Luận văn summary of doctoral thesis on control and automation engineering attitude estimation for small earth observation satellite by fusion of gyroscope sensor and star tracker

GRADUATE UNIVERSITY OF SCIENCE AND TECTINOLOGY NGO DUY TAN ATTITUDE ESTIMATION FOR SMALL EARTH OBSERVATION SATELLITE BY FUSION OF GYROSCOPE SENSOR AND STAR TRACKER Major: Control and

GRADUATE UNIVERSITY OF SCIENCE AND TECTINOLOGY

NGO DUY TAN

ATTITUDE ESTIMATION FOR SMALL EARTH

OBSERVATION SATELLITE BY FUSION OF GYROSCOPE SENSOR AND STAR TRACKER

Major: Control and Automation Engineering

Code: 62 52 02 16

SUMMARY OF DOCTQORAL THESIS

ON CONTROL AND AUTOMATION ENGINEERING

Hanoi — 2018

Supervisor 1: Asoc Prof.Dr Thai Quang, Vinh

Supervisor 2: Dr Bui ‘Trong ‘Tuyen,

Reviewer |:

Reviewer 2:

Reviewer 3:

The thesis is defended to the thesis committee for the Doctoral Degree,

at Graduate University of Science and Technology —

on Date Month Year 2018

Hardcopy of the thesis can be found at:

+ Library of Graduale University of Science and ‘Technology

- National Library of Vietnam,

LIST OF AUTLIOR’S WORKS

Eng dodn tw thé vé tink quan sit Trải di bang phuong phép hop

nhất dữ lê đa cảm biển, KÝ yêu TIội thảo khoa hoe “Neghién ct

phát triển vả ứng đụng công nghệ vũ trụ - 2011”, Viện Công, nghệ

vũtrp, 2011

-np nhất dữ liệu cảm biên tốc độ quay và câm hiển sao đễ dự đoán

ân thể tệ từủi nhá, Ký yêu TIội tháo quốc gia lần th XV: Một số

yên để chọn lọc của Công nghệ thông tin và Iruyên thông- Hà Nội, 93-04/12/2012

Xác định từ thế bằng bộ kễ! hợp cảm biến xao và can quay hỗi

chuyền trên vệ tình VNREDSai-T, Kỷ yêu Hội thảo Công nghé vii

trụ và Ủng dụng — Hà Nội, I9/12/2014

“Hiệu chỉnh quỹ đạo cho về tính nhỗ quan sát Trái đất trên quỹ dạo

đồng bộ Mi trời, Kỷ yêu Hội thảo Công nghệ vũ tru và Ứng dựng

Hà Nội, 19/12/2014

Small savellite attitude determination by gyroscape and star tracker fusion, Intemational Conference on Information and Convergence Technology for Smart Society - To Citi Minh, 1/2016 A.New Approach for Small Saiellite Gyroscope and Star Tracker Fusion, Indian Jonrral of Science and Technology, Volume 9, Jesue 17, 5/2016 (tạp chỉ thuộc danh mục SCODPU S)

Xúc định quỹ đạo về tình viễn thản phù hơp vii didu kiên Viet Nam,

‘Lap chi Khoa hos do dac va ban dé, số 34-12/20 17,

Proposed design of a fault-tolerance attitude estimator for small earth observation satellite, Inlemational Journal of Mechanical Engineering & Technology (IMMET), Volume 9, Issue 1, 1/2018 (tap chí thuộc đanh mục SCOPUS)

Study an the needs and proposal for high and very bigh resolution

satellite remote sensing spstems in Viet Nant, international Jounal

of Civil Engineering & Technology (CIE), Volume 9, Issue 1, 1/2018 (tap chí thuộc danh mnr SCOPUS)

FOREWORD

Data from satellite attitude sensors (orientation sensoxs, angular

rate sensors) needs to be merged together to produce a reliable ontput provided Lo the controller, ‘Tins is Lhe key task of the gatelhte allude

estimator

Some challenges and contrainte are:

+ Conlraint in power supply

- Processing, capability: on-board tasks are mainly implemented on FPGA (Field Gate programmable array) or SoC (System on Chip) + Impacls by space environment and radiation: these are Lypical charateristes which determine the design and on-board part

selections

- Ground-satellite communication penod: limited duration for

contact between satellite and ground control stations

- Real-time

+ Complexily in transformation of courdmale systems

Algorithms for attitude estimation arc nounally hardware implemented So this is the key consideration to select compact and raliable solutions

Solutions for altitude estimation shall mect the following

+ Optimality in performance and on-board rcsơurces (power supply, anemory aid processing capability),

‘Therefore, study and proposal of adaptive estimation algorithms

ae major fields of research in salellile Icchmology The implementation of the algorithms shall consider the stability and

compaciess in order to keep optimal with on-board limited resources

So adapuve mechanism shall be simple bul optimal in compulation And fuzzy logic is of suitable for adaptive approaches

Based on the above analysys the anthor chose the topic of the

thesis “AUttude estimation for small Karih observation satcliilc by fusion of gyroscope sensor aud star tracker”

OBJECTIVE GF THE TLUESIS

The thesis focus on: study and proposal of an attitude methods by

fusion of measurement ftom gyroscope sensor and star tracker for

small Earth obzcrvation satcllite which can meet Ihe on-board

contraints and space environments.

