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The condition describing the spatial structure group has the form:
(2.14)
Whence can we find the number of mobile links and kinematic pairs of the
spatial structural group:
(2.15)
The number of moving links and kinematic pairs in space structural group
should be an integer. In the particular case for spatial structure groups with
kinematic pairs of the fifth class:
A condition describing a flat structure group:
(2.16)
Whence the number of moving links and kinematic pairs find according to:
(2.17)
In the special case with kinematic pairs of the fifth class:
The number of moving links and kinematic pairs in a plane structural group
must be an integer.
Thus, the addition of structural groups to the mechanism does not change
its degree of mobility. Therefore, it is possible to synthesize new mechanisms
by attaching structural groups to the existing mechanism. We synthesize the
structural scheme of the mechanism with one
degree of mobility and two
output links by joining the main ABCD mechanism of the structural group
with kinematic pairs of the third, fourth and fifth classes
(Figure 2.5)
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Figure 2.5 – Structural diagram of the mechanism
with one degree of mobility and two output links
We determine the number of links and kinematic pairs of a structural group
by formula (2.15):
Thus, the structural group consists of two links
of one pair of the third
class, one pair of the fourth class and one pair of the fifth class.
The number of closed circuits formed by a structural group:
K = 3 – 2 = 1.
The number of redundant circuits links, of attached structural group:
S = 3 – (5 – 3) 1 – (5 – 4) 1 = 0.
In Fig. 2.5 the attached structural group is represented by a dashed line.
Достарыңызбен бөлісу: