Introduction to the special issue on shared control

Shared control is an exciting up-and-coming engineering field that is blending the boundaries of control, where humans interact with robots or vehicles that are partly automated. The main challenges for robotics and automation today are posed by the less structured, unpredictable environments, in which humans operate naturally, especially when they need to interact with other humans. As a result, many semi-automated systems today need to be supervised by human operators, but as fast as the levels of automation of many systems are increasing, we also need to speed up how we think about what this implies for human-machine interaction. The widely applied paradigm of human-centered automation has been popular and useful for the past two decades, but it requires an update with the current trend in automation becoming more ubiquitous in human environments and less dependent on explicit input from the human operator. In contrast to the supervisory control paradigm---where control is traded between human and machine---the shared control paradigm implicitly assumes the interaction between two or more independent agents that together perform a task to achieve a common goal. This implies that the design of the shared control system is not necessarily only human centered. In shared control systems, all the acting agents need to be aware of the others' capabilities, weaknesses, and authority. Hence, reciprocal communication of each agent's operational boundaries, whether human or machine, is essential.