Abstract In this paper, we consider the single‐commodity robust network design problem. Given an undirected graph with capacity installation costs on its edges and a set of scenarios with associated flow balance vectors that represent different scenarios of node supplies and demands, the goal is to find integer edge capacities that minimize the total installation cost and permit a feasible single commodity flow for each scenario. This problem arises, for example, in the design of power networks, which are dimensioned to accommodate many different load scenarios. We propose a new method to identify a small subset of the given scenarios, such that solving the robust network design problem for the smaller scenario set leads to almost the same capacities as solving it for the full scenario set . By considering only the scenarios in , the size of the model that needs to be solved can be reduced substantially, while the error introduced by neglecting the remaining scenarios is kept very small. Our method only employs simple techniques from statistical data analysis, namely principal component analysis (PCA), and convex hull computations in low dimensions. Thus, its computational effort is very small and it is easily applicable to more complex network design problems. We evaluate the effectiveness of the method in computational experiments for instances stemming from offshore power grid planning and telecommunication networks. Our results show that the proposed techniques are indeed well suited to identify small scenario subsets that lead to significantly reduced models with high quality solutions.

In this paper, we present a system for socially aware robot navigation for a wide range of service tasks in supermarkets. It comprises modules for real-time person detection and tracking to gain situation awareness, modules to react to situations, and means for human-robot communication. The technical performance of the situation awareness was evaluated in a shelf out-of-stock (SOOS) detection scenario under real-world conditions in a supermarket in Germany. Furthermore, in order to investigate whether and to what extent our social navigation strategy can improve the acceptance and application of a mobile service robot in a supermarket, we have conducted surveys with N = 60 participants and usability tests with N =8 participants during a three-day field test. We can show that a robot for SOOS detection operating in a supermarket during the opening hours is generally accepted by customers and that the integration of a real-time person perception is crucial, especially for keeping appropriate distances to persons and for improving user-centered communication. Furthermore, our results indicate that various communication channels (e.g. speech, a video projector, and LED lights) are beneficial in order to address a wider user group in the targeted supermarket setting.

This paper introduces a novel robot-based approach to the stroke rehabilitation scenario, in which a mobile robot companion accompanies stroke patients during their walking self-training. This assistance enables them to move freely in the clinic practicing both their mobility and spatial orientation skills. Based on a set of questions for systematic evaluating the autonomy and practicability of assistive robots and a three-stage approach in conducting function and user tests in the clinical setting, we present the results of user trials performed with N=30 stroke patients in a stroke rehabilitation center between 4/2015 and 3/2016. This allowed us to make an honest inventory of the strengths and weaknesses of the developed robot companion and its already achieved practicability for clinical use. The results of the user studies show that patients and fellow patients were very open-minded and accepted the robotic coach. The robot motivated them for independent training and leaving their room, despite severe consequences of stroke (lower limbs paralysis, speech/language problems, loss of orientation, depression), provided a very self-determined training regime, and encouraged them to expand the radius of their training in the clinic.

In this article, we consider the Node‐Weighted Dominating Steiner Problem. Given a graph with node weights and a set of terminal nodes, the goal is to find a connected node‐induced subgraph of minimum weight, such that each terminal node is contained in or adjacent to some node in the chosen subgraph. The problem arises in applications in the design of telecommunication networks. Integer programming formulations for Steiner problems usually employ a variable for each edge. We introduce a formulation that only uses node variables and that models connectivity through node‐cut inequalities, which can be separated in polynomial time. We discuss necessary and sufficient conditions for the model inequalities to define facets and we introduce a class of lifted partition‐based inequalities, which can be used to strengthen the linear relaxation. Finally, we show that the polyhedron defined by these inequalities is integral if the underlying graph is a cycle where no two terminals are adjacent. In the general cycle setting, we show that we can get a complete description of the feasible solutions by lifting and projecting into a polytope with no more than twice the dimension. We also show that the well‐known indegree equalities are implied by the lifted partition inequalities. Finally, we evaluate the effectiveness of the presented partition inequalities in computational experiments. © 2016 Wiley Periodicals, Inc. NETWORKS, Vol. 69(1), 33–51 2017

As report on work in progress, this paper describes the objectives and the current state of implementation of the ongoing research project ROREAS (Robotic Rehabilitation Assistant for Stroke Patients), which aims at developing a robotic rehabilitation assistant for walking and orientation exercising in self-training during clinical stroke follow-up care. This requires strongly user-centered, polite and attentive social navigation and interaction behaviors that can motivate the patients to start, continue, and regularly repeat their self-training. Against this background, the paper gives an overview of the constraints and requirements arising from the rehabilitation scenario and the operational environment, a heavily populated multi-level rehabilitation center, and presents the robot platform ROREAS which is currently used for developing the demonstrators (walking coach and orientation coach). Moreover, it gives an overview of the robot's functional system architecture and presents selected advanced navigation and HRI functionalities required for a personal robotic trainer that can successfully operate in such a challenging real-world environment, up to the results of ongoing functionality tests and upcoming user studies.

