Suppression of high-frequency disturbance to satellite by Vernier-gimballing magnetically suspended flywheel

The high-frequency disturbance acting on a satellite decreases the satellite’s stability and pointing precision. The common flywheel is generally used to suppress it, but the number of the required flywheels is usually five or more and that will make the satellite overweight. The magnetically suspended flywheel (MSFW) with Vernier-gimballing capability (Vernier-gimballing MSFW) is proposed in this paper to suppress the high-frequency disturbance. In addition, a comparative simulation research has been done for a satellite controlled by Vernier-gimballing MSFW or reaction FW. It is worth noting that the Vernier-gimbaling MSFW can not only make the actual angle of the satellite track its reference angle better, but also make the accumulative errors of outer and inner virtual gimbal angle be very small, then the satellite’s stability and pointing precision will be improved accordingly. The Vernier-gimballing MSFW is verified to be able to suppress the high-frequency disturbance effectively when their frequencies are within the frequency bandwidth of MSFW.

Office-Cycling: A Promising Way to Raise Pain Thresholds and Increase Metabolism with Minimal Compromising of Work Performance

Aim.Establishing the effects of low intensity cycling (LC), moderate intensity cycling (MC), and standing at a simulated office workstation on pain modulation, work performance, and metabolic expenditure.Methods.36 healthy adults (21 females), mean age 26.8 (SD 7.6) years, partook in this randomized3×3crossover trial with 75 minutes of LC on 20% of maximum aerobic power (MAP) output, 30 minutes of MC on 50% of MAP, and standing 30 minutes with 48-hour wash-out periods. Outcome measures were pain modulation (pressure pain threshold (PPT) and thermal pain threshold)), work performance (transcription, mouse pointing, and cognitive performance), and metabolic expenditure.Results.PPTs increased in all conditions. PPT trapezius showed the highest increase after LC, 39.3 kilopascals (kPa) (15.6; 78.6), compared to MC, 17.0 kPa (2.8; 49.9), and standing, 16.8 kPa (−5.6; 39.4),p=0.015. Transcription was reduced during LC and MC. Mouse pointing precision was best during standing and worst and slowest during MC. Cognitive performance did not differ between conditions. Metabolic expenditure rates were 1.4 (1.3; 1.7), 3.3 (2.3; 3.7), and 7.5 (5.8; 8.7) kcal/minute during standing, LC, and MC, respectively(p<0.001).Conclusions.LC seems to be the preferred option; it raised PPTs, more than doubled metabolic expenditure, whilst minimally influencing work performance.

Identification for Active Vibration Control of Flexible Structure Based on Prony Algorithm

Flexible structures have been widely used in many fields due to the advantages of light quality, small damping, and strong flexibility. However, flexible structures exhibit the vibration in the process of manipulation, which reduces the pointing precision of the system and causes fatigue of the machine. So, this paper focuses on the identification method for active vibration control of flexible structure. The modal parameters and transfer function of the system are identified from the step response signal based on Prony algorithm, while the vibration is attenuated by using the input shaping technique designed according to the parameters identified from the Prony algorithm. Eventually, the proposed approach is applied to the most common flexible structure, a piezoelectric cantilever beam actuated by Macro Fiber Composite (MFC). The experimental results demonstrate that the Prony algorithm is very effective and accurate on the dynamic modeling of flexible structure and input shaper could significantly reduce the vibration and improve the response speed of system.

Servo Controller Application and Design in ATP System

With the rapid development of computer technology, it is widely used in the control field, including advanced alarm plane,cruise missile,radar,O-E theodolite,etc. The increasing complex and real-time arithmetic was applied in the ATP(Acquire Tracking Pointing) system of the control system for boosting the track、captring and pointing precision of O-E(photo-electric) theodolite, so it demanded the servo controller must complete more and more operations in shorter time. While the actual O-E theodolite accomplished the capture and tracking etc. based on PC104 system, so designed the servo control system based on embedded chip as CPU from the practicality, not only decreases the cubage of the system, but also increases the reliability and precision.