Alain Priez

Surface electromyography as a tool to study the head rest comfort in cars.

In this study, two methods were presented in order to evaluate objectively the comfort of head rests in cars using surface electromyography (SEMG). First, the Amplitude Probability Density Function (APDF) was computed. Extremely low level intensity activities were measured. No significant differences were observed on SEMG global activity between experiments with and without a head rest. Second, instead of computing one APDF, several APDF were calculated over time. Analyses focused on the rate of evolution of APDF parameters. This was a time varying APDF (TAPDF). This last method allowed a better diagnosis than the first one. For drivers, significant decreases in SEMG activity were observed when using a head rest. For passengers, a contradictory increase in SEMG activity was observed during experiments with a head rest. This observation was explained by the seat back angle chosen by passengers.

An Original Method to Predict Brake Feel: A Combination of Design of Experiments and Sensory Science

A brake by wire research vehicle was developed and equipped with an electrical active pedal feel emulator. With this device, the relationships between brake pedal force, pedal travel and vehicle deceleration are fully adjustable. We can tune 11 technical parameters (7 for the force/travel pedal relationship and 4 for the deceleration/travel relationship). A Plackett-Burman design of experiments was used to generate 12 unique braking laws. These laws were evaluated by a sensory descriptive analysis panel on seven criteria. Partial Least Square (PLS) analysis was used for data treatment. This analysis sorted out the most influential technical parameters on brake feel. As a result, a software application able to predict brake feel using technical parameters was implemented.

Time varying amplitude probability density function: application to the study of head rest comfort in a car

Evolution of the amplitude probability density function (APDF) of EMG signals from neck muscles were studied in order to make an objective diagnostic of the benefit of using a head rest in a car. This method is simple: several APDFs over a long period of time are computed and observed. Interesting results are obtained with 6 subjects (N=8), especially with evolutions of static and median load. The sign of the evolution appears to be discriminant. Obviously, the major drawback is the lack of explanation of results observed: as the classical APDF, this method is only an a posteriori approach.

Application of a detection-characterization frame for SEMG: preliminary results about head rest comfort in cars

Describes a detection and characterization frame for Surface ElectroMyoGraphy (SEMG). Detection was based on a classical test of variance comparison. For labelling, a method based on a Bayesian approach was performed. Thresholds were learned supervisely. The aim is the extraction of significant parameters from a postural SEMG in long term recordings. The temporal evolution of postural SEMG was then considered. Results about head rest comfort evaluation are presented and compared to previous studies. The observed results remain subject dependent.