Passive Fault Tolerance for a Magnetic Bearing Under PID Control

2001 ◽  
Author(s):  
Benjamin Choi ◽  
Andrew Provenza
Keyword(s):  
Fault Tolerance ◽  
Fault Tolerant ◽  
Magnetic Bearing ◽  
System Stability ◽  
Integral Term ◽  
Stability And Control ◽  
Stiffness And Damping ◽  
And Control ◽  
Component Failures ◽  
Detection Mechanisms

NASA Glenn Research Center (GRC) has developed a Fault-Tolerant Magnetic Bearing Suspension rig to enhance the safety of the bearing system for multiple component failures. A simple proportional-integral-derivative (PID) controller with no fault detection mechanisms was tested in a passive way where the initial bias current and control gains for all the eight heteropolar poles were not changed for the remaining active poles in the fault situations. The action of the integral term in the controller generated autonomous corrective actions for the pole failures to return the rotor to the set point (middle position) after the failure transient. The system stability and control of the rotor position were maintained over the entire speed range, where the rotor passes through the rigid body critical speeds and other rotor disturbances, provided that there was sufficient position stiffness and damping at low speeds. As far as the summation of force vectors of two attracting forces and rotor weight is zero, the passive fault tolerance was successfully demonstrated by using as few as two active poles out of the eight independent poles from each radial bearing (that is simply, 12 out of 16 poles dead). The rotor was spun without losing stability or desired position up to the rig’s maximum allowable speed of 20,000 rpm.

scholarly journals Stability and control of planar compass gait walking with series-elastic ankle actuation

2016 ◽  
Vol 39 (3) ◽  
pp. 312-323 ◽  
Author(s):  
Deniz Kerimoğlu ◽  
Ömer Morgül ◽  
Uluç Saranli
Keyword(s):  
Equations Of Motion ◽  
Period Doubling ◽  
Basic Structure ◽  
System Stability ◽  
Gravitational Potential Energy ◽  
Extended Model ◽  
Stability And Control ◽  
Inclined Surfaces ◽  
And Control ◽  
Series Elastic

Passive dynamic walking models are capable of capturing basic properties of walking behaviours and can generate stable human-like walking without any actuation on inclined surfaces. The passive compass gait model is among the simplest of such models, consisting of a planar point mass and two stick legs. A number of different actuation methods have been proposed both for this model and its more complex extensions to eliminate the need for a sloped ground, balancing collision losses using gravitational potential energy. In this study, we introduce and investigate an extended model with series-elastic actuation at the ankle towards a similar goal, realizing stable walking on level ground. Our model seeks to capture the basic structure of how humans utilize toe push-off prior to leg liftoff, and is intended to eventually be used for controlling the ankle joint in a lower-body robotic orthosis. We derive hybrid equations of motion for this model, and show numerically through Poincaré analysis that it can achieve asymptotically stable walking on level ground for certain choices of system parameters. We then study the bifurcation regimes of period doubling with this model, leading up to chaotic walking patterns. Finally, we show that feedback control on the initial extension of the series ankle spring can be used to improve and extend system stability.

Reconfigurable Fault-Tolerant Tilt-Rotor Quadcopter System

2018 ◽  
Author(s):  
Rumit Kumar ◽  
Siddharth Sridhar ◽  
Franck Cazaurang ◽  
Kelly Cohen ◽  
Manish Kumar
Keyword(s):  
Fault Tolerance ◽  
Dynamic Models ◽  
Fault Tolerant ◽  
Tilt Rotor ◽  
Failure Simulation ◽  
Dynamics And Control ◽  
Space Formulation ◽  
And Control ◽  
Controllability And Observability ◽  
Trim Flight

In this paper, fault-tolerance characteristics of a reconfigurable tilt-rotor quadcopter upon a propeller failure are presented. Traditional quadcopters experience instability and asymmetry about yaw-axis upon a propeller failure but the design and control strategy presented here can handle a complete propeller failure during flight. Fault-tolerance is achieved by means of structural and flight controller reconfiguration. The concept involves conversion of a tilt-rotor UAV into a T-copter. The dynamics and control of the tilt-rotor quadcopter are presented for ideal flight condition and for the reconfigured system in case of propeller failure. Analytical solution for trim flight conditions yielding zero angular rates for the UAV is derived. It has been shown that the structurally reconfigured UAV is controllable and completes the flight mission without much compromise in flight performance. The controllability and observability analysis of the reconfigured system is shown by state space formulation. The flight controllers for both dynamic models are analyzed and the applicability of the proposed concept is presented by propeller failure simulation during the way-point navigation.

