What is a Remote Weapons Station?
A Remote Weapons Station (RWS) is a remotely operated weaponry platform that utilizes light and medium caliber artillery shells. Typically, an RWS contains sensing components (angular rates, accelerations, etc.), motor drives, a turret, and a computer. Today, companies like Electro Optic Systems Pty Ltd are patenting next-generation Electro Optic RWS that are gyro-stabilized, combat-ready and built for precision targeting (1).
Since the two most essential characteristics of an RWS are aiming speed and accuracy, advanced stabilization methods are required to ensure that targets are correctly dealt with. The most critical component in this task is the gyroscope.
Gyroscopes for Stabilization
The gyroscope accounts for the pan and tilt model used by RWS. Spherical data (theta, phi, and the range – rho) is key to stabilizing this system because of the nature of the application. Angle theta is used to stabilize the tilt motor, angle phi is used to direct the pan motor, and rho (distance) is typically calculated using a laser range finder (2).
Improving the stability of weapons stations is a constantly adapting job. Creative uses of both sensors and structures are slowly increasing accuracy over distance. The United States Army filed for an anti-vibration mount for RWS and turrets in July 2019 to provide a more stable platform for gyroscopes to better read and account for the pan and tilt model (3). Since vibrations can severely saturate weapon modeling algorithms, it will take both the right platform and the correct type of ruggedized sensor to push development. But what is the correct sensor?
History in the Making – From Mechanical to MEMS
The first mechanical gyro to be used for stabilization appeared during WW II. This gyro was invented by Charles Stark Draper (4) to stabilize the MK 14 Gunsight (1942) for ship-based anti-aircraft guns. This gun-laying system successfully accommodated the roll and pitch of the vessel while also tracking and “leading” the gun’s aim against a fast-moving aircraft. Sperry Corp. built 100,000 of these systems based on Draper’s design throughout WW II.
This first mechanical gyro for stabilization also caught the eye of editorial publishers. Gold Sanders featured it in an article titled “The Little Top That Aims a Gun” in the July 1945 edition of Popular Science (5).
Fun Fact: In 1961, Draper was awarded a contract by NASA and the United States government to develop the first Inertial Navigation system; a mechanical “floated” gyro-based system that was then responsible for putting men on the moon (4).
After the invention of the mechanical gyro came the Ring Laser Gyroscope (RLG). The first experimental RLG was demonstrated in the U.S. by Macek and Davis in 1963 (6). One of the initial largest benefits of the RLG (especially in the world of weaponry stabilization) was that the RLG was affected minimally, if at all, by accelerations and shock.
In 1976, Victor Vali and Richard Shorthill demonstrated an operational Fiber-Optic Gyroscope (FOG) for the first time. By the end of the 1980s, many hesitated to use the RLG due to its larger size, weight, and power requirements than new FOG devices. Another benefit of FOGs during this time was their immunity to radiofrequency and electromagnetic interferences. With fear rising for a new generation of electronic warfare and media outlets like the New York Times speaking of the imminent disaster from Nuclear electromagnetic pulses (NEMP) (7), military suppliers began to look at the FOG with increasing interest.
In 2004, FOG devices were utilized in the first official RWS manufactured for the U.S. Army under the “Common Remotely Operated Weapon Stations (CROWS)” program. By 2010, many initially smaller companies, like KVH, were able to win multi-million dollar U.S. Army contracts using this fiber-optic technology (8).
So what happened to make the now recognized Microelectromechanical Systems (MEMS) take over the market?
MEMS, The Future of Stabilization
The first stepping stone to create the well-known MEMS gyroscope was the double gimbal gyroscope, which became the silicon-on-glass tuning fork gyroscope developed in 1984 (9). This technology allowed Charles Draper to produce the first MEMS gyroscope in Draper Laboratory in 1992 (4). Although this unit’s performance was mediocre at best, its initial and immediate benefits were lower manufacturing costs, power requirements, and smaller size than RLG and FOG units.
Also, in 1992, the Defense Advanced Research Projects Agency (DARPA) identified MEMS sensors as an emerging technology critical to the nation’s security needs. As a result, DARPA formally established the MEMS Program (10).
This investment by the United States Department of Defense (DOD) led to funded research that advanced at an increased rate, making MEMS technology more robust and with increasingly better performance. Gaining traction, MEMS began to shine over conventional FOG and RLG technologies. Here is a summary of MEMS technology improvements and advancements that came as a result of the MEMS Program (11):
1. Space Savings
MEMS devices are highly space-efficient. Available in the form of chips, these devices can be fitted on electronic circuit boards as small as a few millimeters in width.
2. Digital Interfacing
Digital signaling meant signals could now be encrypted, and users could rewrite data formats in hours rather than weeks. Additionally, digital interfacing meant that two-way communication could be established instead of using previous methods, which required a cable for each direction of communication.
3. Performance
Variable performance allows users to meet application needs without paying extra. Evolving technology means improvements in the performance of MEMS gyroscopes. Tactical and Navigational performance are now available solutions.
4. Rugged
MEMS has no moving components, unlike Dynamically Tuned Gyroscopes (DTG) or RLG, and hence, completely maintenance-free.
5. Cost-Effective
As a whole, MEMS components are available at a fraction of the cost of FOG or RLG. Since MEMS devices have such variable performance, users can always buy to specification and not overspend. Additionally, MEMS device manufacturing processes are much cheaper than FOG or RLG.
