Space engineering - Guidelines for electrical design and interface requirements for actuators

In general terms, the scope of the consolidation of the electrical interface requirements for electrical actuators in the EN 16603-20-21 (equivalent to ECSS-E-ST-20-21) and the relevant explanation in the present handbook is to allow a more recurrent approach both for actuator electronics (power source) and electrical actuators (power load) offered by the relevant manufacturers, at the benefit of the system integrators and of the European space agencies, thus ensuring:
- Better quality
- Stability of performances
- Independence of the products from specific mission targets.
A recurrent approach enables manufacturing companies to concentrate on products and a small step improvement approach that is the basis of a high quality industrial output.
In particular, the scope of the present handbook is:
- To explain the type of actuators, the principles of operation and the typical configuration of the relevant actuator electronics,
- To identify important issues relevant to electrical actuators interfaces, and
- To give some explanations of the requirements set up in the EN 16603-20-21.

Raumfahrttechnik - Richtlinen für das elektrische Design und die Schnittstellenanforderungen von Stellmotoren

Ingénierie spatiale - Règles de design électrique et exigences d’interfaces pour les actionneurs

Vesoljska tehnika - Smernice za električno načrtovanje in zahteve vmesnikov za prožilnike

Na splošno naj bi konsolidacija zahtev za električni vmesnik za električne pogone v standardu EN 16603-20-21 (enakovreden dokumentu ECSS-E-ST-20-21) in ustrezna razlaga v tem priročniku omogočili ponavljajoči se pristop tako za elektroniko aktuatorjev (vir energije) kot električne aktuatorje (napajalna obremenitev), ki jih ponujajo ustrezni proizvajalci, v korist sistemskih integratorjev in evropskih vesoljskih agencij, s čimer se zagotovi:
– večja kakovost,
– stabilnost delovanja,
– neodvisnost izdelkov od ciljev posameznih misij.
Ponavljajoči se pristop podjetjem omogoča, da se osredotočijo na izdelke in pristop k izboljšanju z majhnimi koraki, ki je osnova za visokokakovostno industrijsko proizvodnjo.
Področje uporabe tega priročnika vključuje zlasti:
– razlago vrste aktuatorjev, načel delovanja in tipične konfiguracije ustrezne elektronike aktuatorja,
– prepoznavanje pomembnih vprašanj, povezanih z vmesniki električnih aktuatorjev, in
– nekaj razlag zahtev, določenih v standardu EN 16603-20-21.

General Information

Status
Published
Technical Committee
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
12-Jan-2022
Completion Date
12-Jan-2022

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Standards Content (sample)

SLOVENSKI STANDARD
SIST-TP CEN/TR 17603-20-21:2022
01-marec-2022
Vesoljska tehnika - Smernice za električno načrtovanje in zahteve vmesnikov za
prožilnike

Space engineering - Guidelines for electrical design and interface requirements for

actuators
Raumfahrttechnik - Richtlinen für das elektrische Design und die
Schnittstellenanforderungen von Stellmotoren

Ingénierie spatiale - Règles de design électrique et exigences d’interfaces pour les

actionneurs
Ta slovenski standard je istoveten z: CEN/TR 17603-20-21:2022
ICS:
49.140 Vesoljski sistemi in operacije Space systems and
operations
SIST-TP CEN/TR 17603-20-21:2022 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST-TP CEN/TR 17603-20-21:2022
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SIST-TP CEN/TR 17603-20-21:2022
TECHNICAL REPORT CEN/TR 17603-20-21
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
January 2022
ICS 49.140
English version
Space engineering - Guidelines for electrical design and
interface requirements for actuators

Ingénierie spatiale - Règles de design électrique et Raumfahrttechnik - Richtlinen für das elektrische

exigences d'interfaces pour les actionneurs Design und die Schnittstellenanforderungen von

Stellmotoren

This Technical Report was approved by CEN on 29 November 2021. It has been drawn up by the Technical Committee

CEN/CLC/JTC 5.

CEN and CENELEC members are the national standards bodies and national electrotechnical committees of Austria, Belgium,

Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,

Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia,

Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.
CEN-CENELEC Management Centre:
Rue de la Science 23, B-1040 Brussels
© 2022 CEN/CENELEC All rights of exploitation in any form and by any means
Ref. No. CEN/TR 17603-20-21:2022 E
reserved worldwide for CEN national Members and for
CENELEC Members.
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Table of contents

European Foreword ................................................................................................... 5

Introduction ................................................................................................................ 6

1 Scope ....................................................................................................................... 7

2 References .............................................................................................................. 8

3 Terms, definitions and abbreviated terms ............................................................ 9

3.1 Terms from other documents .................................................................................... 9

3.2 Abbreviated terms..................................................................................................... 9

4 Explanations ......................................................................................................... 11

4.1 Explanatory note ..................................................................................................... 11

4.2 How to use this document ....................................................................................... 11

5 Actuators Interface ............................................................................................... 12

5.1 Type of actuators .................................................................................................... 12

5.2 Coverage assumptions ........................................................................................... 16

5.3 Actuators electronics, general architecture ............................................................. 17

5.3.1 Overview ................................................................................................... 17

5.3.2 ARM block ................................................................................................ 21

5.3.3 SELECT block ........................................................................................... 21

5.3.4 FIRE block ................................................................................................ 22

5.4 Actuators electronic, timing sequence..................................................................... 22

5.5 Actuator electronics, failure tolerance ..................................................................... 24

5.5.1 Double failure tolerance ............................................................................ 24

5.5.2 Single failure tolerance .............................................................................. 26

6 Explanation of ECSS-E-ST-20-21 Interface Requirements ................................ 27

6.1 Functional general .................................................................................................. 27

6.1.1 General ..................................................................................................... 27

6.1.2 Reliability .................................................................................................. 27

6.2 Functional source ................................................................................................... 29

