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GM’s HyGeneral Motors has unveiled the Hy-wire concept car, the world’s first drivable vehicle that combines a hydrogen fuel cell with by-wire technology. The heart of the Hy-wire is an innovative “skateboard” chassis, which contains all of the sedan’s propulsion, transmission, steering and braking components within its 279mm high frame and provides a single electrical connection to the body. In essence, fuel cells enable a skateboard chassis and this flat plane provides unprecedented freedom for designing the vehicle body. 8  Silicon Chip Complementing this, the by-wire systems allow a single docking connection between the skateboard chassis and the body, and this creates great opportunities for reinvesnting the interior layout. Hy-wire was literally designed from the inside out, with form following function. The flexibility of the chassis accommodates multiple interchangeable “snap on” body styles that can be customised to meet customers’ various lifestyles. Fuel Cell Propulsion System Inside, between the aluminium beams of the skateboard chassis, GM engineers have integrated an impressive technology package. A 3-phase electric motor, mounted transversely, drives the front wheels via a single-stage planetary gear with a transwww.siliconchip.com.au mission ratio of 8.67:. It generates a maximum power of 60kW and delivers a maximum torque of 215Nm. Maximum speed is 12,000 rpm. The fuel cell stack consists of 200 single fuel cells connected in series and is roughly the size of a PC tower. It is located in the rear of the skateboard chassis and is cooled using a conventional radiator. The stack, which operates under a pressure of 1.52.7 Bar, has a power density of 1.60kW/l and produces 94kW continuously, with a peak power of 129kW. This delivers between 125V and 200V DC, depending on the load. This is boosted to 250-380V and then converted to 3-phase AC to drive the electric motor. Unlike other fuel cell vehicles, there is no battery in Hy-wire to provide extra power for peak loads. It uses only the fuel cell to provide power, thus simplifying the development and integration. The fuel cells obtain the hydrogen fuel from tanks mounted securely in the centre of the skateboard. The three cylindrical compressed hydrogen storage tanks are made of carbon composite material, have a total weight of only 75kg and store a total of 2kg of gaseous hydrogen at 350 Bar. Yes, you read that correctly – 350 Bar, about 5,000 pounds per square inch! Incidentally, the next stage of development will increase the tank pressure from the current 350 Bar to 700 Bar. GM and QUANTUM Fuel Systems Technologies Worldwide received certification from the top German safety -wire www.siliconchip.com.au institute for a 700 Bar (10,000 psi) hydrogen storage system that could ultimately allow fuel cell vehicles to drive 300 miles depending on the storage volume. Drive-By-Wire, BrakeBy-Wire, Steer-By-Wire, Docking Connection Developed by Swedish-based SKF, the “by-wire” technology enables all of Hy-wire’s major driver-control functions, including steering, accelerator and brakes, to be consolidated into a flexible, hand-controlled unit called the X-drive. It is similar to today’s advanced aircraft controls, where commands are transmitted digitally from the cockpit through electrical cables, or “by wire”, to the various parts of the plane. Hy-wire uses the same technology, allowing the driver to easily control the vehicle with either the right or left hand from the X-drive unit. Drivers also have the option of driving from the left or right driving position because the X-drive is located in a centre console that shuttles from left to right. Because it uses fully electronic connections and controls, the by-wire system simply plugs into the docking connections on the Hy-wire chassis. At the heart of the by-wire system March 2003  9 are smart electro-mechanical actuating units, which convert the driver’s commands from electronic signals to motion. The by-wire system also provides dynamic feedback to the driver via electronic signals. The advantages of by-wire technology in automobile applications include the elimination of steering columns and foot pedals and allows greater design freedom, simplified production of left and right-hand drive models and improved passive safety for the driver. The elimination of mechanical and hydraulic linkages saves   weight and simplifies maintenance because there are fewer moving parts that can wear out. By-wire is more environmentally friendly because hydraulic fluids required for steering and braking are eliminated. Software allows the driver to personalise the handling characteristics of the vehicle by adjusting the feel of steering, braking and acceleration. Adjusting them is as simple as loading a new program. 10  Silicon Chip The Hy-wire’s X-Drive replaces the usual round steering wheel and pedals, giving drivers the option to brake and accelerate with either the right or left hand. The driver accelerates by gently twisting either the right or left handgrip and brakes by squeezing the handgrips. The handgrips glide up and down for steering, somewhat different than today’s vehicles where the steering wheel revolves around a steering column. The X-Drive also incorporates an electronic monitor for rear- view and vital car functions and shuttles easily from side-to-side on a horizontal bar that stretches across the full width of the vehicle. The steering system highlights the basic functions of the by-wire controls. A conventional vehicle uses a direct mechanical or hydraulic connection between the driver’s control www.siliconchip.com.au Specifications: GM Hy-Wire Vehicle: Seating