Inverted decoupling and LMI-based controller design for a turboprop engine with actuator dynamics

The main objective of the turboprop engine control system is to ensure propeller absorbed power at a constant propeller speed by controlling fuel flow and blade angle. Since each input variable affects the selected output variables, there exist strong interactions between different control loops of a Two-Spool Turbo Prop Engine(TSTPE). Inverted decoupling is used to decouple the interactions and decompose the TSTPE into two independent single-input single-output systems. The multi-variable PI controller and two single-variable PI controllers are designed for the TSTPE with actuator dynamics based on Linear Matrix Inequality(LMI), respectively, which is derived from static output feedback and pole placement condition. The step responses show that due to the difference in the response times of the selected output variables, it is difficult to design an appropriate multi-variable PI controller. The designed single-variable PI controllers are tested on the TSTPE integrated model to illustrate the effectiveness of the proposed method, that is,the interactions are first decoupled and then the controllers are designed, and the resulting simulated responses show that compared with the controller designed without actuator dynamics, the gas-generator shaft speed and power turbine shaft speed can better track their respective commands under the action of the controller designed with actuator dynamics.

DYNAMIC FREE ENERGY HYSTERESIS MODEL IN MAGNETOSTRICTIVE ACTUATORS

A dynamic free energy hysteresis model in magnetostrictive actuators is presented. It is the free energy hysteresis model coupled to an ordinary different equation in an unusual way. According to its special structure, numerical implementation method of the dynamic model is provided. The resistor parameter in the dynamic model changes according to different frequency ranges. This makes numerical implementation results reasonable in the discussed operating frequency range. The validity of the dynamic free energy model is illustrated by comparison with experimental data.

Real-time hybrid simulation for structural control performance assessment

Real-time hybrid simulation is an attractive method to evaluate the response of structures under earthquake loads. The method is a variation of the pseudodynamic testing technique in which the experiment is executed in real time, thus allowing investigation of structural systems with rate-dependent components. Real-time hybrid simulation is challenging because it requires performance of all calculations, application of displacements, and acquisition of measured forces, within a very small increment of time. Furthermore, unless appropriate compensation for actuator dynamics is implemented, stability problems are likely to occur during the experiment. This paper presents an approach for real-time hybrid simulation in which compensation for actuator dynamics is implemented using a model-based feedforward compensator. The method is used to evaluate the response of a semi-active control of a structure employing an MR damper. Experimental results show good agreement with the predicted responses, demonstrating the effectiveness of the method for structural control performance assessment.

Control of discrete-time nonlinear systems actuated through counter-convecting transport dynamics

We consider the stabilisation of discrete-time nonlinear systems that are actuated through a pair of transport partial difference equation(PdE)systems that convect in the opposite directions from one another.An explicit feedback law that compensates the discrete PdE dynamics is designed.Global asymptotic stability of the closedloop system is proved with the aid of a Lyapunov function.The feedback design is illustrated through an example.The proposed design in this paper allows the delay to be arbitrarily long and time-varying.Furthermore,our predictor feedback law in discrete time is explicit as the predictor state is computed by an algebraic equation.

Transition characteristics for a small tail-sitter unmanned aerial vehicle

Research on the transition phase of tail-sitter Unmanned Aerial Vehicles(UAVs)is crucial for trajectory planning and performance analysis.This study focuses on the analysis of the transition characteristics and path of a small dual-rotor tail-sitter UAV,including static and dynamic computations.The system input time delay and actuator dynamics are specifically considered during the dynamic analysis,and these actual physical properties ensure that the computation results are reliable and reasonable.The UAV steady-state limit is obtained through static analysis,which is also adopted to verify the correctness of the dynamic results.In regard to the dynamic analysis,several typical transition approaches are computed based on different initial states and optimization objective functions,and the different computations are applicable under specific task conditions.The off-line dynamic results of the transition path and actuator output sequence could also be adopted as reference values for the transition process during real flight.A comparison of the static and dynamic results illustrates the necessity of combining these two methods for UAV transition characteristic analysis.Furthermore,the UAV conceptual parameters related to the transition path are also studied,and the obtained quantitative characteristics provide feedback for the UAV conceptual design.

Proportional-integral-derivative control of nonlinear half-car electro-hydraulic suspension systems

This paper presents the development of a proportional-integral-derivative (PID)-based control method for application to active vehicle suspension systems (AVSS). This method uses an inner PID hydraulic actuator force control loop, in combination with an outer PID suspension travel control loop, to control a nonlinear half-car AVSS. Robustness to model uncertainty in the form of variation in suspension damping is tested, comparing performance of the AVSS with a passive vehicle suspension system (PVSS), with similar model parameters. Spectral analysis of suspension system model output data, obtained by performing a road input disturbance frequency sweep, provides frequency response plots for both nonlinear vehicle suspension systems and time domain vehicle responses to a sinusoidal road input disturbance on a smooth road. The results show the greater robustness of the AVSS over the PVSS to parametric uncertainty in the frequency and time domains.

Voltage control strategy for an uncertain mobile robot

Purpose–The uncertainty and nonlinearity are the challenging problems for the control of a nonholonomic wheeled mobile robot.To overcome these problems,many valuable methods have been proposed by using two control loops namely the kinematic control and the torque control so far.In majority of the proposed approaches the dynamics of actuators is omitted for simplicity in the control design.This drawback degrades the control performance in high-velocity tracking control.On the other hand,to guarantee stability and overcome uncertainties,the control methods become computationally extensive and may be impractical due to using all states.The purpose of this paper is to design a simple controller with guaranteed stability for overcoming the nonlinearity,uncertainty and actuator dynamics.Design/methodology/approach–The control design includes two control loops,the kinematic control loop and the novel dynamic control loop.The dynamic control loop uses the voltage control strategy instead of the torque control strategy.Feedbacks of the robot orientation,robot position,robot linear and angular velocity,and motor currents are given to the control system.Findings–To improve the precision,the dynamics of motors are taken into account.The most important advantages of the proposed control law is that it is free from the robot dynamics,thereby the controller is simple,fast response and robust with ignorable tracking error.The control approach is verified by stability analysis.Simulation results show the effectiveness of the proposed control applied on an uncertain nonholonomic wheeled mobile robot driven by permanent magnet dc motors.A comparison with an adaptive sliding-mode dynamic control approach confirms the superiority of the proposed approach in terms of precision,simplicity of design and computations.Originality/value–The originality of the paper is to present a new control design for an uncertain nonholonomic wheeled mobile robot by using voltage control strategy in replace of the torque control strategy.In addition,a novel state-space model of electrically driven nonholonomic wheeled mobile robot in the workspace is presented.

A Robust Tracking Controller for Electrically Driven Robot Manipulators: Stability Analysis and Experiment

In this paper, a robust controller for electrically driven robotic systems is developed. The controller is designed in a backstepping manner. The main features of the controller are: 1) Control strategy is developed at the voltage level and can deal with both mechanical and electrical uncertainties. 2) The proposed control law removes the restriction of previous robust methods on the upper bound of system uncertainties. 3) It also benefits from global asymptotic stability in the Lyapunov sense. It is worth to mention that the proposed controller can be utilized for constrained and nonconstrained robotic systems. The effectiveness of the proposed controller is verified by simulations for a two link robot manipulator and a four-bar linkage. In addition to simulation results,experimental results on a two link serial manipulator are included to demonstrate the performance of the proposed controller in tracking a given trajectory.