The “Gun-Hard” MEMS
The first known use of MEMS gyroscopes for weapon stabilization dates back to 1994 on the Extended Range Guided Munition (ERGM). The U.S. Navy started this program, and Raytheon fulfilled the contract (12). As a result of this program, MEMS gyroscopes quickly evolved. One of the projectiles used for this project, the EX-171, is shown below (13).
By 2002, a new MEMS-based gyroscope solution was emerging, designed for stabilization and orientation monitoring in the advanced weapon industry. These MEMS emerged due to DARPA launching two new programs: Nano Mechanical Array Signal Processors (NMASP) and Harsh Environment Robust Micromechanical Technology (HERMIT). Built to withstand intense environments, many of these systems took on the name “GunHard” IMUs (14), and by 200,4 private companies such as Honeywell, AIS Inc, Raytheon, Inertial Labs Inc., and Colibrys (later purchased by Safran in 2013) were marketing their new lost-cost replacements to traditional FOG and RLG-based solutions for guided munitions and remote weapons stations.
Recent Innovations to RWS
Stabilization Upgrades
Vibrations will always negatively affect any system by saturating data to some extent. To combat this, Curtiss-Wright has recently released a Turret Drive Servo System (TDSS) that mitigates unwanted vibrations ansubstantially upgradesde to revolutionize stabilization for turrets and pointing systems (15). This system (photographed below) is installed as a kit and can be custom-ordered for many platforms.
Weapon Enhancements
Another American defense company, EOS Defense Systems USA, Inc., announced a new RWS built for more than just low-power artillery. This RWS, the EOS R400S Mk2 remote weapon (shown below), is an electro-optically stabilized weapons station that fires Javelin missiles (FGM- 148) for anti-tank applications in addition to the more traditional Northrup Grumman M230LF Bushmaster gun (16).
Carrier Adaptability
Outside the United States, companies like Leonardo SpA in Spain are creating RWS designed for more than ground vehicles. These automatic aiming systems incorporate target detection, tracking, and autonomous operation, specifically for fixed-wing aerial platforms. Approved within the last year but initially filing to patent their design in 2011 (17), Leonardo SpA continues to innovate and improve systems by predicting future technologies that will be used in the industry almost a decade later.
Inertial Labs Solutions
TAG-200 and TAG-300
The TAG product line consists of two-axis and three-axis gyroscopes specifically engineered to offer highly accurate real-time tracking of an object’s angular velocities. As a result, these products allow for the offset of angular rates to factor in turn and tilt, stabilizing electro-optical systems and RWS.
The TAG product line enables Inertial Labs to better serve customers with highly specialized projects that track angular rate data only, offering an exponentially smaller and lighter product ideal for limited space and weight capacity, whether airborne or ground-based. By comparison, fully integrated inertial measurement units (IMU) can be used in various situations, tracking multiple data types to provide data on orientation, position, and velocity.
The TAG-200 and TAG-300 feature Inertial Labs MEMS Tactical grade gyroscopes with a 2 °/hour bias in-run stability with an Angular Random Walk (ARW) of 0.08 °/√hour. The image above shows the results of an Allan Variance test for measuring gyroscope noise.
IMU-P Tactical
Users need to take advantage of more than gyroscope data for other applications. The IMU-P Tactical utilizes tactical-grade gyroscopes and accelerometers. Depending on your application, Inertial Labs offers two different tactical grade solutions, each with benefits. The IMU-P Tactical-A offers a sensor-fused gyro-based solution with 1 °/hour gyro bias in-run stability with an ARW of 0.2 °/√hour. Alternatively, the IMU-P Tactical-S has a lower ARW of 0.08 °/√hour with a gyro bias-in-run stability of 2 °/hour. End-users continue to benefit from the sensor
solutions from Inertial Labs by only paying for what is needed to meet project requirements. Why pay more when it is not required? The IMU-P Tactical-A was tested in an Allan Variance test for ARW and VRW using the configurable 15g accelerometer. The results of this test can be seen in the plot below.
Users need to take advantage of more than gyroscope data for other applications. The IMU-P Tactical utilizes tactical-grade gyroscopes and accelerometers. Depending on your application, Inertial Labs offers two different tactical grade solutions, each with benefits. The IMU-P Tactical-A offers a sensor-fused gyro-based solution with 1 °/hour gyro bias in-run stability with an ARW of 0.2 °/√hour. Alternatively, the IMU-P Tactical-S has a lower ARW of 0.08 °/√hour with a gyro bias-in-run stability of 2 °/hour. End-users continue to benefit from the sensor solutions from Inertial Labs by only paying for what is needed to meet project requirements. Why pay more when it is not required? The IMU-P Tactical-A was tested in an Allan Variance test for ARW and VRW using the configurable 15g accelerometer. The results of this test can be seen in the plot below.
IMU-NAV-100
Over the years, MEMS devices have continued improving performance and accessibility. The navigational grade IMUs have been reserved for systems that utilize FOGs and RLGs for years. In recent years, however, Inertial Labs has continued to move the ball forward, bringing end users the highest-performing devices on the market at the lowest cost.
The all-new IMU-NAV product line is the latest addition to the Inertial Labs Advanced MEMS sensor-based family. This fully calibrated, temperature compensated, mathematically aligned to an orthogonal coordinate system does not fall short of the Inertial Labs motto: “Attitude is Everything.” It is manufactured to impress.
The IMU-NAV-100 is the first of three navigational grade IMUs from Inertial Labs. Allan Variance tests have proven performance through repeatable trials. Plots for the gyroscope and accelerometer noise for the IMU-NAV-100 can be seen below. The table at the bottom of the page also features key performance characteristics between the three new models of navigation-grade IMU’s from Inertial Labs.
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