ECE5320 Mechatronics
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Prepared by: Shelley Rounds Dept. of Electrical and Computer Engineering Utah State University PowerPoint PPT Presentation


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ECE5320 Mechatronics Assignment#01: Literature Survey on Sensors and Actuators Topic: Torque Coil Actuators. Prepared by: Shelley Rounds Dept. of Electrical and Computer Engineering Utah State University E: [email protected] T: ( 801)884-9235. 3/9/2007. Outline. Reference List

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Prepared by: Shelley Rounds Dept. of Electrical and Computer Engineering Utah State University

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Prepared by shelley rounds dept of electrical and computer engineering utah state university

ECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Topic: Torque Coil Actuators

Prepared by:

Shelley Rounds

Dept. of Electrical and Computer Engineering

Utah State University

E: [email protected]

T: (801)884-9235

3/9/2007


Outline

Outline

  • Reference List

  • To probe further

  • Applications

    • Attitude Control

      • Operational Interface

      • Parameters

  • Basic working principle

  • Sample Configuration

  • Specifications

  • Limitations

  • Cost

ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators


Reference list

Reference List

  • http://www.oss.goodrich.com/datasheets/oss/Goodrich_TRSeries_TorqueRods.pdf

  • http://cosmos.ssol.iastate.edu/cysat/Docs/Fall%2003/Controls/Control%20overview.pdf

  • M. J. Sidi, “Spacecraft Dynamics and Control” Cambridge University Press, 2005.

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

  • http://einstein.stanford.edu/highlights/hl_102805.html

  • http://ocw.mit.edu/NR/rdonlyres/Mechanical-Engineering/2-141Fall-2002/4706270A-4F69-4020-958A-F5172054F35F/0/dcpmm_basics.pdf

  • http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magmom.html

  • http://www.st.northropgrumman.com/capabilities/SiteFiles/technicallibrary/aiaa_1369.pdf

ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators


To explore further survival pointers of web references etc

To explore further (survival pointers of web references etc)

  • http://staff.ee.sun.ac.za/whsteyn/Papers/Magsat.pdf

  • http://ocw.mit.edu/NR/rdonlyres/Aeronautics-and-Astronautics/16-358JSystem-SafetySpring2003/B169A368-9DCC-4916-8897-12B0DE4DC855/0/hete.pdf

  • http://ocw.mit.edu/NR/rdonlyres/Mechanical-Engineering/2-141Fall-2002/4706270A-4F69-4020-958A-F5172054F35F/0/dcpmm_basics.pdf

  • http://www.sti.nasa.gov/tto/spinoff1997/t3.html

  • http://www.nasa.gov/centers/ames/research/technology-onepagers/advanced_min_wheel.html

ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators


Applications

Applications

“Satellites are increasingly used in telecommunications, scientific research, surveillence, and meteorology. These satellites rely heavily on the effectiveness of complex onboard control systems.”

From “Spacecraft Dynamics and Control”

CySat Model

Torque coils are used in a spacecraft to accurately control its orientation.

ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators


Attitude control

Attitude Control

  • Attitude control

    • Control of the position and rotation of the spacecraft

    • Relative to the object that it is orbiting, or relative to sun and stars

    • Orientation described by roll, pitch and yaw angles

www.st.northropgrumman.com

UofU CubeSat

ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators


Attitude control1

Attitude Control

  • Attitude control system must react to external torques

  • External torques:

    • Aerodynamic

    • Solar

    • Magnetic

    • Gravity Gradient

ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators


Operational interface

Operational Interface

The attitude control system consists of:

  • Sensors (gyroscopes, magnetometers etc.)

  • Actuators (torque coils, momentum wheels etc.)

  • Controlling Algorithms (Control laws from torque equations etc.)

From ECE 5320 class slides

ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators


Attitude control parameters

Attitude Control Parameters

From Goodrich

ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators


Basic working principle

Basic Working Principle

  • Torque Rods

    • Act as electromagnets

    • Interacts with Earth’s magnetic field

    • Creates controlled torque to reorient spacecraft

    • Magnetic moment depends on amount of current through the coil

    • Direction of current determines repelling or attracting force

Torque Rods (Goodrich)

ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators


Basic working principle1

Basic Working Principle

Torque coils take advantage of the Earth’s Magnetic Field to control the position of the spacecraft.

Three orthogonal coils can control the x, y, and z-axis.

einstein.stanford.edu

ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators


Basic working principle2

Basic Working Principle

ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators


Basic working principle3

Basic Working Principle

  • The equation for magnetic moment in the current-carrying loop, with current    and area vector      is given by:

  • Where

    •    is the magnetic moment, a vector measured in ampere–square meters

    •    is the current, a scalar measured in amperes, and

    •    is the loop area vector

ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators


Basic working principle4

Basic Working Principle

  • The magnetictorque of an object is given by:

  • Where

    is the torque, measured in Newton-meters,

    is the magnetic moment, measured in ampere-square meters, and

    is the magnetic field, measured in Newtons per (ampere-meter).

ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators


Basic working principle5

Basic Working Principle

  • Dipole moment linearly proportional (±4%) to input current

  • Saturation

    • Point where dipole moment deviates from approximation by ±30%

Typical performance curve of Torque Coil

From “Spacecraft Dynamics and Control”

ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators


Sample configuration

Sample Configuration

From CySat project

ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators


Sample configuration1

Sample Configuration

  • Configuration Procedure

    • Magnetometer and gyros send information to the microcontroller.

    • Microcontroller sends current to the torque coils.

    • Spacecraft moves in the desired direction.

ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators


Specifications

Specifications

From “Spacecraft Dynamics and Control”

ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators


Limitations

Limitations

  • Creates stray magnetic fields

    • Affects magnetometer readings

  • Applied torques extremely small

    • Magnetic moment proportional to 1/(Distance from earth)3

      B = m/R3

    • Torque coils cannot be used if too far away from earth

  • Moments are direction-dependant

ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators


Prepared by shelley rounds dept of electrical and computer engineering utah state university

Cost

  • Ithaco

  • Hughes

  • Lockheed

  • McDonnell Douglas

  • cost approx. $2000

ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators


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