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Definition of term "seeker rate"
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Matt
Nov 24, 2011, 10:44:37 PM11/24/11
to
What's the definition of the terms "seeker rate" and "track loop" in
describing a radar seeker system in an AAM?
Thanks,
Matt
describing a radar seeker system in an AAM?
Thanks,
Matt
Orval Fairbairn
Nov 25, 2011, 7:48:13 PM11/25/11
to
In article
<9cb26a9e-b18b-4655...@da3g2000vbb.googlegroups.com>,
If we told you, we'd have to kill you!
<9cb26a9e-b18b-4655...@da3g2000vbb.googlegroups.com>,
Paul F Austin
Nov 25, 2011, 9:00:56 PM11/25/11
to
used to have only a single sensor scanned across the field of view.
Later that changed to a multi-pixel focal plane. Both had a rate at
which the relative position of the target was updated. Radar seekers
have analogous scanning functions, again updating the position of the
target with respect to the missile at some rate. That is, I believe,
what you're asking about in terms of the "seeker rate". The target
position (always with respect to the missile) is fed into a tracking
loop that will provide command signals to the body control loop. Each is
a closed loop control system. The tracking loop generates a smooth set
of positions, updated with the latest position but also computed using
the history of prior positions. The body control loop takes the smoothed
tracking data and applies control laws that reflect the dynamics of the
missile and sends commands to aero surfaces or possibly propulsion (if
thrust vectoring is available).
Paul
Eunometic
Nov 27, 2011, 12:27:20 PM11/27/11
to
On Nov 26, 1:00 pm, Paul F Austin <pfaus...@bellsouth.net> wrote:
> On 11/25/2011 7:48 PM, Orval Fairbairn wrote:
>
> > In article
> > <9cb26a9e-b18b-4655-b9c8-fa148086f...@da3g2000vbb.googlegroups.com>,
> On 11/25/2011 7:48 PM, Orval Fairbairn wrote:
>
> > In article
> > Matt<MattWri...@AOL.com> wrote:
would likely refer to the angular rate the LOS (line of sight) of the
seeker head (radar or IR) is moving relative to the boresight
(straight ahead) of the missile on the seekers gimbals. Various
algorithems and filters are applied to smooth the motion of the seeker
in tracking or rather estimating the position of the target in the
face of noise and motion.
You might try:
Sight Line Rate Estimation in Missile Seeker Using Disturbance
Observer-Based Technique
Smita Sadhu and T. K. Ghoshal
Abstract—Filtering of base motion disturbance from the sight
line rate is necessary for homing guidance of missiles. The present
work proposes using a noninvasive seeker filter based on the
disturbance
observer concept to extract the target sight line rate signal
from the raw signal corrupted with base motion disturbance. It
is shown that the disturbance observer-based filter in favorable
(nominal) condition can totally eliminate the platform motion from
the raw sight line rate signal. The performance of the filter for
off-nominal condition is also derived and exemplified. Simulation
results demonstrate improved performance of the proposed filter
compared to previously reported schemes.
Index Terms—Base motion isolation, disturbance observer, missile
seeker, sight line rate (SLR).
Paul F Austin
Nov 27, 2011, 5:30:40 PM11/27/11
to
and smooth both, although I had never heard of it referred to a "seeker
rate".
Paul
Dweezil Dwarftosser
Nov 28, 2011, 11:25:02 AM11/28/11
to
euno...@yahoo.com.au wrote...
Probably true - but read on.
Things were a lot simpler in the analog days - when
an AIM-7E-2 could pull an (estimated) 40g left turn
to shoot down a mig crossing the attacker's nose at
about a 90 degree offset at a 2000 ft range.
There was no 'sampling rate' required in an analog
tracking system; it was continuous (and almost
instantaneously resolved, in relative AZ and EL).
Greater deflection from boresight simply resulted in
greater deflection of the control surfaces to correct
the error. (Altitude air density - or lack of it -
modified the deflection in a direct manner, as did
a launching-aircraft-computed "English Bias" signal
applied prior to launch - but only if a few seconds
of target lockon preceeded the launch.)
Than came digital: notoriously slower - especially
when resolving angle and changing angular-rate info.
Not only did the differing outside-world in/out
items require sequential sampling; the sampling rate
for very high deflections had to increase, thus
spending less time on other important attack-missile
functions.
> Various algorithems and filters are applied to smooth
> the motion of the seeker in tracking or rather
> estimating the position of the target in the
> face of noise and motion.