6.2.1 General ..................................................................................................... 29

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6.2.2 Reliability .................................................................................................. 30

6.2.3 Commands ............................................................................................... 33

6.2.4 Telemetry .................................................................................................. 35

6.3 Functional load ....................................................................................................... 38

6.3.1 General ..................................................................................................... 38

6.3.2 Reliability .................................................................................................. 39

6.4 Performance general .............................................................................................. 39

6.4.1 General ..................................................................................................... 39

6.5 Performance source ............................................................................................... 42

6.5.1 Overview ................................................................................................... 42

6.5.2 General ..................................................................................................... 44

6.5.3 Reliability .................................................................................................. 45

6.5.4 Telemetry .................................................................................................. 46

6.5.5 Recurrent products.................................................................................... 46

6.6 Performance load ................................................................................................... 48

6.6.1 General ..................................................................................................... 48

6.6.2 Reliability .................................................................................................. 48

6.6.3 Recurrent products.................................................................................... 49

Figures

Figure 5-1: Dassault pyro initiator ......................................................................................... 13

Figure 5-2: Pyro-valve (to be equipped with pyro initiators) .................................................. 13

Figure 5-3: Thermal knife (partially reusable – needing refurbishment) ................................ 14

Figure 5-4: Thermal knife activation (partially reusable – needing refurbishment)................. 14

Figure 5-5: Thermal knife (with thermal heads visible) .......................................................... 14

Figure 5-6: Glenair heavy duty HDRM (partially reusable – needing refurbishment) ............. 14

Figure 5-7: TINI Aerospace Frangibolt (reusable – manually resettable) .............................. 15

Figure 5-8: NEA split-spool based HDRM (partially reusable – needing refurbishment)........ 15

Figure 5-9: Arquimea pin-puller family (reusable – manually resettable) ............................... 15

Figure 5-10: Typical actuators electronic block diagram ....................................................... 18

Figure 5-11: Typical actuators electronic block diagram, variant 1 ........................................ 19

Figure 5-12: Typical actuators electronic block diagram, variant 2 ........................................ 20

Figure 5-13: Actuators electronics timing sequence ............................................................. 23

Figure 5-14: Actuators electronics timing sequence, different selected lines ........................ 24

Figure 6-1: Actuator electronics {V, I} characteristic ............................................................. 40

Figure 6-2: Example - case 1................................................................................................ 40

Figure 6-3: Example - case 2................................................................................................ 41

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Figure 6-4: Example - case 1 and 2 ...................................................................................... 41

Tables

Table 5-1: Actuators reusability ............................................................................................ 13

Table A-1 : Current driven, non-explosive actuators ............................................................. 51

Table A-2 : Current driven, explosive actuators .................................................................... 53

Table A-3 : Voltage driven actuators..................................................................................... 54

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European Foreword
This document (CEN/TR 17603-20-21:2022) has been prepared by Technical Committee
CEN/CLC/JTC 5 “Space”, the secretariat of which is held by DIN.

It is highlighted that this technical report does not contain any requirement but only collection of data

or descriptions and guidelines about how to organize and perform the work in support of EN 16602-

20.

This Technical report (CEN/TR 17603-20-21:2022) originates from ECSS-E-HB-20-21A.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

This document has been prepared under a mandate given to CEN by the European Commission and

the European Free Trade Association.

This document has been developed to cover specifically space systems and has therefore precedence

over any TR covering the same scope but with a wider domain of applicability (e.g.: aerospace).

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Introduction

The present handbook, and the relevant standard ECSS-E-ST-20-21, have been produced in a general

context to provide stable electrical interface specifications (both for the source and the load, for

functional and performance aspects).

The convergence within ECSS among agencies, of Large System Integrators and of a representative

group of electronic manufacturers on the identified requirement set can provide an effective way to

get more recurrent products for generic use, both for the actuator electronics (power source), and for

the actuators themselves, in a rather independent way from the final application.

The standard ECSS-E-ST-20-21 has therefore to be intended as a standard for product development,

and the present handbook as a guideline to understand the relevant requirements, the typical issues of

the actuators interfaces both at system and at equipment level.

This handbook complements ECSS-E-ST-20-21, and it is directed at the same time to power system

engineers, who are specifying and procuring units supplying and containing electrical actuators, to

power electronics design engineers, who are in charge of designing and verifying actuator electronics,

and to electrical actuators designers.

For the system engineers, this document explains the detailed issues of the interface and the impacts

of the requirements for the design of the actuator chain.

For design engineers, this document gives insight and understanding on the rationale of the

requirements on their designs.

It is important to notice that the best understanding of the topic of Actuators Electrical Interfaces is

achieved by the contextual reading of both the present handbook and the ECSS-E-ST-20-21.

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Scope

In general terms, the scope of the consolidation of the electrical interface requirements for electrical

actuators in the ECSS-E-ST-20-21 and the relevant explanation in the present handbook is to allow a

more recurrent approach both for actuator electronics (power source) and electrical actuators (power

load) offered by the relevant manufacturers, at the benefit of the system integrators and of the

European space agencies, thus ensuring:
• Better quality,
• Stability of performances, and
• Independence of the products from specific mission targets.

