Abstract
The fiber tension should be kept constant during the automated placement of fiber prepreg. The velocity of the fiber placement end-effector moving on complex aircraft panel mould surface varies rapidly, which greatly disturbs the precision of tension control. This paper proposes a tension control strategy combining active control and passive control. The pay-off motor controls the fiber tension directly and a passive dancer roll is designed theoretically as the equipment for attenuation of tension disturbance to realize the real-time compensation of low-frequency velocity variations. The nonlinear model of tension control system, which includes the dynamics of the passive dancer roll, is established, and the effect of dancer roll parameters on its disturbances attenuation performance is analyzed. The controller is designed using the H∞ mixed sensitivity method. An experimental tension control precision about 2% is obtained at stable placement speed on the automated fiber placement (AFP) machine. The experiments also indicated that the tension would not vary over 1 N at a maximum acceleration of 4 m/s2.
Highlights
Composite materials are widely used for aeronautic application, and the automated fiber placement (AFP) is especially suitable for the manufacture of large composite structures, such as fuselage and S-shaped inlet, due to its high efficiency, high quality, and strong adaptability [1, 2].e fiber tension has important influence on the strength and fatigue resistance of composite materials, because the tension variations may lead to wrinkles and other defects, even cause the fiber to break [3, 4]. e damage to the fiber increases as the tension increases in the placement process, and higher tension on the fiber results higher breakage and neps [5]
E fiber tension has important influence on the strength and fatigue resistance of composite materials, because the tension variations may lead to wrinkles and other defects, even cause the fiber to break [3, 4]. e damage to the fiber increases as the tension increases in the placement process, and higher tension on the fiber results higher breakage and neps [5]
E green arrows in Figure 8 represent the transmission line of the fiber feeding system, which is consistent with the structure in Figure 2. e end-effector of the AFP consists of 16 sets of fiber feeding mechanisms, each of which is equipped with a pay-off motor for controlling the fiber tension, a backing film motor for recovering the stripped backing film, a passive dancer roll, a tension sensor, and three guide rolls leading to the compaction roll. 16 sets of fiber are concentrated at the end of the compaction roll for placement
Summary
Composite materials are widely used for aeronautic application, and the automated fiber placement (AFP) is especially suitable for the manufacture of large composite structures, such as fuselage and S-shaped inlet, due to its high efficiency, high quality, and strong adaptability [1, 2]. Tran and Choi [8,9,10] proposed an improved mathematical model for roll-to-roll system in printing industry and designed tension controller using backstepping method to realize precise tension control of paper. Ere are multiple actuators between spans to reduce disturbances, and the precision and robustness of tension control can be effectively ensured by controlling the speed difference of rolls and adjusting the position of the active dancer roll. E motion path of the end-effector is planned according to the surface of the aircraft panel mould, and the rewinding speed depends on the compaction roll with the AFP moving, so the precise control and measurement of the speed of placement is not feasible. Different from the speed difference control or the dancer roll position control, the stability of direct tension control is affected by Passive dancer
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