ESA Guidance, Navigation, and Control Systems - TU Dresden · Apoaxis Orbital plane Equatorial plane. KeyNote: Dresdner Automatisierungstechnischen Kolloquien. Monday 27 th January

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ESA Guidance, Navigation, and Control Section

ESA Guidance, Navigation, and Control Systems

[email protected]

mailto:[email protected]

mailto:[email protected]

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“...Guidance, navigation and control (abbreviated GNC) is a branch of engineering dealing with the design of

systems to control the movement of space vehicles...”

http://en.wikipedia.org/wiki/Engineering

http://en.wikipedia.org/wiki/Engineering

KeyNote: Dresdner Automatisierungstechnischen Kolloquien. Monday 27th January 2014 - ESA Guidance, Navigation, and Control Systems

Acknowledgements and Agenda

About this talk, Definition, Terms, History, Acronyms

Guidance and Optimal Trajectories (G)

Navigation and Estimation (N)

Spacecraft Control (C)

Failure Detection, Isolation, and Recovery (FDIR)

Mission Vehicle Management (MVM)

Examples of GNC Systems:

Earth Orbiting Spacecraft

Entry, Descent, and Landing

Rendezvous and Formation Flying

Interplanetary Space Vehicles

Launchers

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Dresdner Automatisierungstechnischen

Kolloquien

Gez. Prof. Dr. techn.

Klaus Janschek

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About this talk, Definition, Terms, History, Acronyms,...


About the speaker

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Dr. Guillermo Ortega is the Head of the Guidance, Navigation and Control Section of ESA

Space engineering activities in the GNC area in ESA

Design and implement GNC systems for space vehicles including: interplanetary cruise, aero assistance, precision landing, ascent, rendezvous and docking, re-entry, formation flying and drag- free systems

Implementation of the ESA policy and requirements in the GNC area including standardisation, and overall technology planning and development


Definitions

GUIDANCE: establishment of the desired path to follow (current, i.e. in real-time and future)NAVIGATION: establishment of the current and future stateCONTROL: actions to match the current state (navigation) with the foreseen path (guidance)

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http://www.ecss.nl

http://www.ecss.nl

http://www.ecss.nl


Problem description: Position

Want to “move” a space vehicle from point “A” to point “B”

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Pt Touch-down

Pd De-orbiting

Landing

Entry and Descent

Depart from ISS


Problem description: Attitude

Want to “slew” the axis of a space vehicle from axis “A” to axis “B”

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satellite

yaw

roll

pitch

X

Y

Z

orbit

object ofinterest

line

of s

ight

time

follow-onmaneuver

change ofobjectivemaneuver


Simplified GNC block diagram

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S/CKINEMATICS

ATTITUDECONTROL

NAVIGATION

MissionData (guidance)

StabilizationData (guidance)

SENSORS

POSITIONCONTROL

Noise

Noise

Positions,Velocities,

Accelerations

Roll φ,Yaw ψ,Pitch ϕ

Fck

Tca

SENSORS

S/CDYNAMICS


GNC elements

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Star tracker

Gyro

Sun sensor

Infra-red sensor

Solar panel flaps

ThrustersWheels

Guidance, Navigation, and Control

Spacecraft Dynamics and Kinematics


MVM functional diagram

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Mission Vehicle Management (MVM)

Guidance, Navigation, and Control (GNC)

Failure, Detection, Isolation, and Recovery (FDIR)

Heath Monitoring (HM)

Guidance (G) Navigation (N) Control (C)


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Guidance and Optimal Trajectories


Definitions

“...GUIDANCE is the determination of the desired path of travel (trajectory) from the vehicle's current location to a designated target, as well as desired changes in velocity, rotation and acceleration for following that path..”“...Astrodynamics is the application of celestial mechanics to the practical problems concerning the motion of planetary bodies and spacecraft...”“...Celestial mechanics is the branch of astronomy that deals with the motions of celestial objects...”“...TRAJECTORY is the path of a vehicle in space...”

