The controlled element is the dynamic response of the cursor to control input, and it represents the real-world system under human control. A simple mechanical example is shown above. A rolling cart is attached to ground by a damper, and the control input pushes the cart with a force proportional to K. The equivalent controlled-element transfer function is shown in the right side of the figure. The cart exhibits a lagged velocity response with time constant M/b and steady-state velocity K/b. The units of these parameters depend on the units chosen for M, b, and K.

Simple models have been used to capture the primary behavior of certain degrees of freedom in aircraft, automobiles, and other complicated systems. Many experiments have used the simplest controlled elements with position, velocity, and acceleration responses.


All controlled elements included in the library are shown in the above table. There are the basic position, velocity, and acceleration responses. There are also versions of these basic responses with an added first-order lag, making them less responsive at first, but eventually reaching the same steady-state position/velocity/acceleration.

The unstable FirstOrderDivergent controlled element was used to investigate limitations of a human's effective time delay in Jex et al. (1966). The VelocityFlexibleMode includes a second order mode that can be oscillatory. This controlled element was studied with relatively high damping in Shirley and Young (1968), and with very low damping in Potter and Singhose (2013).


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