GorakTwo:
GorakTwo will NOT be offered as a product, unless investors see a benefit to reach the final goal.
GorakTwo has two fractional horsepower DC motors, one running forward, and the other running in reverse.
Running at variable speeds and constant torque. The two motors will power the entire machine, and run
continuously, since a DC motor running without a load, will draw very little power. The uniqueness to the GorakTwo
design is the power transmission system. That is now very close to being tested and ready for use.
With this approach the DC motor torque and power could be delivered to any body limb. The entire
power could be delivered to just one limb, such as an index finger. To achieve the smooth mobility that this
machine would have, the power transmission system would distribute the power in measured controlled
amounts. GorakTwo is to prove and create a reliable, repeatable design, that would minimize the investment
risk to continue to the next level. The reasoning is that if there is a GorakOne and a GorakTwo, then there
will be a GorakThree and so forth, to the final goal, GorakTen. This model would be a complete, anatomically
correct humanoid. This would be the ultimate of the Gorak series, but not the ultimate destination for
sbcRobotics. GorakTen is the term that is often used to mean the final humanoid. GorakTwo at this time will
also use the same hands as GorakOne, and the torsoHead. It will also use the same head, as theTorsoHead
GorakTwo is not designed to do production work. It cannot place parts in place, over and over with high precision.
Such as production robots will do. It's designed to perforn like a human. It has to see when it picks up, such as
a cup of drink, every time. Such as a human does.
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Breaks and Clutches:
The following show some past and current efforts to build efficient clutches and breaks for power
transmission and control. This is the last of the design efforts to put GorakTwo into controlled motion.
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This clutch&break photo shows this design effort. It worked as designed. It accomplished a positive engagement.
Everything was taken into consideration. Including the "inertia factor". The precision engagement
was tripped by a 200ms pulse. Once engaged it would stay positively engaged, until another 200ms would
disengage it. The engagement/disengagement mechanism would use the power from the input shaft to power
the engagement/disengagement action. This mechanism used mechanical hysterises for a reliable engagement
every time. In this photo the input shaft was turning at near 10 revs per second. The engagement action
is tripped by the mechanism with the coil in view. This mechanism is large compared to the actual one,
which is smaller than a penny.
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This photo shows the mechanical input power for this test. A dremel tool, since it offers a very controlled
rotational speed. The long brass wires are for detecting the position of the drive shaft. The longest wire
is the common ground. Since there are two brass inputs, the shaft test software can determined four possible
shaft positions.
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This photo shows the prototype engagementClutch in a stopped state, showing the simple engagement
mechanism, engaged.
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The same prototype engagementClutch in a stopped state, showing the simple engagement
mechanism, disengaged. The power to engage and disengage the clutch comes from the input
drive shaft. With this prototype hybrid clutch design, it takes less power to engage than
it takes to disengage when driving a load. The extra brass pieces are just for testing the
prototype design.
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Static belt drive coefficient of friction test. The required coefficient of friction for this belt drive is
inversely proportional to the clutch RPM.
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This photo shows GorakTwo's ribcage partially assembled, with one drive shaft. At
this stage of the design the drive is showing one "clutch wheel". The finished drive
shaft will eventually have twenty clutch wheels, and four drive shafts. Each with
twenty clutch wheels.
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This photo also shows the PC parallel printer port connector. Since this is what was used to control
this test and other tests. The PC control software needs to know where the position of the shaft is at all times to reliably
control the engagement/disengagement action. The control software is of course running is an MSDos environment.
There was no need for a GigaHertz speed desktop running an OS that used gillions of bytes of memory. In other
words, no Windows OS.
This photo shows the electrical control for most of the design test efforts. In the end, this design
failed. Inertia was the defeat. It was included in the input mechanical design, but left out of the
output. The design engaged a shaft turning at 10 revolutions/sec to a loaded shaft that was totally
standing still. It was like hitting a brick wall. This design might work in situations were the input
shaft is moving very slow. But the reaction time would be slow since the engagement action comes from
input shaft power rotation.
