The Segway PT (originally called the Segway HT ) (HT was for human transporter) is a two-wheeled, self-balancing personal transporter by Segway Inc.Invented by Dean Kamen and brought to market back in 2001.
The Segway PT (referred to at the time as the Segway HT) was developed from the self-balancing iBOTwheelchair which was first initially developed at University of Plymouth, Devon England in conjunction with BAE Systems and Sumitomo Precision Products.
Segway’s first patent was filed in 1994 and granted 3 years later in 1997 followed by othersincluding one submitted in June 1999 and granted in October 2001 and was developed incomplete secrecy under the codename “Project Ginger”
Steve Jobs was one time quoted as saying that it was “as big a deal as the PC”, (but then later retracted that saying that it “sucked”, presumably referring to “the design” but commenting about the boutique price,
These are not large, physical gyroscopes like you might find on a ship or aeroplane, or as an educational toy. They are micro-electrical-mechanical systems (MEMS), or gyroscopes-on-a-microchip.
While relatively rare and expensive when the first Segway PT was revealed in 2001, these days such chips are encountered on a daily basis in iPhones and other smartphones, Nintendo Wii & Sony Playstation controllers, etc. As Silicon Sensing notes on their website page dedicated to the work they did with Segway, Inc: link here Silicon Sensing
Control Units (CU)
Two sophisticated circuit boards from Delphi electronics provide the brain and the muscles for the system. Delphi Electronics were chosen as a partner for their experience in mass production of high quality automobile electronics for sophisticated applications such as airbags.
Each circuit board is fitted with a Texas Instruments (don’t they make calculators?) signal processor that monitors the entire Segway PT system and checks 100 times per second for any malfunction or other conditions that require an immediate reaction.
It reads the information from the balance sensors to determine whether the driver leans forwards or backwards. This information is supplied without time delay to conduct the energy from the accumulator through a set of 12 “high energy-high electricity-field effect transistors” (FET’s) to the motors.
These calculations occur one hundred times per second and the motors are adjusted up to one thousand times per second, a reaction time that far exceeds human perception time. After a malfunction, each circuit board of the Segway PT can completely switch to the other board if there is a major malfunction and keep operating and activate a safety shutdown.
Each board is connected with the electrical circuits of both motors and under normal operating conditions, the processing power is divided
The motors of the Segway PT are unique in many ways. Produced by Pacific Scientific, a business branch of Danaher, they are the most powerful motors that have ever been produced in their weight and size class. Both motors require masive 330 watts for continuous operation and produce a short time peak performance of up to 4 PS.
The motors use brushless servo-technology. This means there are no mechanical contacts that wear out and thereby reduce output.
The magnets are comprised of an extremely powerful and rare earth metal: Neodym-Iron-Bor. Each motor is fitted with two independent windings, from which each of it’s own circuit boards are steered.
Under normal conditions of use, the windings work parallel to each other and divide the workload. In the case of a malfunction the motor deactivates the malfunctioning winding and controls the remaining one to maintain control over the Segway PT until it is brought to a stop.
The motor accurately calibrates the output from up to 8000 turns per minute, which enables a very high power level within a short range. By measuring the position of the magnets, redundant, contactless and analogue sensors give feedback from the motor to the control units. The motor axis is the only movable part.
Days out in Devon for adults
The new Segway PT models are assembled with saphion lithium ion batteries. Segway chose to work with Valence Technology, the leading developers of efficient and safe accumulators. The base for the new accumulators is formed by Saphion ® technology (patented from Valence), which is made from phosphates. Saphion is stable and safe and therefore the ideal solution for daily use. It has a longer lifespan than the traditional NiMH accumulators.
The range is increased while the charging time is reduced. Every accu comprises a compound of high performance cells and a specially developed circuit board that permanently monitors the temperature and tension on the batteries from different positions.
The accu casing is sealed by a vibrating welding method, which forms the exterior of the compound into one single, consistent structure. The seal protects against moisture and remains so strong that it flawlessly stands up to complete and extreme testing. The accus’ integrated electronics enable “intelligent” charging. The owner plugs the Segway into a power point and the accumulator itself chooses the appropriate charging speed based on temperature, tension and current charge level. The accu is quickly charged and switches then into idle and maintenance modes. The Segway PT owner must spare no thought about timing – simply plug in and the rest happens automatically.
Under normal operating conditions the Segway PT reliably monitors both batteries and consistently discharges them. In the case of battery failure, the system can come safely to an emergency stop with only one battery.
You can find out more about batteries here at PT repairs