Analysis

The gripper servo outputs 7.7 kgf*cm of torque at a nominal 4.8 volts. For this project we ran the power supply at a constant 5 volts to allow for maximum torque. 7.7 kgf*cm is multiplied by 9.81 to get the torque of the servo, which is 75.5 N*cm. In order to keep the gripping force of the servo high, we kept the linkage arm length to a minimum. With a length of 5 cm we get a gripping force of 15.1 N.

A 4-Bar parallelogram is used for the linkage in order to provide predictable motion of the claws. If we were to make the drive link shorter and add mechanical advantage to the design, the claws would rotate inward, making it difficult for the user to pick things up accurately.