Tutorials/drcsim/2.4/control mode switching


 * 1) DRC Tutorial: Switching control modes #

This tutorial will explain how to use the BDI-provided behavior library to control the Atlas robot, and how to switch between behavior-library control and your own controller.


 * 1) Background ##

The robot offers two gross modes of control:

* ROS topic: `/atlas/atlas_sim_interface_command` * message type: [atlas/AtlasSimInterfaceCommand](https://bitbucket.org/osrf/drcsim/src/default/ros/atlas_msgs/msg/AtlasSimInterfaceCommand.msg?at=default) * ROS topic: `/atlas/atlas_command` * message type: [atlas/AtlasCommand](https://bitbucket.org/osrf/drcsim/src/default/ros/atlas_msgs/msg/AtlasCommand.msg?at=default)
 * BDI mode: send a high-level goal, such as "stand" or "walk," to BDI's behavior library
 * user mode: send setpoints and gains to the PID controllers that are running on each joint.

You can mix and match these modes on a per-joint basis. Each message type has a `k_effort` array, with one element per joint. To exert BDI-mode control for joint `i`, set `k_effort[i]` to 0; for user-mode control, set it to 255. In this way, you can, for example, ask the BDI library to stand but then control the arms yourself. Note that some (perhaps many) combinations don't make sense, e.g., asking the BDI library to walk but retaining user-mode control of one of the legs.

You should always begin and end BDI-mode control in the "stand" mode. We'll cover this below in the example.


 * 1) Setup ##

There aren't special requirements beyond running drcsim 2.4.x with gazebo 1.6.y. Be sure to start with the usual shell setup: `source /usr/share/drcsim/setup.sh`. Let's bring the robot up in a world with some stuff in it:

roslaunch atlas_utils qual_task_1.launch


 * 1) The demo ##

What follows is, in a way, the worst sort of robot program: a single sequence of steps, executed open loop based on timers and without any feedback. But it will serve to illustrate the point of this tutorial, which is how to manage BDI mode and User mode control of the Atlas robot.

This program proceeds in 5 steps:

1. Send the robot to a home position with all joints at position=0. This step is executed in full User mode, with all joints controlled by the new command. 1. Switch to BDI STAND mode. Note that this step is undertaken in two parts: 1. Ask for STAND_PREP mode, but retain User mode control of all joints. Wait a little bit to let the BDI library get ready to stand. 1. Ask for STAND mode, handing control of all joints to BDI. 1. Take control of some of the arm and neck joints and move them to new positions. This is done while leaving the rest of the robot in BDI mode. We're starting to challenge the STAND mode by moving the arms, but the robot should not fall over. 1. Ask for WALK mode, sending the robot forward 4 steps. This is done while retaining User mode control of a few joints. We're really challenging the WALK mode by keeping control of the arms, but it mostly succeeds. Note that BDI mode expects foot poses to be expressed in the world frame; we first express them in the robot's ego-centric frame and then transform them into the world frame using received data from `/atlas/imu` and `/atlas/atlas_sim_interface_state`. 1. Send the robot back to home in full User mode.

To summarize, this program shows how to go from full User mode to full BDI mode to mixed User/BDI mode and back to full User mode. Many other sequences of transitions are possible.


 * 1) Creating ROS environment to launch demo ###

For running the demo script a minimal ROS setup is needed. Use a directory under ROS_PACKAGE_PATH and follow the instructions to create a package there:

. /opt/ros/fuerte/setup.bash cd ~/ros export ROS_PACKAGE_PATH=`pwd`:$ROS_PACKAGE_PATH roscreate-pkg control_mode_switch atlas_msgs rospy python_orocos_kdl roscd control_mode_switch chmod +x demo.py ./demo.py
 * 1) copy the python script below with name demo.py
 * 1) To run the demo:


 * 1) The code ###

The demo script in python which implements the instructions detailed in this section:


