Artistic robotic pencil sketching using closed-loop force control

This study introduces an artistic robotic painting system. The main purpose was to use a force sensor combined with a 6-axis robotic arm to create pencil sketches. Compared with other painting robots, our system has additional tactile sensing that can overcome the problem of pencil wear and can simulate the feeling of human sketches. To provide the robot with the capability to create paintings, our experiment used neural style transfer technology to extract the content and style image features and recomposed them into a new artwork. The newly generated image was processed for edge detection and further layered using methods, such as k-means clustering and image grayscale quantisation, resulting in a contour layer and multiple background layers. We carried out path planning of different layers according to the layering result, and we sorted the pixels by finding the shortest distance between them to plan a feasible path for the robotic arm at a higher speed. Finally, in the robotic arm painting experiment, we conducted two types of art creation: Chinese brush painting and pencil sketching. In the first type, we used position control to create a Chinese brush painting, and in the second type, we used a proportional-integral-derivative (PID) controller for force control to create pencil sketching. The experimental results show the validity of the proposed techniques in artistic robotic painting, both in Chinese brush painting and pencil sketching, with painting times of less than 30 min.