Nope. Estimating target position is a great way to
miss him - since he presumably will be violently
maneuvering, specifically trying to avoid being
tracked.
In very simple terms, tracking attempts to have the
received power of the radar return be the same (360
degrees) all around thhe seeker's axial look-angle.
Should power be less in one area, it will steer the
missile more towards that 'weaker' area. The only
real 'filtering' occurs in the natural response time
of the control surface actuators, which slightly lag
the command; it's a 'natural' noise/flutter filter.
> You might try:
>
> Sight Line Rate Estimation in Missile Seeker Using Disturbance
> Observer-Based Technique
>
> Smita Sadhu and T. K. Ghoshal
>
> Abstract?Filtering of base motion disturbance from the sight
I love it when PhDs try to complicate relatively
simple things - though this might be beneficial to
(human visible) video-guided weapons; it might
stabilise the scene on the screen a bit. Otherwise,
nah !!
Things were a lot simpler in the analog days - when
an AIM-7E-2 could pull an (estimated) 40g left turn
to shoot down a mig crossing the attacker's nose at
about a 90 degree offset at a 2000 ft range.
There was no 'sampling rate' required in an analog
tracking system; it was continuous (and almost
instantaneously resolved, in relative AZ and EL).
Greater deflection from boresight simply resulted in
greater deflection of the control surfaces to correct
the error. (Altitude air density - or lack of it -
modified the deflection in a direct manner, as did
a launching-aircraft-computed "English Bias" signal
applied prior to launch - but only if a few seconds
of target lockon preceeded the launch.)
Than came digital: notoriously slower - especially
when resolving angle and changing angular-rate info.
Not only did the differing outside-world in/out
items require sequential sampling; the sampling rate
for very high deflections had to increase, thus
spending less time on other important attack-missile
functions.
> Various algorithems and filters are applied to smooth
> the motion of the seeker in tracking or rather
> estimating the position of the target in the
> face of noise and motion.
miss him - since he presumably will be violently
maneuvering, specifically trying to avoid being
tracked.
In very simple terms, tracking attempts to have the
received power of the radar return be the same (360
degrees) all around thhe seeker's axial look-angle.
Should power be less in one area, it will steer the
missile more towards that 'weaker' area. The only
real 'filtering' occurs in the natural response time
of the control surface actuators, which slightly lag
the command; it's a 'natural' noise/flutter filter.
> You might try:
>
> Sight Line Rate Estimation in Missile Seeker Using Disturbance
> Observer-Based Technique
>
> Smita Sadhu and T. K. Ghoshal
>
> line rate is necessary for homing guidance of missiles. The present
> work proposes using a noninvasive seeker filter based on the
> disturbance
> observer concept to extract the target sight line rate signal
> from the raw signal corrupted with base motion disturbance. It
> is shown that the disturbance observer-based filter in favorable
> (nominal) condition can totally eliminate the platform motion from
> the raw sight line rate signal. [...]
> work proposes using a noninvasive seeker filter based on the
> disturbance
> observer concept to extract the target sight line rate signal
> from the raw signal corrupted with base motion disturbance. It
> is shown that the disturbance observer-based filter in favorable
> (nominal) condition can totally eliminate the platform motion from
I love it when PhDs try to complicate relatively
simple things - though this might be beneficial to
(human visible) video-guided weapons; it might
stabilise the scene on the screen a bit. Otherwise,
nah !!
Eunometic
Nov 28, 2011, 11:55:05 PM11/28/11
to
On Nov 29, 3:25 am, Dweezil Dwarftosser <f4...@yahoo.com> wrote:
> eunome...@yahoo.com.au wrote...
Did this really ever happen given the reliabillity deficiencies of the
missile?
If it were true USAF pilots would've not needed to dog fight
and would be just blowing up MiGs cued up by their helmet sights.
> There was no 'sampling rate' required in an analog
> tracking system; it was continuous (and almost
> instantaneously resolved, in relative AZ and EL).
I would argue that conical scannning and pulse techniques
inherantly involve a 'sampling rate' and have
control system bandwidth limitations.
In anycase video grade digital to analog converters can sample at 100M/
samples/sec
while even home computers are doing billions of calcs/second.
> Greater deflection from boresight simply resulted in
> greater deflection of the control surfaces to correct
> the error. (Altitude air density - or lack of it -
> modified the deflection in a direct manner,
Yes, typical autopilot stuff.
