Semi-physical Simulation Platform Research Articles

Security Analysis for CBTC Systems under Attack–Defense Confrontation

Communication-based train controls (CBTC) systems play a major role in urban rail transportation. As CBTC systems are no longer isolated from the outside world but use other networks to increase efficiency and improve productivity, they are exposed to huge cyber threats. This paper proposes a generalized stochastic Petri net (GSPN) model to capture dynamic interaction between the attacker and the defender to evaluate the security of CBTC systems. Depending on the characteristics of the system and attack–defense methods, we divided our model into two phases: penetration and disruption. In each phase, we provided effective means of attack and corresponding defensive measures, and the system state was determined correspondingly. Additionally, a semiphysical simulation platform and game model were proposed to assist the GSPN model parameterization. With the steady-state probability of the system output from the model, we propose several indicators for assessing system security. Finally, we compared the security of the system with single defensive measures and multiple defensive measures. Our evaluations indicated the significance of the defensive measures and the seriousness of the system security situation.

Design and Experiment of a Semiphysical Simulation Platform of the Lifting System of a Tractor with an Adaptive Function

Design and Experiment of a Semiphysical Simulation Platform of the Lifting System of a Tractor with an Adaptive Function

Automatic flight control design considering objective and subjective risks during carrier landing

In this article, a design scheme of automatic carrier landing system control law based on combination of the objective risk and the subjective risk is proposed, in order to improve the safety and flying quality of the landing. The nonlinear longitudinal mathematical model is constructed in the air wake turbulence condition during carrier landing, which is transformed into a linear perturbed model by the state-space equations with deviation state variables. The concepts of the objective risk and the subjective risk in the recovery of an aircraft aboard a carrier are addressed. A principle of predicting the future states based on the current ones is put forward so that a mathematic model for the objective risk is established, synthetically considering the current and future landing state deviations. For the other risk, the corresponding model is obtained by the subjective experiences of the pilots in the flight simulation tests. Furthermore, a novel model predictive control algorithm, which contains the additional subjective risk and the time-varying weights of the state terms, is proposed. Automatic carrier landing control law is built by introducing the objective risk, the subjective risk, and the effect of carrier air wake disturbance. In the rolling optimization progress, these time-varying weights are dynamically tuned according to the constantly changing objective risk to control the state deviations and suppress this risk, while the subjective risk is handled by the additional risk terms. Besides, the action of carrier air wake disturbance is considered and compensated in the derivation of the linear matrix inequalities. Test results based on a semi-physical simulation platform indicate that the new automatic carrier landing system control algorithm proposed by this article brings about an excellent carrier landing performance as well as an improved flying quality.

Method of Emergency Collision Avoidance for Unmanned Surface Vehicle (USV) Based on Motion Ability Database

Abstract The unmanned surface vehicles (USV) are required to perform a dynamic obstacle avoidance during fulfilling a task. This is essential for USV safety in case of an emergency and such action has been proved to be difficult. However, little research has been done in this area. This study proposes an emergency collision avoidance algorithm for unmanned surface vehicles (USVs) based on a motion ability database. The algorithm is aimed to address the inconsistency of the existing algorithm. It is proposed to avoid collision in emergency situations by sharp turning and treating the collision avoidance process as a part of the turning movement of USV. In addition, the rolling safety and effect of speed reduction during the collision avoidance process are considered. First, a USV motion ability database is established by numerical simulation. The database includes maximum rolling angle, velocity vector, position scalar, and steering time data during the turning process. In emergency collision avoidance planning, the expected steering angle is obtained based on the International Regulations for Preventing Collisions at Sea (COLREGs), and the solution space, with initial velocity and rudder angle taken as independent variables, is determined by combining the steering time and rolling angle data. On the basis of this solution space, the objective function is solved by the particle swarm optimization (PSO) algorithm, and the optimal initial velocity and rudder angle are obtained. The position data corresponding to this solution is the emergency collision avoidance trajectory. Then, the collision avoidance parameters were calculated based on the afore mentioned model of motion. With the use of MATLAB and Unity software, a semi-physical simulation platform was established to perform the avoidance simulation experiment under emergency situation. Results show the validity of the algorithm. Hence results of this research can be useful for performing intelligent collision avoidance operations of USV and other autonomous ships

