Tri-Axis Receiver for Wireless Micro-Power Transmission

An innovative tri-axes micro-power receiver is proposed. The tri-axes micro-power receiver consists of two sets 3-D micro-solenoids and one set planar micro-coils in which iron core is embedded. The three sets of micro-coils are designed to be orthogonal to each other. Therefore, no matter which direction the flux is present along, the magnetic energy can be harvested and transformed into electric power. Not only dead space of receiving power is mostly reduced, but also transformation efficiency of electromagnetic energy to electric power can be efficiently raised. By employing commercial software, Ansoft Maxwell, the preliminary simulation results verify that the proposed micro-power receiver can efficiently pick up the energy transmitted by magnetic power source. As to the fabrication process, the isotropic etching technique is employed to micro-machine the inverse-trapezoid fillister so that the copper wire can be successfully electroplated. The adhesion between micro-coils and fillister is much enhanced

Active Controller Design for Microgravity Isolation Systems

This paper examines the performance of active isolation systems for microgravity space experiments as a function of desired transmissibilities that are chosen to be either much below or close to what can be tolerated. The control system utilizes two feedback signals: absolute acceleration and relative displacement of the controlled mass. The controller transfer function for acceleration feedback is chosen to avoid marginally stable pole-zero cancellations. The controller transfer function for relative displacement feedback is determined to achieve the desired transmissibility function. The issue of stability and properness of this controller transfer function are discussed. The required input forces and equivalent closed-loop stiffness are examined for various examples of desired transmissibilities

Complementary Cooperation of Dual Power Circuits to Drive Active Magnetic Bearings

A compact-design hybrid power amplifier for AMB (active magnetic bearing) units, named as dual cooperative drive circuit (DC2), is designed and verified by intensive experiments. DC2 can operate under dual mode: either digital driving mode (DDM) or analog driving mode (ADM). By taking advantages of the complementary cooperation between DDM and ADM, the proposed DC2 manifests its superiorities mainly in three aspects: (i) Compared to a traditional 2-level PWM (pulse width modulation) drive circuit, the improvement degree of reducing the amplitudes of current ripples is up to 62%. (ii) By taking advantages of mutually complementary cooperation between DDM and ADM, the steady-state errors of output current, which is exerted to the coils of AMBs, can be much reduced by DC2. (iii) DC2 can provide a high-current slew rate so that the response of AMBs is fast and quick enough to regulate the high-speed rotor back to the neutral position within a very short time period below 0.40 ms. In addition, the proposed DC2 is particularly suitable to be compliant with digital controllers and DSPs (digital signal processors) since the commands or drive sequences are all in DC (direct current) manner

Sandwiched Magnetic Coupler for Adjustable Gear Ratio

An innovative design of a magnetic coupler for shaft speed amplification is proposed and verified by experiments. The structure of the proposed magnetic coupler is similar to an infinite-stage gearbox. In addition, the mathematical model of flux density is derived to look into the equation of adjustable gear ratio and effect of speed amplification. Moreover, two sets of experiments, namely verification of gear ratio and observation of stall phenomenon, are built up to examine the capabilities and drawbacks of the proposed variable-gear-ratio magnetic coupler. Three types of gear ratios are presented by theoretical analysis at first and then examined by experiments. The gear ratios for these three specific types between the input and output rotors are 4.75, 5.75 and 10.5, respectively. That is, the rotational speed of the output rotor can be precisely and realistically amplified. Besides, in order to reduce the torque inertia of the outer rotor, a ferrite bush is inserted to the inner side of the core rotor to decrease the flux density in the air gap. On the other hand, the overlapped depth of permanent magnets, which are attached onto the inner rotor and outer rotor, has to be appropriately chosen. The smaller the overlapped depth, the weaker is the magnetic attractive force in the air gap. As long as these two modifications (an inserted ferrite bush and the aforesaid overlapped depth) are validated, the torque inertia of the outer rotor can be significantly reduced. Accordingly, the required power to rotate the outer rotor can be greatly reduced if the overlapped depth is shortened. However, insufficient overlapped depth between the high-speed rotor and low-speed rotor will bring about a stall phenomenon caused by the magnetic attractive force between the high-speed rotor and the low-speed rotor being weaker than the start-up torque inertia. In other words, the reduced overlapped depth can also reduce the start-up torque inertia but stall phenomenon may easily occur

Dual Cooperative Drive Circuit for Active Magnetic Bearings

A Dual Cooperative Drive Circuit (DC2) for Active Magnetic Bearing (AMB) units is proposed by this work. DC2 operates in dual modes: Digital Driving Mode (DDM) and Analog Driving Mode (ADM). The proposed DC2 manifests its superiorities in two aspects. (i). Compared to a traditional 2-level PWM (Pulse Width Modulation) drive circuit, the improvement degree of reducing the amplitudes of peak-to-peak current ripples is up to 74%. Reduction of ripples is specially beneficial for AMB units to retain the rotor at steady state, without significant reciprocated fluctuation repeatedly. (ii). DC2 provides high current slew rate so that the response of AMB is fast and quick enough to regulate the rotor back to the desired position within a very short time period. These two advantages by DC2 are fairly pertinent to the problems of rotor position regulation. The proposed DC2 exhibits its satisfactory performance either in computer simulations or realistic experiments