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ABSTRACT: The sensorless position control of permanent-magnet motors is successfully implemented by superimposing a high-frequency voltage signal on the voltage reference or adding a high-frequency current signal to the current reference. The former approach is usually preferred because of its simplicity, although the latter one may allow better performance. This paper presents a new algorithm for the sensorless control of low-saliency permanent-magnet synchronous motors based on high-frequency sinusoidal current signal injection into the d -axis. Different from the related literature, the position information is derived by analyzing the measured high-frequency currents. The amplitude of the d -axis voltage reference is also exploited to improve performance. A proportional-integral (PI) controller plus a resonant term (PI-RES) is adopted to ensure the accurate tracking of both the dc and high-frequency components of the d -axis current reference. The main advantages of the proposed approach are the increased accuracy and sensitivity with respect to the approach based on voltage injection, the insensitiveness to inverter nonlinearities that are compensated by the current regulation loop, the actual control on the injected current value, and the practical absence of acoustic noise. Experiments on a linear tubular permanent-magnet synchronous motor prototype have been carried out to verify the aforementioned advantages. This paper also presents a discussion of the parameters of the PI-RES.
IEEE Transactions on Industry Applications 07/2011; · 1.66 Impact Factor
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ABSTRACT: Phase-locked loop (PLL) algorithms are commonly used to track sinusoidal components in currents and voltage signals in three-phase power systems. Despite the simplicity of those algorithms, problems arise when signals have variable frequency or amplitude, or are polluted with harmonic content and measurement noise, as can be found in aircraft ac power systems where the fundamental frequency can vary in the range 360-900 Hz. To improve the quality of phase and frequency estimates in such power systems, a novel PLL scheme based on a real-time implementation of the discrete Fourier transform (DFT) is presented in this paper. The DFT algorithm calculates the amplitudes of three consecutive components in the frequency domain. These components are used to determine an error signal which is minimized by a proportional-integral loop filter in order to estimate the fundamental frequency. The integral of the estimated frequency is the estimated phase of the fundamental component, and this is fed back to the DFT algorithm. The proposed algorithm can therefore be considered to be a PLL in which phase detection is performed via a DFT-based algorithm. A comparison has been made of the performances of a standard PLL and the proposed DFT-PLL using computer simulations and through experiments.
IEEE Transactions on Industrial Electronics 04/2011; · 5.16 Impact Factor
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ABSTRACT: The sensorless position control of permanent-magnet (PM) synchronous motors can be successfully implemented by superimposing a high-frequency voltage signal on the control voltage. In this paper, the position estimation is obtained by means of a high-frequency sinusoidal voltage signal injected along the estimated -axis. Several methods proposed in the literature obtain the position estimation by tracking the zero condition of the high-frequency current component. We propose a new approach that also exploits the -axis high-frequency current component and allows working with injected voltage signal of reduced amplitude, thus reducing noise and additional losses. The main contribution of this paper relies in the compensation of the motor end effects due to the finite length of the tubular motor armature. These effects must be taken into account in the motor modeling because they cause an error in the position estimation that varies with the motor position. The modeling of the phenomenon and a proper compensation technique are proposed in this paper. Last, a simplified integral-type controller is used to estimate motor position instead of the commonly adopted proportional-integral controller plus integrator, and this requires a low-effort design. Experiments on a linear tubular PM synchronous-motor prototype are presented to validate the theoretical analysis and evidence the feasibility of the proposed sensorless technique.
IEEE Transactions on Industrial Electronics 03/2011; · 5.16 Impact Factor
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ABSTRACT: This paper proposes the compact differential evolution (cDE) algorithm. cDE, like other compact evolutionary algorithms, does not process a population of solutions but its statistic description which evolves similarly to all the evolutionary algorithms. In addition, cDE employs the mutation and crossover typical of differential evolution (DE) thus reproducing its search logic. Unlike other compact evolutionary algorithms, in cDE, the survivor selection scheme of DE can be straightforwardly encoded. One important feature of the proposed cDE algorithm is the capability of efficiently performing an optimization process despite a limited memory requirement. This fact makes the cDE algorithm suitable for hardware contexts characterized by small computational power such as micro-controllers and commercial robots. In addition, due to its nature cDE uses an implicit randomization of the offspring generation which corrects and improves the DE search logic. An extensive numerical setup has been implemented in order to prove the viability of cDE and test its performance with respect to other modern compact evolutionary algorithms and state-of-the-art population-based DE algorithms. Test results show that cDE outperforms on a regular basis its corresponding population-based DE variant. Experiments have been repeated for four different mutation schemes. In addition cDE outperforms other modern compact algorithms and displays a competitive performance with respect to state-of-the-art population-based algorithms employing a DE logic. Finally, the cDE is applied to a challenging experimental case study regarding the on-line training of a nonlinear neural-network-based controller for a precise positioning system subject to changes of payload. The main peculiarity of this control application is that the control software is not implemented into a computer connected to the control system but directly on the micro-controller. Both numerical results on the test functions and experimental-
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results on the real-world problem are very promising and allow us to think that cDE and future developments can be an efficient option for optimization in hardware environments characterized by limited memory.
