Skid Steer Fuel Cell Powered Unmanned Ground Vehicle (Burro)

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Skid Steer Fuel Cell Powered Unmanned Ground Vehicle (Burro) Powered By Docstoc
					Skid Steer Fuel Cell Powered
 Unmanned Ground Vehicle
 Jay Meldrum, Christopher Green
Goals of the Research
Little Brother
Big Brother
     Goals of the Research
Alternative energy for military applications
can provide an engine-off capability
Propulsion for support and deployment
Pl P         for field
Plug Power f fi ld
communications/sentry duty
Mobility platform for DE and NBC
            Two Vehicles
Little Brother
  1000 lb, powered solely on alternative energy
  Serves as a technology building block
Big Brother
  5000 lb, hybrid with conventional diesel and
  alternative energy source
 Little Brother Target Specifications
                      Item                     Target
                      Max GVW                  900 lb
Basis:                Vehicle Weight (wet)     500 lb
Utility / Logistics   Payload                  400 lb
and Equipment         H i h / Width / L h
                      Height Wid h Length      42” x 48” x 84”
                                               42” 48” 84”
(MULE)                Ground Pressure          <1.0 psi
                      Max Speed                    p
                                               25 mph
                      Range                    50 miles
                      Quiet Mode Operation     1hr
                      Maximum Slope Climbing   40%
                      Side Slope               40%
                        p        g
                      Gap Crossing             42”
                      Draw Bar Pull            50%
                                               50% GVW
                      Vertical Step            12”
       Little Brother Modified Target
                      Item                      Target
                      Max GVW                   900 lb
Multifunction         Vehicle Weight (wet)      500 lb
Utility / Logistics   Payload                   400 lb
and Equipment         Height / Width / Length   42” 48” 84”
                                                42” x 48” x 84”
                      Ground Pressure           <1.0 psi
                      Max Speed                 25 mph
                      Range                     50 miles
                      Quiet Mode Operation      1hr
                      Maximum Slope Climbing    40%
                      Side Slope                40%
                      Gap Crossing              42”
                      Draw Bar Pull             50%
                                                50% GVW
                      Vertical Step             12”
Modified Little Brother Targets

     Item                     Target
     Max Speed                4 mph
     Range                    4 miles
     Quiet Mode Operation     ~ 20 minutes
     Maximum Slope Climbing   30%
     Side Slope               30%
Vehicle Dynamics Calculations
Basic analysis to estimate necessary
vehicle power d
  hi l        density
                    it      P    μ + sin α
                               =           gV
                            Mv      η
                                     P = Vehicle Power
                                     Mv = Vehicle Mass
                                     μ = Rolling Resistance
                           V         α = Slope
                                     g = Gravitational Acceleration
                                     V = Velocity
                                     η = Mechanical Efficiency
        α      F Motion Resistance
                                           i       i     d
                                     “Terrain Severity Index” =
                                     μ + sin α
                                                Vehicle Dynamics Graph
                                           Vehicle Power Density vs Speed and Terrain Severity

         ower Density (W

                                1                                                                0.15    μ+ sin α
Vehicle Po

                                                                                                 0.8     Scenarios to Achieve
                                                                                                         Target Speed:
                                                                                                         - Flat road w/ soft soil
                               0.1                                                                        Smooth
                                                                                                         -Smooth surface w/
                                     0.1                          1                       10             17.5 degree
                                                          Vehicle Speed (mph)

