A Systems Engineering Approach For Balancing Powered Trailer
A Systems Engineering Approach For Balancing Powered Trailer Requirements Dana Peterson (CSEP Acq) [email protected] (314) 553-4599 Purpose of Presentation Illustrate a sample of Systems Engineering tools used on the Powered Trailer project to: Resolve requirement issues Understand relationships between requirements Prioritize requirements Get consensus on the best technology options Provide the best balanced overall solution INCOSE BRIEF @ DRS Technologies 2 Powered Trailer Project Goals Powered Trailer Improve combined truck and trailer grade climbing and mobility in soft soil terrain conditions Provide cargo and health status reporting over the C4I network Provide limited trailer self-mobility for climbing aircraft/ship ramps under operator control Provide on-board DC/AC export power for powering shelters and other equipment Focus is on Trailer Drive Technologies INCOSE BRIEF @ DRS Technologies 3 Sample SE Tools Requirements Traceability/ Rationale Matrix (RTRM) N2 Diagram Analytic Hierarchy Process (AHP) Quality Function Deployment (QFD) Morphological Analysis (MA) Architecture Views Trade Study Sensitivity Analysis Affinity Diagram Tree Diagram Fishbone Diagram Digraph Blueprinting Arrow Diagram Matrix Diagram Relations Diagram
Process Decision Program Chart Flow Diagram Context Diagram Pugh Matrix Specification INCOSE BRIEF @ DRS Technologies 4 Systems Engineering Approach User Requirements Performance Spec Requirements Traceability/ Rationale Matrix (RTRM) Mobility Analysis Legend AHP = Analytical Hierarchy Process QFD = Quality Function Deployment MA = Morphological Analysis AHP Requirement Prioritization QFD House Of Quality Power Trailer Design Alternatives MA Technology Options Trade Studies -Performance -Payload -C-130 Transport -R&M -Cost -Schedule Sensitivity Analysis Preferred Solution An Iterative Hierarchical Process That Provides the Best Overall Requirements Balance Multi-Attribute Criteria Problem le du he Sc Co st Many requirements in diverse functional areas A lot of stakeholders involved Tools are needed to balance requirements and validate concept prior to project execution Cost and schedule are receiving a lot more attention
Performance INCOSE BRIEF @ DRS Technologies 6 Solution Synthesis is Becoming More Challenging Part Obsolescence Technology Advances Cultural Reorganization Robust Design Designfor forAdaptability Adaptability Design Techniques Political Modular Systems Approach Rapid Response Open Architecture le du he Sc Six Sigma Co st Spiral Development Performance Security Agile Design Design To Cost People Resources Design for Dynamic Value Company Mergers Economic Eco-Consciousness INCOSE BRIEF @ DRS Technologies 7 Customers Now: Prioritizing Requirements: Spiral 1, 2, 3 Evolution Threshold Vs Objective Key Performance Parameters Vs Key System Attributes Vs Additional Attributes Tier Levels 1, 2, 3, 4 Asking: What Is Possible? What Can Be Done Within Program Constraints and Current Technology?
