Flywheel Spin Research Articles

Motion control studies of a barge mounted offshore dynamic wind turbine using gyrostabilizer

This paper is a sequel to our recently published article “Motion control of a barge for offshore wind turbine (OWT) using gyrostabilizer’, Ocean Eng. 209 (2020). https://doi.org/10.1016/j.oceaneng.2020.107500.The present investigation focuses on the performance of a gyrostabilizer on a barge mounted dynamic Offshore Wind Turbine (OWT) on reducing the angular motions with rotor operating at different speeds through experimental studies. The adjective ‘dynamic’ refers to model wind turbine with rotor that is in motion. To represent the operational scenario, different wind turbine rotor rotating conditions such as below rated power (60 rpm), rated power (85 rpm) and above rated power (114 rpm) were selected. Experiments were conducted in the wave basin with a 1:50 Froude-scaled model of ITI barge supported 5-MW NREL OWT. Forced vibration tests were conducted to evaluate the platform rotations and nacelle response under regular and irregular waves in parked and operating conditions. The platform rotations and nacelle accelerations during roll and pitch DOF for gyrostabilizer ‘off’ and ‘on’ condition with gyro flywheel spin velocity of 5700 rpm were measured and compared to evaluate the motion reduction rates. Using gyrostabilizer, under regular waves, roll/pitch motion reduction by 64/54% for parked, 57/39% for below rated, 67/45% for rated and 64/39% for above rated conditions were obtained. For irregular waves a better reduction of these motions was obtained. By reducing the roll and pitch motions, the nacelle responses are also reduced significantly.

Study on Gear-Driven Gyroscopic Power Generator

To realize a small-sized floating-type wave energy converter, a vibrational power generator that utilizes the gyroscopic effect and a geared acceleration is presented. First, equations of motions of the spin accelerating mechanism are derived. Next, it is shown by the numerical analyses that the spinning velocity of the gyro-flywheel is accelerated by the rotating vibration, a steady-state small vibration with the frequency twice the input frequency exists in the flywheel spin, and the generated power is 10 W at the conditions that the flywheel diameter is 600 mm, the weight is 20 kg, the input frequency is 0.2 Hz and the amplitude is ±10 deg. Finally, an experimental apparatus of the spin accelerating mechanism with a flywheel of φ300 mm is developed to show that the experimental and calculated spin and precession velocities agree well.

Fault diagnosis for satellite sensors and actuators using nonlinear geometric approach and adaptive observers

SummaryThis paper presents a novel scheme for diagnosis of faults affecting sensors that measure the satellite attitude, body angular velocity, flywheel spin rates, and defects in control torques from reaction wheel motors. The proposed methodology uses adaptive observers to provide fault estimates that aid detection, isolation, and estimation of possible actuator and sensor faults. The adaptive observers do not need a priori information about fault internal models. A nonlinear geometric approach is used to avoid that aerodynamic disturbance torques have unwanted influence on the fault estimates. An augmented high‐fidelity spacecraft model is exploited during design and validation to replicate faults. This simulation model includes disturbance torques as experienced in low Earth orbits. This paper includes an analysis to assess robustness properties of the method with respect to parameter uncertainties and disturbances. The results document the efficacy of the suggested methodology.

Mathematical Framework for Hydromechanical Time-Domain Simulation of Wave Energy Converters

Efficient design of wave energy converters based on floating body motion heavily depends on the capacity of the designer to accurately predict the device’s dynamics, which ultimately leads to the power extraction. We present a (quasi-nonlinear) time-domain hydromechanical dynamic model to simulate a particular type of pitch-resonant WEC which uses gyroscopes for power extraction. The dynamic model consists of a time-domain three-dimensional Rankine panel method coupled, during time integration, with a MATLAB algorithm that solves for the equations of the gyroscope and Power Take-Off (PTO). The former acts as a force block, calculating the forces due to the waves on the hull, which is then sent to the latter through TCP/IP, which couples the external dynamics and performs the time integration using a 4th-order Runge-Kutta method. The panel method, accounting for the gyroscope and PTO dynamics, is then used for the calculation of the optimal flywheel spin, PTO damping, and average power extracted, completing the basic design cycle of the WEC. The proposed numerical method framework is capable of considering virtually any type of nonlinear force (e.g., nonlinear wave loads) and it is applied and verified in the paper against the traditional frequency domain linear model. It proved to be a versatile tool to verify performance in resonant conditions.

