03-08-2012, 02:39 PM
Hydraulic ARM
hydrolic ARM.doc (Size: 537 KB / Downloads: 212)
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.
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).