Hardware and so+ware architecture for Plexil-‐based, simula9on supported, robot automa9on Héctor Cadavid1; Javier Chaparro1 1Escuela Colombiana de Ingeniería
ABSTRACT
DEVELOPMENT METHODOLOGY
Some obsolete -‐but common-‐ pracCces in the applicaCon of ferClizers and pesCcides are causing serious environmental problems in Colombia; a situaCon that could be addressed by combining roboCcs and modern farming management principles, for example, the Precision Agriculture. This paper describes a novel applicaCon of Plexil -‐an experimental synchronous programming language developed by NASA-‐ for robot automaCon in agriculture, supported by a simulaCon plaeorm that allows quick prototyping of an automaCon plan, and a transparent integraCon of it on a physical robot. As a result, a methodology for evoluCve robot development, and a case study with a real six-‐wheeled mulCpurpose agricultural robot are presented. Further applicaCons of the simulaCon plaeorm as a mean to easily introduce roboCcs engineers to alternaCve -‐and less error prone-‐ programming models are also discussed.
An outcome of the retrospecCve of this first ajempt to integrate a real robot with an automaCon technology that has been evaluated mostly theoreCcally, is a m e t h o d o l o g y f o r t h e e v o l u C v e a n d incremental development of future Plexil-‐ b a s e d a u t o m a C o n s o l u C o n s . T h i s methodology, which is supported by the proposed soJware architecture and the simulaCon plaeorm considers two important constraints: • The need to avoid dependencies between hardware and soJware development teams to reduce scheduling risks and prevent idle resources. • The need to avoid unsafe/untested control code in the real robot that could lead to the damage of expensive devices.
PLEXIL & UE The Plan ExecuCon Interchange Language PLEXIL is a synchronous reacCve language developed by NASA to support autonomous spacecraJ operaCons. It has been used on applicaCons such as roboCc rovers, a prototype of a Mars drill, and to demonstrate automaCon capabiliCes for potenCal future use on the InternaConal Space StaCon. Programs in PLEXIL, called plans, specify acCons to be executed by an autonomous system as part of normal spacecraJ operaCons or as reacCons to changes in the environment. The computer system on board the spacecraJ that executes plans is called the Universal ExecuCve.
RESULTS
PRECISION AGRICULTURE Precision Agriculture is a farming management principle which aims at reducing the environmental load and the long-‐term sustainability of the agricultural producCon by applying ferClizers and pesCcides only where they are needed, when they are needed. This concept is very relevant for Colombian agriculture, especially considering the reported impacts of the tradiConal ferClizers and pesCcides applicaCon pracCces in this country.
RELATED WORKS Webot was one of the first commercial 2D/3D simulaCon environments for robots development. It was created by CyberboCcs and up to today new versions has been conCnuously released. Gazebo is another simulaCon package with a long trajectory in the field of roboCcs that aims to development of realisCc worlds for the robots by combining the Open Dynamics Engine (ODE) with the open source OGRE rendering engine. The simulaCon plaeorm described in this paper has a similar approach of the Gazebo/ROS plaeorm, given that (1) it uses a simulated environment as the source of events and as the receiver of the generated acCons, and (2) the acCons are generated by the same high-‐level soJware components (in this case, ROS drivers) that will be used by the real robot, but using a web based architecture. However, this is the first plaeorm that enables this kind of development with Plexil, an automaCon technology for mission criCcal systems.
CONCLUSIONS • At this stage, the project was focused mostly in the development of the proof-‐of-‐ concept of a hardware and soJware architecture supported by PLEXIL -‐a high-‐ level synchronous programming language-‐. It is expected to conCnue this work in cooperaCon with an agriculture research group for the development of real precision-‐agriculture soluCons, which will require the integraCon of specific soil-‐ sensors (e.g. pH and conducCvity), the development of more complex Plexil plans, and more staCc and dynamic -‐simulated and in-‐field-‐ tests. • This plaeorm could lead to a more friendly introducCon -‐for researchers in roboCcs-‐ to automaCon technologies like Plexil, and therefore, to the synchronous-‐reacCve programming paradigm as an alternaCve for a simpler and safer robots automaCon. This plaeorm could also be, in the future, a convergence point for all the theoreCcal work that has been done around Plexil and the current advances in applied roboCcs.
Contact
References
Nombre: Héctor Fabio Cadavid R. Universidad: Escuela Colombiana de Ingeniería E-‐mail:
[email protected] Website: www.escuelaing.edu.co
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