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In engineering and design, mechanisms refer to the components or systems that convert input forces or motion into desired output motions or forces, often enabling a specific function or operation. Mechanisms can be as simple as levers and gears or as complex as robotic arms and automated machinery. They are crucial in translating the energy provided by actuators, such as motors or human effort, into useful work, often involving transformations of motion, such as linear to rotational movement or vice versa. Understanding the principles of mechanisms allows engineers to design systems that are efficient, reliable, and effective in performing tasks, making them fundamental in fields such as robotics, automotive engineering, and manufacturing.
Linkage mechanism:-
A linkage mechanism is a mechanical system made up of interconnected links or components that work together to transmit motion and force in a controlled manner. These mechanisms consist of rigid bodies (links) connected by joints, which allow relative motion between the links, enabling the conversion of input motion into a desired output motion. Common types of linkage mechanisms include four-bar linkages, slider-crank mechanisms, and quick return mechanisms, each serving various applications in fields like robotics, automotive engineering, and industrial machinery. By analyzing and designing these linkages, engineers can achieve specific motion paths and functions, making them essential in many mechanical systems.
Types of linkage mechanisms:
Four-bar linkage
Slider-crank mechanism
Rack and pinion
Cam and follower
Toggle mechanism
Applications of linkage mechanisms
Printing Press Mechanisms
Aircraft Landing Gear Systems
Conveyor Belt Systems
Door Closing Mechanisms.
Simulation of linkage Mechanism
Simulation of linkage Mechanism
It consists of four connected links joined by revolute joints. Its versatility lies in its ability to convert rotary motion into oscillating motion and vice versa.
As the crank rotates, it propels the slider back and forth in a linear motion.
This mechanism finds widespread use in engines, pumps, and machinery requiring the conversion of rotary motion into linear motion.
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Slider crane mechanism:-
Slider crane mechanism:-
The slider-crank mechanism is a mechanical system commonly used to convert rotary motion into reciprocating motion or vice versa. It consists of four main components:
Components:
Components:
Crank: Rotates around a fixed axis (the crankshaft) and provides input motion.
Connecting Rod: Links the crank to the slider and transmits motion and forces.
Slider: Moves in a straight line (reciprocating motion) along a guide.
Frame: Serves as the fixed base supporting the mechanism.
Working Principle:
Working Principle:
Rotary to Linear Motion: When the crank rotates, the connecting rod transmits this motion to the slider, causing it to reciprocate linearly.
Linear to Rotary Motion: In reverse, the slider's linear motion can drive the crank to rotate.
Applications:
Applications:
Internal Combustion Engines: Converts piston motion into crankshaft rotation.
Compressors: Transforms rotary motion into piston motion to compress gases.
Pumps: Used in reciprocating pumps for fluid transfer.
Press Machines: For pressing operations in industries.
Degree of freedom(DOF):-
The degree of freedom (DOF) in a mechanism refers to the number of independent motions (or parameters) required to define the position of all parts of the mechanism relative to a fixed frame. It indicates the mobility of the system.
Calculation:
Calculation:
The degree of freedom for planar mechanisms is determined using Grübler's Equation:
DOF=3(n−1)−2j1−j2DOF = 3(n - 1) - 2j_1 - j_2DOF=3(n−1)−2j1−j2
Where:
nnn: Number of links (including the fixed link).
j1j_1j1: Number of lower pairs (1 DOF joints like revolute or prismatic).
j2j_2j2: Number of higher pairs (2 DOF joints like cams or gears).
For spatial mechanisms, the equation becomes:
DOF=6(n−1)−5j1−4j2DOF = 6(n - 1) - 5j_1 - 4j_2DOF=6(n−1)−5j1−4j2
Examples:
Examples:
Slider-Crank Mechanism:
n=4n = 4n=4, j1=4j_1 = 4j1=4, j2=0j_2 = 0j2=0
DOF=3(4−1)−2(4)=1DOF = 3(4 - 1) - 2(4) = 1DOF=3(4−1)−2(4)=1
It has 1 DOF, meaning one input controls its motion.Four-Bar Linkage:
n=4n = 4n=4, j1=4j_1 = 4j1=4, j2=0j_2 = 0j2=0
DOF=3(4−1)−2(4)=1DOF = 3(4 - 1) - 2(4) = 1DOF=3(4−1)−2(4)=1
It also has 1 DOF.
Interpretation:
Interpretation:
DOF = 0: Mechanism is a structure (no motion).
DOF = 1: Single input controls the entire mechanism.
DOF > 1: Multiple inputs or motions are required.
The concept is crucial for analyzing mechanisms in robotics, automobiles, and machinery to ensure desired mobility and control.
MSBS of chasis:-
MSBS of chasis:-
The MSBS of chassis activity helps us understand basic structure of project. It helps to learn how to select adaptor by calculating torque and mass of slider. This understanding is important for our course project because it involves designing and building mechanisms that work efficiently. By understanding this we can apply this knowledge to design and analyze more complex mechanical systems in our course project.
Volume=11.5*10.5*0.5(6+4.5)+0.5(3.5+4.5)*3.5+2(4.5*5)
= 120.75+23.625+14+45
= 20.33cm^3.
Density = Mass/Volume
Mass=Density*Volume
= 7.5*20.33
= 159.6g
Mass of chassis=152.5+300+300+300(mc+mw+mp)
= 1059.373g
= 1.0593kg.
Force=mass * gravity * coefficient of friction between two surfaces
=0.6*9.8*1.0593
=6.229N
Torque = Force* r (r->distance)
=6.22*3.5*10^-2Nm
=0.2Nm
=2.03 kg cm*1.2(FOS)
Therefore Torque=3.04 kg-cm.
Speed of the Actuator=30 rpm.
This activity helped me in understanding how to calculate the Torque and select the motor for any given project .
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