Direct-drive linear reciprocating compressors offer numerous advantages over conventional counter... more Direct-drive linear reciprocating compressors offer numerous advantages over conventional counterparts which are usually driven by a rotary induction motor via a crank shaft. However, to ensure efficient and reliable operation under all conditions, it is essential that motor current of a linear compressor follows a sinusoidal current command with a frequency which matches the system resonant frequency. The design of a high-performance current controller for linear compressor drive presents a challenge since the system is highly nonlinear, and an effective solution must be low cost. In this paper, a learning feed-forward current controller for the linear compressors is proposed. It comprises a conventional feedback proportional-integral controller and a feed-forward B-spline neural network (BSNN). The feed-forward BSNN is trained online and in real time in order to minimize the current tracking error. Extensive simulation and experiment results with a prototype linear compressor show that the proposed current controller exhibits high steady state and transient performance.
To reduce torque ripple in a switched reluctance motor (SRM) by current profiling, a high-perform... more To reduce torque ripple in a switched reluctance motor (SRM) by current profiling, a high-performance current controller is necessary. This study presents a high-performance current controller for SRM drives. A Bspline neural network is used to model the non-linearity of the SRM and estimate back electromotive force (EMF) and incremental inductance on-line in real time. The on-line modelling scheme does not require a priori knowledge of the machine's electromagnetic characteristics. Based on the on-line estimated parameters, a current controller with adjustable PI gains and back-EMF decoupling is implemented. The performance of the current controller has been demonstrated in simulation and experimentally using a four-phase 8/6 550 W SRM drive system.
This paper describes a design methodology to achieve optimal performance for a short-stroke, sing... more This paper describes a design methodology to achieve optimal performance for a short-stroke, single phase tubular permanent magnet motor which drives a reciprocating vapor compressor. The steady-state characteristic of the directdrive linear motor-compressor system is analyzed, and a motor design procedure which takes into account of the effect of compressor loads under nominal operating condition is formulated. It is shown that the motor efficiency can be optimized with respect to two leading dimensional ratios. Experimental results validate the proposed design methodology.
ABSTRACT The analysis of a novel single-phase, short-stroke, reciprocating tubular motor with a q... more ABSTRACT The analysis of a novel single-phase, short-stroke, reciprocating tubular motor with a quasi-Halbach magnetised moving-magnet armature is described. The motor was developed for applications such as linear compressors. The magnetic field distribution, the back-emf and the thrust force of the motor are established analytically in the cylindrical co-ordinate system, and predictions are compared with results derived from finite-element (FE) analysis. It is shown that the difference between the analytical and FE predicted average emf (thrust force) over the operating stroke of 0.01 m is <5%. The analysis and the emf and thrust force predictions are validated by measurements.
… of the Institution of Mechanical Engineers …, 2007
ABSTRACT The current paper analyses the steady-state and dynamic performance characteristics of a... more ABSTRACT The current paper analyses the steady-state and dynamic performance characteristics of a direct-drive linear vapour compressor, and it is shown that it operates most efficiently and stably at resonance under current source excitation. Further, the piston amplitude and top clearance vary almost linearly with the amplitude of the excitation current. These features facilitate efficient operation and control of the linear compressor without the need for a discrete piston position sensor, and provide a simple means of regulating the cooling capacity according to the refrigerator demand. The findings are validated by measurements on a prototype linear compressor.
A novel on-line instant torque estimation scheme for a switched reluctance motor (SRM) is present... more A novel on-line instant torque estimation scheme for a switched reluctance motor (SRM) is presented. In the proposed method, an adaptive B-spline neural network is used to learn the non-linear flux-linkage and torque characteristics of a SRM. Due to the local nature of its generalisation properties, the training of the B-spline neural network is accomplished on-line and in real-time, and the system does not require a priori knowledge of the machine's electromagnetic characteristics. The potential of the method is demonstrated successfully in simulation and experimentally using a 300 W 12/8 3-phase SRM.
