🚀 go-pugleaf

>On Fri, 27 Feb 2004 05:49:25 -0800, Dr. David Kirkby wrote:
>> A friend of mine has bought a 21-seater coach with the idea of converting
>> this into a motor home. Although it is a bit over the top (OTT) in my
>> opinion, he wants a system that can
>>
>> a) Stabilise the vehicle when parked so that wind does not cause it to
>> move on the suspension. i.e remove the effect of the springs in the
>> suspension.

Such measures are seldom needed on medium duty rigs, since the
suspension generally is so stiff, that wind et al, isn't a significant
factor. On our 18,000 lb Ford chassis, we've never recognized a need
for any kind of stabilizer.

>> b) Level the vehicle if parked on terrain with an incline.

For less than 1% of the cost of hydraulic jacks, a few boards from yer
local lumber company will accomplish the same purpose.

I see where see_my_signature_for_my_real_address@hotmail.com (Dr.
David Kirkby) inquired:

>A friend of mine has bought a 21-seater coach with the idea of
>converting this into a motor home. Although it is a bit over the top
>(OTT) in my opinion, he wants a system that can
>
>a) Stabilise the vehicle when parked so that wind does not cause it to
>move on the suspension. i.e remove the effect of the springs in the
>suspension.
>
>b) Level the vehicle if parked on terrain with an incline.
>
>He has asked me if I can design him a system to do this.

You're not going to like my answer, but here it is:  You should tell
your friend that you don't know how to do it, and that he need to
hire someone with a clue to engineer what he wants.

Will Sill

On Fri, 27 Feb 2004 05:49:25 -0800, Dr. David Kirkby wrote:

> A friend of mine has bought a 21-seater coach with the idea of converting
> this into a motor home. Although it is a bit over the top (OTT) in my
> opinion, he wants a system that can
>
> a) Stabilise the vehicle when parked so that wind does not cause it to
> move on the suspension. i.e remove the effect of the springs in the
> suspension.
>
> b) Level the vehicle if parked on terrain with an incline.
<<..>>
>
> He intends adding two sensors that can check if the vehicle is level in
> two orthogonal (at right angle) directions.
>
> I'd like some advice/guidance from anyone with knowledge of how such
> systems might work - I belive they are available at a high price. Someone
> has pointed out to me the turret on militrary tanks keeps in one
> direction, despite the fact the tank moves on uneven terrain.

I believe the military units are a whole different ball of wax-
gyroscopically stabilized, rather than leveling, but reading on...
>
> My thoughts to date have been
>
> 1) Determine from the angle sensors which of the 4 corners the coach
> needs to be raised. Lower a ram in the corner most needing raising until
> such time as it in contact with the ground with say a 1 degree
> correction in the angle of the coach.
>
> 2) Raise the corner that requires the second most degree of correction
> until there has been a 1 degree change in the coaches angle.
>
> 3) Do likewise for the second and third corners.
>
> At this point each ram should be touching the road surface.
>
> Then repeat the procedure, after which the coach should be level.
>
> Another idea is the dead opposite of this.

First- while commercial systems are indeed expensive, I have doubts that a
system can be prototyped much cheaper. The leader in this type system is
HWH- http://www.hwhcorp.com/ - they have a bunch of downloadable
information on the website.

Their automatic system first lowers the front and rear jacks until they
touch the ground (I *think* they have pressure sensors to do this), then
it will activate the jacks in pairs (to keep from twisting the frame),
raising the lowest point- I'm not sure of the algorithm used, but I think
their sensors do not measure degree of out of level, but rather pick on of
the low spots (front to back, or side to side), level that way, then level
the other direction- IOW, if the right front corner is low, it will raise
the right side until side to side is level, then raise the front, 'til
front to back is level.