A recurrent approach enables manufacturing companies to concentrate on products and a small step

improvement approach that is the basis of a high quality industrial output.
In particular, the scope of the present handbook is:

• To explain the type of actuators, the principles of operation and the typical configuration of the

relevant actuator electronics,
• To identify important issues relevant to electrical actuators interfaces, and
• To give some explanations of the requirements set up in the ECSS-E-ST-20-21.
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References
EN Reference Reference in text Title
EN 16601-00-01 ECSS-S-ST-00-01 ECSS system - Glossary of terms

EN 16603-20-21 ECSS-E-ST-20-21 Space engineering - Electrical design and interface

requirements for actuators

EN 16603-33-11 ECSS-E-ST-33-11 Space engineering - Explosive subsystems and devices

EN 16602-30-11 ECSS-Q-ST-30-11 Space product assurance - Derating – EEE components

EN 16602-40 ECSS-Q-ST-40 Space product assurance - Safety
CSG-NT-SBU-16687- Payload safety handbook
CNES Ed/Rev 01/01
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Terms, definitions and abbreviated terms
3.1 Terms from other documents

a. For the purpose of this document, the terms and definitions from ECSS-S-ST-00-01 apply, in

particular for the following terms:
1. redundancy
2. active redundancy
3. hot redundancy
4. cold redundancy
5. fault
6. fault tolerance

b. For the purpose of this document, the terms and definitions from ECSS-E-ST-33-11 apply, in

particular for the following terms:
1. no fire
2. all fire

c. For the purpose of this document, the terms and definitions from ECSS-E-ST-20-21 apply.

3.2 Abbreviated terms

For the purpose of this document, the abbreviated terms from ECSS-S-ST-00-01 and the following

apply:
Meaning
Abbreviation
assembly, integration and test
AIT
chief executive officer
CEO
Centre Spatial Guyanais
CSG
direct current
disable
DIS
electric, electro-mechanic and electronic
EEE
electro-magnetic compatibility
EMC
electro-magnetic interference
EMI
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Meaning
Abbreviation
enable
fail operational
failure mode effect analysis
FMEA
failure mode effect and criticality analysis
FMECA
field programmable logic array
FPGA
fail safe
nominal
non-explosive actuators
NEA
on-board computer
OBC
printed circuit board
PCB
power conditioning and distribution unit
PCDU
redundant
spacecraft central software
SCSW
shape memory alloy
SMA
software
telemetry
worst case
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Explanations
4.1 Explanatory note

The present handbook refers to the electrical interface requirements defined in the ECSS-E-ST-20-21.

The ECSS-E-ST-20-21 requirements are referred to in this handbook by using following convention

and are indicated in italic font:
[requirement number]
For example:
Requirement 5.2.3.2.1a.
 [Req. 5.2.3.2.1.a.]
See also, for more information, Annex A of ECSS-E-ST-20-21.
In addition:

• each requirement (i.e. any statement containing a “shall” in the standard) is marked with red text.

• each recommendation (i.e. any statement containing a “should” in the standard) is marked with

blue text.

Keywords are highlighted in bold. A keyword is a word that either has a special meaning in the

contest of the section in which it appears, or highlight a concept.
4.2 How to use this document

For the best utilisation of this document, it is recommended to print it together with the ECSS-E-ST-20-21

and to consult both of them contextually.

In this way, the discussion and the rationale explanation of each individual requirement are clearer and

there is the minimum risk of misunderstanding.
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Actuators Interface
5.1 Type of actuators

Electro-mechanic actuators of different types are used for space applications as part of hold down and

release mechanisms and deployment mechanisms.
The technologies used in electro-mechanic actuators are varied:

a. Based on pyrotechnic devices (release nuts/bolt cutter, separation nut, cutters, brazing melt,

wire cutter, cable cutter, valves),
b. Split spool devices (Fusible wire, SMA wires),
c. Solenoid actuated nuts,
d. SMA triggered release nuts,
e. SMA actuators (pin pullers and pushers),
f. Paraffin actuators (pin pullers and pushers),
g. Electro-magnetic, solenoid pin puller and pusher actuators,
h. Electromagnets, and magnetic clamps,
i. Thermal cutters and knife,
j. Piezoelectric actuators.

The actuation can be performed by provision of heat thanks to a hot head or a filament, causing

mechanical action, ignition of explosive powder, deformation of SMA or paraffin expansion, or by

direct electro-magnetic action (solenoids, electro-magnets), or by effects induced by piezo-electric

means.

Interfaces to electrical motors (for example solar array drive mechanisms, reaction wheels, and other

mechanisms) are not covered by the present handbook and standard ECSS-E-ST-20-21.

Actuators can be classified according to different criteria: from electrical point of view, they can be

classified as voltage-driven or current-driven types.

A typical example of voltage-driven actuator is a thermal knife, a typical example of current-driven

actuator is a pyro device.

Another interesting classification of actuators is according to their level of reusability, according to

Table 5-1.
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Table 5-1: Actuators reusability
NON-REUSABLE PARTIALLY REUSABLE REUSABLE
REUSABLE
(manually resettable) (self-resetting)
(need for refurbishment)
Pyro cutters Pyro nuts Solenoid actuated nuts Electro-magnetic
actuators and triggers
Initiators Fusible wire actuated SMA actuated nuts
nuts Magnetic clamps
Pyrotechnic bolt, wire Paraffin actuators
cutters and pyro- SMA direct actuators
SMA actuators
cutters
Spool based devices
Wire triggers
separation nut
Thermal cutters
Thermal cutters

The database of actuators used for the drafting of the ECSS-E-ST-20-21 is reported in Annex A.

Some figures of actuators are hereby provided.
Figure 5-1: Dassault pyro initiator
Figure 5-2: Pyro-valve (to be equipped with pyro initiators)
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Figure 5-3: Thermal knife (partially reusable – needing refurbishment)

Figure 5-4: Thermal knife activation (partially reusable – needing refurbishment)

Figure 5-5: Thermal knife (with thermal heads visible)
Figure 5-6: Glenair heavy duty HDRM (partially reusable – needing
refurbishment)
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Figure 5-7: TINI Aerospace Frangibolt (reusable – manually resettable)
Figure 5-8: NEA split-spool based HDRM (partially reusable – needing
refurbishment)
Figure 5-9: Arquimea pin-puller family
(reusable – manually resettable)
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5.2 Coverage assumptions
[Assumption 4.2a]

“This standard applies to satellites; launchers and human space applications are not included.”

