Observer-Based Control of Nonlinear Time-Delay Systems in Lower-Triangular Form

Time-delay systems is a special class of dynamical systems that are frequently present in many fields of engineering. It has been shown in the literature that the existence of a stabilizing observer-based controller is related to delay-dependent conditions that are generally satisfied for a small time delay. Motivating works towards reducing the conservatism of the results are among the on-going research topics especially when partial-state measurements are imposed. This paper investigates the problem of observer-based stabilization of a class of time-delay nonlinear systems written in triangular form. First, we show that a delay nonlinear observer is globally convergent under the global Lipschitz condition of the system nonlinearity. Then, it is shown that a parameterized linear feedback that uses the observer states can stabilize the system whatever the size of the delay. Illustrative example is provided to approve the theoretical results.

Load-Predictive Temperature Control of an Air Conditioning and Refrigeration System

In air conditioning and refrigeration (ACR) systems, the established industry method of capacity control is compressor ON/OFF cycling operations. This paper presents the design of load-predictive controller using compressor ON/OFF operations for temperature regulation with a target application of transport refrigeration systems. A dynamic ACR system model, which consists of a refrigerated cargo space, and a vapor compressor cycle (VCC) system, is developed. The validated VCC model is presented that captures compressor ON/OFF duty cycling dynamics. The dynamic cargo space model is described to accommodate varying conditions, such as door openings. The load-predictive controller tracks the pre-cool and predictive refrigeration load information which is generated based on the operating conditions in the next door-opening event, and decides to operate the VCC system with either normal ON/OFF control or pre-cool actions. Simulation results show that improved cargo space temperature regulation is obtained by implementing the load-predictive control strategy over the baseline industrial hysteretic control scheme in the coupled VCC/cargo space system.

Limitations of Employing Undirected Information Flow Graphs for the Maintenance of Rigid Vehicular Formations

In this paper, we consider the problem of decentralized control of a collection of homogeneous vehicles trying to maintain a rigid formation. Each vehicle attempts to maintain a specified constant safe distance from its adjacent vehicles in the collection. We consider an identical structure for each decentralized controller so that it is simpler from an implementation viewpoint as it does not depend on collection size or vehicle indices. We call a vehicle B adjacent to vehicle A if the relative position of vehicle B is known to vehicle A either by communication or by sensing. In this paper, we only consider undirected information flow graphs, i.e., graphs where vehicle A is adjacent to vehicle B if and only if vehicle B is adjacent to vehicle A. We consider a point mass model for each vehicle and assume the actuation transfer function, which relates the control input to the force supplied to the vehicle, to be a strictly proper rational transfer function. It is known that spacing errors due to disturbances amplify if the reference vehicle information is not available to Ω(n) vehicles, n being the size of the collection [1]. In this paper, we generalize this result to show the following: If there are two or more vehicles in the collection that are adjacent to Ω(n) vehicles, then there is a critical size N* so that the motion of the collection will be unstable if the size of the collection exceeds N*. Practical issues of fault tolerance indicate that there be at least two vehicles that are adjacent to Ω(n) vehicles in the collection. We also further show that the use of a kinematic vehicle model for analysis of disturbance propagation yields results which may not agree with what is observed in practice and hence are inappropriate.

An Output Feedback Based Adaptive Robust Fault Tolerant Control Scheme for a Class of Nonlinear Systems

In this paper we present an output feedback based Adaptive Robust Fault Tolerant Control (ARFTC) strategy to solve the problem of output tracking in presence of actuator failures, disturbances and modeling uncertainties for a class of nonlinear systems. The class of faults addressed here include stuck actuators, actuator loss of efficiency or a combination of the two. We assume no a priori information regarding the instant of failure, failure pattern or fault size. The ARFTC combines the robustness of sliding mode controllers with the online learning capabilities of adaptive control to accommodate sudden changes in system parameters due to actuator faults. Comparative simulation studies are carried out on a nonlinear hypersonic aircraft model, which shows the effectiveness of the proposed scheme over back-stepping based robust adaptive fault-tolerant control.