                                                       Typical μ values:               0.15 = Tracked vehicle
                                                       0.025 = Hallway                 0.3 = Easy Off-Road
                                                       0.06 = Low psi tires            0.8 = Complex Terrain
     Vehicle Dynamics Power
          R    i
Scenarios to achieve target speed of 4 mph:
  Flat road (α = 0) with soft soil (μ = 0.3)
  Smooth surface (μ = 0) with angle α = 17.5 degrees
                          )         g          g
Necessary vehicle power density = 5.9 W/kg
Assume vehicle mass Mv is broken down into
payload (50%), chassis (35%), and power
source (15%)
Resulting alternative energy power density
requirement is 39 W/kg.
          Alternative Energy
      Power Source Selection f LB
      P     S       S l i for
                     Technology                     Power to
                     Lithium-Ion Battery            200 W/kg
                      i k l     l d id
                     Nickel Metal Hydride                 /k
                                                    200 W/kg
                     Sodium/Nickel Chloride Battery 150 W/kg
                     Hydrogenics 12KW Fuel Cell     132 W/kg
                     Nuvera 5KW Fuel Cell           52.7 W/kg
Alternative energy  Minimum targetg                      g
                                                   39 W/kg
power source        Stirling Engine                27.2 W/kg
chosen in agreement
between MTU/ARL     Solid Oxide Fuel Cell          14.4 W/kg
                    Direct Methanol Fuel Cell      6.2 W/kg
Little Brother Assembly and Testing
 Stripped down existing battery-powered
Little Brother Assembly and Testing
 Modify bulkhead for
 placement of 5 kW Nuvera
 fuel cell
 Add two aluminum hydrogen
 storage tanks
 Install track system
 Addition of new electric
  Little Brother Components
DC-                          37.5
DC-DC converter to provide 37 5 VDC to
motor controller
Operation via radio remote control unit
Absorbed glass mat batteries provide
 t t           f f l ll
startup power for fuel cell
2.5 kW inverter provides “plug power” for
directed energy / payload devices
Little Brother Model and
        R li i
Little Brother Results
  I                             Target
  Width                         52”
                                52” (132 cm)
  Length                        89”        )
                                89” (226 cm)
  Height                        46”
                                46” (117 cm)
  Weight                        1,063 lb
  Ground Pressure               0.67 psi
  Vehicle Power Density         10.
                                10.4 W/kg
  Co c e e o g es s a ce
  Concrete Rolling Resistance   0.124
  Drawbar pull (concrete)       70%
                                70% of GVW
  Speed                         2.5 mph
  Radio Control Range           150 ft
Little Brother Results
 Item                             Target
 Fuel capacity per cylinder at    34 min
 maximum power
 Fuel capacity per cylinder (idle) 5.1 h
 Slope capability (dirt)          52%
                                  52% up / down
 Turning radius                   0 = pivot turn
 Mobility, speed control          Inching (very
                                   slow speed)
        y,     p
 Mobility, swamp                   p
                                  Up to 8” water
 Mobility, brush                  Climbed
                                  through 1”
                                  diameter brush
Extreme   Mobility
  Big Brother - 5000 pounds
Multiple vehicle architectures considered
  Electric drive
  Electro-hydraulic drive
  Dual power: mechanical or electric drive
  Parallel electric hybrid
  Series electric hybrid
   Big Brother Platform Selection

Bobcat skid steer / four wheel drive
- 81 hp (60 kw) diesel engine, two speed ranges, ability to
  switch between skid steer and all wheel steer modes
- Belt drive allows for addition of clutches to selectively drive
  hydraulic pumps with electric motor / diesel engine
Big Brother: Hydraulic Pumps / Motors

               Pump 1
              Hydraulic   Electric    Motor
               Pump 2      Motor     Controller    DC-DC      Fuel Cell
                Hyd.                              Converter
              Pump 3
     Engine                           B tt
              Pump 4
              Pump 5

              commercially available in Bobcat skid steer / four wheel drive
          Alternative Energy
      Power Source Selection f BB
      P     S      S l i for
                     Technology                     Power to
                     Lithium-Ion Battery            200 W/kg
                      i k l     l d id
                     Nickel Metal Hydride                 /k
                                                    200 W/kg
                     Sodium/Nickel Chloride Battery 150 W/kg
                     Hydrogenics 12KW Fuel Cell     132 W/kg
                     Nuvera 5KW Fuel Cell           52.7 W/kg
Alternative energy  Minimum targetg                      g
                                                   39 W/kg
power source        Stirling Engine                27.2 W/kg
chosen in agreement
between MTU/ARL     Solid Oxide Fuel Cell          14.4 W/kg
                    Direct Methanol Fuel Cell      6.2 W/kg
Hydrogenics Fuel Cell Performance

