If the robot collides your hand stops moving. If you keep trying to move in that direction the master will not allow you to move. Continuing to try and move shuts down the system. You do not feel the force, but your hand not being able to move does reflect an obstacle.
Yes, the computer can detect a conflict when an arm hits up against something, but the operator doesn't feel anything. You can see that the arm doesn't move as you want it to and, if you persist in the movement, the machine shuts down and has to be reset.