The Instituto de Biomecánica de Valencia (Biomechanics Institute - IBV) and its consortium partners in the European project HARKEN have developed a non-intrusive system integrated into smart materials which is capable of monitoring cardiac and respiratory rhythms in order to prevent drivers from falling asleep. The two-year project had its final meeting in June.
The system is based on three main components: the seat sensor, the seat belt sensor and the signal-processing unit (SPU), which processes the sensor data in real time. All are invisible to the user.
The rhythm of heart beats, specially heart rate (HR) and heart rate variability (HRV), are good indicators of concentration and wakefulness (Lal and Craig, 2001), whereas the decrement of respiration rate has been also been proved to be correlated with increasing fatigue in monotonous driving (Milosevic, 2010), such that slow and deep breathing can indicate a relaxed resting state (Hadjileontiadis, 2006).
The HARKEN system will detect the mechanical effect such physiological activity, filter and cancel the noise and artefacts expected in a moving vehicle (vibration and body movements), and calculate parameters like the intervals between heart beats, or the amplitude and frequency of the respiration signal, which will be delivered in a readable format to integrate it in a fatigue detector.—Martínez et al.
|Scheme of the HARKEN concept. Source: Martínez et al. Click to enlarge.|
When people go into a state of fatigue or drowsiness, modifications appear in their breathing and heart rate; HARKEN can monitor those variables and therefore warn the driver before the symptoms appear.
The approach is similar in concept to technologies Ford described as part of its release of the S-MAX Concept (Earlier post.) Ford’s ECG Heart Rate Monitoring Seat would record the driver’s heart rate, delivering long-term heart activity data that would otherwise need to be recorded at medical centers, and could offer the potential to connect with Ford SYNC to alert remote medical experts to unusual activity or even trigger active safety systems to take over in a case of emergency. Glucose Level Monitoring connects with Ford SYNC could warn parents if a sleeping child in the rear seats suffers a diabetic episode.
The HARKEN system introduces some innovations addressing limitations of current systems.
It replaces the conventional electrodes to monitor physiological signals by smart textile materials, composed by a combination of fibres and yarns with electrical properties, supported by the standard textile of the seat and belt.
The placement of the safety belt strap on the chest and abdomen on the driver, and the pressure exerted on the body, are usually inadequate for physiological monitoring purposes via something similar to a plethysmography monitor. To address this, the HARKEN team studied driver anthropometry to determine the optimal location of the sensors, and designed a system of tensors to get a better control of the placement and pressure of the sensor.
The HARKEN system uses the pressure exerted by the driver’s body weight on the seat cushion and backrest to improve the sensitivity of the materials for certain types of signals. The HARKEN concept measures heart activity by ballistocardiography (BCG), a mechanical measurement of the blood flow driven by heart beats, which has successfully been measured in normal chairs. Although the BCG signal does not show the specific patterns of the ECG waves that are used in clinical assessments, the heart beats are clearly marked and are correlated in both signals, so salient features such as heart rate (HR) or heart rate variability (HRV) are equally measurable by this alternative.
The redundancy of physiological and dynamic measures of the driver’s body allows using data fusion strategies to improve the reliability of the outcome, along with the use of applying adaptive filters to cancel the effect of vibrations and artefacts in the processed signal. Due to those noise factors and filtering effects, the finer details of the physiological signals cannot be retrieved from such a system, but it still possible to look up the main features such as heart beats, and the intervals between successive breaths, that may be used to feed fatigue detection algorithms.
The outcome of this project is a fully functional prototype that allows anticipating the symptoms of fatigue associated with cardiac and respiratory rhythms, and monitors this physiological activity, with the aim of reducing the number of accidents.
The device has been tested by users in closed track tests, in order to prove its effectiveness under real-life conditions. With a short time-to-market scope, Project Harken will shortly have vehicles in the streets in order to run tests in real traffic scenarios.
Background. Road accidents and casualties caused by fatigue are an important societal and economical problem for the EU. In 2008 there were 1.2 million road accidents in the EU, which resulted in 1.5 million casualties and 38,000 fatalities. This kind of accident is projected to be the third most common cause of death and disability worldwide by 2020.
According to the figures of the eSafety Forum, the proportion of fatigue-related crashes is about 8.3% of all vehicle crashes. This implies nearly 100,000 crashes and about 125,000 injured people in the EU every year. That proportion rises when fatal accidents are considered: driver fatigue accounts for 20-35% of serious accidents. The projection of these figures means that there may be more than 7,000 annual fatalities due to fatigue-related accidents in the EU.
Fatigue in-vehicle detectors may reduce such a problem and may save thousands of lives per year, as well as many millions of Euros in health costs.
The HARKEN project received funding from the EU FP7 Capacities Work Programme: Research for the Benefit of SMEs and started in July 2012. The Instituto de Biomecánica de Valencia participates in this project together with the technological center Eesti Innovatsiooni Instituut (Estonia), and the University of Manchester.
Partners also include Fico Mirrors, S.A., which represents the components suppliers of the automobile industry, and SMEs that produce seat covers—Borgstena Group (Project Coordinator); safety belts—ALATEX; smart textiles—Sensing Tex, S.L.; and biosensors—PLUX.
≈ Helios De Rosario Martínez, José S. Solaz Sanahuja, Paulo Gameiro (2014) “Heart and respiration unobtrusive sensors integrated in the vehicle” (public report)