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Leading The Charge
The popularity of electric vehicles rises as battery and fuel-cell technologies improve.
Date Posted: June 29, 2007 12:00 AM
Design Challenges
A number of challenges remain for
both hybrids and fully electric vehicles. Capacity alone is not enough.
The technology should require minimal maintenance. Additionally, it
must safely survive accidents. These
systems need to be rugged and able
to endure a wide range of temperatures as well.
Hybrid vehicles tend to have an
intricate mechanical design that's
more complex than fully electric solutions like the Roadster. Their system
redundancy, energy storage systems,
and electrical engine control are only
somewhat similar. While cars don't
balance on two wheels, a comparable solution can be found in the fully
electric single-passenger vehicle,
Dean Kamen's Segway Human
Transporter (; see "Smart
Motion Makes For A Smarter
Design,").
Since it's also a robotics platform (see "Segway's Concept Centaur:
Computer Controlled Mobility
Leads To New Concepts,"), its design addresses similar challenges faced by electric and
hybrid vehicle designers.
For example, the Segway platforms employ numerous processors
for control (). A number of
these processors, though, simply
monitor the system. While this
leads to better efficiency, safety,
and reliability, the design can get
complex because of the number of
subsystems involved.
Multiprocessing programming
challenges can be as difficult to solve
as improving the performance and
reliability of the energy storage system. Low-cost 8- and 16-bit microcontrollers are meeting the needs at this
point, but the falling prices of 32-bit
platforms will change transportation's architectural landscape over
the next few years.
SEGWAY TRANSPORTER () |
Style: one person standing |
Range: 16 to 24 miles |
Speed: 12.5 mph |
Carrying capacity: 100 to 260 lb |
Motors: two brushless dc servomotors |
Battery: two Saphion lithium-ion battery packs |
Ground clearance: 3 in. |
Turning radius: 0 in. |
Weight: 105 lb |
Footprint: 19 by 25 in. |
Tires: 19-in. puncture-resistant tire |
Price: starting at $5000 |
|
TESLA MOTORS ROADSTER () |
Style: two-seat, open-top, rear-drive roadster |
Top speed: more than 130 mph |
Acceleration: 0-60mph in about 4 seconds |
Range: approximately 250 miles/charge |
Drivetrain: electric motor with two-speed electric-shift manual transmission with
integral differential, traction control |
Transmission: |
Gear |
Ratio |
Overall |
First |
4.20:1 |
14.3:1 |
Second |
2.17:1 |
7.4:1 |
Final |
3.41:1 |
|
Motor: three-phase, four-pole electric motor; 248-hp peak (185 kW); redline at 13,500 rpm; regenerative "engine braking" |
Front suspension: telescopic damper unit; anti-roll bar |
Rear suspension: independent; upper and lower wishbone; co-axial coil
spring/telescopic damper |
Brakes: four-wheel disc brakes with ABS |
Chassis: bonded extruded aluminum with four-wheel wishbone suspension |
Dimensions: overall length 155.4 in.; width 73.7 in.; height 44.4 in. |
Wheelbase: 92.6 in. |
Curb weight: around 2690 lb |
Lights: halogen low- and high-beam headlamp assemblies, LED tail lights |
Energy storage system: lithium-ion batteries, 3.5-hour minimum recharge time,
expected lifetime in excess of 100,000 miles, microprocessor controlled, heater for
cold weather charging to 20°C |
Security: PIN for operating the vehicle; valet mode restricts speed, acceleration,
and distance |
Price: starting at $92,000 |
|
microcontrollers