--
Chris Bryant
http://bryantrv.com

"Dr. David Kirkby" <see_my_signature_for_my_real_address@hotmail.com> wrote
in message news:c99d2c79.0402270549.3789f98a@posting.google.com...
> A friend of mine has bought a 21-seater coach with the idea of
> converting this into a motor home. Although it is a bit over the top
> (OTT) in my opinion, he wants a system that can
>
> a) Stabilise the vehicle when parked so that wind does not cause it to
> move on the suspension. i.e remove the effect of the springs in the
> suspension.
>
> b) Level the vehicle if parked on terrain with an incline.
>
> He has asked me if I can design him a system to do this. He is quite
> capable of adding hydraulic rams to do the mechanicle work, as he has
> excellent mechanical skills and has built a kit-car and done other
> related items. However, he has asked me to design a control system to
> do this. He wants to push one button and it all work. I'm an
> electronics engineer, with quite a bit of experience of using A/D's,
> D/A's and microcontrollers.
>
> He intends adding two sensors that can check if the vehicle is level
> in two orthogonal (at right angle) directions.
>
> I'd like some advice/guidance from anyone with knowledge of how such
> systems might work - I belive they are available at a high price.
> Someone has pointed out to me the turret on militrary tanks keeps in
> one direction, despite the fact the tank moves on uneven terrain.
>
> My thoughts to date have been
>
> 1) Determine from the angle sensors which of the 4 corners the coach
> needs to be raised. Lower a ram in the corner most needing raising
> until such time as it in contact with the ground with say a 1 degree
> correction in the angle of the coach.
>
> 2) Raise the corner that requires the second most degree of correction
> until there has been a 1 degree change in the coaches angle.
>
> 3) Do likewise for the second and third corners.
>
> At this point each ram should be touching the road surface.
>
> Then repeat the procedure, after which the coach should be level.
>
> Another idea is the dead opposite of this.
>
> a) Raise the corner of the motorhome that is already highest, so
> making the motorhome in a worst position than originally. Then do this
> for the second worst corner. and to this for each corner. This seems
> more robust as an algorithm, but needs longer rams, which cost more.
>
> I have nagging doubts about all these.
>
> Do I need pressure sensors to be certain the rams are indeed touching
> the surface on which this is parked ? What happens if the surface is
> not very hard, and gives a certain amount? What effect would wind have
> on this ?
>
> I don't want to completly lift the motorhome, but likewise I do need
> to be able to remove some of the give in the suspension.
>
First, you are reinventing the wheel here.  There are systems out there.
You could probably get your hands on the design.

One important thing you've left out.  It is possible to overstress and bend
the frame with these "rams".  Most manufacturers have stopped allowing
individual rams to activate but, rather, only allow pairs to function.  Just
a point to remember.

cheers

bob

I read in sci.electronics.design that Dr. David Kirkby <see_my_signature
_for_my_real_address@hotmail.com> wrote (in <c99d2c79.0402270549.3789f98
a@posting.google.com>) about 'System for levelling a motorhome', on Fri,
27 Feb 2004:
>My thoughts to date have been
>
>1) Determine from the angle sensors which of the 4 corners the coach
>needs to be raised. Lower a ram in the corner most needing raising until
>such time as it in contact with the ground with say a 1 degree
>correction in the angle of the coach.

With four points of support, you can get 'rocking' - like a table with a
twisted top or legs of slightly different lengths. With only three
points, you cannot get rocking, and the level adjustments don't
interact. See 'milking stool'. (;-)
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

Will Sill wrote:
> I see where see_my_signature_for_my_real_address@hotmail.com (Dr.
> David Kirkby) inquired:
>
>
>>A friend of mine has bought a 21-seater coach with the idea of
>>converting this into a motor home. Although it is a bit over the top
>>(OTT) in my opinion, he wants a system that can
>>
>>a) Stabilise the vehicle when parked so that wind does not cause it to
>>move on the suspension. i.e remove the effect of the springs in the
>>suspension.
>>
>>b) Level the vehicle if parked on terrain with an incline.
>>
>>He has asked me if I can design him a system to do this.
>
>
> You're not going to like my answer, but here it is:  You should tell
> your friend that you don't know how to do it, and that he need to
> hire someone with a clue to engineer what he wants.
>
> Will Sill

*I* like your answer- succinct, practical and realistic- ask an EE and
you end up with GPS controlled magnetic levitation and fuzzy logic
before you know it-ask an ME and you get a working system- why the heck
would this operation need to be automated anyway?- is it being installed
on tundra or something.

On Fri, 27 Feb 2004 16:10:30 +0100, "Frank Bemelman"
<fbemelx@euronet.invalid.nl> wrote:

>Farmer's milking stools have only one leg. The seat is tied to their
>ass, and they sit on it, using their own two legs as well of course,
>so in fact it's still 3 legs at work ;)

Not in my neck of the woods. I grew up on the farm, and our milking
stools had three legs. Same with the neighbors. Never saw a one-legged
one.

--
Al Balmer
Balmer Consulting
removebalmerconsultingthis@att.net

"John Woodgate" <jmw@jmwa.demon.contraspam.yuk> schreef in bericht
news:B2o171EJK1PAFwQU@jmwa.demon.co.uk...
> I read in sci.electronics.design that Dr. David Kirkby <see_my_signature
> _for_my_real_address@hotmail.com> wrote (in <c99d2c79.0402270549.3789f98
> a@posting.google.com>) about 'System for levelling a motorhome', on Fri,
> 27 Feb 2004:
> >My thoughts to date have been
> >
> >1) Determine from the angle sensors which of the 4 corners the coach
> >needs to be raised. Lower a ram in the corner most needing raising until
> >such time as it in contact with the ground with say a 1 degree
> >correction in the angle of the coach.
>
> With four points of support, you can get 'rocking' - like a table with a
> twisted top or legs of slightly different lengths. With only three
> points, you cannot get rocking, and the level adjustments don't
> interact. See 'milking stool'. (;-)

Farmer's milking stools have only one leg. The seat is tied to their
ass, and they sit on it, using their own two legs as well of course,
so in fact it's still 3 legs at work ;)

--
Thanks, Frank.
(remove 'x' and 'invalid' when replying by email)

Dr. David Kirkby wrote:
> A friend of mine has bought a 21-seater coach with the idea of
> converting this into a motor home. Although it is a bit over the top
> (OTT) in my opinion, he wants a system that can

I'd call that way over the top (WOTT).
>
> a) Stabilise the vehicle when parked so that wind does not cause it to
> move on the suspension. i.e remove the effect of the springs in the
> suspension.

