Seat Sensor Research Articles

A technological solution to child safety seat errors: Efficacy of the cellular car seat

Objective Although child safety seats are highly effective in preventing injuries, they are frequently misused. Experts have identified two leading “critical misuses”: (1) loose harness straps and (2) loose vehicle attachment at the base. We designed an innovative child safety seat system that educates, instructs, and alarms participants of safety seat errors. The system includes both the Cellular Car Seat (CCS) smartphone app and a network of car seat sensors. Our objective was to determine if CCS system users had fewer child safety seat misuses than users with a child safety seat manual alone. Methods During the study visit, 92 participants completed three safety seat scenarios using a mock vehicle setup, test doll, and a convertible child safety seat: A) fully install a convertible safety seat, B) recognizing/correcting loose harness straps in a seat with intentionally loose straps, and C) recognizing/correcting loose attachment to the vehicle seat at the base in a seat with intentionally loose attachment. Intervention participants (n = 46) were asked to use the CCS app during each scenario and control participants (n = 46) were given only the paper child safety seat manual. For each scenario, researchers determined errors/misuses present at the end of the scenario, time to complete scenario, and tension achieved on the harness straps (collected via load cell). Results Compared with controls, intervention participants had significantly fewer errors and higher average harness tensions for all three scenarios; furthermore, a greater portion achieved a harness tension of 4 newtons. During Scenario A, the rate of loose harness strap errors was more than three times higher for controls and loose base attachment errors almost six times higher. We observed similar trends in Scenario B, with harness strap errors more than double for controls. In Scenario C, the rates of both critical misuse errors were four times higher for controls compared to the intervention group. Conclusions The innovative CCS system was highly effective at reducing child safety seat use errors, especially critical misuses. Reducing critical misuses will decrease injuries and fatalities among crash-involved children. The CCS system can alert families to everyday harnessing and installation errors and provide families and caregivers with ongoing, accessible support.

Industrially Scalable Piezoresistive Smart-Textile Sensor for Flexible Electronics Application.

Industrially scalable pressure-sensitive smart textile sensors have been developed using graphite-polyurethane (G-PU) composite materials by the plasma-assisted dip-pad-dry-cure method. The advantage of this technique is that it is easy, simple, and suitable for high-volume production with industrially available machinery. The sandwich structure sensor has been constructed with the pressure-sensitive textile semiconductor and embroidery electrodes for manufacturing a single sensor and sensor matrix, which can detect touch, pressure, movement, etc., and send information wirelessly (via smartphone) to the user in real-time. The sensibility, hysteresis behavior, repeatability, and stability against washing, martindale abrasion, etc. of the piezoresistive polyester (PES) textile sensor have been optimized by the plasma-assisted semiconductive coating. The smart textile sensor built into this work provides flexibility, breathability, and wearability and can be easily integrated into wearable items allowing for object detection by scanning their weight, movement, interactive floor mate, and seat sensor mate for dynamic posture detection and sensor hand glove to translate finger movement into sign language (e.g., text or audio able). All necessary electronics and software associated with the relevant application have been developed to demonstrate the effectiveness of the products in a real-world demonstration, which encourages the widespread use of smart textile piezoresistive sensors for a variety of applications in flexible electronics sectors.

Hybrid RFID Based Batteryless Seat Sensor With Discontinuous RF Transmission

In this paper, a hybrid RFID tag and reader system is proposed for wireless and batteryless automotive sensors. The hybrid RFID tag operates in dual mode, which includes conventional RFID operation, and tag active transmission. The reader provides the carrier in conventional RFID communication, using which the tag performs backscatter modulation. In tag active transmit mode, the reader does not provide any carrier, and the tag synthesizes its own carrier for communication. The hybrid tag can communicate with the reader for a range of 21 in. A commercial seat belt sensor was integrated with the tag and a working prototype of the complete system was demonstrated. Time response is a critical parameter for the whole system to work coherently and hence the operational states were modeled for time estimation and address the key parameters. Individual subsystems within the tag and reader circuits are presented in detail to capture the complete system. The proposed system can reduce the effective on-time of the reader significantly and the analysis shows that the reader transmit time can be reduced as much as 90% compared to the conventional RFID reader. The system was validated by designing, fabricating, and testing of the tag and reader circuits within a lab environment.

