Robotics Publications

A Brief History of Robotics in Physical Security*

Commander H.R. (Bart) Everett (Rtd)

Space and Naval Warfare Systems Center, San Diego, D3701
San Diego, CA 92152-7383

* A condensed version of this paper appeared as "Breaking down the Barriers" in Unmanned Vehicles, Vol. 3, No.1, February-April 1998.

From a performance standpoint, the perceived benefits of a robotic security or surveillance capability are numerous and well documented: 1) humans are removed from direct exposure to potentially dangerous situations; 2) robotic systems can perform many security and surveillance functions more effectively than humans; 3) robots don’t get bored and thereby inattentive during long hours of surveillance; and 4) robots don't participate in "inside jobs."

In addition, the robotic site-security application has certain advantages relative to more ambitious battlefield scenarios: 1) the operating environment is known in advance and can to some degree be tailored to support robotic installation; 2) experience-based costs of conventional security measures and documented inventory shrinkage together provide a sound and credible basis for cost/benefit tradeoffs.

Nevertheless, almost 20 years have elapsed since both private industry and the US Department of Defense began to take an active interest in pursuing this promising field, and preliminary systems are only just now achieving the required degree of practicality to warrant serious consideration. This article provides a historical review of some noteworthy endeavors followed by a short survey of currently available systems (see Table 1).

Historical Prototypes

A number of pioneering efforts dating from the very early 1980s are significant in terms of their influence on follow-on systems as they exist today.

Developed at the Naval Postgraduate School, Monterey, CA, during the 1980-1982 time frame, ROBART I by nature of its early debut faced the full gamut of technical challenges. Intended only as a crude feasibility demonstration for the concept of a fully autonomous indoor security robot, this early research effort (Figure 1) made no attempt to maintain an absolute world model of its surroundings. Instead, a rather simplistic relative model encoded the inter-relationships of rooms along a hallway in the form of a linked-list representation.

Figure 1. ROBART I was developed at the Naval Postgraduate School in Monterey, CA (1980-1982).

From a security perspective, ROBART I could only detect the movement of suspected intruders, with no subsequent assessment capability to filter out nuisance alarms. The principle sensing mechanism was a head-mounted passive infrared (PIR) motion detector. Three optical motion sensors provided additional detection capability under conditions where sufficient ambient lighting was available.

In retrospect, ROBART I is significant in that it represents the first actual demonstration of a fully autonomous security robot capable of: 1) detecting potential intruders with a variety of motion sensors; 2) moving unassisted throughout a semi-structured environment while avoiding obstacles; and 3) automatically seeking out and docking with a recharging station when its batteries began running low.

ROBART II (Figure 2), the second-generation follow-on to ROBART I, was developed in Springfield, VA, over the period from 1982 until 1986, when it was made available to the Naval Ocean Systems Center (now SPAWAR Systems Center), San Diego, CA. The robot’s distributed architecture of 13 processors in conjunction with its significantly augmented sensor suite (seven different types of motion detectors) made it ideal as a test-bed for enhanced navigation and intelligent security assessment.

Figure 2. ROBART II (1982-1992) employed a total of 132 external security and navigation sensors.

The addition of an absolute world model allowed ROBART II to: 1) determine its location in world coordinates; 2) create a map of detected obstacles and potential intruders; and 3) perform multi-sensor fusion on the data from its security and environmental sensors. This last feature facilitated the implementation of a sophisticated threat-assessment algorithm that significantly increased the probability of detection while virtually eliminating nuisance alarms.

The first outdoor robotic sentry/surveillance system was the PROWLER (Programmable Robot Observer With Logical Enemy Response), developed between 1983-1985 by Robot Defense Systems (RDS) out of Thornton, CO. The PROWLER was initially implemented as a purely tele-operated vehicle, based on Standard Manufacturing’s diesel-powered six-wheeled hydrostatic-drive chassis (Figure 3). RDS subscribed to an incremental evolutionary upgrade approach to allow near-term deployment of limited-capability PROWLER vehicles in very structured operating conditions, with increased sophistication intended for follow-on applications as the supporting technologies matured.

