Safe Estimation of Vehicle Side-slip for an Autonomous Heavy Vehicle
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Typ
Examensarbete för masterexamen
Program
Systems, control and mechatronics (MPSYS), MSc
Publicerad
2019
Författare
Kotur, Pranay
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
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Sammanfattning
Stabilizing the lateral movement of the vehicle is crucial for functional safety. The variables required to ensure
lateral stability cannot directly be measured from the vehicle. Hence, data from sensors is coupled with the
estimates from the state estimator to obtain reasonably good estimates with a fair amount of accuracy. This
technique called Sensor Fusion, helps to iteratively eliminate any outliers or anomalies and obtain the desired
estimates.
In this thesis, three different models of state estimators were developed in MATLAB/Simulink and their results
compared. Their accuracy was compared to select the best model which would estimate the side-slip correctly.
Each of the models has been given bounds (i.e., a minimum and a maximum bound) for values of side-slip.
These bounds were based on tire wear-and-tear and other tire parameters which would simulate the real-world
experiences. So the main goal was to design the estimator such that the bounds would encompass the actual
measured value from the sensors (also called as 'ground truth').
The first model used was based on the linear bicycle model given in lateral dynamics. This was basically a
mathematical model with a given set of equations along with vehicle parameters and variables. For vehicles
with simple configurations (i.e., passenger cars and rigid-body trucks) whose lateral behaviour is relatively
simpler compared to multi-axle or multi-trailer vehicles, the linear bicycle model gives reasonably accurate
estimates as long as the sideslip angle doesn't exceed 0.5 degrees . The second method used was the kinematics
model which integrated the lateral acceleration to give lateral velocity, which in turn was used to compute
side-slip. However, as is present with most integrators, this methods suffers from what is called as integration
drift. The third and final model was a washout filter model which was effectively a combination of a high-pass
(HP) and a low-pass (LP) filter. Lateral velocities from both the bicycle model as well as the kinematic model
act as inputs for this filter. This filter retains decent accuracy even for high values of side-slip and is not prone
to the errors which the above-mentioned models suffer from.
Beskrivning
Ämne/nyckelord
side-slip angle , state estimator , tractor-semitrailer , lateral stability