 * 1) !/usr/bin/env python

from __future__ import print_function

import roslib roslib.load_manifest('control_mode_switch') import rospy import time from atlas_msgs.msg import AtlasCommand, AtlasSimInterfaceCommand, AtlasSimInterfaceState, AtlasState, AtlasBehaviorStepData from sensor_msgs.msg import Imu import PyKDL from tf_conversions import posemath

class Demo:

def __init__(self): self.NUM_JOINTS = 28 # Latest message from /atlas/atlas_sim_interface_state self.asis_msg = None # Latest message from /atlas/imu self.imu_msg = None

# Set up publishers / subscribers self.ac_pub = rospy.Publisher('atlas/atlas_command', AtlasCommand) self.asic_pub = rospy.Publisher('atlas/atlas_sim_interface_command',          AtlasSimInterfaceCommand) self.asis_sub = rospy.Subscriber('atlas/atlas_sim_interface_state',          AtlasSimInterfaceState, self.state_cb) self.imu_sub = rospy.Subscriber('atlas/imu',          Imu, self.imu_cb) # Wait for subscribers to hook up, lest they miss our commands time.sleep(2.0) def state_cb(self, msg): self.asis_msg = msg

def imu_cb(self, msg): self.imu_msg = msg def demo(self): # Step 0: Go to home pose under user control home_msg = AtlasCommand # Always insert current time home_msg.header.stamp = rospy.Time.now # Assign some position and gain values that will get us there. home_msg.position = [0.0] * self.NUM_JOINTS home_msg.velocity = [0.0] * self.NUM_JOINTS home_msg.effort = [0.0] * self.NUM_JOINTS home_msg.kp_position = [20.0, 4000.0, 2000.0, 20.0, 5.0, 100.0, 2000.0, 1000.0, 900.0, 300.0, 5.0, 100.0, 2000.0, 1000.0, 900.0, 300.0, 2000.0, 1000.0, 200.0, 200.0, 50.0, 100.0, 2000.0, 1000.0, 200.0, 200.0, 50.0, 100.0] home_msg.ki_position = [0.0] * self.NUM_JOINTS home_msg.kd_position = [0.0] * self.NUM_JOINTS # Bump up kp_velocity to reduce the jerkiness of the transition home_msg.kp_velocity = [50.0] * self.NUM_JOINTS home_msg.i_effort_min = [0.0] * self.NUM_JOINTS home_msg.i_effort_max = [0.0] * self.NUM_JOINTS # Set k_effort = [1] to indicate that we want all joints under user control home_msg.k_effort = [255] * self.NUM_JOINTS # Publish and give time to take effect print('[USER] Going to home position...') self.ac_pub.publish(home_msg) time.sleep(2.0) # Step 1: Go to stand-prep pose under user control stand_prep_msg = AtlasCommand # Always insert current time stand_prep_msg.header.stamp = rospy.Time.now # Assign some position and gain values that will get us there. stand_prep_msg.position = [2.438504816382192e-05, 0.0015186156379058957, 9.983908967114985e-06, -0.0010675729718059301, -0.0003740221436601132, 0.06201673671603203, -0.2333149015903473, 0.5181407332420349, -0.27610817551612854, -0.062101610004901886, 0.00035181696875952184, -0.06218484416604042, -0.2332201600074768, 0.51811283826828, -0.2762000858783722, 0.06211360543966293, 0.29983898997306824, -1.303462266921997, 2.0007927417755127, 0.49823325872421265, 0.0003098883025813848, -0.0044272784143686295, 0.29982614517211914, 1.3034454584121704, 2.000779867172241, -0.498238742351532, 0.0003156556049361825, 0.004448802210390568] stand_prep_msg.velocity = [0.0] * self.NUM_JOINTS stand_prep_msg.effort = [0.0] * self.NUM_JOINTS stand_prep_msg.kp_position = [20.0, 4000.0, 2000.0, 20.0, 5.0, 100.0, 2000.0, 1000.0, 900.0, 300.0, 5.0, 100.0, 2000.0, 1000.0, 900.0, 300.0, 2000.0, 1000.0, 200.0, 200.0, 50.0, 100.0, 2000.0, 1000.0, 200.0, 200.0, 50.0, 100.0] stand_prep_msg.ki_position = [0.0] * self.NUM_JOINTS stand_prep_msg.kd_position = [0.0] * self.NUM_JOINTS # Bump up kp_velocity to reduce the jerkiness of the transition stand_prep_msg.kp_velocity = [50.0] * self.NUM_JOINTS stand_prep_msg.i_effort_min = [0.0] * self.NUM_JOINTS stand_prep_msg.i_effort_max = [0.0] * self.NUM_JOINTS # Set k_effort = [1] to indicate that we want all joints under user control stand_prep_msg.k_effort = [255] * self.NUM_JOINTS # Publish and give time to take effect print('[USER] Going to stand prep position...') self.ac_pub.publish(stand_prep_msg) time.sleep(2.0) # Step 2: Request BDI stand mode stand_msg = AtlasSimInterfaceCommand # Always insert current time stand_msg.header.stamp = rospy.Time.now # Tell it to stand stand_msg.behavior = stand_msg.STAND_PREP # Set k_effort = [255] to indicate that we still want all joints under user # control. The stand behavior needs a few iterations before it start # outputting force values. stand_msg.k_effort = [255] * self.NUM_JOINTS # Publish and give time to take effect print('[USER] Warming up BDI