Exercise 2.17 Figure 2.26 shows a parallel robot used for surgical applications. As shown in Figure 2.26(a), leg A is an RRRP chain, while legs B and C are RRRUR chains. A surgical tool is rigidly attached to the end-effector. (a) Use Grübler's formula to find the number of degrees of freedom of the Leg C End-effector Leg B Leg D Surgical tool End-effector Leg D Leg A Surgical tool Leg D Base Base, (a) Point A Point A (b) Figure 2.26: Surgical manipulator. mechanism in Figure 2.26(a). (b) Now suppose that the surgical tool must always pass through point A in Figure 2.26(a). How many degrees of freedom does the manipulator have? (c) Legs A, B, and C are now replaced by three identical RRRR legs as shown in Figure 2.26(b). Furthermore, the axes of all R. joints pass through point A. Use Grübler's formula to derive the number of degrees of freedom of this mechanism.