37 th Gun and Ammunition NDIA Symposium Multi-Role Armament & mmunition System (MRAAS) Weapon Stabilization Assessment

Transcription

1 Gregory S. Johnson Jerry C. Chang Jeffrey V. Ireland Rickie L. Stuva Thomas R. Williams 37 th Gun and Ammunition NDIA Symposium Multi-Role Armament & mmunition System (MRAAS) Weapon Stabilization Assessment United Defense L.P. Armament Systems Division Minneapolis, MN

2 + Contents Background Main Objectives Requirements Vehicle Dynamics Model Gun Pointing Control System Model Stochastic Pointing Error Estimation Platform Stability Analysis Gun Pointing Stiffness Study Conclusions

3 Background U.S. Army Transformation requires transition to highly transportable fighting force. The Future Combat System (FCS) is the intended objective - system of systems to meet a variety of missions. Multi-Role Armament & Ammunition System (MRAAS) under development by U.S. Army ARDEC to meet FCS LOS Direct Fire and BLOS/NLOS Indirect Fire lethality requirements. MRAAS MRAAS Study Study Concept Concept MRAAS Multi-Mission ATD features: Turret Mission Module for integration into light vehicle 105 mm cannon with swing chamber CTA munitions for direct/indirect fires LOS kills out to 4-5 km, BLOS kills out to 50+ km C-130 transportable, with 19 ton total system weight.

4 Main Objectives As part of 6 Month MRAAS Concepting Study Contract: Determine system dynamics impact of integrating a large caliber gun system onto a lightweight ground vehicle. Evaluate weapon stabilization performance of MRAAS, including sensitivity to: Gun unbalance due to CG offset from trunnion axis. Disturbances due to vehicle motion over terrain.

5 Requirements Per the MRAAS Turret Mission Module Weapon Control Request For Proposal: Fire Control System shall support LOS engagements under dynamic conditions with no greater than θ total mils error, 1 sigma Root Mean Square (RMS). Muzzle stabilization error shall be no more than θ stab mils RMS. Indirect fire requirements less stringent. Dynamic Condition Assumptions: Fire On The Move vehicle speed varied 5 to 30 mph. APG Munson Gravel Course and RRC-9 Stabilization Bump Course terrain models used to span roughness.

6 Vehicle Dynamics Model: Vehicle Concepting ey Assumptions: MRAAS turret concept mounted in mid and rear locations on wheeled chassis, with balanced/unbalanced armament (CG forward of trunnion) Appropriate mass property and space claim adjustments made: Concepts I & II Concepts III & IV Trunnion Brg Tipping Assy CG WEAPON COMPARTMENT CREW POWER PACK POWER PACK WEAPON COMPARTMENT CREW Unbalanced Gun Balanced Gun Concept Turret Location Gun Unbalance I Rear Unbalanced II Rear Balanced III Mid Unbalanced IV Mid Balanced Unbalance Most Signicant Effect For Stabilization

7 Vehicle Dynamics Model: DADS Development ey Vehicle Dynamics Assumptions: DADS rigid body chassis model. Simplified wheeled suspension model capturing hydropneumatic non-linear stiffness and damping characteristics Heave natural freq. ~ 1.5 Hz (translation) Pitch natural freq. ~ 0.75 Hz (rotation) Near critical damping Tire stiffness & damping. Traverse Brg Axis F s4 F s3 F s2 F s1 F n4 Trunnion Brg Axis F n3 W F n2 F n1 HSU Stiffnes Damping Tire Stiffness Vehicle Vehicle Dynamics Dynamics Free Free Body Body Diagram Diagram MRAAS DADS Wheeled Suspension Model Modified HSU Stiffness Characteristics 2000 MRAAS DADS Vehicle Suspension Model Modified HSU Damping Characteristics Spring Force [lb] Jounce Approx. Static Position Rebound Bump Stops Wheel Travel [in] Front Stations Rear Stations Damping Force [lb] 1500 Front Stations 1000 Rear Stations Rebound Jounce Wheel Travel Velocity [in/s]

8 Vehicle Dynamics Model: DADS Platform Disturbance Estimate Heave Acceleration Disturbance PSD [g 2 /Hz] Vehicle Pitch Rate Disturbance Power Spectral Density (PSD) MRAS Gun Pointing Disturbance: Concept I1 ATC RRC-9 Stabilization Bump Course, 9/01 Model Update 5 MPH Pitch Rate Disturbance PSD [mrad 2 /s 2 /Hz] MRAS Gun Pointing Disturbance: Concept I ATC RRC-9 Stabilization Bump Course, 9/01 Model Update 10 MPH MPH MPH Frequency [Hz] Vehicle Heave Acceleration Disturbance PSD 5 MPH 10 MPH 20 MPH 30 MPH

