Ralph Jansen

Control of a high-speed flywheel system for energy storage in space applications

A novel control algorithm for the charge and discharge modes of operation of a flywheel energy storage system for space applications is presented. The motor control portion of the algorithm uses sensorless field oriented control with position and speed estimates determined from a signal injection technique at low speeds and a back electromotive force technique at higher speeds. The charge and discharge portion of the algorithm use command feedforward and disturbance decoupling, respectively, to achieve fast response with low gains. Simulation and experimental results are presented demonstrating the successful operation of the flywheel control up to the rated speed of 60 000 r/min.

Design aspects of a high speed permanent magnet synchronous motor / generator for flywheel applications

This paper presents aspects of the design solution for a high speed, high efficiency permanent magnet machine used as a motor/generator (M/G) unit in a flywheel energy storage system. The motor is operated in a vacuum with passive cooling; thus the right choice of permanent magnet properties and ability to withstand demagnetization due to the temperature variation and armature reaction is important for the M/G design. Additionally, the M/G is operated with magnetic bearings so radiation is the only heat transfer method for rotor losses. Because of that, special measures are directed toward reducing the rotor losses. Analytical design results obtained by using a commercial motor design software package are presented. An investigation of the armature reaction and magnet demagnetization is performed using the magnetic circuit method and 2D finite element analysis (FEA). The results of the transient 2D FEA are presented. The value of the axial force applied to the rotor due to the stator slots skew as a function of stator current is determined using 3D FEA simulation. The final design results in good torque performance over the entire operating range

A flywheel energy storage system demonstration for space applications

A novel control algorithm for the charge and discharge modes of operation of a flywheel energy storage system for space applications is presented. The motor control portion of the algorithm uses sensorless field oriented control with position and speed estimates determined from a signal injection technique at low speeds and a back EMF technique at higher speeds. The charge and discharge portion of the algorithm use command feed-forward and disturbance decoupling, respectively, to achieve fast response with low gains. Simulation and experimental results are presented.

Integrated power and attitude control with two flywheels

Energy storage and attitude control are two distinct subsystems of the typical satellite. Energy storage is provided using batteries and active attitude control is accomplished with control moment gyroscopes or reaction wheels. A system mass savings can be achieved if these two subsystems are combined using multiple flywheels for simultaneous kinetic energy storage and momentum transfer. This paper develops, simulates, and experimentally demonstrates the control algorithms to accomplish integrated power and single-axis attitude control using two flywheels.

Stabilizing Gyroscopic Modes in Magnetic-Bearing-Supported Flywheels by Using Cross-Axis Proportional Gains

For magnetic-bearing-supported high-speed rotating machines with significant gyroscopic effects, it is necessary to stabilize forward and backward tilt whirling modes. Instability or low damping of these modes can prevent the attainment of desired shaft speed. We show analytically that both modes can be stabilized by using cross-axis proportional gains and high- and low-pass filters in the magnetic bearing controller. Furthermore, at high shaft speeds, where system phase lags degrade the stability of the forward-whirl mode, a phasor advance of the control signal can partially counteract the phase lag. In some range of high shaft speed, the derivative gain for the tilt modes (essential for stability for slowly rotating shafts) can be removed entirely. We show analytically how the tilt eigenvalues depend on shaft speed and on various controller feedback parameters.

Turboelectric Aircraft Drive Key Performance Parameters and Functional Requirements

The purpose of this paper is to propose specific power and efficiency as the key performance parameters for a turboelectric aircraft power system and investigate their impact on the overall aircraft. Key functional requirements are identified that impact the power system design. Breguet range equations for a base aircraft and a turboelectric aircraft are found. The benefits and costs that may result from the turboelectric system are enumerated. A break-even analysis is conducted to find the minimum allowable electric drive specific power and efficiency that can preserve the range, initial weight, operating empty weight, and payload weight of the base aircraft.

