Observer-Based Disturbance Control for Small-Scale Collaborative Robotics

Collaborative robotics allows merging the best capabilities of humans and robots to perform complex tasks. This allows the user to interact with remote and directly inaccessible environments such as the micro-scale world. This interaction is made possible by the bidirectional exchange of information (displacement - force) between the user and the environment through a haptic interface. The effectiveness of the human/robot interaction is highly dependent on how the human feels the forces. This is a key point to enable humans to make the right decisions in a collaborative task. This paper discusses the design of a dynamic observer to estimate the forces applied by a human operator on a class of parallel pantograph-type haptic interfaces used to control small-scale robotic systems. The objective is to reject disturbances in order to improve the human force perception capability over a wide frequency range. A dynamic pantograph model is proposed and experimentally validated. The observer is designed on the basis of the proposed dynamic model and its efficiency in estimating the applied human force is demonstrated for the first time with pantograph-type interfaces. Experimental validation first shows the effectiveness of the perturbation observer for external human force estimation with a response time of less than 0.2 s and a mean error of less than 7 mN and then the effectiveness of the controller in improving the quality of human sensation of forces down to 10 mN.