Haptic Rendering Algorithm for Manipulating Tiny Objects Attached on Adhesive Surface of Rigid Objects

Abstract

Manipulating tiny objects adsorbed onto irregular objects is a typical simulation application, such as adjusting brackets in orthodontic training. The operator firstly places the bracket on tooth surface covered with adhesive, and then adjusts its posture with probe. There are two challenges in realizing the above simulation scenes with force feedback. Firstly, the tiny object can be affected by multiple forces when manipulating it, making it difficult to build the dynamic model. Secondly, interaction among the tool, the tiny object and the supporting object is complicated. In addition to embedding between the tool and the objects, embedding between the objects should also be avoided. In our previous work we constructed an orthodontic simulation system with force feedback. However, the haptic operation of adjusting brackets was not ideal, as serious penetration and motion chaos often occurred. In this paper, we analyzed various forces in the process of adjusting the bracket with probe to refine the dynamic model, and introduced viscous force to erase motion chaos to accurately control the bracket’s motion. In addition, we optimized the bracket’s posture through the shape matching constraint to ensure that the bracket can closely contact the tooth surface without embedding into it. The subjective assessment and objective assessment were implemented to validate the system. The experimental results indicated that the system allowed to precisely move the tiny object while maintaining its close contact with the supporting object.