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Professor Alleyne's Publications

Conferences	Nonlinear Control of a Quarter Car Active Suspension Abstract In this paper, a quarter-car suspension system with a hydraulic actuator, acting under the effects of coulomb friction, is examined. Nonlinear control laws will be developed and compared with both a passive system and a system acting under linear control. An observer-based nonlinear controller and an adaptive nonlinear controller will also be presented. Experimental results will be compared with both theoretical and simulation results. Back to Conferences	~ welcome ~

. Professor Alleyne's Publications

Conferences	Application of Nonlinear Control Theory to Electronically Controlled Suspensions Abstract This paper illustrates the use of nonlinear control theory for designing electro-hydraulic active suspensions. A nonlinear, "sliding" control law is developed and compared with the linear control of a quarter-car active suspension system acting under the effects of coulomb friction. A comparison will also be made with a passive quarter-car suspension system. Simulation and experimental results show that nonlinear control performs better than PID control and improves the ride quality compared to a passive suspension. Back to Conferences	~ welcome ~

. Professor Alleyne's Publications

Conferences	Adaptive Control for Active Suspensions Abstract This paper uses nonlinear control theory for the control of an elctro-hydraulic active suspension. A "sliding" controller is developed, combined with a parameter adaptation law, and implemented on a quarter car active suspension. Stability and robustness issues, as well as parameter convergence criterion will be discussed. The resulting performance is compared with that of a passive quarter car suspension. Simulation and experimental results at the natural frequency of the car body, 1 Hz, show that the controlled suspension performs better than the passive suspension in improving the ride quality of the quarter car system and parameter adaptation increases performance. Back to Conferences	~ welcome ~

. Professor Alleyne's Publications

Conferences	Switching Adaptive Control of Active Suspensions Abstract A novel approach to adaptive control is introduced and applied to automotive active suspension systems. A previously developed nonlinear "sliding" controller is coupled with a new parameter adaptation algorithm(PAA). The PAA is a gradient algorithm, developed using a Lyapunov approach. The new adaptive control approach differs from a standard adaptive one in that the unknown parameters are allowed to change as rapidly as the states themselves. The PAA switches between different sets of estimated parameters depending on states of the system. As a result, these parameters are not restricted to being constant or slowly time-varying; however, they are restricted to being constant or slowly time-varying within regions of the state space. Convergence and stability properties of this method are examined and discussed. The adaptive control approach is applied to a quarter car active suspension and the system performance is analyzed experimentally. The analysis shows that the new adaptive approach results in improved performance over standard adaptive controllers. Back to Conferences	~ welcome ~

. Professor Alleyne's Publications

Conferences	Multiple Surface Sliding Control Abstract This paper investigates the control of a class of nonlinear systems whose relative degrees are greater than one. The relative degree of a system can be defined as the number of times the system output must be differentiated in order to generate an explicit relationship between the output, and the system input. The control approach to be implemented is a robust version of Feedback Linearization known as Sliding Control and it is applied to SISO systems here. The standard approach to controlling systems with relative degree (r) greater than one is to use a sliding controller with an (r-1)th order sliding surface. An alternative approach, presented here, is to separate the sliding controller into (r-1) sliding surfaces and control each one individually. The entire closed loop system is then analyzed for stability. Back to Conferences	~ welcome ~

. Professor Alleyne's Publications

Conferences	Improved Vehicle Performance Using Combined Suspension and Braking Forces Abstract This paper investigates the integration of various subsystems of an automobile's chassis. The specific focus of this research is the integration of active suspension components with anti-lock braking system(ABS) mechanisms. The performance objective for the integrated approach is defined as a reduction in braking distance over just anti-lock brakes. A two degree of freedom Half Car vehicle model is developed along with models for a hydraulic active suspension and an ABS system. For both subsystems, actuator dynamics are included. Individual controllers are developed for the subsystems and a governing algorithm is constructed to coordinate the two controllers. Simulations of the integrated controller and an ABS system demonstrate a significant increase in performance. Back to Conferences	~ welcome ~

. Professor Alleyne's Publications

Conferences	A Systematic Approach to the Control of a Class of Feedback Linearizable Systems Abstract This paper develops a systematic methodology for the control of a class of feedback Linearizable systems. The class of systems to be dealt with are those that are SISO and can be put in Strict Feedback Form. Additionally, it is assumed that the relative degree of these systems is greater than one and the zero dynamics are stable. For a system with relative degree, r, a series of r system error s are defined. An input-output feedback stabilization method is then used to control each error through the use of synthetic inputs. Subsequently, the entire closed loop system is analyzed for stability. A class of modeling error is introduced and compensated for. The resulting control is able to guarantee specified boundary layer tracking. Finally, a comparison is made in simulation with the Integrator Backstepping approach. Back to Conferences	~ welcome ~

