External Axis

From Wiki

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:

ExternalAxisSchematic.png

Configuration

  • 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.

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

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

  • 4. Click on "Configure Project"

  • 5. Click on "External Axes"

  • 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)

  • 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.)

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

  • 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.

  • Turn on the Hardware, start the software. Wait until the green LEDs on top of all motor modules are blinking green. If the axis you are intending to work on now is not blinking green, something went wrong in the section above. Did you save the project and restart the hardware?
  • Click "Connect"
  • Once connected, click on "File" to get to the "backstage area"
  • Click on "Get Amp Configuration" to download the firmware parameters of all motor modules. After the download is complete, there will be a pop-up message telling you where the backup file can be found on your hard disk. Make a backup of that backup by copying the file to a safe location.
  • Open the file in a plain-text editor like Windows Notepad or Notepad++ (do not use Wordpad, Word or OpenOffice Writer). You will see something similar to this:
<!-- Parameter set for Commonplace Robotics robotics control  /-->
<!-- Target Robot: igus robolink                              /-->
<!-- support@cpr-robots.com                                   /-->
<AmpParameter>
    <Configuration ModuleType="RailStepperV02" NrOfJoints="5"/>

    <Joint0 ID="16" Version="Product 0x42 FW 0x02 0x10"
         ComTimeOut="2000" MaxCurrent="200" MaxLag="5000" EncoderErrorDetection="0" PosP="1.000" PosI="0.0000" PosD="0.000" PosAWU="30"
         Encoder="True" SwapEncoderDirection="False" EndSwitchRising="True" StopOnEndSwitch="False" UseIndexAsRef="False"
         RefStraight="False" RefSinus="False" RefHalf="True" SinusRefTics="2000" SinusRefMaxCycles="6"
         Offset="0" RefSpeed="50" RefSpeedSlow="10" RefFromBothSides="True"
         SGThreshold="2" CSLoad="18" CSStart="18" CSIdle="6" CSRef="15" StartArea="200"
         MinSupplyVoltage="500" MaxTemperature="500" Microstepping="0"
        />

    <Joint1 ID="32" Version="Product 0x42 FW 0x02 0x10"
         ComTimeOut="2000" MaxCurrent="200" MaxLag="5000" EncoderErrorDetection="0" PosP="1.000" PosI="0.0000" PosD="0.000" PosAWU="30"
         Encoder="True" SwapEncoderDirection="False" EndSwitchRising="True" StopOnEndSwitch="False" UseIndexAsRef="False"
         RefStraight="False" RefSinus="False" RefHalf="True" SinusRefTics="2000" SinusRefMaxCycles="6"
         Offset="891" RefSpeed="-50" RefSpeedSlow="-10" RefFromBothSides="True"
         SGThreshold="2" CSLoad="26" CSStart="26" CSIdle="10" CSRef="20" StartArea="200"
         MinSupplyVoltage="500" MaxTemperature="500" Microstepping="0"
        />

    <Joint2 ID="48" Version="Product 0x42 FW 0x04 0x07"
         ComTimeOut="3000" MaxCurrent="0" MaxLag="5000" EncoderErrorDetection="1000" PosP="1.000" PosI="0.0000" PosD="0.000" PosAWU="0"
         Encoder="True" SwapEncoderDirection="False" EndSwitchRising="True" StopOnEndSwitch="False" UseIndexAsRef="False"
         RefStraight="True" RefSinus="False" RefHalf="False" SinusRefTics="500" SinusRefMaxCycles="6"
         Offset="-1" RefSpeed="40" RefSpeedSlow="5" RefFromBothSides="True"
         SGThreshold="2" CSLoad="10" CSStart="10" CSIdle="3" CSRef="8" StartArea="200"
         MinSupplyVoltage="500" MaxTemperature="430" Microstepping="0"
        />

    <Joint3 ID="64" Version="Product 0x42 FW 0x02 0x10"
         ComTimeOut="2000" MaxCurrent="200" MaxLag="5000" EncoderErrorDetection="0" PosP="1.000" PosI="0.0000" PosD="0.000" PosAWU="30"
         Encoder="True" SwapEncoderDirection="False" EndSwitchRising="True" StopOnEndSwitch="False" UseIndexAsRef="False"
         RefStraight="False" RefSinus="False" RefHalf="True" SinusRefTics="2000" SinusRefMaxCycles="6"
         Offset="-1711" RefSpeed="50" RefSpeedSlow="10" RefFromBothSides="True"
         SGThreshold="2" CSLoad="22" CSStart="22" CSIdle="8" CSRef="18" StartArea="200"
         MinSupplyVoltage="500" MaxTemperature="500" Microstepping="0"
        />

    <Joint4 ID="80" Version="Product 0x42 FW 0x02 0x10"
         ComTimeOut="2000" MaxCurrent="200" MaxLag="5000" EncoderErrorDetection="0" PosP="1.000" PosI="0.0000" PosD="0.000" PosAWU="30"
         Encoder="True" SwapEncoderDirection="False" EndSwitchRising="True" StopOnEndSwitch="False" UseIndexAsRef="False"
         RefStraight="False" RefSinus="False" RefHalf="True" SinusRefTics="2000" SinusRefMaxCycles="6"
         Offset="-18405" RefSpeed="50" RefSpeedSlow="10" RefFromBothSides="True"
         SGThreshold="2" CSLoad="16" CSStart="16" CSIdle="6" CSRef="12" StartArea="200"
         MinSupplyVoltage="500" MaxTemperature="500" Microstepping="0"
        />

