Sandira Gayadeen - Academia.edu (original) (raw)
Papers by Sandira Gayadeen
Closed loop stability of electron orbit feedback controllers is affected by mismatches between th... more Closed loop stability of electron orbit feedback controllers is affected by mismatches between the accelerator model and the real machine. In this paper, the small gain theorem is used to express analytical criteria for closed loop stability in the presence of spatial uncertainty. It is also demonstrated how the structure of the uncertainty models affects the conservativeness of the robust stability results. The robust stability criteria are applied to the Diamond Light Source electron orbit controller and bounds on the allowable size of spatial uncertainties which guarantee closed loop stability is determined.
IFAC-PapersOnLine, 2017
This paper considers the problem of designing an optimal controller for the linear static system ... more This paper considers the problem of designing an optimal controller for the linear static system associated with electron beam stabilisation systems in synchrotrons. The relationship between the actuators and sensors used for electron beam control in synchrotrons is modelled as a static response matrix which is typically ill-conditioned. Singular Value Decomposition (SVD) is commonly used to invert the response matrix and modes associated with small singular values are either discarded or filtered. In this paper, a robust control approach is used to determine the optimal static controller to the perturbed system. It is demonstrated how this approach compares to the use of Tikhonov regularisation for an inverse-based controller. A detailed example from the Diamond Light Source synchrotron is presented, applying both the inverse-based method and the robust control approach to stabilise electron beam motion.
Electron orbit feedback controllers are based on the inversion of the response matrix of the stor... more Electron orbit feedback controllers are based on the inversion of the response matrix of the storage ring and as a result, mismatches between the accelerator model and the real machine can limit controller performance or cause the controller to become unstable. In order to perform stability analysis tests of the controller, accurate uncertainty descriptions are required. In this paper, BPM scaling errors, actuator scaling errors and drifts in tune are considered as the main sources of spatial uncertainties and because most electron orbit feedback systems use Singular Value Decomposition (SVD) to decouple the inputs and outputs of the system, the uncertainty can be expressed in terms of this decomposition. However SVD does not allow the main sources of uncertainty to be decoupled so instead, a Fourier-based decomposition of the response matrix is used to decouple and model the uncertainties. In this paper, both Fourier and SVD uncertainty modelling methods are applied to the Diamond ...
2013 European Control Conference (ECC), 2013
In modern synchrotron machines, electrons travelling at relativistic speeds in a closed circular ... more In modern synchrotron machines, electrons travelling at relativistic speeds in a closed circular path are bent by strong electromagnetic fields, which cause the electrons to lose energy in the form of synchrotron radiation. In order to achieve optimum performance, electron beam stability is a crucial parameter for modern synchrotrons. In particular, sub-micron stability is now a common requirement for the vertical position of the beam and to achieve the required performance, beam stabilisation feedback systems are used. A common nonlinearity encountered with the actuators in synchrotron feedback systems are the slew rate limits that are included in the circuits that apply power to the magnets in order to limit voltage changes. The large dimensions of synchrotron feedback systems and fast sample rates mean that robust Model Predictive Control (MPC) is not feasible. Therefore, for this application, anti-windup techniques for rate constrained nonlinearities are appropriate. The approac...
At Diamond Light source, the main assumption for the Fast Orbit Feedback (FOFB) controller design... more At Diamond Light source, the main assumption for the Fast Orbit Feedback (FOFB) controller design is that the corrector magnets all have the same dynamic response. In this paper, a procedure to measure the frequency responses of the corrector magnets on the Diamond Storage Ring is presented and the magnet responses are measured and compared in order to assess whether this assumption is valid. The measurements are made by exciting a single corrector magnet with a sinusoidal input and measuring the resulting sinusoidal movement on the electron beam using electron Beam Position Monitors (eBPMs). The input excitation is varied from 10 Hz to 5 kHz using a 10 mA sine wave. The amplitude ratio and the phase difference between the input excitation and the beam position excitation are determined for each input frequency and the procedure is repeated for several magnets. Variations in both gain and phase across magnets are discussed in this paper and the effect of such variations on the perfo...