. Professor Alleyne's Publications

Conferences	A Comparison of Alternative Intervention Strategies for Unintended Roadway Departure(URD)Control Abstract This paper investigate the use of several different inputs for the control of a vehicle, in the context of URD. In this investigation, the goal of the URD controller is to provide an intervention in the event of the vehicle leaving the road. The types of inputs that will be considered are FOUR Wheel Steering, Rear Wheel Brake Steering. The controller design is an LQ controller based on the simplified dynamics of a 2 degree of freedom bicycle model. However, the analysis of the different strategies being examined. Unlike most control schemes, the performance measure to be used will not be the output tracking error of the system. Instead, the metric of performance is the ratio of peak tire force used versus available tire force or, in other words, the actuator response relative to the maximum available actuator capability. Back to Conferences	~ welcome ~

. Professor Alleyne's Publications

Conferences	Nonlinear Force Control of an Electro-Hydraulic Actuator Abstract In this paper, a Lyapunov_based algorithm is developed for the control of an electro-hydraulic actor. A first order nonlinear model for the actuator is developed from first principles. The servovalve used to control the actuator is modeled as a third order linear system and the controller uses model reduction to a first order system. Using Lyapunov_based techniques, a controller is developed which compensates for the modeled nonlinearities in the actuator. Additionally, parametric model uncertainties are compensated for by the inclusion of a gradient parameter adaptation scheme. The controllers are implemented on a simple force tracking problem, and the results are compared with typical linear controllers found in industrial practice. The comparison is carried out in simulation. The nonlinear controllers, although requiring additional state information, perform much better than the corresponding linear controllers. Back to Conferences	~ welcome ~

. Professor Alleyne's Publications

Conferences	A Variable Structure Gradient Algorithm for Adaptive Control Abstract A Standard assumption in adaptive control is that the parameters being estimated are either constant or vary 'slowly' as a function of time. In this paper an adaptive control algorithm is presented which eliminates the need for the previous assumption provided that the systems being controlled belong to a specified class. The type of systems may be either linear or nonlinear. For this class of systems, the state space is separated into remain constant, or be slowly time varying, within the subspaces. Given a controller for the system, a Lyapunov analysis of the output error dynamics and the parameter error dynamics leads to a parameter adaptation algorithm with a variable structure. The stability and convergence of both the parameter error and the output tracking error are investigated. An analysis of SISO, full-state feedback, linear systems is used to motivate and illustrate the treatment of SISO feedback linearizable systems. Back to Conferences	~ welcome ~

. Professor Alleyne's Publications

Conferences	A Collegewide Laboratory-based Program in Control Systems Technology at the University of Illinois at Urbana-Champaign Abstract We are developing a network of laboratories to support undergraduate and graduate in Control Systems Technology in the College of Engineering at the University of Illinois at Urbana-Champaign. The cornerstone of our program is a centralized Core Laboratory, which provides basic instruction in feedback control systems to all Departments in the College of Engineering. This core laboratory feeds into a network of satellite laboratories, which are designed to provide both vertical and horizontal integration of control systems and related technology across departmental boundaries in the engineering curriculum. By elevating control systems laboratory development from the Department level to the College level we have gained a number of advantages including, more efficient use of space and equipment, better leveraging of funds, elimination of overlap among individual departmental labs, better integration of control systems technology in the curriculum, the ability to hire a full time professional to manage the laboratory, and increased visibility with industry. At the same time we retain the integrity and autonomy of the separate Departmental curricula. This paper describes our concept and our initial experiences in this laboratory development. We focus here on the description of the Core Laboratory while briefly describing the first group of satellite laboratories under development. Back to Conferences	~ welcome ~

. Professor Alleyne's Publications

Conferences	Force Control of Fluid Power Systems Abstract n this work, a Lyapunov-based control algorithm is developed for the control of an electro-hydraulic actuator. A first order nonlinear model for the actuator is developed from first principles. The servovalve used to control the actuator is modeled as a third order linear system and the controller uses model reduction to a first order system. Using Lyapunov-based techniques, a controller is de eloped which compensates for the modeled nonlinearities in the actuator. Additionally, parametric model uncertainties are compensated for by the inclusion of a gradient parameter adaptation scheme. The controllers are implemented on a simple force tracking problem, representative of several manufacturing processes, and the results are compared with typical linear controllers found in industrial practice. The comparison is carried out in simulation. The nonlinear controllers, although requiring additional state information, perform much better than the corresponding linear controllers. Back to Conferences	~ welcome ~

