TML: a language to specify aerial robotic missions for the framework Aerostack

TLDR: The experiments proved that the TML language is easy to use and expressive enough to formulate adaptive missions in dynamic environments, and showed thatThe TML interpreter is efficient to execute multi-robot aerial missions and reusable for different platforms.

Abstract: Purpose The purpose of this paper is to describe the specification language TML for adaptive mission plans that the authors designed and implemented for the open-source framework Aerostack for aerial robotics. Design/methodology/approach The TML language combines a task-based hierarchical approach together with a more flexible representation, rule-based reactive planning, to facilitate adaptability. This approach includes additional notions that abstract programming details. The authors built an interpreter integrated in the software framework Aerostack. The interpreter was validated with flight experiments for multi-robot missions in dynamic environments. Findings The experiments proved that the TML language is easy to use and expressive enough to formulate adaptive missions in dynamic environments. The experiments also showed that the TML interpreter is efficient to execute multi-robot aerial missions and reusable for different platforms. The TML interpreter is able to verify the mission plan before its execution, which increases robustness and safety, avoiding the execution of certain plans that are not feasible. Originality/value One of the main contributions of this work is the availability of a reliable solution to specify aerial mission plans, integrated in an active open-source project with periodic releases. To the best knowledge of the authors, there are not solutions similar to this in other active open-source projects. As additional contributions, TML uses an original combination of representations for adaptive mission plans (i.e. task trees with original abstract notions and rule-based reactive planning) together with the demonstration of its adequacy for aerial robotics.

Figures

Figure 3: Block diagram of the processes used to execute mission plans formulated in TML language.

Figure 6: Example of the Aerostack user interface showing dynamically the movement of one of the two drones. The red line shows a planned trajectory. The black line corresponds to the actual flight.

Figure 1: An example of task tree with actions and skills. Ellipses represent tasks, rectangles represent actions and rounded rectangles represent skills.

Table 2. Example functions used in the verification model.

Figure 8: Example of inter-process communication developed in the experiment.

Figure 5: Demonstrative mission where two drones search in an autonomous flight for a hidden subject in a spatial area with unknown obstacles. Visual markers (ArUco) are used by the drones for self-positioning, obstacle detection and subject detection.

Frequently asked questions

Q1. What contributions have the authors mentioned in the paper "Tml: a language to specify aerial robotic missions for the framework aerostack" ?

The main purpose of this paper is to describe the specification language TML for adaptive mission plans that the authors designed and implemented for the open source framework Aerostack for aerial robotics. One of the main contributions of this work is the availability of a reliable solution to specify aerial mission plans, integrated in an active open-source project with periodic releases. To the best knowledge of the authors, there are not solutions similar to this in other active open-source projects. 

Q2. What have the authors stated for future works in "Tml: a language to specify aerial robotic missions for the framework aerostack" ?

In this paper, the authors have presented TML, a computer language that they designed to specify mission plans for aerial robots in the software framework Aerostack. The authors reviewed other proposals for mission plan specification in robotics. Since TML is part of the Aerostack, the authors plan to generate periodically new releases of this specification language with improvements and extensions. For example, the authors plan to extend TML with additional actions and skills for aerial robotics. 

Q3. What are the other methods that have been used in other robotic systems?

There are other methods with more flexible representations (e.g., task trees, finite state machines, rule bases, Petri nets, etc.) that have been used in other robotic systems, different from aerial systems. 

Q4. What is the purpose of the paper?

In this paper, the authors have presented TML, a computer language that the authors designed to specify mission plans for aerial robots in the software framework Aerostack. 

Q5. What are some other actions that can be performed by a robot?

Besides motion actions there are others such as: take a video, turn off the lights, memorize object image (to be tracked), memorize current point, say a sentence out loud, take a photo, send a message to other robots, etc. 

Q6. What are the constraints that can be used to activate skills?

The authors also consider that skills could be activated with certain constraints such as: (1) distance, i.e., the skill is only activated when the distance between the position of the robot and a certain point is less than certain value, (2) delay, i.e., the skill is activated after a number of seconds, (3) yaw, i.e., the skill is only activated for a particular yaw. 

Q7. What is the definition of a task-driven strategy?

The task-driven strategy is described as a loop (line 2) that covers all tasks according to a sequence established by line 12 (next task). 

Q8. What is the purpose of this paper?

As an answer to this need, this paper presents a mission specification language called TML for aerial robotics together with a reliable interpreter integrated in the Aerostack framework. 

Q9. Why do the authors think that this alternative is possible?

The authors believe that this simulation-based alternative is a possible solution to be used in the future, due to the availability of reusable specialized software components in robotics for simulation and the increasing computational power. 

Q10. What are some examples of skills that can be used to describe a robot?

The following list shows example skills: avoid obstacles, limit extreme movements, interpret ArUco visual markers, interpret voice sentences, and say out loud the current action.