Self-sensing Control Research Articles

A Back-EMF Threshold Self-Sensing Method to Detect the Commutation Instants in BLDC Drives

By predicting future phase-current commutation instants of brushless dc (BLDC) machines, self-sensing control is achieved. Detection of the back electromotive force (EMF) zero-crossing moments is one of the methods used to predict the phase-current commutation instants. Most of the techniques based on back-EMF zero-crossing detection have the inherit disadvantage of an indirect prediction of commutation instants. This is the result of the commutation instant occurring at the $30^{\circ}$ electrical position after zero-crossing of the induced back-EMF in the unexcited phase. Often, the time difference between the zero-crossing of the back-EMF and the current commutation instant is assumed constant. This assumption can be valid for steady-state operation; however, a different time span should be taken into account during transient operation of the BLDC machine. To overcome this problem, an enhancement is proposed here, which improves the performance while keeping the simplicity of the back-EMF zero-crossing detection method.

HF Test Current Injection-Based Self-Sensing Control of PMSM for Low- and Zero-Speed Range Using Two-Degree-of-Freedom Current Control

This paper deals with an innovative self-sensing control scheme based on test current instead of voltage injection. Using two-degree-of-freedom current control, one can overcome the bandwidth limitations that made test current injection unattractive during the last 20 years. The two-degree-of-freedom control scheme consists of a model-based dynamic feedforward control to set the reference response and model reference tracking controllers providing disturbance rejection and position error signals for self-sensing control. Since two-degree-of-freedom control is a model-based control scheme, the compensation for secondary saliencies is inherently included in the precontrol. It is analytically shown that, in the case of alternating test current instead of voltage injection, just the precise knowledge, in general, of the current- and position-dependent secondary diagonal element of the inductance matrix is needed in the case of inductance saliency-based self-sensing control. The effectiveness of the proposed method is proven by experimental results.

Self-sensing control of piezoelectric positioning stage by detecting permittivity

Piezoelectric displacement contains hysteresis and creep properties. Therefore, a displacement sensor is indispensable in precise positioning devices; however, the additional space and cost are problems. On the other hand, self-sensing methods that utilize the piezoelectric actuator itself as the displacement sensor have been proposed. With these self-sensing methods, precise positioning becomes possible without an additional displacement sensor. We developed a self-sensing method utilizing the non-hysteresis relationship between the permittivity change and the piezoelectric displacement. Furthermore, a differential current measurement method using two piezoelectric elements with a bimorph actuator could improve the positioning accuracy. In this study, we examine the control of a positioning stage using two multilayered piezoelectric actuators by applying the differential current measurement method for self-sensing control. The results indicate that the differential current measurement method is effective for precise positioning control. The positioning errors due to hysteresis decreased from 0.8μm to 0.1μm for a 10μm displacement range. In addition, permittivity feedback control could compensate for the creep property.

2A2-A10 太径SMAワイヤの抵抗値制御と移動ロボットへの応用

SMA actuators have light-weight and big power, and especially their powers and strengths of thickened it are increased and then Self-sensing control become more difficult by their electric resistance decreased. SMA actuators have big force to weight ratio. When it is heated and the temperature reaches the transformation point, the phase changes from martensite to austenite and the length and the electric resistance decreases. We can control the displacement of SMA by managing the electric resistance. Thicker SMA has smaller electric resistance, so the control is more difficult. We try to establish accurate control of the thick SMA actuator and application it to mobile robots.