What Are The Tradeoffs? Provide Me With The Best Balanced Solution! INCOSE BRIEF @ DRS Technologies 8 RTRM Sample Sheet (Transport & Trailer Requirements) POWERED TRAILER REQUIREMENTS TRACEABILITY/RATIONALE MATRIX (RTRM) Source 78 Derived from The MSV at GCW must negotiate the 30% side slope. The ORD lines companion trailer is assumed coupled to the truck. This 300 - 304 requirement must be met with either side of the vehicle facing uphill. At what speed does this need to be meet? Definitely need to check stability x Derived from The Mobility Rating Speed (MSR) and the Percent Go/No Go in ORD lines soft soil for the MSV must be equal to or greater than the FCS 308 - 309 vehicle. Therefore, the trailer should provide equal performance. We need to determine what the FCS requirement is. x 79 80 81 30% Side Slope Soft Soil Mobility equal to or greater than FCS Central Tire Inflation ORD lines System (CTIS) 329 - 337 FTTS will have variable height Program charts Comments/Requirements Rationale Spiral Spiral Spiral 3 Draft Trailer Requirement based on FTTS ORD unless specified 1 2 Prod otherwise Item Reqmt/Short Description The requirement is to be able to adjust the MSV/trailer tire pressures to improve cross country mobility. The range of parameters that must be considered are GVW to GCW, axle locations, and terrain conditions. 109.62 inches raised (24 inch ground clearance) and 94.62 inches squatted (9 inch ground clearance). FTTS is 374.5 inches long and has a 96 inch width, with a 77 inch track? Note that these dimensions are subject to change. x x The FTTS-MSV from CW to GCW shall be capable of traversing a dry hard surface side slope up to and including 30 percent. Side slope operation shall be performed with either side of the vehicle facing up slope and without loss of stability or malfunction Soft Soil Traversing Characteristics. The FTTS-MSV (with companion trailer) shall have equal or better Mobility Rating Speed (MRS) and percent GO/NO-GO than the
FCS. The FTTS MSV and its companion trailer shall incorporate means to adjust tire pressure to increase cross country mobility. The FTTS-MSV shall incorporate this capability to allow the operator to adjust tire pressure. Dimensions do not apply to the companion trailer, these are dimensions and requirements for the FTTS prime mover. Variable height may however be required for the trailer to meet transport requirements. Statistics: RTRM - Number of Requirement Paragraphs: 135 - Number of Stated Requirements: 250 - Requirements Needing Clarification: 20 (8%) - Number of Requirement Disconnects: 12 (5%)Issues Helps To Identify & Resolve Requirement INCOSE BRIEF @ DRS Technologies Total Requirement Issues: 32 (13%) 9 System N2 Diagram The N2 diagram illustrates interfaces and relationships between system requirements, parameters, and metrics System functions or elements are listed in the diagonal boxes Interfaces and relationships are identified in the off-diagonal boxes. Data flows in a clockwise direction between functions or elements The next example illustrates a modified form of N2 where requirements have been listed in the diagonal boxes Helps To Surface Interface Issues N2 Helps To Identify Interface Issues INCOSE BRIEF @ DRS Technologies 10 Example N2 Diagram Mobility Payload Protection Transportability C4ISR/EW Elec Power Supportability GVW Curb Weight Height Mobility %NO-GO <25 45-50 mph on 5% Grade Payload:
GVWCWCrew 24 Ground Clearance Desired Turning Radius of 25 SA (FBCB2, MTS) Engine Gen/ Alternator Fuel Specifics Diesel 80 gm/kWh JP8 88 gm/kWh Pwr to Weight Ratio > 30 bhp/ton See GVW t/2h 1.20 for Stability Payload Suspension Max Payload at 5100 lbs Weight Trades Essential Combat Configuration (ECC) C2 Equip Med Equip Weight Trades Sustainment Supplies for 3 Days Weight Trades Payload to Curb Weight Ratio 0.5 H=76 for MPF 102 C-130 Protection Protection for Crew Vs. Weight KE, MINE, IED, Overhead Ease of B-Kit Armor R/R Threat Types & Locations
