barts@cyber.Eng.Sun.COM (Bart Smaalders) (08/30/90)
In article <1990Aug30.014817.8794@portia.Stanford.EDU> boehlke@sunrise.stanford.edu (Dan Boehlke) writes:
I see the next breakthrough in robotics being the
introduction of very high accuracy manipulators--
say an order of magnitude (or more) better than
any systems of the 80's. There are plenty of potential
products that simply cannot be assembled today anywhere
outside of a laboratory.
Very high accuracy manipulators are very difficult to design using
today's technologies if they are to be of any general use. The best
(gp commercial) figures I remember from the 80's are approx. .001"
repeatabilty for a _light duty_ electronic assembly robot (working
envelope ~ 1 cubic foot). Building a manipulator _accurate_ (not just
repeatable) to .0001" with a similar envelope would probably imply:
a. All major joints must be linear slides. Rotary motion is ruled
out if arms are of interesting lengths, since accuracy and stiffness
requirements go through the roof as arm length increases. In addition,
kinematic errors due to inaccurate knowledge of zero position are
difficult to reduce at these accuracy levels.
b. Temperature controlled environment and workpieces is a must. Any
sources of heat in the arm itself must also be cooled, or made constant
in effect. A motor mounted in an arm will cause measurable deflections
as the motor heats up and warms the surrounding structure.
c. The tooling (end effectors, part fixturing, etc) costs will be
very high. The assembly cell should be mounted on a isolated granite
slab.
d. Frequent recalibration and verification would be a must - this
would be a rather delicate device.
A interesting starting point for such a manipulator would be to look at
Coordinate Measuring Machines and the technology used to build them.
- Bart
barts@Eng.Sun.Com
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Bart Smaalders Sun Micro Inc | This space available
barts@cyber.sun.com |
loucks@intvax.UUCP (Cliff Loucks) (08/31/90)
From article <141582@sun.Eng.Sun.COM>, by barts@cyber.Eng.Sun.COM (Bart Smaalders):
<
< In article <1990Aug30.014817.8794@portia.Stanford.EDU> boehlke@sunrise.stanford.edu (Dan Boehlke) writes:
<
< I see the next breakthrough in robotics being the
< introduction of very high accuracy manipulators--
<
< Very high accuracy manipulators are very difficult to design using
< today's technologies if they are to be of any general use. The best
< (gp commercial) figures I remember from the 80's are approx. .001"
< repeatabilty for a _light duty_ electronic assembly robot (working
< envelope ~ 1 cubic foot). Building a manipulator _accurate_ (not just
< repeatable) to .0001" with a similar envelope would probably imply:
<
<
< A interesting starting point for such a manipulator would be to look at
< Coordinate Measuring Machines and the technology used to build them.
<
< - Bart
That's essentially what Adept did with their new UltraOne. It's a
four axis gantry on a granite base. Rated accuracy is +-0.0002" in
a working volume of 26" x 26" x 8".
Cliff
--
A society is not civilized until it domesticates the icecube.
