Читать книгу Pedestrian Inertial Navigation with Self-Contained Aiding - Doruk Senkal, Andrei M. Shkel - Страница 15

In pedestrian inertial navigation, depending on the approaches to be taken and the application restrictions, the IMU can be mounted on different parts of body to take advantage of different motion patterns, such as head, pelvis, foot, wrist, thigh, and foot. Pelvis, or lower back, was the first explored IMU mounting position in the literature, because these parts of the body experience almost no change of orientation during walking, which greatly simplifies the modeling process for both strapdown inertial navigation and SHS [15]. In subsequent studies, thigh and shank were explored, such that IMU can directly measure the motion of the leg, which is directly related to the step length by the biomechanical models [16,17]. More recently, in order to integrate pedestrian inertial navigation with smart phones and wearable devices, such as smart watches and smart glasses, pocket, wrist (or hand hold), and head are becoming the IMU mounting positions of interest [18–20]. The foot‐mounted IMU has also been demonstrated for SHS, but this placement of sensors is mostly used in the ZUPT‐aided pedestrian inertial navigation, instead of SHS.

Head‐mounted IMUs are usually used for heading angle estimation, since it experiences lowest amount of shock and almost no change of orientation. Besides, it is usually convenient to mount the IMU on the helmet for first responders and military applications [21]. However, the low amplitude of angular rate and acceleration during walk makes it hard for step length detection. In addition, the gazing direction may not be aligned with walking direction during navigation. Pelvis‐mounted IMUs have the ability of estimating the step length for both legs with one single device, compared to the IMUs mounted on the legs. It is also more convenient to align the IMU to the walking direction compared to the head‐mounted IMUs. Pocket‐mounted IMUs and hand‐held IMUs are mostly developed for pedestrian inertial navigation for use with smart phones. In this approach, the IMU is not fixed to a certain part of the body, and its orientation may change over the navigation applications due to different hand poses and different ways to store the smart phone in the pocket. It makes the SHS algorithm more complicated than other IMU mounting positions. Foot‐mounted IMUs will experience the highest amount of shock and vibration due to the heel shocks during walking [22]. As a result, a more stringent requirement on the IMU performance will be necessary, such as high shock survivability, high bandwidth and sampling rate, low g‐sensitivity, and low vibration‐induced noise [23]. However, with foot‐mounted IMUs, a close‐to‐stationary state of the foot during the stance phases will greatly reduce the navigation errors in the ZUPT‐aided pedestrian inertial navigation.