2.4.2. Setpoint Values

Because of the position of the sun in the sky changes by 1 degree every 4 min, it is not necessary to modify the orientation of the heliostat every second of the day. Therefore, the values of the reference angles are discretized every minute, as shown in Figure 16 for the parameters of Table 4.

To reduce the error due to the resolution of the rotary encoders, the discrete reference value is converted from radians to encoder steps and is rounded to the closest integer value to obtain a final reference value that corresponds to a value in the encoder steps. Therefore, when the heliostat angles reach the desired position, the error signal will be zero. The values of the error between the final and desired reference of the heliostat axes are shown in Figure 17.

**Figure 16.** Setpoint values of the orientation control for the azimuth axis (**a**), the elevation axis (**b**) and both axes (**c**).

**Figure 17.** Final reference error values of the orientation control for the azimuth axis (**a**), the elevation axis (**b**) and both axes (**c**).
