Research Papers

Analysis and Design of a Passive Steering Mechanism for a Pedaled, Self-Balanced Unicycle

[+] Author and Article Information
Chun-Feng Huang

Department of Power Mechanical Engineering,
National Tsing Hua University,
Hsinchu 30013, Taiwan

Jian-Hao Hong

Department of Power Mechanical Engineering,
National Tsing Hua University,
Hsinchu 30013, Taiwan

T.-J. Yeh

Department of Power Mechanical Engineering,
National Tsing Hua University,
Hsinchu 30013, Taiwan
e-mail: tyeh@pme.nthu.edu.tw

1Corresponding author.

Manuscript received September 16, 2014; final manuscript received May 1, 2015; published online August 18, 2015. Assoc. Editor: Jun Ueda.

J. Mechanisms Robotics 8(1), 011006 (Aug 18, 2015) (10 pages) Paper No: JMR-14-1248; doi: 10.1115/1.4030652 History: Received September 16, 2014

In this paper, a pedaled, self-balanced vehicle named Legway, is developed. The vehicle is structurally similar to a pedaled unicycle but uses a brushless DC (BLDC) hub motor as its main driving wheel. It is intended that the unstable longitudinal dynamics of the vehicle is stabilized by a feedback control system, but the lateral balancing and steering are manually controlled by the rider via a passive steering mechanism. This study is first devoted to the dynamic modeling of the steering mechanism. It is shown from analyzing the model that there is a critical speed beyond which the unicycle becomes open-loop stable in the lateral direction so that the rider can turn the handle to steer the unicycle as the conventional bicycle. The dynamic model is then used for conducting simulations for selecting appropriate design parameters. An experimental prototype is constructed based on the analysis result and the steering performance is experimentally verified.

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Grahic Jump Location
Fig. 3

Definitions of coordinate frames, motion variables, and system parameters

Grahic Jump Location
Fig. 2

Photo and schematics of Legway II

Grahic Jump Location
Fig. 4

Root locus of open loop poles with respect to vehicle speed

Grahic Jump Location
Fig. 7

Experimental response

Grahic Jump Location
Fig. 8

Snapshots of the riding test video

Grahic Jump Location
Fig. 5

Simulated responses

Grahic Jump Location
Fig. 6

Impact of ks and β0 on the steering gain




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