Hirose Fukushima Lab


Expandable Three-Wheeled Rover "Tri-Star II"	BACK TO PLANETARY EXPLORATION ROBOT

Movie.1 Mechanics

Movie.2 Step Climbing

(1995-) At present, many companies are planning to launch unmanned robot rover vehicles for planetary exploration. We are developing Tri-Star II (as shown in Fig.1) as a joint research project with NASDA, Japanese NASA. Tri-Star II has three wheels that are eccentrically supported by vertical rods (shown in Fig.2) and can perform several functions, such as, expansion from housed to expanded posture (shown inFig.3), Omni-directional steering motion, and avoids being trapped on sandy ground. These functions can be achieved by the cooperative drive of active wheels and latches, in order to fix and release the wheel rotation around vertical eccentric rod, and of the sliding motion of the inclined slide arm. The expansion is also aided (as shown in Fig.4) with the synchronized up motion of the hoist. Tri-Star II’s wheels (shown in Fig.5) are composed of stainless steel leaf springs and are able to expand three times in volume.

Tri-Star II has three wheels to maintain static stability, but these wheels also provide adaptability to rougher terrain when expanded (shown in Fig.6). The steering motion of the Tri-Star II is performed in three steps i)　set free the wheels to rotate around the vertical axis, ii) drive the wheels to change their orientation, iii) lock the wheels and rotate them around the vertical axis and go forward.　The motion of the wheels around vertical axis is also useful for escape when the wheel digs into a hole. Fig.1 is the demonstration of Tri-Star II on the beaches of Santa Monica in January of 1997

Fig.1 Tri-Star II

Fig.2 Tri-Star II has 3 Wheels

Fig.3 Housing Mode

Fig.4 Expansion Sequence of Tri-Star II

Fig.5 Tri-Star II's wheel

References:

Shigeo Hirose, Naritoshi Ootsukasa, Takaya Shirasu, Hiroyuki Kuwahara, and Kan Yoneda : Fundamental Considerations for the Design of a Planetary Rover, Proc. ICRA, Nagoya, pp.1939-1944 (1995)
Shigeo Hirose, Hiroyuki Kuwahara, Yasufumi Wakabayashi, Nobuto Yoshioka : Mobility and Remote Control Schemes of an Offset-Wheel Rover Vehicle, Proc. Int. Conf. On Mobile Planetary Robots & Rover Roundup, pp. (1997)
Shigeo Hirose, Hiroyuki Kuwahara, Yasufumi Wakabayashi, Nobuto Yoshioka : The Mobility Design Cocepts/Characteristics & Ground Testing of an Offset-Wheel Rover Vehicle, Proc. Int. Conf. On Mobile Planetary Robots & Rover Roundup, pp.1-14 (1997)