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http://en.wikipedia.org/wiki/Targeting

http://en.wikipedia.org/wiki/Targeting

http://en.wikipedia.org/wiki/Celestial_mechanics




http://en.wikipedia.org/wiki/Spacecraft

http://en.wikipedia.org/wiki/Spacecraft


Guidance Engineer Work Profile

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AscentEntry

Interplanetary

Rendezvous

Loitering

Mission ArcsDisciplines

Technologies

Propulsion

Aerodynamics

Structures

Systems Optimization

MathematicalmodelingSoftware design and

development

Informatics skills


Johannes Kepler “3 laws” -> Year 1609

“...The orbit of every planet is an ellipse with the sun at a focus...”“...A line joining a planet and the Sun sweeps out equal areas during equal intervals of time...”“...The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit...”

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Isaac Newton “3 laws” -> Year 1687

“...An object at rest tends to stay at rest and that an object in uniform motion tends to stay in uniform motion unless acted upon by a net external force...”“...An applied force on an object equals the rate of change of its momentum with time...”“...For every action there is an equal and opposite reaction...”

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Albert Einstein “3 principles” -> Year 1905

“...The speed of light in the vacuum is always the same...”“...Energy is equivalent to matter...”“...The continuos space-time is curved by matter and energy...”

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Orbital Geometry and Classic Elements

Semimajor axis (a): distance between the geometric center of the orbital ellipse with the periapsis (point of closest approach to the central body), passing through the focal

Eccentricity (e): shape of the ellipse, describing how flattened it is

Inclination (i): tilt of the ellipse with respect to the reference plane, measured at the ascending node

Longitude of the ascending node (Ω): horizontally orients the ascending node of the ellipse with respect to the reference frame

Argument of periapsis (ω): defines the orientation of the ellipse in the orbital plane, as an angle measured from the ascending node to the semimajor axis

True anomaly at epoch (ν): defines the position of the orbiting body along the ellipse at a specific time

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Orbital Elements

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νω

Ωi

Ascending node

Vernal Equinox

ApoaxisOrbital plane

Equatorial plane


Foundations of Trajectory Optimization

Is the process of designing a trajectory that minimizes or maximizes some measure of performance within prescribed constraint boundaries

Boundary conditions: initial conditions (launch pad), target orbit, return of rocket stages, staging conditions, visibility of ground stations, ....

Path constraints: max. dynamic pressure, max. heat load, bending moment, max. acceleration, constraints on flight path...

Performance Indices/Cost Functions: maximize payload, minimize fuel consumption, minimize cost ...

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Navigation and Estimation


Definition

NAVIGATION is the process to find the present and future position and orbit of a spacecraft using a series of measurements

Step 1: MEASURING

Obtaining state vectors (x, y, z, Vx, Vy, Vz,...) at timely intervals

Step 2: DETERMINING

Reconstructing the orbit based on a set of state vectors

Step 3: PREDICTING

Forecasting the imminent future state vector

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Measurements taken

Now

Measures interval

Orbit set computation

Now

Measures interval

Orbit set prediction

Now

Measures interval

Prediction


Sensors: Optical

Star tracker

Provides precise 3-axis inertial attitude 10” from Lost in Space (star pattern recognition)

Orbital position required for Earth pointing

New generation: APS (CMOS) instead of CCD

Earth sensor

Provides 2-axis attitude w.r.t. Earth

Third axis = sun sensor or gyroscoping stiffness

0.03 deg GEO (radiance sensitivity)

Scanning or static

Sun sensor

Provides 2-axis attitude w.r.t. Sun

Either coarse analogue (acquisition) or fine digital

Navigation camera

Celestial body imaging and navigation algorithms

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Scanning infra-red Earth sensor

2-axis Digital Sun sensor

Autonomous CCD-Star Tracker


Sensors: Inertial, Magnetic

Magnetometer

Provides (coarse) magnetic field measurement

Light and cheap sensor for acquisition in LEO

Integrating gyros

Provides integrated angular rate

High bandwidth and accuracy (but drift error)

Possible hybrid with optical sensor (Kalman filter)

Accelerometer

Stand-alone or within IMU

No space qualified European sensor

Coarse rate sensors

Provides angular rate <10 deg/h accuracy

Light and cheap sensor for de-tumble, acquisition, short term attitude propagation

