| Because the conventional rigid driven biped robot does not have the function of slowing down the impact and protecting the mechanism,while the flexible driven biped robot has the advantages of similar human tendon flexibility,can bear large impact load,relatively light and compact,many scholars and research institutions turn to study the flexible driven humanoid biped robot.Flexible driv e mainly includes hydraulic drive,pneumatic artificial muscle drive,rope drive and flexible material drive.The research object of our laboratory is the rope-driven flexible unit,mainly around the rope-driven unit research work.In this paper,based on the rope-driven unit,the mechanics modeling of the wire rope,the kinetics modeling of the rope-driven unit,the impact resistance and its application in the anti impact walking of the biped robot are deeply and systematically studied.The main contents are as follows:In order to meet the needs of kinetics modeling of rope-driven unit,the equivalent mechanics model of wire rope under the condition in straight drawing state is established based on the elastic thin rod theory.Firstly,the geometric model of wire rope is established in the Frenet movable frame,and the stress and deformation parameters of wire rope under the assumed conditions are deduced.According to the improved constitutive relation and material mechanics formula,the equivalent elastic modulus calculation formula of wire rope under the condition in straight drawing state is deduced.Compared with the existing research results,the validity of the model and the accuracy of the theoretical formula are verified;In order to solve the modeling problem of the complex winding of the wire rope in the rope-driven unit,by analyzing the change rule of secondary helix angle of wire rope,a reasonable assumption is put forward.Based on the elastic thin rod theory,the stress analysis of bending multi-strand wire rope is carried out,and the calculation formulas of bending rigidity and equivalent elastic modulus of bending multi-strand wire rope is deduced according to the law of energy conservation.ABAQUS is used to simulate the finite element of bending multi-strand wire rope,and a special measuring device for large deformation deflection of bending wire rope is designed and manufactured for experimental verification.After theoretical calculation,finite element simulation and experimental measurement,and compared with the existing research results,the validity of the model and the accuracy of the theoretical formulas are verified;Based on the above-mentioned equivalent mechanics model of multi-strand wire rope under the condition in straight drawing and bending state,a kinetics modeling method of rope-driven unit for robot joint is proposed,and the general kinetics equation of rope-driven unit is deduced.The impact resistance of rope-driven unit is analyzed from passive and active compliance.Based on the existing tension feedback and postion closed loop of joint controller,the active compliance control is introduced to improve the buffer ability of the rope drive unit to the impact.Taking FDU-II rope-driven unit as an example,a new system kinetics model is established by using this method instead of viscoelastic theory,and the system kinetics equation is obtained by substituting the relevant parameters.The numerical simulation and dynamic simulation of FDU-II unit are carried out by programming software and Adams respectively.The FDU-II rope-driven unit prototype was used to do the joint track test,amplitude frequency characteristics test and the forward and reverse rotation frequent reciprocating test,which verified the validity and accuracy of the kinetics model.In order to obtain the impact resistance of FDU-II rope-driven unit,the passive compliant impact tests of normal preload,reduced preload and the active-passive hybrid compliant impact tests of normal preload were carried out;Based on the above research work,a rigid-flexible hybrid kinetics model of biped robot is established.The off-line walking trajectory samples are generated by using the existing walking sample planning method in the laboratory,and an online trajectory compensation method is proposed to reduce the impact of the robot walking on the ground.The simulation model of biped robot with FDU-II rope-driven unit is established in ADAMS software,and the robot walking simulation is carried out on even ground and uneven ground respectively.The effectiveness of this method is verified by ADAMS/Simulink joint simulation,and the best mitigation effect is 90.32%.In addition,the method can be used to avoid the robot toppling caused by too large impact.The above research content provides a reference index for the design and development of new rope-driven unit and biped robot,and also provides a theoretical basis for the realization of anti impact walking of biped robot. |
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