Using in-seat electrical potential sensors for non-contact monitoring of heart rate, heart rate variability, and heart rate recovery

Detecting transient changes in heart rate and heart rate variability during experimental simulated autonomous driving scenarios can indicate participant arousal and cognitive load, providing valuable insights into the relationship between human and vehicle autonomy. Successfully detecting such parameters unobtrusively may assist these experimental situations as well as naturalistic driver monitoring systems within an autonomous vehicle. However, non-contact sensors must collect reliable and accurate signals. This study aims to compare the in-seat, non-contact Plessey EPIC sensor to the gold standard, contact Biopac sensor. Thirty participants took part in five-minute simulated autonomous vehicle journeys in a city environment and a rural environment, and a five-minute resting condition. To ensure the seat sensor was sensitive to elevated heart rate values, heart rate was also collected following the energetic Harvard Step Test. Lin concordance coefficients and Bland-Altman analyses were employed to assess the level of agreement between the non-contact Plessey EPIC sensor and the contact Biopac sensor for heart rate and heart rate variability. Analyses revealed a high level of agreement (rc > 0.96) between both sensors for one-minute averaged heart rate and five-minute averaged heart rate variability during simulated autonomous driving and rest, and one-minute averaged heart rate following the Harvard Step Test. In addition, the non-contact sensor was sensitive to significant differences during tasks. This proof of principle study demonstrates the feasibility of using the non-contact Plessey EPIC sensor to accurately detect heart rate and heart rate variability during simulated autonomous driving environments.

Effectiveness of Combined Stretching and Strengthening Exercise Using Rehabilitation Exercise System with a Linear Actuator and MR Damper on Static and Dynamic Sitting Postural Balance: A Feasibility Study

Postural imbalance induced by prolonged sitting can be improved by exercise therapy. The aim of study was to evaluate the influence of combined stretching and strengthening exercise using rehabilitation exercise system with a linear actuator and MR damper on static and dynamic sitting postural balance. Twelve subjects who sit almost 10 h a day participated in this study. The rehabilitation exercise system with a linear actuator and MR damper was manufactured to provide stretching and strengthening exercise. All subjects were asked to perform an exercise program that was designed to enhance postural balance by stretching the tight muscle and strengthening the weakened muscle. Body pressure distributions were analyzed for mean force and mean pressure using a seat sensor system. Trunk muscle activities were measured by attaching surface electrodes to the thoracic erector spinae, lumbar erector spinae, and lumbar multifidus muscle. All data were divided into two regions (dominant and non-dominant side) under four conditions: no pelvic tilt, lateral pelvic tilt, anterior pelvic tilt, and posterior pelvic tilt. Body pressure distributions and trunk muscle activities were compared between before and after performing exercise under static and dynamic sitting conditions. Both in static and dynamic sitting conditions, there were significant differences in body pressure distributions and trunk muscle activities between the DS and NDS before performing the exercise (p < 0.01). After performing exercise, the body pressure distributions increased on the dominant side while those decreased on the non-dominant side significantly (p < 0.01). In addition, the activities of all trunk muscles on the non-predominant side increased significantly (p < 0.01 and p < 0.05). These results showed that postural balance was improved by decreasing the differences in body pressure distribution and trunk muscle activity between the dominant and non-dominant side after performing exercise. From the results of this study, we concluded that the rehabilitation exercise system with a linear actuator and MR damper is suitable for providing combined stretching and strengthening exercise, and it could be helpful to maintain correct posture by enhancing postural balance during sitting.

Multilayered Composites with Modulus Gradient for Enhanced Pressure-Temperature Sensing Performance.

Highly sensitive and flexible composite sensors with pressure and temperature sensing abilities are of great importance in human motion monitoring, robotic skins, and automobile seats when checking the boarding status. Several studies have been conducted to improve the temperature-pressure sensitivity; however, they require a complex fabrication process for micro-nanostructures, which are material-dependent. Therefore, there is a need to develop the structural designs to improve the sensing abilities. Herein, we demonstrate a flexible composite with an enhanced pressure and temperature sensing performance. Its structural design consists of a multilayered composite construction with an elastic modulus gradient. Controlled stress concentration and distribution induced by a micropatterned structure between the layers improves its pressure and temperature sensing performance. The proposed composite sensor can monitor a wide range of pressure and temperature stimuli and also has potential applications as an automotive seat sensor for simultaneous human temperature detection and occupant weight sensing.