Active Armor Protection Armor Repair Costs Weight Trades Integral Armor GPK, CROWS, Weapons (2) C-130, CH-47, CH-53, MPF Operator Remote Control Climbing Ramps Trailers 18,000 lbs (2) On C-130 12,000 lbs Desired H=76 for MPF 102 C-130 Net-ready, C2, FBCB2, MTS Silent Watch (2 Hours) RFID C2 Equip Weight C2 Equipmen t Weight Antennas 15 kW OB 10 kW Exp Exp Power Weight Trades A-Kit Vs B-Kit Not Specified GVW: CW + Payload + Crew Height Impacts Weight Not Specified Height
Impacts Weight Transportability C4ISR/EW Obstacle Avoidance Elec Power Hybrid Drive Option Supportability Fuel Efficiency 60 ton-mpg 400 mile range GVW Acceleration Curb Weight Height Stowage Items BII 13,000 lbs Max. Axel Loading Weight Trades Suspension Health Mgt. CBM+ Weight Trades 13,000 lbs Max. Axel Loading A0=95% MMBF=10,000 for Production < 157.5 for Berne Tunnel Analytical Hierarchy Process (AHP) Proven, effective means to deal with complex decision making involving multiple criteria Captures both subjective and objective evaluation measures A hierarchal decomposition of requirements or goals is accomplished Pair wise comparisons of requirement attributes are made and relative scores computed for each leaf of the hierarchy Scores are then synthesized yielding the relative weights at each leaf as well as for the overall model A coherent assessment is reached when Inconsistency Ratio < 0.1 (http://people.revoledu.com/kardi/tutorial/AHP/Consistency.htm) AHP Helps to Determine Relative Importance INCOSE BRIEF @ DRS Technologies 12
Requirements Model Breakdown Model Level 1 Model Level 2 Model Level 3 Mobility GVW Driver Vision Stability Speed HP/ton Operational Range Fuel efficiency (ton-mpg) Fuel Capacity Armor Protection Transportability CW Height 76in Axle Loading 30 min Ready Survivability CREW2.1 SD Weapon CBRNE Signature Mgt Ballistics Protection LVOSS Visual signature Thermal signature EM signature Direct Fire IED Mine Anti-tank Blast Protection Seats Crush resistant roof
Model Level 4 Power Management C4IRS/EW C3 SA Net Security Bus Architect Power Buses OB Power Export Power Electrical Storage Supportability RAM Health Mgt HFE O&S Cost Commonality Payload Flatrack (3,200 lb) Cargo (22,000 lb) Fuel Specifics ECU Map Legend: GWV =Gross Vehicle Weight, CW = Curb Weight, C3 = Command, Control, Communications, SD = Self-Defense, SA = Situational Awareness, OB = OnBoard, DVE = Driver Vision Enhancer, CBRNE = Chemical, Biological, Radiological, Nuclear Effects, IED =Improvised Explosive Device, LVOSS = Light Vehicle Obscuration Smoke System, LCC = Life Cycle Cost, UPC = Unit Production Cost INCOSE BRIEF @ DRS Technologies 13 Analytical Hierarchy Process Snapshot Combinatorial Trade Study- Requirements Importance Level 1 Requirements Per Customer Attribute Weights (weights can be modified for tradeoff purposes) Mobility 0.14 Payload 0.20 Transportability
0.20 Survivability 0.10 C4ISR/EW 0.13 Power Mgt 0.07 Supportability 0.16 Total 1.00 Notes: If Row and Column are of equal importance then 1; minimize use of 1 If Row more important than Column then 2 If Column more important than Row then 0 Only need to assess White pairs; Gray pairs are diagonal or self-calculated Level 2 Requirements- Mobility GVW Driver Vision Roll Stability Top Speed Hp/ton Operating Range GVW 1 0 0 2 0 0 Drive Vision 2 1 1 2 1 2 Roll Stability 2 1 1 2 2 2 Top Speed 0 0 0 1 0 0 Hp/ton 2 1 0 2 1 1 Operating Range 2 0 0 2 1 1 Level 3 Requirements- Operating Range Fuel Efficiency Fuel Capacity Fuel Efficiency 1 0 Fuel Capacity 2 1 Armor Protection 0 0 Totals Weighting 3
There are stated and unstated requirements QFD helps to prioritize requirements and their tradeoffs QFD makes invisible requirements and strategic advantages visible QFD helps to define which improvements provide the most gain QFD promotes Team Consensus QFD provides a documented audit trail for decisions The House of Quality Captures the Voice of the Customer INCOSE BRIEF @ DRS Technologies 15 House of Quality Requirements/Desires (Voice of the Customer) Interrelationships between Technologies Technologies (Voice of the Company) Planning Matrix -Requirements Importance -Percent Improvement Desired -Marketing Competition Assessment Relationships between Requirements and Technologies Prioritized