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3-axis MEMS rate sensor

4-axis Fiber Optic Gyroscope

3-axis magnetometer AMR


Estimation Techniques

Deterministic

Kalman-like estimation: Extended Kalman (EKF), Unscented Kalman (UKF), Ensemble Kalman (EnKF)

Wiener estimator (WE)

Particle filter estimators (PF)

Method of moments (MoM)

Minimum-variance unbiased estimator (MVUE)

Stochastic

Maximum likelihood estimators (ML)

Bayes estimator (BE)

Minimum mean squared error estimator (MMSE)

Maximum a posteriori estimation (MPE)

Markov chain Monte Carlo (MCMC)

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Spacecraft Control


Objectives of advanced control techniques at ESA

Ob1) Minimize the spacecraft propellant mass or overall mass, hence reducing mission costOb2) Increase the accuracy of the control when tracking or regulating the plantOb3) Increase the agility of the spacecraft maneuversOb4) Facilitate the overall design process of the GNC subsystem, hence reducing mission cost

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KeyNote: Dresdner Automatisierungstechnischen Kolloquien. Monday 27th January 2014 - ESA Guidance, Navigation, and Control Systems 28

Attitude control

Z

X

Y

yaw: ψ

roll: φ

Pitch: θ

α +α −LOS

α +

α −LOS

Thruster 1

Thruster 2


Spacecraft Pointing Control

Tdist

θrealθref.

Controllaw

Satelliteplant

Sensor

Noise

+

-

e

+Y

+Z

+X

θ

ψ

φ

Pitch

Yaw

Roll


Broad Control System Categories

ControlSystems

Regulators

TrackingSystems

Inputs

DisturbancesPlant

variations

Noise

Outputs

Preliminary Design Criterion: Desired RAISING TIME

Preliminary Design Criterion: Desired TRANSIENT RESPONSE

Disturbances

Plantvariations

Inputs

Outputs(Constant)

Noise

Moving Plant Poles to the

desired location


Actuators:

Reaction Wheels

Momentum capacity 10-40 Nms, Torque up to 0.1Nm (momentum exchange)

Off-loading needs, microvibration issues

Control Momentum Gyroscopes

Gyroscopic Torque: 5 to 45 Nm, provide satellite agility

Propulsion

High to low external torque capacity, used for orbit control and initial acquisition

Efficiency Isp(s): Δm.g Isp = F.Δt = Msat.ΔV

Types:

Cold gas, hydrazine, bi-liquid

Electric propulsion (high Isp, low thrust)

Magnetic torquer

Interaction with Earth magnetic field T= M x B

LEO: acquisition/safe mode and RW off-loading w/o orbit perturbation (no force)

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12 Nms Reaction wheel

400N main engine

Magnetic torquer

CMG


Disturbances

Disturbing torques strongly impact AOCS design

Minimized by Platform design trade-offs

Orbit and Platform configuration dependent:

Aerodynamic torque/force: LEO k.exp(-altitude), (typically mNm at 600km (Solar Array) or align with velocity)

Gravity gradient torque: LEO (GEO) 1/R3 (typically mNm at 600 km or get principal axis towards Earth)

Magnetic torque: LEO (GEO) 1/R3 (typically 10 μNm with small residual magnetic momentum)

Solar pressure torque/force: GEO (LEO) constant (typ. 10 μNm in GEO with 2 symmetrical Solar Arrays then 50 Nms wheel can provide gyroscopic stiffness)

Generated by the Satellite:

Micro-vibrations

Propellant sloshing

Orbit control thrusters: typically 1Nm

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Advanced Control Techniques classified

Multivariable Linear-Time-Invariant systemsH-infinity, Structured Singular Value (SSV), Quantitative Feedback Theory (QFT), Model-Based Predictive Control (MPC), Linear Parameter Varying (LPV)

Multivariable Non-Linear systemsNon-Linear Dynamics Inversion (NDI), Feedback Linearization (FL), Sliding Mode Control (SMC), Numerical Optimization (NO), Fuzzy Logic Control and Neural Networks Control

