Design And Analysis Of A Rod-Driven Continuum Robot With Variable Stiffness

In recent years,with the development and application of robots,new application scenarios are appearing constantly,so the operational requirements of robots are gradually expanding.For example,in the situations of surgery,deep cavity exploration and post-disaster rescue,robots need to be more adaptable and flexible.The emergence of novel continuum robots meet with the special requirements in these situations exactly,which also promotes the research of continuum robots.However,the continuum robots are also faced with many challenges,for example,how to improve their load capacity is important for the application of continuous robots.Besides,it is necessary to figure out the pattern of motion for the control.In this paper,a continuum robot driven by nickel-titanium alloy rods is proposed.A stiffness regulating mechanism driven by a temperature-controlled shape memory alloy(SMA)spring is used to control the friction between the driving rods and the disks to control the overall stiffness.Based on the analysis and hypothesis of the structural characteristics of the variable stiffness continuum arm,and the geometrical basis of the spatial curve and spatial rod,the configuration of continuum arm is represented by series constant curvature micro-elements,and the generalized coordinates of the continuum arm are established too.Considering the effects of elastic force,gravity,driving force,external load and variable friction force,the static equilibrium equation was established using the principle of virtual work.Combining the static equilibrium equation with the geometric constraint equation,a complete static model can be obtained that can solve two kinds of static problems with two different actuation inputs.Finally,through comparison of the simulations and experiments,it is verified that the model has good applicability to the two kinds of static problems.In addition,the relationship between the circuit current I and the stiffness K can be obtained using this model.The results show that this stiffness regulating method can increase the stiffness of the continuum arm by 5-8 times.The research content of this paper further explores the stiffness regulating method and configuration analysis model of continuum robots,which has some promotions to the theory and application of continuum robots.