A unified control design is proposed to simultaneously determine the inputs to both the fast and ... more A unified control design is proposed to simultaneously determine the inputs to both the fast and slow arrays of correctors. By determining the interaction of the spatial subspaces of each array of correctors, spatial modes which require both fast and slow correctors can be identified. For these modes, a mid-ranging control technique is proposed to systematically allocate control action for each corrector. The mid-ranging control technique exploits the different dynamic characteristics of the correctors to ensure that the two arrays of actuators work together and avoid saturation of the fast correctors. Simulation results for the Diamond Storage Ring are presented.
At Diamond Light Source, the Double-Double Bend Achromat (DDBA) lattice upgrade involved the conv... more At Diamond Light Source, the Double-Double Bend Achromat (DDBA) lattice upgrade involved the conversion of one cell of the storage ring from a double bend achromat (DBA) structure to a double-DBA (DDBA). The new cell includes corrector magnets that are different in design to the DBA corrector magnets. The DDBA vacuum chamber cross section is also different from the DBA cells and includes both stainless steel and copper sections over which corrector magnets are fitted around. The performance of the Fast Orbit Feedback (FOFB) used for electron beam stabilisation with the DDBA cell installed is presented in this paper. Firstly the different corrector magnet dynamic responses are characterised and secondly the closed loop performance of the FOFB is measured and analysed for the upgraded lattice.
The I10 beamline at Diamond Light Source is configured to study circular dichroism. To increase s... more The I10 beamline at Diamond Light Source is configured to study circular dichroism. To increase signal to noise ratio between the two beam polarisations and increase temporal resolution the beamline is fed by two separate IDs that are typically configured with opposite handed polarisations. A chicane of steering magnets with programmable power supplies is used to provide 10Hz switching between the two photon beams by producing a dynamic closed bump that alternates the on-axis trajectory of the electron beam between the two IDs. In order to maintain the closed bump and make the switching transparent to the rest of the photon beamlines the phase and amplitude of the sine functions applied to the chicane magnets must be exactly correct. In this paper the linear scheme that was used to correct the residual 10Hz orbit distortion is presented. Future work that uses the fully programmable nature of the magnet power supply controllers to correct high order distortions is also discussed.
Acta Crystallographica Section A Foundations and Advances, 2017
Acta Crystallographica Section A Foundations and Advances, 2016
2015 54th IEEE Conference on Decision and Control (CDC), 2015
The paper proposes some design strategies of static anti-windup control schemes for systems descr... more The paper proposes some design strategies of static anti-windup control schemes for systems describing cross-directional processes. These are processes in which the variations of a variable in a profile orthogonal to the direction of propagation of the variable are controlled. Actually, the anti-windup synthesis approach takes advantages of the particular structure of such systems for which the interaction map between sensors and actuators along the propagation direction is expressed in terms of reduced singular value decompositions. The approach is developed within the framework of a synchrotron machine, in which electrons are accelerated in a closed circular path and bent by strong electromagnetic fields. Different results are proposed with increasing computational complexity to evaluate the potential interest of low dimension problems to solve the anti-windup design problem.
Automatica, 2016
By accelerating electrons to relativistic speeds, synchrotrons generate extremely intense and nar... more By accelerating electrons to relativistic speeds, synchrotrons generate extremely intense and narrow beams of electromagnetic light that are used for academic research and commercial development across a range of scientific disciplines. In order to achieve optimum performance, the stability of the electron beam is a crucial parameter for synchrotrons and is achieved by a beam stabilisation system that is used to control the location of the electron beam and minimise any instability of the electron beam caused by external disturbances. Slew rate limits are common nonlinearities encountered with the actuators in synchrotron feedback systems which can impose significant limitations on the robustness and the performance of the control system. This paper describes an Internal Model Control (IMC) based anti-windup synthesis using an algebraic Riccati equation for a discrete-time control system to compensate against the performance deterioration in the presence of rate constraints. An Integral Quadratic Constraint (IQC) framework is used to analyse the robust stability of the anti-windup augmented closed loop system in the presence of norm-bounded uncertainty. The anti-windup augmented controller is implemented at Diamond Light Source, the UK's national synchrotron facility and improvements in robustness and performance were achieved with respect to the use of no anti-windup compensation.
