Abstract
Keywords - Human-Machine Interface, Brake Pedal Feel, Physiological Stress, Surface Electromyography, Muscular System
The control elements in motor vehicles must be designed as far as possible to save the operator from physiological strain and fatigue while the car is being driven. If these criteria are not fulfilled, or if pain is even felt by the driver while driving, the vehicle in question is felt to be uncomfortable. The risk of muscle strain arises primarily during operations which last only a short time, but which nonetheless require considerable physical exertion. Signs of fatigue, on the other hand, generally occur in connection with driving activity which demands comparatively little physical effort but does so monotonously and continually. There are many open questions at present on known means of registering the strain in such cases, and of establishing concrete connections between the strain and its effect on the driver.
This paper describes an approach involving interdisciplinary methodology which has the potential to contribute new findings and development tools of benefit to the designing of humanmachine interfaces. The methodology used captures in objective terms the major parameters affecting physiological strain on drivers at the wheel. The braking process is the example here investigated. The combination of automotive physics, human physiology and human psychology which is applied in meeting the challenge is, to date, a unique interdisciplinary constellation. One element of the approach is an analysis of the interface parameters in the car itself; specially developed test vehicles made this possible. They were equipped with fully active servo-hydraulic actuators to produce the pedal and braking features in their many variations. The second main focus of the investigations was to achieve measurability of the demands placed on the driver.
One method established in the field of motion sciences for registering and identifying muscles and muscle chains as they are made to work or put under strain is surface electromyography (EMG). This is a non-invasive technique in which myoelectric potentials generated by muscular activity are analysed so that, conclusions can be drawn about physiological strain on the driver of a vehicle. In the present instance, the different muscles and groups of muscles in the lower and upper extremities and in the trunk were subjected to EMG while test drivers were applying the footbrake under various conditions. Selected results from the research are here presented. It is shown that these muscles are involved in how the driver controls the act of braking, and the investigation covers a number of parameters. For different acts, there are differences in both the intensity of the muscular activities and in the selection of which muscles to involve.