So, what exactly is a HiTLCPS? Understanding the principles and theory behind these systems is the main objective of the current chapter. First, in Section 3.1, we will establish a taxonomy that will be used throughout the book. Then, in Sections 3.2 through 3.4, we will address the human role in the three basic processes of HiTLCPSs, namely data acquisition, state inference, and actuation, respectively.
As HiTLCPSs have a wide spectrum of applicability, it is difficult to cover all possible examples of HiTL solutions for a multitude of domains. Thus, we will begin by presenting the most basic, common processes in HiTL control, shown in Figure 3.1. The first phase is known as “data acquisition”. Data related to the human individual is gathered from the available sensors. This data is then processed in the “state inference” stage with the objective of inferring the human's physical and/or psychological state. Some approaches may also attempt to predict future states based on historical data and the current state. Finally, in the “actuation” stage, the system may or may not perform certain actions based on the observed state. Some “open-loop” systems do not affect the system per se, that is their results are merely informative, without direct actuation. However, “closed-loop” systems actuate directly on the environment or the human, in order to influence the loop and achieve a given target.