The Human Transfer Function

August 15, 2024 - Have you ever wondered how we can predict a system's reaction to different inputs? That’s where something called a transfer function comes into play. A transfer function is a mathematical model that helps us understand a system’s output based on its inputs, making it more predictable and useful. But what's often overlooked is the crucial role of the human controller, one of the most versatile and reliable components in these systems.

Think about a pilot in an aircraft. They are not just operators; they are adaptive learners who can exhibit a wide variety of behaviors. Because of this, researchers realized that it was essential to develop mathematical models that capture how pilots respond to different situations. While we already had equations to describe how aircraft behave, understanding how pilots react was equally important for predicting the system's overall performance.

To dive deeper into this, researchers conducted numerous experiments that involved human pilots interacting with unpredictable scenarios. These simulations showed that pilots can adjust their actions to meet the demands of various tasks, optimizing their performance. Pilots' responses tend to be consistent and reliable thanks to training and careful selection, and the researchers generalized this work with a precedent-breaking idea. The human adjusts their own transfer function (within a reasonable range and within the typical reaction time inherent in the human neuromuscular system) to close the loop and stabilize the system.

It’s quite a feat when we can create a mathematical equation that predicts how humans will behave based on sensory input. This achievement has led to the development of a theory that explains how people manually control vehicles. This theory is not just an academic exercise; it’s a practical engineering tool that helps us understand past results and anticipate new challenges. By applying these insights, we can design more robust and effective systems. In summary, the human transfer function highlights the important role that human controllers play in system performance. By understanding and modeling their behavior, we can create better, more reliable systems that work in harmony with human operators.

References:

Salas, E., & Maurino, D. (Eds.). (2010). Human Factors in Aviation. Academic Press.

McRuer, D. T., & Jex, H. R. (1967). A review of quasi-linear pilot models. IEEE transactions on human factors in electronics, (3), 231-249.

McRuer, D.T., & Krendel, E.S. (1959). The human operator as a servo system element. Journal of the Franklin Institute, Volume 267, Issue 5, 381-403.

van Passen, M.M., & Mulder, M. (1998). Identification of Human Operator Control Behavior in Multiple-Loop Tracking Tasks. Delft University of Technology, Faculty of Aerospace Engineering.