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Are robot arms ever used for attitude control in space?
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Motion of a robotic arm mounted on a spacecraft presents an interesting challenge from a control perspective. A robot arm, such as Canadarm (space shuttle) and Canadarm2 (ISS), has significant mass compared to the spacecraft and thus its motion can perturb its attitude as well as its position. In a perfect world, one has plenty of propellant for attitude control thrusters to compensate for robotic arm motion. However, propellant is at a premium and even if plentiful, can impinge on either the robot arm itself or the payload that it is trying to manipulate.
This got me thinking... If a robot arm can cause rotation/translation of a spacecraft, it could theoretically be used as an attitude controller of sorts. This would lead to a much more complicated dynamical control problem because the final pose of the robot end effector is greatly influenced by the path taken. But nonetheless, in theory this could work if the robot arm mass is significant (e.g. w/ a payload caught). Also, if the robot arm is powered primarily by solar panels, it could theoretically be used over a longer span of time.
At least, this is all theory. In practice, are spacecraft robotic arms typically/ever used for attitude control, either as part of its payload-catching mission or as a non-standard method of attitude control? I'm not limiting myself to just the ISS or space shuttles, and am open to any robotic arm in space.
attitude robotic-arm canadarm
asked 3 hours ago
Paul
579615
add a comment |Â
up vote
2
down vote
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Motion of a robotic arm mounted on a spacecraft presents an interesting challenge from a control perspective. A robot arm, such as Canadarm (space shuttle) and Canadarm2 (ISS), has significant mass compared to the spacecraft and thus its motion can perturb its attitude as well as its position. In a perfect world, one has plenty of propellant for attitude control thrusters to compensate for robotic arm motion. However, propellant is at a premium and even if plentiful, can impinge on either the robot arm itself or the payload that it is trying to manipulate.
This got me thinking... If a robot arm can cause rotation/translation of a spacecraft, it could theoretically be used as an attitude controller of sorts. This would lead to a much more complicated dynamical control problem because the final pose of the robot end effector is greatly influenced by the path taken. But nonetheless, in theory this could work if the robot arm mass is significant (e.g. w/ a payload caught). Also, if the robot arm is powered primarily by solar panels, it could theoretically be used over a longer span of time.
At least, this is all theory. In practice, are spacecraft robotic arms typically/ever used for attitude control, either as part of its payload-catching mission or as a non-standard method of attitude control? I'm not limiting myself to just the ISS or space shuttles, and am open to any robotic arm in space.
attitude robotic-arm canadarm
asked 3 hours ago
Paul
579615
@JCRM: I had a suspicion that my estimate of its mass was a bit high.
– Paul
3 hours ago
They are used for attitude (and position) control of the payloads they handle.
– Organic Marble
15 mins ago
add a comment |Â
up vote
2
down vote
favorite
up vote
2
down vote
favorite
Motion of a robotic arm mounted on a spacecraft presents an interesting challenge from a control perspective. A robot arm, such as Canadarm (space shuttle) and Canadarm2 (ISS), has significant mass compared to the spacecraft and thus its motion can perturb its attitude as well as its position. In a perfect world, one has plenty of propellant for attitude control thrusters to compensate for robotic arm motion. However, propellant is at a premium and even if plentiful, can impinge on either the robot arm itself or the payload that it is trying to manipulate.
This got me thinking... If a robot arm can cause rotation/translation of a spacecraft, it could theoretically be used as an attitude controller of sorts. This would lead to a much more complicated dynamical control problem because the final pose of the robot end effector is greatly influenced by the path taken. But nonetheless, in theory this could work if the robot arm mass is significant (e.g. w/ a payload caught). Also, if the robot arm is powered primarily by solar panels, it could theoretically be used over a longer span of time.
At least, this is all theory. In practice, are spacecraft robotic arms typically/ever used for attitude control, either as part of its payload-catching mission or as a non-standard method of attitude control? I'm not limiting myself to just the ISS or space shuttles, and am open to any robotic arm in space.
attitude robotic-arm canadarm
asked 3 hours ago
Paul
579615
Motion of a robotic arm mounted on a spacecraft presents an interesting challenge from a control perspective. A robot arm, such as Canadarm (space shuttle) and Canadarm2 (ISS), has significant mass compared to the spacecraft and thus its motion can perturb its attitude as well as its position. In a perfect world, one has plenty of propellant for attitude control thrusters to compensate for robotic arm motion. However, propellant is at a premium and even if plentiful, can impinge on either the robot arm itself or the payload that it is trying to manipulate.
This got me thinking... If a robot arm can cause rotation/translation of a spacecraft, it could theoretically be used as an attitude controller of sorts. This would lead to a much more complicated dynamical control problem because the final pose of the robot end effector is greatly influenced by the path taken. But nonetheless, in theory this could work if the robot arm mass is significant (e.g. w/ a payload caught). Also, if the robot arm is powered primarily by solar panels, it could theoretically be used over a longer span of time.
