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Robust estimator design for signal injection-based IPM synchronous machine drives
Abstract
This paper analyzes the design choices taken when designing a carrier-signal-based self-sensing position and speed estimation strategy for IPM drives. The balance between the noise generation and the load disturbance rejection process is analyzed, since this balance is essential for robustness. An extended closed loop observer is introduced to improve robustness during load changes, and guidelines for choosing bandwidth for filters is given. A scalar current observer is essential for robust elimination of the fundamental component. An improved structure for the observer is presented and discussed, which improves the impact from transients from the BSF filters.
... Therefore, more or less complex signal filters with a fixed cut-off frequency, e.g. Bandpass or bandstop filter, are required to separate this anisotropic current sequence [11,12]. The necessary signal filters also reduces the phase margin of closed control loops. ...
... In contrast to the fundamental wave model, the flux linkage equation of the HF-model (11) does not contain any flux component cased by the permanent magnetic field. Therefore, the flux linkage of the HF-model « c;˛ˇo nly derive from inductance influences. ...
In this paper a new rotor position observer for permanent magnet synchronous machines (PMSM) based on an Extended-Kalman-Filter (EKF) is presented. With this method, just one single EKF is sufficent to evaluate the position information from electromotive force (EMF) and anisotropy. Thus, the PMSM can be controlled for the entire speed range without a position sensor and without the need to switch or synchronize between different observers. The approach covers online estimation of permanent magnetic field and mechanical load. The resulting EKF-based rotor position estimator is embedded in the existing cascaded control concept of the PMSM without need of additional angle trackers or signal filters. The experimental validation for the position sensorless control shows optimized dynamic behaviour.
... This is because of the low dynamic performance of the current filter, which is utilized to extract the negative sequence current from the measured current in the conventional HFI method [3,[21][22][23][24]. Therefore, an observerbased current filter [21,25] is adopted in the proposed method to improve the dynamic performance of speed estimation. Then, the disturbance of the negative sequence current caused by the fundamental current pulses is effectively suppressed, and the accuracy of momentary speed estimation is greatly improved. ...
... However, the HF negative-sequence current is distorted by the harmonic components inside the fundamental pulse current when using the conventional current filter to separate the fundamental current and HF negative-sequence current during current pulse injection, resulting in huge errors in the estimated position and speed. In order to improve the dynamic performance, a current-observer-based current filter [21,25] is adopted here to replace the conventional subtraction-based current filter in the HFI method. Its simplified diagram is shown in Figure 6. ...
Referring to the sensorless control of interior permanent magnet synchronous motor (IPMSM), the initial rotor polarity is normally estimated based on the motor saturation effect. However, for certain special IPMSMs, the saturation effect is weak even at the rated point, making the saturation-based rotor polarity detection methods invalid. Therefore, this paper proposes a novel rotor polarity detection method based on torque-pulse injection. Two current pulses are imposed on the positive and negative directions of the q-axis estimated by the high-frequency injection (HFI) method, respectively; the signs of speed peaks indicate the rotor polarity. To derive the rotor polarity from the tiny speed signal, a new speed estimation method is presented. To improve the dynamic performance of speed estimation, a special current filter is adopted in the HFI method. To choose the proper width and amplitude of the current pulse under different load and inertia conditions, an automatic program is designed. The proposed method has the advantages of high accuracy, short identification time, tiny movement, and automatic operation, making it applicable to various load and inertia conditions. The effectiveness of the proposed method is validated by experiments on an IPMSM with low saturation effect.
... After normalizing the interpolated position quadrature signal, the rotor position error is obtained through the quadrature phase-locked loop, and then the estimated rotor position θ e and mechanical angular velocityω r are calculated by the Luenberger observer. The principle of the Luenberger observer is detailed in [30,31]. The general control delay varies from 0.75T PWM to 2T PWM depending on the current update-sampling processing method. ...
... After normalizing the interpolated position quadrature signal, the rotor position error is obtained through the quadrature phase-locked loop, and then the estimated rotor position ˆe and mechanical angular velocity ˆr are calculated by the Luenberger observer. The principle of the Luenberger observer is detailed in [30,31]. The general control delay varies from 0.75TPWM to 2TPWM depending on the current update-sampling processing method. ...
