Shaoping Wang

Time delay oriented reliability analysis of Avionics Full Duplex Switched Ethernet

Besides the hardware/software failure of switched Ethernet, the capability of data transmission affects its performance and reliability. After summarizing the influence factors of Ethernet service capability, this paper focuses on the time delay oriented reliability model and analysis method. Based on the operational mechanism analysis of Avionics Full Duplex Switched Ethernet (AFDX), this paper emphasizes on the main factors that affect the data transmission capability, viz. the traffic shaping delay and scheduling delay. With the token bucket principle, this paper carries out the traffic shaping to decrease the sudden traffic disturbance. Based on First Come First Service (FCFS) strategy, this paper provides the appropriate service and controls the multiple virtual links in real time. Combining the traffic shaping delay and adjustment delay to traditional reliability model, this paper establishes the integrated reliability model to evaluate the reliability of AFDX.

High performance torque controller design for electric load simulator

Electric load simulator (ELS) is an important equipment in hardware-in-loop (HIL) simulation which exerts aerodynamic load to the actuation system according to the flight condition. Due to the inherent extraneous torque coupling by actuation system, the most important issue for ELS is how to eliminate the influence of extraneous torque. This paper presents a powerful model-based adaptive robust torque controller, which transfer the external disturbance elimination problem to performance-oriented problem under uncertainties and non-linearities. The backstepping design via adaptive robust control Lyapunov function is exploited to construct specific control law for ELS. Extensive comparative results indicate that the proposed controller is effective to achieve a guaranteed transient as well as final tracking accuracy in the presence of both parametric uncertainties and uncertain nonlinearities.

Integrated reliability metrics to assess fault tolerant control system

This paper presents an integrated reliability definition and mathematical metrics based on function reliability and performance reliability, in which the function reliability highlights failure causality from system to components and the performance reliability focuses on the dynamic performance degradation with operational time. Based on the simulation techniques, this paper establishes the simulation template for typical control system that can describe the dynamic process of performance in continuous time until the parameters exceed the designated threshold. Considering the influence of monitoring voting system, this paper establishes the Markov model with fault detection rate, isolation rate and false alarm rate, investigates the influence to whole system reliability of such factors. Application of triple redundant actuator indicates that the integrated reliability assessment makes full use of the advantages on dynamic fault tree analysis, Markov Model and control performance simulation, and solves the difficulties on calculating reliability considering the characteristics of monitoring system and performance degradation.

False alarm mechanism and control of aircraft hydraulic system

Built-in-Test (BIT) is widely used in aircraft to improve the systems reliability and safety. However, the false alarm of BIT makes it difficult to practical. After investigating the mechanism of false alarm of BIT from sensor failure, signal coupling, unreasonable threshold and uncertainty of fault decision method, an improved fault diagnosis method integrated with sensor redundancy configuration, delay decision and dynamic threshold is proposed. The result from the ground simulation platform indicates the methods effectiveness.

A new method for performance degradation assessment of solid lubricated bearings

Solid lubricated bearing is a key component in spacecrafts and various other applications. Its performance degradation assessment is very important due to the demand of high reliability of aeronautic products. In this paper, a new method consists of wavelet packet decomposition and improved fuzzy c-means is proposed. The vibration signal of tested bearings is decomposed and one node is used to reconstruct the original signal. Then the energy of the reconstructed signal is calculated and the subjection of the energy to normal state is used as performance degradation indicator. Improved fuzzy c-means is used to calculate the subjection matrix. After the test, several tested bearings are observed with an scanning electron microscope.

Prognostic analysis based on updated grey model for axial piston pump

Gradual degradation is the pivotal factor in prognostics analysis while the performance degradation is difficult to get with limit or blurry data. Based on the failure mechanism analysis of axial piston pump, the abrasion resulting from uneven contact between valve plate and cylinder barrel is the crux. With measured value, this paper presents a updated grey model and algorithm flow based on fix dimension updated technique and δ filter, in which the grey model overcomes the influence of uncertainty and disturbance and δ filter improves the quality of original data. Through renewing the information of grey model dynamically, the precision of prognostics increases greatly. Application indicates that the updated grey prediction algorithm could strengthen the scoring of new data and improve the prognostic accuracy with limit data.

Auto-tuning PID module of robot motion system

In order to make the movement of mobile robot more smoothly, this paper designs a Auto-tuning PID module for mobile robot motion system. Based on the systematic mathematical model, this paper presents a least-square real-time parameter estimation algorithm with forgetting factor and incremental PID controller algorithm, and provides PID parameters optimization algorithm for the minimization of objective function. The digital signal controller Microchip dsPIC30F4011 is chosen as the core of master control system to accomplish the design of system software and hardware. The results of spot test in mobile robots platform indicates that self-tuning PID control system can real-time estimate the controlled object parameter, real-time set adjust the controller parameters, then adapt to controlled object variance. So the auto-tuning PID control module is robust with good performance and anti-disturbance capability.

Synchronization control of hydraulic horizontal regulation system

This paper presents a control algorithm to address the leveling issue for lifting vehicle. The leveling system is achieved by electro-hydraulic system because of its advantages, such as small size-to-power ratios and so on. As four cylinders used to achieve synchronization, the issue of cylinder redundancy appears. In order to address this issue, the approach that two cylinders are only allowed to move in the same time is used. The two moving cylinders both are at the front of vehicle or at the back of vehicle. So the leveling issue is converted to motion synchronization of dual-cylinder. The design of controller to achieve motion synchronization of dual-cylinder is presented. The synchronization controller is a double loop controller. Inner-loop controller is a PID controller that is used to achieve the tracking performance of individual cylinder. Outer-loop controller is a compensation controller that is used to compensate the synchronization error of the cylinder the displacement of which is smaller. Simulation results on a dual-cylinder system verified the effectiveness of the proposed approach.

Multidisciplinary modeling method and simulation for Electro-Hydrostatic Actuator

Electro-Hydrostatic Actuator (EHA) is an integrated system whose performance is related to many disciplines, such as electrics, mechanics, hydraulics and control. In order to achieve the performance optimization, the best way is to balance the multidisciplinary and realize the integrated optimization. This paper focuses on the collaborative design and simulation based on commercial software AMESim for hydraulic and Matlab for control, in which the mutual design could harmonize the designed parameters and dynamic performance synchronously. The application indicates that the multidisciplinary model is practicable and effective.

Electrohydrostatic actuator collaborative optimization considering control performance and reliability

When design complex product like Electrohydrostatic Actuator (EHA), all of the experts from different disciplines need to co-design and cooperate. Design variables in different disciplines couple together and affect the object functions, constraint condition. This article use Multidisciplinary Design Optimization (MDO) method — Collaborative Optimization (CO) to design and optimize EHA. When performing the structure design of EHA we consider two disciplines which are control discipline and reliability discipline. When performing the reliability design, the stress and strength should be considered as stochastic variables. We use load-strength interference model to describe the relationship between stress and strength distribution. With the CO method, we can get the mass of the EHA system has decreased. The control performance and reliability of the system are greatly improved.