Damped Ultra-light Deployment Mechanism (DUDM) Characterisation of integrated damping features for elastic collapsible CFRP hinges

Objectives

The objective of this activity is to develop and test a collapsible flexible hinge, based on CFRP blades, with improved damping and, most important, significantly reduced end-of-travel shock, without the risk of overshooting. The solution needs to be based on the available hinge design (i.e. UDM design). The required solutions for damping and shock reduction need to be fully integrated in the hinge design and shall not be provided by an additional mechanism, as this would jeopardize the present advantages of the elastic collapsible hinge. Therefore, integrated solutions with passive damping (no power consumption) or active damping (no power consumption) and minimal requirements to external interfaces need to be identified and fitted to the existing hinge design. Particular care has been taken to achieve the simplest design, but also to achieve manufacturing and integration approach that is as simple as possible. This easy to handle and produce approach increases the market potential of the final product in the future.

Challenges

One of the biggest challenges is very low end-of-travel shock. Together with the objective of low mass and power consumption, this addresses high requirements to the damping material. Where visco-elastic materials which representing a passive damping are strongly affected by thermal environment and active damping solutions often require high amounts of power, a well-balanced solution combining the advantages of both has to be developed. Taking the changing torque during deployment into account, the damping device should automatically balance the resistive and deployment torque in order to ensure a smooth deployment, the required low shock and to avoid overshooting.

Benefits

The here developed deployment mechanism is designed to be ultra-lightweight, yet to be of high stiffness. The passively driven deployment by preloaded CFRP blades together with its shape memory alloy damping unit achieve a sufficient deployment torque yet a very low latching shock in the end. Due to the active damping, an overshooting can be prevented.

Featuring a stowed envelope of 283 x 230 x 118 mm³ it deploys to a final size of 125 x 230 x 265 mm³ while in total only having 682g of mass.

Features

The main features of the DUDM are its ultra-light weight but on the same side its high stiffness. It is an active deployment mechanism, which is damped with a shape memory alloy. So that it achieves a low latching shock in the end and overshooting after the full deployment can be prevented.

A deployment is possible within 200° of deployment angle, each position between full deployed (0°) and 200° is possible.

Featuring a stowed envelope of 283 x 230 x 118 mm³ it deploys to a final size of 125 x 230 x 265 mm³ while in total only having 682g of mass.

The measured average stiffness all exceed the requirements in one magnitude.

Adding to the deployment features, the DUDM has a Hold Down and Release Mechanism interface, so that a Release Device can be mounted onto this.

System Architecture

The general design of the DUDM is shown hereafter. It consists out of two CFRP interface plates with bonded titanium brackets, three CFRP blades (1 Straight Blade and two X-Blades) which are bonded and clamped with the titanium brackets and an HDRM. The arrangement of the blades results in a structure similar to a frame and provides a stiff structure in the deployed position. It allows a bending of the DUDM up to an angle of 200°.

The most critical and hence most important parts at DUDM level are the blades. CFRP was chosen for the blades mainly due to the low and controllable coefficient of thermal expansion (CTE) in axial direction. This is important for low thermal distortion and high accuracy. The Mounting Brackets are made of TiAl6 in order to meet a low CTE and high stiffness. The damping spring is made of a Titanium Nickel Alloy which is isolated from the structure by plates made out of PEEK. 

Plan

The project has been subdivided in:

  • Task 1: “Requirements specification and Concept Trade off”, where several active and passive concepts have been assessed and evaluated with the objective to go on with.
  • Task 2: “Preliminary Design” of one active and one passive concept.
  • Task 3: “Demonstrator Development Plan” has defined a strict way forward through the next Tasks.
  • Task 4: “Development Sample Tests” were performed to evaluate the most suitable concept which is used to enable-
  • Task 5: “Detailed Design” of the selected concept.
  • Task 6 and 7: has covered the Manufacturing, Assembly and Test Phase.  

Current status

A damping device has been successfully developed and a wide test campaign has been performed to validate the requirements. In addition, a new blade material has been used and an all-embracing material validation campaign was successfully performed. Thereby this damped deployment hinge is qualified up to Technology Readiness Level 5. 

ESA Contacts

Status date

Wednesday, February 6, 2019 - 12:16