Design Theory And Mechanism Of A Micro Legged Robot Driven By Line Gears With Variable Transmission Ratio

A design theory and a mechanism of a novel micro legged robot are proposed in this article. This micro legged robot is composed of a transmission mechanism and a walking mechanism. The transmission mechanism is based on the previous study of line gear, which is also named space curve meshing wheel(SCMW) in the published papers. Line gear is proposed from the meshing theory of spatial conjugate curves, so it could provide a considerable transmission ratio in quite a small scale. Meanwhile, the legged mechanism is made of compliant mechanism, which would contribute to provide a bionic movement trajectory on the foot when it is applied in a walking robot.This article mainly focuses on the following three sections: 1. Deducing the formulae for the line teeth of the line gears with variable transmission ratios. In the scale of micro mechanical system, a requirement of a periodic variable transmission ratio could not always be satisfied by means of microcomputer or non-circular gears. Therefore the formulae of line gears which could provide a periodic variable transmission ratio were developed in this article, which was based on the theory of line gear proposed by Prof. Chen Yangzhi. Then several models of line gear pairs were built and manufactured by 3D printing. Afterwards, experiments were conducted for measuring the transmission ratio. The result indicates that a variable transmission ratio will be feasible if the line gears are produced from the proposed formulae, and the change of the transmission ratio is steady in gear drive.2. Designing a micro leg mechanism based on compliant mechanism. The conventional rigid-body mechanisms are always too complicated to be applied in micro robots. This problem could be solved by compliant mechanism because of its simplicity. Therefore this article takes compliant mechanism to design a leg mechanism that can output a bionic trajectory on a foot. It is designed by means of the pseudo-rigid-body model and verified by computer simulation. The compliant leg mechanism is so simple that it is applicable to small or micro robots, applicable to biped robot or multiped robot. In addition, it is designed as a bistable mechanism, with two stable states named “open state” and “contraction state”, thus making it much more portable.3. Designing a complete mechanical system of a compliant legged robot driven by the mentioned line gears with variable transmission ratio. It is not easy to simulate a gait of an animal only by means of mechanisms, because there are usually requirements of quick return motions. At first, it is tried to design a bionic legged robot with an input from gear drive under the condition of constant transmission ratio, but the mechanism is going to be too complicated to be miniaturized. However, if the gears are replaced by the line gears with variable transmission ratio, the output leg mechanism could be much simpler and capable of miniaturizing. Furthermore, if the mentioned compliant leg mechanism is used to take the place of the conventional rigid-body mechanism as well, the entire legged robot would be simplified most.