On the stability of maxwell model based impedance control and cartesian admittance control implementation

Compliance plays an important role in safe and dependable robots operating in close proximity to human and even directly interact with them in a wide range of domains including industrial and domestic usage. Typical impedance control is a popular complaint control methodology in robotic research community, which imposes a desired dynamic behavior described by a mass-spring-damper system connected in parallel, namely Vogit model. However, if the connection between spring and damper is altered into series manner, namely Maxwell model, a totally different compliance and plastic deformation behavior can be produced. In this paper, stability property of the proposed Maxwell model based impedance controller is studied firstly and a marginally stable conclusion is drawn. Besides, we extend our previous work and propose a novel Cartesian admittance or position-based impedance control scheme which is more suitable to be implemented in most common position-controlled robots. Experiments on a robot platform KUKA LWR 4+ are carried out to validate our methods. Experimental results show that our methods have a promising application in human robot friendly interaction and collaboration.