The high-frequency (HF) square-wave voltage injection method can be used in permanent magnet synchronous motor (PMSM) drive systems. However, when the switching frequency is too low, the injection frequency will also decrease, which will reduce the update frequency of the HF response current, making it difficult to extract the position quadrature signal and affecting the accuracy of position estimation and control performance. This paper proposes a method for extracting position quadrature signals based on sampling rate transformation, and a signal processing strategy based on Cascade Integrator Comb (CIC) interpolation filtering, which can solve the problem of waveform distortion caused by the low sampling rate of the extracted position quadrature signal. This strategy can increase the sampling rate of the position quadrature signal to the pulse width modulation (PWM) update frequency by interpolating in the sampling current, thereby reducing the harmonic content of the position quadrature signal and improving the position estimation. precision. In addition, the PWM update frequency and estimated rotational speed information are used to compensate for the delay caused by position estimation and inverter update, which effectively improves the accuracy of position estimation. Finally, the effectiveness of the proposed control strategy is verified by simulation.
... Sensorless algorithms for sinusoidal control of AC machines can be broadly divided into two major groups; 1) those that utilize magnetic saliency for tracking rotor position [2]- [12] and 2) those that estimate rotor position from calculated motor model [8], [13]. The later, requires accurate knowledge of phase voltages and current for proper functionality. ...
... Reluctance in q-axis direction is smaller than that one in d-axis, resulting in q-axis inductance bigger than d-axis; L d Ͻ L q . Therefore, in order to develop maximal torque according to (2), reluctance torque should be utilized, i.e. i d current has to be adjusted to negative values, weakening the resulting magnetic field. On the other hand, the armature reaction effects are dominant, due to small effective air-gap, resulting in saturation of q-axis inductance according to the level of applied load. ...
This paper presents a complex solution for whole speed range sensorless control of interior permanent magnet synchronous motor drives. To cover an entire speed range of IPMSM without position transducer, different sensorless techniques must be employed. Design and implementation of sensorless techniques for different operating speeds are described in this paper. Presented application has been implemented including the high frequency (hf) injection method and extended back EMF state observer on a single chip solution of DSC56F8300 series without any additional supportive circuitry. The extended back EMF algorithm with angular speed and position observer is suitable for sensorless control drive. It is also transferable for other motor types, e.g. synchronous reluctance- or synchronous one with 'smooth ' rotor. The presented sensorless control has been proved in electric washer drive with very good operating properties.
... State estimation and control of permanent magnet brushless DC (BLDC) motors has been an important research area from the past several decades. BLDC motors and drives are widely used in industries due to their high efficiency and high power density [1][2][3][4][5][6][7]. Several control strategies have been proposed and implemented on BLDC drives. ...
This paper presents a non-linear square-root estimation scheme for brushless DC (BLDC) motors. The cubature Kalman filter (CKF) is the main estimation tool for the presented approach. The CKF is a recently proposed estimator for highly non-linear systems and its efficacy has been verified on several applications. The square-root version of the CKF is preferred over the conventional CKF for real-time applications. Despite of having several advantages over other non-linear filters, the CKF has not yet been explored for state estimation of electric drives in the electric drives community. In this study, the authors present a square-root CKF for the speed and rotor position estimation of a highly non-linear and high fidelity BLDC motor, these estimated speed and rotor position are then fed back to control the speed of the BLDC motor. The efficacy of the presented approach for low and high reference speeds, and in the presence of parametric uncertainties, is demonstrated by real-time experiments.
... e., α-axis and β-axis) at the same time. Then by using filters with the phase-locked loop (PLL) method it is possible to separate the two inductive signals and calculate the rotor position and speed from the sine and cosine components conveniently [9][10][11] . The two signals have different frequencies and different phases. ...
This paper proposes a sensorless control approach for Wound Rotor Synchronous Machines (WRSMs) based on a high frequency voltage signal injection into the stator side U phase and VW line, respectively. Considering the machine itself as a rotor position sensor, the rotor position observer is established according to the principles of the rotary transformer. A demodulation method for the high frequency signal inducted in the rotor is proposed as well. Simulation and experimental results show that the proposed sensorless control approach has high performance and good practicability.