capacity: Fuel storage system: device and the relevant component. For example, the commonly used rack-and-pinion steering system uses a small toothed wheel (the pinion) to engage the rack and to shift it left or right. Tie rods then carry the motion to the steering arms at the wheel. By-wire technology, in contrast, translates the driver’s commands into electrical impulses. If the driver turns the handgrips of the X-Drive, sensors capture this motion digitally and send a signal to an electrical motor that moves the steering rack as instructed. Acceleration is similar to the throttle on a motorcycle, except that a throttle cable does not mechanically activate the throttle valve of the power plant. The by-wire system transmits an electronic signal to the electric motor that drives the Hy-wire’s front wheels. Braking is achieved by squeezing either the left or right hand grip. Grip www.siliconchip.com.au Length/diameter: Total capacity: Total weight: Fuel cell stack: Voltage: Length/width/height: Pressure: Continuous rating: Power density: Electrical traction system: Operating voltage: Maximum rating: Maximum torque: Maximum rpm: Transmission ratio: Total weight: Skateboard chassis: Body: Length: Vehicle weight: Wheel base: Fuel cell and by-wire technology, front-wheel drive, luxury sedan Five Three cylindrical high-pressure tanks of carbon composite material, mounted in the middle of the skateboard chassis 1,161/241mm 2kg 75kg 200 single fuel cells; connected in a series 125-200 Volt 472/251/496 mm 1.5-2.7 Bar 94kW, peak of 129kW 1.60 kW/l, 0.94 kW/kg 3-phase asynchronous electric motor with integrated power electronics and planetary gear 250-380 Volt 60kW 215Nm 12,000 8.67:1 92kg Length/width/height: 4,357/1,670/ 279mm Aluminium frame Steel and fibreglass 5 metres 1,900kg 3,114mm March 2003  11 sensors determine how much hand pressure the driver is exerting and these transmit a signal which applies the brakes. The system, developed together with the Italian specialist, Brembo, works with conventional brake calipers but responds faster. Maximum reliability and safety are essential features of the data-transmission system in by-wire control. All safety systems have built-in redundancy and a back-up power supply similar to those used in fly-by-wire systems. Body and Interior Since Hy-wire’s skateboard-like chassis contains all of the propulsion and control systems – a fuel cell and by-wire technology – designers were free to consider a number of body styles and interiors with what amounts to a fresh canvas to explore an endless range of possibilities for the body style and interior package. GM wanted an obvious transition from where vehicle design is now to where the technology could take it and intentionally designed a vehicle that will highlight the openness in the interior and leave it to the occupant’s imagination to consider the possibilities. The break with conventional automobile architecture is obvious on the very first encounter with the car, which is 5-metres long, 1.87-metres wide and 1.57-metres high. Glass is used extensively, giving 12  Silicon Chip passers-by a full view inside and the passengers a perfect view of the world outside. The absence of a conventional engine means there is no need for a grille up front. So the question became what to do with the open front face where you’d typically put a grille. The designers chose to enclose it with glass, allowing the driver to have a view of the road ahead that has never been possible before. You can see immediately that there is no engine at the front, the pedals and instrument panel are superfluous and the floor is flat from front to back. Hy-wire features large side windows and no B-pillars (the traditional post between the front and rear windows). The rear doors are hinged at the back, allowing the four doors to open very wide, providing very easy access. Anyone who accepts the invitation aboard can look forward to a comfortable and exciting journey. Apart from the unmatched panoramic view for the driver and passengers and spacious interior, Hy-wire offers several other key features. The fuel cell and by-wire systems eliminate the need for a traditional engine bonnet and centre tunnel, resulting in improved legroom. The lack of foot pedals means the driver is not restricted to a specific leg position. Flexibility The X-Drive can slide across for left or right side driving, emphasizing Hy-wire’s outstanding flexibility. Pressing a button on the X-Drive starts the Hy-wire vehicle. Buttons also engage the vehicle’s forward, reverse, and neutral drive conditions. The X-Drive attaches to a very light and transparent-looking centre console. Integrated in this console is a second 15cm colour monitor which allows the driver to view radio controls, heating, ventilation, air conditioning and navigation systems. The design team’s work was characterised by a feeling of freedom – freedom, for example, to position the seats and control module where they wanted to, without any restrictions. They paid particular attention to the seats when developing the Hy-wire’s interior. The five-passenger vehicle has front and rear bucket seats; the centre rear seat folds up to create a table. Lightweight materials accentuate the vehicle’s openness, and the overall environmental-friendly concept is expressed by the choice of natural colours. The sporty yet elegant four-door vehicle has short overhangs, eight-spoke light-alloy wheels with 20-inch tyres in front, and 22-inch tyres in the rear. Cameras have replaced the rearview mirrors and the headlamps and tail-lamps feature LED technology. This technology allows the lamps to be packSC aged in a very small space. www.siliconchip.com.au