7,593 research outputs found
Synchronous response modelling and control of an annular momentum control device
Research on the synchronous response modelling and control of an advanced Annular Momentun Control Device (AMCD) used to control the attitude of a spacecraft is described. For the flexible rotor AMCD, two sources of synchronous vibrations were identified. One source, which corresponds to the mass unbalance problem of rigid rotors suspended in conventional bearings, is caused by measurement errors of the rotor center of mass position. The other sources of synchronous vibrations is misalignment between the hub and flywheel masses of the AMCD. Four different control algorithms were examined. These were lead-lag compensators that mimic conventional bearing dynamics, tracking notch filters used in the feedback loop, tracking differential-notch filters, and model-based compensators. The tracking differential-notch filters were shown to have a number of advantages over more conventional approaches for both rigid-body rotor applications and flexible rotor applications such as the AMCD. Hardware implementation schemes for the tracking differential-notch filter were investigated. A simple design was developed that can be implemented with analog multipliers and low bandwidth, digital hardware
Robust Indoor Localization with Ranging-IMU Fusion
Indoor wireless ranging localization is a promising approach for low-power
and high-accuracy localization of wearable devices. A primary challenge in this
domain stems from non-line of sight propagation of radio waves. This study
tackles a fundamental issue in wireless ranging: the unpredictability of
real-time multipath determination, especially in challenging conditions such as
when there is no direct line of sight. We achieve this by fusing range
measurements with inertial measurements obtained from a low cost Inertial
Measurement Unit (IMU). For this purpose, we introduce a novel asymmetric noise
model crafted specifically for non-Gaussian multipath disturbances.
Additionally, we present a novel Levenberg-Marquardt (LM)-family trust-region
adaptation of the iSAM2 fusion algorithm, which is optimized for robust
performance for our ranging-IMU fusion problem. We evaluate our solution in a
densely occupied real office environment. Our proposed solution can achieve
temporally consistent localization with an average absolute accuracy of
0.3m in real-world settings. Furthermore, our results indicate that we
can achieve comparable accuracy even with infrequent (1Hz) range measurements
- …