J Jurjen Caarls

Saturated control of time-varying formations and trajectory tracking for unicycle multi-agent systems

We propose a synchronization approach to solve a problem where multiple unicycle agents are required to follow individual reference trajectories while maintaining a time-varying formation. Motions of the agents are synchronized thanks to coupling terms in their feedback control laws. Under saturation constraints on the control signals, our control laws guarantee global asymptotic zeroing of the synchronization errors and global asymptotic stability of the tracking error dynamics. For stronger controller couplings, the robustness of formation keeping to perturbations is increased. The proposed approach is successfully validated in experiments.

A Two-Tiered Approach to Self-Localization

This paper describes a two-tiered approach to the self-localization problem for soccer playing robots using generic off-the-shelf color cameras. The solution consists of two layers; the top layer is a global search assuming zero knowledge, and the bottom layer is a local search, assuming a relatively good estimation of the position and orientation of the robot. The global search generally yields multiple candidate positions and orientations, which can be tracked, and assigned a confidence level using the local search and/or historic information.

Collision-free tracking control of unicycle mobile robots

We propose a tracking control with collision avoidance for a group of unicycle mobile robots. A supervisory system assigns to each robot its reference path, together with the desired velocity profile as a function of the position along the path. The robot paths and velocity profiles do not necessarily prevent collisions of the robots. Based on the actual robot coordinates, reference velocities of individual robots are coordinated in real-time such as to ensure collision-free robot movements along the assigned paths. The robot motion controllers realize globally asymptotic stable tracking of the reference trajectories under constraints on the actuator inputs. The controllers proposed here offer several advantages with respect to those in the literature, such as better suppression of tracking errors due to more freedom in controller tuning and relaxed constraints on the reference velocities. The suggested tracking control with collision avoidance has successfully been validated in experiments. It can be used for the realization of autonomous transportation tasks in warehouses, harbors, factories, etc.

A Holonic Approach to Warehouse Control

Warehouses play a critical role in the distribution of products of many suppliers to many customers. Traditionally, warehouse operations are controlled by centralised control systems. Because of increasing customer demands, the complexity of such systems becomes too large to respond optimally to all warehouse events. Holonic control systems try to overcome this limitation. This paper presents a framework that supports the development of holonic warehouse control systems. The framework, which is built on top of JADE middleware, allows a holonic control system to be generated from a warehouse layout model and a library of reusable behaviour components. The architecture of the framework and an example of its application to an existing warehouse are presented.

Flexible Transportation in Warehouses

In recent years, autonomous mobile robots (AMR) have emerged as a means of transportation system in warehouses. The complexity of the transport tasks requires efficient high-level control, i.e. planning and scheduling of the tasks as well as low-level motion control of the robots. Hence, an efficient coordination between robots is needed to achieve flexibility, robustness and scalability of the transportation system. In this chapter, we present a methodology to achieve coordination in different control layers, namely high-level and low-level coordination. We investigate how the coordination strategies perform in an automated warehouse. We use simulation results to analyse the system performance. We take into account typical performance indicators for a warehouse, such as time to accomplish the transportation tasks and total cost of the system. In addition to the simulation results, we conduct experiments in a small-scale representation of the warehouse.

Warehouse Simulation Through Model Configuration

The pre-build development of warehouse systems leads from a specific customer request to a specific customer quotation. This involves a process of configuring a warehouse system using a sequence of steps that contain increasingly more details. Simulation is a helpful tool in analyzing warehouse design alternatives, but setting up a detailed simulation is too expensive early in the development process. We show that configurable simulation models can be applied early in the development process with a good cost/benefit ratio. We present a warehouse simulation model that can be configured with customer and topology information and decision algorithms. We show that the simulation results are similar to those of detailed simulations while a warehouse simulation can be configured with little effort and the simulations run fast enough to support sensitivity analysis and design-space exploration.