Technologies INCOSE BRIEF @ DRS Technologies 16 Powered Trailer QFD Analysis Two meetings were conducted with shareholders to get consensus on the Powered Trailer House of Quality Body of Matrix Common definition/scope for each requirement and technical attribute agreed to Reinforced relationship values - by convention: (0-none, 1-weak, 3-moderate, 9-strong) Recognized the most important associations Segregated positive and negative correlations, ensured they were mutually exclusive Achieved Consensus, Consensus, Consensus QFD was finalized via (2) additional WebEx conferences INCOSE BRIEF @ DRS Technologies 17 Powered Trailer House of Quality + - 3 9 9 9 3 1 3 3 9 3 3 3 3
Powered Trailer House of Quality Trailer QFD INCOSE BRIEF @ DRS Technologies 19 QFD Relative Ranking 100 90 80 70 60 50 40 30 20 10 0 QFD Relative Ranking Suspension ICE Hybrid Braking Pwr Storage Steering Towed LHS Serial Bus Auto ID Adj. Deck 3 Axles Umbilical MIP Elect PTO Smart Tie Mech PTO Signature Mgt Wireless (Excludes Technical Difficulty and Cost Factors) INCOSE BRIEF @ DRS Technologies 20 Arrows Impossibility Theorem (A Word of Caution!) Combining individual preferences to form a group utility function presents a problem The use of averaged group preference data in product design optimization can lead to erroneous results This problem may not always be selfevident in the analysis of complex systems and products Group Consensus Must Be Reached To Avoid This Problem Provides a Hierarchical Model For Doing Tradeoffs INCOSE BRIEF @ DRS Technologies 21 Morphological Analysis Designed for multi-dimensional, nonquantifiable problem complexes Explores boundary conditions Investigates the total set of possible relationships and configuration alternatives Rules out alternatives that are inconsistent or incompatible using cross-consistency assessment MA Ensures No Alternative is Overlooked INCOSE BRIEF @ DRS Technologies 22 Morphological Field Example: 3-Parameters: color, texture, size Color: 5 discrete values: red, green, blue, yellow, brown Texture: 5 discrete values: smooth, serrated, rough, grainy,
bumpy Size: 3 discrete values: large, medium, small 75 cells or configurations (Zwicky, 1969, p. 118.) INCOSE BRIEF @ DRS Technologies 23 MA-Trailer Drive Alternatives Vehicle Output Energy Form Trailer Drive Type Mechanical Mechanical Electrical Electrical Hydraulic Hydraulic None Internal Combustion Engine (ICE) Hybrid Electric Hybrid Hydraulic Number of Configurations or Alternatives 4 X 6 = 24 Ruled out Combinations of Output Energy and Hybrid 3 X 2 = 06 18 Alternatives to Investigate No . Vehicle Output Energy Form Trailer Drive Consistency? YES/NO 1 Mechanical Mechanical YES 2 Mechanical Electrical NO 3 Mechanical Hydraulic NO 4 Mechanical
ICE NO 5 Electrical Mechanical NO 6 Electrical Electrical YES 7 Electrical Hydraulic NO 8 Electrical ICE NO 9 Hydraulic Mechanical NO 10 Hydraulic Electrical NO 11 Hydraulic Hydraulic NO 12 Hydraulic ICE NO 13 None Mechanical NO 14 None Electrical
NO 15 None Hydraulic NO 16 None ICE YES 17 None Hybrid Electric YES 18 None Hybrid Hydraulic YES (5) Drive Alternatives Remain in Trade Space INCOSE BRIEF @ DRS Technologies 24 Powered Trailer Design Concepts ALT #1 Electric PTO -Electrical Power Take Off provided by the transport ALT #2 HEV -Series Hybrid Electric Vehicle with ICE, generator, and battery pack ALT #3 HHV -Hybrid Hydraulic Vehicle with hydraulic power provided by an ICE driven power pack ALT #4 Mechanical PTO -Mechanical Power Take Off provided by the transport ALT #5 ICE Drive -ICE (210 HP with 340 ft-lb torque) with conventional drive train ICE = Internal Combustion Engine INCOSE BRIEF @ DRS Technologies 25 Features Common To All Concepts 395/85 R20 XZL tires Central Tire Inflation System (CTIS) Pneumatic Anti-Lock Brake System (ABS) Serial communications with transport Control of mobility assist and CTIS Receipt of trailer health and cargo load status Independent Suspension Trailer bed basic design INCOSE BRIEF @ DRS Technologies 26 Concepts ALT #1 Elect PTO ALT #2 HEV Trailer Trailer
