Andreas Hertle

Planning with semantic attachments: an object-oriented view

In recent years, domain-independent planning has been applied to a rising number of real-world applications. Usually, the description language of choice is PDDL. However, PDDL is not suited to model all challenges imposed by real-world applications. Dornhege et al. proposed semantic attachments to allow the computation of Boolean fluents by external processes called modules during planning. To acquire state information from the planning system a module developer must perform manual requests through a callback interface which is both inefficient and error-prone. In this paper, we present the Object-oriented Planning Language OPL, which incorporates the structure and advantages of modern object-oriented programming languages. We demonstrate how a domain-specific module interface that allows to directly access the planner state using object member functions is automatically generated from an OPL planning task. The generated domain-specific interface allows for a safe and less error-prone implementation of modules. We show experimentally that this interface is more efficient than the PDDL-based module interface of TFD/M.

Community-driven development of standard software modules for search and rescue robots

The main goal of the paper is to continuously enlarge the set of software building blocks that can be reused in the search and rescue domain.

Multirobot Coverage Search in Three Dimensions

Searching for objects and observing parts of a known environment efficiently is a fundamental problem in many real-world robotic applications, e.g., household robots searching for objects, inspection robots searching for leaking pipelines, and rescue robots searching for survivors after a disaster. We consider the problem of identifying and planning sequences of sensor locations from which robot sensors can observe and cover complex three-dimensional 3D environments while traveling only short distances. Our approach is based on sampling and ranking a large number of sensor locations for a 3D environment represented by an OctoMap. The visible area from these sensor locations induces a minimal partition of the 3D environment that we exploit for planning sequences of sensor locations with short travel times efficiently. We present multiple planning algorithms designed for single robots and for multirobot teams. These algorithms include variants that are greedy, optimal, or based on decomposing the planning problem into a set cover and traveling salesman problem. We evaluated and compared these algorithms empirically in simulation and real-world robot experiments with up to four robots. Our results demonstrate that, despite the intractability of the overall problem, computing and executing effective solutions for multirobot coverage search in real 3D environments is feasible and ready for real-world applications.

Mobile manipulation in cluttered environments with humanoids: Integrated perception, task planning, and action execution

To autonomously carry out complex mobile manipulation tasks, a robot control system has to integrate several components for perception, world modeling, action planning and replanning, navigation, and manipulation. In this paper, we present a modular framework that is based on the Temporal Fast Downward Planner and supports external modules to control the robot. This allows to tightly integrate individual sub-systems with the high-level symbolic planner and enables a humanoid robot to solve challenging mobile manipulation tasks. In the work presented here, we address mobile manipulation with humanoids in cluttered environments, particularly the task of collecting objects and delivering them to designated places in a home-like environment while clearing obstacles out of the way. We implemented our system for a Nao humanoid tidying up a room, i.e., the robot has to collect items scattered on the floor, move obstacles out of its way, and deliver the objects to designated target locations. Despite the limited sensing and motion capabilities of the low-cost platform, the experiments show that our approach results in reliable task execution by applying monitoring actions to verify object and robot states.

An Experimental Comparison of Classical, FOND and Probabilistic Planning

Domain-independent planning in general is broadly applicable to a wide range of tasks. Many formalisms exist that allow the description of different aspects of realistic problems. Which one to use is often no obvious choice, since a higher degree of expressiveness usually comes with an increased planning time and/or a decreased policy quality. Under the assumption that hard guarantees are not required, users are faced with a decision between multiple approaches. As a generic model we use a probabilistic description in the form of Markov Decision Processes (MDPs). We define abstracting translations into a classical planning formalism and fully observable nondeterministic planning. Our goal is to give insight into how state-of-the-art systems perform on different MDP planning domains.

Efficient extensible path planning on 3D terrain using behavior modules

We present a search-based path planning system for ground robots on three dimensional terrain. Effectively negotiating such terrain often requires to utilize dedicated robot hardware and to execute specific behaviors. Our base system is independent from the actual robot configuration, but can be customized to a robots abilities. We explicitly plan using a full 3d representation, not requiring any projection or slicing to a 2d world. The drivable surface manifold is automatically extracted from the volumetric 3d representation and generic motions are planned on these surface cells. This is achieved with behavior modules that integrate robot skills with the search. Such a behavior module is responsible for defining traversable surfaces, computing if a motion can be executed, and its cost. We implement two such modules: One for sloped ground and ramps, and one for steps and stairs. The approach is evaluated on simulated real-world environments.

Efficient Auction Based Coordination for Distributed Multi-agent Planning in Temporal Domains Using Resource Abstraction.

Recent advances in mobile robotics and AI promise to revolutionize industrial production. As autonomous robots are able to solve more complex tasks, the difficulty of integrating various robot skills and coordinating groups of robots increases dramatically. Domain independent planning promises a possible solution. For single robot systems a number of successful demonstrations can be found in scientific literature. However our experiences at the RoboCup Logistics League in 2017 highlighted a severe lack in plan quality when coordinating multiple robots. In this work we demonstrate how out of the box temporal planning systems can be employed to increase plan quality for temporal multi-robot tasks. An abstract plan is generated first and sub-tasks in the plan are auctioned off to robots, which in turn employ planning to solve these tasks and compute bids. We evaluate our approach on two planning domains and find significant improvements in solution coverage and plan quality.