In this paper, velocity estimation method for caster odometers is proposed. Caster odometer is a sensor of travel distance and attitude angle using caster mechanism that has twodegree of rotational freedoms. We calculate velocities of a vehicle utilizing the output measured by caster odometers , however, the caster mechanism has nonlinearity component. To deal with the nonlinearity of the caster mechanism, a velocity is estimated by the extended Kalman filter. It is expected to reduce the effect of noise with higher precision than conventional methods (approximated differentiation, extended Luenberger observer). We confirm the accuracy of the proposed estimation by comparing to the conventional method in numerical simulation.
This paper proposes a velocity observer for caster wheel odometers resisting steady-state error. The proposed method is established by attaching a feedback loop of error integration to extended Luenberger observer (ELO). The stability of the proposed observer is proved, moreover, the steady-state error converges to a bounded area where the bounds are defined by design parameters. This fact guarantees that the proposed method is robust against a certain class of model error as well as measurement noise. The advantage over the simple ELO or the conventional approximated differentiator is verified in numerical simulations and experiments.
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