E-STOP and Enable Robot

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Robot State and E-Stop

The "Robot State" refers to the state variable that shows whether the robot (motors) are enabled or disabled, if the e-stop is engaged, and if there are any hardware errors.

E stop.jpg

Sawyer's Emergency Stop (E-Stop) button (the image showing above) is a hardware stop which will disallow power to the robot components. The E-Stop should always be available when running advanced control programs as a safety precaution. If the robot ever moves unexpectedly, press the E-Stop to prevent anyone from being hurt, or damaging the Sawyer hardware.


Quickstart

Use the Enable Robot Script with various arguments to enable the robot or check its current state.


Overview

The "Robot State" refers to the state variable that shows whether the robot (motors) are enabled or disabled, if the e-stop is engaged, and if there are any hardware errors.


EStop and State Message

Below are various state messages and what they mean and indicate. The third column tells you the Resolution to follow if having a problem and you see this message.

Message EStop State / Error Meaning Resolution
enabled: False Robot is disabled; Power to motors is OFF Enable Robot Script
estop_button: 1 E-Stop button is engaged or loose.
estop_button: 2 S/W Stop was called.
estop_button: 3 E-Stop button now disengaged (released), but not reset yet.

EStop States

Below is the raw contents of the [intera_core_msgs/AssemblyState][intera_core_msgs-AssemblyState] Message from the /robot/state topic. The contents explain the meaning of the estop_button and estop_source fields. 

$ rosmsg show intera_core_msgs/AssemblyState -r
bool enabled             # true if enabled
bool stopped             # true if stopped -- e-stop asserted
bool error               # true if a component of the assembly has an error
#
= The following are specific to the robot top-level assembly: =
uint8  estop_button      # One of the following:
  uint8   ESTOP_BUTTON_UNPRESSED = 0   # Robot is not stopped and button is not pressed
  uint8   ESTOP_BUTTON_PRESSED   = 1
  uint8   ESTOP_BUTTON_UNKNOWN   = 2   # STATE_UNKNOWN when estop was asserted by a non-user source
  uint8   ESTOP_BUTTON_RELEASED  = 3   # Was pressed, is now known to be released, but robot is still stopped.
#
uint8  estop_source      # If stopped is true, the source of the e-stop.  One of the following:
  uint8  ESTOP_SOURCE_NONE      = 0   # e-stop is not asserted
  uint8  ESTOP_SOURCE_USER      = 1   # e-stop source is user input (the red button)
  uint8  ESTOP_SOURCE_UNKNOWN   = 2   # e-stop source is unknown
  uint8  ESTOP_SOURCE_FAULT     = 3   # MotorController asserted e-stop in response to a joint fault
  uint8  ESTOP_SOURCE_BRAIN     = 4   # MotorController asserted e-stop in response to a lapse of the brain heartbeat

This table shows example scenarios of various E-Stop states and the corresponding robot state message that would be published.

Message EStop State / Error Resolution 
enabled: True
stopped: False
error: False
estop_button: 0
estop_source: 0
(Good) Robot is enabled; E-Stop is connected and disengaged. 
enabled: False
stopped: False
error: False
estop_button: 0
estop_source: 0
(Good) EStop connected and not triggered; robot disabled; or robot reset. Use the Enable Robot Script to enable the robot:
 $ rosrun intera_interface enable_robot.py -e

enabled: False
stopped: True
error: True
estop_button: 1
estop_source: 1
E-Stop is engaged; Or E-Stop has come loose. Disengage the E-Stop, make sure it is firmly connected to the robot, then reset the robot. 
enabled: False
stopped: True
error: False
estop_button: 3
estop_source: 1
E-Stop is released (or reconnected), but not reset. Reset the robot, then try again:
 $ rosrun intera_interface enable_robot.py -r

enabled: False
stopped: True
error: True
estop_button: 2
estop_source: 1
User triggered (Software) E-Stop. Reset the robot, then try again:
 $ rosrun intera_interface enable_robot.py -r


Enable Robot

The enable robot example program will allow you to enable/disable/reset/stop the robot. You can also get the robot's current state. The robot must be enabled in order to control the motors. In order to control Sawyer's arms, the robot must be put in the 'Enabled' state. Enabling the robot provides power to the joint motors, which are initially in the 'Disabled' state on start-up or after a serious error, such as an E-Stop (Emergency-Stop). The robot's 'State' can be checked with the enable_robot tool.

Note: If an error has occurred, the robot state may need to be reset (-r) before being enabled again.


Basic Usage

To Enable the robot: 

$ rosrun intera_interface enable_robot.py -e

To Disable the robot: 

$ rosrun intera_interface enable_robot.py -d


Functions

To get help on enable_robot use the -h argument: 

$ rosrun intera_interface enable_robot.py -h

Help screen:

enable_robot.py [ARGUMENTS]

  • h, --help show this help message and edit
  • s, --state Print current robot state
  • e, --enable Enable the robot
  • d, --disable Disable the robot
  • r, --reset Reset the robot
  • S, --stop Stop the robot


Robot State

To get the current robot state use -s: 

$ rosrun intera_interface enable_robot.py -s

enabled: False
stopped: False
error: False
estop_button: 0
estop_source: 0

The state output above indicates a normal (all-clear) status, as you would see after power-up. Once you enable the robot to control the arms, you should see the same status but with enabled: True.


Enable Robot

Use -e to enable the robot. 

$ rosrun intera_interface enable_robot.py -e

The robot state enabled field should then switch to True.


Disable Robot

Use -d to disable the robot. 

$ rosrun intera_interface enable_robot.py -d

The robot state enabled field should then switch to False.


Reset

Use -r to reset the robot after an error (if the robot state gives error: True). 

$ rosrun intera_interface enable_robot.py -r

This should clear the error field, setting it back to error: False.


Stop

Use -S (capital S) to stop the robot. This is similar to a "software" E-Stop. 

$ rosrun intera_interface enable_robot.py -S

This will disable the robot and also cause the stopped field and the error field to go True. You will need to reset the robot before enabling it again.


Troubleshooting

Robot fails to enable or reset

If your robot "fails to reset" when you run robot enable, the first thing to check is if the E-Stop is engaged: 

$ rosrun intera_interface enable_robot -s

enabled: False
stopped: True
error: True
estop_button: 1
estop_source: 1

If the estop_button: field says '1', it means the E-Stop is engaged (from [intera_core_msgs/AssemblyState][intera_core_msgs-AssemblyState] message: uint8 ESTOP_BUTTON_PRESSED=1). Disengage the E-Stop by twisting the red top until it 'pops'-up, then try resetting the robot. 

$ rosrun intera_interface enable_robot -r
$ rosrun intera_interface enable_robot -e


More Information

See the Enable Robot Script for more information about the robot's state and dealing with errors.

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