Positioning control of DC servomotor-based antenna using PID tuned compensator

Abstract

Direct current (DC) servomotor-based parabolic antenna is automatically positioned using control technique to track satellite by maintaining the desired line of sight for quality transmission and reception of electromagnetic wave signals in telecommunication and broadcast applications. With several techniques proposed in the literature for parabolic antenna position control, there is still a need to improve the tracking error and robustness of the control system in the presence of disturbance. This paper has presented positioning control of DC servomotor-based antenna using proportional-integral-derivative (PID) tuned compensator (TC). The compensator was designed using the control and estimation tool manager (CETM) of MATLAB based on the PID tuning design method using robust response time tuning technique with interactive (adjustable performance and robustness) design mode at a bandwidth of 40.3 rad/s. The compensator was added to the position control loop of the DC servomotor–based satellite antenna system. Simulations were carried out in a MATLAB environment for four separate cases by applying unit forced input to examine the various step responses. In the first and second cases, simulations were conducted without the compensator (PID TC) in the control loop assuming zero input disturbance and unit input disturbance. The results obtained in terms of time-domain response parameters showed that with the introduction of unit disturbance, the rise time improved by 36 % (0.525–0.336 s) while the peak time, peak percentage overshoot, and settling time deteriorate by 16.3 % (1.29–1.50 s), 43.5 % (34.7–49.8 %), and 7.6 % (4.35–4.68 s), respectively. With the introduction of the PIDTC for the third case, there was an improvement in the system’s overall transient response performance parameters. Thus to provide further information on the improved performance offered by the compensator, the analysis was done in percentage improvement. Considering the compensated system assuming zero disturbance, the time-domain response performance parameters of the system improved by 94.1, 94.7, 73.1, and 97.1 % in terms of rising time (525–30.8 ms), peak time (1,290–67.9 ms), peak percentage overshoot (34.7–9.35 %), and settling time (4.35–0.124 s), respectively. In the fourth case, the compensator’s ability to provide robust performance in the presence of disturbance was examined by comparing the step response performance parameters of the uncompensated system with unit input disturbance to the step response performance parameters of the compensated system tagged: with PID TC + unit disturbance. The result shows that PID TC provided improved time-domain transient response performance of the disturbance handling of the system by 91.0, 95.4, 80.0, and 93.1 % in terms of rising time (336–30.5 ms), peak time (1500–69.1 ms), peak percentage overshoot (34.7–10.0), and settling time (4.68–0.325 s), respectively. The designed compensator provided improved robust and tracking performance while meeting the specified time-domain performance parameters in the presence of disturbance.