For launchers and human space applications, the actuator system needs normally to be two failure

tolerant to avoid human injury, and therefore more stringent requirements are necessary to avoid

spurious actuators activation (for example, it is necessary to disconnect both hot and return line from

ground to actuators, as per [Req.5.2.2d] without alternatives as expressed in [Req.5.2.2e.1] and

[Req.5.2.2e.2]).
[Assumption 4.2b]

“According to requirement 4.4g of ECSS-E-ST-33-11 this standard covers explosive or non-

explosive actuators electronics required to comply with single fault tolerance with respect to

actuation success.”

The actuator electronics provides the requested functionality after any single failure thanks to the

provided redundancy (see [Req.5.2.2a]).
[Assumption 4.2c]

“Interfaces to electrical motors (for example solar array drive mechanisms, reaction wheels, other

mechanisms) are not covered by the present standard.”

While electrical motors can indeed be used in actuators, the complete specification of motor drive

electronics is not subject of the present standard.
[Assumption 4.2d]

“It is assumed that the two fault tolerance approach (as per ECSS-Q-ST-40 clause 6.4.2.1), with

respect to premature and unwanted actuation having catastrophic consequences, when required

according to requirement 4.4h of ECSS-E-ST-33-11, is implemented as a system (SSE and SSS)

level provision and not at equipment level. See ECSS-E-HB-20-21 section 5.5.1”

The actuator electronics covered by ECSS-E-ST-20-21 is single point failure tolerant: the coverage of

premature and unwanted actuation having catastrophic consequences is achieved by system

provisions (avoidance of mechanical interference, additional barriers like skin connectors at spacecraft

level operated during integration activities, etc.).
[Assumption 4.2e]

“Current-driven actuators covered by this standard have an inductance of 1 µH max, not

including harness.”
[Assumption 4.2f]

“Voltage-driven actuators covered by this standard have an inductance of 20 mH max.”

Current-driven actuators normally drive loads characterised by small parasitic inductance (the limit is

set to 1 µH). Normally current regulators are not well suited to drive large inductive loads, otherwise

important stability issues can arise.

Voltage-driven actuators can base their operation on electro-magnetic effects (solenoid pin puller and

pusher, electromagnets, and magnetic clamps), characterised by large inductance (the limit is set to

20 mH).
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In any case, it is necessary to limit the actuator inductance to a reasonable limit to have a chance to

procure generic actuator electronics, e.g. applicable to many actuators types without any design

change.
[Assumption 4.2g]

“The actuators electronics nominal input voltage (excluding transients) is assumed to be within a

range of 21 V to 100 V.”

This is the typical range from regulated and unregulated buses used in European satellites (28 V

regulated or unregulated, 50 V regulate or unregulated, 100 V regulated).
5.3 Actuators electronics, general architecture
5.3.1 Overview

A typical block diagram for explosive or non-explosive actuator electronics is shown in Figure 5-10.

A variant of the actuators electronics block diagram is shown in Figure 5-11.

For brevity, explosive or non-explosive actuator electronics are referred as Actuator Electronics in this

document.

Note that the diagram in Figure 5-10 or Figure 5-11 is given only as a reference, without losing

generality, and some of the features thereby reported can be actually realised differently.

Without losing in generality, the general architecture of Actuator Electronics is hereby explained in

reference to in Figure 5-10.

Actuator Electronics receive power from the Power Conversion and Distribution Electronics (either

directly from a battery or from a regulated power bus).

The power lines from the Power Conversion and Distribution Electronics can be provided or not with

over-current protection to safeguard the power bus from short-circuits or overloads generated in the

Actuator Electronics.

In case over-current protections are not provided by the Power Conversion and Distribution

Electronics, it is important that Actuator Electronics failures do not cause short circuit or overload of

input power lines [Req.5.1.2b].To this respect, the relevant harness or connector lines double insulation

is applied.

To comply with the required single failure tolerance requirement [Req.5.2.2a], the Actuator Electronics

are duplicated, with a nominal (N) and a redundant (R) side.

In Figure 5-10 explosive or non-explosive actuators are just called Actuators (for clarity, only

Actuators and power and command and telemetry lines relevant to nominal side are shown).

There are three physical barriers against spurious or untimely activation of Actuators [Req.5.2.1a],

represented in Figure 5-10 by ARM, FIRE and SELECT blocks.
The need for three barriers is explained in section 5.5.1.

In accordance with best practices, any internal conductor (for example, and referring to Figure 5-11,

disconnected hot line between ARM and SELECT switches when they are both open, or disconnected

return line between ARM switch and actuators return) is grounded to power return to avoid any