Rubbing dynamics behavior of a flywheel shafting with a single point flexible support

The flywheel energy storage system is a new kind conversion device which realizes electric energy and kinetic energy transform into each other. The dynamic characteristics of flywheel energy storage system have been studied extensively in recent years. A single point flexible support is suitable for the small flywheel system, because the friction loss is very low. The flywheel spin test system with a single point flexible support was built. The dynamic model of the flywheel shafting was established to calculate the critical speeds, modal shape and modal damping ratio at different speeds. The results show that the dynamic characteristics of the flywheel shaft are stable, and its structure is simple and efficient. The comparison between the calculated unbalance response and the experimental response indicates that the dynamic model is appropriate. When the flywheel started up and rotated at different speeds, the rubbing dynamics behavior was obtained by the experiment. Full rubbing occurred at high speed would damage the flywheel and stop, which should be tried to avoid.

Combined Singular Perturbations and Nonlinear Geometric Approach to FDI in Satellite Actuators and Sensors

This paper presents a novel scheme for the detection and isolation of faults affecting the sensors measuring the satellite attitude, body angular velocity and flywheel spin rates as well as defects related to the control torques provided by satellite momentum wheels. Thanks to the jointly use of the singular perturbations theory and nonlinear geometric approach, a novel fault detection and isolation system has been developed to accurately detect and isolate faults occurring on all the considered actuators and sensors. Simulation results are based on a detailed nonlinear satellite model with embedded disturbance description. The results document the effectiveness of the proposed fault detection and isolation scheme.

Haptic Orientation Guidance Using Two Parallel Double-Gimbal Control Moment Gyroscopes.

This paper presents a system of two double-gimbal control moment gyroscopes (CMGs) for providing ungrounded kinesthetic haptic feedback. By spinning a second flywheel opposite the first, and rotating them through opposite trajectories, undesired gyroscopic effects can be eliminated, isolating a single torque axis. This produces a moment pulse proportional to the flywheel spin speed and rotation speed. Rotating the CMG gimbals quickly in one direction, then resetting them more slowly generates repeated torque pulses indicating a clear direction cue. We present the mathematical model for moments produced by this system and verify that the performance of our device matches this model. Using these asymmetric moment pulses, we provide haptic cues to participants in two studies. In the first study, users simply identify the direction of torque cues. In the second study, we use the torque pulses to guide users to target orientations. Performance in both studies shows that this system has the potential to provide useful guidance for applications where ungrounded haptic feedback is desired.

Mechanics analysis on the composite flywheel stacked from circular twill woven fabric rings

The filament wound composite flywheel had a deficiency of being fragile along the radial direction because there is no reinforcing phase distribution. The failure along the radial direction due to delamination may happen when the thick cylinder composite flywheel rotate at high speed. A new way to solve the low radial strength problem of the composite flywheel is to use woven fabric material. The 2D woven fabric composite in the form of a circular ring has fibers in both the circumferential and radial directions to bear the stress. This structure features the combination of the typical two-dimensional orthogonal textile fabric and the classic axial laminations, performing new characters in mechanics. Samples of composite disks with 2D woven fabric material were designed and fabricated for spinning test, and the mechanics analysis on the thin woven composite disk was carried out for the first time. With the introduction of micromechanics methods, the elastic constants of the unit cell model of periodic volume representing the whole fabric were extracted from geometrical simplification and homogenization theories. The stiffness and strength of orthogonal twill woven fabric were predicted to evaluate the failure spinning speed of the fabric composite disks. The theoretical maximum spin speed of the woven flywheel could reach 1261rps with energy density of 53Wh/kg. The tension test data on samples of twill woven fabric composite helped with the prediction of failure of disk samples. The spinning tests confirmed that the tail weakness of the stacked configuration and the stiffness degradation from defects in composite contributed greatly to the stable running of flywheel spin.

Combined Geometric and Neural Network Approach to Generic Fault Diagnosis in Satellite Actuators and Sensors

This paper presents a novel scheme for diagnosis of faults affecting the sensors measuring the satellite attitude, body angular velocity and flywheel spin rates as well as defects related to the control torques provided by satellite reaction wheels. A nonlinear geometric design is used to avoid that aerodynamic disturbance torques have unwanted influence on the residuals exploited for fault detection and isolation. Radial basis function neural networks are used to obtain fault estimation filters that do not need a priori information about the fault internal models. Simulation results are based on a detailed nonlinear satellite model with embedded disturbance description. The results document the efficacy of the proposed diagnosis scheme.

