Stijn Quanten

Control of the 3-D spatio-temporal distribution of air temperature

An on-line mathematical approach was used to model the 3-D spatio-temporal temperature distribution in an imperfectly mixed forced ventilated room. A second-order model proved to be a sufficiently good description of the temperature dynamics (R 2 = 0.929) of the system for control purposes. Furthermore, it was possible to fully understand the physical meaning of the second order model structure. Using this model, a model-based predictive controller (MBPC) was developed for a single input single output (SISO) system. The controller was able to accurately control the mean temperature level of four spatial points in the room, and to robustly react to a random local disturbance signal. The results presented in this paper show that MBPC using data-based mechanistic modelling can be of significant importance in the development of a new generation of climate controllers.

Online detection of an emotional response of a horse during physical activity.

The objective of this research was to develop a non-invasive method to detect an emotional response of a horse to novelty during physical activity. Two horses performed 20 trials each, in which the horses heart rate (HR) and physical activity were continuously measured. The relationship between the horses physical activity and HR was described by a mathematical model allowing online decomposition of the horses HR into a physical component and a component containing information about its emotional state. Exposure to the novel object resulted in an increase in the emotional component of HR, which allowed automatic detection of an emotional response of the horse in 33/40 trials. In the remaining seven trials no stable model could be built or data were missing. The results show that model-based decomposition of HR can be a useful tool for quantification of certain aspects of temperament.

Model-based PIP control of the spatial temperature distribution in cars.

An on-line mathematical approach was used to model the spatio-temporal temperature distribution in the imperfectly mixed air inside a car. A second-order model proved to be a sufficiently good description of the temperature dynamics (R 2 = 0.985) of the system. Furthermore, it was possible to fully understand the physical meaning of the second-order model structure. Using this model, a proportional integral plus (PIP) climate controller was developed for a single input single output (SISO) system. The controller was able to follow a temperature level of 18–23–21°C at any desirable point, and to robustly react to a random local disturbance.

Sleepiness phenomics: modeling individual differences in subjective sleepiness profiles.

The present study investigates individual differences in subjective sleepiness profiles during 36 h of sustained wakefulness in a modified constant routine protocol. Twenty-three volunteers (11 females), aged between 18 and 47 yrs (M age = 30.41, SD = 10.26) enrolled in the study. Subjective sleepiness ratings were collected every 2 h by means of visual analogue scales. Circadian rhythmicity was assessed by means of salivary cortisol. Subjective sleepiness data were analyzed using functional principal component analysis (fPCA). Our results show that approximately 80% of the variance is accounted for by three functional components. The first component explains 50.28% of the variance and is characterized by a profile of exclusively positive loadings, representing vertical shifts from the mean sleepiness profile. Scores on this component are positively related to self-reported habitual sleep times and mean slow wave activity (SWA) during wake. Positive scores on the second component (18.40% of the variance) are characterized by a higher than average peak-to-trough amplitude in subjective sleepiness profiles. Participants with higher than average scores on this component show a significantly higher amplitude in salivary cortisol profiles as opposed to participants with lower than average scores. Participants with positive scores on the third component (10.09% of the variance) show higher than average levels of subjective sleepiness during morning hours, a buildup of wake effort occurring later and more afternoon sleepiness after sleep deprivation than negative scorers. Peak levels of salivary cortisol occur significantly later in these participants. Taken together, our results suggest that component 1 represents tonic differences in sleepiness profiles primarily related to mechanisms of sleep homeostasis, component 2 to circadian amplitude differences and component 3 to diurnal preference. However, since the components are additions to a mean profile, each of the three components is likely to correspond to a mixture of multiple physiological parameters, rather than to a single process. The approach shows interesting potential for (1) revealing unidentified physiological processes, (2) testing existing assumptions about regulatory mechanisms at the basis of interindividual variability in sleepiness profiles and (3) the specification of sleepiness phenotypes on a quantitative basis.

Day versus night driving in real traffic and on a driving simulator during an 800km all-highway drive

Driving performance was examined during daytime as opposed to night time during a prolonged drive in real traffic and on a simulator. Eight men and one woman, 25-65 years, participated. Subjects drove an 800 km all-highway drive twice - during daytime and night time - with a 24hr-interval. A driving simulator test was scheduled at the start, halfway, and upon arrival. During real driving, the standard deviation in the steering position was significantly higher from noon till 16:00, and from midnight till 3:00/4:00. Average driving speed was higher during the night, except from 1:00/2:00 till 3:00/4:00. Performance on the simulator did not correspond to this pattern. Concluding, circadian factors had a major impact on driving performance in real traffic. Furthermore, the relative validity of the simulator used, could not be established. This seemed to be related to poor motivation during the simulator tests.

Thermoregulatory changes at driver sleepiness

A functional link between thermoregulation and sleep onset has long been recognised and thoroughly reported. In this work, we present results of a study in which it is evaluated whether this typical functional link still holds in situations where sleepiness is present but subjects are struggling to stay awake (e.g. driver sleepiness) and hence sleep onset (Stage 1 NREM) is not reached. Eight men and six women aged between 20 and 35 years (M = 27, SD = 5.5) participated in the experimental phase which consisted of 42 driver simulator experiments. During simulator driving, Core Body Temperature, proximal and distal skin temperatures, environmental temperature, ECG and EEG are recorded. These experiments revealed that increasing peripheral heat loss is also present in situations of increasing sleepiness without eventually reaching NREM sleep. These results enhance the strong link between thermoregulatory changes and the onset of sleep.

Comparison of thermal comfort performance of two different types of road vehicle climate control systems

The performance of climate control systems in vehicles becomes more and more important, especially against the background of the important relationship between compartment climate and driver mental condition and, thus, traffic safety. The performance of two different types of climate control systems, an un-air-conditioned heating/cooling device (VW) and an air-conditioning climate control unit (BMW), is compared using modern and practical evaluation techniques quantifying both the dynamic 3-D temperature distribution and the local air refreshment rate. Both systems suffer from considerable temperature gradients: temperature gradients in the U-AC (VW) car up to 8–9°C are encountered, while the AC (BMW) delivers clear improvement resulting in temperature gradients of 5–6°C. The experiments clearly demonstrate the effect of the presence of even a single passenger on the thermal regime, increasing the existing thermal discrepancies in the compartment with 15% independent of ventilation rate. Furthermore, in terms of air refreshment rates in the vehicle compartment, an air-conditioning unit halves the air refreshment time at all positions in the vehicle cabin, delivering a significant improvement in terms of human comfort. Similarly, extra air inlets in the back compartment of a car deliver progress in terms of cabin refreshment rate (93 s down to 50 s).

Model-based temperature measurement technique to quantify the dynamic three-dimensional air freshness flow in the interior of a car

A data-based mechanistic (DBM) approach was used to model the spatio-temporal temperature distribution in the imperfectly mixed fluid in a car. The first phase of DBM involves the identification of a mathematical model from experimental data. A second order model proves to deliver a sufficiently good description of the temperature dynamics of the system (R² = 0.985). Furthermore, the physical interpretation of this second order model provides a useful variable. The physical meaning of one of the model parameters is what is called the local volumetric concentration of fresh air flow inside the car. It thus becomes possible to quantify the local air freshness in a complex geometric space as the interior of a car, only using simple temperature measurements. This technique could become a valuable tool in evaluating the performance of for instance climate controllers in interior spaces.