Active Anomalous Transmission and Its Application in Compensating Waveform Distortions

In theoty, engineered anomalous transmission in passive materials and waveguide devices can be used to compensate for wavetorm distortions. However, they suffer from inherent dissipation. Recently, active non-Foster elements with imaginary immittance monotonically decreasing with frequency have shown important potentials in broadening bandwidths of electromagnetic devices. So far, they are implemented besed on negative impedance convertors （NICs） loaded with Foster devices. This makes them intrinsically one-port elements and thus cannot be used to compensate for distortions of signals. We construct a two-port network with a non-Foster transmission coefticient based on an unconventional use of NICs. Simulation and experiments show that it can compensate for extremely distorted signals. The proposed method can be used to broaden existing applications in different areas such as antennas, circuits and systems, and physical-layer signal processing.

Rotor Position Estimation for Single-and Dual-Three-Phase Permanent Magnet Synchronous Machines Based on Third Harmonic Back-EMF under Imbalanced Situation

In this paper,an improved rotor position estimation strategy based on third harmonic back-EMF for single-and dual-three-phase permanent magnet synchronous machines(PMSMs)under imbalanced situation is proposed.Due to the imbalanced machine impedance,back-EMF or sensing resistor network,the measured triplen harmonic back-EMF will contain certain fundamental component distortion which may severely deteriorate the performance of rotor position estimation.With the aid of the fundamental component compensator,this distortion can be significantly compensated,and the rotor position estimation error can be minimized considerably.The proposed strategy has been implemented on a dSPACE platform with a prototype of dual-three-phase PMSM with serious imbalanced parameters,and operate at single-and dual-three-phase conditions.The experimental results prove that the proposed strategy can significantly improve the steady-state and dynamic performance of rotor position estimation under imbalanced situation.

Hardware-in-the-loop simulation for the contact dynamic process of flying objects in space

In the one-gravity environment on the ground, the simulation of the contact process of two flying objects in the zero-gravity environment of space has been a challenging issue since humans first explored space by flying objects. Hardware-in-the-loop （HIL） simulation is an important and effective method to test the usability, reliability, and safety of real docking mechanisms in space. There are four main issues for HIL simulation systems： Design of simulators capable of high frequency response, high motion precision, high velocity, and rapid acceleration; compensation for simulation distortion; design of a control model for the HIL simulation process; and experimental verification. Here, we propose a novel HIL simulator system with a 6-DOF 3-3 perpendicular parallel mechanism and a 3-DOF 3-PRS parallel mechanism; discover the principle of simulation distortion; present distortion compensation models for the force measurement system, dynamic response, and structural dynamics of the simulator; and provide a control model for the HIL simulation process. Two kinds of experiments were performed on the pas- sive-undamped elastic rod and the docking mechanisms to test their performances and to verify the effectiveness and usability of the HIL simulator. The HIL simulation system proposed in this paper is useful for developing space docking, berthing, refu- eling, repairing, upgrading, transporting, and rescuing technologies.