Combined Geometric and Neural Network Approach to Generic Fault Diagnosis in Satellite Reaction Wheels

This paper suggests a novel diagnosis scheme for detection, isolation and estimation of faults affecting satellite reaction wheels. Both spin rate measurements and actuation torque defects are dealt with. The proposed system consists of a fault detection and isolation module composed by a bank of residual filters organized in a generalised scheme, followed by a fault estimation module consisting of a bank of adaptive estimation filters. The residuals are decoupled from aerodynamic disturbances thanks to the Nonlinear Geometric Approach. The use of Radial Basis Function Neural Networks is shown to allow design of generalised fault estimation filters, which do not need a priori information about the faults internal model. Simulation results with a detailed nonlinear spacecraft model, which includes disturbances, show that the proposed diagnosis scheme can deal with faults affecting both reaction wheel torques and flywheel spin rate measurements, and obtain precise fault isolation as well as accurate fault estimates.

Rotor dynamics analysis and experiment study of the flywheel spin test system

The strength study of the flywheel is important to the flywheel energy storage. The motor and bearing are the key challenges for the high-speed flywheel spin test device in vacuum. By using a small stiffness pivot-jewel bearing and a spring squeeze film damper as the lower support of the flywheel, a simple spin system was designed at a low cost and is suitable for longtime operation. The auxiliary sup- port at the top was not removed until the flywheel passed the first critical speed. The flywheel that kept its rigid state in sub-critical state was tested at the high speed without the top support. The dynamic model of the flywheel-bearing-damper was built by means of the La- grangian equation to calculate critical speeds, mode shapes and modal damping ratios at different speeds. The lower damper's effects on the modal damping ratios and forced vibration were discussed. The vibrations of the flywheel-bearing-damper system were measured at the different damping coefficients in the experiment. When the lower damper was adjusted to be overdamped, the flywheel ran up to 50000 r/min steadily, and the experimental result was in agreement with the theoretical assumption. The sub-critical rotor dynamics de- sign and pivot-jewel bearing proved to be good solutions to the spin test for the composite flywheel.

Regenerative Power-Optimal Reaction Wheel Attitude Control

This paper develops an analytical instantaneous power-optimal attitude control for a spacecraft using an integrated reaction wheel–flywheel system allowing for energy storage and return. The control is formulated in a general manner to use an arbitrarily large number of reaction wheels. It is applicable to systems with redundant wheels spanning three-dimensional space, which are controlled by a general attitude control law. The instantaneous power usage is minimized by modifying the wheel control torques using the wheel torque null motion. In this study, reducing the wheel speed results in negative power usage with perfect energy recuperation. Applying the maximum available wheel torque constraints, the null torque solution space is reduced to a hyperdimensional vector geometry problem, and the power-optimal wheel control torques are uniquely determined. The control modifications are applied to both attitude regulation and tracking control laws, demonstrating its performance for a variety of initial spacecraft states. Not only does the new control maximize the energy extraction from the reaction wheels, it also maintains the smallest flywheel spin rates, which helps reduce the maneuver-wide power usage.

Response of an urban bus flywheel battery to a rapid loss-of-vacuum event

The University of Texas at Austin Center for Electromechanics (UT-CEM) has developed a 2 kW-hr flywheel battery for energy management on a hybrid electric urban bus. The battery recovers braking energy and stores excess energy generated by the prime mover (e.g., internal combustion engine). The flywheel rotor, fabricated from high-strength composites, spins at 40,000 rpm at full charge (∼900 m/s tip speed), and is housed in a vacuum enclosure to minimize windage drag. Also integrated into the enclosure is a composite containment system that has been prooftested to provide additional safety. Ensuring flywheel safety is a major issue that must be addressed in using flywheels for transportation applications. A large leak caused by a service failure of the vacuum system could damage the flywheel before the energy dump system has time to act. A rapid loss-of-vacuum test on a rotor similar to that planned for the urban bus flywheel was conducted. Instrumentation, during the flywheel spin test recorded increasing flywheel surface temperature (>316°C or 600°F) following an intentional and abrupt loss of vacuum. No severe damage was noted on the surface of the flywheel, which was later retested to a higher speed to assess structural integrity. This paper provides an analysis of the data from that test and discusses the experimental results as they pertain to safety of the bus flywheel.

Kinematics and dynamics of a double-gimbaled control moment gyroscope

Control moment gyroscopes (CMGs) are torque-generating mechanisms that can be used for attitude and vibration control of spacecraft. CMGs consist of a rotating flywheel as well as a wheel-tilting actuator. Most CMG designs allow the flywheel spin axis to tilt about only one axis––a single-gimbaled CMG. This paper develops and analyzes the kinematics and dynamics of a novel double-gimbaled CMG design. The compact CMG design involves two four-bar linkages allowing the axis of rotation of the spinning flywheel to have two degrees of freedom.