Fig. 6 Example of a a cross-section and 1D profile of the reference velocity structure used in the FDM wave propagation simulation, and b a magnified image of the area surrounded by the rectangle in Fig. 6a.
The top level control is responsible of producing the reference velocity that is used by the lower level controller to regulate the actual velocity of the WEC buoy.
The reference velocity levels were 0.1 and 0.04 m/s, which were also used in the previously described simulation.
To construct the reference velocity model, a local 1-D structure of the area was determined using VELEST software (Kissling et al. 1994) (Figure 2b).
The sheet is stretched with velocity (U_{w}= U_{0}(x+b)^{m}), where (U_{0}) is the reference velocity.
We verify the range of sensitivities α using different reference velocity structures reproduced by decreasing and increasing the reference velocities above 2.5 km depth by up to 20%, as shown by the red and blue 1D velocity profiles in Fig. 6, respectively.
The torques to track the reference velocities are generated using an adaptive proportional-integral-derivative control scheme, which is robust to unknown torque disturbances, combined with a computed torque based feedback linearization unit and a high gain observer to estimate the wheel velocities.
Assuming that each later phase in the receiver functions represents the wave converted from P to S at depth, the time-domain receiver function was transformed into a depth domain along each ray path using a reference velocity model.
Assuming that each later phase in a receiver function was a wave converted from P to S at depth, the time-domain receiver function was transformed into depth domain along each ray path using a reference velocity model.
As in Nakajima et al. (2005), we assumed that the host rock was peridotite; for the reference velocities, defined as the velocities of the dry host rock, we used V P 0 = 7.90 and V S 0 = 4.55 km/s.
