Personal Dead Reckoning Using IMU Mounted on Upper Torso and Inverted Pendulum Model

There has been an increasing demand for infrastructureless localization. Current approaches involving inertial measurement unit (IMU) generally utilize step detection and step counting to estimate the displacement. However, the accuracy is affected, because the step sizes are neglected. Some groups have proposed algorithms that involve placing the IMU on the foot to estimate the step size, but users have commented that it affects their walking. Hence, this paper presents a new method to estimate both the forward displacement and orientation with the IMU placed at the upper torso. Placing IMU at the upper torso to estimate horizontal displacement has been challenging, as the accuracy of the inertial sensors is greatly handicapped by the notorious integration drift when performing integration in the travel direction with the lack of opportunity for zero velocity update. Thus, a novel method is proposed in this paper by exploiting the vertical component of the accelerometer reading. An inverted pendulum model is proposed with a step detector and a step length estimation method. The system is implemented, and two sets of experiments are conducted to demonstrate the capability. The experiment sets include straight lines and rectangular shape path, and in each set, four step sizes of small, normal, large, and mixture are conducted for each test and each test is performed four times. The experimental results show an average displacement error of 1% for straight line paths and 2% for the rectangular paths.