A Novel Approach To Simulating Factory Control System Problems Through A Pc And Four Microcontrollers

Real-World Factory equipment often incorporates various types of communication, interface and control features to provide reliable equipment performance and meet demanding production requirements. This paper discusses a novel simulation project developed to address such common problems as they may be encountered by factory equipment control systems. The reader will gain insight about typical problems and solutions. The module was written in Visual Basic (VB); provides a PC-Based, control and monitoring, Graphical User Interface (GUI); and interfaces to four industrial microcontrollers. Each of these controllers is from a separate manufacturer and programmed with a different software language, including BASIC-52, assembly, ladder and C. RS-232 protocol serially communicates with the VB program through four serial ports that are provided by a PC-Based RocketPort system. Bidirectional serial communication with both binary and ASCII data was developed to study, document and compare methodologies. The GUI was designed to monitor and control factory simulation activities, inputs and outputs (I/O) and alarm functions via microcontroller serial communications. The factory simulation layout is comprised of a variety of components to focus on diverse design and assembly challenges. These include a controllable motor driven propeller with rotation tracking capability, a closed-loop self-balancing pendulum, a hand-held pendant, temperature and light sensors with controllable sources, a light tree, motorized cam-controlled switches and a mechanical counter. The GUI enabled excellent serial communication with the four microcontrollers to provide factory simulation control and monitoring. The Microsoft VB MSComm drivers and the RocketPort system provided simultaneous and robust bi-directional serial communications. Both binary and ASCII data communications proved to be effective methods by providing fast and accurate control, alarming and monitoring. Introduction Production factories are continuously challenged with providing a large variety of cost competitive products with short manufacturing durations. Fast, flexible and reliable electrical and electronic communication, interface and control systems are crucial for factory processes to run efficiently, provide manufacturing flexibility and deliver a wide range of products. Generally a manufacturing process is an equipment collection developed by various manufacturers and operated with various controller types. A modern flexible manufacturing area requires equipment integration into one seamless system. This is challenging due to combinations of computers, microcontrollers, Programmable Logic Controllers (PLC’s) or other controller types. The controllers are programmed and wired to control or monitor sensors, actuators, switches, indicators, alarms and similar devices to provide required system functionality 2 . P ge 1.89.2 This paper examines a project devoted to electrical communication, interface and control concepts and issues. It was specifically developed to provide a real-world factory simulation model utilizing four industrial microcontrollers and five software languages. Each represents a factory control system interconnected via the RS-232 serial protocol. The model leveraged simultaneous bi-directional serial communication with a PC-based Graphical User Interface (GUI). The GUI was programmed with Visual Basic (VB) and provided the factory simulation control, alarming and monitoring focal point. Several factory equipment control system problems were encountered and solutions were developed. For in-depth learning, it was decided to use microcontrollers from separate manufacturers and programmed with a different software languages, including BASIC-52, assembly, ladder and C 2 . The system interface and control elements were developed and demonstrated by controlling devices based on GUI selection, sensor levels and switch states. These included a controllable motor driven propeller with rotation tracking capability, a hand-held pendant, temperature and light sensors with controllable sources, a light tree, motorized cam-controlled switches and a mechanical counter. It also included a self-balancing pendulum with closed-loop manual and GUI position control and monitoring capabilities. This proved to be the most difficult simulation subassembly to control, so additional details will be provided later. Two printed circuit boards (PCB’s) manually control microcontroller inputs with switches and display output status with LEDs. Two breadboards were incorporated to provide development project support and one contained analog signal conditioning circuits. The reader will gain insight from the comprehensive factory simulation model since it uncovered many real-world problems. Key factory RS-232 communication scenarios combined with interface and control simulation solutions provide good reference material . The central VB GUI control and monitoring example can be implemented into various controls projects in a reasonable timeframe. The challenge was expanded when it was decided to develop simultaneous serial communications without the use of any off-the-shelf communication package. Also, the serial communications development was expanded to include binary and ASCII character bi-directional communication. A variety of software solutions and data decoding methods were incorporated to handle these options. Project Scope The project started by determining how real-world controller communication problems could be understood and applied to microcontrollers 2 . First, the RS-232 serial communications protocol was selected due to its popularity. One main objective was to create a factory simulation with multiple microcontroller types and software languages. The first microcontroller was the Motorola 68HC11 (MC02) programmed in assembly language. Next, the Z-World microcontroller (MC04) based, on the Zilog Z-180 processor was purchased due to the fact that it is programmed with the C language. It was decided that the final two microcontrollers would be the EMAC (MC01) and GE Fanuc Micro-PLC (MC03) microcontrollers. MC01 was programmed with BASIC-52. The MC03 microcontroller is was an appropriate controller since it was programmed in the ladder language. Finally, the fifth software language chosen was Microsoft’s Visual Basic (VB), because it is a popular and widely used language that can provide P ge 1.89.3 powerful GUI features. The communication between the microcontrollers and PC was handled with the Comtrol RocketPort system. This provided up to thirty-two PC COM ports, which allowed each microcontroller to be connected to a separate COM port. Figure 1 outlines the project signal flow concept, which became the basic system design principle. Factory Control Screens COMP01 Computer w/ Graphical User Interface (GUI) Software Language: BASIC-52 Software Lanugage: Assembly Software Language: Ladder Software Language: C Software Lanugage: Visual BASIC RP01 RocketPort 16 Channel Breakout Module MC02 Motorola 68HC11 Microcontroller MC01 EMAC Microcontroller MC03 GE Fanuc Micro-PLC MC04 Z-World Microcontroller RP01-HOST To RocketPort ISA PCB