Put some bricks or some wooden 4 by 4 underneath.

>
> b) Level the vehicle if parked on terrain with an incline.
>
> He has asked me if I can design him a system to do this. He is quite
> capable of adding hydraulic rams to do the mechanicle work, as he has
> excellent mechanical skills and has built a kit-car and done other
> related items. However, he has asked me to design a control system to
> do this. He wants to push one button and it all work. I'm an
> electronics engineer, with quite a bit of experience of using A/D's,
> D/A's and microcontrollers.
>
> He intends adding two sensors that can check if the vehicle is level
> in two orthogonal (at right angle) directions.

A safety point: when the sensor becomes disconnected or the
sensor becomes loose, the jacks will try to compensate for that.
Tricky. A possible liablity case too.

>
> [ snip]
>
> I have nagging doubts about all these.

me too.
>
> Do I need pressure sensors to be certain the rams are indeed touching
> the surface on which this is parked ? What happens if the surface is
> not very hard, and gives a certain amount? What effect would wind have
> on this ?

It becomes complicated ...

>
> I don't want to completly lift the motorhome, but likewise I do need
> to be able to remove some of the give in the suspension.

But it'd be possible with it.

Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net

On 27 Feb 2004 05:49:25 -0800,
see_my_signature_for_my_real_address@hotmail.com (Dr. David Kirkby)
wrote:

>A friend of mine has bought a 21-seater coach with the idea of
>converting this into a motor home. Although it is a bit over the top
>(OTT) in my opinion, he wants a system that can
>
<bunch snipped>
Hi,
 It's already been done and probably better then what your friend can
make or you design on short notice.  They are not cheap but there is a
lot involved as you know.  A company called HWH is probably the
biggest and best known.

 Basically, they use four hydraulic jacks a hydraulic pump and matched
length hydraulic lines and an electronic level control device, mounted
in the center of the motor home, and a computer to level the motor
home.  They have two manual and one automatic leveling systems.  Not
all systems use the same parts.  The system is designed that jacks on
the same side always go down together to help prevent twisting of the
frame.  One jack should not be able to raise the motor home by itself.

  The automatic one works on the press of one button.  The way it
works is the leveling device lets the computer know which of the four
sides of the motor home are furthest out of level.  There is a also
controller/display to show the operator what is happening.  The
operator can over ride the computer and do it manually using this
controller/display.   The two jacks on this low side are then lowered
together until that side is level.  Then if one of the other sides are
not level the jacks on that side are lowered.  It keeps going like
this until the computer and level controller are satisfied the coach
is level.  It then shuts off.  Usually takes about a minute or so.
Longer if on really un level ground. The computer and level sensor
will also determine if the motor home is to far out of level for the
system to work and tell you if it is.

 The manual ones basically work the same way but the operator takes
the place of the computer and presses the buttons. On the manual
system this display/controller tells the operator which side to raise
or lower by using lights to show which side is low.

 Your trying to reinvent the wheel here.  But good luck maybe you can
do it cheaper and better.  If you can't do both it's not worth it :)

Take care and Happy Inventing...


RichA
"We Get To Soon Olde and To Late Smart"

Here are to groups about bus conversion:
http://groups.yahoo.com/group/schoolbusconversionuts/
http://www.yahoogroups.com/group/fotr

There are some others that are related to specific bus types but they might
be able to help, do a search in yahoo groups for < RTS > < MCI > <Bus> you
find some help in one of those.

At the schoolbus site, is a guy named Ben Rosander who has written several
book on the subject.