At least, this is all theory. In practice, are spacecraft robotic arms typically/ever used for attitude control, either as part of its payload-catching mission or as a non-standard method of attitude control? I'm not limiting myself to just the ISS or space shuttles, and am open to any robotic arm in space.
attitude robotic-arm canadarm
attitude robotic-arm canadarm
asked 3 hours ago
Paul
579615
asked 3 hours ago
Paul
579615
edited 3 hours ago
asked 3 hours ago
Paul
579615
asked 3 hours ago
Paul
579615
asked 3 hours ago
Paul
579615
579615
@JCRM: I had a suspicion that my estimate of its mass was a bit high.
– Paul
3 hours ago
They are used for attitude (and position) control of the payloads they handle.
– Organic Marble
15 mins ago
add a comment |Â
@JCRM: I had a suspicion that my estimate of its mass was a bit high.
– Paul
3 hours ago
They are used for attitude (and position) control of the payloads they handle.
– Organic Marble
15 mins ago
@JCRM: I had a suspicion that my estimate of its mass was a bit high.
– Paul
3 hours ago
@JCRM: I had a suspicion that my estimate of its mass was a bit high.
– Paul
3 hours ago
They are used for attitude (and position) control of the payloads they handle.
– Organic Marble
15 mins ago
They are used for attitude (and position) control of the payloads they handle.
– Organic Marble
15 mins ago
add a comment |Â
2 Answers
2
active
oldest
votes
up vote
2
down vote
No.
Instead of using a complicated robot arm that already has a task, much simpler and cheaper reaction wheels are used.
answered 3 hours ago
Hobbes
76.5k2210351
If the robot arm were already there for reasons other than attitude control, could it then also be used in this way, perhaps for fine control?
– uhoh
2 hours ago
add a comment |Â
up vote
2
down vote
In theory, yes. In practice, no. The problem is gimbal lock, which is problematic even for practical attitude controls that depend on moving masses such as reaction wheels or control moment gyros. Gimbal lock will rear its ugly head with a robotic arm attitude controller in no time short.
answered 3 hours ago
David Hammen
28.2k166125
2
Can you elaborate? What is it about a robot arm that makes gimbal lock much worse?
– Paul
3 hours ago
@Paul - A real robotic arm (e.g., Canadarm) has stop points. Moving the arms beyond those stop points may result in the arms hitting structure (hence the stop points). Those dangers don't exist if your robot is named Robby. Such a robot can instead wave its arms at will while claiming "Danger, Will Robinson!" But this is presumably a real robotic arm.
– David Hammen
1 hour ago
The arms have a lot of singularities too. I think 7 for the shuttle arm, more for the big arm. Far from my reference material though.
– Organic Marble
17 mins ago
add a comment |Â
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
2
down vote
No.
Instead of using a complicated robot arm that already has a task, much simpler and cheaper reaction wheels are used.
answered 3 hours ago
Hobbes
76.5k2210351
If the robot arm were already there for reasons other than attitude control, could it then also be used in this way, perhaps for fine control?
– uhoh
2 hours ago
add a comment |Â
up vote
2
down vote
No.
Instead of using a complicated robot arm that already has a task, much simpler and cheaper reaction wheels are used.
answered 3 hours ago
Hobbes
76.5k2210351
If the robot arm were already there for reasons other than attitude control, could it then also be used in this way, perhaps for fine control?
– uhoh
2 hours ago
add a comment |Â
up vote
2
down vote
up vote
2
down vote
No.
Instead of using a complicated robot arm that already has a task, much simpler and cheaper reaction wheels are used.
answered 3 hours ago
Hobbes
76.5k2210351
No.
Instead of using a complicated robot arm that already has a task, much simpler and cheaper reaction wheels are used.
answered 3 hours ago
Hobbes
76.5k2210351
answered 3 hours ago
Hobbes
76.5k2210351
answered 3 hours ago
Hobbes
76.5k2210351
answered 3 hours ago
Hobbes
76.5k2210351
76.5k2210351
If the robot arm were already there for reasons other than attitude control, could it then also be used in this way, perhaps for fine control?
– uhoh
2 hours ago
add a comment |Â
If the robot arm were already there for reasons other than attitude control, could it then also be used in this way, perhaps for fine control?
– uhoh
2 hours ago
If the robot arm were already there for reasons other than attitude control, could it then also be used in this way, perhaps for fine control?
– uhoh
2 hours ago
If the robot arm were already there for reasons other than attitude control, could it then also be used in this way, perhaps for fine control?
– uhoh
2 hours ago
add a comment |Â
up vote
2
down vote
In theory, yes. In practice, no. The problem is gimbal lock, which is problematic even for practical attitude controls that depend on moving masses such as reaction wheels or control moment gyros. Gimbal lock will rear its ugly head with a robotic arm attitude controller in no time short.
answered 3 hours ago
David Hammen
28.2k166125
2
Can you elaborate? What is it about a robot arm that makes gimbal lock much worse?
