Page 129 - Welding Robots Technology, System Issues, and Applications

116 Welding Robots
4.4 Programmable and Flexible Control Facility
To be able to use a robot manipulator, the required sensors and the necessary
welding equipment, on a robotic welding application, it’s necessary to outline the
software architecture that could be used as the developing platform. The challenges
posed by a robotic welding system are not different from the ones posed by a
typical flexible manufacturing system based on robots. Consequently, the software
architecture presented here was designed to be used with general robotic
manufacturing cells that may include several types of equipment like robot
manipulators, mobile robots, PLCs, CNC machines, vision systems and several
types of sensors, etc. Usually these systems use different programming languages,
even when the manufacturer is the same. It is then very difficult to make
adjustments to the cell functionality, or adapt it to new requirements posed by the
introduction of a new product or by changes introduced in existing products.
Several research and technical efforts have been made to overcome these problems.
Many of those efforts point to solutions that consider the development of general
programming languages that could be used with any equipment, relying on
individual interpreters to generate the specific code for any equipment.
Nevertheless, recent research works show that it is desirable to have a flexible
environment and still program each machine using its own language [24],[25]. The
reason is simple: a general syntax means introducing generalizations and
simplifications that tend to limit the potentiality of the equipment. Consequently,
some parameterization is not used, special non-grouped functions are not used and
the generated code takes always a uniform structure which may not be the best for
all machines.

The idea presented here is significantly different, being an alternative for the
solutions presented in the literature [27], and also for the software products truly
distributed available on the market [28]-[30]. The basic idea is to define for each
individual machine a collection of software functions that expose all its basic
operational features. That objective requires local processing capabilities,
availability of communication channels and support for the standard technologies
used when implementing the services, installed on the individual machines. Since
the vast majority of the current robotics and automation (R&A) equipment meets
these requirements fully, this is not a serious limitation. It should also be stressed
that the above-mentioned services are to be offered through a local network, on a
distributed software framework based on the client-server model. Furthermore,
using those services from the remote client computer to build controlling and
inspection applications can be performed from any platform (UNIX, Linux,
Win32-DCOM, etc.), using standard programming languages (C, C++, C#, Visual
Basic, etc.).

Several approaches can be used and are currently available from various robot
manufacturers, with specific details and implementations. Nevertheless, the
following objectives are pursued by any of the above-mentioned software
architectures: