Design and optimization of a magnetorheological damper based on B-spline curves

Taking advantage of the magnetically controllable rheological properties of magnetorheological (MR) fluid, MR dampers are widely used in many engineering fields. Much effort has been made to improve the performance of MR dampers. Structural optimization is one of the popular methods to effectively improve the performance parameters of MR dampers. Most MR damper optimizations are focused on parts with regular shape, but shapes governed by equations can bring out more possibilities and further optimal results. Therefore, in this paper, a new MR damper is designed and optimized based on B-spline curves in order to maximize the controllable output damping force while saving the input power for the prosthetic knee. First, design principle of dividing the parts of the MR damper into two categories is introduced. Then, B-spline curves are used to form the piston shape, which is one of the crucial parts inside the magnetic circuit. Later, the optimal B-spline curve and other geometric parameters inside the magnetic circuit are obtained through simulation and optimization. Furthermore, the optimized MR damper is fabricated, assembled and tested. Finally, the proposed MR damper is compared with the ones in our previous work. Experimental results match well with the simulation ones. When working at the frequency of 1.0 Hz and the amplitude of 10 mm, the proposed MR damper has large maximum damping force and dynamic ratio, with acceptable equivalent damping. The proposed MR damper also performs better than the prototypes in our previous work in terms of maximum damping force, field dependent force, equivalent damping, dynamic range, and force-to-power ratio.