stand...') self.asic_pub.publish(stand_msg) time.sleep(1.0) # Now switch to stand stand_msg.behavior = stand_msg.STAND # Set k_effort = [0] to indicate that we want all joints under BDI control stand_msg.k_effort = [0] * self.NUM_JOINTS # Publish and give time to take effect print('[BDI] Standing...') self.asic_pub.publish(stand_msg) time.sleep(2.0) # Step 3: Move the arms and head a little (not too much; don't want to fall       # over) slight_movement_msg = AtlasCommand # Always insert current time slight_movement_msg.header.stamp = rospy.Time.now # Start with 0.0 and set values for the joints that we want to control slight_movement_msg.position = [0.0] * self.NUM_JOINTS slight_movement_msg.position[AtlasState.neck_ay] = 1.0 slight_movement_msg.position[AtlasState.l_arm_ely] = 1.0 slight_movement_msg.position[AtlasState.l_arm_mwx] = 1.0 slight_movement_msg.position[AtlasState.r_arm_ely] = -1.0 slight_movement_msg.position[AtlasState.r_arm_mwx] = -1.0 slight_movement_msg.velocity = [0.0] * self.NUM_JOINTS slight_movement_msg.effort = [0.0] * self.NUM_JOINTS slight_movement_msg.kp_position = [20.0, 4000.0, 2000.0, 20.0, 5.0, 100.0, 2000.0, 1000.0, 900.0, 300.0, 5.0, 100.0, 2000.0, 1000.0, 900.0, 300.0, 2000.0, 1000.0, 200.0, 200.0, 50.0, 100.0, 2000.0, 1000.0, 200.0, 200.0, 50.0, 100.0] slight_movement_msg.ki_position = [0.0] * self.NUM_JOINTS slight_movement_msg.kd_position = [0.0] * self.NUM_JOINTS # Bump up kp_velocity to reduce the jerkiness of the transition stand_prep_msg.kp_velocity = [50.0] * self.NUM_JOINTS slight_movement_msg.i_effort_min = [0.0] * self.NUM_JOINTS slight_movement_msg.i_effort_max = [0.0] * self.NUM_JOINTS # Set k_effort = [1] for the joints that we want to control. # BDI has control of the other joints slight_movement_msg.k_effort = [0] * self.NUM_JOINTS slight_movement_msg.k_effort[AtlasState.neck_ay] = 255 slight_movement_msg.k_effort[AtlasState.l_arm_ely] = 255 slight_movement_msg.k_effort[AtlasState.l_arm_mwx] = 255 slight_movement_msg.k_effort[AtlasState.r_arm_ely] = 255 slight_movement_msg.k_effort[AtlasState.r_arm_mwx] = 255 # Publish and give time to take effect print('[USER/BDI] Command neck and arms...') self.ac_pub.publish(slight_movement_msg) time.sleep(2.0) # Step 4: Request BDI walk walk_msg = AtlasSimInterfaceCommand # Always insert current time walk_msg.header.stamp = rospy.Time.now # Tell it to walk walk_msg.behavior = walk_msg.WALK walk_msg.walk_params.use_demo_walk = False # Fill in some steps for i in range(4): step_data = AtlasBehaviorStepData # Steps are indexed starting at 1 step_data.step_index = i+1 # 0 = left, 1 = right step_data.foot_index = i%2 # 0.3 is a good number step_data.swing_height = 0.3 # 0.63 is a good number step_data.duration = 0.63 # We'll specify desired foot poses in ego-centric frame then # transform them into the robot's world frame. # Match feet so that we end with them together step_data.pose.position.x = (1+i/2)*0.25 # Step 0.15m to either side of center, alternating with feet step_data.pose.position.y = 0.15 if (i%2==0) else -0.15 step_data.pose.position.z = 0.0 # Point those feet straight ahead step_data.pose.orientation.x = 0.0 step_data.pose.orientation.y = 0.0 step_data.pose.orientation.z = 0.0 step_data.pose.orientation.w = 1.0 # Transform this foot pose according to robot's           # current estimated pose in the world, which is a combination of IMU # and internal position estimation. # http://www.ros.org/wiki/kdl/Tutorials/Frame%20transformations%20%28Python%29 f1 = posemath.fromMsg(step_data.pose) f2 = PyKDL.Frame(PyKDL.Rotation.Quaternion(self.imu_msg.orientation.x,                                                      self.imu_msg.orientation.y,                                                       self.imu_msg.orientation.z,                                                       self.imu_msg.orientation.w),                             PyKDL.Vector(self.asis_msg.pos_est.position.x,                                          self.asis_msg.pos_est.position.y,                                          self.asis_msg.pos_est.position.z)) f = f2 * f1           step_data.pose = posemath.toMsg(f) walk_msg.walk_params.step_data[i] = step_data # Use the same k_effort from the last step, to retain user control over some # joints. BDI has control of the other joints. walk_msg.k_effort = slight_movement_msg.k_effort # Publish and give time to take effect print('[USER/BDI] Walking...') self.asic_pub.publish(walk_msg) time.sleep(6.0)