Solar Powered Self-Cleaning Toilet

In a country like India with over 1.3 billion people, 55% of this population which comes to about 600 million people has no access to toilets. The unhygienic and unclean condition of the toilets make it impossible for a large majority of the people to access them. A brilliant solution to this is e- Toilets which means Electronic toilets which integrates various sensors like IR sensor, smell sensor, and seat sensor for detecting human presence, bad odor and seat occupancy respectively. The entire system is powered using solar energy. The proposed system intends to revolutionize the system of flushing the toilets by using automation. The concept of half flush and full flush is being implemented to save the water. The various sensors like IR sensors, seat sensors and smell sensors will make the system efficient and reduce the power consumption. Thus, the aim of this project is to make a standalone system and help India to become a clean and green nation.

Design and implementation of seat occupancy detection system

Location of appropriate seats in seating areas of theaters remains a significant challenge that patrons of these enterprises face. There is therefore, the need for seat occupancy monitoring system to provide readily accessible seat occupancy information to clients and management of these halls. This paper presents the design and implementation of a low cost seat occupancy detection and display system which is capable of monitoring seat occupancy in halls efficiently. The system uses capacitive seat sensors which is designed based on the loading mode technology. It detects the presence of a human occupant using a single electrode. Occupancy data is relayed to a WiFi-enabled microcontroller unit which processes the data and wirelessly transfers the processed data to a central base station over a local area network for graphical and numerical display. Commands are also transferred from the base station to the microcontroller units when needed. Theoretical and empirical results show that the system is able to achieve seat occupancy monitoring accurately, neatly and cost effectively.Keywords: Capacitive sensing, seat occupancy, sensor cluster, microstrip transmission line, Wi-Fi

Development and evaluation of advanced seat and helmet for safer motorcycle users

The purpose of this research is to develop the prototypes of advanced motorcycle seat and protective equipment of compulsory helmet wearing through experimental evaluation. In this prototype, suitable sensors for detecting pillion, strapping chin and wearing helmet of motorcycle users are integrated with the existing motorcycle and helmet. These sensors were developed and investigated through the experimental testing procedures. For the evaluation of pillion seat sensor, the hip of dummy hybrid III 50th percentile male was used with the discrete values of mass on the sliding machine at each position of pillion seat. To conduct the experimental evaluation of strapping chin and wearing helmet conditions, the EN960 european standard headform were used at each position. Consequently, the functional detective range of the developed prototypes are identified and specified at pillion seat, chin strap and helmet wearing conditions. Additionally, these results are planned to develop an advanced system for supporting motorcycle users and increasing awareness of injury reduction.

Non-Invasive Detection of Respiration and Heart Rate with a Vehicle Seat Sensor.

This study demonstrates the feasibility of using a seat sensor designed for occupant classification from a production passenger vehicle to measure an occupant’s respiration rate (RR) and heart rate (HR) in a laboratory setting. Relaying occupant vital signs after a crash could improve emergency response by adding a direct measure of the occupant state to an Advanced Automatic Collision Notification (AACN) system. Data was collected from eleven participants with body weights ranging from 42 to 91 kg using a Ford Mustang passenger seat and seat sensor. Using a ballistocardiography (BCG) approach, the data was processed by time domain filtering and frequency domain analysis using the fast Fourier transform to yield RR and HR in a 1-min sliding window. Resting rates over the 30-min data collection and continuous RR and HR signals were compared to laboratory physiological instruments using the Bland-Altman approach. Differences between the seat sensor and reference sensor were within 5 breaths per minute for resting RR and within 15 beats per minute for resting HR. The time series comparisons for RR and HR were promising with the frequency analysis technique outperforming the peak detection technique. However, future work is necessary for more accurate and reliable real-time monitoring of RR and HR outside the laboratory setting.

