In this paper, a nonsingular, essentially continuous and finite-time convergent impact angle constrained guidance law for intercepting stationary, constant speed, and maneuvering targets is developed using advanced terminal sliding mode control schemes and extended state observer. In order to achieve the specified intercept angle in finite time without singularity, the nonsingular fast terminal sliding mode control algorithm is employed to construct sliding surface. The fast terminal sliding mode control technique is used to establish the reaching law, so the system trajectory converges quickly from initial state to the switching surface in the whole reaching phase and the proposed guidance law is essentially continuous. Noticing the interception of a maneuvering target, the unknown target acceleration is estimated and compensated using extended state observer. Due to its inherent attribute of singularity-free, continuity, and faster convergence rate, no approximation is necessary in the implementation of the proposed guidance law, so better tracking accuracy of the desired intercept angle in a shorter time with a smoother guidance command can be guaranteed compared with conventional terminal sliding mode guidance law. A large number of numerical simulations are implemented to justify the effectiveness of the proposed guidance law.
An inertial actuator that improves load capacity within a miniaturized structure has drawn wide attention. This work proposes an inertial piezoelectric linear actuator and investigates a method that improves its load capacity. The structure and operational principle of the actuator are introduced. A dynamic model of the system is established that simulates the stepping characteristics. The dominant parameters affecting load capacity are discussed in detail. A prototype was manufactured and its main performance features tested. The experimental results confirm that the proposed actuator achieves a load capacity of 3.65 N, a resolution of 0.47 μm, and a speed of 6.15 mm s −1 , despite its compact size of Φ 9 mm×27 mm. The actuator has an improved load capacity given its smaller configuration than those reported in the literature. The model established provides a theoretical guide to the design of similar inertial actuators and may be used to predict and evaluate their load capacity.
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