While the Solidworks simulation tell us alot about our mechanism, even enough to start building, it is still good to know about the velocities and accelerations of certain points along the mechanism. For our particular application, the acceleration of the gripper arms is of particular importance because that that dictates if the design will be able to impart the necessary force required to compress and clamp an object. A kinematic analysis was done on the mechanism in order to obtain velocities and accelerations of points of interest (only 1 in this case, point P shown below). After the accelerations are calculated (if time had permitted), a dynamic analysis could be done based involving the mass of the gripper. A verification on the ability of the input motor to provide the required torque was also going to be done (had time permitted).

• Kinematics

Simulation of Position Vectors from a linear starting distance of 0.6 inches to 2.2 inches for the Link 2 of Mechanism A. Also plots trajectory of Point P on Mechanism B, which is a critical point responsible for interacting with objects to be picked up.

The below figures shows the angular positions in global coordinates of both sub-mechanisms of the robotic gripper for each step increment of the helical joint. The input link 2 of Mechanism A has a limit of 2.18 inches for this configuration

The below figures shows the angular velocities of both sub-mechanisms of the robotic gripper for each step increment of the helical joint based on a motor rotation speed of 4 revolutions per second or for a 1/4-20" threaded rod, 0.2 inches/second.

Handwork done in order to get symbolic equations that were then plugged into Matlab to solve

We were unable to solve for the output angles of Mechanism B symbolically, so a numerical approach was used through the vpasolve command from Matlab. See Appendix for applicable code. The code does take much longer to solve, but there is convergence.

No acceleration analysis was done on either Mechanism A or B due to time constraints. This would have been good in order to have some idea on the clamping potential of the mechanism for a variety of objects.

• Dynamics

While a dynamic analysis was not done initially, it was understood how important it was to do after some initial failures in our first prototype. 

The mass of the gripper was sufficient to impart the required force onto an object, such as a baseball, but the stepper motor that was originally used did not have sufficient torque to move the assembly. While the stepper motor would work fine when it was just the threaded rod attached to it, the additional inertia from the rest of the connected links proved too difficult for it. A move to a Dynamixel AX-12 was the fix, given its relatively high stall torque of 1.5 Nm.

TODO 

• Conduct analysis based on mass of entire mechanism (found through material properties of Solidworks) 
• Conduct analysis of good friction coefficient features to attach to gripper link in order to allow for picking up more slippery objects.

• Functionality of Components for Use Case

TODO