Overview
One target of actual development activities for helicopter drives is the substitution of the conventional swash plate actuation based on hydraulic actuators by electro-mechanical actuators. In comparison to hydraulic actuators the jam of the electro-mechanical actuators has to be considered by a jam tolerant system design.
A possible solution is a redundant system configuration with two identical actuators at the activating positions. In case of a jam the failed actuator has to be disconnected from the drive in very short time by a fast activating actuator. In regard to the requirements no state-of-the art disconnect device is applicable.
The development of the disconnect device covered two different principles:
- reversible system, preferred electro-mechanical
- “single-shot” system, preferred pyrotechnical
Therefore, the project work was carried out by 4 cooperation partners:
- The Institute of Engineering Design and Industrial Design of the University of Stuttgart (IKTD) has research experience in and expert knowledge on the development of fast operating connect/disconnect devices.
- The Italian company Umbra (Umbra) is a highly competent manufacturer and supplier of components for the aerospace industry like ballscrews, actuators and EMA drives.
- The German company PyroGlobe is a highly competent manufacturer and supplier of pyrotechnical components and will participate on the “single-shot” system.
- The Swiss company phi Engineering has experience in methodical product development and will participate on a “single-shot” system beside pyrotechnics.
During investigations performed by the IKTD a wide range of possible connect/disconnect principles were reviewed and concept studies were carried out in this context. This represented a promising basis for a continuative research work and a successful development may be expected. The experience of the industrial partners ensured the realisation of the prototype considering the aerospace requirements.
Funding
Results
Executive Summary:
The FASTDISC project was part of the CleanSky activity System for Green Operations (SGO). One demonstration objective in this research program was the development of a fully electric swash plate actuation.
For fully electrical helicopters the electrification of the primary flight control is considered to be the key technology. The primary flight control of helicopters is performed by positioning of a swash plate with three degrees of freedom. Since the loss of one of these degrees of freedom is classified as safety-critical, the control system requires a fail-safe and fault-tolerant design. The research focuses at the direct replacement of hydraulic actuators by electromechanical ones. A special feature of the electromechanical actuators is that the mechanical jam of the drive train is classified as a safety-critical failure. In the current approach redundant electromechanical actuators were implemented on system level, while a disconnect device (DD) was installed in the drive train of each actuator to prevent a potential mechanical jam failure. When a jammed electromechanical actuator wwas decoupled from the flight control system, the redundant actuators were still capable to take over the control function.
One main contribution to this technology was followed up in the HEMAS project which comprised an electromechanically actuated DD. The FASTDISC project aimed at improvements on the design, further analysis on DDs and the realisation of two advanced designs covering the following principles:
- reversible disconnect device (RDD), preferred electromechanical
- irreversible disconnect device (IDD), preferred pyrotechnical
- The project work was devided in three work packages:
- Study and evaluation of disconnect device concepts
- Disconnect devices detailed design
- Disconnect devices manufacturing and validation testing
- And carried out by 4 cooperation partners:
- the Institute of Engineering Design and Industrial Design of the University of Stuttgart (USTUTT)
- the Italian company Umbra (Umbra)
- the German company PyroGlobe (PyroG)
- the Swiss company phi Engineering (phi)
In concept studies six reversible and six irreversible mechanisms were developed and described in detail. An electro-magnetic principle for the RDD and a pyrotechnical principle for the IDD were selected for detailed prototype design.
The detailed design and the test specification were approved during the CDR. For both RDD and IDD prototypes were manufactured.
Most of the test addressed in the validation testing could be passed successfully. Especially the disconnect functionality and the endurance and the environmental capabilities could be validated. Only the RDD show an insufficient disconnect behavior if only one coil of the solenoid is activated and at low temperatures. Other shortcomings are insufficient static stiffness of the IDD and insufficient backlash of both RDD and IDD. Therefore, design modifications and recommendations were derived to achieve the requirements and for improvement of the prototype design.
As a result, the project work had carried out disconnect devices heigly reliable for primary flight control systems, in compact design for the swash plate actuation and of low weight for aerospace applications.