Sensorless Position Control of Linear Electromagnetic Actuator for Gear Shift Unit

Linear electromagnetic actuators (LEAs), operated by electromagnetic action, are widely used in various applications, such as switches and solenoid valves. Since it operates on the principle of electromagnetic attraction, it is very sensitive to magnetic field. LEA may fail under the impact of disturbing magnetic field (DMF), thus threatens the stability of the whole system. As the magnetic field around tokamak is very strong, it is of great importance to evaluate the behavior of LEAs under DMF. This article presents the analysis of two different types of LEAs in DMFs. Based on the finite element method, the influences of DMF on the two LEAs are analyzed, and both the opening and closing processes are considered. Analyses show that the piston-type LEA may fail to act under DMF, while the plate-type LEA may malfunction even it is not energized. Based on the analysis, the failure mechanism is revealed, and the failure thresholds of the two LEAs are also quantified. The experimental verifications are carried out, which are in good agreement with the simulation results. The analysis model and the main conclusions presented in this article are of great significance to guide the antimagnetic field design of LEAs and ensure their reliable operations in tokamakxs.

This article presents a new electromagnetic linear actuator applied in the electromagnetic-driven valve train. To clarify the actuator’s temperature rise and heat distribution, a heat transfer mode...

In this study, a type of direct-drive gearshift system integrated into a motor-transmission coupled drive system is introduced. It used two electromagnetic linear actuators (ELAs) to perform gearshift events. The adoption of ELAs simplifies the architecture of the gearshift system and has the potential to further optimize gearshift performance. However, a number of nonlinearities in the gearshift system should be investigated in order to enhance the performance of the direct-drive gearshift system. An active disturbance rejection control (ADRC) method was selected as the principal shifting control method due to the simple methodology and strong reliability. The nonlinear characteristics of the electromagnetic force produced by the ELA were subsequently reduced using the inverse system method (ISM) technique. The ADRC approach also incorporated an acceleration feedforward module to enhance the precision of displacement control. The extended state observer (ESO) module used a nonlinear function in place of the original function to improve the ability to reject disturbances. Comparative simulations and experiments were carried out between the ADRC method and improved ADRC (IADRC) method. The outcomes demonstrate the effectiveness of the designed control method. The shift force fluctuates less, and the shift jerk decreases noticeably during the synchronization procedure. In conclusion, combined with the optimized IADRC method, the direct-drive gearshift system equipped with ELAs shows remarkable gearshift performance, and it has the potential to be widely used in motor−transmission coupled drive systems for EVs.

Conventional electromagnetic linear actuators(ELA) have difficulty in balancing efficiency, response and accuracy, so a novel compound ELA is researched, featuring a coaxial integrated design of moving coil and moving iron actuators that switch between co-drive mode and separate drive mode based on service environment. In order to further enhance the comprehensive performance of the actuator and improve its adaptability to extreme working conditions, a multi-objective hierarchical optimization strategy was proposed based on NSGA-II algorithm by analyzing its structural principle, magnetic circuit characteristics and electromagnetic force characteristics. The moving coil actuator, as the main driving component, and the moving iron actuator, as the auxiliary driving component, are selected as the first and second layer optimization objects for multi-objective optimization design. Results indicate that the actuator achieves starting forces of 587.6N and 191.4N under cooperative drive mode and separate drive mode, respectively. Following optimization, these forces increased by approximately 2.2% and 22.4%, while the mover mass was reduced by about 7.2%. The actuator's thrust density, response speed, and structural compactness were effectively enhanced. The proposed approach can be used to solve the complex multi-objective optimization tasks in ELA designing.

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/spl deg/ el. is practically realized.

Extended state observer-based time-optimal control for fast and precise point-to-point motions driven by a novel electromagnetic linear actuator

To realise position control of an induction machine without a mechanical sensor it is necessary to exploit the slotting of the rotor and its influence on the terminal voltage and current respectively. Different rotor designs have already been proposed to generate a spatial influence of the rotor position on the transient terminal quantities. However, in this paper only conventionally designed machines are considered. The influence of rotor skewing, slot opening and saturation on the scope for sensorless position estimation is shown. The investigation of the transient electrical behaviour of the induction machine is done by two different measurement methods. First by applying the INFORM-method (indirect flux detection by on-line reactance measurement). It detects local differences in the stator impedance of the machine by evaluating the transient current change due to voltage pulses applied to the terminals of the machine. Usually the INFORM method is used to detect the saliencies caused by main flux saturation. However it can as well be utilised for position estimation. The second method is the determination of the transient flux-change by measurements made with special measurement coils at different spots in the machine. It is shown that sensorless position control with standard machines in the whole operating range is a very challenging task due to saturation.

