The image projection apparatus includes a temperature detector that detects a temperature inside of the apparatus, and a controller that performs a protection operation when the temperature detected by the temperature detector is higher than a predetermined temperature. In such method, acceleration measurements obtained during one or more motions controlled at a stabilized gait of a human being are used, through accelerometers measuring on a time base accelerations according to at least one direction, and any locomotion irregularities are analyzed from reference measurements. An elastomeric plunger positioned in the passage includes a button with a sealing flange seated against the annular shoulder and a valve head biased against the valve seat.