This thesis develops techniques for the design and analysis of controllers to achieve sub-micron ... more This thesis develops techniques for the design and analysis of controllers to achieve sub-micron accuracy on the position of electron beams for the optimal performance of synchrotrons. The techniques have been applied to Diamond Light Source, the UK's national synchrotron facility. Electron beam motion in synchrotrons is considered as a large-scale, two-dimensional process and by using basis functions, controllable modes of the process are identified which are independent and allow the design to be approached in terms of a family of single-input, single-output transfer functions. This thesis develops techniques for the design and analysis of controllers to achieve sub-micron accuracy on the position of electron beams for the optimal performance of synchrotrons. The techniques have been applied to Diamond Light Source, the UK's national synchrotron facility. Electron beam motion in synchrotrons is considered as a large-scale, two-dimensional process and by using basis functions, controllable modes of the process are identified which are independent and allow the design to be approached in terms of a family of single-input, single-output transfer functions. In this thesis, loop shaping concepts for dynamical systems are applied to the two-dimensional frequency domain to meet closed loop specifications. Spatial uncertainties are modelled by complex Fourier matrices and the closed loop robust stability, in the presence of spatial uncertainties is analysed within an Integral Quadratic Constraint framework. Two extensions to the unconstrained, single-actuator array controller design are considered. The first being anti-windup augmentation to give satisfactory performance when rate limit constraints are imposed on the actuators and the second being a strategy to account for two arrays of actuators with different dynamics. The resulting control schemes offer both stability and performance guarantees within structures that are feasible for online computation in real time.
This paper describes the design and implementation of fast orbit feedback control in mode space. ... more This paper describes the design and implementation of fast orbit feedback control in mode space. Using a Singular Value Decomposition (SVD) of the response matrix, each singular value can be associated with a spatial mode and enhanced feedback performance can be achieved by applying different controller dynamics to each spatial mode. By considering the disturbance spectrum across both dynamic and spatial frequencies, controller dynamics for each mode can be selected. Most orbit feedback systems apply only different gains to each mode however; mode space control gives greater flexibility in control design and can lead to enhanced disturbance suppression. Mode space control was implemented on the Booster synchrotron at Diamond Light Source, operated in stored beam mode. Implementation and performance of the mode space controller are presented.
The Fast Orbit Feedback system that has been installed on the Diamond Light Source Storage ring h... more The Fast Orbit Feedback system that has been installed on the Diamond Light Source Storage ring has been replicated on the Booster synchrotron in order to provide a test bed for the development of the Storage Ring controller design. To realise this the Booster is operated in DC mode. The electron beam is regulated in two planes using the Fast Orbit Feedback system, which takes the beam position from 22 beam position monitors for each plane, and calculates offsets to 44 corrector power supplies at a sample rate of 10 kHz. This paper describes the design and realization of the controller for the Booster Fast Orbit Feedback, presents results from the implementation and considers future development.
Proceedings of the 18th IFAC World Congress, 2011
The robustness properties of multivariable plants with either a single input or single output (bu... more The robustness properties of multivariable plants with either a single input or single output (but not both) under feedback control can be represented succinctly in the frequency domain. Both the robust stability and robust performance of multi-input single-output plants are considered. These results are illustrated for internal model control design of mid-ranging systems. The robust stability of single-input multi-output plants is also considered.
IFAC Proceedings Volumes, 2009
Existing tuning rules for mid-ranging control can be improved. In this paper a novel strategy for... more Existing tuning rules for mid-ranging control can be improved. In this paper a novel strategy for midranging control based on Internal Model Control (IMC) principles is presented. The design reformulates mid-ranging control specifications in terms of classical bandwidth and sensitivity requirements. The performance of this design is demonstrated through simulation studies. The overall benefits of the IMC design are that it provides transparent and flexible tuning, and that it offers a natural framework for antiwindup. Both classical IMC and modified IMC structures are considered for anti-windup. Their performance during saturation is demonstrated through simulation studies, where minimal degradation is observed.
2012 IEEE 51st IEEE Conference on Decision and Control (CDC), 2012
ABSTRACT There are over forty synchrotrons and fourth generation light sources around the world, ... more ABSTRACT There are over forty synchrotrons and fourth generation light sources around the world, which generate synchrotron radiation for academic and industry research by bending electrons that are accelerated to relativistic speeds. To preserve the quality of the photon beam used for experiments, a feedback control system is used to reduce variations in the position of the electron beam. This paper describes the design and robust stability analysis of a beam stabilisation controller, which is considered as a cross-directional control system. Fourier series analysis is used to identify the spatially controllable components of the system and develop a realistic uncertainty model that is used in robust stability tests. The robust stability of the controller is determined by considering both the unbounded sector nonlinearity associated with the actuators and the unmodeled spatial plant response within an Integral Quadratic Constraint (IQC) framework, leading to a robust stability condition that is expressed as a linear matrix inequality (LMI). The paper presents results from the implementation of the controller at Diamond Light Source.
