Flexgear

Background and motivation
In the course of the climate protection initiative, the trend of conserving resources and saving energy while maintaining or improving functionality through lightweight construction is becoming established in industry. The importance of lightweight design is also growing for gear technology. Around 90% of the drive trains of the 29,465 installed onshore wind turbines with an average rated power of 4 MW are based on large gearboxes with a diameter of > 1 m. Additional turbines with ≥ 5 MW are being planned in addition to meet the climate protection initiative targets by 2030. With an increase in the output of wind turbines, the dimensions and mass of the required gearboxes increase at the same time. This may be due to an increase in the diameter of the individual gears or to the addition of further planetary stages. An increase in the gearbox dimension also results in an increased nacelle mass as well as an enlargement of the bearing and tower construction of the wind turbine. This increase in material and production costs is associated with an increase in CO2 consumption for the production and operation of the turbines. In order to conserve resources and the associated energy savings, the material consumption in the design and manufacture of the gearboxes must be minimized by lightweight construction.

Objectives and approach
The overall objective of this project is to develop a concept for integrated lightweight gears with integrated load monitoring and to realize a demonstrator and test rig for validation. In combination with suitable manufacturing processes, the interdisciplinary solution approach is to achieve a mass reduction of up to 65% while simultaneously increasing the service life of the gears. The following sub-goals were derived for concretization:

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1. Design and verification of design guidelines for lightweight gears with flexible structures based on bio-inspired principles right into the gear rim: While lightweight concepts for gears have so far been limited to the basic body, the holistic approach provides for lightweight structures right into the individual teeth. This leads to direct weight savings. Consistent resource savings are also achieved by additive manufacturing of the gears. Thus, the planned lightweight concept additionally offers new design degrees of freedom to realize flexible structures, such as solid-state joints, in order to achieve specific compliance despite hardened surfaces and to compensate for load peaks. This task will be performed by AWI.
2. Integration of an inside sensing system with telemetry to validate the design guidelines on the developed demonstrator and to implement a condition monitoring system for proactive load peak compensation: The new design and manufacturing degrees of freedom allow the integration of sensor technology inside the gear. Short-term load peaks and individual gear conditions (e.g. deformations at critical points of the component) can thus be detected directly and do not have to be interpreted from indirect characteristics such as structure-borne noise, torques or temperatures. Thanks to fast data acquisition and processing, load peaks on the output side can be compensated within a few milliseconds by controlling the grid-feed inverters. This offers further CO2 savings potential because the gear units no longer have to be oversized for the load peaks.