. Professor Alleyne's Publications

Conferences	Infinite Horizon Optimal Control of A Class of Nonlinear Systems Abstract In (Banks et. al., 1992) it is shown that for the class of nonlinear systems d/dt (x) = A(x) x + B(x) u, the solution of the infinite horizon optimal control problem leads to a state dependent Ricatti equation. These results may be employed to generate stabilizing and optimal control laws in a manner which closely parallels the linear quadratic (LQ) technique commonly applied to linear dynamic systems. In the present work we apply this result to a more general class of nonlinear systems, in the form d/dt (x) = f(x) + g(x) u, by means of an appropriate transformation. We also study the robustness and implementability of this technique in real time control applications. Experimental results are given for the nonlinear benchmark problem introduced in (Kokotovic et. al., 1991). Similar to the Linear quadratic (LQ) technique, we obtain time-domain responses which are easily and transparently tuned by adjusting the entries in the penalty matrices. Back to Conferences	~ welcome ~

. Professor Alleyne's Publications

Conferences	Lateral Displacement Sensor Placement and Forward Velocity Effects on Stability of Lateral Control of Vehicles Abstract This paper presents both a simulation and experimental look at lateral vehicle dynamics for automatic steering control. Simulation work shown is based upon the well known "bicycle model". Experimental work is completed on a small-scale vehicle run on the Illinois Roadway Simulator(IRS). Frequency and time domain methods are used to model the vehicle for various sensor locations and forward speeds. The resulting model is a polynomial transfer function from front steer angle input to lateral displacement output. The trends of the bicycle model appear in the experimental vehicle both in pole and zero mapping. In addition, the steering actuator of the vehicle is shown to be a significant factor for model reference and PI based control design. Back to Conferences	~ welcome ~

. Professor Alleyne's Publications

Conferences	Multivariable Bilinear Vehicle Control using Steering and Individual Wheel Torques Abstract This paper is concerned with the stabilization of the lateral motion dynamics of an automobile. A planar vehicle model is used which includes yawing velocity and lateral velocity degrees of freedom. The controllable system inputs are the front and rear wheel steer angles as well as the torque input at each wheel. The model presents two departures from earlier work in this field. The first of these is that the wheel torques may assume both positive or negative values, as would be the case for an electric vehicle with a motor at each of its wheels. The second of these is the inclusion of bilinear terms involving steer angles and wheel torques in the model formulation. The bilinear terms are used to model the effect of steer angles on the effective moment arm associated with brake or drive torques applied at the relevant wheel. A state feedback controller which minimizes a quadratic performance index is developed and simulations are used to evaluate the performance of the proposed controller on a more detailed vehicle model which includes nonlinear tire characteristics. Back to Conferences	~ welcome ~

. Professor Alleyne's Publications

Conferences	Control of a Class of Feedback Stablizable Systems Abstract This paper develops a systematic methodology for the control of a class of feedback linearizable systems. The class of systems to be dealt with are thoose that SISO and can be put in Strict Feedback Form. Additionally, it is assumed that one and the internal dynamics are stable. For a system with relative degree, r, a series of r systemerrors are defined. An input-output feedback linearization method is then used tocontrol each error through the use of synthetic inputs. Subsequently, the entire closed loop system is analysis, this work presents an input-output stability analysis utilizing a Passivity formulation. A class of modeling error is introduced and compensated for. The resulting control is able to guarantee specified boundary layer tracking. Back to Conferences	~ welcome ~

. Professor Alleyne's Publications

Conferences	Control of a Class of Nonlinear Systems Subject to Periodic Exogenous Signals Abstract This paper examines the control of Single-Input, Single-Output Feedback Linearizable nonlinear systems that are either(i) subject to periodic disturbances or (ii) tracking periodic reference trajectories. The key concept is the straghtforward combination of well known differential Geometric techniques with the internal Model Principle resulting in a nonlinear repetitive control strategy. A formulation is presented for the case of Input-State Linearizable and Input-Output Linearizable systems in continuous time. The potential benefits of the nonlinear repetitive controller are given. It is shown that while the standard nonlinear control techniques can be made robust to known disturbances, the nonlinar repetitive technique has desirable characteristics in that it does not require knowledge of the disturbance magnitude and does not need an increased loop gain to accomplish robustness. The procedure is applied to a numerical simulation example with the resulting benefits being clearly shown. Back to Conferences	~ welcome ~

. Professor Alleyne's Publications

Conferences	On the Stability and Performance of Two Stage Hydraulic Servolves Abstract In this work, a System Dynamicsviewpoint is used to examine the stability and performance of a class of hydraulic devices. These devices use hydraulic amplication to command motion of large objects using relatively low level signals. A model is constructed and used for both analysis and simulation of system performance. The analysis is from a linear Classical Controls perspective and is found to be sufficient desipite the nonlinear nature of the systems. The analysis is used to consider design changes to the valve components and their resulting effects. Even though the subsystems consist of stable indicidual components, their interconnection can lead to undersirable performance, or even instability, if the individual dynamics are improperly matched. Back to Conferences	~ welcome ~