<Joint5 ID="88" Version="Product 0x42 FW 0x02 0x10"
         ComTimeOut="2000" MaxCurrent="200" MaxLag="5000" EncoderErrorDetection="0" PosP="1.000" PosI="0.0000" PosD="0.000" PosAWU="30"
         Encoder="True" SwapEncoderDirection="False" EndSwitchRising="True" StopOnEndSwitch="False" UseIndexAsRef="False"
         RefStraight="False" RefSinus="False" RefHalf="True" SinusRefTics="2000" SinusRefMaxCycles="6"
         Offset="-18405" RefSpeed="50" RefSpeedSlow="10" RefFromBothSides="True"
         SGThreshold="2" CSLoad="16" CSStart="16" CSIdle="6" CSRef="12" StartArea="200"
         MinSupplyVoltage="500" MaxTemperature="500" Microstepping="0"
        />	
		
</AmpParameter>
  • The last parameter Block, starting (here) with Joint5 ID="88" is the one to be configured. (note that the joint number starts at 0, so joint 5 would be the sixth module.) Please only change the values in quote marks, do not delete any quote marks, do not use decimal separators. This config file is case sensitive, so lower case and upper case matters.

Encoder Parameters

If the additional external axis is equipped with a motor encoder enter the parameters as shown below: 

ComTimeOut="2000"               #defines the max missed communication message before entering an error state
MaxCurrent="200"                #defines...
MaxLag="5000"                   #How many encoder tics is the encoder signal allowed to lag behind the desired motor position
EncoderErrorDetection="0"       #detects a broken encoder
PosP="1.000"                    #PID control parameter P
PosI="0.0000"                   #PID control parameter I
PosD="0.000"                    #PID control parameter D
PosAWU="30"                     #defines...
Encoder="True"                  #Encoder present?
SwapEncoderDirection="False"    #inverts the encoder direction with respect to the motor.

Reference/Ini Sensor Parameters

EndSwitchRising="True"          #Trigger on the rising edge by entering "True", trigger on the falling edge by entering "False"
StopOnEndSwitch="False"         #Should the axis motion stop during referencing when the end-switch trigger is received? 
UseIndexAsRef="False"           #Should the index pulse of the encoder be used as reference indicator?
RefStraight="False"             #"True" for linear axes, "False" for rotary axes
RefSinus="False"                #Should a sinusoidal search motion be performed? 
                                #("False" for linear axes, "True" for rotary axes with pin-ini)
RefHalf="True"                  #"True" for half-disc inis on rotary axes. "False" for Linear axes.
SinusRefTics="2000"             #How many encoder tics should  the sinusoidal search motion be incremented by per period
SinusRefMaxCycles="6"           #How many periods of sinusoidal search motion should be performed
Offset="-18405"                 #How many encoder tics is the 0 position of the axis away from the position of the reference sensor?
RefSpeed="50"                   #Sets the initial referencing speed: lower is slower
RefSpeedSlow="10"               #Sets the precision referencing speed: lower is slower and more precise
RefFromBothSides="True"         #Should the midpoint of the trigger signal be used instead of the rising/falling edge?

Motor Parameters

SGThreshold="2"                 #defines...
CSLoad="16"                     #Current under load conditions (arbitrary units). Values between 1 and 32 are allowed. 
                                #Smaller is less current.
CSStart="16"                    #Current when starting a motion (arbitrary units). Values between 1 and 32 are allowed. 
                                #Smaller is less curent.
CSIdle="6"                      #Current when position is held (arbitrary units). Values between 1 and 32 are allowed. 
                                #Smaller is less curent.
CSRef="12"                      #Current during referencing (arbitrary units). Values between 1 and 32 are allowed. 
                                #Smaller is less current.
StartArea="200"                 #defines...
MinSupplyVoltage="500"          #not used. Set to 500.
MaxTemperature="500"            #Sets Thermal shutdown temperature (arbitrary units). Select a value between 450 and 500.
Microstepping="254"             #Set to 254.
  • Once all changes have been made, double check the syntax, save the file under a new name and upload it to the robot using "Set Amp Configuration", choose the file and confirm that you want to make changes.Once the upload is complete, restart the hardware as a change of firmware parameters require a restart.


  • Now correct operation of the joints need to be verified.
  • Find the emergency stop button. You will likely need it as setting parameters on an unknown axis is an iterative process.
  • Once the controller has booted up, the motor module LEDs are blinking green, connect the robot, reset and enable the robot.
  • Move the joint by clicking on "E1-" or "E1+". If the axis moves and stops, when you let go of the button the SwapEncoderDirection is set correctly. Otherwise it needs to be swapped again. Using the process above. Power cycling the Hardware is mandatory after the upload of new parameters.
  • In the Software click on "Reference". Click on "Reset" and "Enable". Then click on "Reference axis" next to "External Axis 1". Observe the axis and prevent collisions using the emergency stop. If the joint shows up as "referenced" after the axis motion has finished. The referencing parameters have been set up correctly.
  • Next set up a program that moves the axis over 30min. observe the motor and module temperature. Increase the motor current, if the axis is struggling to move and reduce the motor current, if the axis and/or motor module are getting hot.

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.

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