IEEE Transactions on Evolutionary Computation 03/2011; · 3.34 Impact Factor
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ABSTRACT: Direct drives with linear motors are attracting the attention of both industry and academia thanks to their advantages in terms of higher precision, higher acceleration/deceleration, and reduced dimensions. This paper presents a comparison between industrial PID controllers and state-of-art non-linear control strategies for accurate position tracking on a linear permanent magnet synchronous motor. Namely, the comparison considers an advanced sliding mode approach with scheduling laws related to the state trajectory in the phase plane, and an approximation-based adaptive scheme that relies on a neural network to cancel the non-linearites of the system so as to have almost linear residual dynamics. The feasibility of the control strategies is validated by an extensive experimental analysis. The schemes are both theoretically stable and guarantee accurate positioning, which are, in terms of average absolute position error, two times better than standard PID.
IECON 2010 - 36th Annual Conference on IEEE Industrial Electronics Society; 12/2010
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ABSTRACT: The sensorless control schemes based on machine saliency detection by signal injection commonly adopt a position observer to estimate the motor position. The position observer usually employs proportional-integral-derivative- (PID-) type controllers and low-pass-filters (LPFs) whose parameters need to be properly tuned to achieve satisfactory, or at least stable, performances. Generally, the position observers are tuned with trial and error procedures that require commissioning time and control design experience. This paper deals with the observer modelling and tuning. In particular, the observer model is used for a model-based position control tuning and the effectiveness of the proposed procedure is confirmed by the good agreement of theoretical and experimental results. The experimental test have been realized using both a linear tubular permanent magnet motor (LTPM) and a rotating internal permanent magnet motor (IPM) to demonstrate that the motor control performances can be predicted only if the observer behaviour is considered.
Energy Conversion Congress and Exposition (ECCE), 2010 IEEE; 10/2010
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ABSTRACT: Direct drives with linear motors have been recently attracting the attention of both industry and academia. The main peculiarity of these systems is the lack of mechanical reduction and transmission devices, which makes the influence of some uncertain electromechanical phenomena (e.g., friction, cogging forces, etc.) and load disturbances much more significant than in the case of conventional rotary actuators. This paper describes a control system for a tubular synchronous linear motor based on a sliding-mode control (SMC) and a proportional-integral (PI)-based equivalent disturbance observer. The distinctive peculiarities of the proposed scheme are the use of a control law that guarantees the stability of the system regardless of the payload mass, the adoption of a double boundary layer addressing effectively the harmful effects of static friction, and the introduction of a simple PI-based equivalent disturbance observer that avoids steady-state errors regardless of model uncertainties and external disturbances. The reduced computational cost of the control law, alongside with the introduction of the effective design criteria for the SMC and the disturbance observer, makes the implementation of the proposed approach as simple as standard cascaded linear control schemes using industrial microcontrollers. The aforementioned considerations are validated by extensive experiments.
IEEE Transactions on Industry Applications 11/2009; · 1.66 Impact Factor
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ABSTRACT: A novel algorithm for fundamental frequency and harmonic components detection is presented in this paper. The technique is based on a real-time implementation of discrete Fourier transform, and it allows fast and accurate estimation of fundamental frequency and harmonics of a distorted signal with variable fundamental frequency. It is suitable for active shunt filter applications, when fast and accurate tracking of the reference signal is required to achieve a good control performance. The main application for the algorithm is aircraft ac power systems, where the fundamental frequency can be either fixed on 400 Hz and its actual value fluctuates around the nominal value, or variable in the range 360-900 Hz. Hence, a real-time estimation of fundamental frequency is essential for active filter control. The proposed algorithm has been at first implemented in Matlab/Simulink for computer simulation, and it has been compared with a Phase Locked Loop (PLL) algorithm for frequency detection and the synchronous dq reference method for harmonic detection. Experimental tests have been carried out in order to validate the simulation results. The distorted current absorbed by a nonlinear load is analyzed and processed by means of a digital implementation of the algorithm running on the active shunt power filter control DSP, in order to calculate the active filter compensating current.
IEEE Transactions on Industrial Electronics 09/2009; · 5.16 Impact Factor
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ABSTRACT: This paper examines an adaptive control scheme for tubular linear motors with micro-metric positioning tolerances. Uncertainties such as friction and other electromagnetic phenomena are approximated with a radial basis function network, which is trained online using a learning law based on Lyapunov design. Differently from related literature, the approximator is trained using a composite adaptation law combining the tracking error and the model prediction error. Stability analysis and bounds for both errors are established, and a report on an extensive experimental investigation is provided to illustrate the practical advantages of the proposed scheme.