9 Gun Pointing Control System Model: MATRIXx Development Preliminary Elevation GPCS Model created in MATRIXx. Outer Gyro Rate P+I Loop (inertial) wrapped around Inner Motor Rate P+I loop (relative). MATRIXx model includes: Plant dynamics with variable drive compliance, gear reduction P+I compensation with notch filter Hull rate feed forward sensor with roll-off. MATRIXx MATRIXx Elevation Elevation GPCS GPCS Block Block Diagram Diagram

10 Gun Pointing Control System Model: GPCS Disturbance Rejection Estimate Dist Rejection W/Out Hull Rate Feed Fwd MATRIXx model used to estimate platform disturbance rejection transfer function. Gain [db] -30 Dist Rejection With Hull Rate Feed Fwd Frequency [Hz] Hull rate feed forward provides substantially greater rejection at low frequency. Gain [db] -80 q & ( w ) G( w ) = err q & dist ( w ) Frequency [Hz]

11 Stochastic Pointing Error Estimation 0 db ω bw G(ω) TERRAIN PROFILE Z( x) HICLE CHARACTERISTICS: EOMETRY ASS PROPERTIES USPENSION STIFFNESS USPENSION DAMPING VEHICLE DYNAMICS MODEL GPCS ELEV RATE LOOP BANDWIDTH w bw HEAVE DISTURBANCE & z T (t) PITCH DISTURBANCE GPCS ELEV. RATE LOOP DISTURBANCE REJECTION T.F. POWER SPECTRAL DENSITY q & ( w) G( w ) = err q & dist ( w ) ELEV. RATE DISTURBANCE PSD S (w) qdist & q & (t) v ESTIMATED GPCS REJECTION RESPONSE Pitch Rate Disturbance PSD [mrad 2 /s 2 /Hz] GPCS ELEVATION RESPONSE RMS MRAS Gun Pointing Disturbance: Concept I ATC RRC-9 Stabilization Bump Course, 9/01 Model Update ELEVATION 1s POINTING ACCURACY q RMS 5 MPH 10 MPH 20 MPH 30 MPH

12 Stochastic Error Estimation: Concept I Sensitivity to Terrain, Speed Predicted Elevation Pointing Accuracy [mrad, RMS] MRAAS Gun Pointing Control Bandwidth Analysis Concept I (Unbalanced Gun, Rear Turret) 5 MPH (Gravel Course) 5 MPH (Bump Course) 10 MPH (Gravel Course) 10 MPH (Bump Course) 20 MPH (Gravel Course) 20 MPH (Bump Course) 30 MPH (Gravel Course) 30 MPH (Bump Course) Elevation Rate Loop Bandwidth [Hz]

13 Stochastic Error Estimation: Concept II Sensitivity to Terrain, Speed MRAAS Gun Pointing Control Bandwidth Analysis Concept II (Balanced Gun, Rear Turret) Predicted Elevation Pointing Accuracy [mrad, RMS] MPH (Gravel Course) 5 MPH (Bump Course) MPH (Gravel Course) 10 MPH (Bump Course) MPH (Gravel Course) 20 MPH (Bump Course) MPH (Gravel Course) 30 MPH (Bump Course) Elevation Rate Loop Bandwidth [Hz]

14 Platform Stability Analysis Stochastic method appropriate for concept-level parametric trades. Allows rapid assessment of multiple simulation scenarios. Assumes load motion does not significantly influence base motion (gun and chassis are uncoupled). Next level of fidelity involves coupling MATRIXx pointing control model with DADS suspension model via DADS/Plant. Resulting Platform Stability model used to: Analytically verify stochastic method Estimate gun drive power requirements using Concepts I & II. Control Forces & Torques MRAAS MRAAS MATRIXx MATRIXx GPCS GPCS Model Model DADS/Plant MRAAS MRAAS Rigid Rigid Body Body DADS DADS Model Model Motion Feedback