CHAPTER L-

TRODUCTION 1.1 Sulellite attitude

‘The term “satediite attitude” refers ta the orientaiton of a satellite

in a fixed coordiate system and its angular rates around the couespomding, axis A satellite operation on-board shall meet the

requirements in its onentation such as antenna pointing to ground

slaion, solar panel orientation and carth pointing for imaging

In order to be able to estimate and control the attitude of the

satellite with programmed tasks, the attintde determination and control

subsystem (ADCS) anust be provided with accurate and reliable data from a various types of sensors such as: sm sensor, star tracker,

angular rate sensor, magnetic field sensor It should be noted that each

ype of sensor has many different fealures such as sapling male, accuracy reliability and dependency on current position of the

sarellite Therefore: Multi senser data fusion is the process of

combining mneaswements from different sensors (o produce betler

results than using, individual ones

1.2 Coordianate systems in Investigation of satellite motion

In order to analyze satellite motion, coordinate system shall be

specified The coordinale syslems include inertial 3,, orbital 3, and satellite body 5, coordinates In the scope of this dissertation, it is assumed thal the salellile is a cixcular earth rolaling rigid body

1.3 Aldtude representation

Altitude representations are:

> Direct Cusine Malrix (DCM)

6

Roll, Pitch, Yaw (RPY)

Enller angles and rotation

Quaternion

Modified Rodrigues Parameters (MRP)

Pivol parameters (latest proposal for satellite attitude

and xịt ] is real attitude

Thanks to its advantages, quaternion is still the most popular

allilude representation for small salellile

14 Key crileria for ulliiude determination aud control

subsystem

Key caiteria for ADCS are:

= Attitude accuracy parameters include attitude estimation and

attitude control accuracies:

© Pointing accuracy: difference inxeal and desired altitude in each

3

axis: (6, —8

© Eslimation accuracy: difference in estimaled and real altitude:

Attitude control error places a significant impacts on the

imaging accuracy ơn the groutd and image qualily as well So the acuracies shall te key eritera for Earth obervation missions

1S Attitude estimation algorithms and on-board contraints

‘The altitude estimation uses measurements from gyroscope and slat (racker, Therefore, in order lo design an effective and practical estimator which is adaptive and ffanlt-tolerant, each sensor characteristics and its impacts should be carefully smdied The following cases shall be considered:

- Angular rate sensor: impacts of drift and faulty sensor

- Star tracker: impacts of noise and data unavailability (due to big bright objects)

One the the key feature/contraint of the estimator is optimal design for hardware impleinentation which is of limited processing capacity

It is pointed out by some researches that Kalman filters especially Extended kalman Filter (KI) is showing significant advantages over tradiliowal approaches such as TRIAD or QUEST in term of hardware implementation Adaptive methods are applicable in the conditions of the fluctuational satellite's parameters or fanlty sensors However, due

to the specific in-orbit zequirements of rdliability, accuracy, and and constraint of limited computing resources, adaptive methods have not yet been widely applied

In control systems, fizzy logic is popular far adkive mechanism

It is chosen thanks to the following features:

- Filexibility and comprehensibility

CIAPTER TY SATELLITE MODEL AND SENSORS TN TITE,

ATTITUDE ESTIMATION PROBLEMS 2.1 Satellite model attitude control with reaction wheel

241 Satellite model with reaction wheel as actuator

Salellile model is described as below:

Neis commaned torque

Tzis satellite inertial matrix

If the scalar par q: is separated, the remained forms a Gibbs

Commanded torque: u=N., hen stale equation of the satellite is

Hie) Aix) Du (t)Nelé} + Bat]Naszy£)

24.2 Control taw for attinde contrat

Vor esase of design and simulation, the control Jaw is selected as

“Where: qe, qcis the current and required attitneds respectively

coeand «, if the current and required angular rates

In the mode of Earth pointing, the ADCS is lo control and maintain the body angular sate in pitch axis as given below

10

‘Where 7: isthc Banh rotation period

In case of Sun synchronous orbit, 7, is around 90 minntes

In imaging mode, Lhe salellile alfilude is following a programmed manner (the required attitude can be calculated on-board or uploaded from ground control station)