Good Luck,
Byrd


"Dr. David Kirkby" <see_my_signature_for_my_real_address@hotmail.com> wrote
in message news:c99d2c79.0402270549.3789f98a@posting.google.com...
> A friend of mine has bought a 21-seater coach with the idea of
> converting this into a motor home. Although it is a bit over the top
> (OTT) in my opinion, he wants a system that can
>
> a) Stabilise the vehicle when parked so that wind does not cause it to
> move on the suspension. i.e remove the effect of the springs in the
> suspension.
>
> b) Level the vehicle if parked on terrain with an incline.
>
> He has asked me if I can design him a system to do this. He is quite
> capable of adding hydraulic rams to do the mechanicle work, as he has
> excellent mechanical skills and has built a kit-car and done other
> related items. However, he has asked me to design a control system to
> do this. He wants to push one button and it all work. I'm an
> electronics engineer, with quite a bit of experience of using A/D's,
> D/A's and microcontrollers.
>
> He intends adding two sensors that can check if the vehicle is level
> in two orthogonal (at right angle) directions.
>
> I'd like some advice/guidance from anyone with knowledge of how such
> systems might work - I belive they are available at a high price.
> Someone has pointed out to me the turret on militrary tanks keeps in
> one direction, despite the fact the tank moves on uneven terrain.
>
> My thoughts to date have been
>
> 1) Determine from the angle sensors which of the 4 corners the coach
> needs to be raised. Lower a ram in the corner most needing raising
> until such time as it in contact with the ground with say a 1 degree
> correction in the angle of the coach.
>
> 2) Raise the corner that requires the second most degree of correction
> until there has been a 1 degree change in the coaches angle.
>
> 3) Do likewise for the second and third corners.
>
> At this point each ram should be touching the road surface.
>
> Then repeat the procedure, after which the coach should be level.
>
> Another idea is the dead opposite of this.
>
> a) Raise the corner of the motorhome that is already highest, so
> making the motorhome in a worst position than originally. Then do this
> for the second worst corner. and to this for each corner. This seems
> more robust as an algorithm, but needs longer rams, which cost more.
>
> I have nagging doubts about all these.
>
> Do I need pressure sensors to be certain the rams are indeed touching
> the surface on which this is parked ? What happens if the surface is
> not very hard, and gives a certain amount? What effect would wind have
> on this ?
>
> I don't want to completly lift the motorhome, but likewise I do need
> to be able to remove some of the give in the suspension.
>
> Dave kirkby

I read in sci.electronics.design that Stan Birch <birch999@hotmail.com>
wrote (in <403f8173.18879468@news.netrover.com>) about 'System for
levelling a motorhome', on Fri, 27 Feb 2004:

>Such measures are seldom needed on medium duty rigs, since the
>suspension generally is so stiff, that wind et al, isn't a significant
>factor. On our 18,000 lb Ford chassis, we've never recognized a need for
>any kind of stabilizer.

Up to what wind speed?
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

Check these guys out. You only need to mount each unit and run power
to it, no pressure lines to run.
http://www.bigfootleveler.com

Tom



On 27 Feb 2004 05:49:25 -0800,
see_my_signature_for_my_real_address@hotmail.com (Dr. David Kirkby)
wrote:

>A friend of mine has bought a 21-seater coach with the idea of
>converting this into a motor home. Although it is a bit over the top
>(OTT) in my opinion, he wants a system that can
>
>a) Stabilise the vehicle when parked so that wind does not cause it to
>move on the suspension. i.e remove the effect of the springs in the
>suspension.
>
>b) Level the vehicle if parked on terrain with an incline.
>
>He has asked me if I can design him a system to do this. He is quite
>capable of adding hydraulic rams to do the mechanicle work, as he has
>excellent mechanical skills and has built a kit-car and done other
>related items. However, he has asked me to design a control system to
>do this. He wants to push one button and it all work. I'm an
>electronics engineer, with quite a bit of experience of using A/D's,
>D/A's and microcontrollers.
>
>He intends adding two sensors that can check if the vehicle is level
>in two orthogonal (at right angle) directions.
>
>I'd like some advice/guidance from anyone with knowledge of how such
>systems might work - I belive they are available at a high price.
>Someone has pointed out to me the turret on militrary tanks keeps in
>one direction, despite the fact the tank moves on uneven terrain.
>
>My thoughts to date have been
>
>1) Determine from the angle sensors which of the 4 corners the coach
>needs to be raised. Lower a ram in the corner most needing raising
>until such time as it in contact with the ground with say a 1 degree
>correction in the angle of the coach.
>
>2) Raise the corner that requires the second most degree of correction
>until there has been a 1 degree change in the coaches angle.
>
>3) Do likewise for the second and third corners.
>
>At this point each ram should be touching the road surface.
>
>Then repeat the procedure, after which the coach should be level.
>
>Another idea is the dead opposite of this.
>
>a) Raise the corner of the motorhome that is already highest, so
>making the motorhome in a worst position than originally. Then do this
>for the second worst corner. and to this for each corner. This seems
>more robust as an algorithm, but needs longer rams, which cost more.
>
>I have nagging doubts about all these.
>
>Do I need pressure sensors to be certain the rams are indeed touching
>the surface on which this is parked ? What happens if the surface is
>not very hard, and gives a certain amount? What effect would wind have
>on this ?
>
>I don't want to completly lift the motorhome, but likewise I do need
>to be able to remove some of the give in the suspension.
>
>Dave kirkby

"Dr. David Kirkby"
<see_my_signature_for_my_real_address@hotmail.com> wrote in
message news:c99d2c79.0402270549.3789f98a@posting.google.com...
: A friend of mine has bought a 21-seater coach with the idea of
: converting this into a motor home. Although it is a bit over the
top
: (OTT) in my opinion, he wants a system that can
:
: a) Stabilize the vehicle when parked so that wind does not cause
it to
: move on the suspension. i.e remove the effect of the springs in
the
: suspension.
:
: b) Level the vehicle if parked on terrain with an incline.
:
Just stiffen the suspension and use chocks for leveling.
Air boost shocks will take a lot of flex out and provide some
lift.
While the entire task can be done.  There seems no point.