Cliff Loucks <=> loucks@intvax.UUCP
Sandia National Labs, Albuquerque, New Mexico
mgsmith@hplabsb.HP.COM (Michael Smith) (08/31/90)
>In article <1990Aug30.014817.8794@portia.Stanford.EDU> boehlke@sunrise.stanford.edu (Dan Boehlke) writes: > > I see the next breakthrough in robotics being the > introduction of very high accuracy manipulators-- > say an order of magnitude (or more) better than > any systems of the 80's. There are plenty of potential > products that simply cannot be assembled today anywhere > outside of a laboratory. > >Very high accuracy manipulators are very difficult to design using >today's technologies if they are to be of any general use. The best >(gp commercial) figures I remember from the 80's are approx. .001" >repeatabilty for a _light duty_ electronic assembly robot (working >envelope ~ 1 cubic foot). One reason humans are capable of high accuracy tasks (putting a chip on a circuit board for example) using a low accuracy manipulator (the human arm) is because of the use of end point control. One looks at what one is doing while doing it. Instead of making a robot more accurate, the loop needs to be closed at the end point using either vision or other sensors. Then only the resolution of the robot is important which of course is much simpler than improving the accuracy of a manipulator. End point control is also advantageous because it can eliminate the need for special linear slide joints, a temperature controlled environment, an isolating granite slab, and frequent recalibration. Mike Smith HP Labs
barts@cyber.Eng.Sun.COM (Bart Smaalders) (09/01/90)
In article <5829@hplabsb.HP.COM> mgsmith@hplabsb.HP.COM (Michael Smith) writes:
One reason humans are capable of high accuracy tasks (putting a chip
on a circuit board for example) using a low accuracy manipulator
(the human arm) is because of the use of end point control. One looks
at what one is doing while doing it. Instead of making a robot more accurate,
the loop needs to be closed at the end point using either vision or other
sensors. Then only the resolution of the robot is important which of course
is much simpler than improving the accuracy of a manipulator.
End point control is also advantageous because it can eliminate the
need for special linear slide joints, a temperature controlled environment,
an isolating granite slab, and frequent recalibration.
True to a point, especially with more conventional accuracy requirements-
but the discussion was about manipulators with ~ .0001" accuracy. This
would imply some very accurate sensors indeed. Unless the sensor system
directly measures the positioning error (eg end-effector to workpiece) as a
differential error , one would still need to calibrate the sensor to the
end-effector. Most vision-based sensor systems would have considerable
trouble at this resolution level, and would have a very small field of view.
A contact-based sensing systems is generally much more accurate, but also is
more delicate, has more "observability" problems and recalibration is more
difficult.
In addition, for most assembly tasks the sensor-based system would be
considerably slower, since the robot would need to come to a stop (with time
to damp out all vibration to well below .0001") at least twice before
attaining the final position.
The original poster was interested in moving this sort of technology out of
the lab...that isolated granite table is still probably required, since the
forklifts running down the corridor outside tend to make the robot shake a
thou or two.... And I wonder how stable the camera and lens are over the 20
degree temp variation we get between the night and day shifts :-).
I'm still not sure what product really requires this level of accuracy in
assembly - can anyone clue me in? It would be interesting to examine the
error budget for the complete system.
- Bart
barts@Eng.Sun.Com
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----------------------------------------------------------------------------------
Bart Smaalders Sun Micro Inc | This space available
barts@cyber.sun.com |
ulrich@grip.cis.upenn.edu (Nathan Ulrich) (09/02/90)
An earlier posting says (sorry I don't have the reference): I see the next breakthrough in robotics being the introduction of very high accuracy manipulators-- say an order of magnitude (or more) better than any systems of the 80's. There are plenty of potential products that simply cannot be assembled today anywhere outside of a laboratory. Dan Boehlke (boehlke@sunrise.stanford.edu) replies: Very high accuracy manipulators are very difficult to design using today's technologies if they are to be of any general use. The best (gp commercial) figures I remember from the 80's are approx. .001" repeatabilty for a _light duty_ electronic assembly robot (working envelope ~ 1 cubic foot). Michael Smith (mgsmith@hplabsb.UUCP) responds: One reason humans are capable of high accuracy tasks (putting a chip on a circuit board for example) using a low accuracy manipulator (the human arm) is because of the