(15) Speed Control

• C++

  // Only with Ruckig Pro
   
  #include <ruckig/ruckig.hpp>
   
  #include "plotter.hpp"
   
   
  using namespace ruckig;
   
  int main() {
      // Create instances: the Ruckig trajectory generator as well as input and output parameters
      Ruckig<3> ruckig(0.01);  // control cycle
      InputParameter<3> input;
      OutputParameter<3> output;
   
      // Set input parameters
      input.current_position = {0.0, 0.0, 0.5};
      input.current_velocity = {0.0, -2.2, -0.5};
      input.current_acceleration = {0.0, 2.5, -0.5};
   
      input.target_position = {5.0, -2.0, -3.5};
      input.target_velocity = {0.0, -0.5, -2.0};
      input.target_acceleration = {0.0, 0.0, 0.5};
   
      input.max_velocity = {3.0, 1.0, 3.0};
      input.max_acceleration = {3.0, 2.0, 1.0};
      input.max_jerk = {4.0, 3.0, 2.0};
   
      // We want to break to a paused state and re-accelerate to the normal trajectory
      // using Ruckig's speed control feature.
      // In this example, we have the four phases: 1. start, 2. brake, 3. accelerate, 4. end.
      std::string phase = "start";
      const double speed_change_duration = 1.0;  // [s]
      double time = 0.0;
   
      // Generate the trajectory within the control loop
      std::cout << "t | t_traj | position" << std::endl;
      std::cout << std::fixed << std::setprecision(2);
   
      Result result = Result::Working;
      while (result == Result::Working || result == Result::Paused) {
          result = ruckig.update(input, output);
   
          // The out.time parameter denotes the time on the trajectory,
          // which is not the same as the time in the control loop as soon as the speed is not 1.0.
          time += ruckig.delta_time;
   
          std::cout << time << " | " << output.time << " | " << pretty_print(output.new_position) << std::endl;
   
          if (output.time > 1.8 && phase == "start") {
              phase = "brake";
          }
          if (result == Result::Paused && phase == "brake") {
              phase = "accel";
          }
          if (phase == "accel" && ruckig.speed >= 1.0) {
              phase = "end";
          }
   
          if (phase == "brake") {
              ruckig.speed = std::max(ruckig.speed - ruckig.delta_time / speed_change_duration, 0.0);
          } else if (phase == "accel") {
              ruckig.speed = std::min(ruckig.speed + ruckig.delta_time / speed_change_duration, 1.0);
          }
   
          output.pass_to_input(input);
      }
   
      std::cout << "Trajectory duration: " << output.trajectory.get_duration() << " [s]." << std::endl;
  }

• Python

  # Only with Ruckig Pro
   
  from copy import copy
   
  from ruckig import InputParameter, OutputParameter, Result, Ruckig
   
   
  if __name__ == '__main__':
      # Create instances: the Ruckig OTG as well as input and output parameters
      otg = Ruckig(3, 0.01)  # DoFs, control cycle
      inp = InputParameter(3)
      out = OutputParameter(3)
   
      # Set input parameters
      inp.current_position = [0.0, 0.0, 0.5]
      inp.current_velocity = [0.0, -2.2, -0.5]
      inp.current_acceleration = [0.0, 2.5, -0.5]
   
      inp.target_position = [5.0, -2.0, -3.5]
      inp.target_velocity = [0.0, -0.5, -2.0]
      inp.target_acceleration = [0.0, 0.0, 0.5]
   
      inp.max_velocity = [3.0, 1.0, 3.0]
      inp.max_acceleration = [3.0, 2.0, 1.0]
      inp.max_jerk = [4.0, 3.0, 2.0]
   
      # We want to break to a paused state and re-accelerate to the normal trajectory
      # using Ruckig's speed control feature.
      # In this example, we have the four phases: 1. start, 2. brake, 3. accelerate, 4. end.
      phase = 'start'
      speed_change_duration = 1.0  # [s]
   
      print('\t'.join(['t', 't_traj'] + [str(i) for i in range(otg.degrees_of_freedom)]))
   
      # Generate the trajectory within the control loop
      first_output, times, out_list = None, [], []
      res = Result.Working
      while res == Result.Working or res == Result.Paused:
          res = otg.update(inp, out)
   
          if out.time > 1.8 and phase == 'start':
              phase = 'brake'
          if res == Result.Paused and phase == 'brake':
              phase = 'accel'
          if phase == 'accel' and otg.speed >= 1.0:
              phase = 'end'
   
          if phase == 'brake':
              otg.speed = max(otg.speed - otg.delta_time / speed_change_duration, 0.0)
          if phase == 'accel':
              otg.speed = min(otg.speed + otg.delta_time / speed_change_duration, 1.0)
   
          # The out.time parameter denotes the time on the trajectory,
          # which is not the same as the time in the control loop as soon as the speed is not 1.0.
          time = (times[-1] if times else 0.0) + otg.delta_time
   
          print('\t'.join([f'{time:0.3f}', f'{out.time:0.3f}'] + [f'{p:0.3f}' for p in out.new_position]))
          times.append(time)
          out_list.append(copy(out))
   
          out.pass_to_input(inp)
   
          if not first_output:
              first_output = copy(out)
   
      print(f'Calculation duration: {first_output.calculation_duration:0.1f} [µs]')
      print(f'Trajectory duration: {first_output.trajectory.duration:0.4f} [s]')
   
      # Plot the trajectory
      from pathlib import Path
      from plotter import Plotter
   
      project_path = Path(__file__).parent.parent.absolute()
      Plotter.plot_trajectory(project_path / 'examples' / '15_trajectory.pdf', otg, inp, out_list, plot_jerk=False, times=times)

Output Trajectory