2013 American Control Conference, 2013
ABSTRACT This paper considers the design of electron beam stabilisation control systems for synch... more ABSTRACT This paper considers the design of electron beam stabilisation control systems for synchrotrons that simultaneously determine the inputs to multiple arrays of actuators for regulating variations in the electron beam position. An approach based on determining the interaction of the controllable subspaces is used. This enables the control problem to be decomposed into a series of single-input, single-output; multiple-input, single output and multiple-input, multiple-output problems. An Internal Model Control structure is used to design the controllers for each case and mid-ranging control is proposed for the case where the control directions align. Results from a simulation study using machine data from the Booster synchrotron of the UK's national synchrotron facility, Diamond Light Source are presented.
2011 IEEE International Conference on Control Applications (CCA), 2011
ABSTRACT Synchrotron light sources can produce very in- tense beams of X-rays and ultra violet li... more ABSTRACT Synchrotron light sources can produce very in- tense beams of X-rays and ultra violet light for a range of applications, including protein crystallography, materials char- acterization and high resolution imaging. The Diamond Light Source is a rd generation synchrotron that has recently been constructed near Oxford, United Kingdom, which produces a 3 GeV electron beam in a ring of circumference of over 560 m. A key requirement of the process is that the vertical and horizontal location of the beam should be controlled to within 10% of the beam size, which corresponds to the RMS variation being less than 12.3 m in the horizontal direction and 0.6 m in the vertical direction. The beam location is subjected to disturbances caused by the effects of Insertion Devices and the effect of ground motion, particularly between 16 Hz and 30 Hz, where the ground motion is amplified by the resonances of the girders supporting the ring magnets. To achieve the specification, a fast beam stabilization feedback system is used to regulate the horizontal and vertical position of the beam in the presence of disturbances in the range 1 Hz to 100 Hz, using 170 sensors and actuators in both planes, positioned around the ring at a sampling rate of 10 kHz. This paper describes the design of the controller for this system and the results from the implementation are shown.
Closed loop stability of electron orbit feedback controllers is affected by mismatches between th... more Closed loop stability of electron orbit feedback controllers is affected by mismatches between the accelerator model and the real machine. In this paper, the small gain theorem is used to express analytical criteria for closed loop stability in the presence of spatial uncertainty. It is also demonstrated how the structure of the uncertainty models affects the conservativeness of the robust stability results. The robust stability criteria are applied to the Diamond Light Source electron orbit controller and bounds on the allowable size of spatial uncertainties which guarantee closed loop stability is determined.
IFAC-PapersOnLine, 2017
This paper considers the problem of designing an optimal controller for the linear static system ... more This paper considers the problem of designing an optimal controller for the linear static system associated with electron beam stabilisation systems in synchrotrons. The relationship between the actuators and sensors used for electron beam control in synchrotrons is modelled as a static response matrix which is typically ill-conditioned. Singular Value Decomposition (SVD) is commonly used to invert the response matrix and modes associated with small singular values are either discarded or filtered. In this paper, a robust control approach is used to determine the optimal static controller to the perturbed system. It is demonstrated how this approach compares to the use of Tikhonov regularisation for an inverse-based controller. A detailed example from the Diamond Light Source synchrotron is presented, applying both the inverse-based method and the robust control approach to stabilise electron beam motion.
Electron orbit feedback controllers are based on the inversion of the response matrix of the stor... more Electron orbit feedback controllers are based on the inversion of the response matrix of the storage ring and as a result, mismatches between the accelerator model and the real machine can limit controller performance or cause the controller to become unstable. In order to perform stability analysis tests of the controller, accurate uncertainty descriptions are required. In this paper, BPM scaling errors, actuator scaling errors and drifts in tune are considered as the main sources of spatial uncertainties and because most electron orbit feedback systems use Singular Value Decomposition (SVD) to decouple the inputs and outputs of the system, the uncertainty can be expressed in terms of this decomposition. However SVD does not allow the main sources of uncertainty to be decoupled so instead, a Fourier-based decomposition of the response matrix is used to decouple and model the uncertainties. In this paper, both Fourier and SVD uncertainty modelling methods are applied to the Diamond ...
