Benoit Boulet

Modeling and control of an electric arc furnace

Electric arc furnace (EAFs) are widely used in steelmaking and in smelting of nonferrous metals. The EAF is the central process of the so-called mini-mills, which produce steel mainly from scrap. The power level is directly related to production throughput, so it is important to control the EAF at the highest possible average power with a low variance to avoid breaker trips under current surge conditions. For efficient power control, good dynamic models EAFs are required. This paper solves the electrical circuit of an EAF with a floating neutral, proposes a dynamic model for the EAF, and investigates simple proportional electrode current and power control.

Terminal Iterative Learning Control design with singular value decomposition decoupling for thermoforming ovens

Terminal Iterative Learning Control (TILC) is a cycle-to-cycle control approach that can be used on thermoforming oven. TILC automatically tune the heater temperature setpoints such that the temperature at the surface of the plastic sheet tracks a desired temperature profile. Industrial thermoforming ovens can have a large number of temperature sensor (inputs) and heaters (outputs) which makes the design of TILC difficult. This paper presents the design of a TILC using the singular value decomposition decoupling technique. With this tool, the TILC design is facilitated for industrial thermoforming oven.

Consistency of open-loop experimental frequency-response data with coprime factor plant models

The model/data consistency problem for coprime factorization considered is: Given some possibly noisy frequency-response data obtained by running open-loop experiments on a system, show that these data are consistent with a given family of perturbed coprime factor models and a time-domain /spl Lscr//sub /spl infin// noise model. In the noise-free open-loop case, the model/data consistency problem boils down to the existence of an interpolating function in /spl Rscr//spl Hscr//sub /spl infin// that evaluates to a finite number of complex matrices at a finite number of points on the imaginary axis. A theorem on boundary interpolation in /spl Rscr//spl Hscr//sub /spl infin// is a building block that allows one to devise computationally simple necessary and sufficient tests to check if the perturbed coprime factorization is consistent with the data. For standard coprime factorizations, the test involves the computation of minimum-norm solutions to underdetermined complex matrix equations. The Schmidt-Mirsky theorem is used in the case of special factorizations of flexible systems. For /spl Lscr//sub /spl infin// noise corrupting the frequency-response measurements, a complete solution to the open-loop noisy SISO problem using the structured singular value /spl mu/ is given.

Control of an Overactuated Cable-Driven Parallel Mechanism for a Radio Telescope Application

The large adaptive reflector is a Canadian design concept for a new type of large-scale radio telescope. This new telescope would be composed of a reflector made of individually actuated panels and a multitethered feed platform held aloft by an aerostat. This paper focuses on the position and orientation control of the feed platform. Models of both the cables and the feed platform are first derived. Then, a control strategy adapted to the particular systems dynamics is designed. This control strategy is based on a cascade-control architecture, in which the inner control loop adjusts the tension in each cable. This inner loop controller is synthesized using the H infin optimal-control technique. In addition, gain scheduling is used to adapt the H infin optimal controller to the cable lengths. The outer control loop adjusts the pose of the feed platform, using inverse-dynamics control and PID control. The model derived is coupled to the multiloop controller, and simulations are run to evaluate the performance level of the control strategy.

Uncertainty modeling and experiments in /spl Hscr//sub /spl infin// control of large flexible space structure

Approaches to uncertainty modeling for robust control of large flexible space structures (LFSSs) such as additive or multiplicative perturbations in /spl Hscr//sub /spl infin// do not work very well because of the special properties of LFSS dynamics. We propose the use of a left-coprime factorization (LCF) of LFSS dynamics in modal coordinates in order to get improved stability margins and performance in robust control design. The plant uncertainty is then described as stable perturbations of the coprime factors accounting for modal parameter uncertainty and unmodeled dynamics. Two multivariable /spl Hscr//sub /spl infin// designs based on LCFs of 46th-order collocated and noncollocated models of an LFSS experimental testbed are presented together with simulation and experimental results to illustrate the technique.

Design and Experimental Validation of a Nonlinear Low-Level Controller for an Unmanned Fin-Less Airship

This paper discusses the design of a combined backstepping/Lyapunov controller for the attitude, velocity and height control of an unmanned, unstable, fin-less airship. As the airship actuation has more degrees of freedom than the motion controlled, the controller includes a quadratic optimization algorithm to find the optimal thruster commands. The control law developed provides attitude and velocity control for the entire airship flight regime, i.e., hover, vertical ascent and descent as well as cruise, all with a single controller. Controller performance is first verified using a simulation that includes detailed modeling of sensor noise, computational delays and actuation dynamics. Subsequently, the controller is tested in outdoor flight tests. The controller has been found to perform well both in simulation and flight tests. The controller parameters were identical in simulation and flight test demonstrating the high fidelity of the simulation.

Scheduling schemes for an integrated flight and propulsion control system

Abstract We describe two schemes for scheduling an integrated flight and propulsion control system for an experimental vertical/short take-off and landing (V/STOL) aircraft concept in the acceleration from hover (0– 120 kn ) flight phase. Multivariable integrated flight and propulsion controllers are designed at several points over the V/STOL envelope and implemented as exact plant observers with state feedback. In the first scheduling scheme, the values of the state feedback and observer gain matrices are interpolated between the fixed-point designs as a function of aircraft speed. In the second approach, the control signals produced by the different fixed-point controllers are blended, allowing a significant reduction in the order of the scheduled controllers. Both scheduling schemes are shown in non-linear simulation to provide excellent handling qualities as the aircraft accelerates from the hover.

Robust output feedback stabilization of uncertain time-varying state-delayed systems with saturating actuators

The robust output feedback stabilization problem for state-delayed systems with time-varying delays and saturating actuators is addressed here. The systems considered are continuous-time, with parametric uncertainties entering all the matrices in the system representation. A saturating control law is designed and a region of initial conditions is specified within which local asymptotic stability of the closed-loop system is ensured. The least conservative approach that employs the Lyapunov–Krasovskii functional is adopted to ensure stabilization. The designed controller is dependent on the time-delay and its rate of change. The controller is constructed in terms of the solution to a set of matrix inequalities.

An LMI approach to IMC-based robust tunable control

This paper presents a linear matrix inequalities (LMI) approach to robust tunable control. This controller design technique provides a new online tuning strategy for industrial process control systems. The tuning strategy is based on the performance robustness bounds of the system and knowledge of the plant uncertainty weighting function, which may change with time. The internal model control structure of the controller is adopted together with additive plant uncertainty. The design and tuning of the robust tunable controller for an SISO system relies on an approximate solution to the two-disc optimization problem, that is solved over the class of discrete-time finite impulse response filters via the solution of an LMI problem. A numerical example is given to illustrate the technique.

Dynamic modeling and controller design for a seamless two-speed transmission for electric vehicles

Transmission is one of the crucial elements of the driveline that affects vehicle fuel economy and comfort. It can transfer power in different combinations of torque and speed. This paper focuses on the modeling, simulation and control of a two-speed transmission for electric vehicles which has seamless gear shifting specification. The transmission incorporates two-stage planetary gear sets and two braking mechanisms to control the gear shifting. The dynamic model is developed by using the kinematic equations of the planetary gear trains and the Euler-Lagrange equations to derive the equations of motion. The mathematical model is validated by using the SimDriveLine library of MATLAB/Simulink®. The controller design employs optimal control methods to provide seamless shifting with minimum transition time. Then, by relaxing ideal constraints, a feasible controller is designed based on input-output and input-state feedback linearization. Simulation results demonstrate the ability of the proposed transmission to have smooth shifting without excessive oscillations in the output torque and speed.