This paper presents results of user evaluations with a socially assistive robot companion for older people suffering from mild cognitive impairment (MCI) and living (alone) at home. Within the European FP7 project “CompanionAble” (2008-2012) [1], we developed assistive technologies combining a mobile robot and smart environment with the aim to support these people and assist them living in their familiar home environment. For a final evaluation, user experience studies were conducted with volunteer users who were invited to a test home where they lived and freely used the robot and integrated system over a period of two days. Services provided by the companion robot include reminders of appointments (pre-defined or added by the users themselves or their informal carer) as well as frequent recommendations to specific activities, which were listed e.g. by their family carers. Furthermore, video contact with relatives and friends, a cognitive stimulation game designed especially to counter the progress of cognitive impairments, and the possibility to store personal items with the robot are offered. Recognition of the user entering or leaving the home is triggering situation specific reminders like agenda items due during the (expected) absence, missed calls or items not to be forgotten. Continuing our previous work published in [2], this paper presents detailed description of the implemented assistive functions and results of user studies conducted during April and May 2012 in the smart house of the Dutch project partner Smart Homes in Eindhoven, The Netherlands.

This paper presents results of the development of a socially assistive home robot companion for older people suffering from mild cognitive impairment (MCI) and living (alone) at home. This work was part of the European FP7 project “CompanionAble” (2008-2012) [1] which aimed at developing assistive technologies that can support these elderly and help them to remain in their familiar living environment for as long as possible. To overcome current market entry barriers, from the start we consistently adopted a user- and application-centered development process of the companion robot and focused on three main aspects: (i) the realization of a set of mandatory functionalities to support care recipients and caregivers, (ii) a strict design and usability driven realization to increase the acceptance of the robot by the different end-user groups (the elderly, their relatives, and caregivers), and (iii) the development and component selection considering production and operational costs. In continuation of the work presented in [2], this paper describes the final implementation of the companion robot and presents latest results of functional tests and early findings of user studies recently conducted in the smart house of the Dutch project partner Smart Homes in Eindhoven, The Netherlands.

The paper is addressing several aspects of our work as part of the European FP7 project ¿CompanionAble¿ and gives an overview of the progress in developing a socially assistive home robot companion for elderly people with mild cognitive impairment (MCI) living alone at home. The spectrum of required assistive functionalities and services that have been specified by the different end-user target groups of such a robot companion (the elderly, relatives, caregivers) is manifold. It reaches from situation-specific, intelligent reminding (e.g. taking medication or drinking) and cognitive stimulation, via mobile videophony with relatives or caregivers, up to the autonomous detection of dangerous situations, like falls, and their evaluation by authorized persons via mobile telepresence. From the beginning, our approach has been focused on long-term and everyday suitability and low-cost producibility as important prerequisites for the marketability of the robot companion. Against this background, the paper presents the main system requirements derived from user studies, the consequences for the hardware design and functionality of the robot companion, its system architecture, a key technology for HRI in home environments - the autonomous user tracking and searching, up to the results of already conducted and ongoing functionality tests and upcoming user studies.

The paper gives an overview of the progress in developing a socially assistive home robot companion for elderly people with mild cognitive impairment (MCI) living alone at home. The spectrum of required assistive functionalities of such a robot companion is broad and reaches from reminding functions (e.g. taking medication or drinking) and cognitive stimulation exercises, via mobile videophony with relatives or caregivers, up to the detection and evaluation of critical situations, like falls. The paper is addressing several aspects of our work as part of the European FP7 project “CompanionAble”, as for example the developed robot hardware and its software and control architecture, the implemented skills for robust user detection and tracking and user-centered navigation in the home environment, and reports on already conducted and still ongoing functionality testings and pending usability studies with the end-user target groups (the elderly, relatives, caregivers).

