The vacuum zone manipulator

The gripper.json feature let you customize a gripper with one or more vacuum channels.

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How it works

In order to have this functionality working, the position and the dimensions of the bounding rectangle should be defined for each vacuum zone as well as the digital output channels that control the vacuum valves and optionally the compressed air used at release.

The file structure:

name: name of the gripper

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• edgeAlignment: if true, the box edges will be aligned to the gripper zone edges, otherwise the gripper zone(s) will be centered above the box center

• coveragePercent: defines how many percents of the vacuum zone (bounding rectangle) area must be covered in order to use a specific zone

tcp: the tool center point (TCP) of the gripper as [x, y, z, rx, ry, rz]

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• id: unique identifier (number) of the vacuum area, starting from 1

• x, y: center point of the bounding rectangle relative to the gripper center

• width, length: size of the bounding rectangle

• grip: digital IO signal that controls the vacuum

  • type: standard, configurable, tool (robot IO type)

  • channel: the digital output channel (0-1 for tool 0-7 otherwise)

  • inverse: optional, true if high level signal means no vacuum

• release: digital signal that controls the compressed air blow (optional)

  • type: standard, configurable, tool (robot IO type)

  • channel: the digital output channel (0-1 for tool 0-7 otherwise)

  • inverse: optional, true if high level signal means no blow

configurations: list of valid combinations of vacuum areas that can be used together 

Every time you make changes in the gripper json file, make sure to:

•  verify the correct syntax in a online tool like https://jsonformatter.org/

• upload the file again with the same name (must be gripper.json)

• select another gripper type e.g. custom gripper, and then

• select “import from gripper.json” again

• check the timestamp of last import has changed under the drop-down menu

• make sure there is no other (probably older) gripper.json file in the “patterns” folder.

  The current Pally URCap reads both locations for compatibility reasons:

  1. /programs/patterns

  2. /programs

The gripper.json file

{
  "name": "4-channel gripper",
  "description": "test gripper for multiple product sizes",
  "dimensions": {
    "width": 100,
    "length": 200,
    "height": 100,
    "weight": 1.85,
    "foamHeight": 15
  },
  "properties": {
    "coveragePercent": 40,
    "edgeAlignment": false
  },
  "tcp": [0, 0, 100, 0, 0, 0],
  "cog": [0, 0, 0],
  "zones": [
    {
      "id": 1,
      "x": 0,
      "y": -50,
      "width": 100,
      "length": 100,
      "grip": {
        "type": "standard",
        "channel": 0,
        "inverse": false
      },
      "release": {
        "type": "standard",
        "channel": 1
      }
    },
    {
      "id": 2,
      "x": 0,
      "y": 50,
      "width": 100,
      "length": 100,
      "grip": {
        "type": "standard",
        "channel": 2
      },
      "release": {
        "type": "standard",
        "channel": 3
      }
    }
  ],
  "configurations": [ 
    [1,2], [1], [2] 
  ]
}

Upload to the robot

Move the gripper.json file to a USB-stick and put it into the teach pendant of the robot. Copy the file from the USB-stick and paste it in the home folder of the UR robot.

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Select All Files for the filter to show the file.

As the file is now uploaded to the robot, you can then head over to the gripper tab under Installation and select “Import from gripper.json“

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Example

The following diagram is an example of a 4-channel suction-cup gripper with its corresponding gripper.json file. The different colors indicate different groups of suction cups that can be controlled together.

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 Example gripper.json file

{
  "name": "4-channel gripper",
  "description": "test gripper for multiple product sizes",
  "dimensions": {
    "width": 400,
    "length": 200,
    "height": 150,
    "weight": 1.9,
    "foamHeight": 15
  },
  "properties": {
    "coveragePercent": 51,
    "edgeAlignment": false
  },
  "tcp": [0, 0, 150, 0, 0, 0],
  "cog": [0, 0, 0],
  "zones": [
    {
      "id": 1,
      "x": 0,
      "y": 0,
      "width": 110,
      "length": 180,
      "grip": {
        "type": "standard",
        "channel": 0,
        "inverse": false
      },
      "release": {
        "type": "standard",
        "channel": 1
      }
    },
    {
      "id": 2,
      "x": -110,
      "y": 0,
      "width": 50,
      "length": 180,
      "grip": {
        "type": "standard",
        "channel": 2
      },
      "release": {
        "type": "standard",
        "channel": 3
      }
    },
    {
      "id": 3,
      "x": 110,
      "y": 0,
      "width": 50,
      "length": 180,
      "grip": {
        "type": "standard",
        "channel": 4
      },
      "release": {
        "type": "standard",
        "channel": 5
      }
    },
    {
      "id": 4,
      "x": 0,
      "y": 0,
      "width": 380,
      "length": 50,
      "grip": {
        "type": "standard",
        "channel": 6
      },
      "release": {
        "type": "standard",
        "channel": 7
      }
    }
  ],
  "configurations": [ 
    [1,2,3,4], [4], [1,2,3], [1,2], [2,3], [1], [2], [3] 
  ]
}

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Read more about how to import a gripper.json file.