CAN in personal transportation devices

Source: CAN Newsletter March 2004

The Segway HT (Human Transporter) has become a popular means of personal transportation in police work, mail delivery and other commercial uses. One of the most intriguing aspects of the transporter is its ability to balance a person on just two wheels while at rest or while traveling at up to 30 km/h. To achieve this balance, it utilizes two micro-controller boards, a BSA (Balance Sensor Assembly), a pair of electric gearmotor drives, a user interface and a pair of 12-Volt NiMH batteries. The link between the handlebar-mounted user interfaces and the micro-controllers uses two redundant Controller Area Networks. Each controller board uses a Texas Instruments DSP (TMS 320LF2406) and Philips CAN transceivers (82C250) that provide the intelligence and regulate the power. Each controller monitors the entire system and checks 100 times per second for any faults or conditions that might require immediate response. The micro-controller reads the information from the Balance Sensor Assembly (BSA) to determine if the rider is leaning forward or backward, and instantly uses this information to deliver power from the batteries to the motors through a set of twelve FETs (field-effect transistors).