The daunting task of achieving an autonomous navigation capability in an outdoor environment prior to the advent of a practical global positioning system (GPS) capability was effectively bounded by constraining initial applications to very structured road- or fence-following scenarios. In 1985 the PROWLER successfully demonstrated an ability to autonomously follow a non-linear 500-foot fence line in a test for the US Army at Fort Lewis, WA. The chain link fence was slightly modified through insertion of retro-reflective strips to facilitate detection by the PROWLER’s side-looking laser rangefinder. Application-specific security sensors included a turret-mounted surveillance camera that could be vertically extended up to 28 feet using a special telescoping mast.

The evolutionary-upgrade philosophy adopted by the RDS engineering team, geared towards gradually enhancing the autonomy of their initially tele-operated remote platform as the supporting technologies advanced, was clearly the correct approach from a technical perspective. But transitioning from a start-up role initially funded by small business grants to the production of a viable revenue-generating product was a tough row to hoe, given the technological hurdles of the time. The company filed Chapter 11 in 1986 after an unpaid supplier forced the firm into involuntary liquidation.

Development of the Denning Sentry as an indoor security robot by Denning Mobile Robots of Woburn, MA began in August of 1983. A navigational system based on pre-determined paths marked by near-infrared optical beacons affixed to walls at the end of each path segment proved more than adequate to get the system up and running in very structured environments. The incorporation of recently introduced Polaroid ultrasonic rangefinders improved the navigational solution by allowing the robot to measure its offset as it approached a wall structure, while simultaneously supporting a fairly robust obstacle detection capability. More importantly, the ranging sensors facilitated later development of a powerful wall-following algorithm that reduced dependence on the optical beacon system, increasing flexibility in the event of required path changes and reducing the need to modify the robot’s environment.

Figure 4. The Denning Sentry navigated using a combination of optical beacons and ultrasonic wall following.

On the security side of things, Denning was the first to address the issue of motion detection from a moving platform, heretofore one of the major weaknesses of a mobile robotic security system. Denning engineers collaborated with nearby Alpha Industries on the development of an innovative Doppler microwave motion detector specifically modified for use on a moving platform. The concept was simple: provide a programmable notch filter that would block the Doppler return associated with the robot’s own forward velocity. Unfortunately, the broad effective beam width and multiple harmonics associated with the emitted energy collectively precluded a single discrete Doppler return being induced for a given platform speed, rendering this hypothetical approach impractical under real-world conditions.

Denning’s engineers, unfortunately, were facing the full spectrum of technical challenges as pioneers in a brand new field, simultaneously burdened with too much promised too soon by sometimes over zealous management. While the sophistication of their navigational software grew at a respectable pace, less attention was paid to assessing the data collected by the robot’s motion sensors, thereby limiting the effectiveness of their intrusion detection capability even while the platform was stationary. Ultimately the company went out of business, to be briefly revived later as Denning Branch International Robotics, but with an initial focus on applications other than security (i.e., material handling).

Current Systems

Actual fielding of practical robotic security systems has already begun for interior applications, and expansion into exterior environments is foreseeable in the very near future. The principle contenders in this race are briefly described in the following sections.

The Mobile Detection Assessment and Response System (MDARS) is a joint Army-Navy development effort to provide an automated intrusion detection and inventory assessment capability for use in DoD warehouses and storage sites. The program is managed by the Physical Security Equipment Management Office (PSEMO) at Ft. Belvoir, VA, with overall technical direction provided by the Navy’s SPAWAR Systems Center, San Diego, CA. The patrolling MDARS platforms: 1) detect anomalous conditions such as flooding or fires; 2) detect intruders; and 3) determine the status of inventoried items through the use of specialized RF transponder tags. Separate development efforts target warehouse interiors and outdoor storage areas.

Initiated in 1988, the MDARS Interior program utilizes the K2A Navmaster mobility base developed by Cybermotion, Inc., of Roanoke, VA, equipped with additional collision avoidance, intruder assessment, and product inventory subsystems. A Broad Agency Announcement (BAA) contract was awarded to Cybermotion in 1995 to develop a significantly improved intruder detection sensor package with an integrated camera pan-and-tilt mechanism, shown in Figure 5. Simultaneous control of two robots patrolling nightly within an interior warehouse environment has been demonstrated for over two years at a beta-test facility at Camp Elliott in San Diego, CA. Two additional robots have been operational for almost a year in an Early User Appraisal installation within a Defense Logistics Agency warehouse at Anniston Army Depot in Alabama. The MDARS-Interior program is scheduled to transition to Engineering Development in early 1998 with a formal request for proposals (RFP) being issued shortly thereafter, and operational fielding in the year 2000.

Figure 5. The MDARS-Interior robot with the enhanced SPI-02 security sensor suite on patrol at Camp Elliott.

The MDARS-Exterior Program, initiated in 1993, awarded a BAA contract for the development of the outdoor remote platform (Figure 6) to Robotic Systems Technology (RST), Westminster, MD. The mobility base is a rugged four-wheel hydrostatic-drive diesel-powered vehicle equipped with active-laser, ultrasonic-sonar, millimeter-wave-radar, and stereo-vision sensors for collision avoidance. A formal demonstration of autonomous navigation along straight-line path segments under differential GPS control was conducted at the contractor’s facilities in October 1996. Automatic collision avoidance and limited intruder sensing (using image-stabilized video motion detection) was demonstrated in September 1997 at the DoD Force Protection Equipment Demonstration held at the Marine Corps Air Station in Quantico, VA. Additional efforts will focus on autonomous transit of non-linear path segments and fully integrated intrusion detection employing both video and Doppler radar.

Figure 6. The MDARS-Exterior platform patrolling at the DoD Force Protection Equipment Demonstration in Quantico, VA.

The first Cyberguard SR2 platform was introduced by Cybermotion in 1990, based on their three-wheel synchro-drive K2A Navmaster autonomous mobility base, which had been commercially available for material handling and research applications since 1984. Early Cyberguard models were equipped with environmental sensors and a CCD camera that relayed real-time video over an analog RF link back to a central security console, where a guard could remotely take control of camera pan-and-tilt functions if so desired. Continuous time-lapse video recording was accomplished locally onboard the robotic vehicle for archive purposes, but no automated motion sensors were initially employed.

In 1994 the product was enhanced with the addition of a rotating intrusion detection sensor suite called the Security Patrol Instrumentation (SPI) module, developed under a Cooperative Research and Development Agreement (CRADA) with the Naval Ocean Systems Center. The first-generation SPI-01 was a significant improvement from a cost/producability standpoint over the multi-sensor staring-array approach employed on ROBART II and the early MDARS Interior prototypes, with essentially the same operational capabilities. The introduction of the upgraded six-wheel-drive K3A Navmaster vehicle spawned the Cyberguard SR3 option in 1996 Figure 7). A much-improved security sensor package (see again Figure 5) was developed under the MDARS Interior BAA contract and made commercially available as the SPI-02 in late 1997.

Figure 7. The Cybermotion Cyberguard SR3 based on the K3A platform and SPI-01 security sensor package.

The ROBART series of research prototypes has served the US Navy in developing the component technologies needed in support of the MDARS program. While ROBART I could only detect a potential intruder, ROBART II could both detect and assess, thereby increasing its sensitivity with a corresponding reduction in nuisance alarms. As the third-generation prototype, ROBART III is specifically intended to demonstrate the feasibility of automated response, using (for purposes of illustration only) a pneumatically powered six-barrel Gatling-style weapon that fires simulated tranquilizer darts or rubber bullets (Figure 8).

Figure 8. The prototype automated response robot ROBART III under development at SPAWAR Systems Center.

For increased versatility as a response vehicle, the navigation scheme has been specifically modified to support supervised autonomous operation in previously unexplored interior structures. A "human-centered mapping" strategy is employed to ensure valid first-time interpretation of navigational landmarks as the robot builds its world model. The accuracy of the robot’s real-time position estimation (and ultimately the model representation) is significantly enhanced by an innovative algorithm which exploits the fact that the majority of man-made structures are characterized by parallel and orthogonal walls.

Conclusion

After almost 20 years of extensive development by private industry, academia and the Department of Defense, widespread practical application of intelligent security robots is now an achievable reality for indoor environments, with exterior scenarios soon to follow. In addition to the well touted advantages of improved effectiveness and reduced manning for traditional security roles, more recent attention has been afforded to automated inventory functions using off-the-shelf interactive RF transponder tags attached to sensitive or high value items. The unfortunate patterns of increased theft, violence, and even terrorism emerging throughout society in general, coupled with escalating costs of manpower and training, clearly suggest a sustained interest in this evolving alternative approach to security is very much in order.

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Robotics at Space and Naval Warfare Systems Center, San Diego

Last update: 22 April 1998.
nguyenh@spawar.navy.mil