Research Papers

A Dynamics-Based Hazard Analysis of Inverted-Pendulum Human Transporters Using Data-Mined Information

[+] Author and Article Information
William Singhose

The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology,
Atlanta, GA 30332-0405
e-mail: Singhose@gatech.edu

Christopher Adams, Dooroo Kim

The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology,
Atlanta, GA 30332-0405

Manuscript received January 29, 2015; final manuscript received January 1, 2016; published online July 1, 2016. Assoc. Editor: Chimba Mkandawire.

ASME J. Risk Uncertainty Part B 2(3), 031007 (Jul 01, 2016) (12 pages) Paper No: RISK-15-1008; doi: 10.1115/1.4032459 History: Received January 29, 2015; Accepted January 06, 2016

When a product is a complex dynamic system that interacts directly with a human, engineers must consider a wide range of possible motions and forces that the device could exert on the human. Such an analysis goes beyond a simple thought exercise and requires detailed knowledge about the system dynamics and the operating environment. This paper presents such an analysis of inverted-pendulum human transporters. The list of hazards is constructed by using knowledge of the dynamics and mechanical design obtained through simulation and experimentation. However, the dynamics are so complex that the list is augmented with hazards that are revealed by studying accident videos posted on the Internet. The severity of the hazards is estimated using an energy-based measurement of the hazard onset conditions as well as compounding factors from the mechanical design. In addition, experimental and simulation results of sample hazard conditions illustrate their danger and severity. The analysis reveals that inverted-pendulum human transporters have several hazards with unacceptable risk.

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Fig. 1

Two-wheeled inverted-pendulum human transporters: (a) Segway i167, (b) Segway i2, and (c) Ninebot personal transporter

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Fig. 2

Schematic diagram of an inverted-pendulum human transporter

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Fig. 3

Hazard analysis flowchart

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Fig. 4

Segway roll instability

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Fig. 5

Segway forward speed, yaw rate, and base roll angle during a roll-unstable turn [24]. (a) Forward speed, (b) yaw rate, and (c) base roll angle

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Fig. 6

Segway speed and orientation during a single-wheel obstacle collision [24]. (a) Segway speeds and (b) Segway orientation angles

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Fig. 7

Segway i167 twist-steering grip

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Fig. 8

Segway angular response due to unexpected steering-grip twist when leaning forward [24]

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Fig. 9

Segway yaw rate response with right wheel slip on a medium-friction surface [24]

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Fig. 10

Segway right wheel blocking rider’s foot

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Fig. 11

Rider’s feet trapped by wheel

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Fig. 12

Segway moving without a rider in balance mode

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Fig. 13

Segway handlebar blocking rider’s arm

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Fig. 14

Rider in a seated position on the Segway base

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Fig. 15

One wheel of a transporter colliding with an obstacle. (a) Transporter traveling toward an obstacle. (b) Transporter turns toward obstacle, while the rider’s momentum carries him forward.

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Fig. 16

Total energy of rider versus speed

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Fig. 17

Total energy of rider versus additional fall height when traveling at 5.59 m/s (12.5 mph)

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Fig. 18

Total energy of rider as a function of speed and additional fall height




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