American Control Conference, 2009. ACC '09.; 07/2009
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ABSTRACT: The sensorless position control of permanent magnet motors can be successfully implemented by superimposing a high-frequency voltage on the control voltage. The accuracy of the method relies on a fast and accurate signal processing of the measured quantities and on the compensation of the inverter and motor non idealities. In this paper the position estimation is obtained by adding a high-frequency sinusoidal voltage at the output of the d-axis current controller. According to several methods proposed in the literature the position estimation is obtained by minimizing the high-frequency q-axis current. We propose a new approach that also exploits the analysis of the d-axis high-frequency current. Since this current has reasonable amplitude regardless the position estimation error, the proposed approach allows working with injected voltage of reduced amplitude thus reducing noise and additional losses. Moreover a simple I-type controller is used to estimate rotor position and it requires a low-effort design. Experiments on a linear tubular permanent-magnet motor prototype are presented to compare the performances of the considered estimation techniques.
Electric Machines and Drives Conference, 2009. IEMDC '09. IEEE International; 06/2009
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ABSTRACT: Phase locked loop (PLL) algorithms are commonly used to track sinusoidal components in currents and voltage signals in three phase power systems. Despite the simplicity of those algorithms some drawbacks arise when signals have variable amplitude or are polluted with relevant harmonic content and measurement noise. These are typical conditions in aircraft AC power systems, where the fundamental frequency can be variable in the range 360-900 Hz. To improve the quality of phase and frequency estimates in such power systems a novel PLL scheme based on a real-time implementation of discrete fourier transform (DFT) is presented in this paper. The DFT algorithm calculates the amplitudes of three consecutive components in the frequency domain that are used to determine an error signal to be minimized by a PI controller that estimates the fundamental frequency. The integral of the estimated frequency is the estimated phase of the fundamental component that is fed back to the DFT algorithm. The proposed algorithm can be then reviewed as a PLL in which the phase detector is performed via a DFT-based algorithm. A comparison between the performances of standard PLL and the proposed DFT-PLL has been realized using computer simulations and experiments.
Electric Machines and Drives Conference, 2009. IEMDC '09. IEEE International; 06/2009
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ABSTRACT: Direct drives with linear permanent magnet synchronous motors (LPMSMs) are recently attracting the attention of both industry and academia. On the one hand such electric drives permit to reduce size and increase reliability thanks to the lack of mechanical reduction and transmission devices. On the other hand precision positioning requires linear position sensing with a measuring range (and size) equal to the motor allowed travel. It is clear the advantage of sensorless control in such applications in terms of reduced hardware complexity, cost and maintenance requirements. This paper presents a position sensorless control scheme based on high frequency signal injection. A pulsating voltage is superimposed to the control voltage along the estimated d-axis direction. Then a novel demodulation procedure implemented in stationary coordinates is proposed to extract position information. The procedure has a reduced computational cost if compared to the alternatives already proposed in the related literature and requires no tuning effort. A demonstration of the algorithm convergence valid in transient conditions, and a novel method to measure the high frequency motor impedance are also presented. The proposed approach is well suited for motors with reduced magnetic saliency such as tubular LPMSM. The above considerations are validated by extensive experiments.
Industry Applications Society Annual Meeting, 2008. IAS '08. IEEE; 11/2008
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ABSTRACT: Recent research on compact genetic algorithms (cGAs) has proposed a number of evolutionary search methods with reduced memory requirements. In cGAs, the evolution of populations is emulated by processing a probability vector with specific update rules. This paper considers the implementation of cGAs in microcontroller-based control platforms. In particular, to overcome some problems related to the binary encoding schemes adopted in most cGAs, this paper also proposes a new variant based on a real-valued solution coding. The presented variant achieves final solutions of the same quality as those found by binary cGAs, with a significantly reduced computational cost. The potential of the proposed approach is assessed by means of an extensive comparative study, which includes numerical results on benchmark functions, simulated and experimental microcontroller design problems.
IEEE Transactions on Evolutionary Computation 05/2008; · 3.34 Impact Factor
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ABSTRACT: This paper describes a control system for a tubular synchronous linear motor based on a combination of a linear PID controller and a nonlinear neural network. The nonlinear part of the controller is introduced to progressively augment the tracking performance of the system and is trained online by a compact GA. We implement a variant of a known compact GA that well lends itself to practical implementations in low capacity microcontrollers, thanks to its reduced memory requirements and better distributed computational loads. The potential of the proposed approach is assessed by means of a simulation study on a detailed model of a linear motor. The control system obtained through genetic search outperforms alternative schemes obtained with linear design techniques.
