Rotor-gas bearings are attracting increasing interest because of their high speed capabilities, l... more Rotor-gas bearings are attracting increasing interest because of their high speed capabilities, low friction and clean operation. However, hydrostatic rotor-gas bearings show reduced damping characteristics, which makes it challenging to operate the rotating machine at and about the resonance frequencies. Active lubrication of the journal during operations could enhance the damping and stabilisation characteristics of the sytems, and this could be achieved by means of stabilising controllers. This paper investigates the feasibility of using reduced order models obtained through Grey-Box identification for the design of stabilising controllers, capable of enabling the active lubrication of the journal. The root locus analysis shows that two different control solutions are feasible for the dampening of the first two eigenfrequencies of the rotor-gas bearing in the horizontal and vertical directions. Hardening and softening P-lead controllers are designed based on the models experimentally identified, and salient features of both controllers are discussed. Both controllers are implemented and validated on the physical test rig. Experimental results confirm the validity of the proposed approach.
Gas bearings are popular for their high speed capabilities, low friction and clean operation, but... more Gas bearings are popular for their high speed capabilities, low friction and clean operation, but su er from poor damping, which poses challenges for safe operation in presence of disturbances. Enhanced damping can be achieved through active lubrication techniques using feedback control laws. Such control design requires models with low complexity, able to describe the dominant dynamics from actuator input to sensor output over the relevant range of operation. The mathematical models based on first principles are not easy to obtain, and in many cases, they cannot be directly used for control design due to their complexity and parameter uncertainties. As an alternative, this paper presents an experimental technique for ”in situ” identification of low complexity models of the entire rotor-bearingactuator system. Using grey-box identification techniques, the approach is shown to be easily applied to industrial rotating machinery with gas bearings and to allow for subsequent control design. The paper shows how piezoelectric actuators in a gas bearing are eciently used to perturb the gas film for identification over relevant ranges of rotational speed and gas injection pressure. Parameter-varying linear models are found to capture the dominant dynamics of the system over the range of operation. Based on the identified models, decentralised proportional control is designed and is shown to obtain the required damping in theory as well as in a laboratory test rig.
Rotor-gas bearings are attracting increasing interest because of their high speed capabilities, l... more Rotor-gas bearings are attracting increasing interest because of their high speed capabilities, low friction and clean operation. However, hydrostatic rotor-gas bearings show reduced damping characteristics, which makes it challenging to operate the rotating machine at and about the resonance frequencies. Active lubrication of the journal during operations could enhance the damping and stabilisation characteristics of the sytems, and this could be achieved by means of stabilising controllers. This paper investigates the feasibility of using reduced order models obtained through Grey-Box identification for the design of stabilising controllers, capable of enabling the active lubrication of the journal. The root locus analysis shows that two different control solutions are feasible for the dampening of the first two eigenfrequencies of the rotor-gas bearing in the horizontal and vertical directions. Hardening and softening P-lead controllers are designed based on the models experimentally identified, and salient features of both controllers are discussed. Both controllers are implemented and validated on the physical test rig. Experimental results confirm the validity of the proposed approach.
Gas bearings are popular for their high speed capabilities, low friction and clean operation, but... more Gas bearings are popular for their high speed capabilities, low friction and clean operation, but su er from poor damping, which poses challenges for safe operation in presence of disturbances. Enhanced damping can be achieved through active lubrication techniques using feedback control laws. Such control design requires models with low complexity, able to describe the dominant dynamics from actuator input to sensor output over the relevant range of operation. The mathematical models based on first principles are not easy to obtain, and in many cases, they cannot be directly used for control design due to their complexity and parameter uncertainties. As an alternative, this paper presents an experimental technique for ”in situ” identification of low complexity models of the entire rotor-bearingactuator system. Using grey-box identification techniques, the approach is shown to be easily applied to industrial rotating machinery with gas bearings and to allow for subsequent control design. The paper shows how piezoelectric actuators in a gas bearing are eciently used to perturb the gas film for identification over relevant ranges of rotational speed and gas injection pressure. Parameter-varying linear models are found to capture the dominant dynamics of the system over the range of operation. Based on the identified models, decentralised proportional control is designed and is shown to obtain the required damping in theory as well as in a laboratory test rig.
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Papers by Ilmar Santos
damping, which poses challenges for safe operation in presence of disturbances. Enhanced damping can be achieved
through active lubrication techniques using feedback control laws. Such control design requires models with low
complexity, able to describe the dominant dynamics from actuator input to sensor output over the relevant range of
operation. The mathematical models based on first principles are not easy to obtain, and in many cases, they cannot
be directly used for control design due to their complexity and parameter uncertainties. As an alternative, this paper
presents an experimental technique for ”in situ” identification of low complexity models of the entire rotor-bearingactuator
system. Using grey-box identification techniques, the approach is shown to be easily applied to industrial
rotating machinery with gas bearings and to allow for subsequent control design. The paper shows how piezoelectric
actuators in a gas bearing are eciently used to perturb the gas film for identification over relevant ranges of rotational
speed and gas injection pressure. Parameter-varying linear models are found to capture the dominant dynamics of the
system over the range of operation. Based on the identified models, decentralised proportional control is designed and
is shown to obtain the required damping in theory as well as in a laboratory test rig.
damping, which poses challenges for safe operation in presence of disturbances. Enhanced damping can be achieved
through active lubrication techniques using feedback control laws. Such control design requires models with low
complexity, able to describe the dominant dynamics from actuator input to sensor output over the relevant range of
operation. The mathematical models based on first principles are not easy to obtain, and in many cases, they cannot
be directly used for control design due to their complexity and parameter uncertainties. As an alternative, this paper
presents an experimental technique for ”in situ” identification of low complexity models of the entire rotor-bearingactuator
system. Using grey-box identification techniques, the approach is shown to be easily applied to industrial
rotating machinery with gas bearings and to allow for subsequent control design. The paper shows how piezoelectric
actuators in a gas bearing are eciently used to perturb the gas film for identification over relevant ranges of rotational
speed and gas injection pressure. Parameter-varying linear models are found to capture the dominant dynamics of the
system over the range of operation. Based on the identified models, decentralised proportional control is designed and
is shown to obtain the required damping in theory as well as in a laboratory test rig.