Name Absolut Sensor Aided Inertial Navigation Systems
Funding Reference ISR/DSOR Internal Project
Dates 2004|2006

This project focuses on the design and implementation of inertial navigation systems that must provide, in real time, accurate estimates of the linear and angular positions, and velocities of the autonomous vehicles where they are installed. Micro-Electro-Mechanical Systems (MEMS) are nowadays key technologies to develop Inertial Navigation Systems for autonomous vehicles because of their reduced size, cost and power consumption, relative to conventional devices. Currently off the shelf available MEMS, like rate gyros and accelerometers, are still much less accurate than standard inertial sensors. This requires an extra effort in the development of online compensation techniques involving absolute sensors for biases compensation and platform alignment. The overall goal of this project is to exploit different absolute sensor characteristics, in their natural measurement space, using advanced tightly-coupled architectures to develop MEMS based INS for autonomous vehicles. It is expected to improve the natural INS drifting behaviour resorting to sensors that are currently available in autonomous vehicles. A few cases of interest include:
1) Using state of the art GPS technology, the position of a helicopter can be measured with sub-metric accuracy at low data rate in a pre-specified datum. This accuracy can be achieved using commercially available differential GPS receivers. The Inertial Measuring Unit (IMU) provides accelerations and attitude changes of the platform. The fusion of these data with the linear position available from the GPS receiver produces high update rate accurate position and attitude estimates that are fundamental to stabilize the platform and support the guidance and control system for high precision surveying applications.
2) A laser range finder (LRF) generates highly accurate distance measurements (less than 5 cm), which can be used as an aiding sensor in the take-off, landing phases, or for local navigation close to structures providing estimates of the altitude (distance at the local vertical relative to the ground) and vertical velocity of the helicopter to the specialized navigation systems.
Constraints imposed by the different aiding sensors, like availability and accuracy, require smooth filter switching techniques between different INS compensation techniques.

Research Groups Dynamical Systems and Ocean Robotics Lab (DSOR)
ISR/IST Responsible
Carlos Silvestre
Paulo Oliveira