Note: This tutorial assumes that you have completed the previous tutorials: Control.
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Control Modes

Description: Details on the control modes available for the qb SoftHand

Keywords: qbrobotics SoftHand control

Tutorial Level: BEGINNER

Next Tutorial: GUI Control

For the sake of simplicity, we are going to cover all the control modes for a single qb SoftHand, but it is just a matter of putting things together and set the launch file parameters properly to control several devices together (qb_chain_control is dedicated for such a scope).

All the control modes are initialized in the same manner but with distinct command line arguments. The default single-device control Node which brings everything up and simply waits for commands on the above mentioned Action topic is the following:

roslaunch qb_hand_control control.launch standalone:=true activate_on_initialization:=true device_id:=<actual_device_id>

  • activate_on_initialization [false]: Activates the motor at startup (the device will not move since the first command reference is received).

  • device_id [1]: Each device has its own ID, you need to set the one of the actual device connect to your system.

  • standalone [false]: Starts the Communication Handler together with the control Node. If you set this to false (or remove it since the default value is false), you need to launch the Communication Handler in a separate terminal.

It is worth noting that the activation of the motor can be postponed to improved safety if you are not aware of the state of the system at startup. To do so just set activate_on_initialization:=false (or remove it since the default value is false) and make a call to the Communication Handler activate_motors Service, when your system is ready, e.g. as follows:

rosservice call /communication_handler/activate_motors {"id: <actual_device_id>, max_repeats: 0"}

  • control_duration [0.01]: The duration of the control loop expressed in seconds.

  • get_currents [true]: Choose whether or not to retrieve current measurements from the device.

  • get_positions [true]: Choose whether or not to retrieve position measurements from the device.

  • get_distinct_packages [false]: Choose whether or not to retrieve current and position measurements from the device in two distinct packages.

  • max_repeats [3]: The maximum number of consecutive repetitions to mark retrieved data as corrupted.

  • set_commands [true]: Choose whether or not to send command positions to the device.

  • set_commands_async [false]: Choose whether or not to send commands without waiting for ack.

  • use_rviz [true]: Choose whether or not to use rviz. If enabled you should see a virtual hand on screen performing a similar behavior.

Be aware that the qb SoftHand is desensorized and therefore it is not possible to know exactly the position of each finger: the screen visualization is just the result of an estimation of the closure value and may differ form the real configuration of your hand (e.g. when grasping an object).

The followings are particular control modes which are enabled with few parameters, but the concepts of this paragraph hold for all of them:

  1. GUI Control

    Control the qb SoftHand through a simple GUI

  2. Waypoint Control

    Control the qb SoftHand motion through an automatic waypoint trajectory loop

  3. API Control

    Custom control application using the qbrobotics API

Wiki: qb_hand_control/Tutorials/Control Modes (last edited 2018-08-01 09:05:31 by AlessandroTondo)