Collision avoidance planning for unmanned surface vehicle based on eccentric expansion

The International Regulations for Preventing Collisions at Sea (COLREGS) specify certain navigation rules for ships at risk for collision. Theoretically, the safety of unmanned surface vehicles and traffic boats would be guaranteed when they comply with the COLREGS. However, if traffic boats do not comply with the demands of the convention, thereby increasing the danger level, then adhering to the COLREGS may be dangerous for the unmanned surface vehicle. In this article, a dynamic obstacle avoidance algorithm for unmanned surface vehicles based on eccentric expansion was developed. This algorithm is used to solve the possible failure of collision avoidance when the unmanned surface vehicle invariably obeys the COLREGS during the avoidance process. An obstacle avoidance model based on the velocity obstacle method was established. Thereafter, an eccentric expansion operation on traffic boats was proposed to ensure a reasonable balance between safety and the rules of COLREGS. The expansion parameters were set according to the rules of COLREGS and the risk level of collision. Then, the collision avoidance parameters were calculated based on the aforementioned motion model. With the use of MATLAB and Unity software, a semi-physical simulation platform was established to perform the avoidance simulation experiment under different situations. Results show the validity, reliability and intellectuality of the algorithm. This research can be used for intelligent collision avoidance of unmanned surface vehicle and other automatic driving ships.

Attitude Measurement for High-Spinning Projectile with a Hollow MEMS IMU Consisting of Multiple Accelerometers and Gyros.

A low cost, high precision hollow structure MEMS IMU has been developed to measure the roll angular rate of a high-spinning projectile. The hollow MEMS IMU is realized by designing the scheme of non-centroid configuration of multiple accelerometers. Two dual-axis accelerometers are respectively mounted on the pitch axis and the yaw axis away from the center of mass of the high-spinning projectile. Three single-axis gyros are mounted orthogonal to each other to measure the angular rates, respectively. The roll gyro is not only used to judge the spinning direction, but also to measure and compensate for the low rotation speed of the high-spinning projectile. In order to improve the measurement accuracy of the sensor, the sensor output error is modeled and calibrated by the least square method. By analyzing the influence of noise statistical characteristics on angular rate solution accuracy, an adaptive unscented Kalman filter (AUKF) algorithm is proposed, which has a higher estimation accuracy than UKF algorithm. The feasibility of the method is verified by numerical simulation. By using the MEMS IMU device to build a semi-physical simulation platform, the solution accuracy of the angular rate is analyzed by simulating different rotation speeds of the projectile. Finally, the flight test is carried out on the rocket projectile with the hollow MEMS IMU. The test results show that the hollow MEMS IMU is reasonable and feasible, and it can calculate the roll angular rate in real time. Therefore, the hollow MEMS IMU designed in this paper has certain engineering application value for high-spinning projectiles.

Modeling and Speed Control of the Underwater Wheeled Vehicle Flexible Towing System

In this paper, the research contents are mainly focused on the technology of the underwater wheeled vehicle speed control. For providing a passive towed underwater wheeled vehicle with accelerating, uniform motion and decelerating capability which can simulate an underwater navigation environment for the carried unit, we devised a novel open-type hydraulic flexible towing system. Combining the hydrodynamic model of the vehicle and the hydraulic mechanism model, the dynamic characteristics of the novel towing system are studied by computing simulation. Aiming at the force coupling character of double driving hydraulic winches, a master-slave synchronization control strategy is proposed. Then, in view of the flexible towing system features, i.e., strong coupling, nonlinear, time-varying load, and environmental constraints, a real speed controller based on fast terminal sliding mode control theory is designed and manufactured. To verify the effectiveness of the controller, a hardware-in-the-loop simulation test is carried out on the strength of a semiphysical simulation platform based on Matlab/Simulink and VxWorks real-time system. The experiment results show that the speed controller based on fast terminal sliding mode control has excellent effect on rapidity, stability, and anti-interference characteristics.

