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ABSTRACT
This study introduced a six-legged walking machine with new leg structure, analyzed this walking machine’s mechanism and tripod gait and transmission system. With modeling in PRO/E, we imported the model into ADAMS, simulation results showed the motion curve of the walking machine in three dimensional. Prototype test showed the walking machine’s straight walking capacity and provided a basis for improvement. The results of test proved the design’s rationality and revealed some problems need to be optimized, such as leg stuck even machine’s body sink. This design showed a valuable way in walking machine’s walking mechanism.


INTRODUCTION

Walking machines are a sort of robots for which use for translocation legs and the motion of them can be similar to insect or mammal moves (Graca and Zimon, 2009). The structure design of this kind of robots puts great contribution to its environmental adaptability and walking stability on complex and nasty non-structure environment where human’s activities need to be replaced by machine (Wang et al., 2009). It has broad application prospects in many fields, such as mountain transport, satellite detection, disaster relief and rescue, mineral exploitation and military affairs. Currently, many researchers paid attention to the design of multi-legged walking machine, especially six-legged walking machine. Greiner et al. (1996) had developed the ALUVs (autonomous legged underwater vehicles) which has six legs. ALUVs can walk under the water and clear sea mines by self-explosion. Delcomyn and Nelson (2000) designed six-legged biomimetic robot-Biobot. Its movements are driven by pneumatic component, using unique structure to mimic muscle characteristics. Wilcox et al. (2007) provides a robotic vehicle called ATHLETE which uses wheels on six legs. ATHLETE is designed for rough and steep lunar terrain and each limb can perform complex tasks independently. All these walking robots have adopted serial mechanism leg structure, each leg needs 2 or more motors to drive and control the leg attitude, therefore, these robots must apply complex control system and complicated driving system. Because of the complex structure and demanding precision of control (Vitek and Blankenship, 1999; Kriz and Milliner, 2003), walking machine’s reliability and stability are still unable to meet the practical requirements.

This study presents a new type of six-legged walking machine. This six-legged walking machine adopts new structure and the tripod gait, as well as six legs driven by one motor. One unique advantage of this walking machine is that the walking movement can be realized without any complex control system. A second unique advantage is that the center of gravity height jitter of this machine is negligible.

DESIGN OF THE SIX-LEGGED WALKING MACHINE

Design of leg: Leg structure is the core component of multi-legged walking machines which features determine the basic properties of multi-legged walking machine. Leg structure of this walking machine use six linkage (Fig. 1). Crank is the antriebstange, bracing swing around sleeve. When crank fixed to the shaft at one end, page link 3 swings around the joint C and Joint D back and forth, preparing the institution for preliminary leg open and contractile function. When the joint B in the sleeve, joint B subject constraints from sleeve rather than turning, so joint D and joint C hold up the machine body, page link 3 ‘s swing make the body moving forward.

Crank rotating 360° around the drive shaft center completes a operation cycle. In the first 180° of crank rotation, as joint B in the sleeve, page link 1 and 2 is equivalent to an overall, page link 3‘s swing make the body moving forward. In the last 180°of crank rotation, joint B leaves sleeve, goes into rotating pair. Under the action of joint B, C and D and page link 4, 3 lift off the ground, no longer support the body, achieve the movement. This leg structure can convert single rotary motion into leg walking exercise directly and has similar moving gesture with quadruped mammals.

Gait selection: Gait is the process that single leg put up and down according to a certain order and trajectory (Cuiping, 2007). Gait choice should based on the leg structure. Suitable gait is the basis of the walking machine to realize continuous stability walking motion. Currently, most of the six-legged walking machine using tripod gait. Triangle gait refers to three pairs of legs are divided into two groups, with alternating triangular support structure to move forward (Fig. 2a), number 1, 3, 5 legs for a group, No. 2, 4, 6 legs for the other group, thereby formed two triangular brackets.


reference:
http://scialertfulltext/?doi=itj.2014.984.988&org=11