Heart rate variability (HRV) and muscular system activity (EMG) in cases of crash threat during simulated driving of a passenger car

Objectives: The aim of the study was to verify whether simultaneous responses from the muscular and circulatory system occur in the driver's body under simulated conditions of a crash threat. Materials and Methods: The study was carried out in a passenger car driving simulator. The crash was included in the driving test scenario developed in an urban setting. In the group of 22 young male subjects, two physiological signals - ECG and EMG were continuously recorded. The length of the RR interval in the ECG signal was assessed. A HRV analysis was performed in the time and frequency domains for 1-minute record segments at rest (seated position), during undisturbed driving as well as during and several minutes after the crash. For the left and right side muscles: m. trapezius (TR) and m. flexor digitorum superficialis (FDS), the EMG signal amplitude was determined. The percentage of maximal voluntary contraction (MVC) was compared during driving and during the crash. Results: As for the ECG signal, it was found that in most of the drivers changes occurred in the parameter values reflecting HRV in the time domain. Significant changes were noted in the mean length of RR intervals (mRR). As for the EMG signal, the changes in the amplitude concerned the signal recorded from the FDS muscle. The changes in ECG and EMG were simultaneous in half of the cases. Conclusion: Such parameters as mRR (ECG signal) and FDS-L amplitude (EMG signal) were the responses to accident risk. Under simulated conditions, responses from the circulatory and musculoskeletal systems are not always simultaneous. The results indicate that a more complete driver's response to a crash in road traffic is obtained based on parallel recording of two physiological signals (ECG and EMG)

Application of modelling and simulation to evaluate the theta method used in diagnostics of automotive shock absorbers

The dynamic properties of the car's suspension largely depend on the damping that results from the state of the shock absorbers. Their technical condition is essential for vehicle occupants’ comfort and traffic safety. It changes with the time and intensity of use of the vehicle. Therefore, adequate methods of non-destructive (diagnostic) testing of suspension damping have been sought for many years. The on-vehicle tests are particularly useful thanks to their low cost and short test duration time. The newest method is the ‘theta’ method which is the subject of the presented article. Notation ‘theta’ usually means relative damping (damping ratio) in the vibrating system. The paper asses four variants of the method. Two versions come from modal analysis and are also known as the ‘peak-picking method’ or ‘half-power method’. Two other versions are described in cited patent documentations. Three linear ‘quarter car' models with their description in the frequency domain were used to assess mentioned variants of the ‘theta’ method. Calculations were made for two typical datasets corresponding to the front and rear suspension system of a medium-class motor car. This provided grounds for general qualitative and (within a limited scope) quantitative assessment of the usefulness of individual variants of the method under analysis and for comparisons between them. The paper is to help in choosing the variant of the ‘theta’ method that would most likely find the application and that might be recommended to manufacturers and would-be purchasers of diagnostic suspension testers. The author has also highlighted the importance of possible further research

Application of Modelling and Simulation in Durability Tests of Vehicles and Their Components

The use of simulation and modelling has been proposed for determining the excitations to be applied in the procedures of laboratory testing of a car’s structural components, without the need to test the complete vehicle. The paper presents the general concept as well as an example of the procedure. It covers determining the spectrum and time-domain realization of a load on a selected node of the vehicle structure under durability tests. The author used both the mathematical and physical model of the tractor-semitrailer unit, where the input was considered as a random process resulting from the road profile. He calculated the transmittance modules and the power spectral densities of the vertical force on the joint between the tractor’s fifth wheel and the kingpin of the semitrailer and the extreme values of the dynamic components of this force. The inverse discrete Fourier transform makes it possible to generate the realization of the said force. It can be used in durability studies. The limitation of the work to the testing of a specific structural node reduces the scope and, in consequence, the cost of the process. The method presented may also be used for various types of vehicle models, including hybrid and electric vehicles

The influence of an unbraked single-axle trailer on the stopping distance of a two-axle car