                                                          FUEL CELL PERFORMANCE

                                    58                                                        14

                                    54                                                        12

                                    50                                                        10                         Voltage Spec
            Fuel Cell Voltage [V

                                                                                                   Fu Cell Power [kVA]
                                                                                                                         Run 1 Volts
                                    46                                                        8
                                                                                                                         Run 2 Volts
                                    42                                                        6                          Power kVA Spec
                                                                                                                         Run 1 Power

                                    38                                                        4                          R 2P
                                                                                                                         Run Power

                                    34                                                        2

                                    30                                                         0
                                         0   50   100      150       200        250   300   350
                                                        Fuel Cell Current (A)
               Big Brother
Vehicle dynamics model predictions on
fuel cell power
      , p
  Flat, improved road
  (μ = 0.08, speed ~ 10 mph)
     p        p
  Sloped, improved road
   (μ = 0.08, 4 mph, slope ~ 10%)
  Flat, off road
   (μ = 0.3, speed ~ 2.5 mph)
  Sloped, off road
  (μ = 0.3, 2 mph, slope ~ 10%)
            Big Brother
Electronic control via joystick (drive-by-
wire) allows for ease in remote control of
Powering hydraulic pump with alternative
energy source preserves drive and steer
control logic
                     Big Brother

   Solid model packaging of Hydrogenics 12 kW fuel cell,
hydrogen storage, DC converters, motor drive, electric motor,
                        and clutches
Big Brother Packaging
Big Brother Rollout
PEM fuel cells have sufficient power to weight ratio to
             ll to di    i      hi l
power small t medium size vehicles ranging fi from
~1000 lb (~453 kg) to ~6000 lb (2268 kg).
PEM fuel cells output a nominal voltage of 50 volts
   d       load d this lt
under no l d and thi voltage d  drops as current t
increases. This voltage level is adequate for powering
small vehicles (~1000 lb; 453 kg) but must be
converted to a higher voltage for larger vehicles
(~5000 lb; 2268 kg).
PEM fuel cell power packages are heavier than the
equivalent internal combustion engine package 697 lb
(316 kg) for 12 kw (16 hp) fuel cell versus 87 lb (39 kg)
for a similarly powered 15 hp (11.2 kw) Kohler gasoline
   g )
The cost of fuel cells systems compared
to internal combustion engines as of this
       g     g
writing is higher.
The purity of hydrogen required for PEM
fuel cells is high to avoid contamination
which limits life of the fuel cell stack.
Some fuel cells manufacturers (but not
all) require externally supplied de-ionized
water to hydrate the stack.
Most fuel cell manufacturers recommend that the fuel cell
not be subjected to temperatures below the freezing point
of water. This limits their functionality in vehicles
compared to internal combustion engines which can
operate at much lower temperatures.
As of this writing the availability of hydrogen the cost of
high purity hydrogen, and the lack of a distribution system
for hydrogen compared to gasoline or diesel fuel make
                     p                     ,         y
fuel cell vehicles impractical. However, this study has
shown that hydrogen mobility platforms can be
implemented with current off-the-shelf fuel cell technology.
              ,           y g          , pp          off-the-
Both Nuvera, Inc. and Hydrogenics, suppliers of off-the-
shelf “balance of plant” fuel cell systems are capable of
supplying fuel cell systems for mobility applications. This
technology is improving quickly and prices are becoming
more economical as production and technology levels
     Michigan Tech
Keweenaw R
K                h Center
         Research C
  Former US Army Test Site
  500 acre test track
  Modeling and Simulation Group
  Test and Validation Group
  Snow Research
  www mtukrc org
   For more information contact
Jay Meldrum at
                                Fuel Cell Efficiencies
                                                                 Variable Low Voltage DC 37-57 VDC