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This photo shows another approach. This one worked as designed. The input shaft was running at over
1000rpm. This engagement was smooth and efficient. Because the holding power was low, a higher RPM
had to be used. In this photo, the yellow and black alligator clips, are the input shaft position. This
design was not suitable, since it took too long to engage and disengage. In this photo, the design is
complete, with transmission and differential. The total height is 3/4" and the diameter is 2"x1/4".
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This approach did not use the power of the input shaft for engagement, and instead powered by the driver.
The initial engagement current was higher, than the holding current. For as long the coils are energized
there will be an effecient coupling. But removing the holding current will continue to hold due to the
builtin magnetic hysterises as designed for when a light coupling was needed. To completely disengage,
the coils, a demagnetizing current was used since the coils were powered by an H-bridge, The trick to this
design is a shaft(input) within a shaft(output) within a shaft(differential).
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This photo shows the latest try. This prototype design approach was never put to the spin test. Since it was
decided that it was not simple enough and it had too many moving parts. It's about a 1/4" thick. It
also had too much mass and therefore too much inertia. But its performance was expected to be better
than the rest. This approach could be used either as a clutch or break. In this photo, the input
control is the 10gram weight holding a 50gram weight. In this photo the 50g weight represents the input
to the transmission gear train. This one too used the shaft within a shaft within a shaft.
To provide the 10g force a MicroSizer Motor was going to be used. This design was abandoned for a better
design, that's next, simple with less moving parts, less mass, more efficient and a better transfer
function. For GorakTwo to be put in motion, it needs two of these for every pseudo-muscle, and there's two
pseudo-muscles for every limb, just as humans have, working opposite of each other.
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This view shows a more detail construction and also shows the miniature DC motor mounted using a fuse clip.
Also in this photo is the improved and simplified gear transmission/differential mechanism. The hybrid gear set was
made from a mold made from TAP plastics, SiliconeRTV mold making coupound and the casting was made from a
polyurethane.
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This photo shows the side view of the same miniature clutch/break design. From the blue, downwards should
not be more than a 1/4" in thickness. The miniature DC motor meets the spec, but not the rest of the design.
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The miniature DC motor is part of a series of motors for the MicroSizer ultra miniature RC cars. These
motors are also available as the "cellPhone vibrating" motors. Also available from Solarbotics.com. The
motors in this photo, were available from HobbyTown USA and cost twice a much as the Solarbotics motors.
However the motor, and gears were bought at the local HobbyTown, and there was no shipping charges or
waiting for delivery.
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The Body:
This photo shows the construction of GorakTwo's body. This photo is showing the hip joint. When this
photo was taken, the machine was still under construction. As of this writing, this hip joint is
complete and so is the rest of the body. This photo does not show every detail, so as not to
compromise any proprietary confidential information.
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This photo shows the further construction of
GorakTwo's body. This photo is showing the hip internals.
The lettering points to the pulleys that lead to the shoulder and arm. Above the lettering is the place
for the power transmission, not shown is this photo, since it's confidential. This photo shows that the
build is complicated, but of course it's not, it's just out of context. The pink yarn is used since it's
easy to see. But the final will use the right steel cabling. These photos were taken during its construction,
since then the machine has been close to finished.
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This photo shows the construction of the waist and hip. In this photo it's still incomplete. However
by the time of this writing, this has been completed. Again this photo does not show everything, to
protect the patent applications.
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This photo shows the construction of the waist and hip. In this photo it's still incomplete. However
by the time of this writing, this has been completed. Pink yarn was used for more than one purpose.
Again this photo does not show everything, to protect the patent applications.
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| More details and pics coming soon. Web page last updated; Feb 20, 2007.
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| Copyright © 2003-2007 by sbcRobotics, ALL RIGHTS RESERVED
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