Control of a robotic manipulator for catching a falling raw egg to achieve human-robot soft physical interaction

Robotic systems provide support for many areas of human activities such as industry, welfare, nursing, housework, and office work. Human-robot soft physical interaction is crucial for realizing safe support in human living environments. This study considers the soft physical interaction between a robot and an object by presenting a control method of a robotic manipulator that catches a falling raw egg. First, we consider a nonlinear decoupling control of a robotic manipulator. Next, a controller design is presented for catching a falling object with a small impact force. This controller consists of two parts: a position tracking controller that tracks a desired trajectory before contact between the object and the end-effector, and a force controller that is triggered after the contact. We employ a position-based impedance controller so that the entire control system can be constructed as a position-based controller. To achieve good tracking performance and reduce the impact force, a discrete-time adaptive two-degree of freedom controller is employed, which considers disturbances such as friction. Experimental results demonstrate the effectiveness of the proposed approach.