‘The satellite madel is linearized around earth pointing angular rate: [O, -m, 0]

20 Axtt}+ BN O+BN,,

‘Where: x(t) is the state matrix and defined as | qh

his the angular momentum of the reaction wheelsN, Ine yéu cin

Nast ig external disturbance forces

A, B are state matrices

Where: ä is the messưed angular rate, pis Ue Hme-

dependant drift and n,, „ụ are Gaussiơn white noise processes

11

222 Star tracker

Star tracker is ant optical device functioning to determine sarellite attitude by precise imaging of stars The captured image is then compared (o Lhe slar map in order Lo calculate (he cuzrent altitude, AAalar tracker is modelled as

4.=484

Where

4.8 the cutput quaterion of the sensor,

is (he actual allilude,

#yis (he sensor noise:

CHAPTER III - ATTITUDE ESTIMATION BY MULTI

SENSOR FUSION

Atiude demermination is considered as optimal estimation solution based on multiple sources of sensors The estimation algorilian must evaluale the reliabilily of cach sensor which is Lhe

scusor confidence factor

Some popular estimations methods are

Weighted function

Lxtended Kalman Filter (EK)

Qualernion Estimation (QUEST)

Pivot based method

cm-board satellites shows several disadvantages such as more memory

utilization, computational burden and higher power consumption These are also constraints which mst be balanced to ensure the real

time operation of the satellite

Summary: In this chapter, the attitude estimation model for small

Earth observation satellite has been described And the estimator by

Kalam Giller has been shown as well ‘The model is the background for applying adaptive nicchanism to improve the fault-tolerance of the

estimator and the ADCS in general

CHAPTFRIV PROPOSAL OF A ESTIMATION METHOD W1TH GYROSCOPE DRIFI-COMPENSATION

41 Design of a drift-compensated estimator

The state vector is chosen as’

Where: q fq: q: qr qi] ie reel attitnde B [Pr By B.] is the dift

vector of the gyroscope

13

EKF for attitude cstimator is illustrated below:

woe Init PÄ)P,

R-ñ Baa

Tạ, x FRE 40,000

Ky = PH ag EO) PT +R, ` Gains

- Angular random walk (ARW): 0.15% Ji

- arth pointing rate: 2° rad/s (Satellite obital period: T=90

minutes)

= Required angular rate: [-0.0036 -0.0074 0.0032] zd’s

- Imaging period: ‘101200 to To 1300 (second)

~_ Extemaltorgue: z=[0 0 0];

- Initial condition: x=[1 0 0 0 00 0]:

Control law: PID

- Desired atttitude: roll manouver by an angle of 30°

4.2.1 Simutation result by weighted method

“Axisifactor Roll (rad) Piteh (rad) ‘Yaw (rad) Mean 00003805 00007924 00005978

42.2 Simulation results of EKF attitude estimator by gyro drift

compensation

Figure 0,3 Estimated attitude (Roll, Fitch, Figure 0.4 Pointing errors

Yaw) Performances of the estimator are:

AxisParameter ‘Roll (rad) Piteh (rad) | Yaw (rad)

Mean “481 &05 Tae eds [ 416605 Std deviation 00001515 00001493 | 00001348

Summary: The results show that kalman filter is fully capable of reliable attitude estimator

CHAPTER V - PROPOSAL OF A FAULT-TOLERANCE

ATTITUDE ESTIMATOR FOR SMALL EARTH

OBSERVATION SATELLITE S11 Design of a Kalman filter for multi-sensor data fusion for attitude estimation

A Gyro-stellar estimator (GSE) operation is described by the following steps:

16

5.2 Application of fuzzy logic for tuning the estimator

The fuzzy tuning mechanism is proposed to monitor and adjust the filter coefficienls Q,and Tụ:

_

sen 40)

Where a >-1is the tuning factor, if q =1the estimator 1s a

pwe EKF, g,.R, ale constant matzices

Fuzzy based algorithm is developed with two inputs of meaud

and deviation values of the innovation Tunning factor a is the

17

+ Ifthe gyrorcope is working nomnally: gyro measurcments are used

to estimate the attitude

+ If the pyroscope is degraded: reference angular rates are used instead of gyro measurements If lhe dar tracker measurements are also interrupted for longer than the designed thresholds (due

ta charged particle, big, bright objects ) the gyro measurement shall be used

= Ifthe gyroscope is faulty: reference angular rates are used instead

of pyro measurements If the star tracker measurements are also

18

interrupted for longer than the designed thresholds, the dynamics

eugation is integrated for attitude estimation

Angular random walk (ARW); 0.15% yh

Earth pointing angular rate: 2*pi/(90*60) rad/s (T,=90