Evolutionary Computation, 2007. CEC 2007. IEEE Congress on; 10/2007
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ABSTRACT: A novel algorithm for fundamental frequency and harmonic components detection is presented in this paper. The technique is based on a real-time implementation of discrete Fourier transform and it allows fast and accurate estimation of fundamental frequency and harmonic amplitudes and phases of a distorted and noisy signal with fluctuating fundamental frequency. It is suitable for active shunt filter applications, when fast and accurate tracking of the reference signal is required in order to achieve a good control performance. The main application for the proposed algorithm is for aircraft AC power systems, where the fundamental frequency is 400 Hz and its actual value can fluctuate around the nominal value, hence a real-time estimation of fundamental frequency is essential for accurate active filter control. The proposed algorithm has been first implemented in Matlab/Simulink environment for computer simulation, and then the simulation results have been validated by means of experimental tests on a three-phase system, where a voltage signal generated by a programmable power supply has been analyzed and processed by means of a digital implementation on a microprocessor.
Power Electronics and Applications, 2007 European Conference on; 10/2007
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ABSTRACT: This paper describes the implementation of self-optimizing embedded control schemes for induction motor drives. The online design problem is formulated as a search problem and solved with stochastic optimization algorithms. The objective function takes into account the tracking error, and is directly measured on the hardware bench. In particular, we compare two efficient optimization algorithms, a simultaneous perturbation stochastic approximation method, and a compact genetic algorithm. Both search strategies have very small computational requirements, and therefore can be directly implemented on the same processor running the control algorithm.
Power Electronics and Applications, 2007 European Conference on; 10/2007
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ABSTRACT: Recent research on compact GAs (cGAs) has proposed a number of evolutionary search methods with reduced memory requirements. The cGAs evolve a stochastic description of an hypothetical population processing a probability vector with update rules inspired to the typical selection and recombination operations of a GA. The cGAs well lend themselves to real-time implementations in constrained, low capacity microcontrollers, as they have reduced memory requirements and evenly distributed computational loads with respect to the standard, population- based GA. This paper considers the implementation of cGAs in the same microcontroller used to implement the cascaded control of an induction motor drive. We develop a real-valued version of a cGA that achieves final solutions of the same quality of those found by binary cGAs, with a significantly reduced computational cost. The potential of the proposed approach is assessed by means of an experimental study. The cascaded control system obtained through genetic search outperforms alternative schemes obtained with linear design techniques.
Electric Machines & Drives Conference, 2007. IEMDC '07. IEEE International; 06/2007
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ABSTRACT: This paper describes the implementation of a self- optimizing embedded control scheme for an induction motor drive. The online design problem is formulated as a search problem and solved with a stochastic optimization algorithm. The objective function takes in account the tracking error, and is directly measured on the hardware bench. The online optimization is performed with the simultaneous perturbation stochastic approximation (SPSA) algorithms, which offer a very effective tradeoff between simplicity of implementation, speed of convergence and quality of the final solutions. Among the known SPSA algorithms considered in this paper, we also propose a novel variant inspired to the concept of elitism frequently used in evolutionary computation. To assess the relative performances of the various algorithms, the paper carries out a comprehensive analysis of a control scheme for an induction motor drive subject to time-varying load disturbances.
Electric Machines & Drives Conference, 2007. IEMDC '07. IEEE International; 06/2007
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ABSTRACT: This paper describes the design of a new fuzzy logic-based navigation algorithm for autonomous robots. This design effectively achieves correct environment modeling and noisy and uncertain sensory data processing on low-cost hardware equipment. A hierarchical control strategy is presented in which three different reactive behaviors are fused in a single control law by means of a fuzzy supervisor guaranteeing robot safety and task accomplishment. Due to the inherent transparency of fuzzy logic, the proposed algorithm is computationally light, easily reconfigurable, and well-performing in a wide range of differing operating conditions and environments
IEEE Robotics & amp amp Automation Magazine 01/2007; · 1.99 Impact Factor
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ABSTRACT: This paper describes a design procedure for a cascaded control system of induction motors based on compact genetic algorithms (cGAs). CGAs are search methods that process a probability vector (describing the distribution of a hypothetical population) with update rules inspired to the typical selection and recombination operations of a GA. The cGAs well lend themselves to real-time implementations in constrained, low capacity microcontrollers, as they have reduced memory requirements and evenly distributed computational loads with respect to the standard, population-based GA. This paper investigates the applicability of a cGAs selected from literature to simultaneously optimize the couple of position and speed controllers using a weighted cost function that combines indices about position, speed, and current responses. The search is performed on-line, iteratively experimenting new solutions directly on the induction motor drive. The cascaded control system obtained through genetic search outperforms alternative schemes obtained with linear design techniques
IEEE Industrial Electronics, IECON 2006 - 32nd Annual Conference on; 12/2006
