# How Self-Balancing Vehicles Warn Users Before They Tip Over > A safety system for self-balancing vehicles that monitors how much 'room' the machine has left to accelerate before it loses its ability to stay upright. - **Patent:** US 6302230 - **Original title:** Personal mobility vehicles and methods - **Owner:** Deka Products LP - **Granted:** 2001 - **Status:** Public domain (expired) - **Times cited:** 172 - **Field:** consumer_electronics, mechanical, automotive ## What it does This patent describes a safety mechanism for vehicles that are inherently unstable, like a Segway. Because these machines rely on active motors to stay upright, they have a physical limit to how fast they can accelerate to compensate for a lean. The system calculates a 'balancing margin'—the gap between the vehicle's current speed and the maximum speed it can reach while still maintaining balance. If that gap gets too small, the system triggers an alarm, such as a beeping sound or a physical 'ripple' vibration in the motors, to warn the rider to slow down. ## What it does NOT cover - Does not cover vehicles that are inherently stable, such as four-wheeled cars or bicycles with kickstands. - Does not cover systems that automatically stop the vehicle without providing a warning to the user. - Does not cover non-motorized balancing devices like a standard unicycle or tightrope walker. ## The clever bit The system treats 'acceleration potential' as a finite resource, effectively quantifying the safety buffer of a dynamic system that would otherwise be invisible to the rider. ## Real-world examples 1. Segway Personal Transporter (PT) 2. Self-balancing hoverboards 3. Electric unicycles ## Why it matters This technology was essential for the commercial viability of the Segway PT. Without this safety 'headroom' monitor, a rider could unknowingly push the machine to its physical limit, causing the motors to lose their ability to balance and leading to a sudden fall. It established the standard for how active-balancing personal transport devices manage user safety. ## Frequently asked questions ### What does How Self-Balancing Vehicles Warn Users Before They Tip Over cover? A safety system for self-balancing vehicles that monitors how much 'room' the machine has left to accelerate before it loses its ability to stay upright. ### Who owns patent US 6302230? Deka Products LP owns this patent, granted in 2001. ### When does this patent expire? This patent has expired and is now in the public domain — anyone can use the invention freely. ### What is patent US 6302230 cited by? This patent has been cited by 172 later patents that build on its ideas. ### What problem does this patent solve? This technology was essential for the commercial viability of the Segway PT. Without this safety 'headroom' monitor, a rider could unknowingly push the machine to its physical limit, causing the motors to lose their ability to balance and leading to a sudden fall. It established the standard for how active-balancing personal transport devices manage user safety. ### What does this patent NOT cover? Does not cover vehicles that are inherently stable, such as four-wheeled cars or bicycles with kickstands. **Full plain-English explainer:** https://patentbrief.org/patent/us/6302230/segway-personal-transporter **Original patent:** https://patents.google.com/patent/US6302230 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [How Early Vehicle Airbag Safety Systems Work](https://patentbrief.org/patent/us/3552770/automotive-airbag-safety-device) — A 1968 patent describing an early vehicle safety system that uses a rapidly inflating confinement to protect passengers during a collision. - [How the iRobot Roomba Automatically Cleans Floors Without Falling Down Stairs](https://patentbrief.org/patent/us/6883201/roomba-autonomous-vacuum) — A 2002 patent describing an autonomous floor-cleaning robot that uses sensors to navigate rooms, avoid cliffs like stairs, and sweep debris into a removable bin. - [How Elisha Otis Invented the Modern Safety Elevator](https://patentbrief.org/patent/us/31128/otis-elevator-safety-brake) — An 1861 patent by Elisha Otis describing a mechanism to prevent elevators from falling if their support cables snap. - [How James Plimpton Invented the Modern Roller Skate](https://patentbrief.org/patent/us/37305/roller-skates-plimpton) — A 19th-century invention that introduced pivoting wheels to roller skates, allowing users to steer by leaning their bodies. - [Boosting Fuel Cell Power for Vehicles Using Oxygen Injection](https://patentbrief.org/patent/us/5346778/electrochemical-load-management-system-for-transportation-applications) — A system that boosts a vehicle's fuel cell power by injecting pure oxygen into the air supply when the engine needs extra energy.