"Alan Balmer" <albalmer@att.net> schreef in bericht
news:2cjv309broq36dch4a5tdhqse91ls4aacm@4ax.com...
> On Fri, 27 Feb 2004 16:10:30 +0100, "Frank Bemelman"
> <fbemelx@euronet.invalid.nl> wrote:
>
> >Farmer's milking stools have only one leg. The seat is tied to their
> >ass, and they sit on it, using their own two legs as well of course,
> >so in fact it's still 3 legs at work ;)
>
> Not in my neck of the woods. I grew up on the farm, and our milking
> stools had three legs. Same with the neighbors. Never saw a one-legged
> one.

Here in the Netherlands the farmers used 1 legged stools. Not anymore
of course, it's all milking machines and even milking robots these days.


--
Thanks, Frank.
(remove 'x' and 'invalid' when replying by email)

"Dr. David Kirkby" <see_my_signature_for_my_real_address@hotmail.com> wrote
in message
> Dave kirkby

First off, go to

http://www.bigconcreteblocksRus.com

and give them the general dimensions of your motor home.

Then contact

http://www.us.gov.army

and request a big helicopter.

Job done.

DNA

Don wrote:

> I thought one legged stools had been outlawed by OSHA.  If not, they
> should be.  They're dangerous.
>
> Don

Particularly if you strap it on your ass upside down. Probably should
have a pictorial warning label at least. An upside down "T" in a red
circle with a red diagonal slash.

--
bill
Theory don't mean squat if it don't work.

Frank Bemelman wrote:
>
> Farmer's milking stools have only one leg. The seat is tied to their
> ass, and they sit on it, using their own two legs as well of course,
> so in fact it's still 3 legs at work ;)
>
I thought one legged stools had been outlawed by OSHA.  If not, they
should be.  They're dangerous.

Don

On Fri, 27 Feb 2004 17:23:30 GMT, RichA <richatpa*nospam*@epix.net>
wrote:

>On 27 Feb 2004 05:49:25 -0800,
>see_my_signature_for_my_real_address@hotmail.com (Dr. David Kirkby)
>wrote:
>
>>A friend of mine has bought a 21-seater coach with the idea of
>>converting this into a motor home. Although it is a bit over the top
>>(OTT) in my opinion, he wants a system that can
>>

>
> Your trying to reinvent the wheel here.  But good luck maybe you can
>do it cheaper and better.  If you can't do both it's not worth it :)
>
>Take care and Happy Inventing...
>
> 
>RichA
>"We Get To Soon Olde and To Late Smart"

and don't forget it has to be tied into the the ignition and
transmission so if you try to drive off they'll retract.  Can't just
tie it into the ignition in case you want to run the engine to
recharge batteries.

All in all the already manufactured ones are cheaper than buy all the
pieces and building your one.

Jon

===============================================
                   Jon Griffin
          Oliver, BC      Cottage Grove, OR
              USN(ret) FMCA# F257439
===============================================

"Dr. David Kirkby" <see_my_signature_for_my_real_address@hotmail.com> wrote
in message news:c99d2c79.0402270549.3789f98a@posting.google.com...
> A friend of mine has bought a 21-seater coach with the idea of
> converting this into a motor home. Although it is a bit over the top
> (OTT) in my opinion, he wants a system that can
>
> a) Stabilise the vehicle when parked so that wind does not cause it to
> move on the suspension. i.e remove the effect of the springs in the
> suspension.
>
> b) Level the vehicle if parked on terrain with an incline.
>
> He has asked me if I can design him a system to do this. He is quite
> capable of adding hydraulic rams to do the mechanicle work, as he has
> excellent mechanical skills and has built a kit-car and done other
> related items. However, he has asked me to design a control system to
> do this. He wants to push one button and it all work. I'm an
> electronics engineer, with quite a bit of experience of using A/D's,
> D/A's and microcontrollers.
>
> He intends adding two sensors that can check if the vehicle is level
> in two orthogonal (at right angle) directions.
>
> I'd like some advice/guidance from anyone with knowledge of how such
> systems might work - I belive they are available at a high price.
> Someone has pointed out to me the turret on militrary tanks keeps in
> one direction, despite the fact the tank moves on uneven terrain.
>
> My thoughts to date have been
>
> 1) Determine from the angle sensors which of the 4 corners the coach
> needs to be raised. Lower a ram in the corner most needing raising
> until such time as it in contact with the ground with say a 1 degree
> correction in the angle of the coach.
>
> 2) Raise the corner that requires the second most degree of correction
> until there has been a 1 degree change in the coaches angle.
>
> 3) Do likewise for the second and third corners.
>
> At this point each ram should be touching the road surface.
>
> Then repeat the procedure, after which the coach should be level.
>
> Another idea is the dead opposite of this.
>
> a) Raise the corner of the motorhome that is already highest, so
> making the motorhome in a worst position than originally. Then do this
> for the second worst corner. and to this for each corner. This seems
> more robust as an algorithm, but needs longer rams, which cost more.
>
> I have nagging doubts about all these.
>
> Do I need pressure sensors to be certain the rams are indeed touching
> the surface on which this is parked ? What happens if the surface is
> not very hard, and gives a certain amount? What effect would wind have
> on this ?
>
> I don't want to completly lift the motorhome, but likewise I do need
> to be able to remove some of the give in the suspension.
>
> Dave kirkby

