External Axis

This Document describes how to add an external axis. An additional Stepper Motor Module is required to control the external Axis.

Hardware Connections

Connect the external axis just like all other axes. See pinout below:

Configuration

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  1. Switch on the Robot and start CPRog/iRC. It takes about 20-30s for the embedded computer to boot, so that it can be connected in step 3.

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  2. Click on "File". Then select your Robot type.

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  3. Click on Connect. Once connected, click on "File" again.

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  4. Click on "Configure Project"

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  5. Click on "External Axes"

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  6. Configure your external Axis.

The values displayed on the last image above are the correct values for the optional linear axis that the robolink DP robots can travel on.

• Type: Leave this field blank, unless you know which xml robot configuration file you want to use for the external axis.
• Kinematic: Select independent. - At the time of writing only independent axes are supported. "Dependent" means that the robot is connected to the external axis and moves with it. Independent allows the external axis to be moved independently of the robot.
• CAN ID: This is the address of the stepper motor module of this axis. Normally the first external axis has the CAN ID 88, which corresponds to switch position 9 on the stepper motor module of the axis.
• Gear scale: Defines the gear-transmission-ratio. It should be set, so that the position displayed in the software corresponds to the distance the external axis has been moved. When position 1000 (mm) is displayed in the software, the robot should have moved 1m. Negative Values can be used to invert the direction of travel. (For a rotational external axis, this value would be the degrees (°) of rotation, i.e. the when 360 (°) is displayed in the software, the axis should have completed one rotation.
• Position min and Position max: define the joint limits to avoid collisions. A 1m external axis should be limited to a minimum of 0 (mm) or greater and a maximum of 1000 (mm) or smaller.
• Velocity max: is the maximum velocity that the axis is allowed to move at. For a linear axis this value is in mm/s. For a rotational axis this value is in °/s.
• Acceleration: defines the instant acceleration in mm/s² or °/s². (Initial acceleration from standstill)
• Acceleration Inc: defines the subsequent acceleration in mm/s² or °/s². (Subsequent acceleration, once the axis is moving)

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  7. Click on "Save project". The project is saved locally on the PC and also remotely on the embedded computer module. This operation may take up to 5s. To activate the changes, restart the robot (switch off, wait 10s switch on.)

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  8. Click on Connect. Once connected, click on "File" again

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  9. Click on "Configure Project" and verify that the changes that you made are still present.

Firmware Parameters

Any stepper motor module will need to be configured. For known axes this is done in the factory. For custom axis this process needs to be carried out by the user for the system to function as intended.

1. Turn on the the ModuleCtrl software.
2. Select the correct CAN ID (hex) of your module.
   

   Fig 1. Select the correct CAN ID of your module and click connect.
   • For an additional 4th axis this would be 0x40 (decimal 64 converted to hex).
   • For an additional 5th axis this would be 0x50 (decimal 80 converted to hex).
   • For an additional 6th axis this would be 0x58.(decimal 88 converted to hex).
3. Click "connect"
4. Switch to the Configuration tab.
5. If the additional external axis has a motor encoder, which it normally should, enter the paramters as shown on Fig 2.
   

   Fig 2. Enter the module paramters as shown on this image.
   . Initially, click "read" to download the current parameters from the module. Remember to click the set after entering the values, so that the parameters are uploaded to the firmware.
6. Switch to the StepperMotor Tab and initially click "read" to download the current parameters. Enter the values shown in Fig 3 and click "write".
   

   Fig 3. Enter the module paramters as shown on this image.
7. Then click "read" again to verify that the configuration has been written as intended.
8. The axis is now configured to the default parameters for an external linear axis. However, you may want to vary the parameters:
9. If you later on notice that the referencing switch is not being found, change
   • "End Switch Rising" to invert the end-switch logic.
   • "Ref Speed" and "Ref Speed Slow", if the axis is moving at the wrong speed when referencing. Invert these parameters, if the axis is turning in the wrong direction during referencing.

Referencing

Now you are ready to reference the robot including the external axis. Start at Step 2 in the link, since the robot is already connected in software right now.