Control Of Ultrasonic Motor Research Articles

Optimization of Ultrasonic Motor Control Based on NARX Neural Network

Abstract Compared with traditional motors, ultrasonic motors have the advantages of small size and no noise and are widely used in modern technological fields. This article proposes a neural network-based ultrasonic motor control method and optimizes it to address the difficulty of controlling ultrasonic motors. Firstly, the principle and equivalent circuit of ultrasonic motors are studied, and a phase-shifted PWM method suitable for driving ultrasonic motors is proposed. Secondly, to meet the nonlinear characteristics of ultrasonic motors, a NARX neural network that can be used for nonlinear systems is adopted for optimization control. Finally, an experimental platform was built for the experiment, and the results showed that the proposed H-bridge driving circuit has a wide input voltage range. After using the NARX neural network, the output voltage of the H-bridge circuit is more stable, which can provide a stable driving voltage for the ultrasonic motor. It can provide a certain reference value for the application of ultrasonic motors in modern technology.

Design and Implementation of Drive and Control System for Ultrasonic Motor over Power Line Communication

In this study, remote control application of an ultrasonic motor (USM) has been achieved over the power line communication (PLC) system. Fast, practical, affordable and effective operating mode is essential for the USM. This study aimed to develop an original, efficient, effective and economical method. Drive and control of USM control has been succeeded with the developed PLC control system. A two-phase high-frequency inverter, a power line transmitter, and a power line receiver circuits have been designed to drive and control of the ultrasonic motor. Required measurements are acquired from the power line to select the most suitable communication frequency and coupling circuit impedance for the PLC system. For the communication frequency and impedance value measurements the receiver and the transmitter circuits have been designed. The PLC-controlled system has been tested for different operating conditions of the ultrasonic motor. USM control has been accomplished over the existing power line without using extra cables and interfaces for communication. The obtained results show that the PLC-controlled system is practical, reliable, cost-effective, and feasible for the remote control of the USM. This research contributes a new and essential perspective for the PLC-based remote control studies in addition to the USM drive and control strategies.

Adaptive PI control of ultrasonic motor using iterative learning methods

PI (proportional integral) controller is widely utilized in ultrasonic motor control systems. However, PI controllers which use fixed parameters is often difficult to ensure that the control performance meets the expectations. Based on the idea of iterative learning control (ILC), a new online adaptive adjustment method for PI control parameters is proposed. Simple P (proportional) type and PD (proportional differential) type iterative learning controllers are designed to adjust the proportional and integral coefficients of PI controller online. Using this method, the coefficients of PI controller are adaptively adjusted with the change of motor characteristics to ensure the control performance meets expectations. This method can improve the nonlinear expression ability of the controller, so that its input–output relationship can better match the characteristics of the controlled object, thereby improving the control performance. Results of comparative experiments indicate the validity of the proposed control strategy.

Robust Speed Control of Ultrasonic Motors Based on Deep Reinforcement Learning of a Lyapunov Function

Speed control of ultrasonic motors (USM) needs to be precise, fast, and robust; however, this becomes a challenging task due to the nonlinear behavior of these motors including nonlinear response, pull-out phenomenon, and speed hysteresis. However, linear controllers would be suboptimal and unstable, and nonlinear controllers would require expert knowledge, expensive online calculations, or costly model estimation. In this paper, we propose a model-free nonlinear offline controller that can significantly mitigate these challenges. Using deep reinforcement learning (DRL) algorithms, a neural network speed controller was optimized. A soft actor-critic (SAC) DRL algorithm was chosen due to its sample efficiency, fast convergence, and stable learning. To ensure controller stability, a custom control Lyapunov reward function was proposed. The steady-state USM behavior was mathematically modeled for easing controller design under simulation. The SAC agent was designed and trained first in simulation and then further trained experimentally. The experimental results support that the trained controller can successfully expand speed operation range ([0, 300] rpm), plan optimal control trajectories, and stabilize performance under varying load torque and temperature drift.

Super-Resolution Velocity Reconstruction and Control of Ultrasonic Motors.

Accurate and fast velocity feedback signal is essential for the velocity control of ultrasonic motors (USMs). However, the low operating velocity of USMs results in a long velocity detection dead time (VDDT) of incremental encoders, which seriously restricts the dynamic control performance of USMs. Therefore, this article presents a super-resolution velocity control (SRVC) scheme based on the velocity reconstruction for the USM. First, the mathematical model of the USM is derived from the mechanical characteristics and the electromechanical coupling characteristics. Then, the velocity reconstruction method is proposed by combining the model estimated velocity and the encoder measured velocity. The closed-loop control scheme using the reconstructed velocity is implemented by a self-designed driving circuit. Experimental results show the velocity reconstruction method not only can break through the limitation of the encoder resolution to reduce the VDDT but also has a high-velocity accuracy. Furthermore, compared with the existing encoder-based control scheme, the proposed SRVC scheme has a faster velocity response under different loads.

