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Hexapod Grip Arm

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Revision as of 16:20, 21 November 2018 by Vorpalwiki (talk | contribs) (STEP 2: Adding Servo Extensions to the Robot's Servo Driver)

UNDER CONSTRUCTION

This page is currently in a DRAFT state. Do not attempt to build the Grip Arm project yet using these instructions.

What is the Hexapod Grip Arm?

The Hexapod Grip Arm is an open source 3D printed project that provides an arm with a claw end-effector. It's designed for [Vorpal The Hexapod] and will plug right into the accessory port for that project. It could easily be used with other robotics projects as well.

What are the Capabilities of the Grip Arm?

The Grip Arm can:

  • Raise and lower the claw end-effector. When attached to Vorpal The Hexapod, the claw can be lowered almost to ground level (about 2.5 centimeters or 1 inch) or it can be raised to about the top of the robot's cap.
  • Open and close the claw. The claw can grasp objects up to about 5 centimeters (2 inches) in diameter.
  • The Grip Arm can safely lift objects of up to about 120 grams (4.5 ounces).
  • The Grip Arm is designed so that the claw remains approximately level as it raises and lowers.

The Grip Arm is intended to be used with Vorpal The Hexapod for activities and games, not to lift heavy objects.

Photo Gallery

Controlling The Grip Arm

Assuming you have the Grip Arm assembled and installed along with the latest version of robot firmware, you may control it using the gamepad it as follows:

  1. Turn the robot dial to "RC". Now, turn it slowly counterclockwise until you hear one beep. Go a bit farther, then stop turning. You are now in radio control mode but the Grip Arm controls replace the usual F2 fight mode controls.
  2. Click on F2 on the gamepad. The DPAD will now control the Grip Arm according to the diagram below.

The Grip Arm will retain its position even when you switch to other modes. For example, you can open the claw, raise the arm, then hit W1 to walk. The arm will remain in its last position until you go back into F2 mode and change it.

As you hold DPAD buttons, the arm will move at modest speed, allowing you to stop where you need it to be.

NOTE: The robot goes into sleep mode when it's in any walking (W) mode after five seconds of inactivity. The Grip Arm servos will also go to sleep in this case. Clicking any DPAD button will wake up all the servos and they'll return to their prior positions.

GripArm-DPAD.JPG

Assembly Instructions

Bill of Materials (BOM)

A complete kit is available from The Vorpal Robotics Store

BOM:

  • 1 x Tower Pro MG90S servo. Used to lift the arm, metal gear servo required. The Vorpal Brand MG90 Servo is optimized for this kind of project.
  • 1 x Tower Pro SG90 servo. This is a plastic gear servo used to open and close the claw.
  • 2 x servo extension wires (M-F) 10cm length or longer.
  • 4 x nylon spacers 1/4" long, 1/4" outer diameter with center hole for #6 screw. These are used as bearings for moving parts.
  • 4 x #6-32 by 1/2" long button head socket screws with #6 washers.

3D Printed Parts

  • See Thingiverse for STL files to 3D print the Grip Arm parts

STEP 1: Flashing The Robot Control Program

To control the Grip Arm using your gamepad, you will need a new version of the robot code. This code needs to be installed before you start to build the Grip Arm, because you'll need it to adjust the servos and install the servo horns in the right orientation.

If you bought a robot kit from Vorpal Robotics after December 1, 2018, then your robot already has the new version of code that supports the Grip Arm.

If you self-sourced parts, or bought from us before December 1, 2018, then you need to follow instructions to flash the new robot code. The instructions to do this are here: Flashing the Robot Code.

STEP 2: Adding Servo Extensions to the Robot's Servo Driver

Take the cap off the robot and remove the screws holding the electronics caddy in place.

Carefully lift the electronics caddy and locate the servo driver.

There are two servo extension wires in the kit. One of them is labelled SD12 on one end and ELBOW on the other end. The other is labelled SD13 on one end and CLAW on the other end.

Carefully wiggle the Servo Driver out of the electronics caddy. Disconnect any long, 20cm jumper wires in ports 12 through 15. The Grip-Arm servo extension wires will be replacing those. Move the Buzzer power wires to port 14 and move the BEC power output wires to port 15 (if they're not already there). This means ports 12 and 13 are now clear of any wires. Plug the end of the servo extension labelled SD12 into Servo Driver port 12, and plug the wire end labelled SD13 into Servo Driver port 13. Do not disturb any of the hexapod leg or hip servo connections which are in ports 0 through 11, and do not disturb the SDA/SCL connections on the end of the Servo Driver. The diagram below illustrates these connections. GripArm-ServoDriver-Diagram.JPG

Carefully insert the Servo Driver back into its spot in the electronics caddy.

Route the other ends of the two servo extensions you just installed to the accessory port such that the ends labelled CLAW and ELBOW are sticking out of the port.

Place the electronics caddy back on top of the robot. Do not screw it in yet, just in case you accidentally unplugged something. Later after testing you'll screw down the caddy again.

License

The Hexapod Grip Arm is licensed under the Creative Commons Attribution-ShareAlike International 4.0 license.