Sensor Fusion concerns model-based state estimation from a multitude of sensors.
The model is of the form
x[k+1] = f(x[k],u[k],w[k]),
y[k] = h(x[k],u[k])+ e[k],
where
x[k] denotes the state vector,
u[k] is an input signal, and
y[k] contains the sensor measurements.
Here,
w[k] is the process noise and
e[k] the measurement noise.
The model is specified by a
state predictor
f(x[k],u[k],w[k]) and a measurement relation
h(x[k],u[k]), together with noise distributions for
w[k]
and
e[k].
The goal in sensor fusion is to utilize information
from spatially separated sensors of the same kind (so called sensor
networks), sensors of different kind and finally on a more abstract
level information sources in general in terms as for example
geographical information systems.
The current activities concern
- Particle filter theory The particle offers a general
algorithm for state estimation in the models above, with potentially better peformance than the classical extended Kalman filter (EKF) for nonlinear or non-Gaussian systems. Our contributions involve:
- Convergence analysis for the state estimate, where results with relaxed asssumptions have been presented.
- Marginalization to mitigate the complexity of the particle
filter, which in the end allows a scalable algorithm.
- Applications
- Fusion of sensor observations and GIS. Concrete applications are
terrain navigation of aircraft using altitude GIS, terrain navigation
of underwater vehicles using bottom depth GIS, localization in road
networks using road GIS, surface ship navigation using radar and sea
chart GIS, etc.
- SLAM Simultaneous Localization And Mapping (SLAM) aims at
solving to tasks in the same filter, namely localization of the host
vehicle and at the same time building a map (GIS) of the surrounding.
Both EKF and PF based approaches have been proposed, and we are
actively developing these approaches for different applications
(unmanned aerial vehicles for instace).
- Collision Avoidance (CA) is one important application of
state estimation, where the estimated state is used to assess the risk
for a conflict, and also for evaluating different evasive maneuvers.
- Automotive CA is researched with Volvo Car in a serie of joint
projects.
- Airborne CA, often referred to as sense and avoid, is a joint
project with SAAB Aerospace.