The paper examines the relative merits of competing linear motor technologies and topologies for ... more The paper examines the relative merits of competing linear motor technologies and topologies for reciprocating compressor applications. It has been shown that a single-phase, short-stroke, tubular permanent magnet excited motor with a quasi-Halbach magnetized armature and a slotted stator is the most appropriate, due to its high specific force capability and efficiency, its relative simplicity, and the availability of emerging
Direct-drive linear reciprocating compressors offer numerous advantages over conventional counter... more Direct-drive linear reciprocating compressors offer numerous advantages over conventional counterparts which are usually driven by a rotary induction motor via crank shaft. However, to ensure efficient and reliable operation under all conditions, it is essential that the motor current of the linear compressor follows a sinusoidal command profile with a frequency which matches the system resonant frequency. This paper describes a hybrid current controller for the linear compressors. It comprises a conventional proportional-integral (PI) controller, and a B-spline neural network compensator which is trained on-line and in real-time in order to minimize the current tracking error under all conditions with uncertain disturbances. It has been shown that the hybrid current controller has a superior steady-state and transient performance over the conventional carrier based PI controller. The performance of the proposed hybrid controller has been demonstrated by extensive simulations and experiments. It has also been shown that the linear compressor operates stably under the current feedback control and the piston stroke can be adjusted by varying the amplitude of the current command.
This paper considers torque ripple minimisation control for switched reluctance motors (SRMs) and... more This paper considers torque ripple minimisation control for switched reluctance motors (SRMs) and presents a novel on-line approach to the estimation of instantaneous torque. An adaptive B-spline neural network is used to learn the non-linear flux linkage and torque characteristics of an SRM. The training of the B-spline neural network is accomplished on-line in real-time, and the system does not require a priori knowledge of the SRM's electromagnetic characteristics. The potential of the torque estimation method is demonstrated in simulation and experimentally using a 550 W 8/6 four-phase SRM operating in saturation, and it has been applied successfully to torque ripple minimisation.
This paper proposed a DSP controlled 2 kW PFC converter with a novel sampling algorithm which can... more This paper proposed a DSP controlled 2 kW PFC converter with a novel sampling algorithm which can greatly improve switching noise immunity in almost all average current control power supplies. Based on the newly developed DSP chip TMS320F240, a 2 kW PFC stage designed as the front-end of a frequency-variable air-conditioner is implemented. The novel sampling algorithm shows great advantages when the switch operates in the range above 30 kHz
This paper describes alternative winding configurations of a short-stroke, single phase tubular p... more This paper describes alternative winding configurations of a short-stroke, single phase tubular permanent magnet motor for linear compressor applications. Three design variants are considered and analyzed, and their relative merits are evaluated. The open-circuit magnetic field distribution, backemf and thrust force are established analytically, and the results are compared and validated by finite element analysis and experimental measurement on a prototype motor.
ABSTRACT A linear vapor compressor operates most efficiently at resonant frequency which varies w... more ABSTRACT A linear vapor compressor operates most efficiently at resonant frequency which varies with piston stroke and operation conditions. A novel resonant frequency tracking technique is proposed in order to achieve high efficiency operation of a linear compressor system. This is based on the fact that for given amplitude of the motor current, the linear compressor system reaches its maximum stroke and maximum input and output powers at its resonant frequency. By evaluation of the input power to the compressor and implementing a perturb and observe algorithm, the proposed technique can adjust the frequency of the motor current to match the resonant frequency of the compressor operation. The proposed technique does not require a position sensor, and can be easily implemented in a digital controller. Simulation and experimental results have demonstrated the validity of the proposed technique.
A switched reluctance motor torque ripple reduction scheme using a B-spline neural network (BSNN)... more A switched reluctance motor torque ripple reduction scheme using a B-spline neural network (BSNN) is presented. Closed-loop torque control can be implemented using an on-line torque estimator. Due to the local weight updating algorithm used for the BSNN, an appropriate phase current profile for torque ripple reduction can be obtained on-line in real time. It has good dynamic performance with respect to changes in torque demand. The scheme does not require high-bandwidth current controllers. Simulation and experimental results demonstrate the validity of the scheme.
A novel online-modeling scheme for the switched reluctance motor (SRM) using a B-spline neural ne... more A novel online-modeling scheme for the switched reluctance motor (SRM) using a B-spline neural network (BSNN) is proposed in this paper. A 2-D BSNN is designed to learn the nonlinear-flux-linkage characteristic of an SRM online and in real-time. Torque, incremental inductance, and back-emf estimates can be derived from the BSNN after training. The scheme does not require a priori knowledge of the SRM electromagnetic characteristics. Simulation and experimental results show that the scheme has a good estimation performance and robustness at low to medium motor speed.
This paper proposes a novel sampling algorithm for digital signal processing (DSP) controlled 2 k... more This paper proposes a novel sampling algorithm for digital signal processing (DSP) controlled 2 kW power factor correction (PFCs) converters, which can improve switching noise immunity greatly in average-current-control power supplies. Based on the newly developed DSP chip TMS320F240, a 2 kW PFC stage is implemented. The novel sampling algorithm shows great advantages when the converter operates at a frequency above 30 kHz.
