and the configuration of the modified disturbance compensation is shown in Figure 3(b).
4. Experiment of continuous-time RAC
In this section, some experiments of the RAC method are done for the vertical type 2-link underwater robot shown in Figure 1.
Figure 4 shows the configuration of the experimental system. A robot has a 2-DOF manipulator with joints that are actively rotated by velocity and torque control type servo actuators consisting of servo motors and incremental type encoders. The physical parameters of the underwater robot are shown in Table 1. Moreover, four 40[W] thrusters are attached to the vertical and horizontal directions on the robot base to provide propulsion for controlling the position and attitude angle of the base. The forward and reverse propulsion generated by the thruster are calculated by
1.341 v2 - 1.363v - 0.026 (1.2 < v < 4) - 0.763v2 - 0.835v + 0.019 (-4 < v < -1.2)
where v is the input voltage to the power amplifier of the thruster. Note that Equation (31) were obtained from the experiments (Yamada & Sagara, 2002).
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