A new active disturbance rejection control-based (ADRC) scheme is proposed in this work to address the problem of tracking/rejecting periodic signals of unknown and varying frequencies. The frequencies are obtained on-line with a dedicated adaptive estimator and used in real-time as partial model information to an observer that reconstructs (among other things) the negative influence of periodic terms on the controlled output. A continuously updated two-tier control action is then applied to compensate the periodic interference and govern the resultant (simplified) plant dynamics. The proposed control topology is derived here in its general form and validated with an experimental case study.

Purpose A laser seeker is an important element in missile guidance and control systems, responsible for target detection and tracking. Its control is, however, a challenging problem due to complex dynamics and various acting disturbances. Hence, the purpose of this study is to propose a systematic design, tuning, analysis and performance verification of a nonlinear active disturbance rejection control (ADRC) algorithm for the specific case of the laser seeker system. Design/methodology/approach The proposed systematic approach of nonlinear ADRC application to the laser seeker system consists of the following steps. The complex laser seeker control problem is first expressed as a regulation problem. Then, a nonlinear extended state observer (ESO) with varying gains is used to improve the performance of a conventionally used linear ESO (LESO), which enables better control quality in both transient and steady-state periods. In the next step, a systematic observer tuning, based on a detailed analysis of the system disturbances, is proposed. The stability of the overall control system is then verified using a describing function method. Next, the implementation of the NESO-based ADRC solution is realized in a fixed-point format using MATLAB/Simulink and Xilinx System Generator. Finally, the considered laser seeker control system is implemented in discrete form and comprehensively tested through hardware-in-the-loop (HIL) co-simulation. Findings Through the conducted comparative study of LESO-based and NESO-based ADRC algorithms for the laser seeker system, the advantages of the proposed nonlinear scheme are shown. It is concluded that the NESO-based ADRC scheme for the laser seeker system (with appropriate parameters tuning methodology) provides better control performance in both transient and steady-state periods. The conducted multicriteria study validates the efficacy of the proposed systematic approach of applying nonlinear ADRC to laser seeker systems. Practical implications In practice, the obtained results imply that the laser seeker system, governed by the studied nonlinear version of the ADRC algorithm, could potentially detect and track targets faster and more accurately than the system based on the common linear ADRC algorithm. In addition, the article presents the step-by-step procedure for the design, field programmable gate array (FPGA) implementation and HIL-based co-simulation of the proposed nonlinear controller, which can be used by control practitioners as one of the last validation stages before experimental tests on a real guidance system. Originality/value The main contribution of this work is the systematic procedure of applying the ADRC scheme with NESO for the specific case of the laser seeker system. It includes its design, tuning, analysis and performance verification (with simulation and FPGA hardware). The novelty of the work is also the combination and practical realization of known theoretical elements (NESO structure, NESO parameter tuning, ADRC closed-loop stability analysis) in the specific case of the laser seeker system. The results of the conducted applied research increase the current state of the art related to robust control of laser seeker systems working in disturbed and uncertain conditions.

Introduction/purpose: Technological progress has led to the actualization of the problem of construction and use of high-energy microwave weapons, especially electromagnetic bombs. However, in the recent military-professional literature, this issue is little represented. Methods: The available existing literature on the subject was analyzed. Results: It has been established that the general principles of functioning and theoretical bases have been widely available and known for many years. Numerous experiments in specialized institutions have confirmed the electromagnetic pulse effectiveness. This is especially true of sensitivity of devices based on semiconductor technology. Also, it is assumed that, at the current technological level, technical solutions are widely available to a large number of entities. The most common model of electromagnetic bomb dealt with in the literature is the realization of the use of a compression flux generator and an oscillator with a virtual cathode. According to the authors, this variant would ensure that the final product has realistic physical dimensions and sufficient strength to be useful. Another problem identified in the literature is the massive absence of adequate protection measures against the effects of electromagnetic pulses. This applies not only to the civilian but also to the military sector and imposes the need to invest significant resources in order to subsequently increase resilience. Conclusion: The available literature indicates that it is possible to make an electromagnetic bomb of acceptable physical dimensions and power. It is assumed that it would generate an electromagnetic pulse with a power of about 10 GW and a frequency of 5 GHz. In combination with high-precision weapons, even protected devices would be successfully disabled. The wide presence of semiconductor technology in all spheres of life makes this weapon extremely effective and it is realistic to expect its much wider application in the coming period.

In this paper, the laser seeker control problem is solved in the framework of active disturbance rejection control (ADRC). The considered problem, which consists of laser seeker stabilisation and target tracking, is expressed here as a regulation problem. A nonlinear extended state observer (NESO) with varying gains is used to improve the performance of linear ESO (LESO), and thus enable better control performance in both transient period and steady-state, with lower control effort. Based on a detailed analysis of system disturbances, a special ADRC tuning method is proposed. The stability of the overall control structure is analysed with a description function method. Through comparative simulations LESO-based and the introduced NESO-based ADRC for the laser seeker system, the advantages of the proposed scheme are shown.