200 Kw 300 vdc mechanical Transport Control box/Inverter Display motor System Controller DC-AC Inverter 12/24 vdc for electronics, trailer lights, etc. pump radiator ALT #4 Mech PTO Low pressure reservoir System Controller 12/24 vdc for electronics, trailer lights,etc. Transport ABS mechanical PTO Display System Controller Display 12/24 vdc for electronics, trailer lights,etc. Note: Brake and CTIS lines to wheels not shown for clarity Note: Brake and CTIS lines to wheels not shown for clarity Trailer Generator ICE CVT serial ABS mechanical Fuel Tank Display Display System Controller 12/24 vdc for electronics, trailer lights,etc. serial ABS hydraulic
Operator Remote Control Unit pneumatic Transport discrete ICE High pressure accumulator ALT #5 ICE Drive discrete Trailer pneumatic Pump/ motor Display Display Export Power Note: Brake and CTIS lines not shown for clarity Trailer mechanical radiator Operator Remote Control Unit ALT #3 HHV Transport ABS Control box/Inverter Display 12/24 vdc for electronics, trailer lights, etc. Note: Brake and CTIS lines not shown for clarity discrete motor pump Export Power serial Control box/Inverter motor System Controller DC-AC Inverter Operator Remote Control Unit pneumatic Battery Pack 36 kW-hr ICE Generator (25) 120 amp-hr batteries Air tanks ABS
fuel tank Control box/Inverter serial CTIS Transport discrete motor CTIS mechanical Battery Pack 36 kW-hr (25) 120 amp-hr batteries Air tanks serial Steering actuator discrete Steering actuator pneumatic pneumatic Architectural Views for all Five Alternatives DC-AC Inverter Operator Remote Control Unit Export Power Note: Brake and CTIS lines to wheels not shown for clarity INCOSE BRIEF @ DRS Technologies 27 Physical Characteristics Wheel Drive Suspension ALT#1 Electric PTO ALT#2 HEV ALT#3 HHV ALT#4 Mech PTO ALT#5 ICE drive 4x2 4x4 4x2 4x2 4x4
Trailing Arm Either Type Either Type Double A-Arm Double A-Arm Length (in) Width (in) Deck Height (in) Ground Clearance (in) Track (in) 280 96 51.5 328 96 51.5 285 96 51.5 280 96 51.5 328 96 51.5 18 81 18 81 18 79 18 81 18 81 Wheel Base (in) Basic Bed (lbs) 192 5,745 192 5,745 201 5,745 192 5,745 192 5,745 Suspension & Power Drive (lbs) Flat rack (lbs) 6,625 9,800 5,155 4,875 7,570 3,200
3,200 3,200 3,200 3,200 Cargo Load (lbs) 22,000 22,000 22,000 22,000 22,000 Total Weigh-lbs 37,570 18.8 ST 40,395 20.2 ST 36,100 18.1 ST 35,820 18 ST 38,515 19.3 ST ST = Short Ton or 2,000 lbs INCOSE BRIEF @ DRS Technologies 28 ALT #1 Elect PTO Components Detail Needed for Credible Cost & Schedule Estimates INCOSE BRIEF @ DRS Technologies 29 Cost Vs Key Requirements Met Cost Vs Key Requirements Met Cost per 1000 Units $150K $140K $70K $55K $40K $35K 0 10 20 30 40 50 60
70 80 90 100 Percent of Key Requirements Met INCOSE BRIEF @ DRS Technologies 30 Comparison of Alternatives Trade Parameters Requiremen t Weightings Alt #1 Elect PTO Alt #2 HEV Alt #3 HHV Alt #4 Mech PTO Alt #5 ICE Drive Mobility Assist 5|5 3 5 4 3 5 Self Mobility 3|3 0 5 4 0 4 Payload 4|4 5 4 4 5 4 Complexity
Normalized Score 1.36 |1.39 1.46 |1.41 1|1 1.28 |1.42 1.54 |1.58 Weighting/Scoring 0-5 with 5 Best INCOSE BRIEF @ DRS Technologies 31 SE Tool Usage Summary Understanding requirements; their relationships, and relative importance: Tools: RTRM, N2 Diagram, AHP Getting consensus on the best technology options for meeting customer needs: Tools: QFD (House of Quality) Evaluating alternatives: Tools: AHP, MA, Architectural Views Selecting the best alternative: Tools: Trade Study, Sensitivity Analysis INCOSE BRIEF @ DRS Technologies 32 Conclusions SE Process Critical for Providing Best Balanced Solution SE Tools Assist in: Understanding requirements and their relationships Getting consensus on which technology options provide the greatest benefits Assuring no viable alternative is overlooked Performing meaningful tradeoffs and sensitivity analysis Making decisions involving multiple attribute criteria Go to: www.incose.org for more information Capturing the Results in the Requirements Set Reduces Program Execution Risks INCOSE BRIEF @ DRS Technologies 33 Questions ? INCOSE BRIEF @ DRS Technologies 34
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