Direct-drive linear reciprocating compressors offer numerous advantages over conventional counter... more Direct-drive linear reciprocating compressors offer numerous advantages over conventional counterparts which are usually driven by a rotary induction motor via a crank shaft. However, to ensure efficient and reliable operation under all conditions, it is essential that motor current of a linear compressor follows a sinusoidal current command with a frequency which matches the system resonant frequency. The design of a high-performance current controller for linear compressor drive presents a challenge since the system is highly nonlinear, and an effective solution must be low cost. In this paper, a learning feed-forward current controller for the linear compressors is proposed. It comprises a conventional feedback proportional-integral controller and a feed-forward B-spline neural network (BSNN). The feed-forward BSNN is trained online and in real time in order to minimize the current tracking error. Extensive simulation and experiment results with a prototype linear compressor show that the proposed current controller exhibits high steady state and transient performance.
To reduce torque ripple in a switched reluctance motor (SRM) by current profiling, a high-perform... more To reduce torque ripple in a switched reluctance motor (SRM) by current profiling, a high-performance current controller is necessary. This study presents a high-performance current controller for SRM drives. A Bspline neural network is used to model the non-linearity of the SRM and estimate back electromotive force (EMF) and incremental inductance on-line in real time. The on-line modelling scheme does not require a priori knowledge of the machine's electromagnetic characteristics. Based on the on-line estimated parameters, a current controller with adjustable PI gains and back-EMF decoupling is implemented. The performance of the current controller has been demonstrated in simulation and experimentally using a four-phase 8/6 550 W SRM drive system.
This paper describes a design methodology to achieve optimal performance for a short-stroke, sing... more This paper describes a design methodology to achieve optimal performance for a short-stroke, single phase tubular permanent magnet motor which drives a reciprocating vapor compressor. The steady-state characteristic of the directdrive linear motor-compressor system is analyzed, and a motor design procedure which takes into account of the effect of compressor loads under nominal operating condition is formulated. It is shown that the motor efficiency can be optimized with respect to two leading dimensional ratios. Experimental results validate the proposed design methodology.
ABSTRACT The analysis of a novel single-phase, short-stroke, reciprocating tubular motor with a q... more ABSTRACT The analysis of a novel single-phase, short-stroke, reciprocating tubular motor with a quasi-Halbach magnetised moving-magnet armature is described. The motor was developed for applications such as linear compressors. The magnetic field distribution, the back-emf and the thrust force of the motor are established analytically in the cylindrical co-ordinate system, and predictions are compared with results derived from finite-element (FE) analysis. It is shown that the difference between the analytical and FE predicted average emf (thrust force) over the operating stroke of 0.01 m is <5%. The analysis and the emf and thrust force predictions are validated by measurements.
… of the Institution of Mechanical Engineers …, 2007
ABSTRACT The current paper analyses the steady-state and dynamic performance characteristics of a... more ABSTRACT The current paper analyses the steady-state and dynamic performance characteristics of a direct-drive linear vapour compressor, and it is shown that it operates most efficiently and stably at resonance under current source excitation. Further, the piston amplitude and top clearance vary almost linearly with the amplitude of the excitation current. These features facilitate efficient operation and control of the linear compressor without the need for a discrete piston position sensor, and provide a simple means of regulating the cooling capacity according to the refrigerator demand. The findings are validated by measurements on a prototype linear compressor.
A novel on-line instant torque estimation scheme for a switched reluctance motor (SRM) is present... more A novel on-line instant torque estimation scheme for a switched reluctance motor (SRM) is presented. In the proposed method, an adaptive B-spline neural network is used to learn the non-linear flux-linkage and torque characteristics of a SRM. Due to the local nature of its generalisation properties, the training of the B-spline neural network is accomplished on-line and in real-time, and the system does not require a priori knowledge of the machine's electromagnetic characteristics. The potential of the method is demonstrated successfully in simulation and experimentally using a 300 W 12/8 3-phase SRM.
