The orl active floor

In this article a novel type of sensor system called the Active Floor is presented that allows the time-varying spatial weight distribution of the active office environment to be captured. The properties of the Active Floor are described, showing that it differs substantially from other commonly encountered sensor systems. Furthermore, classification of the footstep signature of a number of individuals is attempted by application of the hidden Markov model technique. e are concerned in this article with a weight-sensitive floor to be used as a means of sens- ing the distribution and time variation of loads within a building. Data obtained from such a floor can be fed into a distributed location system for the active office (l). The active floor is a square grid of conventional carpet tiles, each backed by 18 mm plywood and 3 mm steel plate, supported at the corners by cylindrical load cells which are instrument- ed to give us the total vertical force. In the data acquisition system described below we have found that the load cells are able to resolve weight changes of about 50 g. The grid has a 50 cm spacing, and a sampling rate of 500 Hziload cell is employed. Earlier work at ORL produced the Active Badgel system (2) where each person or object wears a device or tag that can communicate via infrared light with badge stations dis- tributed around the working environment. In contrast to this, a property of the floor that particularly interests us is that its operation does not require tagging or any special positioning of objects. Strong statements regarding weight and movement can be made about the environment without elaborate interpretation, and there is a wealth of data for more advanced analysis. To see why the floor is different from other sensing systems we have encountered, we analyze its properties in comparison with other systems.