Overview of NASA Electrified Aircraft Propulsion Research for Large Subsonic Transports

NASA is investing in Electrified Aircraft Propulsion (EAP) research as part of the portfolio to improve the fuel efficiency, emissions, and noise levels in commercial transport aircraft. Turboelectric, partially turboelectric, and hybrid electric propulsion systems are the primary EAP configurations being evaluated for regional jet and larger aircraft. The goal is to show that one or more viable EAP concepts exist for narrow-body aircraft and mature tall-pole technologies related to those concepts. A summary of the aircraft system studies, technology development, and facility development is provided. The leading concept for midterm (2035) introduction of EAP for a single-aisle aircraft is a tube and wing, partially turboelectric configuration NASA Single-Aisle Turboelectric Aircraft With Aft Boundary Layer (STARC– ABL); however, other viable configurations exist. Investments are being made to raise the technology readiness level of lightweight, high-efficiency motors, generators, and electrical power distribution systems as well as to define the optimal turbine and boundary-layer ingestion systems for a midterm tube and wing configuration. An electric aircraft power system test facility (NASA Electric Aircraft Testbed (NEAT)) is under construction at NASA Glenn Research Center and an electric aircraft control system test facility (Hybrid Electric Integrated System Testbed (HEIST)) is under construction at NASA Armstrong Flight Research Center. The correct building blocks are in place to have a viable large-plane EAP configuration tested by 2025 leading to entry into service in 2035 if the community chooses to pursue that goal.

Bearingless Five-Axis Rotor Levitation with Two Pole Pair Separated Conical Motors

In some high performance applications, such as high speed rotating machinery, systems where access for maintenance is limited, or operating environments with extreme temperatures and pressures, motors without mechanical bearings would be preferred. This paper presents the theory, simulation, and lab results of a new type of fully magnetically levitated bearingless motor. The motors are wound without internally connecting the pole pairs, and force is controlled by varying rotor reference frame d-axis current to each pole pair. This in turn raises or lowers the flux caused by the permanent magnets, creating a flux imbalance on the periphery of the rotor [1], which in turn creates a net force on the rotor. The conical shape of the motor allows forces to be created in both radial and axial directions, allowing these motors full 5-axis levitation. Index Terms – Bearingless Motor, Conical Motor, 5-axis levitation.

Levitation performance of two opposed permanent magnet pole-pair separated conical bearingless motors

In standard motor applications, rotor suspension with traditional mechanical bearings represents the most economical solution. However, in certain high performance applications, rotor suspension without contacting bearings is either required or highly beneficial. Examples include applications requiring very high speed or extreme environment operation, or with limited access for maintenance. This paper expands upon a novel bearingless motor concept, in which two motors with opposing conical air-gaps are used to achieve full five-axis levitation and rotation of the rotor. Force in this motor is created by deliberately leaving the motors pole-pairs unconnected, which allows the creation of different d-axis flux in each pole pair. This flux imbalance is used to create lateral force. This approach is different than previous bearingless motor designs, which require separate windings for levitation and rotation. This paper examines the predicted and achieved suspension performance of a fully levitated prototype bearingless system.

Stability Limits of a PD Controller for a Flywheel Supported on Rigid Rotor and Magnetic Bearings

Active magnetic bearings are used to provide a long -life, low -loss suspension of a high -speed flywheel rotor . This paper des cribes a modeling effort used to understand the stability boundaries of the PD controller used to control the active magnetic bearings on a high speed test rig . Limits of stability are described in terms of allowable stiffness and damping values which resu lt in stable levitation of the non -rotating rig. Small signal stability limits for the system is defined as a non -growth in vibration amplitude of a small disturbance. A simple mass -force model was analyzed. The force resulting from the magnetic bearing wa s linearized to include negative displacement stiffness and a current stiffness. The current stiffness was then use in a PD controller. The phase lag of the control loop was modeled by a simple time delay. The stability limits and the associated vibration frequencies were measured and compared to the theoretical values. The results show a region on stiffness versus damping plot that have the same qualitative tendencies as experimental measurements . The resulting stability model was then extended to a flywh eel system. The rotor dynamics of the flywheel was modeled using a rigid rotor supported on magnetic bearings. The equations of motion were written for the center of mass and a small angle linearization of the rotations about the center of mass. The stabil ity limits and the associated vibration frequencies were found as a function of non dimensional magnetic bearing stiffness and damping and non dimensional parameters of flywheel speed and time delay.