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Revolutionary Invention... or Expensive Toy? Following months of media hype and speculation, inventor Dean Kamen’s Segway Corporation have finally unveiled their unique machine – a scooter with an uncanny ability to replicate the balance and motion mechanisms of the human brain. While some analysts have touted that the creation will ‘change the shape of cities’, others remain unimpressed. In this article we take a closer look at the ‘Segway’ and its brilliant technical design (well, at least as close as we’re allowed!). By Sammy Isreb 6  Silicon Chip www.siliconchip.com.au I t sounds as though it has the elements of immense success. With over $100 million in funding from America’s top venture capital firms and designed by some of the top engineering minds available, Segway developed a product which gained some phenomenal media hype leading up to its release. Adding to the hype, some amazing quotes from big names – “As big a deal as the PC”: Steve Jobs – “Maybe bigger than the Internet”: John Doerr, a venture capitalist who backed Netscape and Amazon.com. So what exactly is the Segway HT (Human Transporter)? A very fancy powered scooter would be the simplest answer. Based on a footprint of only 48cm by 63.5cm, the Segway is designed to take up as little space as possible. Touted as a solution to inner city transportation woes, the Segway is meant to transport people quickly and efficiently, taking up no more room than a pedestrian. It was never designed to replace cars, simply to provide an alternative for short distance commuting and to www.siliconchip.com.au clean up densely crowded and polluted city areas. It seems as though this admirable desire to simplify short distance commuting puts the Segway in the same market category as a myriad of other devices – bicycles, rollerblades, scooters and skateboards, to name just a few. What sets the Segway apart from the rest is its safety, simplicity of use, and highly ergonomic design. The Segway was designed from the outset to mimic the body’s natural sense of balance and motion. It uses some incredible sensory and computing technology simply to stay upright, providing unmatched ease of use. To start moving forwards or backwards the user simply leans slightly forward or backward. Leaning further will increase speed, while moving towards centre will slow down. It is a natural human response to try and upright one’s body under panic. Segway uses this phenomenen to dispense with the need for mechanical brakes – as the user assumes an upright position it slows then stops completely. Steering is as simple as twisting the handlebar, with the amount of twist determining the turning speed. Amazingly, the unit can turn on its own footprint, rotating on the spot. Intelligent key The amazing technology begins as soon as you start the Segway using the electronic “Intelligent Key”. A 128-bit encrypted key word is stored on the key, which is required to start the particular unit it was shipped with. In addition to the security feature, the Intelligent Key also stores the user’s profile, with all units supplied with “beginners” and “advanced” keys. The beginner’s key limits the Segway’s top speed, among other things. It is envisaged that in the future users will be able to customise their operating parameters via programmable keys. User display Next to the key slot on the ‘handlebar’ is an LCD display which provides the user with all relevant information such as battery charge level and current operating conditions. This display is designed for ease of January 2002  7 gravitational field. The design philosophy of the Segway has been to incorporate a very high level of redundancy into the device, which has been reflected though the use of five rather than the required three gyroscopes. Each of the Segway’s gyroscopes consists of a solid-state angular rate sensor, a device of silicon construction used to measure rotation. This uses a tiny silicon wafer attached to a supporting structure. An AC voltage is applied to the wafer, causing it to vibrate in a predictable manner. When the device is moved, the vibration is altered and thus measured and used to determine the degree of rotation. Electronics Controller Boards The Segway uses dual, fully redundant controller boards to accept inputs from the Inertial Sensor Assembly, along with other sensors, in order to process the data and appropriately drive the motors. While Segway is very secretive regarding the architecture of these processor boards, they have reportedly claimed 10 onboard processors distributed amongst the two boards, with around three times the processing power of an average consumer PC. If either of the boards experiences a failure, the other board assumes control, and will bring the Segway to a safe stop. Riding is said to be as easy as falling off a log! Lean forward and it goes forward. Lean back and it stops, then goes backward. Twist the handlebar one way and it turns that way. And vice versa. visibility in high levels of sunlight. Chassis Design The chassis is constructed from aluminum, sealed from the atmosphere to protect the electronics inside. Aside from obviously providing