26-04-2014, 02:25 PM
ASSISTANCE FOR A PATIENT, AGED PEOPLE OR PARCIALLY PARALYGED PERSON
ASSISTANCE FOR A PATIENT.docx (Size: 1.36 MB / Downloads: 13)
Though India is a country of hundred cores people, there is a deficiency of qualified people. It is quite unfortunate to say that we cannot provide 24 hours nurse facility to a patient in a hospital. Also it is quite impossible to provide 24 hours human assistance to an aged person. So we have developed a robot to provide 24 hours assistance to the patient in a hospital, aged person in home or a partially paralyzed person without any break. The robot can perform small works like pick & place a glass of water or medicine, switch on the fan and light and bring other things. It is a wireless controlled manipulator type robot with gripping facility.
Basic Component of the System
Mechanical Components
Gear
Plywood
Screw
Nut & bolt
Wheel
Custard wheel
Arm assembly with a four bar linkage
Planar Four-Bar Linkages
Fig.4
Planar four-bar linkages are important mechanisms found in machines. The kinematics and dynamics of planar four-bar linkages are important topics in mechanical engineering. Planar four-bar linkages are constructed from four links connected in a loop by four one degree of freedom joints. A joint may be either a revolute that is a hinged joint, denoted by R, or a prismatic, as sliding joint, denoted by P. The planar quadrilateral linkage is formed by four links and four revolute joints, denoted RR. The slider-crank linkage is constructed from four links connected by three revolute and one prismatic joint, or RRRP. The double slider is a PRRP linkage. Planar four-bar linkages can be designed to guide a wide variety of movements.
Planar Quadrilateral Linkage
Planar quadrilateral linkage, RR or 4R linkages have four rotating joints. One link of the chain is usually fixed, and is called the ground link, fixed link, or the frame. The two links connected to the frame are called the grounded links and are generally the input and output links of the system, sometimes called the input link and output link. The last link is the floating link, which is also called a coupler or connecting rod because it connects an input to the output.
Assuming the frame is horizontal there are four possibilities for the input and output links:[3]
A crank: can rotate a full 360 degrees
A rocker: can rotate through a limited range of angles which does not include 0° or 180°
A 0-rocker: can rotate through a limited range of angles which includes 0° but not 180°
A π-rocker: can rotate through a limited range of angles which includes 180° but not 0°
Some authors do not distinguish between the types of rocker.
Grashof Condition
The Grashof condition for a four-bar linkage states: If the sum of the shortest and longest link of a planar quadrilateral linkage is less than or equal to the sum of the remaining two links, then the shortest link can rotate fully with respect to a neighbouring link. In other words, the condition is satisfied if S+L ≤ P+Q where S is the shortest link, L is the longest, and P and Q are the other links.
Design of Four Bar Mechanisms
The synthesis, or design, of four bar mechanisms is important when aiming to produce a desired output motion for a specific input motion. In order to maximize cost and efficiency, a designer will choose the simplest mechanism possible to accomplish the desired motion. When selecting a mechanism type to be designed, link lengths must be determined by a process called dimensional synthesis. Dimensional synthesis involves an iterate-and-analyze methodology which in certain circumstances can be an inefficient process; however, in unique scenarios, exact and detailed procedures to design an accurate mechanism may not exist.