Advanced Welding Processes: Technologies and Process Control

Welding automation and robotics 237
The positional control system controls the position and velocity of a number
of axes, either rotational or linear, to enable three-dimensional trajectories to
be followed. Both the welding head and component position may be controlled.
The weld process control system may control the welding parameters directly
or more commonly via an interface with an intelligent welding power source
(see Chapter 3). Cell management activities concern the communications
between the welding system and the external production environment. The
control should be able to actuate component delivery and discharge systems,
provide job status and quality information. The combination of computer
control and modular mechanical design offers an alternative to the normal
robotic approach.
11.8 Remote-control slave and automated systems
Remote-control welding devices are used in particularly hazardous
environments. They may take the form of a master-slave manipulator or a
fully automated system with remote monitoring.
11.8.1 Master-slave manipulators (MSM)
Master-slave manipulators involve the use of a multi-axis positioner, which
is positioned and controlled by a remote manual operator. These devices
have been used in the nuclear industry for the manipulation of radioactive
components and in hyperbaric applications for positioning components or
welding inside a high pressure chamber.
These systems are usually specially built to meet the specific application
requirements; although some general-purpose arms are available, 5 these are
not normally designed for welding applications, and the repeatability, positional
accuracy and load-carrying performance must be evaluated carefully. Welding
systems of this type have been specially developed for nuclear applications.
11.8.2 Fully automated remote welding systems
The use of fully automated systems for remote welding applications reduces
the possibility of manual error and should improve repeatability. Systems
have been developed for deep-water hyperbaric applications, [280, 281] in
which welding is carried out at depths of up to 360 m in a dry hyperbaric
chamber filled with helium-rich gas. The welding head is an orbital GTAW
system and an inverter-based electronic power source under computer control
is situated within a service container adjacent to the welding enclosure (i.e.
5Special-purpose remotely controlled arms are normally designed for underwater applications
or bomb detection and disposal.