This paper developed a new magnetorheological (MR) prosthetic knee joint using an MR damper as the brake. According to the gait data of healthy people walking on flat ground, the structure of a MR prosthetic knee joint was expounded in detail, and its motion and dynamic model was also established. In addition, an MR damper was developed according to the specific needs of an MR prosthesis. The forward and reverse mechanical models of the MR damper were established, and its damping performance was obtained through experimental tests. In addition, to solve the problems of uncertainty and external interference in the MR prosthetic knee joint system, a second-order sliding mode controller was proposed. The experimental test results show the maximum positive error of the knee joint swing trajectory is 9.4°, which effectively tracks the reference swing trajectory.

A conventional muffler used in vibratory rollers is usually designed based on experience and its performance could be enhanced in a large degree through structure optimization. In order to evaluate performance of reactive muffler and its effect on power loss of engine, flow field of muffler was discussed by CFD comparing with experimental test and the structure of reactive muffler was optimized. Based on results of simulation and optimization, the reactive muffler used in vibratory rollers with weight of 13t was fabricated and its field test was carried on. The simulate results showed that velocity field coincided with the pressure field basically, which indicates that the optimized muffler -2# has excellent aerodynamic characteristics and rational design of damping units. The results of field tests showed that 2# muffler had better acoustic insertion loss with little pressure loss. Acoustic insertion loss was 17~18.4 dB (A) at engine speed of 2450 rpm, which meets the designing goal.

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