| A new type of wheel-leg hybrid mobile robot driven by line gear reducers was proposed in this dissertation.A novel line gear reducer was adopted in the transmission system.Line gear is a novel gear mechanism via point contact meshing,with the characteristics of compact space and large transmission ratio.The line gear reducers can reduce the size and weight of the mobile platform.The mobile platform is equipped with self-locking transformable wheels.As a wheel-leg hybrid mechanism,the mobile platform is capable of coping with the obstacles and moving smoothly in different terrain environments.This dissertation mainly focuses on the following three sections:Firstly,a design methodology for coplanar axes line gear with controllable sliding was proposed.The line gear pair designed by the methodology is capable of achieving forward-reverse transmission without backlash.Line gear pair is a novel transmission mechanism via a couple of spatial conjugate curves,including driving contact curve and driven contact curve.In this dissertation,the driving contact curve of the coplanar axes line gear pair was extended from a circular helix to a conic helix with variable cone angle,and the driven contact curve was subsequently obtained based on the space curve meshing theory.The studying of the selection criteria of the parameters based on the sliding rate of the line gear pair is finished,which provides the basis for the lubrication design of the line gear.A new type of line tooth,of which two contact curves lie on each side,was proposed for forward-reverse transmission without backlash.The tooth surface is formed by a normal tooth profile moving along contact curve and tooth thickness auxiliary curve.The formulae of the contact curves,tooth thickness auxiliary curves and spatial cylindrical tooth surfaces of the new type of line tooth are derived,which theoretically provides a foundation for standardized production of line gear pair in industry.The calculation example of the line gear pairs shows that the sliding rate can be effectively controlled by using a conic helix as driving contact curve.The result of kinematics experiment shows that the line gear pair designed by the methodology could be capable of achieving forward-reverse transmission without backlash and with controllable sliding rate.Secondly,a design methodology for a kind of self-locking transformable wheel mechanism and its mobile platform was presented.The transformable wheel is a kind of wheel-leg hybrid mechanism,of which the geometrical structure can be adjusted stepless.It is capable of running smoothly and quickly on the stairs with different structural dimensions and coping with the obstacles in different terrain environments.According to the analytic geometry,the design concept of the transformable wheel was put forward,and the obstacle surmounting ability of mobile platform was analyzed.The dynamic differential equation of the mobile platform was established by using the Lagrangian mechanics,and the dynamic characteristics were analyzed by using the commercial software MSC ADAMS,and the driving force of the actuation system is calculated.Thirdly,the wheel-leg hybrid mobile robot driven by line gear reducers was designed.After the comprehensive analysis of the size and transmission power of the mobile robot transmission system,an orthogonal axes line gear reducer with better bearing capacity in unit volume is adopted.According to the differential geometry,the surface features of the tooth surface were studied,and the force conditions of the line gear pairs were deduced,so that the theoretical basis of the shaft design and selection of the bearings was established.The finite element simulation software was used to study the contact stress distribution of the line gear pair.Finally,the experiment of the wheel-leg hybrid mobile robot was carried out.The experimental results show that wheel-leg hybrid mobile robot driven by line gear reducers has better carrying capacity and obstacle surmounting ability. |
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