Thermal comfort of aeroplane seats: influence of different seat materials and the use of laboratory test methods

This study determined the influence of different cover and cushion materials on the thermal comfort of aeroplane seats. Different materials as well as ready made seats were investigated by the physiological laboratory test methods Skin Model and seat comfort tester. Additionally, seat trials with human test subjects were performed in a climatic chamber. Results show that a fabric cover produces a considerably higher sweat transport than leather. A three-dimensional knitted spacer fabric turns out to be the better cushion alternative in comparison to a moulded foam pad. Results from the physiological laboratory test methods nicely correspond to the seat trials with human test subjects.     

Virtual optimisation of car passenger seats: Simulation of static and dynamic effects on drivers’ seating comfort

The virtual investigation of static and dynamic effects on seating comfort requires the application of an adequate human model. An appropriate seat model considering static and dynamic properties of the structure, the foam and the trim is needed to perform an optimisation for a lower load level on the driver. The evaluation of the seating comfort must be divided into a static and a dynamic part. For the computation of the relevant physical quantities with the human model CASIMIR and a detailed seat model, the finite-element solver ABAQUS (ABAQUS Inc., http://www.abaqus.comwww.abaqus.com) is used.

To reflect a real driving situation, in the first step the human model is adapted to the right posture, which is given by the inclination of the cushion and the backrest. The seating process is then computed by the load due to gravity. The static comfort is mainly evaluated by the seat pressure distribution. Results such as the H-point and the meat-to-metal value can give additional important informations for the ergonomic and structural design of the seat. As the model reflects the nonlinear properties and the finite-element solver considers the effects out of finite displacements and contact, a good correlation with measurement is achieved.

The dynamic simulation is carried out by a unit excitation of the seat slides at the clamping points. To consider frequency-dependent properties of foam, structure and the human body, the computation uses an implicit solver. Therefore the model is linearised after the nonlinear static seating process.

Dynamic comfort is evaluated by the seat-transfer function. The presented numerical method leads to a good correlation with the measurements. Superposing the results with real excitation signals enables the estimation of the dynamic loads as muscle or intervertebral disc forces on the driver.

Altogether this method, in an early state of the development enables the user to optimise a car passenger seat structure due to the static and dynamic comforts. Considering boundary conditions as higher load amplitudes and accelerations, the advantages of virtual development can also be applied for construction vehicle seats.

Relevance to Industry

The present method allows the evaluation of static and dynamic comforts in a virtual phase of seat development. Besides the reduction of time and costs, the application of the simulation enables the testing of new materials and ways of construction with low investment.     

An ergonomics investigation into human thermal comfort using an automobile seat heated with encapsulated carbonized fabric (ECF).

This report presents the results of an ergonomics investigation into human thermal comfort using an automobile seat heated with an encapsulated carbonized fabric (ECF). Subjective and objective thermal comfort data were recorded while participants sat for 90 min in a heated and a non-heated automobile seat in an environmental chamber. Eight male participants each completed eight experimental sessions in a balanced order repeated measures experimental design. The conditions in the chamber were representative of a range of cool vehicle thermal environments (5, 10, 15 and 20 degrees C; in the 20 degrees C trial participants sat beside a 5 degrees C 'cold wall'). Participants in the heated seat condition used the heating controller with separate temperature control over the back of the seat (squab) and bottom of the seat (cushion) in an effort to maintain their thermal comfort while wearing the provided clothing, which had an estimated insulation value of 0.9 Clo. The trials showed that participants' overall sensations remained higher than 'slightly cool' in the heated seat at all temperatures. Participants' overall discomfort remained lower (i.e. more comfortable) than 'slightly uncomfortable' at temperatures ranging down to nearly 5 degrees C in the heated seat. Hand and foot comfort, sensation and temperature were similar in both seats. Asymmetric torso and thigh skin temperatures were higher in the heated seat although no significant discomfort was found in the front and back of the torso and thigh in either seat. Participants reported no significant difference in alertness between the control and heated seat.     

