# Wave Excitation Force Estimation of Wave Energy Floats Using Extended Kalman Filters

## TL;DR

This paper explores the use of Extended Kalman Filters to estimate wave excitation forces on wave energy converters from measurement data, enhancing control strategies for wave energy devices.

## Contribution

It introduces and compares two novel EKF-based methods for estimating excitation forces, including a direct state inclusion and a harmonic oscillator model, validated with experimental data.

## Key findings

- Both methods successfully estimate excitation forces under various wave conditions.
- The harmonic oscillator model shows robustness to measurement noise.
- Sensitivity analyses reveal the impact of model parameters and sampling rates.

## Abstract

In many advanced control strategies the wave excitation force is key to determining the control input. However, it is often difficult to measure the excitation force on a Wave Energy Converter (WEC). The use of Kalman filters to estimate the wave excitation force based on readily available measurement data can potentially fill the gap between the development of WEC control strategies and the data that is available. Two different estimation methods using an nonlinear Extended Kalman Filter are tested on experimental wave tank data for a heaving semi-submerged float. The first method relies on directly including the excitation force as a state in the first order dynamics---which allows the "random walk" of the Kalman filter to identify an estimate of the excitation force. The second method of estimation involves modeling the wave excitation force as a harmonic oscillator comprised of sinusoidal components. Both methods are evaluated for a variety of incident waves and additional sensitivity analyses are performed to investigate the susceptibility of these estimation methods to changes in the model, measurement noise, and sampling rate.