Intermittent control: a computational theory of human control

Abstract

The paradigm of continuous control using internal models has advanced understanding of human motor control. However, this paradigm ignores some aspects of human control, including intermittent feedback, serial ballistic control, triggered responses and refractory periods. It is shown that event-driven intermittent control provides a framework to explain the behaviour of the human operator under a wider range of conditions than continuous control. Continuous control is included as a special case, but sampling, system matched hold, an intermittent predictor and an event trigger allow serial open-loop trajectories using intermittent feedback. The implementation here may be described as "continuous observation, intermittent action". Beyond explaining unimodal regulation distributions in common with continuous control, these features naturally explain refractoriness and bimodal stabilisation distributions observed in double stimulus tracking experiments and quiet standing, respectively. Moreover, given that human control systems contain significant time delays, a biological-cybernetic rationale favours intermittent over continuous control: intermittent predictive control is computationally less demanding than continuous predictive control. A standard continuous-time predictive control model of the human operator is used as the underlying design method for an event-driven intermittent controller. It is shown that when event thresholds are small and sampling is regular, the intermittent controller can masquerade as the underlying continuous-time controller and thus, under these conditions, the continuous-time and intermittent controller cannot be distinguished. This explains why the intermittent control hypothesis is consistent with the continuous control hypothesis for certain experimental conditions.

Ageing of internal models: from a continuous to an intermittent proprioceptive control of movement

“…Kleinman 1969) or an intermittent (e.g. Gawthrop et al 2011) model of control is more appropriate to explain the motor behaviour has been widely discussed in the literature. Results of the present study suggested that the control of movement was mainly continuous in young adults and mainly intermittent in older adults.…”

Cloud Type Interpretation of Statistical Properties of Human Response Delay in Pendulum Balancing

“…During the last decades there have been found much evidence for a novel paradigm of human actions in balancing various systems-human intermittent control (for a review see, e.g., [1,2,3,4,5]). This paradigm implies that human control is discontinuous, repeatedly switching on and off instead of being always active throughout the process.…”

“…Recently the event-driven models have become widely employed [10,1,11,4]. They are built up on the fact that humans cannot detect small deviations of the controlled system from a desired state and for this reason are not able to control the system dynamics in its close proximity.…”

“…An approach based on governing equations similar to (1) has been developed for describing human reaction in balancing unstable objects with the prediction of their motion, e.g., [1,14]. The models with prediction assume the information about the system state at time moments t < t − τ to be known and uses the internal models to "calculate" system states in the time interval (t − τ, t).…”

“…In particular, we have observed that the response delay time characterizing the control activation is a random variable changing in a wide interval about 100-600 ms [16]. It has enabled us to pose a question about, at least, the universality of approaches employing models similar to (1).…”