Performance analyses of antagonistic shape memory alloy actuators based on recovered strain

In comparison with conventional shape memory actuated structures, antagonistic shape memory alloy (SMA) actuators permits a fully reversible two-way response and higher response frequency. However, excessive internal stress could adversely reduce the stroke of the actuators under repeated use. The two-way shape memory effect might further decrease the range of the recovered strain under actuation of an antagonistic SMA actuator unless additional components (e.g., spring and stopper) are added to regain the overall actuation capability. In this paper, the performance of all four possible types of SMA actuation schemes is investigated in detail with emphasis on five key properties: recovered strain, cyclic degradation, response frequency, self-sensing control accuracy, and controllable maximum output. The testing parameters are chosen based on the maximization of recovered strain. Three types of these actuators are antagonistic SMA actuators, which drive with two active SMA wires in two directions. The antagonistic SMA actuator with an additional pair of springs exhibits wider displacement range, more stable performance under reuse, and faster response, although accurate control cannot be maintained under force interference. With two additional stoppers to prevent the over stretch of the spring, the results showed that the proposed structure could achieve significant improvement on all five properties. It can be concluded that, the last type actuator scheme with additional spring and stopper provide much better applicability than the other three in most conditions. The results of the performance analysis of all four SMA actuators could provide a solid basis for the practical design of SMA actuators.

Position Self-Sensing Evaluation of Novel CW-IPMSMs With an HF Injection Method

This paper introduces two different novel designs of interior permanent-magnet synchronous machines with concentrated windings, which are attractive to a self-sensing control system. The new machines have some advantages: lower subharmonics of air-gap flux density and magnetomotive force and lower machine losses, including eddy current losses. The machines have been adapted for self-sensing applications by using a high-frequency (HF) injection method. The main machine parameters affecting the estimation accuracy are analyzed such as fundamental frequency saliencies, cross saturation, HF inductance, HF resistance, and harmonic distortion due to multisaliencies. The experimental results verify that the novel machines can reach very high performance with good self-sensing properties regarding the accuracy of the estimated position/speed of electric drives even without the multisaliency decoupling compensation method.

Technique for Magnetic Bearing Based on Mixed-Kernel Support Vector Machine Forecasting Model

The self-sensing magnetic bearing can reduce the cost and the axial size of the magnetic bearing and increase its reliability. A mixed-kernel least squares support vector machines (LS-SVM) forecasting model is proposed for self-sensing technique of a hybrid magnetic bearing. The structure and mathematical model of the radial-axial hybrid magnetic bearing are introduced. Based on the principle of the mixed-kernel LS-SVM, the nonlinear forecasting model between the current and the displacement which realizes the displacement self-sensing control is built through genetic algorithm. Simulation has done to verify the validity and feasibility of proposed method.

Study on Wavelet De-Noising of High Frequency Current Signal for Rotor Position Self-Sensing of PMSM

Self-sensing control of permanent magnet synchronous motor has been a hot research topic of motor control technology, which has the advantages of low cost and high reliability. The use of a high-frequency carrier signal superimposed on the fundamental excitation of PMSM has established itself in recent years as a viable means of eliminating position sensors in ac drives for applications. In the carrier signal injection methods, the rotor position can be estimated by using the carrier signal current resulting from the interaction between the carrier signal voltage and the spatial saliency. The existing sampling error and random noise of high frequency current signal were uncertain to the rotor position self-sensing, that may affect the rotor position self-sensing precision. This paper describes a new wavelet de-noising method of the high-frequency current signal, improving the de-noising results significantly.

Self-Sensing Control of Nafion-Based Ionic Polymer-Metal Composite (IPMC) Actuator in the Extremely Low Humidity Environment

This paper presents feedforward, feedback and two-degree-of-freedom control applied to an Ionic Polymer-Metal Composite (IPMC) actuator. It presents a high potential for development of miniature robots and biomedical devices and artificial muscles. We have reported in the last few years that dehydration treatment improves the electrical controllability of bending in Selemion CMV-based IPMCs. We tried to replicate this controllability in Nafion-based IPMC. We found that the displacement of a Nafion-based IPMC was proportional to the total charge imposed, just as in the Selemion-CMV case. This property is the basis of self-sensing controllers for Nafion-based IPMC bending behavior: we perform bending curvature experiments on Nafion-based IPMCs, obtaining the actuator's dynamics and transfer function. From these, we implemented self-sensing controllers using feedforward, feedback and two-degree-of-freedom techniques. All three controllers performed very well with the Nafion-based IPMC actuator.

