Influence Of Actuator Dynamics Research Articles

A unified switching dynamic modeling of multi-mode underwater vehicle

Hybrid underwater vehicles have increasingly been deployed in ocean observation and monitoring. This study presents a novel multi-mode underwater vehicle (MUV) motivated by integrating maneuvering efficiency, endurance, and vertical continuous observation capacity. It can switch freely among three operation modes, including vertical diving and floating mode (VDF mode) like the Argo profiling float (APF), steady gliding mode (SG mode) similar to the underwater glider (UG), and propeller-rudder propulsion mode (PRP mode) such as the autonomous underwater vehicle (AUV). The generalized theory of mode switching through extreme pitch angle adjustment is emphasized, mainly to achieve smooth switching between VDF mode and SG mode (or PRP mode) with the critical design principles of the attitude and buoyancy subsystems. Mathematical models describing the motion of three operation modes are developed, particularly considering the actuators’ dynamic characteristics. Simulations are performed to verify the mobility performance of the vehicle, especially considering the influence of actuator dynamics on mode switching. Real-time prototype experiments demonstrate the desired performance of various modes and, in particular, confirm the necessity of the mentioned design criteria for mode switching.

Fuzzy Constrained Predictive Optimal Control of High Speed Train with Actuator Dynamics

We investigate the problem of fuzzy constrained predictive optimal control of high speed train considering the effect of actuator dynamics. The dynamics feature of the high speed train is modeled as a cascade of cars connected by flexible couplers, and the formulation is mathematically transformed into a Takagi-Sugeno (T-S) fuzzy model. The goal of this study is to design a state feedback control law at each decision step to enhance safety, comfort, and energy efficiency of high speed train subject to safety constraints on the control input. Based on Lyapunov stability theory, the problem of optimizing an upper bound on the cruise control cost function subject to input constraints is reduced to a convex optimization problem involving linear matrix inequalities (LMIs). Furthermore, we analyze the influences of second-order actuator dynamics on the fuzzy constrained predictive controller, which shows risk of potentially deteriorating the overall system. Employing backstepping method, an actuator compensator is proposed to accommodate for the influence of the actuator dynamics. The experimental results show that with the proposed approach high speed train can track the desired speed, the relative coupler displacement between the neighbouring cars is stable at the equilibrium state, and the influence of actuator dynamics is reduced, which demonstrate the validity and effectiveness of the proposed approaches.

Effects of actuator nonlinearity on aeroelastic characteristics of a control fin

The influences of actuator nonlinearities on actuator dynamics and the aeroelastic characteristics of a control fin were investigated by using iterative V-g methods in subsonic flows; in addition, the doublet-hybrid method (DHM) was used to calculate unsteady aerodynamic forces. The changes of actuator dynamics induced by nonlinearities, such as backlash or freeplay, and the variations of flutter boundaries due to the changes of actuator dynamics were observed. Results show that the aeroelastic characteristics can be significantly dependent on actuator dynamics. Thus, the actuator nonlinearities may play an important role in the nonlinear aeroelastic characteristics of an aeroelastic system. The present results also indicate that it is necessary to seriously consider the influence of actuator dynamics on the flutter characteristics at the design stage of actuators to prevent aeroelastic instabilities of aircraft or missiles.

Displacement Feedback Control of Proof-Mass Actuators for Vibration Suppression.

The use of direct displacement feedback control for vibration suppression of flexible structures by multiple proof-mass actuators is investigated. Closed-loop eigenvalue analysis is carried out considering the influence of actuator dynamics, and closed-loop stability is proved which indicates the stability robustness of the control algorithm. Regarding the performance of the control system, parameters of the actuator are optimized analytically using an eigenvalue criterion for one-degree-of-freedom structure and the optimum parameters are expressed in closed form as a function of feedback gain. In addition, the results of optimum parameters are generalized to adapt to control of multiple-degree-of-freedom structure. A control example of a plane frame structure is given with the actuators used either passively or actively. Simulation results demonstrated the effectiveness of the proposed control procedures.