gyro-control of a solar sailing satellite · 2017-03-01 · gyro-control of a solar sailing...

Gyro-Control of a Solar Sailing Satellite

by

Hendrik W. Jordaan

Willem H. Steyn

Electronic Systems Laboratory

Department of Electrical & Electronic Engineering

Stellenbosch University

January 20, 2017

International Solar Sailing Symposium

Background

Attitude ControlSolar sailing

Gyro-Control

Conclusion

Situated about 30 minutes

away from Cape-Town,

South-Africa

Stellenbosch


Background


Gyro-Control

Conclusion

History with microsatellites,

SunSat, SunSpace,

SumbandilaSat

Current main focus is on ADCS

research

Develop ADCS CubeSat

components which is sold

under CubeSpace brand

Also involved in a number of

interesting international projects

Stellenbosch University


Background


Gyro-Control

Conclusion

• Current solar sailing missions main payload is the solar sail

• Future missions will have other science payloads e.g.

image payloads

• Main specification driver for attitude control is mission

payload

• Attitude control requirements for solar sailing is low, only

slow manoeuvres and rough attitude stability relative to a

sun angle.

• High sampling and long exposure payloads very stringent

attitude requirements

Attitude Requirements


Background


Gyro-Control

Conclusion

• Largest difference between a solar sail and standard

spacecraft is the large MoI, which is obtained when

deploying a large space structure.

• When comparing the MoI of a 80m2 and 100m2 square sail

there is a 43.9% increase in the MoI with less than a meter

increase in boom length.

• The attitude control actuator specifications should increase

• This is dependent on the sail/spacecraft MoI ratio

• Ratio of the sail MoI relative to the entire spacecraft MoI

Standard Satellite vs Solar Sail Satellite

Parameter 80m2 Sail 100m2 Sail

Boom length 6.325m 7.071m

MoI Ixx=Izz 10.149kg.m2 14.607kg.m2

MoI Iyy 20.299kg.m2 29.213kg.m2


Background


Gyro-Control

Conclusion

• The sail/spacecraft MoI ratio is determined simply by λ =max(𝚲) with 𝚲 = 𝑰𝑆/𝑰 where 𝑰𝑆 the MoI of the sail and 𝑰 is

MoI of the entire spacecraft.

• Small λ indicates rotational dynamics of spacecraft is

dominant

• Larger λ indicates that the dynamics are greatly influenced

by the sail

• MoI will greatly influence the attitude performance either

increase in sail size or vibration of non-rigid elements

• Some control attitude control methods will greatly influence

this ratio and thus less suitable to scale to larger solar sails.

• Manoeuvres are limited by actuator specifications and the

non-rigid dynamics of the sail

Standard Satellite vs Solar Sail Satellite


Background


Gyro-Control

Conclusion

• Current attitude control methods can be separated into two

categories:

• Active methods

• Thrusters (gas and electric)

• Standard magnetorquer rods

• Reaction and momentum wheels

• Solar thrust methods

• Changing CoM

• Translation stage

• Control boom

• Mass-balasts

• Changing CoP

• Reflective changes

• Control vanes

• Sail shape changes

• Review by Fu et al. 2016

Current attitude control methods


Background


Gyro-Control

Conclusion

• Spinning sail has a number of advantages above stabilised

sail

• Unsymmetrical solar thrust averaged to spin vector

• Centrifugal force produce internal force

• Major drawbacks are

• Satellite bus is rotating, limits mission payload

• Angular momentum bias resists angular manoeuvres

Spinning Solar Sail

Standard Spinning Solar Sail Slow Spinning Solar Sail


Background


Gyro-Control

Conclusion

• The tri-spin solar sail consists of three sections rotating

relative to each other.

• The nett angular momentum of the spacecraft is zero

• Similar to connecting two dual-spin satellite to each other

• The gyro tri-spin solar sail is created by placing these

rotating structures on two-axes gimbals.

Tri-Spin Solar Sail

Tri-Spin Solar Sail Gyro Tri-Spin Solar Sail


Background


Gyro-Control

Conclusion

• This configuration creates a dual CMG configuration

• Torque multiplication achieved with small changes in gimbal

angles

• Steering laws of gimbal angles, assuming scissoring, can

be used to determine required gimbals angels and control

inputs for certain torque requirements

Gyro Control


Background


Gyro-Control

Conclusion

Gyro Control (cont)


• Creates a scalable attitude actuator – angular momentum of

the sail is used to determine the actuator performance

• Larger angular momentum requires smaller gimbal angles

to obtain reference torque

Background


Gyro-Control

Conclusion

Gyro Control (cont)


• Investigated the effects of some control inconsistencies

• Angular momentum bias, gimbal angle errors and MoI

uncertainties are investigated

Background


Gyro-Control

Conclusion

• High performance attitude control must be achieved on

solar sail satellites to make it appropriate for science

missions.

• Some control methods scale much better to larger sails than

others.

• Gyro tri-spin solar sail produce an attitude control actuator

that scales with the MoI of the sail

• Comes at a cost e.g. large mechanical complexities

• Starting to exist the realm of ignoring sail vibrations

Conclusion


Background


Gyro-Control

Conclusion

• The current trend is for more deployables on smaller

spacecrafts, not only true for solar sails.

• Smaller spacecrafts are more susceptible to non-rigid

influence.

• Future ADCS needs to be able to handle active damping of

vibrations to be able to operate mission payloads.

Final Remarks


Background


Gyro-Control

Conclusion

Thank you

Questions?

Willem Jordaan [email protected]


mailto:[email protected]

gyro-control of a solar sailing satellite · 2017-03-01 · gyro-control of a solar sailing...

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