This paper presents the research on a problem which is difficult to implement in the actual magnetization process of Electromagnetic Linear Actuator (ELA)'s permanent magnets radially magnetized. Given magnetic field symmetry and assembly feasibility, it creatively puts forward four parallel magnetized-permanent magnets joint schemes (PM-PMs Joint Schemes) of the ELA. On the basis of mathematical modeling and simulating calculation, further study on the comparison of magnetic field effects and ELA's performance in different joint schemes is accomplished. Then, through the Analytic Hierarchy Process(AHP), 8 parallel magnetized-permanent magnets joint model (8 PM-PMs Joint Model) is determined as the best choice after optimizing selection. Further, the 8 PM-PMs Joint Scheme is trial-produced and its air gap flux density and electromagnetic force are also tested. Compared with simulating calculation, the maximum error from test result is within 4.3%, verifying the accuracy of mathematic model and simulating calculation.

Design, development and control of flexure mounted linear displacement electromagnetic actuator

While linear actuators have many applications, the majority of them are rigid and straight, limiting their applications and the work environment. This article presents a novel design for an electromagnetic flexible linear actuator (FLA) that can overcome such restrictions, as well as a computationally efficient model that predicts the output force based on the input current and the actuator shape. The FLA design is of a 3D-printable stator, easy-to-manufacture, and assemble with off-the-shelf components, modular, scalable, and easy to maintain. It can bend and take any arbitrary shape with reasonable curvature based on the dimensions of the motor. This facilitates the integration of the FLA in industry. The presented novel mathematical model fills the gap in the research area of the nonstraight actuator models. The model is derived by decomposing the actuator into noncoaxial coils and magnets. Through cascading the forces generated between each coil and the magnets, the output force of the actuator is calculated. The output of the model is validated experimentally by comparing its results to the actuator's force at different bending angles, planar, and in 3D space.

In this paper an approach towards databased fault diagnosis of linear electromagnetic actuators is presented. Time and time-frequency-domain methods were applied to extract fault related features from current and voltage measurements. The resulting features were transformed to enhance class separability using either Principal Component Analysis (PCA) or Optimal Transformation. Feature selection and dimensionality reduction was performed employing a modified Fisher-ratio. Fault detection was carried out using a Support-Vector-Machine classifier trained with randomly selected data subsets. Results showed, that not only the used feature sets (time-domain/time-frequency-domain) are crucial for fault detection and classification, but also feature pre-processing. PCA transformed time-domain features allow fault detection and classification without misclassification, relying on current and voltage measurements making two sensors necessary to generate the data. Optimal transformed time-frequency-domain features allow a misclassification free result as well, but as they are calculated from current measurements only, a dedicated voltage sensor is not necessary. Using those features is a promising alternative even for detecting purely supply voltage related faults.

This paper presents the initial rotor position estimation and the sensorless control for IPM synchronous motor. In sensorless drive, it is important to know the exact information of the initial rotor position. The initial position estimation method is based on the peak current changed according to the rotor position owing to the saliency. A speed sensorless control based on an instantaneous reactive power is proposed for the IPMSM drives. In the proposed algorithm, the current observer estimates the line currents and the estimated speed can be yielded from the voltage equations because the information of speed is included in back EMF. To minimize the estimation error, the speed estimator is compensated by using the instantaneous reactive power.

This paper presents sensorless position estimation using a conventional or "symmetric" cage-induction motor. The rotor position information is obtained by high frequency injection and using the modulating effect of the rotor slots. This makes true sensorless position control possible. The deteriorating effect of saturation harmonics for operation at full flux and higher loads is suppressed by using a harmonic compensation scheme based on parameters obtained from an automated commissioning process. Experimental results are presented showing sensorless position estimation at full flux and high loads. For a conventional machine, such high-load results have not been published before.

This study aims to realize a tactile display which can represent 2D haptic information on the display surface. The display consists of many compact actuation systems whose position and force can be controlled. In our previous works, sensorless motion control for a compact solenoid actuator has been proposed to realize the compact actuation system. Additionally, we have proposed sensorless control method for a dual solenoid actuator (DSA) to improve the control performance. However, the proposed DSA system has a few problems such as large body, large mover mass, and large friction force. In order to solve these problems, this paper proposes a new compact dual solenoid actuator (CDSA). The proposed actuator has less number of coil turns, therefore much current is required to generate large magnetic force. On the other hand, the large current generates large thermal energy which causes change of the inductance characteristics of the dual coils. The sensorless position estimation is conducted using the relation between the mover position and the inductance. Therefore, thermal compensation method for the new CDSA is also proposed in this paper. Experiments were conducted to validate the proposal. As a result, the sensorless position estimation with less than 60μm estimation error was achieved.

This paper presents the use of the inherent high-frequency pulsewidth modulation (PWM) harmonics for sensorless control of ac machines. The amplitude and position of the PWM voltage harmonics cannot be controlled independently and are determined by the fundamental machine operation. However, they do form a high-frequency excitation and can provide information on saliencies within ac machines. This paper examines the feasibility of sensorless control based on extracting the rotor-bar slot position information for a cage induction machine using PWM harmonics. The position-signal demodulation and compensation schemes used are derived. Experimental results are provided for an off-the-shelf induction motor operating under sensorless current, speed, and position control, including zero excitation and zero speed.