use of end point control. One looks at what one is doing while doing it. Instead of making a robot more accurate, the loop needs to be closed at the end point using either vision or other sensors. Then only the resolution of the robot is important which of course is much simpler than improving the accuracy of a manipulator. High precision manufacturing can be handled in two distinct ways. The current automated approach is to use very massive and very stiff machines with linear slides and precise position control. There are grinding operations which are toleranced in millionths of an inch (that's 0.000001") and the machines that can handle this are vibration-isolated and temperature controlled. You will never get near this precision with a serial robot arm--the geometry of cantilevered links connected by revolute joints just does not lend itself to this kind of accuracy. Some small SCARA arms claim repeatability under controlled conditions of 0.001" inch, but this is mostly BS. I challenge anyone to show me a serial robot arm that can obtain accuracy (not repeatability) of better than 0.01" inch outside of controlled testing and calibrating environments, and throughout its claimed payload range. But we've all heard about engravers that could put the Gettysburg Address on the head of a pin by hand. How is this possible, given that the human arm has lousy position control in free space, even in comparison to robot arms? You may claim that the engraver uses a magnifying device and his advanced vision system to perform "endpoint" control, and if robot vision systems were as good we could do the same thing with robot manipulators. Ridiculous! The engraver does the same thing that we do when we write: he grounds his high workspace, low accuracy arm to the workpiece and uses his small workspace high accuracy hand to perform the work. Have you ever tried to write anything small and legible without resting your hand on the paper? "Endpoint" control will not overcome the accuracy limitations of a robot arm, which are related to position sensing, stiction, and stiffness. And any incidental vibration can destabilize such as system--not a problem if the workpiece and the manipulator are in contact. But I'm not a pessimist. I think high-accuracy operations can be realized with current technology and with serial robot manipulators. But not with precise position control and not with "endpoint" control, but with force control. This same low-accuracy human manipulation system can locate its two hands relative to each other in space with enough accuracy to put a 0.9995" peg in a 1.0000" hole. How? By using compliance and force control. This is better than any robot manipulator can accomplish without huge chamfers and the use of a RCC (which is passive compliance). My opinion only. Now tell me why I'm wrong. Nathan Ulrich "If it was easy, someone would have ulrich@grip.cis.upenn.edu done it already..." DoD #0080 - GT750 pilot
mgsmith@hplabsb.HP.COM (Michael Smith) (09/04/90)
In article <141710@sun.Eng.Sun.COM> barts@cyber.Eng.Sun.COM (Bart Smaalders) writes: > >True to a point, especially with more conventional accuracy requirements- >but the discussion was about manipulators with ~ .0001" accuracy. ... >Most vision-based sensor systems would have considerable >trouble at this resolution level, and would have a very small field of view. A system with an accuracy of ~2.5 microns (0.0001") that uses machine vision currently exists. A small field of view is not very important because the features of parts that require that degree of accuracy are usually also very small. After all, everything is relative. > >In addition, for most assembly tasks the sensor-based system would be >considerably slower, since the robot would need to come to a stop (with time >to damp out all vibration to well below .0001") at least twice before >attaining the final position. > The coordinate measurement machine called the Ultra 1 (from Adept) is actually pretty slow because it is always accurate, even it doesn't need to be. For example, when you pick up a small part from a feeder, you don't usually need to know its location very precisely. The Ultra 1 still has to carry its huge granite links around though which slows things down. >The original poster was interested in moving this sort of technology out of >the lab...that isolated granite table is still probably required, since the >forklifts running down the corridor outside tend to make the robot shake a >thou or two.... And I wonder how stable the camera and lens are over the 20 >degree temp variation we get between the night and day shifts :-). > Assembling parts to ~2.5 microns can be very difficult just as producing chips with fine traces is. You wouldn't produce chips on the factory floor because of course a clean room is required. Similarly, a special environment is usually required for high precision assembly. The robot system should also be mechanically isolated from the floor using commercially available dampeners. >I'm still not sure what product really requires this level of accuracy in >assembly - can anyone clue me in? My guess is that anything that requires ~2.5 microns accuracy is highly proprietary so private companies (such as HP) will be very secretive. Electronic devices in general are shrinking so there should be very many applications in the future. Mike Smith HP Labs