Effects of heated seat and foot heater on thermal comfort and heater energy consumption in vehicle

Subjective experiments involving 12 different conditions were conducted to investigate the effects of heated seats and foot heaters in vehicles on thermal sensation and thermal comfort. The experimental conditions involved various combinations of the operative temperature in the test room (10 or 20°C), a heated seat (on/off) and a foot heater (room operative temperature +10 or +20°C). The heated seat and foot heater improved the occupant's thermal sensation and comfort in cool environments. The room operative temperature at which the occupants felt a ‘neutral’ overall thermal sensation was decreased by about 3°C by using the heated seat or foot heater and by about 6°C when both devices were used. Moreover, the effects of these devices on vehicle heater energy consumption were investigated using simulations. As a result, it was revealed that heated seats and foot heaters can reduce the total heater energy consumption of vehicles.

Statement of Relevance: Subjective experiments were conducted to investigate the effects of heated seats and foot heaters in vehicles on thermal comfort. The heated seat and foot heater improved the occupant's thermal sensation and comfort in cool environments. These devices can reduce the total heater energy consumption in vehicles.     

Definition and determination of the bus oscillatory comfort zones

The paper defines “equal oscillatory comfort zones” as a novel concept in the sphere of the bus vertical dynamics. Oscillatory zones are determined using the original and validated oscillatory model of the intercity bus and comfort criteria according to the international ISO 2631/1997 standard requirements. The bus spatial oscillatory model with 65 degrees of freedom (DOF) was built in the ADAMS/View module of the multibody software package MSC.ADAMS. The model was excited by two different real road surfaces: poor asphalt-concrete and good asphalt-concrete pavements, registered at the speed of 64 km/h and 90 km/h respectively. It was found by simulation that oscillatory zones with different comfort assessments exist in the bus. The most comfortable oscillatory zone is in the middle part of the bus (between the front and the rear axle), whereas the least comfortable oscillatory zone is on the rear bus overhang. For the purpose of the ride comfort harmonization, using Design of Experiments (DOE) analysis, new oscillatory parameters are proposed for passenger seats which do not ensure satisfactory oscillatory comfort level. It is concluded that harmonization of oscillatory comfort for all bus passengers could be achieved for good asphalt-concrete excitation. For the poor road excitation it is possible to achieve significant improvement of comfort, especially for the assistant driver and passengers in the bus rear overhang. On a poor asphalt-concrete pavement, by using the proposed seat oscillatory parameters, the allowed exposure time for vertical whole body vibration would be considerably extended.Relevance to industryOscillatory comfort has a particular importance for users of intercity buses traveling longer distances. Comfort assessment of each bus user and mapping of comfort zones can indicate the individual seat and group of the seats on which the oscillatory comfort is reduced. Proper selection of seat oscillatory parameters can improve users comfort. Results of such an analysis can significantly help bus designers and manufacturers in order to improve and harmonize oscillatory comfort on the whole vehicle platform.     

Driver sitting comfort and discomfort (part II): Relationships with and prediction from interface pressure

Pressure at the driver–seat interface has been used as an objective method to assess seat design, yet existing evidence regarding its efficacy is mixed. The current study examined associations between three subjective ratings (overall, comfort, and discomfort) and 36 measures describing driver–seat interface pressure, and identified pressure level, contact area, and ratio (local to global) variables that could be effectively used to improve subjective responses. Each of 27 participants was involved in six separate driving sessions which included combinations of two seats (from vehicles ranked high and low on overall comfort), two vehicle classes (sedan and SUV), and two driving venues (lab-based and field). Several pressure variables were identified as more effective for assessing sitting comfort and discomfort across a range of individual statures. Based on the results, specific approaches are recommended to improve the sitting experience: (1) lower pressure ratios at the buttocks and higher pressure ratios at the upper and lower back; and (2) balanced pressure between the bilateral buttocks, and between the lower and upper body. Finally, separate analyses supported that human–seat interface pressure was more strongly related with overall and comfort ratings than with discomfort ratings.

Relevance to industry

Several interface pressure variables were identified that showed associations with subjective responses during sitting. Use of these measures is suggested to improve the quality of car seats.     