2013 European Control Conference (ECC), 2013
In modern synchrotron machines, electrons travelling at relativistic speeds in a closed circular ... more In modern synchrotron machines, electrons travelling at relativistic speeds in a closed circular path are bent by strong electromagnetic fields, which cause the electrons to lose energy in the form of synchrotron radiation. In order to achieve optimum performance, electron beam stability is a crucial parameter for modern synchrotrons. In particular, sub-micron stability is now a common requirement for the vertical position of the beam and to achieve the required performance, beam stabilisation feedback systems are used. A common nonlinearity encountered with the actuators in synchrotron feedback systems are the slew rate limits that are included in the circuits that apply power to the magnets in order to limit voltage changes. The large dimensions of synchrotron feedback systems and fast sample rates mean that robust Model Predictive Control (MPC) is not feasible. Therefore, for this application, anti-windup techniques for rate constrained nonlinearities are appropriate. The approac...
At Diamond Light source, the main assumption for the Fast Orbit Feedback (FOFB) controller design... more At Diamond Light source, the main assumption for the Fast Orbit Feedback (FOFB) controller design is that the corrector magnets all have the same dynamic response. In this paper, a procedure to measure the frequency responses of the corrector magnets on the Diamond Storage Ring is presented and the magnet responses are measured and compared in order to assess whether this assumption is valid. The measurements are made by exciting a single corrector magnet with a sinusoidal input and measuring the resulting sinusoidal movement on the electron beam using electron Beam Position Monitors (eBPMs). The input excitation is varied from 10 Hz to 5 kHz using a 10 mA sine wave. The amplitude ratio and the phase difference between the input excitation and the beam position excitation are determined for each input frequency and the procedure is repeated for several magnets. Variations in both gain and phase across magnets are discussed in this paper and the effect of such variations on the perfo...
A unified control design is proposed to simultaneously determine the inputs to both the fast and ... more A unified control design is proposed to simultaneously determine the inputs to both the fast and slow arrays of correctors. By determining the interaction of the spatial subspaces of each array of correctors, spatial modes which require both fast and slow correctors can be identified. For these modes, a mid-ranging control technique is proposed to systematically allocate control action for each corrector. The mid-ranging control technique exploits the different dynamic characteristics of the correctors to ensure that the two arrays of actuators work together and avoid saturation of the fast correctors. Simulation results for the Diamond Storage Ring are presented.
At Diamond Light Source, the Double-Double Bend Achromat (DDBA) lattice upgrade involved the conv... more At Diamond Light Source, the Double-Double Bend Achromat (DDBA) lattice upgrade involved the conversion of one cell of the storage ring from a double bend achromat (DBA) structure to a double-DBA (DDBA). The new cell includes corrector magnets that are different in design to the DBA corrector magnets. The DDBA vacuum chamber cross section is also different from the DBA cells and includes both stainless steel and copper sections over which corrector magnets are fitted around. The performance of the Fast Orbit Feedback (FOFB) used for electron beam stabilisation with the DDBA cell installed is presented in this paper. Firstly the different corrector magnet dynamic responses are characterised and secondly the closed loop performance of the FOFB is measured and analysed for the upgraded lattice.
The I10 beamline at Diamond Light Source is configured to study circular dichroism. To increase s... more The I10 beamline at Diamond Light Source is configured to study circular dichroism. To increase signal to noise ratio between the two beam polarisations and increase temporal resolution the beamline is fed by two separate IDs that are typically configured with opposite handed polarisations. A chicane of steering magnets with programmable power supplies is used to provide 10Hz switching between the two photon beams by producing a dynamic closed bump that alternates the on-axis trajectory of the electron beam between the two IDs. In order to maintain the closed bump and make the switching transparent to the rest of the photon beamlines the phase and amplitude of the sine functions applied to the chicane magnets must be exactly correct. In this paper the linear scheme that was used to correct the residual 10Hz orbit distortion is presented. Future work that uses the fully programmable nature of the magnet power supply controllers to correct high order distortions is also discussed.
