I began my design process by researching claw mechanisms. From the images I viewed, I saw the majority of claws consisted of two four bars where one controlled the top claw and the second controlled the bottom claw. For the arm portion of the mechanism, I decided on using a simple four bar attached to the servo motor given to us. Based off of those ideas, I created my first design seen below in Figure 2.
Figure 2. My initial design for my mechanism.
The problem with this first design is that the top and bottom claws would require two separate inputs, which would complicate the opening and closing of the claw at the same time. To solve this problem, I began brainstorming for a manner to simultaneously control both the top and bottom claw. I solved the problem by implementing two gears that would connect the bottom and top claws, as seen in Figure 3 below.
Figure 3. My second design that now included gears.
Now that the claw design would only require a single input to open and close, I moved on to attempting to find a way to open and close the claw using the motion of the arm. After spending a lot of time failing to do this by adding an addition link connecting the joint of the top claw to a link within the arm and a slotted slider, I concluded that it would be in my best interest to move forward with the project using a second servo motor to move the claw portion of the mechanism. This led to the final design shown below in Figure 4.
Figure 4. My final design for my mechanism.
In this final design, I added a third gear that would be connected to one of the gears controlling the claw that would be responsible for the opening and closing movement. This third gear would be powered by a micro-servo motor. This would conclude my design process for my mechanism.