Input                                 26,667    watts                  High amperage = 350 amps max

Efficiency @ max power                    45%

Output (Net Rated Electrical)         12,000    watts

DC-DC CONVERTERS                                          Low volt / high amps to High volt / low amps

Input                                 12,000    watts                     Output 324 VDC at 14 amps

Efficiency                            82.0%

Output                                  9,840   watts

MOTOR DRIVE                                                                 Convert DC to 3-phase AC

Input                                   9,840   watts                                  Output 240 VAC

Efficiency                            94.0%

Ou pu
Output                                  9,250
                                        9, 50    a s

AC ELECTRIC MOTOR                                       Convert Electrical Power to Mechanical Power

Input                                   9,250   watts                                  Output 1765 rpm

Efficiency                            92.4%

Output                                  8,547   watts

V-BELT                                                                          1.7 : 1 Speed increasing

Input                                   8,547   watts                                  Output 3000 rpm

Efficiency                            95.0%

Output                                  8,119   watts           10.9       HP

Convert Efficiency (after FC)         67.7%

Overall Efficiency (from H2)          30.4%
Diesel Engine/Electric Motor Clutch
         Fuel Cell Information
        H d
5 kW Hydrogen P          Exchange M b
                  Proton E h                          F l C ll
                                    Membrane (PEM) Fuel Cell (5 kW
= 6.7 HP)
      From Nuvera Fuel Cells of Cambridge, MA
             0.33                                  99.999%
      Uses 0 33 kg/hr of Ultra High Purity (UHP = 99 999% pure)
Hydrogen at max power
      Weight = 219 lbs (dry weight, not including power conditioning
or Hydrogen supply)
      Produces an unregulated DC output b t
      P d                 l t d       t t between 26 – 52 voltslt
      DC Generation Efficiency = 52% (Produces as much heat as
                                           (2.5 KW),
      Startup Time: 12 secs to half power (2 5 KW) 5 – 12 minutes
to full power (5 kW)
      Requires 8 L of DeIonized water for operation
      Requires 300 watts of external power for startup and shutdown
              H2 Information
Tanks: 2,015 psi, Aluminum tank 7” dia. X 38”; 15.7
lit         lbs,
liters, 45 lb CGA 350
      At max power one tank will run the fuel cell for 34
Pressure Regulation:        2,000 psi tank pressure must be
reduced to 15 psi for fuel cell
              Tri-    Switch-
Matheson Tri-Gas Switch-Over Manifold
      Automatically and mechanically switches from low
tank to new tank
        g pressure isolation valves allow removal of
      High p
empty tank without shutdown
      All stainless steel components and high pressure
                        g purity gas
vent valves insure high p y g
            DC/DC Information
DC/DC CONVERTER                          Required to stabilize the fuel
cell s             voltage.
cell’s DC output voltage
       Zahn Electronics Model DCDC24/36/5000 CCH63250-SSU
“A 2-quadrant, crystal controlled, double half H bridge, interlaced,
boost converter based on HC08 microcomputer technology”      gy
Pulse Width Modulation: Switching Frequency = 31,250 Hz exactly
At 50% duty cycle, the input and output voltage and output current
ripples are zero
       Effi i     (5 000    tt i 4 800      tt
96% Efficiency (5,000 watts in; 4,800 watts out) t)
Input Voltage DC = 18v to 60v            Input Current = 250A max
Output Voltage DC = 20v to 60v (must be 2v higher than input)
       Set to 38.5 v in order to charge battery bank.
            Battery Information
BATTERY BANK Provides: startup/shutdown power for fuel cell, burst
                     motors,                                     motors.
power capability for motors and regenerative power storage from motors
Odyssey PC680 MJT (Metal Jacket, Top post)        Absorbed Glass Mat
(AGM) ($86 each)
Sealed dry cell valve regulated lead acid (VRLA) gas recombination
State of ChargeVolts3X Volts100%12.84 or
Cyclic Charge Voltage = 14.4 – 14.8V @ 77oF       3X = 43.2 – 44.4V
Float Ch      V lt      13 5 13 8
Fl t Charge Voltage = 13.5 – 13.8 V @ 77 F77oF          40.5 41.4V
                                                  3X = 40 5 – 41 4V
No initial Charge Current Limit
Charge voltage must not exceed 15.0V              3x = 45V
              g    p
Cold Cranking Amps = 220A
Pulsed Hot Cranking Amps (5 sec) = 680 A
         Motor Information
                           g             p
The 56:1 overall reduction gives us 107 rpm at
the sprocket
This should have produced 3.3 mph
While on the test stand we could only get 96 5
rpm at the sprocket
         p      p             p
That drops the speed to 3.0 mph
When the track is on the ground the higher
resistance lowers speed more.

