Mechatronic objects for real-time control software development

Abstract

The design of real-time control software for a mechatronic system must be effectively integrated with the system hardware in order to achieve useful qualitative benefits beyond basic functionality. The sought-after benefits include: rapid development, flexibility, maintainability, extensively, and reusability. In this work we focus upon the interface between the device drivers and the control software with the aim to properly design this interface to best realize the aforementioned benefits. The results of this fundamental research include the development of an easily manageable set of four C++ object classes following an object-oriented approach to software design. These Universal Mechatronic Objects (UMOs) are applicable to a wide spectrum of actuators including dc motors, stepper motors, and solenoids; and sensors including pressure sensors, microswitches, and encoders. UMOs encapsulate the interface between the electrical subsystem and the control subsystem, providing the control software developer with a powerful abstraction that facilitates the development of hardware-independent control code and providing the electrical subsystem developer with an effective abstraction that facilitates the development of application-independent device drivers. Objects which are intuitively related to hardware components of the mechatronic system can be declared using the UMOs early in the system development process to facilitate the rapid concurrent development of both the electrical and the control subsystems. Our UMOs were developed as part of a project to implement a real-time control system for a z-theta robotic manipulator. The z-theta manipulator is one component of the Minifactory project in the Microdynamic Systems Laboratory at Carnegie Mellon University. The goals of this agile assembly project include the reduction of factory setup and changeover times, plug-and-play type modularity, and the reuse of its components. The application of UMOs to the manipulator software development is shown to be consistent with these goals.