Xiaoye Qi

Flux-Weakening Control of Nonsalient Pole PMSM Having Large Winding Inductance, Accounting for Resistive Voltage Drop and Inverter Nonlinearities

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.

Double Crossed Step-Down-Stress Accelerated Life Testing for Pneumatic Cylinder Based on Cumulative Damage Model

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.

Path classification and estimation model based prognosis of pneumatic cylinder lifetime

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.

A Superfluous Force Suppression Method Based on Structure Invariance Principle with Particle Swarm Optimization Algorithm

The key technology of load simulator is superfluous force suppression. This article uses a compensation method of structure invariance principle to solve the problem of superfluous force. Intelligent Particle Swarm Optimization algorithm based on the experimental data is used to identify parameters of the system so as to establish the mathematical model of which simulation result is consistent with the experimental result, and design a compensator based on this model to achieve the purpose using structure invariance principle to eliminate superfluous force.

Double-Crossed Step-Stress Accelerated Life Testing for Pneumatic Cylinder

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.

Research on Anti-Control of Missile Electro-Hydraulic Actuator Using Active Disturbance Rejection Control Method

Nowadays, the electro-hydraulic actuator plays an important role in some modern tactical missiles. High power, great robustness and high tracking precision are the most significant demands for the missile actuator. Therefore an advanced method of active disturbance rejection control (ADRC) is presented aiming at the dynamics of the system are highly nonlinear and have large extent of model uncertainties, such as tremendous changes in load. Firstly, a novel ADRC controller is designed for estimating and compensating disturbance based on the mathematical model of missile electro-hydraulic actuator. Then, the influence of rudder load on the system performance is analyzed in this paper. Simulation results show that the ADRC control approach can decrease the tracking error and enhance the robustness of missile electro-hydraulic actuator system when the rudder load changed tremendously. But the phenomenon of Anti-Control has disadvantageous effect on the transition period of actuator loop and evenly causes the system divergence.

Modeling Analysis and Simulation of Hydraulic Axial Piston Pump

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.

Comparison of drive performance of PM synchronous machine fed by inverters with different PWM strategies in constant torque and constant power regions

Constant torque and constant power operation performance of permanent-magnet synchronous motors, particularly in the constant power region, not only depends on the flux-weakening control schemes but also relies on the PWM strategies. In this paper, the hysteresis control and SVPWM (including linear and over-modulation) are considered due to their popularity. An improved current regulated delta modulation (CRDM) is developed to improve the performance in both constant torque and constant power regions. The analyses, verified experimentally, show that the improved CRDM strategy demonstrates an improved torque capability which is nearly the same as SVPWM in the constant torque region, and an enlarged speed range compared with hysteresis control.

Analysis of failure mechanism and stress influence on cylinder

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 cylinders moving parts with theory of cumulative damage, which demonstrates cylinders 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.

The application of active disturbance rejection control method to tactical missile electro-hydraulic actuator

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.