Artykuł przedstawia wyniki obliczeń symulacyjnych procesu hamowania w ruchu prostoliniowym zespołu pojazd dwuosiowy - jednoosiowa niehamowana przyczepa oraz samego pojazdu dwuosiowego. Oceniano długość drogi zatrzymania zespołu pojazdów na poziomej i pochylonej wzdłużnie drodze, zarówno dla jezdni suchej jak i mokrej. Zmieniano pochylenie wzdłużne drogi, a także masę przyczepy oraz położenie wzdłużne i pionowe jej środka masy. Efektem pracy jest jakościowa i ilościowa ocena wpływu na skuteczność hamowania samochodu dwuosiowego z dołączoną do niego niehamowaną przyczepą jednoosiową. Otrzymane wyniki wykazały, że dodatkowe obciążenie pojazdu bez przyczepy nie ma wpływu na długość drogi zatrzymania ani na wartość maksymalnego opóźnienia hamowania, gdy kierowca może w pełni wykorzystać przyczepność kół jezdnych do nawierzchni. Dołączenie niehamowanej przyczepy ma największy wpływ na drogę zatrzymania dla pojazdu o najmniejszej masie. Jak można było oczekiwać, wzniesienie skraca drogę zatrzymania, natomiast spadek drogi wydłuża ją. Długość drogi zatrzymania znacznie wydłuża się na mokrej nawierzchni, co uwidacznia się szczególnie na spadku drogi.The article presents the results of simulation calculations of the braking process in a straight-line motion of a set of a two-axle vehicle and a single-axle unbraked trailer. The stopping distance of the set on a horizontal and sloping road surface, dry and wet, was assessed. The longitudinal inclination of the road was changed, as well as the weight of the trailer and the longitudinal and vertical position of its centre of mass. The result of the work is a qualitative and quantitative assessment of the impact (on braking efficiency) of attaching an unbraked single-axle trailer to a two-axle car when going up and down a hill and on a level road surface. The obtained results showed that the additional load of the vehicle itself (without the trailer) had no effect on the length of the stopping distance or on the value of the maximum braking deceleration when the driver could fully use the traction of the road wheels to the road surface. Attaching an unbraked trailer has the greatest effect on the lightest vehicle. As expected, positive elevation shortens the stopping distance, while negative elevation lengthens it. The length of the stopping distance increases significantly on a wet surface, which is particularly noticeable for negative elevation

Assessment of Drivers’ Reaction Times. Tests on the Track and in the Driving Simulator

This paper describes research studies analyzing the behaviour of drivers in the simulated accident risk situation. The study was conducted in two environments: on the Kielce Car Test Track and in the driving simulator autoPW of Warsaw University of Technology. The same 3 (different) situational scenarios of accidents were performed in both environments and the same group of 100 drivers was examined. Each of the examined persons performed the same set of tests, randomly ordered, carried out for various values of the time TTC (time to collision), received as combinations of the tested vehicle velocity and its distance from the roadblock. The vehicle speed was changed within the range from 36 up to 60 km/h, and the distance of the vehicle from the first roadblock from 5 up to 50 m. The paper presents exemplary results of the research studies

Heart rate variability (HRV) and muscular system activity (EMG) in cases of crash threat during simulated driving of a passenger car

Objectives: The aim of the study was to verify whether simultaneous responses from the muscular and circulatory system occur in the driver's body under simulated conditions of a crash threat. Materials and Methods: The study was carried out in a passenger car driving simulator. The crash was included in the driving test scenario developed in an urban setting. In the group of 22 young male subjects, two physiological signals - ECG and EMG were continuously recorded. The length of the RR interval in the ECG signal was assessed. A HRV analysis was performed in the time and frequency domains for 1-minute record segments at rest (seated position), during undisturbed driving as well as during and several minutes after the crash. For the left and right side muscles: m. trapezius (TR) and m. flexor digitorum superficialis (FDS), the EMG signal amplitude was determined. The percentage of maximal voluntary contraction (MVC) was compared during driving and during the crash. Results: As for the ECG signal, it was found that in most of the drivers changes occurred in the parameter values reflecting HRV in the time domain. Significant changes were noted in the mean length of RR intervals (mRR). As for the EMG signal, the changes in the amplitude concerned the signal recorded from the FDS muscle. The changes in ECG and EMG were simultaneous in half of the cases. Conclusion: Such parameters as mRR (ECG signal) and FDS-L amplitude (EMG signal) were the responses to accident risk. Under simulated conditions, responses from the circulatory and musculoskeletal systems are not always simultaneous. The results indicate that a more complete driver's response to a crash in road traffic is obtained based on parallel recording of two physiological signals (ECG and EMG)