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In this paper, taking the planetary roller screw for aircraft electro-mechanical actuator as the research object. The planetary roller screw exist four different designs which are widely used for different applications: these four designs are respectively known as standard planetary roller screw, inverted planetary roller screw, recirculating planetary roller screw and differential planetary roller screw. The composition, thread form, working characteristics and applicable occasions of these four different designs are analyzed and compared. Considering the possible relative slide between components, the angular and axial motion relationships are demonstrated in detail, and the relationships of structural parameters between components were obtained. The force analysis was performed at the contact point to analyze the transmission efficiency. The relation between the transmission efficiency and contact angle, helix angle was also deduced in consideration of the rolling friction and the relative sliding friction of the component. The results show that the transmission efficiency of the planetary roller screw rapidly increases with the increase of the helix angle and then gradually decreases. In addition, the efficiency gradually increases with the increase of the contact angle, and finally tends to be stable.

Current high power load simulators are generally incapable of obtaining both high loading performance and high energy efficiency. Simulators with high energy efficiency are used to simulate static-state load, and those with high dynamic performance typically have low energy efficiency. In this paper, the variants of secondary control (VSC) with power recovery are developed to solve this problem for loading hydraulic driving devices that operate under variable pressure, unlike classical secondary control (CSC) that operates in constant pressure network. Hydrostatic secondary control units are used as the loading components, by which the absorbed mechanical power from the tested device is converted into hydraulic power and then fed back into the tested system through 4 types of feedback passages (FPs). The loading subsystem can operate in constant pressure network, controlled variable pressure network, or the same variable pressure network as that of the tested device by using different FPs. The 4 types of systems are defined, and their key techniques are analyzed, including work principle, simulating the work state of original tested device, static operation points, loading performance, energy efficiency, and control strategy, etc. The important technical merits of the 4 schemes are compared, and 3 of the schemes are selected, designed, simulated using AMESim and evaluated. The researching results show that the investigated systems can simulate the given loads effectively, realize the work conditions of the tested device, and furthermore attain a high power recovery efficiency that ranges from 0.54 to 0.85, even though the 3 schemes have different loading performances and energy efficiencies. This paper proposes several loading schemes that can achieve both high dynamic performance and high power recovery efficiency.

The nose landing gear is a vital component of an aircraft,which has an important impact on the safety of the aircraft.This paper studies the system of nose landing gear steering on the basis of the gear and rack mechanism durability test of a certain type of civil aircraft landing gear steering. Furthermore,it puts forward a method of passive loading,which can simulate the friction when the nose landing gear reciprocating turning,and establishes the mathematical model. The simulation results show that the simulator can meet the requirements of load,and laid a theoretical foundation for the subsequent actual work.

The thesis presents a reconstruction of bottom surface of shoe last based on foot pressure distribution in order to relieve the influence caused by plantar pressure concentration. First, in order to match the plantar pressure data and the shoe last data, the shoe last data is processed to locate the center location of the heel, the sole and the big feet thumb. Then the pressure data is also processed to extract the corresponding data which is interpolated and fitted of the area of the heel, the sole and the big feet thumb. and then the establish area of bottom surface is determined depending on the pressure data of three area. Finally, based on the extracted pressure data and the convex-concave coefficient of pressure data, the reconstruction of bottom surface of shoe last is achieved.

Double Crossed Step-Down-Stress Accelerated Life Testing (DCSDS-ALT) discussed in this paper was implemented by switch down the double stresses alternately. Compared to constant stress test, step-stress test decreased specimen numbers, time and cost, and eventually well improve the accelerated testing efficiency. For pneumatic cylinder, the step-down-stress testing failure physics can be described as cumulative degradation model. By use of cumulative damage General Log-Linear relationship and Weibull assumption, the failure data obtained were equivalently converted to failure data under constant stress testing. Then the reliability specifications can be derived with better accuracy. The 5% of average lifetime estimation error and 1.85% of the characteristic lifetime error are very satisfying for pneumatic industrial lifetime prediction.