build-up of potential due to electrostatic phenomena [Req.5.2.2h].
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For clarity, redundant
actuators and relevant
lines are not shown
Actuator Electronics R
Power Conversion and Actuator Electronics N
Distribution Electronics
Selection
FIRE FIRE
i(1...n)
ARM (output) (output)
STATUS
CURRENT VOLTAGE
STATUS
2 2
N&R
M&R
N&R N&R
SELECT
Actuator 1N
Selector 1
FIRE*
ARM
Ground
Star Point
Actuator 2N
Selector 2
2 2
N&R N&R
N&R N&R
FIRE ON (FIRE
ARM EN ARM DIS
OFF)
Actuator nN
Selector n
*The FIRE actuator
might be a voltage or a
current source.
N&R N&R
Selection Selection
i(1...n) i(1...n)
EN DIS
Key: DIS = disable EN = enable N = nominal R = redundant
Figure 5-10: Typical actuators electronic block diagram
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For clarity, redundant
actuators and relevant
Electrical Actuator R lines are not shown
Electrical Actuator N
Power Conversion and
Selection
i(1...n)
Distribution Electronics FIRE FIRE
STATUS
(output) (output) ARM
CURRENT VOLTAGE STATUS
N&R
2 2
N&R N&R N&R
SELECT
Actuator 1N
Selector 1
FIRE* ARM
Ground
Star Point
Actuator 2N
Selector 2
N&R 2 N&R
N&R 2 N&R 2
FIRE ON (FIRE
ARM EN ARM DIS
OFF)
Actuator nN
Selector n
2n 2n
*The FIRE actuator is
N&R
N&R
based on a solid state
device Selection
Selection
i(1...n)
i(1...n)
DIS
Key: DIS = disable EN = enable N = nominal R = redundant
Figure 5-11: Typical actuators electronic block diagram, variant 1
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For clarity, redundant
actuators and relevant
lines are not shown
Electrical Actuator R
Power Conversion
Electrical Actuator N
Selection
FIRE FIRE
i(1...n)
(output) (output)
ARM
STATUS
STATUS CURRENT VOLTAGE
N&R N&R N&R N&R
Actuator 1N
Selection
Selector 1
ARM FIRE
Actuator*
Actuator
Ground
Star Point
Actuator 2N
Selector 2
2 2
N&R N&R N&R N&R
FIRE ON (FIRE
ARM EN ARM DIS
OFF)
Selector n
Actuator nN
2n 2n
N&R
N&R
*The FIRE actuator
Selection Selection
might be a voltage or a
i(1...n) i(1...n)
...

SLOVENSKI STANDARD
kSIST-TP FprCEN/TR 17603-20-21:2021
01-oktober-2021
Vesoljska tehnika - Smernice za električno načrtovanje in zahteve vmesnikov za
prožilnike

Space engineering - Guidelines for electrical design and interface requirements for

actuators
Raumfahrttechnik - Richtlinien für die elektrische Auslegung und
Schnittstellenanforderungen für Antriebe
Ta slovenski standard je istoveten z: FprCEN/TR 17603-20-21
ICS:
49.140 Vesoljski sistemi in operacije Space systems and
operations
kSIST-TP FprCEN/TR 17603-20-21:2021 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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kSIST-TP FprCEN/TR 17603-20-21:2021
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kSIST-TP FprCEN/TR 17603-20-21:2021
TECHNICAL REPORT
FINAL DRAFT
FprCEN/TR 17603-20-21
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
August 2021
ICS 49.140
English version
Space engineering - Guidelines for electrical design and
interface requirements for actuators
Raumfahrttechnik - Richtlinien für die elektrische
Auslegung und Schnittstellenanforderungen für
Antriebe

This draft Technical Report is submitted to CEN members for Vote. It has been drawn up by the Technical Committee

CEN/CLC/JTC 5.

CEN and CENELEC members are the national standards bodies and national electrotechnical committees of Austria, Belgium,

Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,

Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia,

Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are

aware and to provide supporting documentation.

Warning : This document is not a Technical Report. It is distributed for review and comments. It is subject to change without

notice and shall not be referred to as a Technical Report.
CEN-CENELEC Management Centre:
Rue de la Science 23, B-1040 Brussels

© 2021 CEN/CENELEC All rights of exploitation in any form and by any means Ref. No. FprCEN/TR 17603-20-21:2021 E

reserved worldwide for CEN national Members and for
CENELEC Members.
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Table of contents

Introduction ................................................................................................................ 6

1 Scope ....................................................................................................................... 7

2 References .............................................................................................................. 8

3 Terms, definitions and abbreviated terms ............................................................ 9

3.1 Terms from other documents .................................................................................... 9

3.2 Abbreviated terms..................................................................................................... 9

4 Explanations ......................................................................................................... 11

4.1 Explanatory note ..................................................................................................... 11

4.2 How to use this document ....................................................................................... 11

5 Actuators Interface ............................................................................................... 12

5.1 Type of actuators .................................................................................................... 12

5.2 Coverage assumptions ........................................................................................... 16

5.3 Actuators electronics, general architecture ............................................................. 17

5.3.1 Overview ................................................................................................... 17

5.3.2 ARM block ................................................................................................ 21

5.3.3 SELECT block ........................................................................................... 21

5.3.4 FIRE block ................................................................................................ 22

5.4 Actuators electronic, timing sequence..................................................................... 22

5.5 Actuator electronics, failure tolerance ..................................................................... 24

5.5.1 Double failure tolerance ............................................................................ 24

5.5.2 Single failure tolerance .............................................................................. 26

6 Explanation of ECSS-E-ST-20-21 Interface Requirements ................................ 27

6.1 Functional general .................................................................................................. 27

6.1.1 General ..................................................................................................... 27

6.1.2 Reliability .................................................................................................. 27

6.2 Functional source ................................................................................................... 29

6.2.1 General ..................................................................................................... 29

6.2.2 Reliability .................................................................................................. 30

6.2.3 Commands ............................................................................................... 33

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6.2.4 Telemetry .................................................................................................. 35

6.3 Functional load ....................................................................................................... 38

6.3.1 General ..................................................................................................... 38

6.3.2 Reliability .................................................................................................. 39

6.4 Performance general .............................................................................................. 39

6.4.1 General ..................................................................................................... 39

6.5 Performance source ............................................................................................... 42

6.5.1 Overview ................................................................................................... 42

6.5.2 General ..................................................................................................... 44

6.5.3 Reliability .................................................................................................. 45

6.5.4 Telemetry .................................................................................................. 46

6.5.5 Recurrent products.................................................................................... 46

6.6 Performance load ................................................................................................... 48

6.6.1 General ..................................................................................................... 48

6.6.2 Reliability .................................................................................................. 48

6.6.3 Recurrent products.................................................................................... 49

Annex A Actuators database .................................................................................. 50