> as did
> a launching-aircraft-computed "English Bias" signal
> applied prior to launch - but only if a few seconds
> of target lockon preceeded the launch.)
That I'll need help understanding "English Bias"
>
> Than came digital: notoriously slower - especially
> when resolving angle and changing angular-rate info.
> Not only did the differing outside-world in/out
> items require sequential sampling; the sampling rate
> for very high deflections had to increase, thus
> spending less time on other important attack-missile
> functions.
Horse and buggy.
> nah !!- Hide quoted text -
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -
> eunome...@yahoo.com.au wrote...
missile?
If it were true USAF pilots would've not needed to dog fight
and would be just blowing up MiGs cued up by their helmet sights.
> There was no 'sampling rate' required in an analog
> tracking system; it was continuous (and almost
> instantaneously resolved, in relative AZ and EL).
inherantly involve a 'sampling rate' and have
control system bandwidth limitations.
In anycase video grade digital to analog converters can sample at 100M/
samples/sec
while even home computers are doing billions of calcs/second.
> Greater deflection from boresight simply resulted in
> greater deflection of the control surfaces to correct
> the error. (Altitude air density - or lack of it -
> modified the deflection in a direct manner,
> as did
> a launching-aircraft-computed "English Bias" signal
> applied prior to launch - but only if a few seconds
> of target lockon preceeded the launch.)
>
> Than came digital: notoriously slower - especially
> when resolving angle and changing angular-rate info.
> Not only did the differing outside-world in/out
> items require sequential sampling; the sampling rate
> for very high deflections had to increase, thus
> spending less time on other important attack-missile
> functions.
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -
Ken S. Tucker
Nov 29, 2011, 4:10:18 AM11/29/11
to
Just read the front and conclusions for definitions,
http://www.sal.tkk.fi/publications/pdf-files/ehyt04.pdf
"Seeker rate", is bridge term enveloping, sensor swinging
rate (maintaining lock) and aerodynamic manuverability,
both are required.
If you intend to be a "dragon fly" you'll need the math ;-).
Ken
Dweezil Dwarftosser
Nov 29, 2011, 2:14:10 PM11/29/11
to
euno...@yahoo.com.au wrote...
> Dweezil Dwarftosser <f4...@yahoo.com> wrote:
>
> > Things were a lot simpler in the analog days - when
> > an AIM-7E-2 could pull an (estimated) 40g left turn
> > to shoot down a mig crossing the attacker's nose at
> > about a 90 degree offset at a 2000 ft range.
> >
>
> Did this really ever happen given the reliabillity deficiencies of the
> missile?
July 8th, 1972, Steve Ritchie and Chuck DeBellevue
(Five-kill and six-kill VN aces, respectively.)
I had one thing wrong in the above account, however.
The target was passing from left-to-right, rather
than right-to-left, so the missile pulled a 90 degree
RIGHTHAND turn.
BTW - the USAF had corrected almost all of the AIM-7
'reliability' problems within the next three years or
so, on F-4s. The problem was rarely the missile; more
often, it was the maintenance of the launching aircraft
- and a seriously-flawed 'interlocks out' procedure
which most pilots clung to, far too long.
Profoundly-better test equipment fixed the maintenance
problems - but the arrogance of the (aircrew) Fighter
Weapons School resisted the procedural changes tooth-
and-nail.
> If it were true USAF pilots would've not needed to dog fight
> and would be just blowing up MiGs cued up by their helmet sights.
The close-in knife fight (where BVR missiles suffer)
was mandated by the Rules-of-Engagement: visual
identification.
Every WCS troop knew that helmet-mounted cueing would
never work, long before the first attempts to create
such a system existed. (Calibration upon use is
mandatory, yet impossible to keep true in actual
combat use.)
> Dweezil Dwarftosser <f4...@yahoo.com> wrote:
>
> > Things were a lot simpler in the analog days - when
> > an AIM-7E-2 could pull an (estimated) 40g left turn
> > to shoot down a mig crossing the attacker's nose at
> > about a 90 degree offset at a 2000 ft range.
> >
>
> Did this really ever happen given the reliabillity deficiencies of the
> missile?
(Five-kill and six-kill VN aces, respectively.)
I had one thing wrong in the above account, however.
The target was passing from left-to-right, rather
than right-to-left, so the missile pulled a 90 degree
RIGHTHAND turn.
BTW - the USAF had corrected almost all of the AIM-7
'reliability' problems within the next three years or
so, on F-4s. The problem was rarely the missile; more
often, it was the maintenance of the launching aircraft
- and a seriously-flawed 'interlocks out' procedure
which most pilots clung to, far too long.
