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.