Annex B Extract from CSG-NT-SBU-16687-CNES ................................................ 55

B.1 EXTRACT from CSG-NT-SBU-16687-CNES Ed/Rev 01/01 ................................... 55

Figures

Figure 5-1: Dassault pyro initiator ......................................................................................... 13

Figure 5-2: Pyro-valve (to be equipped with pyro initiators) .................................................. 13

Figure 5-3: Thermal knife (partially reusable – needing refurbishment) ................................ 14

Figure 5-4: Thermal knife activation (partially reusable – needing refurbishment)................. 14

Figure 5-5: Thermal knife (with thermal heads visible) .......................................................... 14

Figure 5-6: Glenair heavy duty HDRM (partially reusable – needing refurbishment) ............. 14

Figure 5-7: TINI Aerospace Frangibolt (reusable – manually resettable) .............................. 15

Figure 5-8: NEA split-spool based HDRM (partially reusable – needing refurbishment)........ 15

Figure 5-9: Arquimea pin-puller family (reusable – manually resettable) ............................... 15

Figure 5-10: Typical actuators electronic block diagram ....................................................... 18

Figure 5-11: Typical actuators electronic block diagram, variant 1 ........................................ 19

Figure 5-12: Typical actuators electronic block diagram, variant 2 ........................................ 20

Figure 5-13: Actuators electronics timing sequence ............................................................. 23

Figure 5-14: Actuators electronics timing sequence, different selected lines ........................ 24

Figure 6-1: Actuator electronics {V, I} characteristic ............................................................. 40

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Figure 6-2: Example - case 1................................................................................................ 40

Figure 6-3: Example - case 2................................................................................................ 41

Figure 6-4: Example - case 1 and 2 ...................................................................................... 41

Tables

Table 5-1: Actuators reusability ............................................................................................ 13

Table A-1 : Current driven, non-explosive actuators ............................................................. 51

Table A-2 : Current driven, explosive actuators .................................................................... 53

Table A-3 : Voltage driven actuators..................................................................................... 54

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European Foreword

This document (FprCEN/TR 17603-20-21:2021) has been prepared by Technical Committee

CEN/CLC/JTC 5 “Space”, the secretariat of which is held by DIN.

It is highlighted that this technical report does not contain any requirement but only collection of data

or descriptions and guidelines about how to organize and perform the work in support of EN-16602-

20.

This Technical report (FprCEN/TR 17603-20-21:2021) originates from ECSS-Q-HB-20-21A.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such

patent rights.

This document has been prepared under a mandate given to CEN by the European Commission and

the European Free Trade Association.

This document has been developed to cover specifically space systems and has therefore precedence

over any TR covering the same scope but with a wider domain of applicability (e.g.: aerospace).

This document is currently submitted to the CEN CONSULTATION.
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Introduction

The present handbook, and the relevant standard ECSS-E-ST-20-21, have been produced in a general

context to provide stable electrical interface specifications (both for the source and the load, for

functional and performance aspects).

The convergence within ECSS among agencies, of Large System Integrators and of a representative

group of electronic manufacturers on the identified requirement set can provide an effective way to

get more recurrent products for generic use, both for the actuator electronics (power source), and for

the actuators themselves, in a rather independent way from the final application.

The standard ECSS-E-ST-20-21 has therefore to be intended as a standard for product development,

and the present handbook as a guideline to understand the relevant requirements, the typical issues of

the actuators interfaces both at system and at equipment level.

This handbook complements ECSS-E-ST-20-21, and it is directed at the same time to power system

engineers, who are specifying and procuring units supplying and containing electrical actuators, to

power electronics design engineers, who are in charge of designing and verifying actuator electronics,

and to electrical actuators designers.

For the system engineers, this document explains the detailed issues of the interface and the impacts

of the requirements for the design of the actuator chain.

For design engineers, this document gives insight and understanding on the rationale of the

requirements on their designs.

It is important to notice that the best understanding of the topic of Actuators Electrical Interfaces is

achieved by the contextual reading of both the present handbook and the ECSS-E-ST-20-21.

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Scope

In general terms, the scope of the consolidation of the electrical interface requirements for electrical

actuators in the ECSS-E-ST-20-21 and the relevant explanation in the present handbook is to allow a

more recurrent approach both for actuator electronics (power source) and electrical actuators (power

load) offered by the relevant manufacturers, at the benefit of the system integrators and of the

European space agencies, thus ensuring:
 Better quality,
 Stability of performances, and
 Independence of the products from specific mission targets.

A recurrent approach enables manufacturing companies to concentrate on products and a small step

improvement approach that is the basis of a high quality industrial output.
In particular, the scope of the present handbook is:

 To explain the type of actuators, the principles of operation and the typical configuration of the

relevant actuator electronics,
 To identify important issues relevant to electrical actuators interfaces, and
 To give some explanations of the requirements set up in the ECSS-E-ST-20-21.
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References
EN Reference Reference in text Title
EN 16601-00-01 ECSS-S-ST-00-01 ECSS system - Glossary of terms
EN 16603-20-21 ECSS-E-ST-20-21 Space engineering - Electrical design and
interface requirements for actuators
EN 16603-33-11 ECSS-E-ST-33-11 Space engineering - Explosive subsystems
and devices
EN 16602-30-11 ECSS-Q-ST-30-11 Space product assurance - Derating – EEE
components
EN 16602-40 ECSS-Q-ST-40 Space product assurance - Safety
CSG-NT-SBU- Payload safety handbook
16687-CNES
Ed/Rev 01/01
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Terms, definitions and abbreviated terms
3.1 Terms from other documents

a. For the purpose of this document, the terms and definitions from ECSS-S-ST-00-01 apply, in

particular for the following terms:
1. redundancy
2. active redundancy
3. hot redundancy
4. cold redundancy
5. fault
6. fault tolerance

b. For the purpose of this document, the terms and definitions from ECSS-E-ST-33-11 apply, in

particular for the following terms:
1. no fire
2. all fire

c. For the purpose of this document, the terms and definitions from ECSS-E-ST-20-21 apply.