Profoundly-better test equipment fixed the maintenance
problems - but the arrogance of the (aircrew) Fighter
Weapons School resisted the procedural changes tooth-
and-nail.
> If it were true USAF pilots would've not needed to dog fight
> and would be just blowing up MiGs cued up by their helmet sights.
was mandated by the Rules-of-Engagement: visual
identification.
Every WCS troop knew that helmet-mounted cueing would
never work, long before the first attempts to create
such a system existed. (Calibration upon use is
mandatory, yet impossible to keep true in actual
combat use.)
Dweezil Dwarftosser
Nov 29, 2011, 2:47:02 PM11/29/11
to
euno...@yahoo.com.au wrote...
[...]
> > There was no 'sampling rate' required in an analog
> > tracking system; it was continuous (and almost
> > instantaneously resolved, in relative AZ and EL).
>
> I would argue that conical scannning and pulse techniques
> inherantly involve a 'sampling rate' and have
> control system bandwidth limitations.
You may be confusing launching-aircraft parameters
(which did use pulse techniques) with those of the
missile (which didn't).
> In anycase video grade digital to analog converters can
> sample at 100M/samples/sec while even home computers
Lessee, in 1972, the four-bit Intel 4004 was typically
clocked at 1.2 MHz, while DACs and ADCs boasted multi-
millisecond conversion times. IIRC, the 8008 didn't
arrive until '73 or '74.
>
> > Greater deflection from boresight simply resulted in
> > greater deflection of the control surfaces to correct
> > the error. (Altitude air density - or lack of it -
> > modified the deflection in a direct manner,
>
> Yes, typical autopilot stuff.
>
> > as did
> > a launching-aircraft-computed "English Bias" signal
> > applied prior to launch - but only if a few seconds
> > of target lockon preceeded the launch.)
>
> That I'll need help understanding "English Bias"
The term comes from the (American-English only?)
pool hall phrase describing the application of
some 'body english' to the cue ball, making it
curve, slow down, or even appear to turn a right
angle before contacting its target ball.
English Bias was a computed term applied to the
missile before launch, loosely describing a flight
path to use between it's initial roll (to flight
attitude) and self-acquisition of the target
aircraft's return.
> > Than came digital: notoriously slower - especially
> > when resolving angle and changing angular-rate info.
> > Not only did the differing outside-world in/out
> > items require sequential sampling; the sampling rate
> > for very high deflections had to increase, thus
> > spending less time on other important attack-missile
> > functions.
>
> Horse and buggy.
Perhaps - but still deadly, and far more improved than
it was almost 40 years ago.
[...]
> > There was no 'sampling rate' required in an analog
> > tracking system; it was continuous (and almost
> > instantaneously resolved, in relative AZ and EL).
>
> I would argue that conical scannning and pulse techniques
> inherantly involve a 'sampling rate' and have
> control system bandwidth limitations.
(which did use pulse techniques) with those of the
missile (which didn't).
> In anycase video grade digital to analog converters can
> are doing billions of calcs/second.
Don't you mean 'analog-to-digital' converters?
Lessee, in 1972, the four-bit Intel 4004 was typically
clocked at 1.2 MHz, while DACs and ADCs boasted multi-
millisecond conversion times. IIRC, the 8008 didn't
arrive until '73 or '74.
>
> > Greater deflection from boresight simply resulted in
> > greater deflection of the control surfaces to correct
> > the error. (Altitude air density - or lack of it -
> > modified the deflection in a direct manner,
>
> Yes, typical autopilot stuff.
>
> > as did
> > a launching-aircraft-computed "English Bias" signal
> > applied prior to launch - but only if a few seconds
> > of target lockon preceeded the launch.)
>
> That I'll need help understanding "English Bias"
pool hall phrase describing the application of
some 'body english' to the cue ball, making it
curve, slow down, or even appear to turn a right
angle before contacting its target ball.
English Bias was a computed term applied to the
missile before launch, loosely describing a flight
path to use between it's initial roll (to flight
attitude) and self-acquisition of the target
aircraft's return.
> > Than came digital: notoriously slower - especially
> > when resolving angle and changing angular-rate info.
> > Not only did the differing outside-world in/out
> > items require sequential sampling; the sampling rate
> > for very high deflections had to increase, thus
> > spending less time on other important attack-missile
> > functions.
>
> Horse and buggy.
it was almost 40 years ago.
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