A Micro Aerial Vehicle with Precise Position and Attitude Sensors

This study shows the potential of navigation technologies in the field of position and orientation determination on a micro aerial vehicle (MAV), which weight does not exceed 5 kg. Although the MAV systems feature high flexibility and capability of flying into areas that are inhospitable or inaccessible to humans, the lack of precision in positioning and attitude estimation on-board decreases the gained value of the captured imagery. This limits their mode of operation to indirect georeferencing. This paper pre-sents the development of a low cost MAV with navigation-sensor payload that shall assure a position and attitude control with accuracy from which either direct or integrated sensor orientation can benefit. After describing the hardware configuration and the synchronization of all measurements we present a case study that evaluates the performance of the positioning component and its application on integrated sensor orientation without ground control. There we show that thanks to the implementation of a multi-frequency, low power GNSS receiver, the system can potentially attain the mapping characteristics of much larger platforms flown on man-operated carriers while keeping the sensor size and weight suitable for MAV operations. The attitude accuracy of the developed board hosting several MEMS-IMUs is evaluated dynamically on a terrestrial vehicle using a reference (navigation grade) INS. Although this method offers continuous evaluation of the orientation accuracy and the obtained results are satisfactory with respect to the foreseen operations, this performance remains to be confirmed in a flight.

Autonomous and non-autonomous dynamic model based navigation system for unmanned vehicles

Mehran Khaghani, Jan Skaloud

A navigation system including a vehicle dynamic model (VDM) that serves as the main process model within a navigation filter is described. When used in an unmanned aerial vehicle (UAV), the navigation system may work in communication with inertial measurement units (IMUs) and environment dependent sensors such as GNSS receivers. Particularly, the navigation system is beneficial in the case of GNSS signal reception outages, where conventional IMU coasting drifts quickly. Yet, the navigation system may also be employed in other scenarios, for example during GNSS presence for improved positioning, velocity and attitude determination, or in combination with GNSS when no IMU is available by design or due to a failure. In the navigation system, a solution to VDM equations provides an estimate of position, velocity, and attitude, which can be updated within a navigation filter based on available observations, such as IMU data or GNSS measurements.

2016

Applicability Of New Approaches Of Sensor Orientation To Micro Aerial Vehicles

Martin Rehak, Jan Skaloud

This study highlights the benefits of precise aerial position and attitude control in the context of mapping with Micro Aerial Vehicles (MAVs). Accurate mapping with MAVs is gaining importance in applications such as corridor mapping, road and pipeline inspections or mapping of large areas with homogeneous surface structure, e.g. forests or agricultural fields. There, accurate aerial control plays a major role in successful terrain reconstruction and artifact-free ortophoto generation. The presented experiments focus on new approaches of aerial control. We confirm practically that the relative aerial position and attitude control can improve accuracy in difficult mapping scenarios. Indeed, the relative orientation method represents an attractive alternative in the context of MAVs for two reasons. First, the procedure is somewhat simplified, e.g. the angular misalignment, so called boresight, between the camera and the inertial measurement unit (IMU) does not have to be determined and, second, the effect of possible systematic errors in satellite positioning (e.g. due to multipath and/ or incorrect recovery of differential carrier-phase ambiguities) is mitigated. First, we present a typical mapping project over an agricultural field and second, we perform a corridor road mapping. We evaluate the proposed methods in scenarios with and without automated image observations. We investigate a recently proposed concept where adjustment is performed using image observations limited to ground control and check points, so called fast aerial triangulation (Fast AT). In this context we show that accurate aerial control (absolute or relative) together with a few image observations can deliver accurate results comparable to classical aerial triangulation with thousands of image measurements. This procedure in turns reduces the demands on processing time and the requirements on the existence of surface texture. Finally, we compare the above mentioned procedures with direct sensor orientation (DiSO) to show its potential for rapid mapping.

Copernicus Gesellschaft Mbh2016

Applicability Of New Approaches Of Sensor Orientation To Micro Aerial Vehicles

Martin Rehak, Jan Skaloud

Copernicus Gesellschaft Mbh2016