3.2 Abbreviated terms

For the purpose of this document, the abbreviated terms from ECSS-S-ST-00-01 and the following

apply:
Meaning
Abbreviation
assembly, integration and test
AIT
chief executive officer
CEO
Centre Spatial Guyanais
CSG
direct current
disable
DIS
electric, electro-mechanic and electronic
EEE
electro-magnetic compatibility
EMC
electro-magnetic interference
EMI
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Meaning
Abbreviation
enable
fail operational
failure mode effect analysis
FMEA
failure mode effect and criticality analysis
FMECA
field programmable logic array
FPGA
fail safe
nominal
non-explosive actuators
NEA
on-board computer
OBC
printed circuit board
PCB
power conditioning and distribution unit
PCDU
redundant
spacecraft central software
SCSW
shape memory alloy
SMA
software
telemetry
worst case
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Explanations
4.1 Explanatory note

The present handbook refers to the electrical interface requirements defined in the ECSS-E-ST-20-21.

The ECSS-E-ST-20-21 requirements are referred to in this handbook by using following convention

and are indicated in italic font:
[requirement number]
For example:
Requirement 5.2.3.2.1a.
 [Req. 5.2.3.2.1.a.]
See also, for more information, Annex A of ECSS-E-ST-20-21.
In addition:

 each requirement (i.e. any statement containing a “shall” in the standard) is marked with red text.

 each recommendation (i.e. any statement containing a “should” in the standard) is marked with

blue text.

Keywords are highlighted in bold. A keyword is a word that either has a special meaning in the

contest of the section in which it appears, or highlight a concept.
4.2 How to use this document

For the best utilisation of this document, it is recommended to print it together with the ECSS-E-ST-20-21

and to consult both of them contextually.

In this way, the discussion and the rationale explanation of each individual requirement are clearer and

there is the minimum risk of misunderstanding.
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Actuators Interface
5.1 Type of actuators

Electro-mechanic actuators of different types are used for space applications as part of hold down and

release mechanisms and deployment mechanisms.
The technologies used in electro-mechanic actuators are varied:

a. Based on pyrotechnic devices (release nuts/bolt cutter, separation nut, cutters, brazing melt,

wire cutter, cable cutter, valves),
b. Split spool devices (Fusible wire, SMA wires),
c. Solenoid actuated nuts,
d. SMA triggered release nuts,
e. SMA actuators (pin pullers and pushers),
f. Paraffin actuators (pin pullers and pushers),
g. Electro-magnetic, solenoid pin puller and pusher actuators,
h. Electromagnets, and magnetic clamps,
i. Thermal cutters and knife,
j. Piezoelectric actuators.

The actuation can be performed by provision of heat thanks to a hot head or a filament, causing

mechanical action, ignition of explosive powder, deformation of SMA or paraffin expansion, or by

direct electro-magnetic action (solenoids, electro-magnets), or by effects induced by piezo-electric

means.

Interfaces to electrical motors (for example solar array drive mechanisms, reaction wheels, and other

mechanisms) are not covered by the present handbook and standard ECSS-E-ST-20-21.

Actuators can be classified according to different criteria: from electrical point of view, they can be

classified as voltage-driven or current-driven types.

A typical example of voltage-driven actuator is a thermal knife, a typical example of current-driven

actuator is a pyro device.

Another interesting classification of actuators is according to their level of reusability, according to

Table 5-1.
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Table 5-1: Actuators reusability
NON-REUSABLE PARTIALLY REUSABLE REUSABLE
REUSABLE
(manually resettable) (self-resetting)
(need for refurbishment)
Pyro cutters Pyro nuts Solenoid actuated nuts Electro-magnetic
actuators and triggers
Initiators Fusible wire actuated SMA actuated nuts
nuts Magnetic clamps
Pyrotechnic bolt, wire Paraffin actuators
SMA direct actuators
cutters and pyro-
SMA actuators
cutters
Spool based devices
Wire triggers
separation nut
Thermal cutters
Thermal cutters

The database of actuators used for the drafting of the ECSS-E-ST-20-21 is reported in Annex A.

Some figures of actuators are hereby provided.
Figure 5-1: Dassault pyro initiator
Figure 5-2: Pyro-valve (to be equipped with pyro initiators)
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Figure 5-3: Thermal knife (partially reusable – needing refurbishment)

Figure 5-4: Thermal knife activation (partially reusable – needing refurbishment)

Figure 5-5: Thermal knife (with thermal heads visible)
Figure 5-6: Glenair heavy duty HDRM (partially reusable – needing
refurbishment)
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Figure 5-7: TINI Aerospace Frangibolt (reusable – manually resettable)
Figure 5-8: NEA split-spool based HDRM (partially reusable – needing
refurbishment)
Figure 5-9: Arquimea pin-puller family
(reusable – manually resettable)
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5.2 Coverage assumptions
[Assumption 4.2a]

“This standard applies to satellites; launchers and human space applications are not included.”

For launchers and human space applications, the actuator system needs normally to be two failure

tolerant to avoid human injury, and therefore more stringent requirements are necessary to avoid

spurious actuators activation (for example, it is necessary to disconnect both hot and return line from

ground to actuators, as per [Req.5.2.2d] without alternatives as expressed in [Req.5.2.2e.1] and

[Req.5.2.2e.2]).
[Assumption 4.2b]

“According to requirement 4.4g of ECSS-E-ST-33-11 this standard covers explosive or non-

explosive actuators electronics required to comply with single fault tolerance with respect to

actuation success.”