mgsmith@hplabsb.HP.COM (Michael Smith) (09/04/90)
In article <29067@netnews.upenn.edu> ulrich@grip.cis.upenn.edu (Nathan Ulrich) writes: > >But I'm not a pessimist. I think high-accuracy operations can be realized >with current technology and with serial robot manipulators. But not with >precise position control and not with "endpoint" control, but with force >control. This same low-accuracy human manipulation system can locate its >two hands relative to each other in space with enough accuracy to put a >0.9995" peg in a 1.0000" hole. How? By using compliance and force control. >This is better than any robot manipulator can accomplish without huge chamfers >and the use of a RCC (which is passive compliance). > >My opinion only. Now tell me why I'm wrong. > I work for a $10 billion a year company and I have never seen an application where such a peg is put into a hole! Such an application is about as realistic as bin picking or stacking legos. It doesn't matter how well a system does something that is not useful. This is a major contention of mine. I believe that a great deal of robotics research is misdirected. Hey, sure such stuff is fun. My first paper was on bin picking and I have given demonstrations on compliance using a force sensor because it was technically challenging and interesting but subsequently I found that it was misguided. I have never seen force compliance used in an actual application, not because it is unavailable, but because it is not as needed as other technologies. We have been collectively doing research in robotics for many years now and they are still not widely used in manufacturing. Why? Because they are not cost effective and because they have been frequently misapplied. We need to really look at what robots should be used for and then work on the problems that specifically prevent them from being used in those applications. Mike "my favorite project was a robotic bartender" Smith HP Labs
ulrich@grip.cis.upenn.edu (Nathan Ulrich) (09/06/90)
In article <29067@netnews.upenn.edu> I write: ...This same low-accuracy human manipulation system can locate its two hands relative to each other in space with enough accuracy to put a 0.9995" peg in a 1.0000" hole.... In article <5832@hplabsb.HP.COM> mgsmith@hplabsb.UUCP (Michael Smith) responds: I work for a $10 billion a year company and I have never seen an application where such a peg is put into a hole! Such an application is about as realistic as bin picking or stacking legos. It doesn't matter how well a system does something that is not useful. You must not have had any exposure to mechanical systems, then, or ever spent *any* time watching a machinist (the size of your company doesn't lend any credibility to your ignorance, by the way). This type of task, which has been generalized into the peg and hole insertion example, is very prevalent in all types of mechanical assembly. Shafts and bearings frequently have this type of tolerance (or tighter). Bearing housings and bearings commonly have interference fits (where the housing bore is *smaller* than the OD of the bearing). Even the relatively simple task of inserting a screw or bolt into a clearance hole is an example of peg and hole insertion, although usually with much lower tolerances. I could spend pages listing the tasks I'm aware of that fall into this category (and I'm only a PhD student, not an employee of a multi-million dollar company :-). I think one reason the peg and hole insertion has been a prevalent watershed for robotic assembly is because it is a good measure of either the precision of the system or its ability to accomplish difficult tasks with force control or compliance. And the tolerance of the fit is a good measuring stick. Systems that can accomplish tight tolerance peg and hole insertion are also considered able to handle different geometries (square key in square hole, etc) although this is not always true. Michael Smith continues: >We have been collectively doing research in robotics for many years now >and they are still not widely used in manufacturing. Why? Because they >are not cost effective and because they have been frequently misapplied. >We need to really look at what robots should be used for and then work >on the problems that specifically prevent them from being used in >those applications. And who will decide what robots "should" be used for? Just because a project doesn't seem to have immediate application does not mean that it hasn't advanced the state of the art and will not eventually find application somewhere. If we only concentrate on immediately-apparent applications then we will fall behind in broader research, and ten years from now the Japanese will be laughing at us (again). This is not to propose that we ignore applications. Although I do think robots are most useful outside of manufacturing, many of the ideas that have been tossed around in conferences on robotics could be applied (and have been, but in Japan or Europe) if the US manufacturing industry was more concerned with long-range planning than short-term profits. Nathan Ulrich "If it was easy, someone would have ulrich@grip.cis.upenn.edu done it already..." DoD #0080 - GT750 pilot
