24-12-2010, 04:24 PM
[attachment=7649]
Introduction
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[1] 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.
Components of Hydraulic Actuation Systems
1.Hydraulic Fluid:
The fluid used is 40W oil reads as 40 weight oil. It has high viscosity which maintains a lubricating film between moving parts. This also reduces friction loss and cools the components.
2.Line:
Pipe and tubes along with the fittings or connectors, constitute the conducting lines that carry hydraulic fluid between components.
3.Hydraulic Pump:
The pump used here is gear pump. A gear pump develops flow by carrying fluid between the teeth of two meshed gears. One gear is driven by the drive shaft and turns the other, which is free. The pumping chambers formed between the gear teeth are enclosed by the pump housing and the side plates. A low pressure region is created at the inlet as the gear teeth separate.
[attachment=7650]
Abhinav
Tripathi
Kulbhushan
Kumar
Akhilesh
Pankaj Singh
Navneet Verma
Tripathi
Kulbhushan
Kumar
Akhilesh
Pankaj Singh
Navneet Verma
Introduction
Hydraulic Actuators employs hydraulic pressure to drive an output member. These are used where high speed and large forces are required. The fluid used in hydraulic actuator is highly incompressible so that pressure applied can be transmitted instantaneously to the member attached to it. A robotic arm incorporates an articulate system, which together function in much same way as its biological counterpart. The skeleton is composed of rigid links that connect varying numbers of joints that are capable of sliding, twisting or rotating. The robot's muscles come in the form of actuators that convert hydraulic, electrical or pneumatic energy into power for each joint. Next there is an electronic nervous system of wires and sensors that carries commands to the muscles of the robotic arm and then back to an external computer. The main difference between the arm of the robot and that of a human is found at the arm's extremity. Rather than having a flexible, multi-fingered hand, typical robot arms end in special-purpose devices called end-effectors, which are installed directly into the wrist. To reduce the number of calculations, needed to determine the robot's exact position, the base is generally kept stationary. In a few applications, however, like the robots in spot welding, robots are programmed to follow an assembly line. The motions of the robots can be programmed by means of direct teaching where the arm is manually guided through its desired motion and the robot's computer remembers these specific motions, sort of like a watch and learn method. Robots can also be taught by means of programming by a computer specialist. Finally there is always the option of creating a learning computer that will gather data as it makes mistakes and on the following attempt, it won't make the same mistake again.
Principle Used in Hydraulic Actuator System
Pascal’s Law
Pressure applied to a confined fluid at any point is transmitted undiminished and equally throughout the fluid in all directions and acts upon every part of the confining vessel at right angles to its interior surfaces.
Amplification of Force
Since pressure P applied on an area A gives rise to a force F, given as, F = P×A Thus, if a force is applied over a small area to cause a pressure P in a confined fluid, the force generated on a larger area can be made many times larger than the applied force that crated the pressure. This principle is used in various hydraulic devices to such hydraulic press to generate very high forces.
Advantages of Hydraulic Actuation Systems
Hydraulics refers to the means and mechanisms of transmitting power through liquids. The original power source for the hydraulic system is a prime mover such as an electric motor which drives the pump. However, the mechanical equipment cannot be coupled directly to the prime mover because the required control over the motion, necessary for industrial operations cannot be achieved. In terms of these Hydraulic Actuation Systems offer unique advantages, as given below.
Variable Speed and Direction: Most large electric motors run at adjustable, but constant speeds.It is also the case for engines. The actuator (linear here) of a hydraulic system, however, can be driven at speeds that vary by large amounts and fast, by varying the pump delivery or using a flow control valve. In addition, a hydraulic actuator can be reversed instantly while in full motion without damage. This is not possible for most other prime movers.
Power-to-weight ratio: Hydraulic components, because of their high speed and pressure capabilities, can provide high power output with vary small weight and size, in comparison to electric system components. Note that in electric components, the size of equipment is mostly limited by the magnetic saturation limit of the iron.
Stall Condition and Overload Protection: A hydraulic actuator can be stalled without damage when overloaded, and will start up immediately when the load is reduced. The pressure relief valve in a hydraulic system protects it from overload damage. During stall, or when the load pressure exceeds the valve setting, pump delivery is directed to tank with definite limits to torque or force output. The only loss encountered is in terms of pump energy. On the contrary, stalling an electric motor is likely to cause damage.
Components of Hydraulic Actuation Systems
Hydraulic Fluid
Hydraulic fluid is essentially non-compressible to be able to transmit power instantaneously from one part of the system to another. At the same time, it lubricates the moving parts to reduce friction loss and cool the components so that the heat generated does not lead to fire hazards. It also helps in removing the contaminants to filter. The other desirable property of oil is its lubricating ability. Finally, often, the fluid also acts as a seal against leakage inside a hydraulic component. The degree of closeness of the mechanical fit and the oil viscosity determines leakage rate. Figure 2 below shows the role played by hydraulic fluid films in lubrication and sealing. The fluid used is 40W oil reads as 40 weight oil. It has high viscosity which maintains a lubricating film between moving parts.
