Updated README

Author: tabula-rosa

README.md

@@ -35,7 +35,15 @@ python scripts/command_joints.py
 
 The robot can be safely shut down by pressing Ctrl+c on the terminal that is running `position_control.launch`. The robot will move into a safe joint configuration before removing motor power.
 
+# Safety
+1. Never stand or place objects within the working space of the robot.
+2. Always assume the robot will behave unexpectedly and antagonistically. Plan accordingly so that your experiments are always conducted safely.
+3. If you need to power cycle the motors, read the Motor Lockup section below **BEFORE** power cycling.
+4. Before running experiments, know exactly what commands to run to expediently shut down the robot. (Ctrl+c in the terminal running the `position_control.launch` script.)
+
 # Troubleshooting
+
+## Can't Connect to Device
 The argument `device_name` in `position_control.launch` needs to be updated to the actual device being used on your platform, which is the USB device that the U2D2 controller is using. If the default parameter in `position_control.launch` is not valid, the following command will show the device name:
 ```
 dmesg | grep 'attached to tty'
@@ -46,5 +54,8 @@ The message will appear similar to:
 ```
 In this case, `ttyUSB0` is indeed the device name. Change your launch script as appropriate based on the actual device your platform is using.
 
+## Motor Lockup
+If the robot stops following the joint commands, you may need to power cycle the motors. Hold the robot arm **BEFORE YOU DISCONNECT MOTOR POWER** because the arm will collapse otherwise. As you hold the arm, carefully unplug the USB controller and the power adapter. Put the arm back in a safe configuration, and reconnect both the controller and the power adapter.
+
 # Attribution
 Thanks to Adithya Murali (@adithyamurali) for creating the skeleton and basic usage scripts.