Simplified approach for prediction of spread,roll load and torque in grooveless rolling of billets

Abstract

A simplified analytical approach has been developed to predict the spread, roll load and torque in the grooveless rolling of billets under various conditions of billet aspect ratio, height reduction ratio, friction coefficient and roll radius. The results obtained from the simplified analytical model are shown to be in fair agreement with those obtained from three-dimensional finite element simulation under the same conditions. The main merit of the proposed simplified analytical approach, as compared with three-dimensional finite element simulation, lies in the drastic reduction of computational time required in finite element simulation, which favours the effective use of such a simplified approach to design the rolling schedule and apply online control of grooveless rolling.     

Torque distribution using a weighted pseudoinverse in a redundantly actuated mechanism

When mobility, the number of independent variables to describe system motion exactly, is greater than the degree-of-freedom of task space, the system is called a kinematically redundant system. On the other hand, redundant actuation indicates a situation when there are more actuators than a system's mobility. Redundant actuation yields many advantages. First, actuation redundancy can increase the force, velocity and acceleration of an end-effector. Second, if some actuators are out of order, the system can still work well. This fault-tolerant capability is useful for remote control robots in space or nuclear plants. Impulsive force can decrease when modulating arbitrary stiffness without feedback control. The performance of a system can be improved by optimizing redundancy. However, there are some issues of economic efficiency and minimization of a system, because redundant actuation may involve more actuators than non-redundant actuation. In addition, there are infinite torque sets of motors for the same task. We used a weighted pseudoinverse matrix for torque distribution. To reduce the maximum torque, we suggested the use of the minimum norm torque as the weighting values. This method allows for smaller motor capacity, and can contribute to economic efficiency and minimization of a system.