The linear extended state observers (LESOs) have been widely employed in the saliency-based sensorless control of interior permanent magnet synchronous motor (IPMSM) drives for position and speed tracking. The performances of the LESO are mainly determined by its bandwidth. This paper focuses on the bandwidth determination of the third-order (3
rd
)-LESOs used in saliency-based sensorless control. A generic method for determining the bandwidth of the 3
rd
-LESO is proposed by means of the open-loop transfer function, by which both the position and speed tracking performances can be further revealed. The desired bandwidth can be roughly achieved by adjusting the natural frequency and subsequently precisely tuned via two damping factors for the specific application of sensorless control. Subsequently, general guidelines of the bandwidth determination are proposed and summarized. Moreover, an intuitive and improved fourth-order (4
th
)-LESO, which is extended from the conventional 3
rd
-LESO, is proposed and comprehensively analyzed for its application in the sensorless control. Compared with the conventional 3
rd
-LESO, the proposed 4
th
-LESO exhibits improved capability of the high frequency noise rejection and thus it is a promising candidate for the saliency-based sensorless control. Finally, all the theoretical analyses are verified experimentally on a 1-kW IPMSM drive.
This paper analyzes the effect of angle estimation error on the sensorless torque control of the permanent-magnet synchronous motor (PMSM). The actual torque of PMSM may differ from the torque reference due to the angle error in sensorless control. Furthermore, this torque discrepancy can cause instability to the control system, especially in the flux weakening region. The instability is highly dependent on the gain setting of the controller and observer in the control loop. To mitigate the adverse effect of the angle error, a torque feedforward method considering the transient angle error is proposed. With the proposed torque feedforward method, the gain margin of the control loop can be enhanced without modifying the gain of the control system. The proposed method is verified through the simulation and experimental results.
HF signal injection method can obtain the rotor position accurately by tracking the rotor saliency at low and zero speed. However, this method arouses the high-frequency component in the induced current, causing audible noise and electromagnetic interference (EMI) problems. The audible noise generated by injected HF signals is uncomfortable to hear, which inevitably restricts the implementation of this kind of sensorless control scheme in industrial and household applications. Adopting the idea of noise reduction in power converters, random HF signal injection method is a good way for noise suppression.
The conventional high frequency (HF) voltage injection method can accurately extract rotor position for interior permanent magnet synchronous motor (IPMSM) drives at low and zero speed ranges. However, the fixed injection frequency will produce a loud audible noise. To solve this problem, a pseudo-random phase-switching fixed-frequency (PRPSFF) signal injection method is proposed in this paper. Based on the principle of phase selection for the PRPSFF injection scheme, the DC bias problem in the induced HF current can be diminished by setting a limitation in the injected voltage. Then a corresponding signal processing method is investigated to deal with the signal delay in the HF current extraction. Besides, the current power spectra density (PSD) for PRPSFF injection is analyzed, and a comparison between PRPSFF and the pseudo-random frequency-switching fixed-phase (PRFSFP) injection schemes is also introduced. The results show that the discrete harmonic spectrum in current PSD can be offset, and the continuous spectrum is smoother than that of PRFSFP injection. Finally, the effectiveness of the sensorless control method is verified by experiments on a 2.2-kW IPMSM drive platform.
The paper deals with combined real-time model of PM synchronous motor for sensorless position control in the field of robotic systems. Real-parametric-and real-time model could be ideal tools for both control and simulation of the PMSM position drive. Unfortunately that idealized model doesn't exist so far. Such a model has to face following serious problems: it must be excited and synchronized by real input including non-linearities of power supply converter (switch voltage drops, dead-times,..); it should also provide on-line identification of the motor parameters including load changes. Combine real-time model proposed in the paper fulfills most of those requirements: it is supplied by real data from the motor stator voltages, so it is exactly synchronized with real system, and it works with off-line identified motor parameters.
The paper deals with real-time control of PM synchronous motor for sensorless position using Power PC-MPC processor. Real parametric-and real-time model could be ideal tools for both control and simulation of the PMSM (permanent magnet synchronous motor) position drive. Unfortunately that idealized model doesn't exist so far. Such a model has to face following serious problems: it must be excited and synchronized by real input including non-linearities of power supply converter (switch voltage drops, dead-times,..); it should also provide on-line identification of the motor parameters including load changes. Combine real-time control system proposed in the paper fulfills most of those requirements: it is supplied by real data from the motor stator voltages, so it is exactly synchronized with real system, and it works with off-line identified motor parameters.
