Micro-Technology for Positioning, Navigation and Timing (µpnt) Dr. Program Manager DARPA/MTO
Aggregation Overall goal: Enable self-contained chip-scale inertial navigation Reduce SWaP of existing Inertial Measurement Units (IMU) What we have now: CSAC, IMPACT, NGIMG, PINS (DSO) - Components MINT, TUNS (DSO), SoOP (STO) System Integration Unaddressed need: Limited dynamic range Unacceptable long-term drift Size, Weight, Power and Cost (no path for chip-scale IMU) New approaches: Exploit inertia of elastic waves for increase in dynamic range Self-calibration on-a-chip for compensation of long-term bias drift Integration of time and inertial measurement units for cross-calibration and SWaP&C Why now? Recently emerged precision manufacturing of 3D structures Lab demonstration of bias stability improvement via mimicking inertial forces and persistent excitation Accumulated knowledge in heterogeneous integration and algorithms 2
Durations of DOD Missions Enable self-contained inertial navigation with micro systems Speed of Platform (km/hr) 10,000 1,000 100 10 1 M-16 Ballistic Grenade Launcher Over 70% of missile missions are less than 3 min Missile 1 SEALs Underwater Mission Soldier Walking in Cave Missile 2 Missile 3 Precision Engagement with GPS-assisted guidance Missile 4 Soldier Walking in Open Field Missile 5 Micro UAV Missile 6 Missile 8 Missile 7 1 10 100 1,000 Range of Mission (km) HMMWV Missile 9 Missile 10 Personal navigation GPS-assisted 24 hr Missile 11 Currently Funded New Starts 3
µpnt Technology Drivers Technical Focus Area Components Gyros, clocks, accels, velocity sensors Driving Operation Characteristics System Calibration ZUPting, persistent excitation with micro stages, algorithms Device Integration Fabrication approaches, architectures Guidance High Dynamic Range 1 1 MRIG: Micro Rate Integrating Gyroscopes Navigation Low Power Consumption NGIMG: Navigation Grade Integrated Micro Gyroscopes CSAC: Chip Scale Atomic Clock IMPACT: Integrated Micro Primary Atomic Clock Technology MINT: Micro Inertial Navigation Technology PASCAL: Primary and Secondary Calibration on Active Layer IT-MARS: Information Tethered Micro Automated Rotary Stages TIMU: Deep Integration of Time and Inertial Measurement Unit - New Starts 4
Precision Engagement ACTIVE GUIDANCE DEFINE ORIENTATION DEFINE TARGET Today: large & expensive sensors on static platforms Vision: small SWaP sensors extended to mobile platforms Today: GPS-assisted Vision: self-contained guidance (no GPS) in fast precision engagement Today: GPS, magnetic compass, and range finder Vision: eliminate magnetic compass with ultra-small gyro compassing solutions 5
µpnt Challenges Sensors for dynamic environment Frequency miss-match grows proportionally to input rotation rate. Linearity of response is affected by rotation rate Challenging dynamic environment, bias drift, ultra miniaturization on system-level Long-term bias drift Increased surface- tovolume ratio makes micro devices sensitive to surface effects: charging, contamination, outgassing, trapping This results in long-term fluctuation of physical parameters, reflected in longterm sensor drift Deep integration of clocks & IMU 2 mm SoA clocks and sensors are incompatible, and implemented separately Multiple non-synchronized frequency sources are used in Navigation system routinely (power consumption, grows in uncertainty of time-position-orientation) Fabrication processes Dissimilar and incompatible with wafer-level parallel fabrication SWaP & C Can build small, but cannot build precise (~10-2 relative tolerance) performance SoA micro-structures are fundamentally flat, non-ideal for high-g environment and fast-agile sensor concepts 6
