Objective  The optoelectronic stabilization platform is an important component of airborne optoelectronic systems, which plays a role in target tracking and imaging, isolating external disturbances of the carrier, and improving imaging quality. The optoelectronic stabilization platform is an important combat equipment for flight carriers such as helicopters, reconnaissance aircraft, and unmanned aerial vehicles. It plays an important role in the entire combat chain tasks such as search, detection, locking, tracking, strike, and evaluation. With the continuous improvement of battlefield demand, the accuracy requirements of optoelectronic stabilization platforms have gradually increased from tens of microradians to within ten microradians. The optimization of optoelectronic stabilization platform control algorithms is the most direct and cost-effective method to improve its stability accuracy. The current control algorithm for optoelectronic stabilization platforms mainly relies on PID algorithm, and in algorithm design and control, model free or ideal zero free models are used. However, in actual systems, there are often zero points, and the dynamic zero points that are not considered seriously limit the further improvement of system stability accuracy. Therefore, this paper proposes a disturbance rejection control design method for optoelectronic stabilization platforms that considers the zero point of the transfer function.

  Methods  This paper proposes a disturbance rejection control design method for optoelectronic stabilization platforms that considers the zero point of the transfer function. In the analysis of the system model, the flexible transmission between the motor and the load was taken into account (Fig.2), and the model of the photoelectric stable platform with zero point was derived (Eq.2). By perturbing the platform model with zeros (Eq.12), the system with zeros is transformed into a system with disturbances but without zeros (Eq.18). Furthermore, through disturbance estimation and compensation, the system model is ultimately transformed into a standard model (Eq.25). Finally, the system controller was designed using zero pole cancellation method to achieve high-performance closed-loop control of the optoelectronic stable platform.

  Results and Discussions  The disturbance rejection control of the optoelectronic stable platform considering the transmission zero point can achieve high-performance command response and disturbance suppression through disturbance design, disturbance estimation, and disturbance compensation, while considering the dynamic conditions of the system zero point. A simulation verification experiment was designed for this algorithm (Fig.5), and the corresponding performance of the system's instructions was evaluated by adjusting indicators such as setting time, rise time, and overshoot (Fig.6). The results showed that the proposed algorithm reduced the setting time by 37.2% and overshoot by 62.35% compared to the traditional PID algorithm. Compared with MLADRC, the overshoot increased by 80.72% and the setting time increased by 61.97% while ensuring the same rise time (Tab.1). The disturbance suppression ability of the system was verified through the method of equivalent disturbance injection, which is superior to traditional methods such as PID and MLADRC (Fig.7). Finally, through physical experiments, it was verified that the disturbance suppression capability within 5 Hz was improved by more than 80% compared to traditional PID controllers, and the disturbance capability was improved by 27.41% compared to MLADRC (Tab.3). This algorithm has excellent disturbance suppression ability.

  Conclusions  A disturbance rejection control algorithm for optoelectronic stabilization platform considering transfer function zeros has been designed. This algorithm has the characteristics of considering the dynamics of model zeros, excellent instruction response, and strong disturbance suppression ability. It can convert system models containing zeros into zero free systems for controller design. Simulation and physical verification experiments show that the algorithm has significantly improved performance in step command response and disturbance suppression within 5 Hz compared to traditional PID control algorithm, linear active disturbance rejector control design algorithm, and model assisted linear active disturbance rejector control design algorithm, which can effectively enhance the performance of the optoelectronic stability platform system.