SemiAutonomous Spacecraft Docking Control

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Semi-Autonomous Spacecraft Docking Control

• By Cengiz Akinli

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Overview

• Relative precision of target and chase attitude
  measurements
• 3-axis manual control
• Project Summary

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Relative Precisionof Attitude MeasurementsAssump
tions

• No sub-pixel interpolation
• Generated image is ideal Target spots always
  fill one pixel exactly (regardless of range)
  Target spots shift pixels instantaneously
• Chase position and target attitude determination
  are equivalent problems

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Relative Precisionof Attitude Measurements

• VGS style target produces a row of dots image
• Range determined by angular separation in
  FOV(e.g. This example shows 8 pixel separation
  while aligned.)

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Chase Attitude Measurement

• Pixel separation is fixed angle (range
  independent)
• Minimum detectable chase rotation is the same

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Target Attitude Measurement

• Minimum detectable target rotation is a(In
  image, c moves up one pixel relative to a b.)
• cc hsina (1)

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Center Target Spot Movement

• Assume a is small ? c is directly above c and?
  is 90.
• Then cc rsinB (2)
• Combining (1) and (2) yields

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Three Axis Manual Control

• USB joystick-based via any network connected
  system
• Network comm via unencrypted connection to
  non-network aware server under inetd.
• Joystick control NOT currently a DSACSS component

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Three Axis Manual Control

• Effective simultaneous throttle control on all
  axes
• Set regulator to throttle setting of axis with
  maximum stick displacement, effect throttle
  control on other axes via PWM.
• Includes hooks for overthrottling (for PWM effect
  on net output pressure) to include results of
  other work in progress.

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Project Summary

• Progress what has been accomplished
• Problems areas of concern
• Plans whats next

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Progress

• Literature reviewed existing sensors reviewed
  and strengths and weaknesses assessed
• Configuration determined used above information
  to settle on setup
• Hardware tested successful in setup of control
  system (thrusters) and manual control device
  (joystick) via remote manipulation

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Problems

• Hardware not working- no image from USB cameras
  yet, though several are visible as devices

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Plans

• Laser designators DB mounting bracket
• Target DB deflector and camera mount
• Automatic control select controller

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Questions

• Go ahead. Make my day.