jpexg@rice-chex.ai.mit.edu (John Purbrick) (09/06/90)
In article <5832@hplabsb.HP.COM> mgsmith@hplabsb.UUCP (Michael Smith) writes: >.....I have never seen force >compliance used in an actual application, not because it is unavailable, >but because it is not as needed as other technologies. > >...... >Mike "my favorite project was a robotic bartender" Smith >HP Labs Well, since you lead up to it--I made a system a few years ago which would visit a row of paper cups one at a time and pinch them with a force-sensing servo controlled gripper. It could reliably tell the difference between single cups and double cups (one inside another). The idea was to build a pyramid out of the cups but I never got around to it. Think how this could revolutionize the bartending field! --John Purbrick
josip@ra.src.umd.edu (Josip Loncaric) (09/06/90)
In article <5832@hplabsb.HP.COM> mgsmith@hplabsb.UUCP (Michael Smith) writes: >In article <29067@netnews.upenn.edu> ulrich@grip.cis.upenn.edu (Nathan Ulrich) writes: >> >>But I'm not a pessimist. I think high-accuracy operations can be realized >>with current technology and with serial robot manipulators. But not with >>precise position control and not with "endpoint" control, but with force >>control. This same low-accuracy human manipulation system can locate its >>two hands relative to each other in space with enough accuracy to put a >>0.9995" peg in a 1.0000" hole. How? By using compliance and force control. >>This is better than any robot manipulator can accomplish without huge chamfers >>and the use of a RCC (which is passive compliance). >> >>My opinion only. Now tell me why I'm wrong. >> > >I work for a $10 billion a year company and I have never seen >an application where such a peg is put into a hole! Such an application >is about as realistic as bin picking or stacking legos. It doesn't matter >how well a system does something that is not useful. This is a major >contention of mine. I believe that a great deal of robotics research >is misdirected. Hey, sure such stuff is fun. My first paper was on >bin picking and I have given demonstrations on compliance using a force >sensor because it was technically challenging and interesting but >subsequently I found that it was misguided. I have never seen force >compliance used in an actual application, not because it is unavailable, >but because it is not as needed as other technologies. > >We have been collectively doing research in robotics for many years now >and they are still not widely used in manufacturing. Why? Because they >are not cost effective and because they have been frequently misapplied. >We need to really look at what robots should be used for and then work >on the problems that specifically prevent them from being used in >those applications. > >Mike "my favorite project was a robotic bartender" Smith >HP Labs Well, perhaps you never had to put that size peg into that size hole... but if you never had to deal with closely fit parts, I'd be very surprised. The key point I'd like to make is that in assembling parts with very tight tolerances (finer than the positional accuracy of the robot) you CAN and SHOULD use force-based strategies. Assembling parts by feel is much easier than assembling them without force feedback. This is another example where designing parts so that their shape guides the assembly process through force feedback can be helpful... Anyway, the reason people have not used active force control much have to do with the technical difficulties of attaching this gadget to a commercial robot - it's very hard to get high enough bandwidth - but passive RCC devices are widely used. Your second point (that robotics research is not being directly applied to manufacturing) is well taken. A classic example (from an MIT robotics course) has students designing an elaborate two-handed dishwashing robot, while dishwashing robots can be bought at Sears for $300. So, what manufacturing needs are better manufacturing machines, and not "robots" in the Capek's R.U.R. sense. Many researchers, however, are motivated by the problem of designing machines capable of functioning in unstructured environments. This has little importance in a highly structured production process, but will be of great significance 10-20 years from now, as robot applications become truly widespread. These future robots may also help reduce the complexity of learning production tasks in a factory (less precise programming will be needed). Summary: robotics research serves more goals than just manufacturing. Force feedback (pasive and/or active) is a valuable technique in assembling close fit parts, which should be designed to help the process along. A final comment: HP probably uses robots mainly to stuff PCBs, which may explain why you've never dealt with peg-in-hole type problems. But, if you assemble VCRs, Walkmans, servomotors, etc., this type of problem quickly shows up. -- Josip Loncaric / SRC / U. of Maryland / <josip@ra.src.umd.edu> -------------------------------------------------------------- ! Today's Special: Opinions....$0.02 each ! --------------------------------------------------------------
