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Pressure-based Staircase Step Counter

IP.com Disclosure Number: IPCOM000245408D
Publication Date: 2016-Mar-08
Document File: 6 page(s) / 196K

Publishing Venue

The IP.com Prior Art Database

Abstract

In this report, we present a novel staircase step counting algorithm, which uses the pressure signal collected with a wearable device to deduce the number of upward and downward steps. The presented algorithm accurately derives the staircase step numbers despite having a high noise level in the signal due to many unwanted external effects influencing the pressure signal, such as ventilation systems and the opening and closing of doors.

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Pressure-based Staircase Step Counter

Introduction

Nowadays, personal activity monitors are widely used to monitor human activity. Especially pedometers, which are devices measuring the number of steps an individual takes, have become a very popular as motivators and supervisors for daily exercises. The newest generation of pedometers available on the market do not only measure the number of steps (10,000 steps a day is a typical goal) but also monitor the distance walked and run, activity and sleep times, and energy expenditure (i.e., by counting the number of calories burned). This information is used to track an individual's activities and provide advice for a healthier living.

The IMUs (inertial measurement units) used in pedometers, are well suited to accurately monitor various activities. Based on these activities the energy expenditure is derived by additionally using body parameters, such as height and weight. However, recent studies show that these calorie counts are not very accurate because the number of burned calories also depends on the exercise intensity. For example, it makes a big

                           actual
difference whether an individual is walking along a flat surface or is going upwards or downwards. Hence, the prediction of the energy expenditure can be significantly improved by additionally monitoring vertical body movements, which can be done by using a barometric pressure sensor, and using this information to extend the computational model of the calorie counter [1, 2]. Barometric pressure sensors are very well suited for this task by having a high precision but at the same time a low power consumption. This report shows how the pressure sensor readings can be used to derive the number of steps walked upwards and downwards.

Challenges

The ambient barometric pressure varies smoothly from the Earth's surface to the top of the mesosphere, which is at around 100km above the surface. Close to the surface, 1 Pascal pressure difference corresponds to roughly 8.5 cm height difference. State-of-the-art pressure sensors are very sensitive and are able to measure such kind of pressure differences. Hence, these sensors are also able to distinguish a single staircase step, which is typically 16 cm high.

The major challenge is coming from the fact that the pressure signal is not static as it highly depends on environmental effects, namely:

Weather: The weather has a huge influence on the barometric pressure and is therefore used as precious information to predict future weather developments in the atmosphere, such as storms. The air pressure can easily change by 10 hPa within a day corresponding to a height difference of 85 m.

External effects: The pressure sensor is not only sensitive to the ambient barometric pressure but also to artificially created pressure waves. This is often observed inside buildings due to the opening and closing of doors, opening and closing of windows, ventilation and air conditioning systems, kitchen hoods, and...