hydrolic arm
TRANSCRIPT
Hydraulic ARM
Contents
1. Objective
2. Introduction
3. DC motor
4. 8051
5. Conclusions
INTRODUCTION
Objective: - The main objective of this project to build a unique kind of robotic
algorithm to achieve a new kind of approachability in the field of robotics. The
Robotic arm is one of those types of different view for automation in machines.
These robots are designed to clean or pull up & down any kind obstructions
Abstract : The Robotic Manipulator Arm extends the flexibility of workstations by
transporting material more efficiently and quickly between worktable, peripheral devices
and assembly lines etc.
A sub class of more general family of Robots, the Industrial Robots.
An industrial robot is officially defined by ISO as an automatically controlled,
reprogrammable, multipurpose manipulator programmable in three or more axes.
Despite its numerous possible usages, it finds most widespread usage in manufacturing
industry.
Typical applications of robots include welding, painting, assembly, pick and place,
packaging and palletizing, product inspection, and testing, all accomplished with high
endurance, speed, and precision.
Hydraulics
Hydraulics is a topic in applied science and engineering dealing with the mechanical
properties of liquids. Fluid mechanics provides the theoretical foundation for hydraulics,
which focuses on the engineering uses of fluid properties. In fluid power, hydraulics is used
for the generation, control, and transmission of power by the use of pressurized liquids.
Hydraulic topics range through most science and engineering disciplines, and cover
concepts such as pipe flow, dam design, fluidics and fluid control circuitry, pumps,
turbines, hydropower, computational fluid dynamics, flow measurement, river channel
behavior and erosion.
Free surface hydraulics is the branch of hydraulics dealing with free surface flow, such as
occurring in rivers, canals, lakes, estuaries and seas. Its sub-field open channel flow studies
the flow in open channels.
Hydraulic machines are machinery and tools that use liquid fluid power to do simple
work. Heavy equipment is a common example.
In this type of machine, hydraulic fluid is transmitted throughout the machine to various
hydraulic motors and hydraulic cylinders and which becomes pressurised according to the
resistance present. The fluid is controlled directly or automatically by control valves and
distributed through hoses and tubes.
The popularity of hydraulic machinery is due to the very large amount of power that can be
transferred through small tubes and flexible hoses, and the high power density and wide
array of actuators that can make use of this power.
Hydraulic machinery is operated by the use of hydraulics, where a liquid is the powering
medium.
Force and torque multiplication
A fundamental feature of hydraulic systems is the ability to apply force or torque
multiplication in an easy way, independent of the distance between the input and output,
without the need for mechanical gears or levers, either by altering the effective areas in two
connected cylinders or the effective displacement (cc/rev) between a pump and motor. In
normal cases, hydraulic ratios are combined with a mechanical force or torque ratio for
optimum machine designs such as boom movements and track drives for an excavator.
Examples
Two hydraulic cylinders interconnected
Cylinder C1 is one inch in radius, and cylinder C2 is ten inches in radius. If the force
exerted on C1 is 10 lbf, the force exerted by C2 is 1000 lbf because C2 is a hundred times
larger in area (S = πr²) as C1. The downside to this is that you have to move C1 a hundred
inches to move C2 one inch. The most common use for this is the classical hydraulic jack
where a pumping cylinder with a small diameter is connected to the lifting cylinder with a
large diameter.
Pump and motor
If a hydraulic rotary pump with the displacement 10 cc/rev is connected to a hydraulic
rotary motor with 100 cc/rev, the shaft torque required to drive the pump is 10 times less
than the torque available at the motor shaft, but the shaft speed (rev/min) for the motor is 10
times less than the pump shaft speed. This combination is actually the same type of force
multiplication as the cylinder example (1) just that the linear force in this case is a rotary
force, defined as torque.
Both these examples are usually referred to as a hydraulic transmission or hydrostatic
transmission involving a certain hydraulic "gear ratio".
Hydraulic pump
An exploded view of an external gear pump.
Hydraulic pumps supply fluid to the components in the system. Pressure in the system
develops in reaction to the load. Hence, a pump rated for 5,000 psi is capable of
maintaining flow against a load of 5,000 psi.
Pumps have a power density about ten times greater than an electric motor (by volume).
They are powered by an electric motor or an engine, connected through gears, belts, or a
flexible elastomeric coupling to reduce vibration.
Common types of hydraulic pumps to hydraulic machinery applications are;
Gear pump : cheap, durable (especially in g-rotor form). , simple. Less efficient,
because they are constant (fixed) displacement, and mainly suitable for pressures
below 20 MPa (3000 psi).
Vane pump : cheap and simple, reliable.Good for higher-flow low-pressure output.