abg@stc06.ornl.gov (BANGS A L) (09/07/90)
In article <5832@hplabsb.HP.COM> mgsmith@hplabsb.UUCP (Michael Smith) writes: >Mike "my favorite project was a robotic bartender" Smith Well, just thought you might want to know that it has been done. When I worked for Honeybee Robotics, my primary project was the development of just such a beast, using a GMF robot and various bits of automated dispensing equipment. We got some TV coverage, but so far, no nibbles that want to spend money. A couple of talk shows wanted to have the robot on, but it was going to be a real pain to move it to a studio. Alex L. Bangs ---> bangsal@ornl.gov Of course, my opinions are Oak Ridge National Laboratory/CESAR my own darned business... Autonomous Robotic Systems Group
ssridhar@pase60.Convergent.Com (Srinivasan Sridhar) (09/07/90)
During my research student days, we had several robotics projects involving manufacturing and non-manufacturing tasks. Precision was important in all applications. Assembly line robotics required precise positioning of the manipulator. Even sensing required precision positioning (as a result of the sensing). When we conducted industry sponsored projects, the specifications put froth by most industries required accuracy (even the tasks demanded this). For instance, using a manipulator for card assembly, force sensing and positioning would require the system to be capable of micro-movements. Surgical applications would most definitely require extreme positioning. The applications go on and on and on............ ___ sridhar
mgsmith@hplabsb.HP.COM (Michael Smith) (09/07/90)
In article <1990Sep6.202839.15676@cs.utk.edu> bangsal@ornl.gov (BANGS A L) writes: >In article <5832@hplabsb.HP.COM> mgsmith@hplabsb.UUCP (Michael Smith) writes: >>Mike "my favorite project was a robotic bartender" Smith > >Well, just thought you might want to know that it has been done. When I >worked for Honeybee Robotics, my primary project was the development of >just such a beast, using a GMF robot and various bits of automated >dispensing equipment. We got some TV coverage, but so far, no nibbles >that want to spend money. A couple of talk shows wanted to have the >robot on, but it was going to be a real pain to move it to a studio. > We used a robot to sell beer at 100% markup at engineering society events and then we would drink the profits. It was fun. Also got a bit of TV coverage. Develop a system that revolutionizes manufacturing though and you are still a pariah. We have to get away from what people can do and have robots do what we cannot (such as high accuracy assembly). Such projects not being considered as interesting is something we need to overcome. Mike Smith HP Labs
hbg6@citek.mcdphx.mot.com (09/08/90)
In article <5837@hplabsb.HP.COM> mgsmith@hplabsb.UUCP (Michael Smith) writes: > >We have to get away from what people can do and have robots do what we cannot >(such as high accuracy assembly). Such projects not being considered >as interesting is something we need to overcome. > >Mike Smith >HP Labs Not considered interesting by whom? The popular press is still waiting for the 100% accurate robotic lawn mower / window washer. A robotic system which places a spindle in an interference fit hole just dosen't make points in the ratings. If your playing to that audience, don't hold your breath for interest. John
hugh@ria.ccs.uwo.ca (Mr. Hugh Jack) (09/10/90)
I have only briefly noticed the on-going arguments in this column about high accuracy manipulators, and it has reminded me about some discussion I have seen in papers. The cornerstone of the problem can be described as 'Human/Super Human'. The problem typically involves trade offs between high accuracy and high flexibility. As humans we tend to concentrate on accuracy, flexibility, power, or some combination thereof. Many current robotics researcher have attempted to get the best of both. This is not to say that it is not possible, but the best robotics systems we have seen to date (i.e. humans) are never super. Thus, I would like to bravely conclude that the question of which is better or more useful is not the issue. What researchers should be moving towards is a system that is able to use compromises between the different domains. Hugh Jack Graduate Student University of Western Ontario London, Ontario, Canada hugh@engrg.uwo.ca p.s. Anybody who takes these opinions seriously is as twisted as i am.