A technical challenge for large power loading test device is how to achieve both of high loading dynamic performance and high energy efficiency, consequently power recovery and reuse technology should be applied. Hydrostatic secondary control has reasonable dynamic performance for loading and benefits power recovery. However conventional secondary control based on constant pressure network (CPSCS) can still be further improved when using in loading test bench for hydraulic driving head. This paper proposes hydrostatic variable-pressure secondary-control (VPSCS), for which the corresponding system is designed. Subsequently by simulation with AMESim, the dynamic performance and energy feedback or recovery efficiency of CPSCS and VPSCS are analyzed and evaluated, and finally the works in the next step are presented. The conclusion shows VPSCS, compared with CPSCS, improves energy feedback efficiency by 18%~30% but has worse wave shape of load torque when using the servo pressure valve set designed preliminarily.

Co-simulation based on LMS Virtual.Lab Motion and Imagine.Lab AMESim was used on aircraft cabin door hydromechanical drive system design. By analysis of 1-D hydraulic model and 3-D mechanism model co-simulation, we draw the conclusion that over-running load accounts for hydraulic motor over speed. To improve hydraulic system, the one-way throttle valve was employed to balance the over-running load according to the co-simulation results. Subsequently, the co-simulation outcome showed the improved-designed hydraulic system controlled the over-running load more effectively. Therefore, a convenient, reliable and accurate method of hydraulic system based on over-running load balance was available.

Prognosis is a key technology to improve reliability, safety and maintainability of products, a lot of researchers have been devoted to this technology. But to improve the predict accuracy of remaining life of products has been difficult. To predict the lifetime specification of pneumatic cylinders with high reliability and long lifetime and small specimen, this paper put forward the prognosis algorithm based on the path classification and estimation (PACE) model. PACE model is based entirely on failure data instead of failure threshold. Pneumatic cylinders normally characterize with failure mechanism wear and tear. Since the minimum working pressure increases with the number of working cycles, the minimum working pressure is chosen as degradation signal. PACE model is fundamentally composed of two operations: path classification and remaining useful life (RUL) estimation. Path classification is to classify a current degradation path as belonging to one or more of previously collected exemplary degradation paths. RUL estimation is to use the resulting memberships to estimate the remaining useful life. In order for verification and validation of PACE prognostic method, six pneumatic cylinders are tested. The test data is analyzed by PACE prognostics. It is found that the PACE based prognosis method has higher prediction accuracy and smaller variance and PACE model is significantly outperform population based prognostics especially for small specimen condition. PACE model based method solved the problem of prediction accuracy for small specimen pneumatic cylinders’ prognosis.

This paper proposes an improved flux-weakening control method to improve the drive performance of nonsalient pole permanent magnet synchronous motors having large winding inductance and consequently an infinite constant power speed ratio. The proposed method consists of two parts. The first part utilizes the voltage differences between the input and output of a minimum-magnitude-error over-modulation block to modify the d-axis current references. The second part uses the compensated q-axis voltage, in which the resistive voltage drop and the distorted voltage due to inverter nonlinearities are taken into account, to detect the maximum torque per voltage (MTPV) line. Under the MTPV condition, a PI controller with a low-pass filter is presented to modify the q-axis current reference. With these two parts, the bus voltage utilization in the proposed method is close to the six-step operation and the actual current trajectory approaches the ideal MTPV line. As a result, the drive performance in the whole flux-weakening region is optimized in terms of maximizing the output torque/power. The method also shows a good performance in transient response. Effectiveness and superiorities of the proposed method are verified by experimental results.

Based on characteristics of AMESim software and structural characteristics of aviation piston pump, the model of a rational aviation piston pump was constructed after simplified. In this issue, the equations of motion of the piston and the process of oil suction and oil discharge for a single piston are theoretically analyzed. The effects of the four kinds of leakage to the loss of flow rate and to the pulsing of the pump are emphatically analyzed. Through build the model of axial piston pump, which provides certain theoretical basis for design different kinds of model of the piston pump.

This paper discusses the principle and method of Double-Crossed Step-Down-Stress Accelerated Life Testing (DCSDS-ALT) for pneumatic cylinders. As to pneumatic cylinder, the step-down-stress testing failure physics can be described as cumulative degradation model. Temperature and frequency are normally chosen as the test stresses. The failure data obtained under DCSDS-ALT testing steps can be converted to those under constant stress testing. And the reliability specifications can be derived accordingly. To compare Double-stress ALTs with traditional constant stress testing shows Double-stress ALTs can meet the accuracy demand. The 5% of average lifetime estimation error and 1.85% of the characteristic lifetime error are very satisfying for pneumatic industrial lifetime prediction.