The work presented in this paper deals with the issues in practical implementation of the high-frequency injection methods for control of IPM machines without shaft position sensors. Implementing a high-frequency injection technique for rotor position estimation requires intense signal processing of the measured currents as well as the filtering of the signals to extract the rotor position information. These tasks turn in complicate control algorithm, but more importantly degrade the overall system performance by introducing delays, increasing response times and decreasing the bandwidth of the controller. Moreover some specific filtering techniques limit the operation of the machines to the very narrow operating range. These issues and their specific effects are discussed in this paper and mitigation procedures are proposed, implemented and verified through the experimental setups. Experimental results of a new high-performance controller without rotor position sensors are presented as well. The major contribution of this work is a new controller based on the high-frequency injection method that eliminates the need for low-pass filtering and improves the performance of the machine.
The paper deals with combined real-time model of PM synchronous motor for sensorless position control. Real-parametric-and real-time model could be ideal tools for both control and simulation of the PMSM position drive. Unfortunately that idealized model doesn't exist so far. Such a model has to face following serious problems: it must be excited and synchronized by real input including non-linearities of power supply converter (switch voltage drops, dead-times,..); it should also provide on-line identification of the motor parameters including load changes. Combine real-time model proposed in the paper fulfills most of those requirements: it is supplied by real data from the motor stator voltages, so it is exactly synchronized with real system, and it works with off-line identified motor parameters.
The paper presents a position sensing method for IPM motors based on an observer referring to the estimated frame of reference, eliminating problems with position dependent inductances. Convergence of the estimation error to zero is proofed, under the assumption that the mechanical time constant is much larger than the electrical one. The observer can be used right from startup to rated speed, so bump from a startup strategy is avoided. In order to verify the observer experiments have been performed
This paper presents a complex solution for whole speed range sensorless control of interior permanent magnet synchronous motor (IPMSM) drives. To cover an entire speed range of IPMSM without position transducer, different sensorless techniques must be employed. Design and implementation of sensorless techniques for different operating speeds are described in this paper. Presented application has been implemented including the high frequency (hf) injection method and extended back EMF state observer on a single chip solution of DSC56F8300 series without any additional supportive circuitry
High frequency carrier injection is a promising approach solving high performance sensorless drive demands. Position control at low and zero speed is only possible using anisotropic effects considered in high-frequency models. The usually open loop carrier signal injection is impacted by nonlinear inverter properties like the dead-time effect. This paper discusses the influence of the dead time effect on the carrier signal excitation comparing alternating and revolving injection principles. To overcome disturbing effects an alternating injection procedure is proposed using a predefined injection angle. The approach reduces the effects of the inverter distortion voltages. As a result it is possible to track even small saliencies typical for surface mounted permanent magnet synchronous machines. For processing the high frequency current for position estimation, there is no additional hardware necessary within a standard drives with field oriented control. The paper presents theoretical analysis and experimental results.
An analysis of pulsewidth-modulation inverter nonlinearities influencing high-frequency carrier-signal voltage injection for saliency-tracking-based rotor/flux position estimation is presented in this paper. Distortion of the injected carrier voltage caused by the nonlinear behavior of the inverter has been reported to cause errors in the estimated rotor/flux position. Though a number of techniques have been developed to compensate for inverter nonlinearities, they have not been proven to be effective when a high-frequency low-magnitude voltage needs to be generated. Both the origins of the distortion as well as the requirements for compensation methods to be effective when producing such high-frequency voltages will be established in this paper.
This paper presents an improved method to estimate rotor motion states for an interior permanent-magnet machine drive. This approach is based on the estimation of a saliency-based electromotive force (EMF) in the stationary reference frame using a state filter. The spatial information obtained from the estimated saliency-based EMF is used in an observer to estimate the motor motion states. By using the commanded torque as a feedforward input to the observer, the motion state estimation has zero-phase lag, providing a very-high-bandwidth estimate.
