Gripper assembly and positioning?

The more technical aspects of Spirit, and carry-over discussion from Kickstarter updates.
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Joined: Fri Jan 26, 2018 5:03 pm

Gripper assembly and positioning?

Postby gpvillamil » Thu Feb 01, 2018 2:57 pm

Just a quick note re gripper assembly, correct me if I'm wrong:

If you follow the instructions, you will go through the servo centering process for pan, grip and tilt. When you then assemble the gripper, you are instructed to assemble it in a near-closed position (grippers pointing forward).

However, I notice that when doing the demo behaviors, this means the grippers are too far forwards.

I made my own Arduino sketch to put the gripper in stowed position, and then just removed and repositioned the arms. This seems to be working fine. You can use servo trim to adjust the arms to close exactly.

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Re: Gripper assembly and positioning?

Postby esba1ley » Fri Feb 02, 2018 3:22 am

I actually broke the servo and had to replace it following the directions. Once I put in a new one, I ran the servo cal routine and watched how the servo moved... then, I installed the grippers so that they wouldn’t hit either limit during the cal routine. I found that I can now command to an open limit of 10, and a completely closed limit of 98.

One thing to note, though: if you have to replace a servo, make sure you replace it with exactly the same model: the plastic parts won’t fit other servos.
Erik S. Bailey
Entry, Descent, and Landing Aerospace Engineer
Maker, and Musician
SpiritRover Kickstarter Backer #460

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