Department of Electrical and Computer Engineering Texas A&M University

1. Design and Implementation of Real-Time Discrete Controllers on NI cRIO/FPGA Adetutu Ajayi, Spencer Cureton, Undergraduate Students Dr. Karen Butler-Purry, Faculty Mentor Abstract Background Tools SOFTWARE HARDWARE The NI State Diagram Toolkit allows Finite State Models, which can represent a discrete controller, to be implemented on the cRIO/FPGA. The CompactRIO offers the ability to implement certain portions of the application in FPGA hardware while implementing other portions in its LabVIEW environment. An FPGA, with the ability to perform millions of operations in parallel, is the hardware used to efficiently implement complex FSMs. The goal of this project was to learn the process for designing and implementing complex finite state models on NI’s cRIO/FPGA using the State Diagram Toolkit within LabVIEW. An understanding of embedded discrete controllers, NI’s cRIO/FPGA, LabVIEW, and digital logic were necessary to achieve the desired objective. The implementation of certain examples in increasing complexity (vehicle tail-lights, a traffic light controller, and a four-level elevator controller) on the cRIO/FPGA using the state diagram toolkit, allowed achievement of the goal. LabVIEW 8.0: a development environment for a visual programming language from National Instruments. State Diagram Toolkit: provides a visualization of state machine programming architecture. Bridges diagram and LabVIEW code. Virtual Instrument: LabVIEW programs are called virtual instruments, or VIs, because their appearance and operation imitate physical instruments. Front Panel: User-interface that contains controls and displays to manipulate the LabVIEW code running in the Block Diagram. Block Diagram: Contains the block elements and wires representing code and data flow. • CompactRIO: The Compact Reconfigurable Input Output device includes • Embedded Processor: Pentium class processor that performs complex floating-point calculations • FPGA: Reconfigurable architecture built into the cRIO chassis for logic operations • Host Computer: Windows based PC with LabVIEW installed. Programs the cRIO device via a TCP/IP connection Embedded Controller: A device that monitors events or values within a system and creates outputs to change operational conditions of the system. FPGA (Field Programmable Logic Array); A programmable device containing millions of logic gates that allow multiple processes to execute at the same time. Finite State Model: A model of performance composed of a finite number of states, transitions between the states, and actions. Programming skills: Familiarity with programming techniques and sequences within LabVIEW environment; including an understanding of case selection, re-iterations, functions and variable manipulation. CompactRIO CPU FPGA EXAMPLE 1 EXAMPLE 3 EXAMPLE 2 Traffic Lights Vehicle Tail-Lights 4-Level Elevator Controller • Requirements: An intelligent discrete controller for a Four Level Elevator system with respective inputs and outputs. • Main Concepts: • Timing between states representing motor movement • Complex logic operations required to use/hold previous information. • Use of many variables (13 inputs and 19 outputs) and transition between states • Use of Truth tables and Karnaugh Maps to determine outcomes for all possible inputs • Modified code structure through SubVIs, Global Variables, and Sequence Structures IMPLEMENTATION DESIGN • Requirements: To produce a traffic light controller for a city intersection using sensors to detect turning cars while adhering to strict sequence patterns. • Main Concepts: • Introduction to digital controllers • Design/implementation on cRIO/FPGA. • Data communication between cRIO/FPGA • Sequencing and timing in design • Variable manipulation and clustering of variables • Requirements: A car’s light controller with sequential turning signals, emergency and brake lights, controlled by user-inputs on Front Panel. • Main Concepts: • Introduction to visual programming through State Diagram Toolkit. • Design front panel (user interface) Department of Electrical and Computer Engineering Texas A&M University College Station, TX 77843-3128 Lessons Learned Conclusions Future Work • Inclusion of NI hardware modules for use of external I/O • Power System Applications • System Reconfiguration: Fault analysis and rerouting to minimize outages. • Generator Monitoring & Control • cRIO vs. FPGA: The FPGA is more appropriate for data acquisition and highly critical control algorithms. All discrete operations should be implemented on the FPGA. The cRIO is suitable for precise floating-point operations, data logging and user control interface. • Design Process: Detailed design methods such as brainstorming, note taking, testing and debugging are needed to depict the design process before implementation • Real Time: Issues such as timing, sequencing and task priorities must be considered in design and implementation • A state diagram/table is advantageous in designing digital controllers because it considers all possible inputs at the different states • The state diagram toolkit provides a bridge between a visual state diagram and LabVIEW code. • The FPGA/cRIO serves as an ideal hardware target due to its ability to perform complex logic operations in Real-Time • Visual Programming is more appealing to a novice programmer. Electrical Engineering Research Applications to Homeland Security National Science Foundation: Research Experiences for Undergraduates Texas A&M Engineering: Undergraduate Summer Research Grant