butterworth_filter.h

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/* Author: Andy Zelenak
   Description: A first-order Butterworth low-pass filter. There is only one parameter to tune.
   The first-order Butterworth filter has the nice property that it will not overshoot.
 */
 
#pragma once
 
#include <cstddef>
 
#include <moveit_butterworth_filter_parameters.hpp>
#include <moveit/robot_model/robot_model.h>
#include <moveit/online_signal_smoothing/smoothing_base_class.h>
 
namespace online_signal_smoothing
{
class ButterworthFilter
{
public:
  ButterworthFilter(double low_pass_filter_coeff);
  ButterworthFilter() = delete;
 
  double filter(double new_measurement);
 
  void reset(const double data);
 
private:
  static constexpr std::size_t FILTER_LENGTH = 2;
  std::array<double, FILTER_LENGTH> previous_measurements_;
  double previous_filtered_measurement_;
  // Scale and feedback term are calculated from supplied filter coefficient
  double scale_term_;
  double feedback_term_;
};
 
// Plugin
class ButterworthFilterPlugin : 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;
 
private:
  rclcpp::Node::SharedPtr node_;
  std::vector<ButterworthFilter> position_filters_;
  size_t num_joints_;
};
}  // namespace online_signal_smoothing