One of the lads here in Oz has come up with a system, no electronics as I
understand. AFAIK the rams are all fed from a common reservoir  and thus
each moves until it hits the deck and I guess a coupla pounds are then added
to take the load.


--
Regards ........ Rheilly Phoull

"Dr. David Kirkby" wrote:
>
> A friend of mine has bought a 21-seater coach with the idea of
> converting this into a motor home. Although it is a bit over the top
> (OTT) in my opinion, he wants a system that can
>
> a) Stabilise the vehicle when parked so that wind does not cause it to
> move on the suspension. i.e remove the effect of the springs in the
> suspension.
>
> b) Level the vehicle if parked on terrain with an incline.
>
> He has asked me if I can design him a system to do this. He is quite
> capable of adding hydraulic rams to do the mechanicle work, as he has
> excellent mechanical skills and has built a kit-car and done other
> related items. However, he has asked me to design a control system to
> do this. He wants to push one button and it all work. I'm an
> electronics engineer, with quite a bit of experience of using A/D's,
> D/A's and microcontrollers.
>
> He intends adding two sensors that can check if the vehicle is level
> in two orthogonal (at right angle) directions.
>
> I'd like some advice/guidance from anyone with knowledge of how such
> systems might work - I belive they are available at a high price.
> Someone has pointed out to me the turret on militrary tanks keeps in
> one direction, despite the fact the tank moves on uneven terrain.
>
> My thoughts to date have been
>
> 1) Determine from the angle sensors which of the 4 corners the coach
> needs to be raised. Lower a ram in the corner most needing raising
> until such time as it in contact with the ground with say a 1 degree
> correction in the angle of the coach.
>
> 2) Raise the corner that requires the second most degree of correction
> until there has been a 1 degree change in the coaches angle.
>
> 3) Do likewise for the second and third corners.
>
> At this point each ram should be touching the road surface.
>
> Then repeat the procedure, after which the coach should be level.
>
> Another idea is the dead opposite of this.
>
> a) Raise the corner of the motorhome that is already highest, so
> making the motorhome in a worst position than originally. Then do this
> for the second worst corner. and to this for each corner. This seems
> more robust as an algorithm, but needs longer rams, which cost more.
>
> I have nagging doubts about all these.
>
> Do I need pressure sensors to be certain the rams are indeed touching
> the surface on which this is parked ? What happens if the surface is
> not very hard, and gives a certain amount? What effect would wind have
> on this ?
>
> I don't want to completly lift the motorhome, but likewise I do need
> to be able to remove some of the give in the suspension.
>
> Dave kirkby

  Perhaps an atom bomb could be used to solve all of the problems in a
definitive manner.

On Fri, 27 Feb 2004 05:49:25 +0000, Dr. David Kirkby wrote:

> A friend of mine has bought a 21-seater coach with the idea of
> converting this into a motor home. Although it is a bit over the top
> (OTT) in my opinion, he wants a system that can
>
>
Sounds way OTT to me. I'm sure I wouldn't do it this way. If I did this at
all, I would put in seperate manual controls for all four corners and do
the whole stabilization thing myself, using small bubble-levels for
sensors.

> a) Stabilise the vehicle when parked so that wind does not cause it to
> move on the suspension. i.e remove the effect of the springs in the
> suspension.
>
> b) Level the vehicle if parked on terrain with an incline.
>
> He has asked me if I can design him a system to do this. He is quite
> capable of adding hydraulic rams to do the mechanicle work, as he has
> excellent mechanical skills and has built a kit-car and done other
> related items. However, he has asked me to design a control system to do
> this. He wants to push one button and it all work. I'm an electronics
> engineer, with quite a bit of experience of using A/D's, D/A's and
> microcontrollers.
>
> He intends adding two sensors that can check if the vehicle is level in
> two orthogonal (at right angle) directions.

There are micro-macnined accelerometers out there, nowadays. I seem to
remember Crossbow as a manufacturer, in the US. (Not sure where you are.)
I think Analog Devices has them, too. This should be able to provide level
sensing feedback.