This paper analyzes the dynamic operation of carrier-signal-based
sensorless field-oriented AC motor drives. The effects of the harmonics
introduced by the fundamental current transients at frequencies near the
carrier-signal frequency are first analyzed, then compensation based on
a fundamental current observer is proposed. The utilization of such a
fundamental current observer provides the possibility of modifying the
analog-to-digital conversion process to increase the number of bits
effectively containing spatial information and thereby substantially
increasing the accuracy of the estimated rotor position or flux angle
This paper presents a method using carrier frequency injection to estimate the initial rotor position and magnet polarity for an interior permanent magnet synchronous machine. A non-saturating inductance model of the machine provides no information about the polarity of the rotor magnet because the position observer based on this model is locally stable at both poles. To distinguish the polarity of the rotor magnet, the magnetic saturation effect can be used. A 2nd order Taylor series can be used to describe the nonlinear magnetic saturation relationship between the current and the flux linkage in the d-axis rotor reference frame. The 2nd order term produces the 2nd harmonic component of the carrier frequency, and the sign of its coefficient identifies the polarity of the rotor magnet being tracked. Both simulation and experimental results show good response of the position observer at rotor electrical positions of ±0.5π rad using either a rotating vector in the stationary reference frame or a pulsating vector in the estimated rotor reference frame.
In the presented paper the practical realization of a position sensorless biaxial positioning system based on industrial permanent magnet synchronous motor (PMSM) drives is introduced. At low speed including standstill the INFORM-method is used for sensorless position estimation, at high speed an EMF-based short circuit model is applied. With the help of a proper control structure and a corresponding implementation in the DSP the standard deviation of the estimated rotor position is just about 3-5 degrees (el.) at both models, resulting in a linear position resolution of about 0.05 mm in the presented application. In order to reduce the costs of the drive and to increase its reliability once more the energy consumption at generating mode is implemented without any additional hardware just by a slightly modified control structure. As a result a highly dynamic low-cost sensorless position control with a positioning accuracy of about 3-5° el. is practically realized.
Current regulators for interior permanent magnet machines have unique challenges if high performance torque regulation is to be achieved. This paper presents a novel approach for fully decoupling the problematic cross-coupling with estimated parameters from online self-tuning. In the on-line estimation algorithm, the model is formulated such that cross-coupled estimated parameters are eliminated, which improves the parameter estimation robustness. Parameter estimation is further improved by combining the model with a closed loop observer. Cross-coupling terms can then be decoupled using estimated parameters to improve the performance of the current regulator.
The increasing use of AC machines compared to DC motors in
electrical drive applications has several reasons. A very important
advantage of AC machines is their simple construction. However, AC
drives often need mechanical sensors (tachometers, position encoders)
for field orientation. In many applications these sensors reduce
robustness and increase costs of a drive considerably. The main
objective of this paper is to present the “INFORM” method
based on real-time inductance measurements for sensorless control of AC
drives
This paper addresses self-sensing (“sensorless”)
control of salient-pole permanent magnet synchronous motors (PMSMs). The
major contribution of this work is the introduction of a
simple-to-implement estimation technique that operates over a wide speed
range, including zero speed. The technique achieves simplicity by
decoupling the inherent cross-coupling in PMSMs. The technique utilizes
the dependence of inductance on rotor position in interior permanent
magnet machines to produce position and velocity estimates both for
field orientation and for all motion control of the drives. The
technique functions in a manner similar to a resolver and
resolver-to-digital converter (RTDC) sensing system, whereby in the
proposed technique the motor acts as the electromagnetic resolver and
the power converter applies carrier-frequency voltages to the stator
which produce high-frequency currents that vary with position. The
sensed currents are then processed with a heterodyning technique that
produces a signal that is approximately proportional to the difference
between the actual rotor position and an estimated rotor position. This
position error signal and a torque estimate are then used as inputs to a
Luenberger style observer to produce parameter insensitive, zero lag,
position and velocity estimates
This paper presents a viable transducerless rotor position and
velocity estimation scheme for PWM inverter driven induction,
synchronous, and reluctance machines with the capability of providing
robust and accurate dynamic estimation independent of operating point,
including zero and very high speeds, light and heavy loading. The
injection of a balanced three-phase high frequency signal (500 to 2 kHz)
generated by the inverter, followed by appropriate signal demodulation
and processing combined with a closed-loop observer, enable the tracking
of rotor magnetic saliencies from the machine terminals. Although rotor
magnetic saliency is inherent within reluctance machines, and most
synchronous machines, saliency in the induction machine is introduced
via a modulation of the rotor slot leakage with minimal detrimental
effects on the machine performance. Experimental verification for the
induction machine is included