Design and Analysis of a Rolling Joint Based on Gear Tooth for Continuum Robots

Continuum robots can work in narrow and complicated space well because they are more flexible and more adaptable. The joint of the continuum robot is an important factor affecting its performance. However, it is difficult for existing joints to reconcile between load capacity and flexibility. Besides, they also suffer from complex assembly and big friction. This paper presents a rolling joint for continuum robots that has one gear tooth and one tooth space in each rolling elements. The curvature diameter of the rolling elements is equal to the reference diameter of the gear and the centers of the two circles coincide. The joint can rotate with no slip and small friction. The use of just one gear tooth solves the misalign of the gear teeth. In addition, it also has the advantages of simple assembly, large axial bearing capacity and strong torsional stiffness. The kinematics and statics model of the joint was established based on homogeneous transformation and Hertz Formula, respectively. The results of simulations and tests show that the rolling joint made of structural steel can at least bear the axial load of 1000 N and the torsion load of 3 N center dot m, the gear tooth can ensure the two rolling elements rotate without slip, and the torsional stiffness of the continuum robot can be strengthened and stabilized because of the gear teeth in its joints.