Types of remote control systems

Hot cells for the nuclear energy development have been one of the primary applications areas for teleoperation systems, because of the hazardous radioactive environment involved. A classical example of tele-manipulator as was publicized in the press during the peak era of nuclear technology development can be glimpsed by the cover page picture of the German magazine Der Spiegel [49].

FIG. 8. Photograph of tele-manipulator on the cover page of Der Spiegel.

Apart from the teleoperators, a number of other tools and devices have been applied to nuclear facilities and with the development of industrial robotics the non-nuclear applications have been merged with teleoperation technology of nuclear origin.

Hot cells for the nuclear energy development have been one of the primary applications areas for teleoperation systems, because of the hazardous radioactive environment involved. Apart from the teleoperators, a number of other tools and devices have been applied to nuclear facilities and with the development of industrial robotics the non-nuclear applications have been merged with teleoperation technology of nuclear origin.

• Hard automation includes all automatic machinery that is built for specific purpose. Optimized for a specific task prior to installation, hard automation usually performs its task reliably. Such machines are not programmable and can only be reconfigured by physical re-arrangement and manual settings. Examples discussed include automatic fuel handling and loading machines in the Russian Federation and the USA, and cutting and grinding machines in India.

• Telemanipulators are mechanical or electromechanical machines (e.g. master-slave manipulators) directly controlled by human operators to perform a task at a distance. A telemanipulator is often composed of a master arm and located in the operator side and the other side of the manipulator (‘slave’ arm) located in the working enclosure, from where information (visual, sound, force, etc.) is fed back to the human operator who controls the master arm linked to the slave manipulator. At hot-cell facilities, a pair of master manipulator arms are usually installed to match with human arms (both right and left) of the workers.

• Telemanipulators are generally more complex and expensive than manual tooling, require periodic maintenance, and are potentially less reliable than manual tools. However, over 50 years of continuous use and improvement has proven telemanipulators generally reliable. A large number of telemanipulators are in use at a variety of nuclear facilities around the world.

• A telerobotic system is capable of performing either a bi-lateral mode (between the master side and slave side, like the telemanipulator) or in a unilateral mode from the master side to the slave side (like the electro-mechanical or ‘power’ manipulator). In the latter case, the end-effector trajectory and force/impedance of slave arm are determined by computer command rather than master arm inputs. The advantage of this unilateral mode is to perform repetitive tasks by automated program thus to avoid the operator intervention in the loop.

• Robotic machinery has been used primarily in production modes and structured environments, usually for material movement between processes. Examples presented include fuel production and dismantlement in India and the USA, and automated inspections and fuel reconstitution in Germany. Robotic machinery has also been installed at reprocessing facilities in France and the UK.

Force reflection refers to the capability of reflecting the external force experienced by the slave side to the master side and is typically described as bilateral control. Applications of force reflection systems are often hindered by radiation effects on electronics or control medium like hydraulics which suffer sometimes with seal degradation. More recently, advances in equipment and control capabilities have enabled design of flexible robotic systems for unstructured environments and off-normal event recovery. Specifically, the convergence upon telerobotics has put the human into the robotic control loop. Telerobotics refers to computer-assisted manual operations, or conversely, manually-assisted computer operations. This combination allows a human operator to concentrate on the task without concern for the operating details, resulting in potentially faster and safer execution of operations in difficult environments.

Robotic systems can be significantly more complex than telemanipulators, raising reliability issues and questions of radiation tolerance. In the past, robotic systems were primarily programmed by laborious teach-and-repeat methods, operating thereafter in autonomous mode. This has not been conducive to application beyond the production facility. Further, capital expense of robotic systems can be significantly higher than manual and teleoperated tools. However, operational experience in France and systems analysis of future US facilities have shown that robotic systems can have substantially lower operating costs than manual

operation or telemanipulation, while increasing speed and safety. This operational cost reduction can offset capital costs, in some cases quickly.

More recently, advances in equipment and control capabilities have enabled design of flexible robotic systems for unstructured environments and off-normal event recovery. Specifically, the convergence upon telerobotics has put the human into the robotic control loop. Telerobotics refers to computer-assisted manual operations, or conversely, manually-assisted computer operations. This combination allows a human operator to concentrate on the task without concern for the operating details, resulting in potentially faster and safer execution of operations in difficult environments.