Cai Chenxiao

Adaptive impedance control in robotic cell injection system

The time-varying force control in cell injection is a difficult work that suffers from low precision, non-repetition and uncontrollable characteristics, especially when the uncertainties from both the robotic model and the injected cells (uncertain environment position and stiffness) are considered. In this paper, a simple adaptive impedance control method combining an inner-loop impedance controller and an outer-loop trajectory tracking algorithm is proposed to cope with the time-varying compliant force control. The time-delayed joint controller is utilized to compensate for the uncertainties in the robust position controller, and in the inner-loop, previous information of certain system parameters are applied to design the adaptive law. Stability and convergence have also been analyzed and simulation studies are shown to verify the effectiveness of the proposed controllers.

Two new upper bounds of the solution for the continuous algebraic Riccati equation and their application

In this paper, for the solution of the continuous algebraic Riccati equation (CARE), we derived two new upper matrix bounds. Compared with the existing results, the newly obtained bounds are less conservative and more practical, which means that the condition for the existence of the upper bounds derived here is much weaker. The advantage of the results is shown by theoretical analysis and numerical examples. Moreover, in redundant optimal control, when we increase the columns of the input matrix, some sufficient conditions are presented to strictly decrease the largest singular value of the feedback matrix by utilizing these upper bounds. We also give some examples to illustrate the effectiveness of these sufficient conditions.