[JTC] Move PID to controller plugin #2
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christophfroehlich
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saikishor
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| if (use_closed_loop_pid_adapter_) | ||
| { | ||
| trajectory_msgs::msg::JointTrajectory traj; | ||
| traj.points.push_back(state_current_); |
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@christophfroehlich Maybe also adding the state_desired_ would help
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computeGains takes a full trajectory, here it is only initialized with the same points as used for set_hold_position
As mentioned in the description, an update for dynamic reconfigure is missing.
But there is also a call missing for receiving a new trajectory, I'll push an update here.
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I pushed a new update
saikishor
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| lock_cmd_joint_names = get_node()->add_pre_set_parameters_callback( | ||
| [this](std::vector<rclcpp::Parameter> & parameters) | ||
| { | ||
| for (auto & parameter : parameters) | ||
| { | ||
| if (parameter.get_name() == "command_joints") | ||
| { | ||
| RCLCPP_ERROR( | ||
| get_node()->get_logger(), | ||
| "The parameter 'command_joints' is read-only. You can't change it."); | ||
| parameter = rclcpp::Parameter("command_joints", command_joint_names_); | ||
| } | ||
| } | ||
| }); |
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@christophfroehlich Shouldn't this be set before the set_parameter line?
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no because I wouldn't be able to set the parameter then. it should just "lock" the parameter afterwards
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Up to now there were only two possibilities of controlling the system with JTC:
The aim of this PR is to create an interface for supporting new control strategies, and enable even creating custom controller plugins by users. This is done by plugins of base class
TrajectoryControllerBase, loaded by the pluginlib.Together with the change of #3 it will even be supported to integrate state-space controller where the system output does not have the same size as the system input: See the following swing-up of a cart-pole from this demo, where I implemented a LQR as plugin
swingup_lqr_gh.mp4
Why to change JTC in this way:
The API was designed around the following methods:
computeControlLawNonRT: called when a new trajectory is received. This may take some time (e.g., calculating the gains for a LQR by solving Riccati equations). This blocks the execution of the new trajectory by JTC until the calculation is finished (seeis_ready()). The user has to implement a realtime-buffer to switch the old control law to the new one, once it is started (seestart()). In case of any abort (update trajectory withset_hold_position()), there is acomputeControlLawRTwhich needs to finish in the RT loop.updateGainsRT: A fast update within the RT loop, e.g., update of the PID gains from dynamic reconfigured ROS parameters.computeCommands: Evaluate the control law inside the RT loop with earlier calculated/updated gains.Notes:
jointsandcommand_jointsparameter #3, the map for the gains should becommand_joints. But most of the time this parameter is empty and copied over fromjointsin JTC. Because it is a static read-only variable, it is not possible to override the parameter for the plugin from JTC -> I had to make it reconfigurable from the generate_parameter_library, but added a callback afterwards to prohibit a later change from the user. If anyone knows a better way to solve this, please let me know.The behavior of existing configurations should not break with the proposed changes.