> I'd like some advice/guidance from anyone with knowledge of how such
> systems might work - I belive they are available at a high price.
> Someone has pointed out to me the turret on militrary tanks keeps in one
> direction, despite the fact the tank moves on uneven terrain.
>
>
Yeah, but they would have to use three-axis gyros (or similar
micro-machined devices) and possibly three-axis accelerometers, too, all
with fast update rates. This is overkill for your application.

> My thoughts to date have been
>
> 1) Determine from the angle sensors which of the 4 corners the coach
> needs to be raised. Lower a ram in the corner most needing raising until
> such time as it in contact with the ground with say a 1 degree
> correction in the angle of the coach.
>
>
You don't want angle sensors, you want a two-axis accelerometer installed
perfectly level, or at an offset to perfectly compensate for its own bias.

> 2) Raise the corner that requires the second most degree of correction
> until there has been a 1 degree change in the coaches angle.
>
> 3) Do likewise for the second and third corners.
>
> At this point each ram should be touching the road surface.
>
> Then repeat the procedure, after which the coach should be level.
>
> Another idea is the dead opposite of this.
>
> a) Raise the corner of the motorhome that is already highest, so making
> the motorhome in a worst position than originally. Then do this for the
> second worst corner. and to this for each corner. This seems more robust
> as an algorithm, but needs longer rams, which cost more.
>
>
>
I think this is the better algorithm. It could probably allow you to
dispense with the pressure sensor. Then again, you might get thrown off if
you get a gust of wind while you are lowering one of the rams. This might
trick the system into thinking the ram has touched down when it hasn't.
Also, I should mention that I have no experience with this type of
application.

> I have nagging doubts about all these.
>
> Do I need pressure sensors to be certain the rams are indeed touching
> the surface on which this is parked ? What happens if the surface is not
> very hard, and gives a certain amount? What effect would wind have on
> this ?
>
>
As I mentioned above, you may indeed need pressure sensors. They would
seem to provide the most reliable detection of when a ram touches down.
However, since any sensor can fail, I would probably put some logic in
there to make sure that if the accelerometer(s) detect(s) a large change in
tilt, you turn off the ram and signal a fault, even if the pressure sensor
is reading a low pressure.

> I don't want to completly lift the motorhome, but likewise I do need to
> be able to remove some of the give in the suspension.

It might be nice to be able to completely lift the motorhome. I wouldn't
want to jack one up manually to change a tire.


> Dave kirkby

Good luck!

--Mac

"Dr. David Kirkby" wrote:
>
> A friend of mine has bought a 21-seater coach with the idea of
> converting this into a motor home. Although it is a bit over the top
> (OTT) in my opinion, he wants a system that can
>
> a) Stabilise the vehicle when parked so that wind does not cause it to
> move on the suspension. i.e remove the effect of the springs in the
> suspension.

Any jacking system will accomplish this. Once the bus is supported by a
set of stiff jacks, movement will be minimized.

> b) Level the vehicle if parked on terrain with an incline.
>
> He has asked me if I can design him a system to do this. He is quite
> capable of adding hydraulic rams to do the mechanicle work, as he has
> excellent mechanical skills and has built a kit-car and done other
> related items. However, he has asked me to design a control system to
> do this. He wants to push one button and it all work. I'm an
> electronics engineer, with quite a bit of experience of using A/D's,
> D/A's and microcontrollers.

You'll need pressure (or load) sensors on each leg and two nested
control loop levels. The inner loop will regulate the pressure in each
ram to maintain an equal load distribution. Two outer control loops (one
for the roll axis and one for the pitch axis) will provide error signals
from the tilt sensors to bias the load control loops and achieve the
leveling function.

The algorithm should guarantee that each leg will pick up a minimum
amount of load in the event the bus is initially parked level so that
the equal load criteria isn't satisfied until some minimum amount of
load is taken off the bus springs.

The system will also need some sort of limit switches so it can detect a
situation in which there is insufficient ram travel available to satisfy
the leveling solution.

If the rams have sufficient travel, you might also want to implement a
angular limit safety switch (a pendulum hanging inside a contact ring of
the appropriate size) so that when the system tips the bus close to its
limits of stability, the whole thing is shut down. Needless to say, this
feature shouldn't depend upon the microprocessor to work. The tilt
sensors can probably judge whether the incline is beyond hope of
leveling before entering the leveling algorithm, but the safety system
should shut everything (including the pump) down in the event the rest
of the system goes brain-dead.


--
Paul Hovnanian     mailto:Paul@Hovnanian.com
note to spammers:  a Washington State resident
------------------------------------------------------------------
professor; n, One who talks in someone else's sleep.

