The aircraft full-scale fatigue test is widely used in the modern aircraft industry for the safety of flight. Generally, the aircraft full-scale fatigue test is achieved by structural loading; multiple hydraulic actuators are used to apply load for force control. The fatigue loading test takes approximately several years. A key challenge is how to accelerate the loading frequency to shorten the total test time. Nevertheless, when pluralities of hydraulic actuator simultaneously increase the loading frequency, the mutual coupling force from the low rigidity of the aircraft structure will cause a large loading error, meaning that the test cannot be implemented. Although it is possible to reduce error by adding sensors, the force sensors need to connect several kilometers of cable. This paper proposed a novel motion synchronous composite decoupling control strategy with fewer sensors. The control method compensates the negative coupling effect of the channels by integrating the command signals and feedback signals of all channels. It can suppress coupling force and reduce errors at higher frequencies, thereby shortening the experiment time. Opposed to traditional decoupling control methods, advantages of this strategy are that it only needs force sensors and it does not need additional displacement or velocity and acceleration sensors to collect state variables for building the state space. Furthermore, it has been experimentally verified that the new motion synchronous composite decoupling control method can indeed guarantee sufficient control accuracy when the test frequency is increased. The method has great economic significance for shortening test duration.
A novel dual Halbach array is proposed in this paper to increase the output performance of tubular linear machines. The magnetic field distribution in three-dimensional (3D) space is formulated with Bessel functions analytically. Following that, the modeling of force output for linear machines with threephase windings is carried out based on Lorentz force law. The formula component of force ripple is separated from the analytical expression of total force. It is found that for multi-phase tubular linear machines, the force output and force ripple are not only closely related to the instantaneous position of the mover, but also the starting position. Therefore, the force output of the linear machine is formulated for three typical starting positions as a function of mover positions. The derived models are simulated with respect to the mover's motion. They are also validated with numerical results from finite element calculation. The study shows that an appropriate starting position of the mover helps to improve the output performance of the tubular linear machines. The proposed analytical force model can also be employed to analyze the influence of the structure parameters on the force output of linear machines with similar structures.
Linear machines are widely employed in robotics, transportation and manufacturing industries because complex rotation-to-translation conversion mechanism is no longer required. This paper proposed a novel tubular linear machine with dual permanent magnet (PM) Halbach arrays to achieve high force output performance. Based on Lorentz force law, the magnetic force output and force ripple for three-phase winding linear machine is formulated in analytical way. By taking advantage of the analytical models, the force output is simulated with respect to the motion of the mover. Numerical result is then obtained to validate the analytical force models. In addition, based on the technology of non-dimensionalization, the mathematical force models are employed to analyze the influence among the structure parameters on the force output and force ripple for design purpose of the tubular linear machines. The study in this paper could contribute to the design analysis and optimization of electromagnetic linear machines with similar poles patterns.
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