Jacques Penders

A Robot Swarm assisting a Human Fire Fighter

Emergencies in industrial warehouses are a major concern for fire-fighters. The large dimensions, together with the development of dense smoke that drastically reduces visibility, represent major challenges. The GUARDIANS robot swarm is designed to assist fire-fighters in searching a large warehouse. In this paper we discuss the technology developed for a swarm of robots assisting fire-fighters. We explain the swarming algorithms that provide the functionality by which the robots react to and follow humans while no communication is required. Next we discuss the wireless communication system, which is a so-called mobile ad-hoc network. The communication network provides also the means to locate the robots and humans. Thus, the robot swarm is able to provide guidance information to the humans. Together with the fire-fighters we explored how the robot swarm should feed information back to the human fire-fighter. We have designed and experimented with interfaces for presenting swarm-based information to human beings.

Mixed human-robot team navigation in the GUARDIANS project

A theoretical framework for generating navigation behaviour patterns in mixed human-robot groups in complex environments is proposed. This framework represents an essential part in the development of a multiple robot-human system for assisting fire-fighters in search and rescue operations in the GUARDIANS project. In order to produce the desired behaviours an artificial potential field method has been developed. We distinguish a three classes of agents: robots, humans and obstacles, and apply different potential functions to them. Depending on the situation, we switch from one function to another; this allows to generate desired behaviour patterns as well as to avoid certain local minima. Typical behaviour patterns are singled out and their stability is discussed. Stability analysis is based on geometric considerations, that permits to avoid bulky computations and provide graphic demonstrations of convergence. The proposed framework can be used in other robotic applications where a group of heterogenous agents is deployed.

An experiment on squad navigation of human and robots

Mobile robots are nowadays capable of navigating in a semi-structured environment, either alone or in formations. Dealing with mobile obstacles, e.g. persons, in everyday environments poses additional challenges which are being addressed by the research community. This paper presents an experiment with a set of robots -acting as a swarm- and one person. The aim of such robot-human squad is to explore an unmapped area indoors. The swarm is programmed such that obstacle avoidance, robot avoidance and human avoidance is combined with staying in the vicinity of the human and gradually proceeding towards the end point. The robots are provided with enough sensors to perform avoidance, and determine/estimate the distance to the human. Communication is one-way only, from robots to human. The aim of the experiment is to provide insights about the real problems of the multirobot system when dealing with a non-expert person in a cooperative exploration task.

Salient Feature of Haptic-Based Guidance of People in Low Visibility Environments Using Hard Reins

This paper presents salient features of human-human interaction where one person with limited auditory and visual perception of the environment (a follower) is guided by an agent with full perceptual capabilities (a guider) via a hard rein along a given path. We investigate several salient features of the interaction between the guider and follower such as: 1) the order of an autoregressive (AR) control policy that maps states of the follower to actions of the guider; 2) how the guider may modulate the pulling force in response to the trust level of the follower; and 3) how learning may successively apportion the responsibility of control across different muscles of the guider. Based on experimental systems identification on human demonstrations from ten pairs of naive subjects, we show that guiders tend to adopt a third-order AR predictive control policy and followers tend to adopt second-order reactive control policy. Moreover, the extracted guiders control policy was implemented and validated by human-robot interaction experiments. By modeling the followers dynamics with a time varying virtual damped inertial system, we found that it is the coefficient of virtual damping which is most sensitive to the trust level of the follower. We used these experimental insights to derive a novel controller that integrates an optimal order control policy with a push/pull force modulator in response to the trust level of the follower monitored using a time varying virtual damped inertial model.

Privacy in (mobile) Telecommunications Services

Telecommunications services are for long subject to privacy regulations. At stake are traditionally: privacy of the communication and the protection of traffic data. Privacy of the communication is legally founded. Traffic data subsume under the notion of data protection and are central in the discussion. The telecommunications environment is profoundly changing. The traditionally closed markets with closed networks change into an open market with open networks. Within these open networks more privacy sensitive data are generated and have to be exchanged between growing numbers of parties. Also telecommunications and computer networks are rapidly being integrated and thus the distinction between telephony and computing disappears. Traditional telecommunications privacy regulations are revised to cover internet applications. In this paper telecommunications issues are recalled to aid the on-going debate. Cellular mobile phones have recently be introduced. Cellular networks process a particular category of traffic data namely location data, thereby introducing the issue of territorial privacy into the telecommunications domain. Location data are bound to be used for pervasive future services. Designs for future services are discussed and evaluated for their impact on privacy protection.

