satellite attitude control system design using reaction...

Aerospace Power & Electronics Simulation Workshop 2004

• Satellite Attitude Control System Design Using Reaction Wheels

Bhanu Gouda Brian FastDan Simon

2Aerospace Power & Electronics Simulation Workshop 2004

Outline

1. Overview of Attitude Determination and Control system

2. Problem formulation

3. Control schemes

3.1 Modified PI Controller

3.2 Active Disturbance Rejection Control

4. Conclusion


ADCS

•ADCS: Attitude Determination and Control subsystem

•Attitude Determination -Using sensors

•Attitude Control - Using actuators


Disturbance torques

• Aerodynamic• Gravity gradient• Magnetic• Solar radiation• Micrometeorites


Attitude control modes•Orbit insertion

•Acquisition

•Slew

•Contingency or Safe


Spacecraft control type

• Passive control - Gravity gradient control- Spin control


Spacecraft control type

• Active control (Actuators)- Reaction wheels- Momentum wheels- Control - moment gyros- Magnetic torquers

- Gas Jets or Thrusters


Tetrahedron configuration of Reaction wheels


Outline



3. Control schemes



4. Conclusion


Problem formulation


Mathematical model

[ ]122111 2

1 wmdmrwIH −

+==

[ ]222222 2

1 wmdmrwIH

+==

Angular momentum of each disk

Moment with respect to the space craft

( ) ••••+= θθ 22 2MdMrI

M = Mass of the space craft

mi = mass of the reaction wheel

wi= angular velocity of the wheel

θ = Angular position of space craft

r = radius of the wheel

I= moment of inertia


Conservation of angular momentum

Mathematical model

( ) ( ) ( ) ••+=

++−

+ θ22

222

122 2

21

21 MdMrwmdmrwmdmr

dtd

( )••

=+− θ..221 mMww

dtd

[ ]••

=+ θIHHdtd

21

( ) cmMww +=+− •

θ2

21


Outline



3. Control schemes



4. Conclusion


Control Scheme

Two types of controllers are investigated- Modified PI Controller- Active Disturbance Rejection Controller


Simplorer

• Simplorer• Circuit element

models• Electric machine

models• Data analysis tools• Interfaces with

Matlab / Simulink


Outline



3. Control schemes



4. Conclusion


• This controller is used as the baseline controller• Only one tuning parameter • Generalized 2 DOF control structure is proposed

Modified PI Controller

Reference: A Robust Two-Degree-of-Freedom Control Design Technique and its Practical Application-Robert Miklosovic, Zhiqiang Gao


kis-1 Plant transfer function

kp

actcc

actdesactpi

actdes Sk

Sk θωωθθθθθ ..2).(.).(

2

−−=−−

actθdesθ


Motion profiling

•The desired trajectories as the command input in the closed loop control

•In this case, a profile generator is used to produce desired angle to the system

•Motion profile is used instead of step.


w2

GAIN GAIN

SUM5

GAIN

w1

w2

theta

theta_dot

Disturbanc

error in theta

Theta Actual

control signal

w1

t_des_de deg_rad

theta_dot_de

RANDOM

Random_Nois

GAIN

theta_de

CONST

Yt

Motion_profi

Motion profile Modified PI Controller

actθPlant Model

Simulation Results

Random Noise


I

INTG

GAIN

GAIN

GA

IN

GAIN2

10

error_in_the

10

theta_actu

10

GAIN

GAIN

SUM4

I

10

disturbance

10

w2

10

theta_do

10

theta

10

w1

GAIN3

GAIN4

Modified PI Controller

Plant Model

actcc

actdesactpi

actdes Sk

Sk θωωθθθθθ ..2).(.).(

2

−−=−−

( ) cww +=+− •θ

221


Simulation ResultsTheta Actual & desired

Noise amplitude: 0.07 - 0.1

Noise interval: 2 sec

t_des_theta_d

t [s]

0.1k

-10

20

40

60

80

0 102 4 6 8

t_des_theta_d

t [s]

0.1k

-10

20

40

60

80

0 102 4 6 8


Simulation Results

control inputs w1 and w2w1.VALw2.VAL

t [s]

7

0

2

3

4

5

0 102 4 6 8

w1.VAL w2.VAL

t [s]

8

1

2

3

4

5

6

7

0 102 4 6 8 Noise amplitude: 0.07 - 0.1

Noise interval: 2 sec


Outline



3. Control schemes



4. Conclusion


Active Disturbance Rejection Controller

•New digital controller to motion control problems

• Disturbances are estimated using extended state observer (ESO) and compensated in each sampling period.

•Dynamic compensation reduces motion system to a double integrator which can be controlled using a nonlinear PID controller


Extended State Observer• It is a unique nonlinear observer • Proper Selection of the gains and functions are

critical to the success of the observer• Once ESO is properly setup, the performance of the

observer is quite insensitive to plant variations and disturbances

+

−−

=

•

•

yub

zz

z

zo

oo

o

o2

2

12

2

1

02

012

ωω

ωω


Plant Model

Simulation Results


Define Simplorer inputs and outputs in the property dialog of the SiM2SiM component

Simplorer and Matlab


Matlab/Simulink Model

Outputs from the SimplorerInputs to the

simplorer


Simulation Results

t_des_dGAIN1.theta_d

t [s]

0.1k

-10

20

40

60

80

0 1.10.2 0.4 0.6 0.8

Theta Actual and Theta desired

Noise amplitude: 0.05 Noise Interval: 0.5 sec

t_des_theta_

t [s]

0.1k

-10

20

40

60

80

0 1.70.2 0.6 1 1.2


w1.VAw2.VA

t [s]

12

-2

2468

0 1.10.2 0.4 0.6 0.8

w1 and w2

Simulation Results

w1.VAw2.VA

t [s]

15

-20

0

-10

-5

5

0 1.70.4 0.8 1 1.2

Noise amplitude: 0.05 Noise Interval: 0.5 sec


• The simulation of Modified PI and ADRC showed that ADRC worked well for the system

• 1 DOF problem will be extended to 3 degrees of freedom problem

• Implementation of the controller design in microcontroller/FPGA microchip.

• Comparisons with other controllers

Conclusion and Future work

satellite attitude control system design using reaction...

Documents