Collaborative robots, or cobots, are required to maintain compliant interaction while delivering rapid response performance when subjected to sudden, strong forces, such as during impact riveting, resistance spot welding, or precision shaft-hole assembly. This makes low-damping, high-stiffness impedance control critical for the reliable execution of these tasks.
Traditional impedance control methods, however, are plagued by considerable force-tracking errors caused by model uncertainties and external disturbances, which can lead to system instability and thus limit their practical deployment in industrial settings.
To tackle this longstanding challenge, a research team from the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences (CAS), in collaboration with researchers from the University of Liverpool, has developed an adaptive jerk control (AJC) method based on a biased sliding surface (BSS) design.
Their findings were recently published in IEEE Transactions on Industrial Electronics.
The research team first constructed a biased sliding surface to real-time characterize the dynamic variations of the force-position coupling characteristics in cobot systems. This design allows the system to accurately estimate force offset errors even under low-damping impedance operating conditions.
An adaptive jerk controller was subsequently designed to achieve exponential attenuation of such force offset errors. Beyond this, the newly proposed control framework significantly expands the stable selection range of impedance parameters, enabling cobots to realize high-stiffness and low-damping compliant interaction performance.
Experimental validations have confirmed the effectiveness of the proposed method, demonstrating notable improvements in force-tracking accuracy and contact stability compared to existing technologies.
The study shows potential in advancing cobot applications in high-end manufacturing and delivering more stable and precise force-control solutions for humanrobot collaboration.
This work was supported by the National Natural Science Foundation of China, and the Zhejiang Provincial Natural Science Foundation Major Project, among other sources.
Framework of the proposed low-damping impedance control method for collaborative robots. (Image by NIMTE)