Control of Distributed Parameters SystemsHuman Control Systems

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Failure Detection, Isolation, and Recovery


FDIR

Different levels of complexity:

Compromise between mission continuation and spacecraft safety

Ensure smooth automatic reconfiguration in case of H/W anomaly

Ultimately go to Sun pointing Safe Mode (mission outage but S/C safety)

Implement or not independent sensors to monitor critical operations, in addition to the sensors and actuators in the loop

Redundancy

Branch A and branch B or single string

Cross strapping between units to combine A and B units

At unit level, or only electronics

example: 4 Reaction Wheels in a skewed configuration

3 out of 4: 3 RW’s being sufficient for 3-axis torque generation

False alarm risks

tuning of the monitoring threshold and time constant to avoid false alarm

Reliability

Compute probability of success over the required lifetime, based on H/W units MTBF (Mean Time Between Failure)

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Caution and Warning

Performance factors to taken into account: controllability, stability, algorithm speed, computational loads, etc

Predefined yellow (caution) and red tubes (warning) around the nominal path have been established to mean the controllability of the system around the pre-established optimal trajectory.

In general, the FDIR system strategies shall be robust to the flight conditions at specific Mach numbers and dynamic pressures chosen by the control engineer along the complete flight path

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Caution tube

Warning tubeNominal trajectory

Real trajectory

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Mission Vehicle Management


Role of GNC analyst in a space project

Identify relevant requirements, needs, and constraintsTrade-off alternative mission scenarios to fulfill requirementsAnalyze system budgetsDefine a mission conceptSketch a mission time-lineShare results and produce report

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Space Project Phases

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Production-ground qualification testing

Detailed definition

Utilization

Disposal

ECSS-E-10 http://www.ecss.nl

B C E FD0 A

Mission needs identification

Feasibility

Preliminary definition

http://www.ecss.nl

http://www.ecss.nl


Spacecraft MVM Life Cycle (zoomed)

Mission requirementsand performances

Orbit design,Equipment design,

Modes design

Analysis: Time & Frequency

domains and stability

Interactive simulations & animations forperformance verification

Control laws generationModes transitionFailure recovery

Computer code generation

Testing on

ground

Real processing on flight

MV

MD

esig

n

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Earth Orbiting Spacecraft


Telecommunications

~0.12° for absolute pointing (half cone, at antenna level)

minimization of mission outage (back up modes before safe mode)

Large solar arrays (flexible modes 0.01 Hz), transfer GTO to GEO

Long lifetime (typ. 15 years) and harsh environment (radiations)

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Mission Orbit type

Artemis Geostationary

SMART-OLEV Geostationary

EDRS Geostationary


Scientific satellites

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AOCS

Fine Sun sensor 16 Thrusters

2 Sun acquisition sensors

3-axis rate gyros 4 Control wheels

Star tracker

Quadrant star sensor

Earth limb sensor

1.000 Km

70.000 Km

Mission Orbit type

XMM Highly elliptical

INTEGRAL Highly elliptical

from 0.1° to <1 milliarcsec for absolute pointingCutting edge missions with very specific requirementsinstrument as AOCS sensorVariety of orbits: LEO, GEO, Lagrange point L2


Observing the Earth

from 0.1° to 0.01° for absolute pointing

Angular rate stability for image acquisition: typical 0.001 °/s, agility

on-ground post-processing (image rectification and localization)

LEO: eclipse and intermittent link with Control Centre

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Mission Orbit type

Cryosat Highly elliptical

Aeolus Circular, Sun Synchornous

Goce Circular

Sentinel Circular


Navigation

~0.2° for absolute pointing Yaw steering due to non sun synchronous orbitMEO: high level of radiations

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Mission Orbit type

Galileo Constellation, circular

EGNOS Geostationary

EDRS Geostationary


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Entry, Descent, and Landing


EDL Missions and GNC

Type of entry:Ballistic:

Normally spin stabilized to keep desired attitudeNo active control (no thrusters)

ControlledUsing thrusters and/or aero-dynamics surfaces

GNC design based on mission features, constraints, and requirements

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ARD (ESA)

