ADLAND - Adaptive Landing Gears for Improved Impact Absorption
Overview
Background & policy context:
The motivation for this research was to respond to requirements for high impact energy absorption in aircraft landing gears.
Typically, shock absorbers are designed as passive devices with characteristics adjusted either to the most frequently expected impact loads or to ultimate load conditions. However, in many cases the variation of real working conditions is so high that the optimally designed passive shock absorber does not perform well enough.
In contrast to the passive systems, this research focused on active adaptation of energy absorbing structural elements, where a system of sensors recognises the type of impact loading and activates energy absorbing components in a fashion that guarantees optimal dissipation of impact energy.
Objectives:
The ADLAND project dealt with evaluating the options for adaptive shock absorbers to be applied in aircraft landing gears. Analytical design procedures were developed to simulate different potential design options and the best practical solution was determined. The different hardware components regarding adaptive shock absorbers were developed and tested with regard to an adaptive landing gear model.
The project objectives were:
- to develop a concept of adaptive shock-absorbers;
- to develop new numerical tools for the design of adaptive vehicles and for the simulation of the adaptive structural response to an impact scenario;
- to develop technology for actively controlled shock-absorbers applicable in landing gears (there are two options: Magneto-Rheological Fluid-based (MRF) and Piezoelectric Valve-based);
- to design, model and perform repetitive impact tests of the adaptive landing gear model with high impact energy dissipation effects; and
- to design, produce and test in flight the chosen full-scale model of the adaptive landing gear.
Methodology:
The approach of the project focused on active adaptation of the energy absorbing system (equipped with sensors identifying impact in advance and controllable semi-active dissipaters) with the ability to adapt to extreme overloading during landing. The term active adaptation refers to the particular case of actively controlled energy dissipater, where the need for external sources of energy is minimised and the task for actuators is reduced to modify local mechanical properties rather than to apply externally generated forces. These applications of active control concept are usually more reliable, stable and cost-effective. Therefore, adaptive systems are more appropriate in the impact dissipation task than their fully active counterparts.
The main tasks defined for the project participants were:
- to develop an efficient methodology and strategy of control for the adaptive landing gears during landing impact (with assessment of its applicability and feasibility study);
- to develop MR fluid in accordance to the requirements defined by the consortium representatives from aeronautic industry;
- to develop, design and fabricate an adaptive landing gear utilising the MRF technology. The task in this problem did cover the following issues: design of the device in accordance to the aeronautic requirements, to develop the control unit, which withstand the timing requirements occurring in the case of the landing impact, laboratory validation of the developed and fabricated devices;
- to develop, design and fabricate a piezo-actuated adaptive landing gear, with controllability of the internal hydraulic fluid flow by means of a piezo-valve. The task in this problem did cover the following issues: design of the device in accordance to the aeronautic requirements, to design an appropriated fluidic duct and the piezo-valve head, to develop the control unit, which withstand the timing requirements occurring in the case of the landing impact, laboratory validation of the developed and fabricated devices;
- to validate experimentally in the laboratory conditions, the landing gears with the active systems for small passenger aircraft (1.1 t) and for small cargo aircraft (8 t), and the final task was
- to perform the field testing of the developed device on the small cargo aircraft.
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