Generalized Minimum Variance Iterative Learning Speed Control of Ultrasonic Motor

Generalized Minimum Variance Iterative Learning Speed Control of Ultrasonic Motor

Secant iterative learning control of ultrasonic motor

Aiming at the problem that the differential term of Newton iterative learning law is not easy to be determined and affects the control performance, the secant iterative learning law is proposed by using the secant method in numerical analysis technology. The proposed control strategy is applied to the speed control of ultrasonic motor to verify its effectiveness. Some practical improvements for the secant iterative learning control strategy are proposed to solve the problems in practical uses of the strategy. According to the nonlinear characteristics of ultrasonic motor, a simple method for determining the value of learning gain is obtained based on the experimental data. Furthermore, online adaptive adjustment method of learning gain is proposed to compensate the nonlinearity of ultrasonic motor. Experimental results show that the motor’s control performance progressively improves during the iterative learning process, featuring higher convergence speed and better performance, which indicates that the proposed control strategy is effective.

3Pb4-4 Torque control of ultrasonic motor using holding torque reduction by standing wave excitation

3Pb4-4 Torque control of ultrasonic motor using holding torque reduction by standing wave excitation

Variable Gain PID Control of Ultrasonic Motor using Novel Hybrid PSO with Improved Searching Ability

The ultrasonic motor (USM) is a type of actuator driven by frictional force. At present, because of their excellent features, USMs are used in a range of applications, such as for autofocus of cameras and in actuators for devices in MRI environments and microrobots. However, because the dynamic characteristics of USMs vary according to temperature, humidity, and load conditions, their mathematical modeling is difficult. Thus, PID control has conventionally been used for the control of USMs. However, conventional PID control with fixed gains cannot compensate for the non-linear characteristic variation of a USM. In this research, we propose a novel hybrid particle swarm optimization (PSO) system for USM control. The proposed method uses PSO to automatically tune the optimized PID gains. The experiments demonstrated that optimized gains in USM control can be obtained in real time, and high accuracy.

Torque control of ultrasonic motors for walking assist system

Torque control of ultrasonic motors for walking assist system

Nonlinear Hammerstein model of ultrasonic motor for position control using differential evolution algorithm

The model of ultrasonic motor (USM) is the foundation of the analysis and control of the motor. Ultrasonic motor maintains nonlinear and complicated in dynamics due to its special structure and unique operating, which makes it difficult to establish a good model with traditional modeling. Moreover, the model should be established in line with strong nonlinearities. The nonlinear Hammerstein model of USM is established in this paper, which can better characterize the nonlinear motor. To adapt the model to the need of position control of ultrasonic motor, driving frequency and rotor position are considered as the input and output variables of the Hammerstein model respectively. To improve the accuracy of model and the efficiency of modeling process, model identification combined with differential evolution algorithm is designed. The comparison of model calculation results with the experimental data shows the accuracy of the established model and the validity of the proposed modeling.

Model-free adaptive speed control on travelling wave ultrasonic motor

AbstractThis paper introduced a new data-driven control (DDC) method for the speed control of ultrasonic motor (USM). The model-free adaptive control (MFAC) strategy was presented in terms of its principles, algorithms, and parameter selection. To verify the efficiency of the proposed method, a speed-frequency-time model, which contained all the measurable nonlinearity and uncertainties based on experimental data was established for simulation to mimic the USM operation system. Furthermore, the model was identified using particle swarm optimization (PSO) method. Then, the control of the simulated system using MFAC was evaluated under different expectations in terms of overshoot, rise time and steady-state error. Finally, the MFAC results were compared with that of proportion iteration differentiation (PID) to demonstrate its advantages in controlling general random system.

Integration simulation method concerning speed control of ultrasonic motor

In this paper, the configuration of control system of the ultrasonic motor (USM) from finite element method (FEM) model by applying the nonlinear model order reduction (MOR) is proposed. First, the USM and the FEM model is introduced. Second, FEM model order reduction method is described. Third, the result of comparing the computing time and accuracy of the FEM model and reduced order model is shown. Finaly, nominal model for control is derived by system identification from reduced order model. Nonlinear model predictive control (NMPC) is applied to the nominal model, and speed is controlled. the controller effect is comfirmed by applying the proposed reduced order model.