Axial piston pump : many designed with a variable displacement mechanism, to vary
output flow for automatic control of pressure. There are various axial piston pump
designs, including swashplate (sometimes referred to as a valveplate pump) and
checkball (sometimes referred to as a wobble plate pump). The most common is the
swashplate pump. A variable-angle swashplate causes the pistons to reciprocate a
greater or lesser distance per rotation, allowing output flow rate and pressure to be
varied (greater displacement angle causes higher flow rate, lower pressure, and vice
versa).
Radial piston pump A pump that is normally used for very high pressure at small
flows.
Piston pumps are more expensive than gear or vane pumps, but provide longer life
operating at higher pressure, with difficult fluids and longer continuous duty cycles. Piston
pumps make up one half of a hydrostatic transmission.
Structure Details
The robotic arm in the picture is a lot of fun to make and use. It uses a first and third
class lever, and has a fun linkage for the grabber. It can grab, pick up, and move to the side.
A great first project to warm you up using levers and hydraulics.
You can peg the small pieces that hold the long arm (as I have), but it takes very precise
drilling, so your best bet is to glue the small cross pieces. Once the glue is set though,
drilling and pegging will make this model last forever (maybe longer).
First thing to do is: Gather the parts!
You will need
• 6 - 5 ml syringes
• 4 screw eyes big enough for a 3/16 dowel
• 93 cm of tubing
to fit the syringes, - 6
mm outside diameter
• 166 cm of 1 x 1 cm sticks
• base -this can be any size, however, mine is 2 cm thick, 8.8 cm wide x 26 cm
long ( an 11" piece of 1" x 4" wood)
Support structure
Overall view of the arm
• a small disk about 7.5 cm diameter - you can cut some plywood for this, or use the
precut wheels
• 30 cm of 2 cm x 2 cm wood - for the stand - any size close to this is OK though
• 50 cm of dowel - 14 cm more if you are going to peg the small crossbars for the arm
Tubing
You need two kinds of tubing:
4 mm inside and 6 mm
Outside
• the tubes for the syringes are 1/8" inside, 3/16" outside dimension
• (this is 4 mm inside and 6 mm outside dimension)
- and the holder tubes - to go around the dowel and the tubing and hold them in place
• this tubing is 3/16" inside and 1/4" outside dimension, (this is 6 mm inside and 8 mm
outside dimension)
Cut the 1 xl cm wood and drill the holes
The center of the holes near the ends is 6 mm away from the end.
When you drill holes in pieces the same length, lay them on top of each other and
drill, that way the holes will be exactly the same distance apart.
Important! - all 3/16" dowels are not the same! I find that if I use a 3/16" drill bit for
the holes, the dowel is so tight in the hole it will not move. So, I use a 13 /64" drill bit
and the dowel is snug so the piece doesn't wobble, but is loose enough that it moves
in the hole with some friction. You really should test your dowel in a scrap piece to
make sure the fit is correct (snug, but not too snug so it doesn't move).
With the 1x1 cm wood cut the following pieces:
3- 30 cm pieces - rounded at
one end 2 - 12.2 cm pieces,
round off the ends
2 - 7.5 cm pieces
4- 6 cm pieces, cut on an angle and sanded on the inside edge
4 - 3.2 cm pieces one has a small hole in the middle (use the smallest bit since it is just for
a bit of wire) 1 - 2.5 cm piece - drill a 13/64 hole in the middle
3 - 1.1 cm pieces - drill a 13/64 hole in the middle
The pieces should look like this!
H~ 6 cm-*|
12.2 cm
7.5 cm
1.1 cm - hole inthe middle of each.
These
two
are
the^
same.
6 cm
—
15
cm"
Cut 2 - 15 cm
pieces with the
2 x 2 cm wood
and cut the
base.
Cut a 7.5 cm
diameter circle
disk out of VV"
plywood. Drill a
13/64 hole in
the middle.
If there is no
measurement
for the hole,
the center of it
should be .6
cm from the
end of the
wood (this is
most of them).
One
has a
small
2.5 cm
3
13
cm
8 cm
13 cm
30 cm - all
three.
Make the long part of the arm, use the small 3.2 cm pieces to join them. The middle
bottom piece should have a small hole in the middle for a piece of wire later on.
This
piece ■
has a
small
hole
drilled
through
.
Hole on
side
Outside - holes
point out,
middle piece, hole
is up.
Glue them so
there is a
little space for the
middle piece to
slide.
Assemble the pieces as shown
here. Carefully glue the small 3.2
cm pieces to the outside 30 cm
pieces - make sure the holes are
pointing out.
Let the glue harden (dry?) and
assemble the base.
Place a 2.5 cm
peg in
the hole. It has
a little hole
drilled across
the
top.
The piece with small hole is on the bottom.
The Base!
Drill a hole in the base 8 cm from the
front and to the side so the disk is close
to one side. This will leave room for the
piston that moves it on the other side.
Cut a 4 cm dowel and glue it in the
base. Slide the disk over the dowel and
glue down the 2.5 cm piece over the
disk. This way the disk will rotate, but
not come off!
Glue peg in base and
to wood,
but not to the disk (it
has to
turn).
