The paper shows the design of an innovative magneto-rheological fluid brake (MRF brake). The integral brake torque from a conventional MRF brake is not quite large since it commonly adopts a single ring-type electromagnetic pole to produce magnetic flux to change the MRF viscosity. This presented innovative MRF brake features with multiple electromagnetic poles to significantly increase the active chaining areas for MRF, and then increase the brake torque. Because of the special arrangements of pole numbers and directions of magnetic flux for these poles, the active chaining areas of MR fluid and brake force are maximized. The simulation results confirmed the feasibility and ability of this innovative MRF brake. Performance comparison shows that the innovative MRF brake has 118% more torque output than a commercial one.
Conventional gyroscopes are equipped with a single-axis control input, limiting their performance. Although researchers have proposed control algorithms with dual-axis control inputs to improve gyroscope performance, most have verified the control algorithms through numerical simulations because they lacked practical devices with dual-axis control inputs. The aim of this study was to design a piezoelectric gyroscope equipped with a dual-axis control input so that researchers may experimentally verify those control algorithms in future. Designing a piezoelectric gyroscope with a dual-axis control input is more difficult than designing a conventional gyroscope because the control input must be effective over a broad frequency range to compensate for imperfections, and the multiple mode shapes in flexural deformations complicate the relation between flexural deformation and the proof mass position. This study solved these problems by using a lead zirconate titanate (PZT) material, introducing additional electrodes for shielding, developing an optimal electrode pattern, and performing calibrations of undesired couplings. The results indicated that the fabricated device could be operated at 5.5±1 kHz to perform dual-axis actuations and position measurements. The calibration of the fabricated device was completed by system identifications of a new dynamic model including gyroscopic motions, electromechanical coupling, mechanical coupling, electrostatic coupling, and capacitive output impedance. Finally, without the assistance of control algorithms, the “open loop sensitivity” of the fabricated gyroscope was 1.82 μV/deg/s with a nonlinearity of 9.5% full-scale output. This sensitivity is comparable with those of other PZT gyroscopes with single-axis control inputs.
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