Acta Crystallographica Section A Foundations and Advances, 2017
Acta Crystallographica Section A Foundations and Advances, 2016
2015 54th IEEE Conference on Decision and Control (CDC), 2015
The paper proposes some design strategies of static anti-windup control schemes for systems descr... more The paper proposes some design strategies of static anti-windup control schemes for systems describing cross-directional processes. These are processes in which the variations of a variable in a profile orthogonal to the direction of propagation of the variable are controlled. Actually, the anti-windup synthesis approach takes advantages of the particular structure of such systems for which the interaction map between sensors and actuators along the propagation direction is expressed in terms of reduced singular value decompositions. The approach is developed within the framework of a synchrotron machine, in which electrons are accelerated in a closed circular path and bent by strong electromagnetic fields. Different results are proposed with increasing computational complexity to evaluate the potential interest of low dimension problems to solve the anti-windup design problem.
Automatica, 2016
By accelerating electrons to relativistic speeds, synchrotrons generate extremely intense and nar... more By accelerating electrons to relativistic speeds, synchrotrons generate extremely intense and narrow beams of electromagnetic light that are used for academic research and commercial development across a range of scientific disciplines. In order to achieve optimum performance, the stability of the electron beam is a crucial parameter for synchrotrons and is achieved by a beam stabilisation system that is used to control the location of the electron beam and minimise any instability of the electron beam caused by external disturbances. Slew rate limits are common nonlinearities encountered with the actuators in synchrotron feedback systems which can impose significant limitations on the robustness and the performance of the control system. This paper describes an Internal Model Control (IMC) based anti-windup synthesis using an algebraic Riccati equation for a discrete-time control system to compensate against the performance deterioration in the presence of rate constraints. An Integral Quadratic Constraint (IQC) framework is used to analyse the robust stability of the anti-windup augmented closed loop system in the presence of norm-bounded uncertainty. The anti-windup augmented controller is implemented at Diamond Light Source, the UK's national synchrotron facility and improvements in robustness and performance were achieved with respect to the use of no anti-windup compensation.
This thesis develops techniques for the design and analysis of controllers to achieve sub-micron ... more This thesis develops techniques for the design and analysis of controllers to achieve sub-micron accuracy on the position of electron beams for the optimal performance of synchrotrons. The techniques have been applied to Diamond Light Source, the UK's national synchrotron facility. Electron beam motion in synchrotrons is considered as a large-scale, two-dimensional process and by using basis functions, controllable modes of the process are identified which are independent and allow the design to be approached in terms of a family of single-input, single-output transfer functions. This thesis develops techniques for the design and analysis of controllers to achieve sub-micron accuracy on the position of electron beams for the optimal performance of synchrotrons. The techniques have been applied to Diamond Light Source, the UK's national synchrotron facility. Electron beam motion in synchrotrons is considered as a large-scale, two-dimensional process and by using basis functions, controllable modes of the process are identified which are independent and allow the design to be approached in terms of a family of single-input, single-output transfer functions. In this thesis, loop shaping concepts for dynamical systems are applied to the two-dimensional frequency domain to meet closed loop specifications. Spatial uncertainties are modelled by complex Fourier matrices and the closed loop robust stability, in the presence of spatial uncertainties is analysed within an Integral Quadratic Constraint framework. Two extensions to the unconstrained, single-actuator array controller design are considered. The first being anti-windup augmentation to give satisfactory performance when rate limit constraints are imposed on the actuators and the second being a strategy to account for two arrays of actuators with different dynamics. The resulting control schemes offer both stability and performance guarantees within structures that are feasible for online computation in real time.
This paper describes the design and implementation of fast orbit feedback control in mode space. ... more This paper describes the design and implementation of fast orbit feedback control in mode space. Using a Singular Value Decomposition (SVD) of the response matrix, each singular value can be associated with a spatial mode and enhanced feedback performance can be achieved by applying different controller dynamics to each spatial mode. By considering the disturbance spectrum across both dynamic and spatial frequencies, controller dynamics for each mode can be selected. Most orbit feedback systems apply only different gains to each mode however; mode space control gives greater flexibility in control design and can lead to enhanced disturbance suppression. Mode space control was implemented on the Booster synchrotron at Diamond Light Source, operated in stored beam mode. Implementation and performance of the mode space controller are presented.
The Fast Orbit Feedback system that has been installed on the Diamond Light Source Storage ring h... more The Fast Orbit Feedback system that has been installed on the Diamond Light Source Storage ring has been replicated on the Booster synchrotron in order to provide a test bed for the development of the Storage Ring controller design. To realise this the Booster is operated in DC mode. The electron beam is regulated in two planes using the Fast Orbit Feedback system, which takes the beam position from 22 beam position monitors for each plane, and calculates offsets to 44 corrector power supplies at a sample rate of 10 kHz. This paper describes the design and realization of the controller for the Booster Fast Orbit Feedback, presents results from the implementation and considers future development.