The actuator electronics provides the requested functionality after any single failure thanks to the

provided redundancy (see [Req.5.2.2a]).
[Assumption 4.2c]

“Interfaces to electrical motors (for example solar array drive mechanisms, reaction wheels, other

mechanisms) are not covered by the present standard.”

While electrical motors can indeed be used in actuators, the complete specification of motor drive

electronics is not subject of the present standard.
[Assumption 4.2d]

“It is assumed that the two fault tolerance approach (as per ECSS-Q-ST-40 clause 6.4.2.1), with

respect to premature and unwanted actuation having catastrophic consequences, when required

according to requirement 4.4h of ECSS-E-ST-33-11, is implemented as a system (SSE and SSS)

level provision and not at equipment level. See ECSS-E-HB-20-21 section 5.5.1”

The actuator electronics covered by ECSS-E-ST-20-21 is single point failure tolerant: the coverage of

premature and unwanted actuation having catastrophic consequences is achieved by system

provisions (avoidance of mechanical interference, additional barriers like skin connectors at spacecraft

level operated during integration activities, etc.).
[Assumption 4.2e]

“Current-driven actuators covered by this standard have an inductance of 1 µH max, not

including harness.”
[Assumption 4.2f]

“Voltage-driven actuators covered by this standard have an inductance of 20 mH max.”

Current-driven actuators normally drive loads characterised by small parasitic inductance (the limit is

set to 1 µH). Normally current regulators are not well suited to drive large inductive loads, otherwise

important stability issues can arise.

Voltage-driven actuators can base their operation on electro-magnetic effects (solenoid pin puller and

pusher, electromagnets, and magnetic clamps), characterised by large inductance (the limit is set to

20 mH).
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In any case, it is necessary to limit the actuator inductance to a reasonable limit to have a chance to

procure generic actuator electronics, e.g. applicable to many actuators types without any design

change.
[Assumption 4.2g]

“The actuators electronics nominal input voltage (excluding transients) is assumed to be within a

range of 21 V to 100 V.”

This is the typical range from regulated and unregulated buses used in European satellites (28 V

regulated or unregulated, 50 V regulate or unregulated, 100 V regulated).
5.3 Actuators electronics, general architecture
5.3.1 Overview

A typical block diagram for explosive or non-explosive actuator electronics is shown in Figure 5-10.

A variant of the actuators electronics block diagram is shown in Figure 5-11.

For brevity, explosive or non-explosive actuator electronics are referred as Actuator Electronics in this

document.

Note that the diagram in Figure 5-10 or Figure 5-11 is given only as a reference, without losing

generality, and some of the features thereby reported can be actually realised differently.

Without losing in generality, the general architecture of Actuator Electronics is hereby explained in

reference to in Figure 5-10.

Actuator Electronics receive power from the Power Conversion and Distribution Electronics (either

directly from a battery or from a regulated power bus).

The power lines from the Power Conversion and Distribution Electronics can be provided or not with

over-current protection to safeguard the power bus from short-circuits or overloads generated in the

Actuator Electronics.

In case over-current protections are not provided by the Power Conversion and Distribution

Electronics, it is important that Actuator Electronics failures do not cause short circuit or overload of

input power lines [Req.5.1.2b].To this respect, the relevant harness or connector lines double insulation

is applied.

To comply with the required single failure tolerance requirement [Req.5.2.2a], the Actuator Electronics

are duplicated, with a nominal (N) and a redundant (R) side.

In Figure 5-10 explosive or non-explosive actuators are just called Actuators (for clarity, only

Actuators and power and command and telemetry lines relevant to nominal side are shown).

There are three physical barriers against spurious or untimely activation of Actuators [Req.5.2.1a],

represented in Figure 5-10 by ARM, FIRE and SELECT blocks.
The need for three barriers is explained in section 5.5.1.

In accordance with best practices, any internal conductor (for example, and referring to Figure 5-11,

disconnected hot line between ARM and SELECT switches when they are both open, or disconnected

return line between ARM switch and actuators return) is grounded to power return to avoid any

build-up of potential due to electrostatic phenomena [Req.5.2.2h].
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For clarity, redundant
actuators and relevant
lines are not shown
Actuator Electronics R
Power Conversion and
Actuator Electronics N
Distribution Electronics
Selection
FIRE FIRE
i(1...n)
ARM (output) (output)
STATUS
CURRENT VOLTAGE
STATUS
2 2
N&R
M&R
N&R N&R
SELECT
Actuator 1N
Selector 1
FIRE*
ARM
Ground
Star Point
Actuator 2N
Selector 2
2 2
N&R N&R
N&R N&R
FIRE ON (FIRE
ARM EN ARM DIS
OFF)
Actuator nN
Selector n
*The FIRE actuator
might be a voltage or a
current source.
2n 2n
N&R N&R
Selection Selection
i(1...n) i(1...n)
EN DIS
Key: DIS = disable EN = enable N = nominal R = redundant
Figure 5-10: Typical actuators electronic block diagram
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For clarity, redundant
actuators and relevant
Electrical Actuator R lines are not shown
Electrical Actuator N
Power Conversion and Selection
i(1...n)
Distribution Electronics FIRE FIRE
STATUS
(output) (output) ARM
CURRENT VOLTAGE
STATUS
N&R
N&R N&R N&R
SELECT
Actuator 1N
Selector 1
FIRE*
ARM
Ground
Star Point
Actuator 2N
Selector 2
N&R N&R
2 N&R N&R
2 2
FIRE ON (FIRE
ARM EN ARM DIS
OFF)
Actuator nN
Selector n
*The FIRE actuator is N&R
N&R
based on a solid state
device
Selection
Selection
i(1...n)
i(1...n)
DIS
Key: DIS = disable EN = enable N = nominal R = redundant
Figure 5-11: Typical actuators electronic block diagram, variant 1
----------------------
...

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