Design of Automatic Carrier-Landing Controller Based on Compensating States and Dynamic Inversion

In this paper, a design scheme of automatic carrier landing system (ACLS) control law based on compensating states and dynamic inversion is proposed, in order to eliminate landing risk and air wake disturbance and improve flight quality during landing. First of all, the mathematical model for an aircraft during carrier landing is established and transformed into a low-order linear perturbed model with the involved state variables, which denotes the reference model. Second, a high-dimension field of the landing risk is addressed, which reflects the current and the potential risk degrees due to the subjective prediction of the pilots. The coefficients of the landing risk field are established based on a pilot behavioral model. Third, a concept of compensating states is proposed by this paper. On one hand, the compensating states of the air wake disturbance are estimated from the nonlinear and reference models. On the other hand, the compensating states of the landing risk are composed of the high-dimension risk field. Fourth, automatic carrier landing control law is built with the compensating states of air wake and landing risk, nonlinear dynamic inversion, and feedback signals of the flight states. In the rolling optimization progress, the landing risk, air wake, and nonlinear factors of flight states are dynamically introduced to control the state deviations and suppress landing risk. Test results based on a semi-physical simulation platform indicate that the proposed algorithm brings about an excellent landing performance and an ability to eliminate landing risk and air wake.

Research on the key problems of MPPT strategy based on active power control of hydraulic wind turbines

The constant displacement pump-variable motor hydrostatic transmission system is used as the main drive system in hydraulic wind turbines, and unlike traditional wind turbines using asynchronous generators and electronic converter devices, the synchronous generator is directly adopted for grid-connected generation. In this paper, the maximum power point tracking (MPPT) problem of hydraulic wind turbines is studied in depth. The energy transfer process of hydraulic wind turbines is introduced, and the key issues to be solved in MPPT are presented. A MPPT strategy based on active power control is proposed. The power transmission characteristics of hydraulic wind turbines and the nonlinear problems existing in active power control are analyzed. A small signal linearization method combined with variable gain proportional integral differentiation (PID) is used to solve the power response inconsistent problems that come from system nonlinearity. The MPPT strategy based on active power control is optimized by a speed control loop to insure the system stability in the process of MPPT. Finally, the power response consistency and the MPPT strategy are verified in the 30 kVA semi physical simulation platform.

A Generalized Predictive Control-Based Path Following Method for Parafoil Systems in Wind Environments

Parafoil systems represent flexible wing vehicles. In case a vehicle is flying at low altitude, it is well known that the vehicle is more susceptible to winds. Also, due to the nonlinear, large inertial existing within the system, traditional control methods, such as traditional proportional-integral-derivative (PID), cannot guarantee the quality of path following. Therefore, we here apply generalized predictive control (GPC)-based method for parafoil systems to follow the designed path for a better control effect. To achieve this, we first propose a novel modeling method based on computational fluid dynamics to build a dynamic model of the parafoil system in windy environments. Afterward, a guidance law is designed according to a hybrid approach that combines the cross track error and the line of sight. In addition, the path following controller is established by using GPC. Finally, we generate and interpret numerical results to demonstrate the feasibility of the horizontal path following method in windy environments by utilizing the semi-physical simulation platform. The achieved results show that the GPC controller achieves high precision path following. More precisely, it possesses a better anti-wind ability and tracking accuracy and, therefore, the method outperforms PID controller.

Design and flight-stability analysis of a closed fixed-wing unmanned aerial vehicle formation controller

This article addresses a flight-stability problem for the multiple unmanned aerial vehicles cooperative formation flight in the process of the closed and high-speed flight. The main objective is to design a cooperative formation controller with known external factors, and this controller can keep the consensus of attitude and position and reduce the communication delay between any two unmanned aerial vehicles and increase unmanned aerial vehicles formation cruise time under the known external factors. Known external factors are taken into consideration, and longitude maneuvers using nonlinear thrust vectors were employed with unsteady aerodynamic models, according to the attitude and position of unmanned aerial vehicles, which were employed as corresponding input signals for studying the dynamic characteristics of unmanned aerial vehicles formation flight. In addition, the relative distance between any two unmanned aerial vehicles was not allowed to exceed their safe distance so that the controller could perform collision avoidance. An analysis of formation flight distance error shows that it converged to a fixed value that well ensured unmanned aerial vehicles formation flight stability. The experimental results show that the controller can improve the speed of a closed formation effectively and maintain the stability of formation flight, which provides a method for closed formation flight controller design and collision avoidance for any two unmanned aerial vehicles. Meanwhile, the effectiveness of proposed controller is fully proved by semi-physical simulation platform.