Effect of lumbar support on seating comfort predicted by a whole human body-seat model

Automobile seat greatly affects the ride comfort of drivers in a prolonged driving. Not only the layout parameters of automobile seats, such as seat height, cushion inclination angle, backrest inclination angle, etc, but also the backrest surface related with lumbar support all affect the seating comfort. The human body-seat system includes the three-dimensional data of body based on anatomy and anthropometry, three-dimensional data of seat and adjustable assembly interaction between body and seat based on human body kinematics. Body height and driving posture are adjusted in POSER software, then the solid model of human skin, skeleton and muscle are created in ANSA software, and the integrated model of body-seat system is created in ABAQUS software. The adjustment of the lumbar support parameters is achieved by setting boundary condition of lumbar support region of seats. The finite element model of human body-seat system is validated by comparison to available literature results. At last the finite element model is applied to analyze the effect of lumbar support parameters of seats on the interaction between body and seat under the action of gravity. The pressure value and distribution, contact area, total force of backrest and intervertebral disc stress are obtained. The result shows that the optimal thickness of seat's lumbar support size for the seating comfort is 10 mm after comprehensive comparison and evaluation.Relevance to industry: This study investigated the effects of lumbar support on seating comfort, and can be used to protect the lumbar health. The modeling and simulation method can be applied for the optimization design of vehicle seats.     

Comfort seat design: Thermal sensitivity of human back and buttock

In recent years, comfort seat design has received widespread attention from researchers. One of the factors that could contribute to comfort is the thermal influence due to the interaction between the human and the seating surface, for which literature is limited.In this paper, a laboratory experimental setup was used to detect and analyse the temperature changes at interface between seated subjects and a sensorized automotive seat. Acquired temperatures were processed in order to identify a mathematical model for describing the temperature changes at the interface.The main target of the study was the identification of the most sensitive areas of the human body to temperature variation while seated and its effect on local and overall perceived thermal comfort.Statistical analysis showed that the effects of temperature were most perceived in the “Upper Body” (UB) and less in the “Lower Body” (LB). The shoulders, the sides of the back, the back and the buttocks were most sensitive to temperature changes at the interface. Differences have been highlighted also between male and female subjects.Relevance to industryThe identification of the most sensitive areas of the human body to temperature variation, while seated, and the identification of the logarithmic model for describing the temperature changes should allow seat designers to define targets and strategies in developing cooling and heating systems for car seats, taking into account, in a preventive evaluation, the most probable perceived thermal comfort.     

Some observations regarding the vibrational environment in child safety seats

A growing issue in the area of vehicular ride comfort is that of child safety seats. Postural, thermal and vibrational comfort considerations are finding their way into child seat design. This paper makes some observations regarding the current state of child safety seat design, then goes on to present the results of vibration tests performed over two road surfaces using two child seats and two children. The vibration levels measured at the interfaces between the children and their seats were found to be higher than the vibration levels between the driver and the driver's seat. Calculated power spectral densities and acceleration transmissibility functions showed that the vibration transmission characteristics of the coupled system consisting of the automobile seat, child seat and child were different from those of the driver/seat system. Whereas, automobile seats normally reduce vibrational disturbances at most frequencies, the child seats tested amplified vibration at most frequencies up to 60 Hz.     

Effects of heated seats in vehicles on thermal comfort during the initial warm-up period

Eight subjects participated in a subjective experiment of eight conditions to investigate the effects of heated seats in vehicles on skin temperature, thermal sensation and thermal comfort during the initial warm-up period. The experimental conditions were designed as a combination of air temperature in the test room (5, 10, 15, or 20 °C) and heated seat (on/off). The heated seat was effective for improving thermal comfort during the initial warm-up period when air temperature was lower than 15 °C. Use of heated seats prevented decreases in or increased toe skin temperature. Heated seats also increased foot thermal sensation at 15 and 20 °C. Optimal thermal sensation in contact with the seat was higher when air temperature was lower. Optimal skin temperature in contact with the seat back was higher than that with the seat cushion. Moreover, these optimal skin temperatures were higher when air temperature was lower.