INTRODUCTION
> Previous work in Autonomy for small unmanned ground vehicles
CURRENT WORK
Many advances have been made in autonomy for unmanned ground vehicles (UGVs) but most of these advances have been for large UGVs only, in that the sensors required for autonomy are typically large, heavy and require a significant amount of power. Because of the size, weight and power restrictions imposed by a man-portable UGV advances in autonomy have been very limited.
The SPAWAR Systems Center San Diego (SSC San Diego) has previously developed a waypoint navigation capability for small robots. That system required an operator to monitor a live video feed from the vehicle to ensure it did not strike any obstacles in its path. Now SSC San Diego in cooperation with the NASA Jet Propulsion Laboratory (JPL) has developed a miniature obstacle detection sensor suitable for small robots. SSC San Diego has also developed the obstacle-avoidance algorithms to navigate autonomously around obstacles.
In 1999 under the Joint Robotics Program (JRP) Man-Portable Robotic Systems (MPRS) project, SSC San Diego developed a small UGV intended for use by Army engineers for tunnel, sewer, cave, and urban structure reconnaissance. As originally developed, the UGV (called the URBOT for Urban Robot, Fig. 1), was strictly tele-operated from a wearable operator control unit (OCU) (Fig. 2). This allowed the soldier to manually drive the vehicle into high-risk areas and receive video feedback to assess the situation before entering. The system was used in several experiments at Fort Leonard Wood, MO, Fort Drum, NY, and Fort Polk, LA.1
Figure
1. MPRS URBOT Figure 2.
MPRS URBOT OCU
In 2002 SSC San Diego was tasked with developing a GPS-waypoint-navigation
capability for the URBOT. The requirement was for a small robot to semi-autonomously
navigate undetected several miles into a combat area. The user was concerned
about operator fatigue if the system was to be tele-operated the entire
distance. The concept of operations was to pre-plan the mission using high
resolution imagery, and then to select a path that appeared to obstacle-free.
The operator would monitor the video feed from the vehicle and watch for
obstructions, taking manual control of the vehicle only when necessary to
drive around an obstacle. Under this task, SSC San Diego developed one of
the first waypoint navigation systems for UGVs of this size2, as well as
the Multi-robot Operator Control Unit (MOCU) which continues to evolve,
and is now the core command and control station for the Spartan ACTD. Figure
3 shows a screen shot of an early version of MOCU. The planned route is
in blue, the raw GPS data (with large spikes) is red, and the actually URBOT
path (determined by the Kalman Filter) is in magenta.
Figure 3. Screen shot of an early version of MOCU
Autonomous obstacle avoidance (OA) was not attempted for this task primarily because of the lack of adequate sensors that met the size, weight, power and fidelity requirements of a rugged, man-portable system. A great deal of successful work has been done OA for larger UGVs, but those systems rely on sensors that are large, power-hungry, and require CPU intensive operations and are inappropriate for a small robots.
In recent years it has become increasingly clear that small robots provide a needed capability to the warfighter. It is also clear that as small robots become more prevalent the requirement for higher levels of autonomy will increase [3]. In Iraq soldiers are using and depending on small robots daily but only in situations that are controlled and pose a serious risk of injury or death. One reason for this is that all of the small robots currently fielded are strictly tele-operated. These tele-operated systems require the operator’s full attention and prevent him from maintaining his own personal security. The primary example of this is in Improvised Explosive Device (IED) disposal. In this application the risk to the soldier in manually disposing of the IED is huge. In most cases IED disposal is also done in a relatively controlled environment where the robot operator is in an area secured by a force protection team.
In order for small robots to become more useful in more tactical scenarios, they must have autonomous navigation capabilities. This is also the case for applications that would make use of teams of small robots, such as land mine clearance, communications relaying, etc. One of the most basic building blocks for any autonomous behavior is robust obstacle avoidance.
The requirement for developing sensors and autonomous capabilities for small platforms is also influenced by the platforms themselves. The primary small robot acquisition programs currently underway within the DoD are the Future Combat Systems (FCS) Soldier Unmanned Ground Vehicle (SUGV) and the NAVEOD Man-Transportable Robotic System (MTRS). The FCS SUGV platform will be approximately 25% smaller than the iRobot Packbot. In order for that vehicle to maintain its mobility (including self-righting) and survivability, any sensor system must be integrated into a very small payload area between the tracks. This will require the sensors to be extremely small by today’s standards and virtually eliminates most of the sensors currently being used in academic and scientific research.