Experimental Investigation Into Improved Wrapper Control of Hot Strip Steel Rolling Mill Downcoilers

With increasing international competition in steel production mainly from developing nations, it is important for steel plants to keep up to date with new technologies, and continuously improve on current practices and manufacturing techniques to remain competitive. This paper looks specifically at improvements to the hot rolling mill downcoilers, which is where the strip is coiled at the end of the rolling process. Hydraulic and pneumatic technology is combined to give accurate position control of guide wrappers that aid the initial coiling process. The paper presents an experimental test rig, using an actual wrapper guide, constructed to evaluate the specific design approach.

Design and Implementation of Dual-Stage Track-Following Control for Hard Disk Drives

This paper discusses the design and implementation of two track-following controllers for dual-stage hard disk drive servo systems. The first controller is designed by combining an outer loop sensitivity-decoupling (SD) controller with an inner loop disturbance observer (DOB). The second is designed by combining mixed H2/H∞ synthesis techniques with an add-on integral action. The designed controllers were implemented and evaluated on a disk drive with a PZT-actuated suspension-based dual-stage servo system. Position error signal (PES) for the servo system was obtained by measuring the slider displacement with an LDV and injecting a simulated track runout.

Variation-Based Transparency Analysis of an Internet-Distributed Hardware-in-the-Loop Simulation Platform for Vehicle Powertrain Systems

Recent work by the authors and colleagues developed an Internet-distributed hardware-in-the-loop simulation (HILS) platform to integrate two geographically-dispersed HILS setups over the Internet, namely, the engine-in-the-loop simulation setup at the University of Michigan (UM) in Ann Arbor, MI, and the driver-in-the-loop ride motion simulator at the US Army Tank-Automotive Research, Development and Engineering Center (TARDEC) in Warren, MI. As the literature discusses in detail, distributing the HILS over the Internet introduces transparency issues due to the delay, jitter, and loss associated with the Internet. This paper first illustrates on a simple example that distributing the simulation can in and of itself be another important source of transparency degradation. Then, the paper presents a variation analysis to evaluate the effect of these two main sources of transparency degradation on the performance of the abovementioned setup. The paper concludes that transparency and how it is affected by distributing the simulation and by the delay, jitter, and loss associated with the Internet is dependent on the signal of interest. Specifically, it is shown that distributing the simulation has more effect on the transparency of the engine torque and throttle signals than the delay, jitter, and loss of the Internet between Ann Arbor and Warren, whereas it does not significantly affect the transparency of vehicle speed unless the Internet delay increases significantly.

Automotive Battery Prognostics Using Dual Extended Kalman Filter

This paper proposes a strategy for estimating the remaining useful life of automotive batteries based on dual Extended Kalman Filter. A nonlinear model of the battery is exploited for the on-line estimation of the State of Charge, and this information is used to evaluate the actual capacity and predict its future evolution, from which an estimate of the remaining useful life is obtained with suitable margins of uncertainty. Simulation results using experimental data from lead-acid batteries show the effectiveness of the approach.

A Novel Automotive Transmission Clutch Control Mechanism

Clutch fill control is critical for automotive transmission performance and fuel economy, including both automatic and hybrid transmissions. To ensure proper function of the transmission systems, it is important to have a precise and robust clutch fill process. Current clutch fill control is realized in an open loop fashion, due to the lack of a pressure or position sensor in the clutch chamber. To improve the accuracy and robustness of this system, a new clutch control mechanism is proposed, which includes an internal feedback structure without a pressure or position sensor. First, the design and working principles of the new mechanism are presented. Second, the advantages of the internal feedback mechanism are analyzed and shown to be superior to the traditional clutch fill mechanism. To this end, the dynamic model of the new mechanism is formulated. Through a series of simulations and case studies, the new clutch control mechanism is demonstrated to be effective, efficient, and robust for solving the clutch fill and engagement control problem.

Virtual Development Environment for Fluid Power Mechatronic Systems

In this paper the results of the German state-funded research project “Fluidtronic”, that deals with a virtual development environment for fluid technical mechatronic systems, is presented. Firstly the conventional development process of a fluid technical mechatronic system is introduced. The conventional development process typically takes a long time because design failures are often only identified during the plant commissioning. Secondly the new virtual development environment, which is worked out in the “Fluidtronic” project is presented. It shows how both the system performance can be optimized and also how the commissioning time can be reduced extensively, if the interactions between mechanical, electrical and fluid power parts are tested at an early point of time in the development process. Optimizations in the development process are realized with the help of new and improved simulation models as well as soft- and hardware in the loop simulations.