The Internet of Things Based Fault Tolerant Redundancy for Energy Router in the Interacted and Interconnected Micro Grid

2020 ◽  
Vol 29 (07n08) ◽  
pp. 2040019
Author(s):  
Zixia Sang ◽  
Rengcun Fang ◽  
He Lei ◽  
Jiong Yan ◽  
Dongjun Yang ◽  
...  
Keyword(s):  
Internet Of Things ◽  
Fault Tolerant ◽  
Control Strategies ◽  
Distribution Network ◽  
Power Circuit ◽  
Micro Grid ◽  
Distribution Energy ◽  
Redundancy Design ◽  
And Control ◽  
Component Failures

The distribution energy router (DER) is the core of the interacted and interconnected micro grid in future distribution network, which fully meets the needs of the ubiquitous power internet of things (IOT) based future distribution network. The reliability of micro grid which applies the DER is highly related to its cascaded full-bridge converters. With the redundant full-bridge converters and IOT technology, the DER can stand the component failures, hence improve the robustness of the DER as well as the future interacted and interconnected micro grid. For a ubiquitous power IOT technology based DER, this paper proposes a redundancy design for fault tolerant strategy. Several redundancy designs are discussed in detail with operational principles and control strategies. The proposed redundancy design is implemented on the power circuit of one phase for DER consists of a nine-level cascaded full-bridge converter in Saber simulation platform, and the simulation results prove that the redundancy design can minimize the customer’s power interrupt time and the consequent damages to the system.

Fault Tolerant Magnetic Bearings

1999 ◽  
Vol 121 (3) ◽  
pp. 504-508 ◽  
Author(s):  
E. H. Maslen ◽  
C. K. Sortore ◽  
G. T. Gillies ◽  
R. D. Williams ◽  
S. J. Fedigan ◽  
...  
Keyword(s):  
Fault Tolerance ◽  
High Speed ◽  
Fault Tolerant ◽  
High Capacity ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Flexible Rotor ◽  
Variable Reluctance ◽  
Modular Redundancy ◽  
Bearing System

A fault tolerant magnetic bearing system was developed and demonstrated on a large flexible-rotor test rig. The bearing system comprises a high speed, fault tolerant digital controller, three high capacity radial magnetic bearings, one thrust bearing, conventional variable reluctance position sensors, and an array of commercial switching amplifiers. Controller fault tolerance is achieved through a very high speed voting mechanism which implements triple modular redundancy with a powered spare CPU, thereby permitting failure of up to three CPU modules without system failure. Amplifier/cabling/coil fault tolerance is achieved by using a separate power amplifier for each bearing coil and permitting amplifier reconfiguration by the controller upon detection of faults. This allows hot replacement of failed amplifiers without any system degradation and without providing any excess amplifier kVA capacity over the nominal system requirement. Implemented on a large (2440 mm in length) flexible rotor, the system shows excellent rejection of faults including the failure of three CPUs as well as failure of two adjacent amplifiers (or cabling) controlling an entire stator quadrant.

Stability and Control of a Parametrically Excited Rotating Beam

1998 ◽  
Vol 120 (4) ◽  
pp. 462-470 ◽  
Author(s):  
S. C. Sinha ◽  
Dan B. Marghitu ◽  
Dan Boghiu
Keyword(s):  
Equations Of Motion ◽  
System Stability ◽  
Flexible Beam ◽  
Parametrically Excited ◽  
Stability And Control ◽  
Rotation Parameters ◽  
The Stability ◽  
And Control ◽  
Time Invariant ◽  
Time Periodic

In this paper the stability and control of a parametrically excited, rotating flexible beam is considered. The equations of motion for such a system contain time periodic coefficients. Floquet theory and a numerical integration are used to evaluate the stability of the linearized system. Stability charts for various sets of damping, parametric excitation, and rotation parameters are obtained. Several resonance conditions are found and it is shown that the system stability can be significantly changed due to the rotation. Such systems can be used as preliminary models for studying the flap dynamics and control of helicopter rotor blades and flexible mechanisms among other systems. To control the motion of the system, an observer based controller is designed via Lyapunov-Floquet transformation. In this approach the time periodic equations are transformed into a time invariant form, which are suitable for the application of standard time invariant controller design techniques. Simulations for several combinations of excitation and rotation parameters are shown.

Renewable Integrated Power System Stability and Control

2021 ◽  
Author(s):  
Hêmin Golpîra ◽  
Arturo Román‐Messina ◽  
Hassan Bevrani
Keyword(s):  
Power System ◽  
Power System Stability ◽  
System Stability ◽  
Stability And Control ◽  
And Control ◽  
Integrated Power System
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