Assurance of asymptotic trajectory tracking in robotic manipulators with a continuous control law in the presence of unmodeled dynamics or external disturbance is a challenging problem. Recently, it is asserted that this aim is achieved by designing a traditional model-free controller together with time delay estimation (TDE) such that neither dynamical parameters nor conservative assumptions on the external disturbance are required. In this note, the purpose is to show that this claim is wrong. Additionally, modification of this method for some special cases is presented.

翻译：最近,有人断言,通过设计传统的无模型控制器,加上时间延迟估计(TDE),既不需要动态参数,也不需要关于外部干扰的保守假设,从而实现这一目标。本说明的目的是要表明这一说法是错误的。此外,还对某些特殊情况提出了修改这一方法的建议。