Fred Bloggs <nospam@nospam.com> wrote in message news:<404127D2.7010901@nospam.com>...
> Paul Hovnanian P.E. wrote:
> > "Dr. David Kirkby" wrote:
> >
> >>A friend of mine has bought a 21-seater coach with the idea of
> >>converting this into a motor home. Although it is a bit over the top
> >>(OTT) in my opinion, he wants a system that can
> >>
> >>a) Stabilise the vehicle when parked so that wind does not cause it to
> >>move on the suspension. i.e remove the effect of the springs in the
> >>suspension.
> >
> >
> > Any jacking system will accomplish this. Once the bus is supported by a
> > set of stiff jacks, movement will be minimized.
> >
> >
> >>b) Level the vehicle if parked on terrain with an incline.
> >>
> >>He has asked me if I can design him a system to do this. He is quite
> >>capable of adding hydraulic rams to do the mechanicle work, as he has
> >>excellent mechanical skills and has built a kit-car and done other
> >>related items. However, he has asked me to design a control system to
> >>do this. He wants to push one button and it all work. I'm an
> >>electronics engineer, with quite a bit of experience of using A/D's,
> >>D/A's and microcontrollers.
> >
> >
> > You'll need pressure (or load) sensors on each leg and two nested
> > control loop levels. The inner loop will regulate the pressure in each
> > ram to maintain an equal load distribution. Two outer control loops (one
> > for the roll axis and one for the pitch axis) will provide error signals
> > from the tilt sensors to bias the load control loops and achieve the
> > leveling function.
> >
> > The algorithm should guarantee that each leg will pick up a minimum
> > amount of load in the event the bus is initially parked level so that
> > the equal load criteria isn't satisfied until some minimum amount of
> > load is taken off the bus springs.
> >
> > The system will also need some sort of limit switches so it can detect a
> > situation in which there is insufficient ram travel available to satisfy
> > the leveling solution.
> >
> > If the rams have sufficient travel, you might also want to implement a
> > angular limit safety switch (a pendulum hanging inside a contact ring of
> > the appropriate size) so that when the system tips the bus close to its
> > limits of stability, the whole thing is shut down. Needless to say, this
> > feature shouldn't depend upon the microprocessor to work. The tilt
> > sensors can probably judge whether the incline is beyond hope of
> > leveling before entering the leveling algorithm, but the safety system
> > should shut everything (including the pump) down in the event the rest
> > of the system goes brain-dead.
> >
> >
>
> Good idea- this sounds like a small handful of 741's driving the whole
> error bridge thing to zero.

Not a good idea. This could activate while driving, or become faulty
and partially activate while driving. If the person building it doesnt
understand about error trees and the dangers and reliability issues in
auto environments they shouldnt be building something like this.

In this country it would also make your vehicle uninsurable.

Regards, NT

Paul Hovnanian P.E. wrote:
> "Dr. David Kirkby" wrote:
>
>>A friend of mine has bought a 21-seater coach with the idea of
>>converting this into a motor home. Although it is a bit over the top
>>(OTT) in my opinion, he wants a system that can
>>
>>a) Stabilise the vehicle when parked so that wind does not cause it to
>>move on the suspension. i.e remove the effect of the springs in the
>>suspension.
>
>
> Any jacking system will accomplish this. Once the bus is supported by a
> set of stiff jacks, movement will be minimized.
>
>
>>b) Level the vehicle if parked on terrain with an incline.
>>
>>He has asked me if I can design him a system to do this. He is quite
>>capable of adding hydraulic rams to do the mechanicle work, as he has
>>excellent mechanical skills and has built a kit-car and done other
>>related items. However, he has asked me to design a control system to
>>do this. He wants to push one button and it all work. I'm an
>>electronics engineer, with quite a bit of experience of using A/D's,
>>D/A's and microcontrollers.
>
>
> You'll need pressure (or load) sensors on each leg and two nested
> control loop levels. The inner loop will regulate the pressure in each
> ram to maintain an equal load distribution. Two outer control loops (one
> for the roll axis and one for the pitch axis) will provide error signals
> from the tilt sensors to bias the load control loops and achieve the
> leveling function.
>
> The algorithm should guarantee that each leg will pick up a minimum
> amount of load in the event the bus is initially parked level so that
> the equal load criteria isn't satisfied until some minimum amount of
> load is taken off the bus springs.
>
> The system will also need some sort of limit switches so it can detect a
> situation in which there is insufficient ram travel available to satisfy
> the leveling solution.
>
> If the rams have sufficient travel, you might also want to implement a
> angular limit safety switch (a pendulum hanging inside a contact ring of
> the appropriate size) so that when the system tips the bus close to its
> limits of stability, the whole thing is shut down. Needless to say, this
> feature shouldn't depend upon the microprocessor to work. The tilt
> sensors can probably judge whether the incline is beyond hope of
> leveling before entering the leveling algorithm, but the safety system
> should shut everything (including the pump) down in the event the rest
> of the system goes brain-dead.
>
>

Good idea- this sounds like a small handful of 741's driving the whole
error bridge thing to zero.