Non-Fixed Contact Manipulation Control Framework for Deformable Objects with Active Contact Adjustment

The assumption of fixed contact between robots and deformable objects (DOs) is widely used by previous DO manipulation (DOM) studies. However, the fixed contact setting is inapplicable to many real-life applications due to various factors, such as the end-effector's type and the DO's intrinsic material properties. In such cases, the non-fixed contact (NFC) configuration, which has not been well-investigated, usually demonstrates better applicability in terms of contact flexibility and payload capacity. In this letter, we investigate the problem of DOM with NFC, particularly the contact condition characterization and active contact adjustment strategy. To this end, we propose a versatile index and an optimization-based method for the contact description and adjustment. Then a systematic control framework combining both deformation control and active contact adjustment control is proposed for task-level DOM control. The feasibility and effectiveness of the proposed method were verified via the presented experiments.