Problems with Flexy and the demo version

This blog post will be split into two parts. (1) Problems with Flexy and (2) demo version. In summary, we found problems with our design but we still used it in our presentations (Mid semester FYP review and Monash Open Day) as a demo version.You can see it in action with the Leap Motion here!

Problems with Flexy

In our last post about our progress: ARMazing! (Part Four: Arm + Hand = oh noes ) we found that we could not control the fingers with our proposed mechanism. Reasons were: 

1. Too much friction. Especially the part where the wires were rubbing against the plastic tube
2. The mechanical energy could not be efficiently transferred from the servos to the robot hand.
3. Hence the servos would stall and the fingers would no move.

Our first 3D printed hand

Furthermore, if the hand was mounted on the Mentor Arm, the movement about the wrist will effect strings (tendons). The wrist is controlled by 4R and 4L motors (see below). For example, if the wrist bends downwards, it will create a longer path between the servos and the robot fingers. The tension between the servos and the fingers will increase, contracting the fingers.

Figure 1

Demo Version

But we could not abandoned our project! We decided to NOT mount it on the Mentor arm. Instead, we will put the servos and the robot hand together WITHOUT the mentor arm. We had to do a couple of things first:

1. Create a platform for the hand to lie on. (Figure 2)
2. Create knobs on the servo where the string (tendon) will be hooked on. (Figure 3)
3. Added springs to the fingers to pull the finger back into the initial position. (Figure 4)

Figure 2

Figure 3 

Figure 4

More pictures below...

You can see it in action with the Leap Motion here!

Now we need to figure out what to do next.... a new hand with a different mechanism?