An integrated model for predicting driver’s discomfort while interacting with car seat and car controls
A driving task requires physical demands from the driver to operate car controls, while sitting on the car seat. The near static seated posture in a confined space may causes discomfort and fatigue. In Malaysia, fatigue is the third highest contributing factors to road accident, accounting for 15.7%. Fatigue can interfere with concentration while driving the car. When the driver is getting fatigue, it may reduce the performance, and hence increase the risk of road accident. This show that fatigue effect can cause danger to the driver. The four main objectives of this research are: (1) to evaluate driver’s discomfort and performance while engaged with the car seat and car controls based on subjective assessment.; (2) to analyse the pressure interface on the car seat based on different driving positions.; (3) to evaluate the SEMG surface electromyography (SEMG) signal for the muscle activity based on different driving positions and actions.; and (4) to develop integrated model to predict driver’s discomfort while engaged with the car seat and car controls. Eleven test subjects participated in this experiment. The data for this research were collected by using mixed method approach, comprising of the subjective (Visual Analogue Scales, VAS) and objective assessment methods (SEMG and pressure measurement). The VAS was the subjective assessment method used for measuring the car driver’s discomfort perception while engaging with car seat and car controls, namely steering wheel, manual gear and accelerator pedal. The SEMG was used to measure muscle activity for Deltoid Anterior (DA), Gastrocnemius Medial (GM) and Tibialis Anterior (TA) involving two different positions, the closest seated position to the car controls (Position A) and the further seated position from the car controls (Position B). Having done that, the data were analysed by using Temporal and Amplitude Analysis based on Maximal Voluntary Contraction. The SEMG analysis was in accordance to the SEMG for the Non-Invasive Assessment of Muscles recommendation. The pressure mat was used to measure the pressure distribution of the car seat. In addition, the body measurement, consisting of anthropometric dimension and the joint angle were measured in this study. Referring to VAS assessment, subjects feel more discomfort at Position B while operating the steering wheel at 45 turning degree and gear during changing the gear to gear 1. For pedal control, the subjects experienced discomfort at Position A particularly when releasing the pedal. The SEMG’s findings for the steering wheel task showed the DA at Position B with 45 turning degree showed a higher muscle contraction. Changing the gear to Gear 1 at Position B demonstrated the highest Amplitude at the DA. For pedal control, TA depicted the highest muscle contraction in releasing action at Position A, while the GM showed the highest muscle contraction in pressing action at Position B. In terms of pressure distribution measurement, the buttocks part at Position A depicted the highest mean pressure. The regression test was used to determine the level of significance whether the coefficient of working muscle activity can be used as characteristics and predictors for driver’s discomfort. From the results, the prediction model could be developed. The results indicated that integration between the body measurement and pressure interface or muscle activity show a higher R2; car seat (R2 = 0.952), steering (R2 = 0.983), gear (R2 = 0.980), and pedal (R2 = 0.911 and 0.952). Thus, it can be concluded that the prediction on drivers’ discomfort when driving in different conditions produces better results when incorporating the body measurement that is related with the car seat and car controls.