Modular vehicle
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The modular vehicle concept is not new. The horses that drew stagecoaches could be changed at rest-stops so that there was fresh horsepower to keep the coach moving while the tired animals had time to recover.
A similar approach has been proposed for modern electric vehicles.
Battery recharging in electric vehicles
With an electric vehicle, the recharging of batteries takes much longer than filling the fuel tank of a conventional vehicle, especially if it is done at a slow enough rate to maximize battery life.
There are two principal ways to address this problem: battery exchange and chassis exchange.
Battery exchange
In the first approach, spent batteries are removed from the vehicle, and replaced by fresh batteries while the original ones are recharged. The disadvantage is that batteries are very heavy and vulnerable to damage while being moved.
There is also a risk of fire, explosion or electrocution as a result of having to disconnect and reconnect batteries and their cooling system in the vehicle.[1]
Chassis exchange
In the second approach, a vehicle's entire power and fuel system, plus its wheels and suspension, are contained in a single module or chassis. When the batteries need recharging, the vehicle's body is lifted off and placed onto a fresh power module.
An advantage of this system is that batteries do not have to be removed or reinstalled, and their connections remain intact. As well, if the power modules are standardized, it is possible to fit a range of vehicle bodies to any power module, to meet different needs at different times.
In either approach, the driver could still "top-up" the vehicle's batteries, by plugging in to a suitable power source, whenever convenient.
History of the modern modular vehicle
The world's first road-licensed quick-change modular electric vehicle, based on a patent awarded to Dr Gordon E Dower in 2000 [2], was shown at the World Electric Vehicle Association 2003 Electric Vehicle Symposium EVS-20 in Long Beach, California, USA.
Dower described the vehicle's two parts as its motorized deck, shortened to modek, and its "containing module" or ridon. When attached to each other, the vehicle thus formed was dubbed the Ridek.
In 2004, General Motors tried to patent a modular vehicle called Autonomy[3] but the attempt was unsuccessful because Dower’s patent already existed.[4]
A team at GM did, however, continue to work on Autonomy, which was intended to be powered by a hydrogen fuel cell. They unveiled a non-driveable version in January 2002 at the Detroit Auto Show.[5]
The driveable prototype, called Hy-wire was unveiled at the Paris Auto Show in September, 2002.
An important difference between the Ridek and GM vehicles was that Ridek used mechanical connections between the modules for braking and steering, which automatically engaged when the body was lowered on to the chassis, whereas GM used an electronic, or "drive-by-wire", connection for steering, braking and controlling the 4 wheel motors.
The chassis in the GM vehicle, dubbed a skateboard, was only 11 inches thick and had less room for batteries than in the Ridek vehicle's modek.[6]
The body was intended to be lifted with a spider hoist and took about half an hour to bolt onto the skateboard, whereas exchanging the chassis in a Ridek vehicle was designed to take a few minutes.
Neither Autonomy nor Hy-wire was ever road licensed, but all three Ridek prototypes were, and Ridek III is in regular use in Washington state.
Flexibility
Modular vehicles using the chassis exchange approach make it possible to use different types of bodies on one standardized chassis.[7] There could be specialized bodies for taxis, for example.
Depending on the size and condition of the batteries in them, the chassis could be offered in short-range and long-range versions. The longer-range batteries would be heavier and, therefore, less desirable when making short trips only.
Also, the modular chassis, with its batteries and motor, are relatively easy to work on, since there is no vehicle body to impede access.
Implications for vehicle ownership
By using a standardized chassis, which is replaced whenever the batteries need charging, it has been suggested that individuals may wish to own just the vehicle body (or more than one body, if they prefer to have options such as a sedan, convertible or light truck).[8]
The chassis, including its costly batteries, could be part of a fleet, maintained by the fleet owner, and offered under contract, being exchangeable as needed.
See also
References
- ^ Berr, October, 2008, Dublin Institue of Technology, Department for business and Regulation, Department for Transport, Investigation into the Scope for the Transport Sector to switch to Electric Vehicles and Plug-In Hybrids, appendix B.1.2.3., p. B3
- ^ Dower, Gordon E, 2000, US Patent: Modular vehicle construction and transportation system
- ^ Patent application 10/966,548, filed 10/15/2004, assigned General Motors, lead inventor Adrian B Chernoff
- ^ Patent 10/966/548,denied 2/23/2006, Attorney docket no: GP -3015791/GM0268PUS-1
- ^ King, Ralph, GM'S Race to the Future - the inside story of how the world's biggest automaker came to see the hydrogen car as its salvation--and took the lead in the engineering challenge of the century, Business 2.0 Magazine, Oct 1, 2003.
- ^ Chernoff, Adrian B et al, 2003 US Patent: Vehicle chassis having systems responsive to non-mechanical control signals
- ^ Chernoff, Adrian B et al, 2003 US Patent: Vehicle body interchangeability
- ^ Dower, Gordon E, A Better Plan for a Better Place for electric cars