15 Platform Stability Analysis: Stochastic Method Verification, Concept I Unbalanced Gun Predicted Elevation Pointing Accuracy [mrad RMS] Predicted Elevation Pointing Accuracy [mrad, RMS] MRAAS Gun Pointing Control Bandwidth Analysis 0.4 Concept II (Balanced Gun, Rear Turret) 0.3 METHOD STOCHASTIC Elevation Rate Loop Bandwidth [Hz] 5 MPH (Bump Course) 10 MPH (Bump Course) 20 MPH (Bump Course) 30 MPH (Bump Course) 30 MPH (Bump, MATRIXx) 0 20 MPH (Bump, MATRIXx) DADS/PLANT 1 10 MPH (Bump, MATRIXx) MPH (Bump. MATRIXx) Elevation Rate Loop Bandwidth [Hz] MRAAS Gun Pointing Control Bandwidth Analysis Concept I (Unbalanced Gun, Rear Turret) METHOD STOCHASTIC DADS/PLANT Elevation Rate Loop Bandwidth [Hz] 5 MPH (Bump Course) 10 MPH (Bump Course) 20 MPH (Bump Course) 30 MPH (Bump Course) 5 MPH (Bump. MATRIXx) 10 MPH (Bump, MATRIXx) 20 MPH (Bump, MATRIXx) 30 MPH (Bump, MATRIXx) Balanced Gun

16 Platform Stability Analysis: Elevation Drive Power Estimation 18.0 MRAAS Weapon Stabilization Power Estimation RRC-9 Bump Course, 10 Hz 1st Mode, 70% Assumed Overall Efficiency Total Motor Power Required [HP] Model I: Unbalanced Gun Model II: Balanced Gun PTotal Vehicle Speed [mph] High Slew Accel Slew Accel = 1.0 rad/s2 Med Slew Accel Slew Accel = 0.67 rad/s2 Low Slew Accel Slew Accel = 0.5 rad/s2 High Slew Accel Slew Accel = 1.0 rad/s2 Med Slew Accel Slew Accel = 0.67 rad/s2 Low Slew Accel Slew Accel = 0.5 rad/s2 ( T ) unbalance + Taccel + T w max = stab

17 Gun Pointing Stiffness Study Minimum 1 st natural frequency of the gun pointing system is constrained by the controller bandwidth. The gun pointing system natural frequency is determined by the flexibility of: Gun Drive Actuators, Turret, Gun Mount, Cannon A parametric study using a NASTRAN FEM was used to investigate first mode sensitivity to: Elevation Drive Stiffness Mount/Cannon Stiffness Mount Extension Length Mount Bearing Locations NASTRAN NASTRAN Armament Armament Finite Finite Element Element Model Model Gun Pointing First Mode MRAAS Gun Pointing Stiffness Sensitivity Effective First Mode vs Gun Drive Stiffness Gun Mount Configuration Short Long E E E E E E E Effective Drive Stiffness Effective Drive Stiffness (in-lb/rad, Actuator+Mount Lugs+Turret) Short With Tube Sprt.

18 Platform Stability Analysis Demo: DADS/Plant w/stabilized Flex Body MRAAS MRAAS MATRIXx MATRIXx GPCS GPCS Model Model DADS/Plant Flexible Body Demonstration Active Gun Pointing With Armament Structural Flexure Control Forces & Torques DADS/Plant Motion Feedback PG RRC-9 Stabilization Course NASTRAN NASTRAN Modal Modal Analysis Analysis MRAAS MRAAS DADS DADS Model Model with with Flexible Flexible Body Body Armament Armament DADS DADS Flexible Flexible Body Body Translator Translator

19 Platform Stability Analysis Demo: DADS/Plant - Stabilized Flexible Body

20 Conclusions Stochastic error estimation method provided rapid concept-level gun pointing performance estimation. Reducing gun CG offset from trunnion could reduce req mts for: Bandwidth & pointing stiffness by up to 25% Maximum drive power by up to 50% Trunnion vertical accelerometer (vertical acceleration feed forward). Parametric FEA modeling used for early estimation of optimal gun pointing component stiffnesses. Coupled modeling approach provided improved fidelity by leveraging subsystem models. Next step is to incorporate a Muzzle Reference Sensor with armament flexure response in the pointing control model. Using this approach, the disturbance rejection benefit of an active suspension system can also be evaluated.

21 Acknowledgements Study Co-Authors: Jerry Chang, DADS Vehicle Dynamics Rick Stuva, Gun Pointing Control Analysis Jeff Ireland, Tech Consulting/Pointing Stiffness Tom Williams, Parametric FEA This study was initiated and funded by the U.S. Army ARDEC under Contract DAAE30-00-C The authors would like to thank Steven McDonald, Roger Kent, Ramon Espinosa, and Thomas Louzeiro at Picatinny Arsenal; and Stephen Krupski at Benet Labs for their timely assistance, suggestions, and feedback.