# Step 5: Go back to home pose under user control home_msg = AtlasCommand # Always insert current time home_msg.header.stamp = rospy.Time.now # Assign some position and gain values that will get us there. home_msg.position = [0.0] * self.NUM_JOINTS home_msg.velocity = [0.0] * self.NUM_JOINTS home_msg.effort = [0.0] * self.NUM_JOINTS home_msg.kp_position = [20.0, 4000.0, 2000.0, 20.0, 5.0, 100.0, 2000.0, 1000.0, 900.0, 300.0, 5.0, 100.0, 2000.0, 1000.0, 900.0, 300.0, 2000.0, 1000.0, 200.0, 200.0, 50.0, 100.0, 2000.0, 1000.0, 200.0, 200.0, 50.0, 100.0] home_msg.ki_position = [0.0] * self.NUM_JOINTS home_msg.kd_position = [0.0] * self.NUM_JOINTS # Bump up kp_velocity to reduce the jerkiness of the transition home_msg.kp_velocity = [50.0] * self.NUM_JOINTS home_msg.i_effort_min = [0.0] * self.NUM_JOINTS home_msg.i_effort_max = [0.0] * self.NUM_JOINTS # Set k_effort = [1] to indicate that we want all joints under user control home_msg.k_effort = [255] * self.NUM_JOINTS # Publish and give time to take effect print('[USER] Going to home position...') self.ac_pub.publish(home_msg) time.sleep(2.0) if __name__ == '__main__': rospy.init_node('control_mode_switch') d = Demo d.demo