The paper examines the relative merits of competing linear motor technologies and topologies for ... more The paper examines the relative merits of competing linear motor technologies and topologies for reciprocating compressor applications. It has been shown that a single-phase, short-stroke, tubular permanent magnet excited motor with a quasi-Halbach magnetized armature and a slotted stator is the most appropriate, due to its high specific force capability and efficiency, its relative simplicity, and the availability of emerging
Direct-drive linear reciprocating compressors offer numerous advantages over conventional counter... more Direct-drive linear reciprocating compressors offer numerous advantages over conventional counterparts which are usually driven by a rotary induction motor via crank shaft. However, to ensure efficient and reliable operation under all conditions, it is essential that the motor current of the linear compressor follows a sinusoidal command profile with a frequency which matches the system resonant frequency. This paper describes a hybrid current controller for the linear compressors. It comprises a conventional proportional-integral (PI) controller, and a B-spline neural network compensator which is trained on-line and in real-time in order to minimize the current tracking error under all conditions with uncertain disturbances. It has been shown that the hybrid current controller has a superior steady-state and transient performance over the conventional carrier based PI controller. The performance of the proposed hybrid controller has been demonstrated by extensive simulations and experiments. It has also been shown that the linear compressor operates stably under the current feedback control and the piston stroke can be adjusted by varying the amplitude of the current command.
This paper considers torque ripple minimisation control for switched reluctance motors (SRMs) and... more This paper considers torque ripple minimisation control for switched reluctance motors (SRMs) and presents a novel on-line approach to the estimation of instantaneous torque. An adaptive B-spline neural network is used to learn the non-linear flux linkage and torque characteristics of an SRM. The training of the B-spline neural network is accomplished on-line in real-time, and the system does not require a priori knowledge of the SRM's electromagnetic characteristics. The potential of the torque estimation method is demonstrated in simulation and experimentally using a 550 W 8/6 four-phase SRM operating in saturation, and it has been applied successfully to torque ripple minimisation.
This paper proposed a DSP controlled 2 kW PFC converter with a novel sampling algorithm which can... more This paper proposed a DSP controlled 2 kW PFC converter with a novel sampling algorithm which can greatly improve switching noise immunity in almost all average current control power supplies. Based on the newly developed DSP chip TMS320F240, a 2 kW PFC stage designed as the front-end of a frequency-variable air-conditioner is implemented. The novel sampling algorithm shows great advantages when the switch operates in the range above 30 kHz
This paper describes alternative winding configurations of a short-stroke, single phase tubular p... more This paper describes alternative winding configurations of a short-stroke, single phase tubular permanent magnet motor for linear compressor applications. Three design variants are considered and analyzed, and their relative merits are evaluated. The open-circuit magnetic field distribution, backemf and thrust force are established analytically, and the results are compared and validated by finite element analysis and experimental measurement on a prototype motor.
ABSTRACT A linear vapor compressor operates most efficiently at resonant frequency which varies w... more ABSTRACT A linear vapor compressor operates most efficiently at resonant frequency which varies with piston stroke and operation conditions. A novel resonant frequency tracking technique is proposed in order to achieve high efficiency operation of a linear compressor system. This is based on the fact that for given amplitude of the motor current, the linear compressor system reaches its maximum stroke and maximum input and output powers at its resonant frequency. By evaluation of the input power to the compressor and implementing a perturb and observe algorithm, the proposed technique can adjust the frequency of the motor current to match the resonant frequency of the compressor operation. The proposed technique does not require a position sensor, and can be easily implemented in a digital controller. Simulation and experimental results have demonstrated the validity of the proposed technique.
A switched reluctance motor torque ripple reduction scheme using a B-spline neural network (BSNN)... more A switched reluctance motor torque ripple reduction scheme using a B-spline neural network (BSNN) is presented. Closed-loop torque control can be implemented using an on-line torque estimator. Due to the local weight updating algorithm used for the BSNN, an appropriate phase current profile for torque ripple reduction can be obtained on-line in real time. It has good dynamic performance with respect to changes in torque demand. The scheme does not require high-bandwidth current controllers. Simulation and experimental results demonstrate the validity of the scheme.
A novel online-modeling scheme for the switched reluctance motor (SRM) using a B-spline neural ne... more A novel online-modeling scheme for the switched reluctance motor (SRM) using a B-spline neural network (BSNN) is proposed in this paper. A 2-D BSNN is designed to learn the nonlinear-flux-linkage characteristic of an SRM online and in real-time. Torque, incremental inductance, and back-emf estimates can be derived from the BSNN after training. The scheme does not require a priori knowledge of the SRM electromagnetic characteristics. Simulation and experimental results show that the scheme has a good estimation performance and robustness at low to medium motor speed.
This paper proposes a novel sampling algorithm for digital signal processing (DSP) controlled 2 k... more This paper proposes a novel sampling algorithm for digital signal processing (DSP) controlled 2 kW power factor correction (PFCs) converters, which can improve switching noise immunity greatly in average-current-control power supplies. Based on the newly developed DSP chip TMS320F240, a 2 kW PFC stage is implemented. The novel sampling algorithm shows great advantages when the converter operates at a frequency above 30 kHz.
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