Decisional autonomy of planetary rovers

Abstract

To achieve the ever increasing demand for science return, planetary exploration rovers require more autonomy to successfully perform their missions. Indeed, the communication delays are such that teleoperation is unrealistic. Although the current rovers (such as MER) demonstrate a limited navigation autonomy, and mostly rely on ground mission planning, the next generation (e.g. NASA Mars Science Laboratory and ESA Exomars) will have to regularly achieve long range autonomous navigation tasks.However, fully autonomous long range navigation in partially known planetary-like terrains is still an open challenge for robotics. Navigating hundreds of meters without any human intervention requires the robot to be able to build adequate representations of its environment, to plan and execute trajectories according to the kind of terrain traversed, to control its motions and to localize itself as it moves.All these activities have to be planned, scheduled, and performed according to the rover context, and controlled so that the mission is correctly fulfilled. To achieve these objectives, we have developed a temporal planner and an execution controller, that exhibit plan repair and replanning capabilities. The planner is in charge of producing plans composed of actions for navigation, science activities (moving and operating instruments), communication with Earth and with an orbiter or a lander, while managing resources (power, memory, etc) and respecting temporal constraints (communication visibility windows, rendezvous, etc). High level actions also need to be refined and their execution temporally and logically controlled. Last, in such critical applications, we believe it is important to deploy a component which protects the system against dangerous or even fatal situations resulting from unexpected interactions between subsystems (e.g. move the robot while the robot arm is unstowed) and/or software components (e.g. take and store a picture in a buffer while the previous one is still being processed).In this article we review the aforementioned capabilities, that have been developed, tested and evaluated on board our rovers (Lama and Dala). After an overview of the architecture design principle adopted, we summarize the perception, localization and motion generation capabilities -required by autonomous navigation -and their integration and concurrent operation in a global architecture. We then detail the decisional components : a high level temporal planner which produces the robot activity plan on board, and temporal and procedural execution controllers. We show how some failures or execution delays are being taken care of with online local repair, or replanning.

Mission Operations and Autonomy

“…One example being a threetiered software architecture designed for planetary rovers by LAAS-CNRS [21]. This design uses a distributed set of nonhomogeneous processes to perform realtime event-based or task-based control loops, with three levels of abstraction.…”

Robotics and artificial intelligence: A perspective on deliberation functions

“…Some planning capabilities have been added to PRS [21] to anticipate paths leading to execution failure. PRS is used on various robotics platforms to trigger commands, e.g., through GenoM functional modules services [45].…”

“…[5], which rely on them to implement deliberative functions. • Hierarchical architectures are probably the most widely used in robotics [22,45,75]. They propose an organization of the software along layers (two or three) with different temporal requirements and abstraction levels.…”

Off-road Robotics—An Overview

“…The concepts and technologies developed within the scope of off-road robotics can be applied in many different fields, including the agricultural [81,103], construction [89], and forestry [10,39] sectors as well as space exploration [49,88,93], search and rescue operations [70], humanitarian demining [8], and the military domain [23,44,90,107].…”