Place the center of the disk about 8 cm from the front and over to the side.
The right side of the support structure has two screw eyes, the one on the inside is big enough for the syringe tube and is 2.5 cm up from the bottom. The one on the outside can be smaller since it only will have a wire in it, and it is .5 of a cm from the bottom and .5 cm from the back (the long side of the base is the back). You can use a big one on the outside if that is all you have. Screw them in before you glue the pieces to the disk since it is easier (especially the inside one).
Cut a piece of dowel to fit in the holes 6 cm from the bottom. It should be long enough to
go to the outside edge of the support structure (that's what I call this part), so the structure
is exactly 3.2 cm across. The long arm should be 3.2 cm across, (measure your drying
long arm) so the space here has to be that wide. The 15 cm pieces are glued to the disk.
structure to the disk.Make the supports 3.2 cmapart
• 3 at 3 cm
long
• 4 at 4 cm
long
Insert pegs in the top holes so they stick in 1 cm, this will
hold the long arm. They don't need to be glued since
there is no motion that will work them loose, and it's nice
to be able to remove them Let this dry and go on to the
grabber arms.
The Grabber Arms
This is the part that
shows if you have
cut and drilled with accuracy!
Start off by looking at the diagram and checking out
where things will go.
Small
pieces
attach on
the
For the Grabber arms you will need 7 pieces of cut dowel.
The dowels will insert into the holes and a
tube is pushed over the end to hold them in
place.
So you need 10 tubes cut .5 of a cm. This is the 6mm tubing that is a bit bigger than
the tubing you use for the syringes. Did you get all that?
Push a 4 cm dowel through, add a spacerand attach the bottom linkage.
J__ /__ I__ L
Add the rubber sleeves over these dowels to hold them in place.
To finish, place the 4 cm
dowel through the long
arm, through a wooden
spacer and then through the
bottom arm, as shown here.
Do the same for the other
side and you are ready for
the claws! Place tubing
over the dowels to hold
them in place. There should
be .5 cm on each side of the
arm for the tubing.
The linkage should look something like this. Test it so it is smooth, sandwhere needed.
The claws!
There are two ways you can attach them. If you look above they both have a space
between them, and here there is no space between one of them. Our researchers have
decided that they are both fine and you can use whichever technique you want (in a
vote 42 to 5).
Either way, you need a wooden spacer on the arm on the right.
On these pieces the dowel doesn't need a rubber holder since they are going to be
glued and the dowel should be flat on the claw. Trim the dowel with a pair of small
wire snippers if they are too long.
Move the linkage in and out with your hands and adjust the claws so they are at the
correct angle, and they don't bind with each other. If they hit each other and don't
nicely mesh then take them off and sand them so they slide together. Once they are
smoothly meshing and at an angle that you like, put glue on the dowels and push them
in.
Now for the hydraulics!
As you have seen there are three syringes to
move the parts, and three to push them. You
will need to drill a small hole in the top or
side of the syringe, so you can attach it to the
arms with a small piece of wire. Each syringe
is held in place by a screw eye, and a plastic
tube (like the wooden dowels).
Attach the base-turning piston
Place the tube with the holder through the screw eye and into the syringe. Snug up\ the holder. Hot glue if needed.
11.5 cm
Take one of the
syringes (they can
also be called
pistons, since that's
what they are called
when they are used
in hydraulics) and
fill it with water.
Coloured water (use
food colouring) is
best since you can
easily see which
piston pushes which - you will have three.
Place the .5 cm outer tube over the 20 cm tube and leave it close to the end.
Fill the piston with water; attach the tube (the small outer tube should be on the opposite
end). When the piston and the tube are full, (get as many bubbles out as you can), place it
through the screw eye and onto the other syringe (which should be empty and pushed all the
way in. Then push some water in and attach the flat top to the screw eye on the base with a
small piece of wire. There you have it. Push and pull, it should move around! If the holder
tube slides along the tubing, you may need to get out the glue gun and glue it so it stays put.
Now for the long arm
Fill the tube with water and attach it tothe holdertop to the lon
Cut about 25 cm of tubing, place
a .5 cm tube over one end and
fill the syringe and tube so it is
full. Place the tubing through the
screw eye in the
middle of the
support arms
and over the
other syringe and you have
number two almost done. Attach
a wire through the top of the
syringe, and
through the wooden piece (you
did put in a hole didn't you?).
Twist it so the attachment is
snug and check your work. The
arm should go up and down!
Adjust the small holder tube at
the bottom so it is snug.
with water andt to the syringe. Slide up
the holder tube and attach the long arm.
The Claw mechanism (you can almost taste this it is so close!)
Place a screw eye into the crossbar and a piece of dowel with a small hole in it
in the center long arm. Fill the syringe as usual (I hope you are using different
colours). Slide up the .5 cm holder tube and then attach the syringe to the dowel
with some wire at the other end.