Modeling and control of mine main fan switchover system

Mine main fan switchover system (MMFSS) is crucial for the mine safe production. MMFSS consists of two main fans (one working and one on standby), and each main fan is equipped with a vertical air door and a horizontal air door. The main purpose of MMFSS is to ensure the stability of the underground airflow quantity and achieve the satisfactory ventilation during the switchover. Moreover, the safe and economic operation of mine production should be ensured. In this paper, the modeling and control problem of MMFSS is considered. First, based on the theory of fluid flow network, the minimal model of MMFSS is built by combining the branch fluid dynamics with the concept of graph theory. Then, a decentralized controller that fully considers the pressure head regulation of two main fans is developed by the Lyapunov stability theory. The controller can ensure that the four air doors can meet with the technological requirements. Finally, the proposed results are conformed using simulations on a semi-physical simulation platform for MMFSS.

Fault Tolerant Predictive Control Based on Discrete-Time Sliding Mode Observer for Quadrotor UAV

An active fault-tolerant control scheme for a quadrotor unmanned aerial vehicle (UAV) with actuators faults is presented in this paper. The proposed scheme is based on model predictive control (MPC) and the discrete-time sliding mode observer. Considering the impact of disturbances on fault diagnosis, a discrete-time sliding mode observer with simple structure and strong robustness against the disturbances is designed to isolate the actuator faults and estimate the control effectiveness factors accurately. Using the fault diagnosis information, a model predictive active fault tolerant controller with embedded integrator is proposed to compensate parameter uncertainty and bounded disturbances in the realistic control system of the quadrotor. The advantages of the proposed control scheme are the ability of dealing with the control constraints, improving the fault-tolerant control precision and getting better real-time and anti-interference performance. The algorithm comparison experimental results on the quadrotor semi-physical simulation platform validate the feasibility and effectiveness of the proposed control scheme.

Design of multi-functional simulation platform based on mining speed-regulating magnetic coupling

This paper establishes a semi-physical simulation platform on the basis of massive data analysis and computation according to the characteristics of mining speed-regulating magnetic coupling. The platform can be used to simulate various environment changes in the actual on-load application of magnetic coupling, verify the control strategy for magnetic coupling, provide simulation basis and references for on-site usage, as well as establish a mathematical model for all components of driving system of the entire belt conveyor. Through the experiment analysis, it is proved that this platform can effectively and objectively simulate the speed control situation of coupling, as well as the multi-power balance effect of the belt conveyor during soft startup of belt conveyor, thus providing practical engineering applications with strong data support.

Design of Semi-Physical Simulation Platform for Hydraulic System of Working Device of Excavator

Design of Semi-Physical Simulation Platform for Hydraulic System of Working Device of Excavator

T–S Fuzzy Logic Based Modeling and Robust Control for Burning-Through Point in Sintering Process

Burning-through point (BTP) control is the key to guranteeing the sintering process and sinter quality. Due to an opening combustion and multiple input conditions, the combustion process of the sintering process shows a typical characteristic of time-varying operation conditions. This paper analyzes the influence factors resulting in time-varying operation conditions and then constructs an improved Takagi–Sugeno (T–S) fuzzy model of BTP based on the linear parameter varying (LPV-TS-BTP model), in which the BTP temperature and the central bellows temperature are taken as time-varying parameters. The model explains how the different working conditions change the systems dynamics and describes this time-varying nonlinear model in the form of a linear combination model. Then, a fuzzy robust control method based on the LPV-TS-BTP model is designed by using the parallel distributed compensation principle to realize the BTP control of complex process, in which the controller parameters are achieved by using the linear matrix inequality (LMI) method. The simulations about modeling and control, which are carried out on a semiphysical simulation platform for the sintering process, verify that the model has a high prediction accuracy, and the fuzzy robust control makes BTP stable around a given bellows.