Cylinder, which converts pressure of compressed gas into mechanical energy, is one of main pneumatic actuators in electromechanical products. With application of cylinder becoming broader and broader, the demand on high reliability of cylinder gets more and more urgent. In order to improve the reliability of cylinder, it must be made clear the failure mechanism of it beforehand. This paper first shows detailed structure of the tested A series of cylinder, then gives deep insight into the failure mechanism of this kind of cylinder with experimental phenomena gained from a large number of accelerated lifetime tests, such as wear of piston edge, accumulated debris in the lid of piston rod, noticeable ground traces on the piston rod and damage of the piston sealing ring. This paper also presents a microscopic explanation to the wear process of cylinder's moving parts with theory of cumulative damage, which demonstrates cylinder's micro failure process. At last it analyzes failure data obtained in the accelerated lifetime tests using lifetime data analysis software, mainly including the influence each stress (temperature, actuating frequency, pressure and speed) has on the lifetime of cylinder and why this happens, which further validates the failure mechanism of this kind of cylinder is wear of moving parts.

Nowadays, electro-hydraulic actuator plays an important role in some modern tactical missiles. High power, great robustness and high tracking precision are the most significant targets for the actuator. However, the dynamics of the electro-hydraulic position servo system are highly nonlinear and have a large extent of model uncertainties, such as tremendous changes in the rudder load and external disturbance torque. So an advanced method of active disturbance rejection control (ADRC) is presented in this paper. Firstly, the general principle and structure of the ADRC strategy are introduced in order to improve the robust performance of the system. Then, a novel ADRC controller is designed for estimating and compensating total disturbance based on the mathematical model of the system. Compared with proportional integral derivative (PID) control, various simulation results show that the ADRC control approach can give faster and accurate response, and enhance the robustness of the system. Therefore, the ADRC control strategy is much superior in dealing with dynamic uncertainties and external disturbance for the electro-hydraulic actuator position servo system.

The abilities of synthesized function, intelligent control and health monitor for airborne utilities are becoming more and more important by which all the systems work efficiently and coordinately can be ensured. avionics and other systems work in order. This paper works over several items about UMS by introducing updated simulation framework and redundancy and fault tolerance. In order to obtain high performance of distributed process ability, heuristic job dispatching algorithm and hydrodynamic load balancing strategy are used to solve the static job dispatch and dynamic job scheduling respectively. Dynamic fault tolerance load balancing with and without failure occurs are simulated. Experiment result shows that communication cost is minimized, multiplex task redundancy and system real time performance are finally satisfied.

Pneumatic pressure regulator is an important element in pneumatic fluid power systems; it decompresses and regulates the pressure of system, so its performance determines the system's performance and its reliability must be grasped. The paper firstly presents a method about the reliability test circuit of pneumatic regulators, which include test conditions, test circuit and threshold levels; then analyses the fault mechanism and gives FMEA(Failure Mode and Effects Analysis) and FTA(Fault Tree Analysis); finally, by test data analyses and regulator dissolving, finds the major fault model and gives a life extend method. These permit the assessment of pneumatic regulators' reliability and provide a direction to improve their preferences.

A distributed fully automatic control scheme integrated with the advanced measurement sensors is designed to fulfill the precise control to growth process of the monocrystal silicon growers distributed in different locations. This scheme may meet the demand on large scale industrialization and high productive yield of bulk-material in solar energy applications.

Accelerated life testing (ALT) for the airborne hydraulic pump is a good way to obtain the reliability of airborne hydraulic pump under a more severe environment in a short period of test time. For fully thinking of energy saving, a new kind of technique taking hydraulic motor to recover energy that exists in traditional load subsystem is adopted. The possibility and performance of the ALT system, consisting of a DC motor, a variable-displacement pump and a variable-displacement motor, has been analysed. The model of the system has been made by bondgraph simulation technique and the hydrostatic power-distribution transmission has been studied. On the one hand, the new technique can reduce the loss of energy and avoid high temperature of hydraulic oil, but on the other hand, it can add to the difficulties of strong robust control. A series of simulations are performed, and the results show that the new technique for energy saving is satisfactory and the robust character of the system should be further studied.