I suspect that pushing the motor from 24v to 36
v was not as linear as we assumed
              More Motor Info
B h d DC motor b M                     Model C40-ZP-
                      by Magmotor M d l C40-ZP-300FX
Nominally: 24 v, 4000 rpm, 3.8 HP Peak Efficiency = 84.8%
Pushed in this application to: 36 v, 6000 rpm
Mated with a GAM Impact Series Gearbox        JPG-W-090-028G-
                                              JPG- 090-028G-
     28:1 Gear Reduction through a 2-stage planetary gearbox
Additional 2:1 gear reduction using 28T:14T sprockets and #40
Total Gear Reduction = 56:1 6000 rpm motors reduce to 107 rpm at
              Motor Controller
R b Q DC M    Motor C      ll Model
                     Controller M d l AX2850HE
A two channel motor controller using high-efficiency Power
MOSFET transistors controlled using Pulse Width Modulation
(      )                         p          g        p
(PWM) at 16 kHZ. The AX2850 power stages can operate from 12
to 40 VDC and can sustain up to 120A of controlled current,
delivering up to 4,800W (approximately 6 HP) of useful power to
each motor.
60 amp Maxi Fuses inline on input of each channel
Unit requires a rechargeable battery in the system to handle
Futaba Attack 2DR: 2 channel Digital Proportional R/C system
      T2DR transmitter, R132JE receiver at 80 mHz
           Safety Stop
CONTACTOR Relay to disconnect primary
power via Emergency Stop Switch
           #586-           Contactor,
   Stancor #586-906 Power Contactor
200 amp continuous, 36 VDC, SPNO
         E-Stop, Push-L k T -R
   IDEC E-St     P h       Turn-
                 Push-Lock Turn Reset,t
60mm head
TRACK         Production snowmobile track
Camoplast 9005C Cross Country track
   62-pitch (156 i ) f ll clipped, 15 i h
   62- it h        in.), fully li d   inch
wide with 1 in. lugs
   Uses 9 tooth extrovert driver
             Inverter and Wiring
OutBack Power Systems FX2536MT
2 500 VA                        Output,                        20.8
2,500 VA, True Sinewave AC Output continuous output current = 20 8 amps ACrms
92% Efficiency
DC Input Range              28.0 – 45.3 VDC
Including MATE2 system controller and display with RS232
Intelligent battery charging at a maximum of 35 amps DC
DC Input Wired with 1/0 wire, SB quick disconnect, and 80 amp ANL fuse
Weight = 63.8 lbs with INPUT cables attached
1/0 stranded cables Cobra Wire & Cable XFLEX            291 max amps
#2 AWG 2641 x 36 ga., high current power cable
Terminals and connectors:
MagnaLug hex-crimped lugs
                       contacts, hex-
Anderson PowerPole contacts hex-crimped
SB Quick Disconnect Housings: Large = 175 amp, Small = 50 amp
Heat shrink tubing with meltable sealant