Erjen Lefeber

Tracking control of an underactuated ship

In this paper, we address the tracking problem for an underactuated ship using two controls, namely surge force and yaw moment. A simple state-feedback control law is developed and proved to render the tracking error dynamics globally K- exponentially stable. Experimental results are presented where the controller is implemented on a scale model of an offshore supply vessel.

Saturated stabilization and tracking of a nonholonomic mobile robot

This paper presents a framework to deal with the problem of global stabilization and global tracking control for the kinematic model of a wheeled mobile robot in the presence of input saturations. A model-based control design strategy is developed via a simple application of passivity and normalization. Saturated, Lipschitz continuous, time-varying feedback laws are obtained and illustrated in a number of compelling simulations. c 2001 Elsevier Science B.V. All rights reserved.

Way-point tracking control of ships

The paper considers way-point tracking control of ships using yaw torque control. A full state feedback control law is developed using a cascaded approach, and proved to globally asymptotically stabilize the heading and the cross-track error of the ship. Simulation results are presented.

Exponential tracking control of a mobile car using a cascaded approach

Abstract In this paper we address the problem of designing simple global tracking controllers for a kinematic model of a mobile robot and a simple dynamic model of a mobile robot. For this we use a cascaded systems approach, resulting into linear controllers that yield global K-exponential stability of the closed loop system.

Output Feedback Tracking of Ships

In this brief, we consider output feedback tracking of ships with position and orientation measurements only. Ship dynamics are highly nonlinear, and for tracking control, as opposed to dynamic positioning, these nonlinearities have to be taken into account in the control design. We propose an observer-controller scheme which takes into account the complete ship dynamics, including Coriolis and centripetal forces and nonlinear damping, and results in a semi-globally uniformly stable closed-loop system. Furthermore, a gain tuning procedure for the observer-controller scheme is developed. Experimental results are presented where the observer-controller scheme is implemented onboard a Froude scaled 1:70 model supply ship. The experimentally obtained results are compared with simulation results under ideal conditions and both support the theoretical results on semi-global exponential stability of the closed-loop system.

Linear controllers for exponential tracking of systems in chained-form

In this paper we address the tracking problem for a class of non-holonomic chained-form control systems. We present a simple solution for both the state feedback and the dynamic output feedback problem. The proposed controllers are linear and render the tracking error dynamics globally K-exponentially stable. We also deal with both control problems under input saturation. Application of the results to the control of wheeled mobile robots is illustrated by means of simulations of a car pulling a single trailer.

Robust cyclic berth planning of container vessels

We consider a container terminal operator who faces the problem of constructing a cyclic berth plan. Such a plan defines the arrival and departure times of each cyclically calling vessel on a terminal, taking into account the expected number of containers to be handled and the necessary quay and crane capacity to do so. Conventional berth planning methods ignore the fact that, in practice, container terminal operator and shipping line agree upon an arrival window rather than an arrival time: if a vessel arrives within that window then a certain vessel productivity and hence departure time is guaranteed. The contributions of this paper are twofold. We not only minimize the peak loading of quay cranes in a port, but also explicitly take into account the arrival window agreements between the terminal operator and shipping lines. We present a robust optimization model for cyclic berth planning. Computational results on a real-world scenario for a container terminal in Antwerp show that the robust planning model can reach a substantial reduction in the crane capacity that is necessary to meet the window arrival agreements, as compared to a deterministic planning approach.

Feedback control of 2-product server with setups and bounded buffers

A manufacturing machine processing two product types arriving at constant rate and setup times involved is considered in this study. An optimal process cycle is derived with respect to minimal weighted time averaged work in process (wip) level. In addition, a feedback law is proposed that steers the system to this optimal process cycle from arbitrary start point. The analysis has been done for both unbounded and bounded buffer capacity. Although the analysis is done for continuous models, the feedback law has been implemented successfully in a discrete event simulation

Simultaneous berth allocation and yard planning at tactical level

We present a simultaneous berth allocation and yard planning problem at tactical level, since the berth allocation has a great impact on the yard planning and vice versa. This problem is solved by means of an alternating berth and yard planning heuristic approach. The alternating heuristic quickly converges to a local minimum which heavily depends on the starting point. Therefore, we formulate another optimization problem for generating a suitable starting point. A real size case study provided by PSA Antwerp shows that our approach to simultaneously solve both problems might reduce the total straddle carrier travel distance considerably as compared with a representative allocation.

Controlling a re-entrant manufacturing line via the push-pull point

A reduced model of a re-entrant semiconductor factory exhibiting all the important features is simulated, applying a push dispatch policy at the beginning of the line and a pull dispatch policy at the end of the line. A commonly used dispatching policy that deals with short-term fluctuations in demand involves moving the transition point between both policies, the push–pull point (PPP) around. It is shown that with a mean demand starts policy, moving the PPP by itself does not improve the performance of the production line significantly over policies that use a pure push or a pure pull dispatch policy, or a CONWIP starts policy with pure pull dispatch policy. However, when the PPP control is coupled with a CONWIP starts policy, then for high demand with high variance, the improvement becomes approximately a factor of 4. The unexpected success of a PPP policy with CONWIP is explained using concepts from fluid dynamics that predict that this policy will not work for perishable demand. The prediction is verified through additional simulations.