C-1-3 Adaptive feed-forward cancellationに基づくセルフセンシング・モデルフリー振動制御(情報・精密機器のサーポ・スマート制御,口頭発表)

C-1-3 Adaptive feed-forward cancellationに基づくセルフセンシング・モデルフリー振動制御(情報・精密機器のサーポ・スマート制御,口頭発表)

B34 LQG制御則に基づくセルフセンシングモデルフリー振動制御(M-OS3-1 制御/センシング,M-OS3 スマート構造システム,「海を越え,国を越え,世代を超えて!」)

B34 LQG制御則に基づくセルフセンシングモデルフリー振動制御(M-OS3-1 制御/センシング,M-OS3 スマート構造システム,「海を越え,国を越え,世代を超えて!」)

Comparison of resistance-based and inductance-based self-sensing controls for surface permanent-magnet machines using high-frequency signal injection

This paper presents injection-based self-sensing (position sensorless) control methods for surface permanent magnet (SPM) machines with concentrated windings (CWs) and distributed windings (DWs). Two position-dependent spatial saliency signals are compared. The two signals relate to resistance variation due to high-frequency eddy current losses and to inductance variation due to stator tooth saturation. Finite-element analysis is performed to investigate the properties of two saliency signals in different SPM machines. Implementation methods, as well as advantages for closed-loop control, are discussed. This paper includes experimental evaluation of resistance-based versus inductance-based self-sensing control performance in SPM machines with CWs and DWs.

Active Vibration Control of a Microactuator for the Hard Disk Drive Using Self-Sensing Actuation

This paper presents the self-sensing control of a microactuator for hard disk drives. The microactuator uses a PZT actuator pair installed on the suspension assembly. The self-sensing microactuator forms a combined sensing and actuation mechanism. Direct velocity feedback and positive position feedback are used in this paper. Our experimental results show that both strategies are effective in suppressing vibrational modes and successfully demonstrate the feasibility of using a self-sensing actuator on an HDD suspension assembly.

Surface Permanent-Magnet Machine Self-Sensing at Zero and Low Speeds Using Improved Observer for Position, Velocity, and Disturbance Torque Estimation

This paper proposes an improved method for the estimation of position, velocity, and disturbance torque in a surface permanent-magnet (SPM) machine self-sensing (position sensorless) drive that uses high-frequency (HF) voltage injection. SPM machines traditionally do not have enough position-dependent signals because their symmetric rotors result in near-zero spatial saliency. A separate disturbance observer and a saliency-tracking observer with speed-varying bandwidth (BW) tuning are used together to improve the disturbance rejection performance while maintaining the accuracy of self-sensing position and velocity estimation. According to the experimental evaluation, the proposed estimation method can achieve higher BW for the disturbance estimation and decoupling which can increase the stiffness of SPM machine closed-loop self-sensing control. This paper includes experimental comparative evaluation of closed-loop encoder-based versus closed-loop self-sensing-based operation of a SPM machine drive.

J044102 適応型セルフセンシング圧電アクチュエータを用いたスマート構造の振動制御

A self-sensing actuator is known to be effective in vibration control of flexible structures. Currently, a seif-sensing piezoelectric actuator is implemented by using a tuned bridge circuit. This circuit easily becomes unbalanced because of the variation of the piezoelectric capacitance which is sensitive to ambient temperature, and it causes the closed-loop system instability. In this study, an adaptive self-sensing control with an EKF (Extended Kalman Filter) is proposed to estimate the unknown capacitance value. The results of numerical simulations show that the present method estimates the unkown parameter with sufficient accuracy and guarantees the system safety.