somewhere to stand on and a case for the internals of the unit, the chassis has been designed to act as a heatsink for the complex assembly of gyroscopes, processor boards, motors and batteries. According to the manufacturer’s testing, the chassis can withstand an amazing seven tonnes of load. Inertial Sensor Assembly This subsystem is probably one of 8  Silicon Chip Batteries the most amazing of the entire device. Incorporated into the top rim of the chassis are hidden injection-moulded rubber diaphragms. When the user gets onto the unit the diaphragms deform towards the electronics below, engaging the self-balancing systems. At this stage the unit is aware of the operator’s presence and begins balancing the unit and the user upright. In fact, anything but the hardest shove to a Segway rider will not tip them. The Inertial Sensor Assembly resides within the chassis, sandwiched by the motors to one side and the batteries to the other. The assembly consists of five aviation-grade gyroscopes, used to determine the location of the machine in relation to the Earth’s Probably the most conventional technology aboard the Segway are the rechargeable batteries, which are supplied in either Nickel Cadmium or Nickel Metal Hydride varieties. According to early testing, fully charged Ni-MH batteries will be able to propel the Segway anywhere from 17km to 28km depending on the terrain, weight of the user, and method of riding. Each Segway uses two batteries, which are sealed and incorporate charge and temperature monitoring electronics. The unit is charged from mains power and will take around six hours to fully charge. Motors and Transmission Each wheel is driven by two (redundant) high speed brushless electric motors. For each wheel, the motor consists of two windings, functioning as separate electric circuits, with full www.siliconchip.com.au redundancy, providing a single mechanical unit. In order to allow the motors to run at a high speed, which optimises efficiency, a 24:1 two stage helical sealed transmission unit is used in each wheel. In addition to maximising efficiency, the beauty of the drive train design is the fact that by running the motors in opposite directions the unit is able to turn on the spot. This is a major selling feature of the Segway. In addition to this, the motors can propel the unit to a top speed of 20km/h, even with operators weighing up to 110kg. The unit has no brakes as such, using the motors for accelerating, turning and braking. When the user signals his intent to slow or stop by leaning back, the control boards cause the motors to decelerate. Wheels and Tyres Each wheel is made from a forged steel hub surrounded by a glass-reinforced thermoplastic rim. Each rim has a cutaway hole for threading a bicycle-style lock through. The wheels attach to the main unit via a single nut mechanism. In order to maximise the range of the unit, the wheels have special low-rolling-resistance silica tyres, which are air inflated and puncture resistant. Synopsis As the amazing array of technological features will surely attest, the Segway is indeed a machine which could go a long way towards being a personal transportation medium. It does, however, come with a US$3000 price tag (AU$6000) for the yet-to-be-released consumer version Specifications: Top speed: 20km/h Weight: 36kg Dimensions: 48 x 63.5cm Weight capacity: 110kg person with 34 kg of cargo Range: About 28km on even ground, or 17km on undulating terrain Motors: Each wheel is driven by a two horsepower brushless DC electric motor Transmission: Two-stage transmission with 24:1 gear ratio Computer: Two redundant processing boards with 10 processors distributed amongst them Power: Two rechargeable batteries. Either Ni-MH or Nicad Sensors: Five solid state gyroscopes plus sensors to detect presence of user Brakes: No mechanical braking system. Regenerative engine braking. Turning radius: On the spot Security: Intelligent Electronic Key system, using 128-bit encrypted key code. Also determines operational profile Driver interface: High visibility LCD display which indicates battery charge and operational status Price: Approx. US$3,000 (consumer version) and an astounding US$8,000 (AU $16,000) for the commercial model recently released. But this has not deterred several US corporations, including the US Postal Service, The National Park Service and General Electric, amongst others, from signing on to field test the units over the next few years. While all those involved with the Segway believe – or hope – it will become the next craze to sweep the world, one can not help but wonder why the average individual consumer would wish to spend almost half the price of a new small car on a device which is intended to replace one of life’s most healthy activities – walking. Depending on the success of the corporate trials, mass production for the consumer market could quite easily see the price fall to attainable levels. Until then the Segway will remain SC a very expensive toy! UM66 SERIES TO-92 SOUND GENERATOR. THESE LOW COST IC’S ARE USED IN MANY TOYS, DOORBELLS AND NOVELTY APPLICATIONS 1-9 $1.10 10-24 $0.99 25+ $0.88 EACH INC GST www.siliconchip.com.au January 2002  9