Study on the sliding mode fault tolerant predictive control based on multi agent particle swarm optimization

For a class of uncertain discrete-time systems with time varying delay, the problem of robust fault-tolerant control for such systems is studied by combining the design of sliding mode control (SMC) and model predictive control (MPC). A sliding mode fault tolerant predictive control based on multi agent particle swarm optimization (PSO) is presented, and the design, analysis and proof of the scheme are given in detail. Firstly, the sliding mode prediction model of the system is designed by assigning poles of the output error of the system. The model has time varying characteristics, and it can improve the motion quality of the system while ensuring the sliding mode is stable. Secondly, a new discrete reference trajectory considering time-delay systems subjected simultaneously to parameter perturbations and disturbances is proposed, which not only can ensure that the state of the system has good robustness and fast convergence in the process of approaching sliding mode surface, but also can inhibit chattering phenomenon. Thirdly, the multi agent PSO improves the receding-horizon optimization, which can quickly and accurately solve the control laws satisfying the input constraints, and can effectively avoid falling into local extrema problem of the traditional PSO. Finally, the theoretical proof of robust stability of the proposed control scheme is given. Experimental results of quad-rotor helicopter semi physical simulation platform show that the state of uncertain discrete-time systems with time varying delay is stable under the action of the proposed control scheme in this paper. The advantages of fast response, less overshoot and small control chattering prove the feasibility and effectiveness of the proposed control scheme.

RETRACTED: A semi-physical simulation platform of attitude determination and control system for satellite

A semi-physical simulation platform for attitude determination and control system is proposed to verify the attitude estimator and controller on ground. A simulation target, a host PC, many attitude sensors, and actuators compose the simulation platform. The simulation target is composed of a central processing unit board with VxWorks operating system and many input/output boards connected via Compact Peripheral Component Interconnect bus. The executable programs in target are automatically generated from the simulation models in Simulink based on Real-Time Workshop of MATLAB. A three-axes gyroscope, a three-axes magnetometer, a sun sensor, a star tracer, three flywheels, and a Global Positioning System receiver are connected to the simulation target, which formulates the attitude control cycle of a satellite. The simulation models of the attitude determination and control system are described in detail. Finally, the semi-physical simulation platform is used to demonstrate the availability and rationality of the control scheme of a micro-satellite. Comparing the results between the numerical simulation in Simulink and the semi-physical simulation, the semi-physical simulation platform is available and the control scheme successfully achieves three-axes stabilization.

Control of the Electric Load Simulator Using Fuzzy Multiresolution Wavelet Neural Network with Dynamic Compensation

A fuzzy multiresolution wavelet neural network (FMWNN) controller with dynamic compensation (DC) is proposed to address the complexities of the electric load simulator (ELS). The FMWNN acts as a main torque tracking controller, which takes full advantage of the merits of an ideal sliding mode, fuzzy rules, and multiresolution WNN. The fuzzy algorithm is used to dynamically adjust the weights of the WNN and effectively accelerate the convergence rate. In addition, the DC controller is designed to greatly decrease the effect of the approximation error and guarantee the system stability in the sense of the Lyapunov theory. Finally, the proposed algorithms are carried out on the semiphysical simulation platform, the precision and superiority of which are comparatively verified based on the simulation results.

Horizontal-Plane Trajectory-Tracking Control of an Underactuated Unmanned Marine Vehicle in the Presence of Ocean Currents

Based on an integral backstepping approach, a trajectory-tracking control algorithm is proposed for an underactuated unmanned marine vehicle (UMV) sailing in the presence of ocean-current disturbance. Taking into consideration the UMV model's fore/aft asymmetry, a nonlinear three-degree-of-freedom (3DOF) underactuated dynamic model is established for the horizontal plane. First, trajectory-tracking differences between controllers designed based on symmetric and asymmetric models of the UMV are discussed. In order to explicitly study the effect of ocean-current interference on the trajectory-tracking controller, the ocean current is integrated into the kinematic and dynamic models of the UMV. Detailed descriptions of distinct trajectory-tracking control performances in the presence of different ocean-current velocities and direction angles are presented. The well-known persistent exciting (PE) condition is completely released in the designed trajectory-tracking controller. A mild integral item of trajectory tracking error is merged into the control law, and global stability analysis of the UMV system is carried out using Lyapunov theory and Barbalat's Lemma. Simulation experiments in the semi-physical simulation platform are implemented to confirm the effectiveness and superiority of the excogitated control algorithm.