µpnt Technical Approaches Inertia of elastic waves, self-calibration/cross-calibration algorithms, 3D fabrication Sensors for dynamic environment Utilize inertia of elastic waves. Precession of standing waves preserves linearity and extends the dynamic range. Explore new materials with large Young Modulus Deep integration of clocks & IMU 2 mm Develop clocks and sensors around a compatible combination of materials (Si, SiO 2, Rb, Cs) Use a single master clock for time, sync, and signal processing Long-term bias drift Compensate by applying persistent excitation via calibration stage integrated along side with sensors Fabrication processes Utilize under-explored process: post-release assembly, chip-level welding, stacking Explore precision fabrication based on surface tension (~10-6 projected tolerance) 3D processes: blow, stretch, stamp, roll 7
New Approach for Solving Dynamic Range Limitations Hemispherical Resonance Gyro (HRG) Highly successful Boutique process Northrop Grumman HRG Bias Stability : 0.01 [ deg hour] Size : 50 [ cm ] φ = Ωdt Angle Random Walk (ARW) : 0.0006 [deg Power : 4 [ Watts] 3 hour ] Rate Response HRG on micro scale Exploits inertial properties of elastic waves in solids Relies on wafer-scale fabrication of isotropic 3D solids Results in unprecedented increase in dynamic range New approach Rate Integrating Gyroscope 3% 20 Hz 40 Hz Input Angular Rate Classical Rate Gyroscope Classical Rate Gyroscope ωn 2 && x + x& + ωn x = 2Ωy& Q ωn 2 && y + y& + ωn y = 2Ωx& Q ω n - drive/sense natural frequency Ω - measured rotation rate Q - resonator quality factor Δ - frequency separation New Approach Rate Integrating Gyroscope Axis of Rotation Elastic wave Price Range per axis: $50,000-$100,000 8
Self-Calibration On-a-Chip Bias Drift (illustration) Motivation Output (Voltage) Ideal response Drifted response Input (Rotation) Current options when sensor drifts: Use inaccurate data Remove sensor from system re-calibrate in lab & re-insert in system discard & replace Approach Gyroscope Calibration Stage Why Now?: Previously, technology pushed towards the perfect sensor community now realizes the challenges of this approach Phenomenon of drift not well understood Re-calibration circumvents knowledge about the cause of drift New emerging technological advances permit the miniaturization of rate tables for on-chip calibration New Approach: 1. Fabricate sensor directly on calibration stage 2. Periodically apply reference stimulus (e.g. oscillatory) 3. Extract reference stimulus and sensor response 4. Recover new I/O relationship and reset bias 1. Co-fabricate 2. Excite 3. Extract 4. Reset sensor reference 9
The program addresses the emerging DOD need to Decrease reliance on GPS Increase system accuracy Reduce co-lateral damage Increase effective range Reduce SWAP&C µpnt Objective HG9900 Nav grade IMU HG1930 MEMS IMU This program Parameters Units SOA SOA MEMS µpnt Size mm 3 1.6*10 7 6.5*10 4 8 Weight gm 4.5*10 3 2*10 2 ~2 Power W 25 5 ~1 Gyro Range deg/sec (Hz) 1,000 (3) 3,600 (10) 15,000 (40) Gyro Bias deg/hr 0.02 4 0.05 Gyro ARW deg/ hr 0.01 0.12 0.01 Gyro Drift ppm, 3σ 1 400 1 Accel. Range g 25 70 1,000 Accel. Bias mg 0.1 4 0.1 Misalignment µ-radians, 3σ 200 1,000 100 10
µpnt Organization Components Nav-Grade Integrated Micro Gyro (NGIMG) FY10 FY11 FY12 FY13 FY14 Micro Rate Integrating Gyroscopes (MRIG) BAA Demo 3D isotropic manufacturing Demo Rate Integrating Gyro SWaP and Performance demonstrated Device Integration Chip-Scale Atomic Clock (CSAC) Timing and IMU Integration (TIMU) Integrated Micro Primary Atomic Clock Technology (IMPACT) System Calibration BAA Demo functional T+IMU unit Demo tactical grade performance Demo Nav. grade performance Micro Inertial Navigation Technology (MINT) Prim. and Sec. Calibration on Active Layer (PASCAL) Information Tethered Micro Automated Rotary Stages (ITMARS) BAA Demo Sensors on Calibration Stages Demo Improvement in drift characteristics Completely Integrated System =BAA =End of Phase 11