Man Suffers Serious Injuries Due to Self-Balancing Scooter Defect

Engineering Expert WitnessThis case involves a male in his late 20’s who was participating in an intramural sports league in which gyroscopically-stabilized scooters were used by all participants. During one of the events, the man’s scooter lost power and stopped working while in use, which resulted in him falling and sustaining a severe injury. He later had to undergo surgery. It was claimed that the scooter should have provided some warning to the rider before shutting down due to a lack of charge.

Question(s) For Expert Witness

  • 1. Please describe your engineering experience with similar products.
  • 2. In your experience, what are some reasons a scooter may suddenly lose power and stop working?

Expert Witness Response E-008183

I am familiar with Segway, as I worked as a tire design engineer with these scooters while I was a Michelin Tire employee. These scooters are battery powered and may lose power because the battery is depleted. However, in this case, the unit is supposed to warn the rider. If the rider continues to use it, at a given point the unit will make itself come to a stop while still balancing. It is designed to not suddenly lose power. If the unit did indeed lose power with no warning, this is a real problem, as the stability of the machine depends on power. The manufacturer has access to a log on each machine which keeps track of the machine operation. A sudden power loss should be discoverable via this log. An electrical connection problem or battery malfunction could explain a sudden power loss.

Expert Witness Response E-008051

I have analyzed 6-8 cases in which I have reviewed downloaded information and analyzed control data (details under protective order). All those cases resolved positively. These scooters lose power due to old batteries, insufficient recharge, or overuse on charge. The scooter should detect the low battery condition and perform a controlled shut down with very specific notification and procedure, depending on the model and internal software version. I have performed analyses on a number of cases. Often, failure to provide proper training (video, summary of manual, demonstration and pre-trip training) have been the cause of injury incidents at shut down or coming to a complete stop. The details are very important in determining causation. The stored event data is also very valuable.


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