Proceedings of the 18th IFAC World Congress, 2011
The robustness properties of multivariable plants with either a single input or single output (bu... more The robustness properties of multivariable plants with either a single input or single output (but not both) under feedback control can be represented succinctly in the frequency domain. Both the robust stability and robust performance of multi-input single-output plants are considered. These results are illustrated for internal model control design of mid-ranging systems. The robust stability of single-input multi-output plants is also considered.
IFAC Proceedings Volumes, 2009
Existing tuning rules for mid-ranging control can be improved. In this paper a novel strategy for... more Existing tuning rules for mid-ranging control can be improved. In this paper a novel strategy for midranging control based on Internal Model Control (IMC) principles is presented. The design reformulates mid-ranging control specifications in terms of classical bandwidth and sensitivity requirements. The performance of this design is demonstrated through simulation studies. The overall benefits of the IMC design are that it provides transparent and flexible tuning, and that it offers a natural framework for antiwindup. Both classical IMC and modified IMC structures are considered for anti-windup. Their performance during saturation is demonstrated through simulation studies, where minimal degradation is observed.
2012 IEEE 51st IEEE Conference on Decision and Control (CDC), 2012
ABSTRACT There are over forty synchrotrons and fourth generation light sources around the world, ... more ABSTRACT There are over forty synchrotrons and fourth generation light sources around the world, which generate synchrotron radiation for academic and industry research by bending electrons that are accelerated to relativistic speeds. To preserve the quality of the photon beam used for experiments, a feedback control system is used to reduce variations in the position of the electron beam. This paper describes the design and robust stability analysis of a beam stabilisation controller, which is considered as a cross-directional control system. Fourier series analysis is used to identify the spatially controllable components of the system and develop a realistic uncertainty model that is used in robust stability tests. The robust stability of the controller is determined by considering both the unbounded sector nonlinearity associated with the actuators and the unmodeled spatial plant response within an Integral Quadratic Constraint (IQC) framework, leading to a robust stability condition that is expressed as a linear matrix inequality (LMI). The paper presents results from the implementation of the controller at Diamond Light Source.
2013 American Control Conference, 2013
ABSTRACT This paper considers the design of electron beam stabilisation control systems for synch... more ABSTRACT This paper considers the design of electron beam stabilisation control systems for synchrotrons that simultaneously determine the inputs to multiple arrays of actuators for regulating variations in the electron beam position. An approach based on determining the interaction of the controllable subspaces is used. This enables the control problem to be decomposed into a series of single-input, single-output; multiple-input, single output and multiple-input, multiple-output problems. An Internal Model Control structure is used to design the controllers for each case and mid-ranging control is proposed for the case where the control directions align. Results from a simulation study using machine data from the Booster synchrotron of the UK's national synchrotron facility, Diamond Light Source are presented.
2011 IEEE International Conference on Control Applications (CCA), 2011
ABSTRACT Synchrotron light sources can produce very in- tense beams of X-rays and ultra violet li... more ABSTRACT Synchrotron light sources can produce very in- tense beams of X-rays and ultra violet light for a range of applications, including protein crystallography, materials char- acterization and high resolution imaging. The Diamond Light Source is a rd generation synchrotron that has recently been constructed near Oxford, United Kingdom, which produces a 3 GeV electron beam in a ring of circumference of over 560 m. A key requirement of the process is that the vertical and horizontal location of the beam should be controlled to within 10% of the beam size, which corresponds to the RMS variation being less than 12.3 m in the horizontal direction and 0.6 m in the vertical direction. The beam location is subjected to disturbances caused by the effects of Insertion Devices and the effect of ground motion, particularly between 16 Hz and 30 Hz, where the ground motion is amplified by the resonances of the girders supporting the ring magnets. To achieve the specification, a fast beam stabilization feedback system is used to regulate the horizontal and vertical position of the beam in the presence of disturbances in the range 1 Hz to 100 Hz, using 170 sensors and actuators in both planes, positioned around the ring at a sampling rate of 10 kHz. This paper describes the design of the controller for this system and the results from the implementation are shown.