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In the four-bar mechanism system, the closed-loop equation for the position analysis is
Where theta3 and theta4 are unknown variables of the mechanism and theta2 joint variable is rotated by the outer actuation ring. Theta 3 and theta4 are determined by the other given elements using the above closed-loop equations(eq.3. and eq.4.) and the below plot shows the x and y position of the joint B by changing the theta2.
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Figure.8. shows the mechanical advantage by changing the theta2. The interesting point is the mechanical advantage drastically increases when theta2 is 277°. Figure 7 shows that w4(wout) is zero when theta2 is 277° and this means that wout is at this this is the toggle point. Since this makes the denominator of equation 9 zero, the mechanical advantages increase infinitely.
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