Telehealth monitor to measure physical activity and pressure relief maneuver performance in wheelchair users

ABSTRACTThis study demonstrated the feasibility of a device for monitoring pressure relief maneuvers and physical activity for wheelchair users. The device counts the number of wheel pushes based on wheelchair acceleration and measures pressure relief maneuvers using a seat sensor consisting of three force sensing resistors (FSRs). To establish the feasibility of the seat sensor for the detection of pressure relief maneuvers, 10 wheelchair users and 10 non-disabled controls completed a series of wheelchair depression raises, forward trunk leans, and lateral trunk leans. The seat sensor was placed underneath the user’s seat cushion. To establish the feasibility of wheel push counting, 10 full-time wheelchair users navigated a flat 50-m outdoor track and a 100-m outdoor obstacle course during self-propulsion (e.g., wheel pushes) and during assisted-propulsion (e.g., no wheel pushes). Of the 240 performed pressure relief, 225 were properly classified by the seat sensor (accuracy: 94%, sensitivity: 96%, specificity: 80%). Sensitivity was highest for depression raises (98%) and lowest for front lean maneuvers (80%). The wheelchair activity monitor measured 2,112 pushes during the self-propulsion trials compared to 2,162 pushes measured with the instrumented push-rim (97.7%). During assisted-propulsion trials, there were 477 incorrectly identified pushes (8.0 per trial).

Influence of pelvic asymmetry and idiopathic scoliosis in adolescents on postural balance during sitting.

The effects of pelvic asymmetry and idiopathic scoliosis on postural balance during sitting were studied by measuring inclination angles, pressure distribution, and electromyography. Participants were classified into a control group, pelvic asymmetry group, scoliosis group, and scoliosis with pelvic asymmetry and then performed anterior, posterior, left, and right pelvic tilting while sitting on the unstable board for 5 seconds to assess their postural balance. Inclination and obliquity angles between the groups were measured by an accelerometer located on the unstable board. Pressure distribution (maximum force and peak pressure) was analyzed using a capacitive seat sensor. In addition, surface electrodes were attached to the abdominal and erector spinae muscles of each participant. Inclination and obliquity angles increased more asymmetrically in participants with both pelvic asymmetry and scoliosis than with pelvic asymmetry or scoliosis alone. Maximum forces and peak pressures of each group showed an asymmetrical pressure distribution caused by the difference in height between the left and right pelvis and curve type of the patients' spines when performing anterior, posterior, left, and right pelvic tilting while sitting. Muscle contraction patterns of external oblique, thoracic erector spinae, lumbar erector spinae, and lumbar multifidus muscles may be influenced by spine curve type and region of idiopathic scoliosis. Asymmetrical muscle activities were observed on the convex side of scoliotic patients and these muscle activity patterns were changed by the pelvic asymmetry. From these results, it was confirmed that pelvic asymmetry and idiopathic scoliosis cause postural asymmetry, unequal weight distribution, and muscular imbalance during sitting.

Noninvasive ambulatory measurement system of cardiac activity.

This work implements a noninvasive system that measures the movements caused by cardiac activity. It uses unobtrusive Electro-Mechanical Films (EMFi) on the seat and on the backrest of a regular chair. The system detects ballistocardiogram (BCG) and respiration movements. Real data was obtained from 54 volunteers. 19 of them were measured in the laboratory and 35 in a hospital waiting room. Using a BIOPAC acquisition system, the ECG was measured simultaneously to the BCG for comparison. Wavelet Transform (WT) is a better option than Empirical Mode Decomposition (EMD) for signal extraction and produces higher effective measurement time. In the laboratory, the best results are obtained on the seat. The correlation index was 0.9800 and the Bland-Altman limits of agreement were 0.7136 ± 4.3673 [BPM]. In the hospital waiting room, the best results are also from the seat sensor. The correlation index was 0.9840, and the limits of agreement were 0.4386 ± 3.5884 [BPM]. The system is able to measure BCG in an unobtrusive way and determine the cardiac frequency with high precision. It is simple to use, which means the system can easily be used in non-standard settings: resting in a chair or couch, at the gym, schools or in a hospital waiting room, as shown.

Monitoring Switch-Type Sensors via Inductive Coupling: Application to Occupancy and Belt Detection in Removable Vehicle Seats

Inductive links have been widely proposed for sensors placed in harsh or inaccessible environments, where wiring is unpractical. Usually, the sensor forms part of an LC resonant network. The resonant frequency is dependent on the quantity to be measured and is estimated from a coupled reader. This paper proposes the use of inductive links for switch-type sensors, i.e., those that can be roughly modeled as switches in response to the sensed parameter. First, we present a comprehensive analysis for an arbitrary number of sensors. Second, we show the feasibility of using inductive links for occupancy and belt detection in removable vehicle seats, where wiring is unpractical. The state (open or closed) of the related sensors is attained by first measuring the equivalent resistance of the readout inductor and then estimating its resonant frequency. Ferrite-core coils were used to increase the detection distance. Experimental tests were carried out using an impedance analyzer with the readout coil and commercial seat sensors at the resonant network. The resistance value at the resonant frequency decreased with an increasing distance between the coupled coils. Even so, detection of the sensors' state was feasible at all the tested distances, from 0.5 to 3 cm.

Vertical vibration characteristics of seated human bodies and a biodynamic model with two degrees of freedom

Understanding the vibration characteristics of a seated human body is critical for evaluation and improvement of ride comfort of various passenger vehicles. There have been very little publications about the vibration characteristics of a seated Chinese human body. By using wide-band white noise excitations and a homemade seat sensor, vertical vibration tests were carried out on 28 volunteers. Apparent masses were obtained for each volunteer at a frequency range of 1–20 Hz for various excitation levels. A biodynamic model, which has two degrees of freedom in parallel and includes a frame mass, was chosen to describe the vertical vibration characteristics of the seated human body. The model parameters were identified by means of a Gauss-Newton method with an error function defined in terms of both real and imaginary parts of the apparent mass against frequency. Based on the averaged data of the mass-normalized apparent mass from experiments, the model parameters and corresponding modal parameters were obtained for seated Chinese people at ages of 20–25 with standard weight. The apparent masses predicted by the biodynamic model with identified parameters agree very well with those obtained from experiments. Statistical analysis demonstrates the influence of volunteer’s height and weight on the model parameters for a seated human body.

Center-of-Pressure Displacement During Postural Changes in Relation to Pressure Ulcers in Spinal Cord-Injured Patients

To evaluate the center-of-pressure displacement in spinal cord-injured patients, to investigate dynamic sitting stability and its relationship with pressure ulcers. Sixteen spinal cord-injured patients and 18 healthy volunteers were included in the study. For the assessment of dynamic sitting stability, center-of-pressure displacement during maximum unsupported forward, backward, and right- and left-sided trunk leaning were measured with a seat sensor system, which was placed between the subject's buttocks and chair. Center-of-pressure displacements in all directions in spinal-injured patients were smaller than healthy volunteers (P < 0.05). Center-of-pressure displacements for high- and low-thoracic spinal cord-injured patients were not significantly different. History of previous pressure ulcer was not different between high- and low-thoracic spinal cord-injured patients (chi = 0.90, P = 0.62). Mean center-of-pressure displacement during forward and backward leaning were smaller in patients with pressure ulcer history (P = 0.04 and 0.03, respectively). The results of this study suggest that impaired dynamic sitting stability is associated with pressure ulcer development.

Audio speaker system for automotive vehicle

An automotive audio speaker system includes a set of main speakers and a set of sub-speakers. The main speakers are distributed about the vehicle cabin so as to focus audio sound near the center thereof. The main speakers reproduce separate right and left audio channels, either singly or in groups, and the sub-speakers reproduce monaural sound resulting from combination of the right and left channels. The sub-speakers are arranged and operated in such a manner that the audio focus is divided and displaced to form a number of acoustic images, each coinciding with a passenger seat. Seat sensors capable of detecting the presence of a passenger in a corresponding seat may be used to control the operation of the sub-speakers, either by adjusting their relative volumes or by distributing the right and/or left audio channels thereamong.

Factors Associated with Safety Belt Use in 1974 Starter-Interlock Equipped Cars

Interview data were obtained from 394 drivers whose safety belt use or non-use had been observed in 1974 cars equipped with a starter-interlock system linked to belts and seat sensors. Belt-use was not related to education, race, comfort-convenience ratings of belts, or having had a friend injured but not killed in a crash - factors that had been found related to belt use in previous research on earlier model cars not equipped with starter-interlock systems. Drivers in 1974 cars were more likely to be seen using belts if they used their cars on their jobs or were in and out of them frequently, on average, each day. Despite favorable ratings of the efficacy of belt use, over 40 percent of drivers in 1974 cars were not using belts and 29 percent claimed that the interlock was among the least liked features of their new car. /AUTHOR/