acceleration_filter.hpp

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/* Author: Paul Gesel
Description: applies smoothing by limiting the acceleration between consecutive commands.
The purpose of the plugin is to prevent the robot's acceleration limits from being violated by instantaneous changes
to the servo command topics.
 
 In the diagrams below, the c-v lines show the displacement that will occur given the current velocity. The t-c lines
 shows the displacement between the current position and the desired position. The dashed lines shows the maximum
 possible displacements that are within the acceleration limits. The v-t lines shows the acceleration commands that
 will be used by this acceleration-limiting plugin. The x point shows the position that will be used for each scenario.
 
Scenario A: The desired position is within the acceleration limits. The next commanded point will be exactly the
desired point.
     ________
    |        |
c --|-----xt |
 \__|__ v    |
    |________|
 
Scenario B: The line between the current position and the desired position intersects the acceleration limits, but the
reference position is not within the bounds. The next commanded point will be the point on the displacement line that
is closest to the reference.
     ________
    |        |
c --|--------x------t
 \__|__ v    |
    |________|
 
Scenario C: Neither the displacement line intersects the acceleration limits nor does the reference point lie within
the limits. In this case, the next commanded point will be the one that minimizes the robot's velocity while
maintaining its direction.
           ________
          |        |
c --------x--- v   |
 \        |        |
  \       |________|
   t
 */
 
#pragma once
 
#include <cstddef>
 
#include <moveit/online_signal_smoothing/smoothing_base_class.hpp>
#include <moveit/robot_model/robot_model.hpp>
#include <moveit/robot_state/robot_state.hpp>
#include <moveit/utils/logger.hpp>
#include <moveit_acceleration_filter_parameters.hpp>
 
#include <osqp.h>
#include <types.h>
#include <Eigen/Sparse>
 
namespace online_signal_smoothing
{
MOVEIT_STRUCT_FORWARD(OSQPDataWrapper);
 
// Plugin
class AccelerationLimitedPlugin : public SmoothingBaseClass
{
public:
  bool initialize(rclcpp::Node::SharedPtr node, moveit::core::RobotModelConstPtr robot_model,
                  size_t num_joints) override;
 
  bool doSmoothing(Eigen::VectorXd& positions, Eigen::VectorXd& velocities, Eigen::VectorXd& accelerations) override;
 
  bool reset(const Eigen::VectorXd& positions, const Eigen::VectorXd& velocities,
             const Eigen::VectorXd& accelerations) override;
 
  ~AccelerationLimitedPlugin() override
  {
    if (osqp_workspace_ != nullptr)
    {
      osqp_cleanup(osqp_workspace_);
    }
  }
 
private:
  rclcpp::Node::SharedPtr node_;
  online_signal_smoothing::Params params_;
  size_t num_joints_;
  Eigen::VectorXd last_velocities_;
  Eigen::VectorXd last_positions_;
  Eigen::VectorXd cur_acceleration_;
  Eigen::VectorXd positions_offset_;
  Eigen::VectorXd velocities_offset_;
  Eigen::VectorXd max_acceleration_limits_;
  Eigen::VectorXd min_acceleration_limits_;
  moveit::core::RobotModelConstPtr robot_model_;
  Eigen::SparseMatrix<double> constraints_sparse_;
  OSQPDataWrapperPtr osqp_data_;
  OSQPWorkspace* osqp_workspace_ = nullptr;
  OSQPSettings osqp_settings_;
};
}  // namespace online_signal_smoothing