Huygens (ESA)

IXV (ESA)

X-38 (ESA and NASA)


EDL Mission Sequence and Problem Description

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Entry

Descent

Landing

Entry gate

Landing point

TAEM

De-orbitInitial boundary constraints

Final boundary constraints

Path constraints

Path constraints

Marsenvironment conditions

Vehicle features


Definitions

Trajectory optimization of entry trajectories

Ballistic or controlled

Foot prints and landing ellipses

Equilibrium glide

Path constraints and boundary constraints

maximum dynamic pressure

maximum heat-flux

maximum acceleration

angle of attack (Mach-dependent)

control reserve (equilibrium glide)

Performance indices:

minimum heat-load

maximum safety

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Crew Rescue Vehicle

Development of the control laws for automatic re-entry vehicle type CRV

trajectory control

attitude control

Control target

Easy control in all possible regions of the flight

Cut-down cost for GNC adjustment to new lading sites

GNC

GPS SPS or PPS Thruster activation

Parachute controls

3-axis accelerometer

3-axis rate gyro

Flaps, rudder deflections

FADS

Alt.

Time

120 Km

10 Km

90 Km

30 Km

Parachute deployment3 Km

Roll maneuver

400 s 1600 s800 s

End of RCS; start rudder

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Rendezvous and Formation Flying


Rendezvous Missions and GNC

Designed to approach two spacecraft and mate them

Circular or elliptical rendezvous

Circular rendezvous governed by the Clohessy-Wiltshire equations. Elliptical much difficult

Uses a special coordinate system: Local Vertical Local Horizontal

Need a high accurate sensing suite

Need spacial propulsion systems to accurate position and slew the vehicle

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HTV (JAXA)

Progress (Rosscosmos)

ATV (ESA)


Automatic Transfer Vehicle

Development of the control laws for automatic rendezvous and docking of servicing vehicles:

trajectory controlattitude control

Control targetSoft docking and structural latching operationsMore performance in the follow-up of the target docking port of the station

Flight Direction

S0S1

7000 m

2000 m

V-bar

R-bar

ISS docking port target

Local Vertical Local Horizontal coordinate

system


Comparisons: ATV, Progress, Apollo

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ATV rendezvous with ISS

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Flight Direction

S0S1

S2S3S4

ATV

6000 m

2000 m

V-bar

R-bar

ISS docking port target

Local Vertical Local

Horizontal coordinate

system

S52500 m500 m

[-20000 m, 0 m, 10000 m]


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Interplanetary Space Vehicles


Interplanetary Vehicles and GNC

Fly-by between planets

Mid-course correction maneuvers

Optimal pointing of antennae to ground stations

Station keeping in Lagrangian points

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Venus Express

Mars Express

Rosetta


Missions Examples

High pointing accuracy on attitude stabilization

Agility on attitude slew

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Mission Orbit type

ExoMars Ascent, loitering, interplanetary, entry

Mars Sample Return

Ascent, loitering, interplanetary, entry,

rendezvous

Moon Lander


rendezvous

Human Mission to Mars


rendezvous


Missions Examples

Very high accuracy in terms of attitude stabilization and control (case of LISA)

Hard survival environment for vehicles very closed to the Sun (case of SOLO)

Very long periods of trip and quick and frequent maneuvers coupling attitude and trajectory

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Launchers


GNC for launchers

Trajectory optimization of nominal ascent trajectories

Performance maps of rockets

Optimization of non-nominal trajectories: missionization

Nominal Splash down of stages

Stages fragmentation analysis and splash down locations

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Mission

Ariane-5

Soyuz

Vega

Heavy Lift Launcher

Impact Z9

Impact Z23Impact P80


ESA rocket family

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GNC of a Small Rocket

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Problems in Space EngineeringESA UNCLASSIFIED – For Official Use

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Thank you for your attention

esa.int

Documents

ESA Guidance, Navigation, and Control Systems - TU Dresden · Apoaxis Orbital plane Equatorial plane. KeyNote: Dresdner Automatisierungstechnischen Kolloquien. Monday 27 th January