英文文献：Dynamic Gravity Cancellation and Regulation Control in Robots with Flexible Transmissions: Constant, Nonlinear, and Variable Stiffness-柔性传动机器人的动态重力抵消和调节控制:恒定、非线性和可变刚度
英文文献作者：Alessandro De Luca,Fabrizio Flacco
英文文献摘要：
We consider the problem of perfect cancellation of gravity effects in the dynamics of robot manipulators having flexible transmissions at the joints. Based on the feedback equivalence principle, we aim at designing feedback control laws that let the system outputs behave as those of the same robot device when gravity is absent. The cases of constant stiffness (elastic joints), nonlinear flexible, and variable nonlinear flexible transmissions with antagonistic actuation are analyzed. As a particular case, antagonistic actuation with transmissions having constant but different stiffness is also considered. In all these situations, viable solutions are obtained either in closed algebraic form or by a simple numerical technique. The compensated system can then be controlled without taking into account the gravity bias, which is particularly relevant for safe physical human-robot interaction tasks where such compliant manipulators are commonly used. Moreover, dynamic gravity cancellation allows to design new PD-type regulation controllers and to show their global asymptotic stability without the need of any positive lower bound neither on the stiffness nor on the proportional control gain. A Lyapunov-based proof is provided for the case of robots with elastic joints. Simulation results are reported to illustrate the obtained performance in the various robotic systems with flexible transmissions.

研究了关节处具有柔性传动的机械臂动力学中重力效应的完全消除问题。基于反馈等价原理，设计反馈控制律，使系统输出在无重力情况下表现为同一机器人装置的输出。分析了常刚度(弹性关节)、非线性挠性和对抗驱动的变非线性挠性传动的情况。作为一个特殊的情况，对抗驱动的变速箱具有常数但不同的刚度也被考虑。在所有这些情况下，可行的解要么以封闭代数形式，要么通过一个简单的数值技术获得。补偿后的系统可以在不考虑重力偏差的情况下进行控制，重力偏差尤其适用于安全的人机交互任务，在这些任务中，这种顺从的机械手是常用的。此外，动态重力抵消允许设计新的pd型调节控制器，并显示其全局渐近稳定性，而不需要任何正的下界刚度或比例控制增益。针对具有弹性关节的机器人，给出了基于李亚普诺夫的证明。仿真结果表明，所获得的性能在各种机器人系统的柔性传输。