– Paul
3 hours ago
@Paul - A real robotic arm (e.g., Canadarm) has stop points. Moving the arms beyond those stop points may result in the arms hitting structure (hence the stop points). Those dangers don't exist if your robot is named Robby. Such a robot can instead wave its arms at will while claiming "Danger, Will Robinson!" But this is presumably a real robotic arm.
– David Hammen
1 hour ago
The arms have a lot of singularities too. I think 7 for the shuttle arm, more for the big arm. Far from my reference material though.
– Organic Marble
17 mins ago
add a comment |Â
up vote
2
down vote
In theory, yes. In practice, no. The problem is gimbal lock, which is problematic even for practical attitude controls that depend on moving masses such as reaction wheels or control moment gyros. Gimbal lock will rear its ugly head with a robotic arm attitude controller in no time short.
answered 3 hours ago
David Hammen
28.2k166125
2
Can you elaborate? What is it about a robot arm that makes gimbal lock much worse?
– Paul
3 hours ago
@Paul - A real robotic arm (e.g., Canadarm) has stop points. Moving the arms beyond those stop points may result in the arms hitting structure (hence the stop points). Those dangers don't exist if your robot is named Robby. Such a robot can instead wave its arms at will while claiming "Danger, Will Robinson!" But this is presumably a real robotic arm.
– David Hammen
1 hour ago
The arms have a lot of singularities too. I think 7 for the shuttle arm, more for the big arm. Far from my reference material though.
– Organic Marble
17 mins ago
add a comment |Â
up vote
2
down vote
up vote
2
down vote
In theory, yes. In practice, no. The problem is gimbal lock, which is problematic even for practical attitude controls that depend on moving masses such as reaction wheels or control moment gyros. Gimbal lock will rear its ugly head with a robotic arm attitude controller in no time short.
answered 3 hours ago
David Hammen
28.2k166125
In theory, yes. In practice, no. The problem is gimbal lock, which is problematic even for practical attitude controls that depend on moving masses such as reaction wheels or control moment gyros. Gimbal lock will rear its ugly head with a robotic arm attitude controller in no time short.
answered 3 hours ago
David Hammen
28.2k166125
answered 3 hours ago
David Hammen
28.2k166125
answered 3 hours ago
David Hammen
28.2k166125
answered 3 hours ago
David Hammen
28.2k166125
28.2k166125
2
Can you elaborate? What is it about a robot arm that makes gimbal lock much worse?
– Paul
3 hours ago
@Paul - A real robotic arm (e.g., Canadarm) has stop points. Moving the arms beyond those stop points may result in the arms hitting structure (hence the stop points). Those dangers don't exist if your robot is named Robby. Such a robot can instead wave its arms at will while claiming "Danger, Will Robinson!" But this is presumably a real robotic arm.
– David Hammen
1 hour ago
The arms have a lot of singularities too. I think 7 for the shuttle arm, more for the big arm. Far from my reference material though.
– Organic Marble
17 mins ago
add a comment |Â
2
Can you elaborate? What is it about a robot arm that makes gimbal lock much worse?
– Paul
3 hours ago
@Paul - A real robotic arm (e.g., Canadarm) has stop points. Moving the arms beyond those stop points may result in the arms hitting structure (hence the stop points). Those dangers don't exist if your robot is named Robby. Such a robot can instead wave its arms at will while claiming "Danger, Will Robinson!" But this is presumably a real robotic arm.
– David Hammen
1 hour ago
The arms have a lot of singularities too. I think 7 for the shuttle arm, more for the big arm. Far from my reference material though.
– Organic Marble
17 mins ago
2
2
Can you elaborate? What is it about a robot arm that makes gimbal lock much worse?
– Paul
3 hours ago
Can you elaborate? What is it about a robot arm that makes gimbal lock much worse?
– Paul
3 hours ago
@Paul - A real robotic arm (e.g., Canadarm) has stop points. Moving the arms beyond those stop points may result in the arms hitting structure (hence the stop points). Those dangers don't exist if your robot is named Robby. Such a robot can instead wave its arms at will while claiming "Danger, Will Robinson!" But this is presumably a real robotic arm.
– David Hammen
1 hour ago
@Paul - A real robotic arm (e.g., Canadarm) has stop points. Moving the arms beyond those stop points may result in the arms hitting structure (hence the stop points). Those dangers don't exist if your robot is named Robby. Such a robot can instead wave its arms at will while claiming "Danger, Will Robinson!" But this is presumably a real robotic arm.
– David Hammen
1 hour ago
The arms have a lot of singularities too. I think 7 for the shuttle arm, more for the big arm. Far from my reference material though.
– Organic Marble
17 mins ago
The arms have a lot of singularities too. I think 7 for the shuttle arm, more for the big arm. Far from my reference material though.
– Organic Marble
17 mins ago
add a comment |Â
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@JCRM: I had a suspicion that my estimate of its mass was a bit high.
– Paul
3 hours ago
They are used for attitude (and position) control of the payloads they handle.
– Organic Marble
15 mins ago