In laparoscopic surgeries, robotic systems commonly use trocar fixation to achieve remote center motion (RCM). However, this fixation occupies the surgeon's operational space and limits surgical flexibility. It is essential to ensure adequate workspace while maintaining RCM to enhance procedural efficiency and safety. This paper introduces a novel approach to preserve RCM without relying on trocar fixation. The proposed method integrates a six-degree-of-freedom robotic arm with a dual end-effector system, employing tool coordinate storage and remote center point definition to achieve precise four- degree-of-freedom RCM motion control. To validate this method, an experimental setup with an optical tracking system was utilized to measure and calibrate the remote center position. The results indicate that the robot maintained RCM with mean positional errors of 0.672, 0.318, and 0.704 mm along the x, y, and z axes, respectively, yielding a three-dimensional mean error of 1.136 mm. These findings demonstrate the effectiveness of the method in maintaining RCM while maximizing surgical workspace and operational flexibility.

In this paper, we introduce a recently built screwing robotic system for the bolt assembly of elastic steel plates. The screwing robotic system consists of two vision cameras (having narrow and wide fields of view), a collaborative robot with a 10 kg payload, and a motorized screw drill with a pneumatic bolt supplier. Due to the elasticity of the steel plates, they tend to statically deform and dynamically vibrate during tasks under the conventional setting of automatic screwing, often resulting in screw failures. Thus, we designed a compliant connector device to be attached between the robot end-effector and screw drill that can absorb vibration and shock during the bolt assembly to improve the screwing quality and success rate of the bolt assembly. Upon adopting this screwing robotic system with the compliant connector, the success rate of the bolt assembly was improved from 56% to 100%.