Add external axes with no kinematics

Alex_Corrado

Hi all,
I'm adding to my robot application ( robot with 6 d.o.f.) two external axes to command via Ethercat a special gripper with 2 d.o.f. I would like to command them from the Python API without any kinematics and I will probably use them in target position mode. I guess I'll have to update my licence to get the two extra axes, right? What else should I do?

Philippe

Hi Alex,

Yes, you probably have a license for just the Manipulator module, which supports the actuators that are part of the manipulator kinematics. If you want to add more actuators, you can get a license update so you can enable the Machine module, which comes with two axes and setpoint generators (jerk limited motion to a set target position).

Can you please send a quick request to sales@vectioneer.com, so we can make a quotation for you.

Philippe

Alex_Corrado

OK, thank you.
From the Python API, how can these two additional axes be controlled? And from a configuration point of view, how can you determine which EtherCAT devices are part of the robot and which control the two external axes?

Philippe

Alex_Corrado You can do it in several ways:

using a SetpointGenerator module, you can set the target point via python and a smoothed setpoint is then generated for the axis this is linked to
stream your own profile (requires hard-realtime), this way you can also create an additional feedback loop, for instance to close, until you feel a certain force with a force sensor. You can do this via the Motorcortex API (via setParameter) or via a UDP module (UDP is preferred because it has better realtime performance).

Note:
you can configure the drive in position, velocity and torque mode, so you can also choose what signal you wish to command.

Alex_Corrado

This is clear, but usually for the robot I connect the PDOs of the 6 drives to the 6 control loops that are automatically generated when I use the robot app (fields filled in internally by the kinematics); in this case, if two additional axes were ‘activated’, I would find 8 control loops, but which of these are related to the two external axes?

Philippe

The Machine module will be available after activation and you will configure your system for 8 axes in total. The first 6 will still be linked to the manipulator module and the last two you can link to the Machine Module.

So a number of things need to be done:

upgrade the license
in config.json:
- increase the number of axes and actuators to 8
- enable the Machine modules with 2 joints
link your ethercat drives to the new Actuators (Actuator 7 and 8)
link the machine module's 2 joint signals to the to the last two axes in AxesControl.
setup the correct parameters for the Actuators 7 and 8 (like limiters)
not to forget: there is a set of matrices to convert between Axes and Actuators, these need to be set to the unity matrix manually, since changing the size of axes and actuators will make the current value not correct.

Alex_Corrado

Before upgrading the license I am testing it with the time limited license. I believe that the limits and any reduction ratios are set in the control.xml file, as for the other axes, right? Where can I find these matrices that need to be set up?

Philippe

Yes this is in control.xml. Look for axesToActuatorTransform and actuatorToAxesTransform. If you delete these lines from control.xml and deploy the configuration, the system will initialize the parameter to the unity matrix. So then save the parameter in DESK to create a new control.xml on the controller and then fetch it back up to your portal.

To test, you can also remove (or rename) your license file, so you fall back to demo mode, then you can configure and use additional axes that are not currently part of your license. If you do not do that the system will not start because it will see only 6 axes in the license and you configured 8 for instance. Without a license you can run for about 30 minutes every time, but you can configure as many axes as you like.

Alex_Corrado

I followed your tips but when I try to switch in manual joint mode an error appear (see below). I updated also the file "machine-control.link.json" as follow. What else is missing on the configuration?

{ "Version": "1.0.0", "Groups": [ { "Name": "From Logic To Control", "SystemMode": "All", "Enable": true, "Links": [ { "Source": { "Path": "root/Logic/:stateToCtrl" }, "Destination": { "Path": "root/MachineControl/:fromState" } }, { "Source": { "Path": "root/Logic/:modeToCtrl" }, "Destination": { "Path": "root/MachineControl/:fromMode" } } ] }, { "Name": "From Control To Logic", "SystemMode": "All", "Enable": true, "Links": [ { "Source": { "Path": "root/MachineControl/:toMode" }, "Destination": { "Path": "root/Logic/:ctrlToMode" } } ] }, { "Name": "Between Axis Control and Machine Control", "SystemMode": "All", "Enable": true, "Links": [ { "Source": { "Path": "root/AxesControl/axesPositionsActual", "Index": 6, "Length": 2 }, "Destination": { "Path": "root/MachineControl/actualJointPositionsFiltered", "Index": 0 } }, { "Source": { "Path": "root/MachineControl/jointPositionsTarget", "Index": 0 }, "Destination": { "Path": "root/AxesControl/axesPositionsInput", "Index": 6, "Length": 2 } }, { "Source": { "Path": "root/MachineControl/jointVelocitiesTarget", "Index": 0 }, "Destination": { "Path": "root/AxesControl/axesVelocitiesInput", "Index": 6, "Length": 2 } }, { "Source": { "Path": "root/MachineControl/jointAccelerationsTarget", "Index": 0 }, "Destination": { "Path": "root/AxesControl/axesAccelerationsInput", "Index": 6, "Length": 2 } }, { "Source": { "Path": "root/AxesControl/axesIsOpenLoop" }, "Destination": { "Path": "root/MachineControl/jointIsOpenLoop" } } ] }, { "Name": "DefaultModeSetting", "SystemMode": "All", "Enable": true, "SetParameters": [ { "Path": "root/MachineControl/gotoJogMode", "Value": true } ] }, { "Name": "PositionMode", "SystemMode": "All", "Enable": true, "SetParameters": [ { "Path": "root/MachineControl/gotoVelocityMode", "Value": false } ] }, { "Name": "VelocityMode", "SystemMode": "All", "Enable": false, "SetParameters": [ { "Path": "root/MachineControl/gotoVelocityMode", "Value": true } ] } ] }

philippeH

Hi Alex,

I just checked out your log file and noticed you have allot of double linking.

I provided you with a linking example (6Axis Robot + 2 Machine):

You could use this linking folder instead, just rename the other on the linking_ and the linking_update to linking. in case you have personalized linking please update yourself.

Alex_Corrado

Was the file "manipulator-control.link.json" the problem? I didn't understand what the problem was.

Philippe

Please use the working example and compare it to your configuration to find the missing setting.

Alex_Corrado

The example works fine, wrt the old files I found some wrong "enable" fields. From Python's point of view, how can the two external joints be controlled separately? For the robot, a RobotCommand reference is initialized, which is automatically connected to the ‘manipulatorControl’, but how does it work with the additional axes? Do I have to “rewrite” the robot libraries for those axes connecting directly them to the ‘machineControl’ fields?

Alex_Corrado

I need further clarification. I added jog commands for the two additional axes as well. Obviously, to use them in simulation, I added the simulated target and actual position fields to their PDOs and created two additional joystick commands that write to the ‘root/MachineControl/hostInJointVelocity’ fields, similar to what I did for the robot's individual joints. But I see that the simulation is not working. Am I forgetting some connection?