-mode controller, which is known to be robust to system uncertainties is designed for fine motion tracking control of the objective lens in vertical direction (focusing). The controller is then experimentally realized and position-tracking responses of the optical pick-up are presented in time domain. In addition, control durability is demonstrated by showing favorable tracking performance of a sinusoidal trajectory up to 8000 cycles of operation.

Modeling and Analysis for Active Control of Circular Saw Vibrations

Addressed in this paper is modeling and analysis for active control of circular saw vibrations. A method is put forward based on finite element modeling. It starts with modeling of a circular saw in the body- fixed frame, where vibration analyses including natural frequencies and modes can be readily obtained by a standard finite element analysis package. To consider the rotation of a circular saw, the finite element model is transformed to the space-fixed frame, where vibration mode shapes remain the same while natural frequencies are affected by the product of the rotation speed and the order of the mode shape. Upon normalization, the vibration equations can be expressed in terms of natural frequencies and modes, from which a state-space control model can be obtained. The model developed has shown a good agreement between simulation and experimental results. Furthermore, the model is used to design an online state estimator using the Kalman filter as well as an active vibration controller-based linear-quadratic-Gaussian method.

Force Tracking Control of a Flexible Gripper Driven by Piezoceramic Actuators

This paper presents a robust force tracking control of a flexible gripper driven by a piezoceramic actuator characterizing its durability and quick response time. The mathematical governing equation for the proposed system is derived by employing Hamilton’s principle and a state space control model is subsequently obtained through the modal analysis. Uncertain parameters such as frequency variation are included in the control system model. The sliding mode control theory which has inherent robustness to the system uncertainties is adopted to design a force tracking controller for the piezoceramic actuator. Using the output information from a tip force sensor, a full-order observer is constructed to estimate state variables of the system. Force tracking performances for desired trajectories represented by sinusoidal and step functions are evaluated by undertaking both simulation and experimental works. In addition, in order to illustrate practical feasibility of the proposed method, a two-fingered gripper is constructed and its performance is demonstrated by showing a capability of holding an object.

Robust Tracking Control of Smart Flexible Structures Featuring Piezofilm Actuators

This paper presents a robust control of a smart flexible structure featured by a piezofilm actuator characterizing its light weght and quick response time. A mathematical governing equation for the proposed structure is derived by employing Hamilton's principle and a state space control model is subsequentrly obtained through modal analysis. Uncertain system parameters such as frequency variation are included in the control model. A sliding mode control theroy thich has inherent robustness to systme uncertainties is adopted to design a tracking controller for the peizofilm actuator. Using the output informaiton from the tip deflection sensor, a full-order observer is constructed ot estimate state variables for the system. Tracking performances for desired trajectories of sinusoidal amd step functions are evaluated by undertaking both simulation and experimental works.