Challenges of the Multi-robot Team in the GUARDIANS Project

The Guardians multi-robot team is being designed to be deployed in a large warehouse to assist firefighters in the event or danger of a fire. The large size of the environment together with development of dense smoke that drastically reduces visibility, represent major challenges in search and rescue operations. The GUARDIANS robots act alongside a firefighter and should provide, among others, the following tasks: to guide or accompany the firefighters on the site while indicating possible obstacles and locations of danger and maintaining communications links. In order to fulfill the aforementioned tasks the robots need to be able to exert certain behaviours. Among the basic behaviours are capabilities to unite in a group - generate a formation - and navigate on the site while keeping this formation. The basic control model used to generate these behaviours is based on the so-called social potential field framework, which we adapt to fulfill specific tasks of the Guardians scenario. All of the tasks can be achieved without central control, and some of the tasks can be performed even without explicit communication among the robots. We discuss advantages and shortcomings of our model and present samples of implementation on ERA-MOBI robots, commonly referred to as Erratics.

Experiments in cooperative human multi-robot navigation

In this paper, we consider the problem of a group of autonomous mobile robots and a human moving coordinately in a real-world implementation. The group moves throughout a dynamic and unstructured environment. The key problem to be solved is the inclusion of a human in a real multi-robot system and consequently the multiple robot motion coordination. We present a set of performance metrics (system efficiency and percentage of time in formation) and a novel flexible formation definition whereby a formation control strategy both in simulation and in real-world experiments of a human multi-robot system is presented. The formation control proposed is stable and effective by means of its uniform dispersion, cohesion and flexibility.

Towards Autonomous Robotic Systems

Robot with non-back-drivable actuators will appear stiff when in contact with the environment and human. This scenario is unsafe for the Human-Robot Interaction (HRI). In order to guarantee safety in HRI, the robot will be made “soft” such that a compliant control can be introduced. Apart from utilizing the proper mechanism design, the back drivability actuators can be achieved by a suitable choice of control. In particular, in this paper, a PID control is employed to achieve an active compliance control. The reference impedance model characteristics are exploited for which the system allows us to introduce a virtual mass-spring-damper system to adjust the compliant control level. The performance of the PID control will be tested on the RED Hand in the simulation. The results are recorded and analyzed for the thumb finger. The results show that the PID controller is capable of controlling the motion and position of the RED Hand. In addition, the compliance behavior for the RED Hand can be suitably adjusted based on the required compliant level.

An approach to multi-robot site exploration based on principles of self-organisation

This paper presents a novel approach to multi-robot site exploration and map building considering the robot team as a self-organising system. The approach has been developed within the framework of the project GUARDIANS. The Map Building process represents not a separate activity, but an inherent byproduct of self-organisation. The system consists of an (heterogeneous) robot swarm, a mobile ad-hoc network and an (evolving) topological map of the environment. The proposed map building approach takes advantage of a cooperating robot team (as opposed to a single robot) allowing accurate deployment and localisation in a structured, yet dynamic manner. A topological graph representation of the environment is formed, from which an initial metric representation is elicitable as edges are assigned lengths. This reasonable sketch of the environment can be further developed to a full metric map and be used as the basis of building ad-hoc mobile wireless communication and sensor networks. The presented algorithms also take into consideration sensor limitation and are tested on a group of Khepera III robots, specially upgraded to fulfil the needs of our approach.

Experimental study on the effects of communication range on cooperative robotic search in complex environments

Communication has an important role in multi-robot systems. It can facilitate cooperation, therefore, improve the performance of the system significantly. In this study we investigated the benefits of networked communication by experimentally evaluating the results of two search algorithms which are spiral search and informed random search. The experiments were performed in an experimental area containing obstacles and using e-puck robots where the communication ranges were ldquosimulatedrdquo with the help of an overhead camera. Each robot was allowed to (i) keep an occupancy grid based local map of the environment containing also information about the cells it has visited and (ii) exchange this information with the other robots within its communication range. The effect of the size of communication range on the performance of the system defined as the time of completion of the search task (i.e, locating the target), was investigated.