Overview

This package determines the contact timing, locations, and forces, to execute a given robot body plan. Local body and footstep plans are computed separately, and heuristically combined later on.

License

The source code is released under a MIT License.

**Author: Joe Norby, Yanhao Yang
Affiliation: Robomechanics Lab
Maintainers: Yanhao Yang (yanha.nosp@m.oy@a.nosp@m.ndrew.nosp@m..cmu.nosp@m..edu) and Alex Stutt (astut.nosp@m.t@an.nosp@m.drew..nosp@m.cmu..nosp@m.edu)**

The Local Planner package has been tested under ROS Melodic 18.04. This is research code, expect that it changes often and any fitness for a particular purpose is disclaimed.

Usage

Config files

• local_planner.yaml Sets planning hyperparameters, for local body and footstep plans.

Nodes

local_planner

Calculates a local robot body plan, and discrete and continuous local footstep plans.

Local Body Planer

• Uses NMPC to find ground reaction forces that best track a nominal body trajectory.

Local Footstep Planner

• Uses the a given local body plan to calculate foot trajectories. It computes a contact schedule, and then selects discrete foothold positions using dynamic and kinematic heuristics similar to Raibert's heuristic.

Subscribed Topics

• **/terrain_map** ([grid_map_msgs/GridMap])

  The 2.5D height map with terrain information.

• **/global_plan** ([quad_msgs/RobotPlan])

  The global plan consisting of interpolated robot states leading from the start to the goal state.

• **/state/ground_truth** ([quad_msgs/RobotState])

  The current state of the robot.

• **/cmd_vel** ([geometry_msgs/Twist])

  Input velocity, given as a twist.

Published Topics

• **/local_plan** ([quad_msgs/RobotPlan])

  The local plan, consisting of interpolated robot states.

• **/foot_plan_discrete** ([quad_msgs/MultiFootPlanDiscrete])

  Matrix of foot contact locations (number of contacts x num_legs_).

• **/foot_plan_continuous** ([quad_msgs/MultiFootPlanContinuous])

  Continuous foot trajectories.

Parameters

• **update_rate** (int, default: 333)

  The update rate of the controller (in Hz).

• **timestep** (double, default: 0.03)

  Timestep duration (in seconds).

• **horizon_length** (int, default: 26)

  The length of the planning horizon in number of timesteps.

• **desired_height** (double, default: 0.27)

  Desired z-height (in meters).

• **toe_radius** (double, default: 0.02)

  Robot toe radius (in meters).

• **cmd_vel_filter_const** (double, default: 0.10)

  Commanded velocity filter constant.

• **cmd_vel_scale** (double, default: 1.0)

  Scale for input twist velocity (cmd_vel).

• **last_cmd_vel_msg_time_max** (double, default: 2.0)

  Threshold for maximum amount of time to wait for new twist velocity data from cmd_vel.

• **stand_vel_threshold** (double, default: 0.1)

  Velocity threshold to enter stand mode.

• **stand_cmd_vel_threshold** (double, default: 0.1)

  Commanded velocity threshold to enter stand mode.

• **stand_pos_error_threshold** (double, default: 0.05)

  Position error threshold to enter stand mode (measured from foot centroid).

Bugs & Feature Requests

Please report bugs and request features using the Issue Tracker.