Novel Design of Flux-Intensifying Interior Permanent Magnet Synchronous Machine Suitable for Self-Sensing Control at Very Low Speed and Power Conversion

This paper proposes a new rotor design for flux-intensifying interior permanent magnet synchronous machine (FI-IPM SM) that is more suitable for self-sensing control at zero/very low speed based on saliency-tracking methods and retains acceptable power conversion capability as compared to a traditional flux-weakening IPM SM (FW-IPM SM). Design steps for the rotor structure of the new machine are laid out and discussed to emphasize key design challenges. The proposed FI-IPM SM and a conventional FW-IPM SM with similar torque-speed capability are made to evaluate performances in power conversion as well as self-sensing capability at very low speed. Finite-element analysis (FEA) is used to evaluate each machine's performance. The proposed FI-IPM SM shows less variation in the saliency when the machine is loaded, leading to a possibility of better self-sensing performance at very low speed as compared to the traditional FW-IPM SM. Experimental results on the efficiency and self-sensing performance of these two machines are presented to verify the design methodology.

Surface-Permanent-Magnet Synchronous Machine Design for Saliency-Tracking Self-Sensing Position Estimation at Zero and Low Speeds

Elimination of externally mounted position sensors and their associated cables is a goal for drive manufacturers. This paper addresses design methods of surface-permanent-magnet (SPM) synchronous machines for saliency-tracking self-sensing (position sensorless) position estimation. Machine spatial saliency is created by stator magnetic saturation due to the rotor zigzag leakage flux from SPMs. Using the machine saliency created by zigzag leakage flux can allow an SPM machine to be suitable for saliency-tracking position estimation without the need of any special rotor design modification. In addition, another major benefit is achieved, i.e., a saliency role reversal whereby L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> >; L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</sub> . This has the advantage of reducing machine cross-saturation and increasing the feasible region for closed-loop self-sensing control. All the design procedures are verified by the finite-element analysis, and a 50-W SPM machine is used for experimental evaluation.

High-precision positioning using a self-sensing piezoelectric actuator control with a differential detection method

We present a self-sensing control method for piezoelectric actuators, which enables high-resolution positioning without an external positioning sensor. One of the present authors previously proposed a self-sensing piezoelectric actuator control system (Kawamata et al. (2008) [1] and Ishikiriyama and Morita (2010) [2]). In the previous studies, a linear relationship between piezoelectric displacement and permittivity change was discovered, and this linear relationship was applied for positioning control. To detect permittivity changes, a high frequency voltage signal (permittivity detection voltage), in addition to the driving voltage signal, was applied to the actuator. The permittivity change was monitored as the amplitude of the current at the same frequency as the permittivity detection voltage. From this current amplitude, the permittivity change was easily calculated in real time. However, the positioning resolution was insufficient compared to that of traditional external positioning sensors, such as a strain gage sensor. In this study, we improved the positioning resolution by introducing a differential current measurement using two piezoelectric elements, one on each side of a bimorph actuator. The phase of the detected current signal was taken into consideration using a lock-in amplifier. In other words, the conductivity-related current and the permittivity-related current were measured separately. With these improvements, the permittivity change related to the piezoelectric displacement could be measured precisely, and self-sensing feedback control with a positioning error of less than 0.4 μm over a movement range of 80 μm was demonstrated.

Design of a robust control strategy for the heating power of shape memory alloy actuatorsat full contraction based on electric resistance feedback

The application of shape memory alloys (SMA) for actuators is still limited to a couple ofparticular prototypes, and only a few commercial actuators are available. One of the mainreasons is the lack in robustness regarding substantial fatigue and changes in boundaryconditions. In order to improve the life time behavior and reduce the fatigue ofSMA actuators, a self-sensing control strategy is presented. Based on resistancefeedback, the heating power at full contraction is controlled in order to avoidoverheating without reducing the operating voltage. This allows fast actuationwithout thermal overload of the SMA. The concept was proved experimentally.Life time tests show a considerable increase in life cycles and reduce of fatigue.

Self-Sencing Control Research on a Linear Compressor

Compared to conventional compressors, the linear compressor with a free piston can improve efficiency and save energy, but the displacement varies due to different load conditions, which seriously influences its performance. In this paper, based on the theoretical analysis, a self-sensing control system with a SPWM inverter and a PC software interface for a moving-magnet linear compressor is developed, and the displacement of the linear compressor which is under control is tested. The result shows the error of the control system is under 0.2mm, and the accuracy fulfils the requirements.