Liebherr (Germany)

Aerospace industry is moving towards a more electric aircraft (MEA) or even an all-electric aircraft (AEA), which will incite the focus on reducing the total harness mass and complexity, thus employing powerline communication (PLC) technique seems to be a potential solution to be implemented for airborne uses. This paper explores the feasibility to implement PLC technology over aircraft DC powerline, fed by switched-mode power supply. First, a channel characterization and analysis were conducted, also an adaptive stage was discussed and designed to transmit the data over an already existing powerline. Furthermore, the channel capacity was estimated along with the required data signal level. This study investigates also a real-case context with the use of switched-mode dc/dc converter which effect the PLC performance and signal integrity. Eventually, PLC implementation and tests were conducted as well as discussed from latency, bit error rate (BER) and EMC compliance perspective with the RTCA DO-160G standard requirements.

Over the past years, the number of electrical systems in airplanes, and thus their power ratings have been rising. Therefore, the optimization of devices and actuators regarding efficiency and power density has become increasingly important. Besides the large topic of weight reduction at component level, aircraft manufacturers and several research projects have focused on the topology of the entire electrical grid. One possible topology may divide the whole network into subnets and an active power filter maintains the power quality at the connection to the main bus. This solution allows the use of simple diode bridge rectifiers in all power electronic devices within the subnet, which results in increased reliability, power density and reduced costs. Since most of the actuators e.g. in a wing are not driven permanently and not simultaneously, the power rating of this active power filter is significantly smaller than the power rating of the entire subnet. This paper presents the control algorithm for an active power filter for aerospace application, which requires robust behaviour towards frequency transients and high compensation accuracy in steady state operation.

Abstract In this study, a high-speed on/off digital valve was developed for use in a hydraulic control system. The device basically consists of a poppet valve acting as the main valve, and a multilayered piezoelectric (PZT) actuator for driving the poppet valve. A hydraulic amplifier was adopted to increase the actuation of the PZT actuator to the poppet valve. A compensation mechanism was set up to reduce this temperature effect in the hydraulic actuation of the PZT actuator. This problem arises when the oil temperature increases and causes the valve displacement to fluctuate slightly.The static and dynamic characteristics of the device were investigated by experiment and computer simulation. As a result, it was found that the switching time of the valve is less than 0.7 ms. Moreover, the valve can be driven by a PWM carrier wave using frequencies of up to 500 Hz. Additionally, the validity of the temperature compensation mechanism was confirmed. Hence, this valve may be determined as feasible device to b...