MOBILITY
One of the primary concerns in either the planning or the analysis of a mechanism is that the number of degrees of freedom, also called the mobility of the device. The mobility of a mechanism is that the number of input parameters (usually joint variables) that has got to be controlled independently to bring the device into a selected posture.
Ignoring, for the instant, certain exceptions to be mentioned later, it’s possible to work out the mobility of a mechanism directly from a count of the quantity of links and also the number and kinds of joints comprising the mechanism.
To develop this relationship, consider that—before they’re connected together—each link of a planar mechanism has three degrees of freedom when moving with planar motion relative to the fixed link.
If the 2 links are connected by a two-degree-of-freedom joint, it provides one constraint.
When the constraints for all joints are subtracted from the overall degrees of freedom of the unconnected links, we discover the resulting mobility of the assembled mechanism.
If m = 1, the MECHANISM & LINK are often driven by one input motion to supply constrained (uniquely defined) motion.
Two examples are the slider-crank linkage and therefore the four-bar linkage, respectively.
If m = 2, then two separate input motions are necessary to provide constrained motion for the mechanism; such a case is that the five-bar linkage.
If the Kutzbach criterion yields m = 0, motion is impossible and therefore the MECHANISM & LINK forms a structure.
If the criterion yields m < 0, then there are redundant constraints within the chain and it forms a statically indeterminate structure.
Note within the examples that when three links are joined by one pin, such a connection is treated as two separate but concentric joints; two j1 joints must be counted.
Particular attention should be paid to the contact (joint) between the wheel and also the fixed link.
Here it’s assumed that slipping is feasible between the 2 links.
Recall that, during this case, the mechanism is mostly said as a “linkage.” it’s important to comprehend that the Kutzbach criterion can give an incorrect result.
MOBILITY
One of the primary concerns in either the planning or the analysis of a mechanism is that the number of degrees of freedom, also called the mobility of the device. The mobility of a mechanism is that the number of input parameters (usually joint variables) that has got to be controlled independently to bring the device into a selected posture.
Ignoring, for the instant, certain exceptions to be mentioned later, it’s possible to work out the mobility of a mechanism directly from a count of the quantity of links and also the number and kinds of joints comprising the mechanism.
To develop this relationship, consider that—before they’re connected together—each link of a planar mechanism has three degrees of freedom when moving with planar motion relative to the fixed link.
If the 2 links are connected by a two-degree-of-freedom joint, it provides one constraint.
When the constraints for all joints are subtracted from the overall degrees of freedom of the unconnected links, we discover the resulting mobility of the assembled mechanism.
If m = 1, the mechanism are often driven by one input motion to supply constrained (uniquely defined) motion.
Two examples are the slider-crank linkage and therefore the four-bar linkage, respectively.
If m = 2, then two separate input motions are necessary to provide constrained motion for the mechanism; such a case is that the five-bar linkage.
If the Kutzbach criterion yields m = 0, motion is impossible and therefore the mechanism forms a structure.
If the criterion yields m < 0, then there are redundant constraints within the chain and it forms a statically indeterminate structure.
Note within the examples that when three links are joined by one pin, such a connection is treated as two separate but concentric joints; two j1 joints must be counted.
Particular attention should be paid to the contact (joint) between the wheel and also the fixed link.
Here it’s assumed that slipping is feasible between the 2 links.
Recall that, during this case, the mechanism is mostly said as a “linkage.” it’s important to comprehend that the Kutzbach criterion can give an incorrect result.
For example, represents a structure which the criterion properly predicts m = 0. However, the result’s a double-parallelogram linkage with a mobility of m = 1, although indicates that it’s a structure.
The actual mobility of m = 1 results given that the parallelogram geometry is achieved.
CHARACTERISTICS OF MECHANISMS
An ideal system for the classification of mechanisms would be a system that permits a designer to enter the system with a group of specifications and leave with one or more mechanisms that satisfy those specifications many attempts are made; few are particularly successful in devising a satisfactory system.
In total, Torfason displays 262 mechanisms, each of which might have a spread of dimensions.
His categories are as follows: Snap-Action Mechanisms Snap-action, toggle, or flip-flop mechanisms are used for switches, clamps, or fasteners.
Torfason also includes spring clips AND gate breakers.
Linear Actuators Linear actuators include stationary screws with traveling nuts, stationary nuts with traveling screws, and single-acting and double-acting hydraulic and pneumatic cylinders.
Fine Adjustments Fine adjustments could also be obtained with screws, including differential screws, worm gearing, wedges, levers, levers asynchronous, and various motion-adjusting mechanisms.
Clamping Mechanisms
Typical clamping mechanisms are the C-clamp, the wood worker’s screw clamp, cam-actuated and lever-actuated clamps, vises, presses (such because the toggle press), collets, and stamp mills.
Locational Devices Torfason shows 15 locational mechanisms.
Ratchets and Escapements
There are many various styles of ratchets and escapements, some quite clever. they’re employed in locks, jacks, clockwork, and other applications requiring some kind of intermittent motion.
Swinging or Rocking Mechanisms
The category of swinging or rocking mechanisms is commonly termed oscillators; in each case, the output rocks or swings through an angle that’s generally but 360◦.
