Description:
OBJECTIVE: Develop a lightweight agile motion base having a high axial load capacity and capable of high precision pointing over a small range of angular displacements. Such a mechanism would enable lightweight stabilized mounts for the forward firing weapons and laser designators used onboard military aircraft and ground vehicles. DESCRIPTION: Problem: Military helicopters such as the MH-6, OH-58, UH-1, MH-60M DAP, and ARH-70 employ fixed forward firing machine guns and auto cannons as weapons. These installations are lightweight and simple, but require the pilot to point the aircraft with high precision in order to hit their targets. Many ineffective rounds are expended due to unexpected motions encountered in the dynamic flight environment of combat. Turreted systems such as that used on the AH-64, and pintle mounted systems such as used in the doors / windows / ramps of AH-1, UH-60, CH-47, CH-53, and V-22 allow off-axis shots but are an order of magnitude heavier than fixed gun mounts and are also subject to wasted rounds due to aiming errors during dynamic flight. The wasted rounds mean heavier ammunition loadouts are required to do the mission, and also increase the risk of collateral damage. The standard of performance for aerial gunnery from an OH-58D is to achieve at least one hit out of 70 shots fired at a wheeled vehicle between 800 1200m distant (see ref 1). This improves to one hit in 30 shots for the AH-64 with a stabilized gun turret using current technology. Some OH-58D flight crews consider their machine guns to be area suppression weapons rather than point target weapons, preferring to use expensive guided missiles (see ref 2) in order to minimize collateral damage (see ref 3). Modern technology enables highly accurate stabilized weapons turrets by incorporating direct-drive brushless stepper motors, lightweight and stiff composite gimbal assemblies, and computerized stabilization / fire controls (see references 4-6). However, these gimbal / motor assemblies are still too heavy for application as stabilized mounts for forward firing guns. Payoff: The resulting Agile, Small-deflection, Precision (ASP) Motion Base would serve as the heart of a stabilized mount for forward firing weapons. Such a mount would allow precision pointing of the weapon throughout the firing sequence, reducing the number of shots required. Fewer shots required results in more stowed kills per loadout, or lighter weight ammo loads with a corresponding improvement in aircraft lift and reduction in sustainment costs. Fewer round fired also minimizes the risk of collateral damage. Technical Approach: The ASP motion base should be capable of small (7 degrees ) azimuth and elevation deflections at low (<10 Hz) bandwidths to compensate for inaccuracies in aircraft pointing ability and / or play in any recoil mechanisms employed. The ASP motion base must also have a precise position control capability to enable good performance when driven by a stabilization algorithm and when subjected to the gun firing and aircraft maneuver loads. The fundamental design of the ASP motion base must be scalable for the weight and recoil forces of the full range of guns / cannons currently used on US military rotorcraft. Integrating the actuation system with the structure may reduce weight and hysteresis. Ideally, the ASP motion base will also incorporate a highly efficient integrated recoil mechanism to further reduce weight on the aircraft. PHASE I: The awardee shall demonstrate the feasibility of the ASP motion base assembly using modeling and simulation. Loads shall be based on an M3P machine gun as employed on an OH-58D helicopter. Critical technological factors such weight, pointing accuracy, control response, actuation power required, failure modes and effects, scalability, and manufacturability shall be assessed. PHASE II: The awardee shall design, build, and demonstrate the functionality and performance of the ASP motion base on a moving platform. Applied loads shall be based on an M3P machine gun as employed on an OH-58D helicopter. Closed-loop position control shall be demonstrated, but stabilization control need not be. Critical technical measures to be demonstrated include; pointing accuracy while under load of better than 0.1 milli-radians at frequencies higher than the gun firing rates (19 Hz), fail-safe failure modes, system weight less than 40 pounds (3x the current OH-58D mount, 15%-20% of ground vehicle turret (refs 7,8)), power required less than 30 amps at 28 volts DC. PHASE III: The awardee shall design, build, and demonstrate the functionality and performance of an inertially stabilized forward-firing gun mount using the ASP motion base technology. The stabilized mount shall replace the existing mount on an OH-6, UH-1, or OH-58 helicopter, and be flight tested under live fire conditions. Critical technical measures for the ASP-based system include; at least a 5:1 improvement in hits per round, cause no increase in takeoff weight while providing at least the same number of stowed kills, be capable of integrating with existing fire control systems. Phase III will result in a proven capability ready for adaptation to fielded military helicopters, boats, or ground vehicles, manned or unmanned. The proven ASP motion base technology may also benefit non-DoD applications by providing lightweight devices that can precisely point devices that impose large axial loads. Remote-control water cannons on top of Fire Department tower trucks, vectoring thrust rocket nozzles for satellite launchers, and mobile telescope / dish antenna tracking mounts are all viable candidates for this technology. It may also improve resistance to earthquakes for freestanding slender columns (towers) by providing active stabilization, similar in concept to that used by the Segway scooters.
