Comparison of Electrical, Hydraulic and Pneumatic Systems

Comparison of electrical, hydraulic and pneumatic systems can be done in aspects like energy source, energy storage, energy cost, distribution system, linear actuators, rotary actuators and controllable force.

S.no	Aspect	Electrical	Hydraulic	Pneumatic
1	Energy source	Usually from outside supplier	Electric motor or diesel driven	Electric motor or diesel driven
2	Energy storage	Limited (batteries)	Limited (accumulator)	Good (reservoir)
3	Distribution system	Excellent, with minimal loss	Limited basically a local facility	Good. Can be treated as a plant wide service
4	Energy cost	Low cost	Moderate cost	High cost
5	Linear actuators	Short motion via solenoid. Otherwise via mechanical conversion	Cylinders. Very high force	Cylinders. Medium force
6	Rotary actuators	AC and DC motors. Good control on DC motors. AC motors cheap	Low speed. Good control. Can be stalled	Wide spread range. Accurate speed control difficult
7	Controllable force	Possible with solenoid & DC motors complicated by need for cooling	Controllable high force	Controllable medium force.
8	Problems	Dangers from electric shock	Leakage dangerous and unsightly. Fire hazard	Noisy

Comments

Grashof’s Law

Grashof’s Law The Grashof’s law states that for a four-bar linkage system, 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 neighboring link. Consider a four-bar-linkage. Denote the smallest link by S, the longest link by L and the & other two links by P and Q. If the Grashof’s Law condition is satisfied i.e S+L ≤ P+Q, then depending on whether shortest link ‘S’ is connected to the ground by one end, two ends, or no end there are 3 possible mechanisms. They are: Double crank mechanism Double-rocker mechanism and Crank and Rocker Mechanism 1. Double crank mechanism In double crank mechanism, the shortest link ‘S’ is a ground link. Both input crank and output crank rotate at 360°. Grashof’s condition for double crank mechanism: s+l > p+ q Let: ‘s’ = length of shortest link, ‘l’ = length...

Gruebler’s Equation

Gruebler’s Equation Degrees of freedom for planar linkages joined with common joints can be calculated through Gruebler’s equation. Gruebler’s equation is given by the formula: where, n = total number of links in the mechanism j p = total number of primary joints (pins or sliding joints) j h = total number of higher-order joints (cam or gear joints) Mechanisms and structures with varying mobility for Figure (a), (b) and (c) Most linkages used in machines have a single degree of freedom. An example of single degree-of-freedom linkage is shown in figure (a). Linkages with zero or negative degrees of freedom are termed locked mechanisms. Locked mechanisms are unable to move and form a structure. A truss is a structure composed of simple links and connected with pin joints and zero degrees of freedom. An example of locked mechanism is shown in figure (b). Linkages with multiple degrees of freedom need more than one dri...

Fundamental Concepts and Terms in Vibration

Fundamental Concepts and Terms in Vibration Vibration is a mechanical phenomenon, It is a movement first in one direction and then back again in the reverse direction. e.g: the motion of a swinging pendulum, the motion of a tuning fork. Any simple vibration is described by three factors: its amplitude; its frequency and rate of oscillation. Some of the general terms you will come across while studying on vibration topic are Oscillatory motion, Simple Harmonic Motion, Periodic Motion. now we will see the above mentioned terms in brief. Oscillatory motion is described as motion that repeats itself in a regular intervals of time. for example a sine wave or cos wave or pendulum. The time taken for an oscillation to occur is often referred to as the oscillatory period. Simple Harmonic Motion: Simple Harmonic Motion is periodic motion in which the restoring force is directly proportional to the displacement. F = -k*x A simple harmonic motion of a pendulum is an example of m...

mechanical engineering

Search This Blog