Slenderness tuning to adjust and regulate constant force mechanisms (STAR-CFM)

Force regulation and adjustment is a challenge in some applications because it requires sensor-controller feedback loops resulting in high system complexity, low range of adjustability, and poor compactness. The objective of this paper is structural control using slenderness tuning to adjust and regulate constant force mechanisms (STAR-CFM) in which the constant force (CF) is regulated passively and adjusted semi-actively. First, a FE parametric study of the baseline CFM with structural imperfections is conducted. Second, a structural control strategy is implemented to adjust the CF value by tuning slenderness using a structural tie. A detailed optimization is conducted to provide the maximum change in the CF under the defined constraints. The proposed methodology provides a CFM with a high energy similarity index, i.e., S_CF>0.92. Our experimental validation confirms the effectiveness of the proposed structural control approach, achieving a significant adjustment range of the control force (CF) up to four times the baseline value. The STAR-CFM provides a compact design compared to the literature designs with a non-dimensional operational displacement of s = 0.45. The STAR-CFM advancements may minimize the mechanical and control system complexity in many applications.