The paper gives a comprehensive overview of our Shopping Guide project, which aims at the development of interactive mobile shopping companion robots for everyday use in challenging operating environments such as home improvement stores. It is spanning an arc from the expectations and requirements of store owners and customers, via the challenges of the shopping scenario and the operating environment, the implemented functionality of the shopping guide robots, up to the results of long-term field trials. The field trials started in April 2008 and still ongoing aim at studying whether and how a group of interactive mobile shopping guide robots can operate completely autonomously in such everyday environments and how they are accepted by uninstructed customers. In these field trials, where nine robotic shopping guides traveled together 2187 kilometers in three different home improvement stores in Germany, more than 8,600 customers were successfully guided to the locations of their products of choice. With the successful development of these shopping guide robots, a further important step towards assistive robotics for daily use has been done.

Abstract In this article, we discuss the relation of unsplittable shortest path routing (USPR) to other routing schemes and study the approximability of three USPR network planning problems. Given a digraphD= (V,A) and a setKof directed commodities, an USPR is a set of flow pathsP , (s,t) ∈K, such that there exists a metric λ = (λa) ∈Z with respect to which eachP is the unique shortest (s,t)‐path. In the Min‐Con‐USPR problem, we seek an USPR that minimizes the maximum congestion over all arcs. We show that this problem is NP‐hard to approximate within a factor ofO(|V|1−ϵ), but polynomially approximable within min(|A|,|K|) in general and withinO(1) if the underlying graph is an undirected cycle or a bidirected ring. We also construct examples where the minimum congestion that can be obtained by USPR is a factor of Ω(|V|2) larger than that achievable by unsplittable flow routing or by shortest multipath routing, and a factor of Ω(|V|) larger than that achievable by unsplittable source‐invariant routing. In the CAP‐USPR problem, we seek a minimum cost installation of integer arc capacities that admit an USPR of the given commodities. We prove that this problem is NP‐hard to approximate within 2 − ϵ even in the undirected case, and we devise approximation algorithms for various special cases. The fixed charge network design problem FC‐USPR, where the task is to find a minimum cost subgraph ofDwhose fixed arc capacities admit an USPR of the commodities, is shown to be NPO‐complete. All three problems are of great practical interest in the planning of telecommunication networks that are based on shortest path routing protocols. Our results indicate that they are harder than the corresponding unsplittable flow or shortest multi‐path routing problems. © 2009 Wiley Periodicals, Inc. NETWORKS, 2009

The paper describes progress achieved in our long-term research project ShopBot, which aims at the development of an intelligent and interactive mobile shopping assistant for everyday use in shopping centers or home improvement stores. It is focusing on recent progress concerning two important methodological aspects: (i) the on-line building of maps of the operation area by means of advanced Rao-Blackwellized SLAM approaches using both sonar-based gridmaps as well as vision-based graph maps as representations, and (ii) a probabilistic approach to multi-modal user detection and tracking during the guidance tour. Experimental results of both the map building characteristics and the person tracking behavior achieved in an ordinary home improvement store demonstrate the reliability of both approaches. Moreover, we present first very encouraging results of long-term field trials which have been executed with three robotic shopping assistants in another home improvement store in Bavaria since March 2008. In this field test, the robots could demonstrate their suitability for this challenging real-world application, as well as the necessary user acceptance.

Abstract We study the complexity of two inverse shortest paths (ISP) problems with integer arc lengths and the requirement for uniquely determined shortest paths. Given a collection of paths in a directed graph D = (V, A), the task is to find positive integer arc lengths such that the given paths are uniquely determined shortest paths between their respective terminals. In the first problem we seek for arc lengths that minimize the length of the longest of the prescribed paths. In the second problem, the length of the longest arc is to be minimized. We show that it is 𝒩𝒫‐hard to approximate the minimal longest path length within a factor less than 8/7 or the minimal longest arc length within a factor less than 9/8. This answers the (previously) open question whether these problems are 𝒩𝒫‐hard or not. We also present a simple algorithm that achieves an 𝒪(∣V∣)‐approximation guarantee for both variants. Both ISP problems arise in the planning of telecommunication networks with shortest path routing protocols. Our results imply that it is 𝒩𝒫‐hard to decide whether a given path set can be realized with a real shortest path routing protocol such as OSPF, IS‐IS, or RIP. © 2007 Wiley Periodicals, Inc. NETWORKS, Vol. 50(1), 29–36 2007