B.T. Costic

A MATLAB-based control systems laboratory experience for undergraduate students: toward standardization and shared resources

This paper seeks to begin a discussion with regard to developing computer aided control system design (CACSD) tools to promote undergraduate controls laboratory development. The advocated CACSD design tools are based on the popular, commercially available MATLAB environment, the Simulink toolbox, and the Real-Time Workshop toolbox. This paper describes how these tools can be utilized to address several issues that are confronted by control systems educators including: standardization, budget constraints, and limited resources. Specifically, by confronting the standardization issue, the following advantages are realized for laboratory development: (1) the required computer hardware will be low cost; (2) commercially available plants from different manufacturers can be supported under the same CACSD environment with no hardware modifications; (3) both the Windows and Linux operating systems can be supported via the MATLAB based Real-Time Windows Target and the Quality Real-Time Systems (QRTS) based Real-Time Linux Target; and (4) the Simulink block diagram approach can be utilized to prototype control strategies, thereby, eliminating the need for low level programming skills. The advantages related to standardization of the CACSD design tools will enable educators to confront the additional budget constraint and limited teaching resources issue by facilitating: (1) the sharing of laboratory resources within each university (i.e., between departments); (2) the development of Internet laboratory experiences for students (i.e., between universities); and (3) the initiation of an Internet-based archive of laboratory tutorials and Simulink files for in-house developed plants and commercially available plants.

Nonlinear tracking control of the VTOL aircraft

In this paper, we present a nonlinear tracking controller for the nonminimum-phase, underactuated model of a vertical take off and landing (VTOL) aircraft. Specifically, the controller is designed to ensure that the VTOL aircraft position/orientation tracks a reference signal generator. The controller ensures that the position/orientation tracking error can be exponentially forced into an arbitrarily small neighborhood around zero (i.e., globally uniformly ultimately bounded (GUUB) tracking).

Towards the standardization of a MATLAB-based control systems laboratory experience for undergraduate students

The paper seeks to begin a discussion with regard to developing standardized computer aided control system design (CACSD) tools that are typically utilized in an undergraduate controls laboratory. The advocated CACSD design tools are based on the popular, commercially available MATLAB environment, the Simulink toolbox, and the Real-Time Workshop toolbox. The primary advantages of the proposed approach are as follows: 1) the required computer hardware is low cost, 2) commercially available plants from different manufacturers can be supported under the same CACSD environment with no hardware modifications, 3) both the Windows and Linux operating systems can be supported via the MATLAB based Real-Time Windows Target and the Quality Real Time Systems (QRTS) based Real-Time Linux Target, and 4) the Simulink block diagram approach can be utilized to prototype control strategies; thereby, eliminating the need for low level programming skills. It is believed that the above advantages related to standardization of the CACSD design tools will facilitate: 1) the sharing of laboratory resources within each university (i.e., between departments) and 2) the development of Internet laboratory experiences for students (i.e., between universities).

A new learning control approach to the active magnetic bearing benchmark system

This paper presents a nonlinear control method for the active magnetic bearing benchmark system. A flux input controller, based on a new iterative learning control strategy, is proposed to asymptotically regulate the system while compensating for periodic, exogenous disturbances. Numerical simulation results are presented to illustrate the performance of the proposed controller.

Energy management and attitude control strategies using flywheels

This paper is devoted to the use of multiple flywheels that integrate the energy storage and attitude control functions in space vehicles. This concept, which we refer to as an integrated energy management and attitude control (IEMAC) system, reduces the space vehicle bus mass, volume, cost, and maintenance requirements while maintaining or improving the space vehicle performance. To this end, we present two nonlinear IEMAC strategies (model-based and adaptive) that simultaneously track a desired attitude trajectory and desired energy/power profile. Both strategies ensure asymptotic tracking while the adaptive controller compensates for uncertain spacecraft inertia.

Nonlinear control of magnetic bearing in the presence of sinusoidal disturbance

We present a modular control strategy to achieve global asymptotic stability for the regulation problem of a single-axis active magnetic bearing (AMB) in the presence of an unknown sinusoidal disturbance (i.e., the amplitude and the frequency are unknown). Specifically, we design a set of linear, BIBO filters to facilitate the utilization of standard adaptive control techniques to compensate for the effects of the unknown sinusoidal disturbance. In view of the fact that the disturbance frequency might slowly vary with time, we utilize a least squares prediction error-based update law to promote faster convergence of the parameter estimates.

Autobalancing DCAL controller for a rotating unbalanced disk

We design a control strategy for a rotating unbalanced disk. The control strategy is composed of a control torque and two control forces. The control strategy regulates disk displacement while ensuring that the unbalanced disk tracks a desired angular velocity trajectory. Specifically the control uses a desired compensation adaptation law (DCAL) and a gain adjusted forgetting factor to achieve exponential stability despite the lack of knowledge of the imbalance-related parameters provided a mild persistency of excitation condition is satisfied.

Boundary control of a two-dimensional flexible rotor

In this paper, we present the design of boundary controllers for a two-dimensional, spinning flexible rotor system. Specifically, we develop a model-based boundary controller which exponentially regulates the rotors displacement and the angular velocity tracking error, and an adaptive boundary controller which asymptotically achieves the same control objective while compensating for parametric uncertainty. As opposed to previous boundary control work, which focused on the velocity setpoint problem and placed restrictions on the magnitude of the desired angular velocity setpoint, the proposed control architecture achieves angular velocity tracking with no restrictions on the magnitude of the desired velocity trajectory.

Boundary control for a general class of string models

We study the control of an undamped, nonlinear string model with actuator dynamics at the boundary. Specifically, we develop a boundary controller which asymptotically stabilizes the out-of-plane displacement. The performance of the controller is illustrated via dynamic simulation.

Repetitive learning control: a Lyapunov-based approach

In this paper, a learning-based feedforward term is developed to solve a general control problem in the presence of unknown nonlinear dynamics with a known period. Since the learning-based feedforward term is generated from a straightforward Lyapunov-like stability analysis, the control designer can utilize other Lyapunov-based design techniques to develop hybrid control schemes that utilize learning-based feedforward terms to compensate for periodic dynamics and other Lyapunov-based approaches (e.g., adaptive-based feedforward terms) to compensate for non-periodic dynamics. To illustrate this point, a hybrid adaptive/learning control scheme is utilized to achieve global asymptotic link position tracking for a robot manipulator.