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Antonio Yordan-Nones Heterogeneous Modeling & Design of a Robot Arm Control System for Ptolemy II University of Puerto Rico, Mayagüez Mentors: Prof. Edward A. Lee Xiaojun liu http://chess.eecs.berkeley.edu Motivation Robots and embedded control systems are traditionally programmed to perform automated tasks, yet accomplishing dynamically changing tasks will typically require the use of specialized software systems. In order to design these sophisticated control systems the use of computational modeling and simulation techniques is necessary to ensure that final implementations of the system perform optimally. Since even the simplest robotic control systems are intrinsically a mixture of heterogeneous sub-systems, each focusing on a particular task, we need a means of modeling the different aspects of the system accurately and intuitively. Designing a Robot Arm Actor Input: •3D Cartesian Coordinates Output: •Incremental Servo Positions •Notify reaching outside of the robot’s workspace Design: •Calculate the inverse kinematics •Convert the degrees of rotation to absolute servo positions •Verify servo bounds to stay inside of the robot’s workspace •Step through the sequence of movements / positions of the servo motors •Output a stream of bytes to the external serial servo controller The focus of study in the Ptolemy project is on modeling, simulating, and designing embedded systems that require heterogeneous and hybrid modeling, component concurrency, and realtime responsiveness. Ptolemy extends component-based design principles by accurately managing the time continuum and maintaining concurrency among actors, features that are especially useful when designing control systems software. August 7, 2003 Modeling embedded control systems for robotics in Ptolemy is very flexible since there are a variety of models of computation to choose from. For example, an electro-mechanical system could be represented under continuous dynamics, and a digital communications system may be more appropriately modeled under the discrete-event domain. Systems that employ multiple modes of operation with overlapping computational domains are hybrid models. Lynx-5 Robot Arm CASE STUDY: Lynx-5 meets X-10 Remote Control PtolemyII: An Overview Modeling Control Systems in Ptolemy II Features: •A novel embedded system: •concurrent components •discrete-events (DE) •X-10 wireless remote control sends commands through the X-10 network •Specify the cardinal orientation to move the arm ( up - down - left - right ) •Implement communication between 2 different models & 2 different computers by sending datagrams To apply modeling techniques in Ptolemy and demonstrate embedded software control of a robotic manipulator we chose the Lynx-5 Robot Arm. The Lynx-5 is an articulated manipulator (RRR) with 2 planar links in an elbow-like configuration and 4 degrees-of-freedom - each of the 4 joints are controlled by dedicated servo motors.