Robust Motion Control of Ultrasonic Motors Under Temperature Disturbance

This paper presents a practical robust controller that solves the problem of accurate motion control of ultrasonic motors (USMs) over prolonged durations, where temperature increases pose a significant challenge. This paper focuses on USMs with driver circuits that have a single user-controllable input. Prior to developing the robust controller, a nonlinear model of the system was identified by experimentally measuring the temporal relationship between motor speed and temperature to the applied input control signal. A linear approximation of this model was used to design two robust inverse dynamic controllers: one used temperature feedback and the other did not. Both control methods were implemented on a custom designed embedded control system and achieved highly consistent and accurate performance while under load over a range of working frequencies. Step-response experiments (1 rad) demonstrated a rise time of 0.1 s without any overshoot or steady-state error. A normalized RMSE below 3% with a delay of 25 ms was achieved for reference inputs with frequencies up to 1 Hz. This performance was maintained during prolonged continuous dynamic operation of several minutes, despite the great variation in the motor’s dynamics due to the temperature effects (over a range of 25 °C–45 °C) and modeling uncertainties.

位相差制御方式進行波型超音波モータの恒温駆動

We propose a phase-controlled traveling-wave-type ultrasonic motor (USM) driven in the constant temperature mode. By setting the phase difference between two sinusoidal driving signals fed into USM zero, a thermally-equilibrium condition of USM is attained without rotation. We call such an operation mode idling. Because the resonance frequency of the USM depends on the temperature, the rotational speed is decreased with increasing the temperature, which has been made the frequency control of USM somewhat difficult. Unlike the conventional frequency-controlled USM, a phase-controlled one with idling is free from the temperature change and is controllable with ease. We have constructed a feedback loop system for the phase-controlled USM and evaluated its performance in comparison with the conventional frequency-controlled one.

Magnetic resonance imaging compatible remote catheter navigation system with 3 degrees of freedom.

To facilitate MRI-guided catheterization procedures, we present an MRI-compatible remote catheter navigation system that allows remote navigation of steerable catheters with 3 degrees of freedom. The system consists of a user interface (master), a robot (slave), and an ultrasonic motor control servomechanism. The interventionalist applies conventional motions (axial, radial and plunger manipulations) on an input catheter in the master unit; this user input is measured and used by the servomechanism to control a compact catheter manipulating robot, such that it replicates the interventionalist's input motion on the patient catheter. The performance of the system was evaluated in terms of MRI compatibility (SNR and artifact), feasibility of remote navigation under real-time MRI guidance, and motion replication accuracy. Real-time MRI experiments demonstrated that catheter was successfully navigated remotely to desired target references in all 3 degrees of freedom. The system had an absolute value error of [Formula: see text]1mm in axial catheter motion replication over 30mm of travel and [Formula: see text] for radial catheter motion replication over [Formula: see text]. The worst case SNR drop was observed to be [Formula: see text]3%; the robot did not introduce any artifacts in the MR images. An MRI-compatible compact remote catheter navigation system has been developed that allows remote navigation of steerable catheters with 3 degrees of freedom. The proposed system allows for safe and accurate remote catheter navigation, within conventional closed-bore scanners, without degrading MR image quality.

Novel intelligent PID control of traveling wave ultrasonic motor

A simple control strategy with acceptable control performance can be a good choice for the mass production of ultrasonic motor control system. In this paper, through the theoretic and experimental analyses of typical control process, a simpler intelligent PID speed control strategy of TWUM is proposed, involving only two expert rules to adjust the PID control parameters based on the current status. Compared with the traditional PID controller, this design requires less calculation and more cheap chips which can be easily involved in online performance. Experiments with different load torques and voltage amplitudes show that the proposed controller can deal with the nonlinearity and load disturbance to maintain good control performance of TWUM.

Self-tuning speed control of ultrasonic motor combined with efficiency optimization

Aiming at the nonlinear characteristics of ultrasonic motor (USM) control system, a self-tuning pole assignment speed control strategy is proposed in this paper. The parameters of motor system are identified online, and then the controller is modified online according to the identified parameters of motor. In view of the short-time working characteristic of USM, a method for determining initial values of parameters with online identification algorithms is presented. Using this method, efficient self-tuning control can be realized using a small quantity of testing data. The proposed strategy is robust and relatively simple. Experimental results indicate that the speed control performance is good.

Characteristic model of travelling wave ultrasonic motor

In general, the design and analysis of ultrasonic motor and motor’s control strategy are based on mathematical model. The academic model is widely used in the analysis of traveling wave ultrasonic motor (TWUSM). But the dispersive characteristic of piezoelectric ceramics and other complicated process, such as the friction, make the model’s precision not so accurate. On the other hand, identification modeling method, which is built based on the tested data, has obtained increasing application in the study of ultrasonic motor’s control technology. Based on the identification model, many control strategies can be designed easily. But the identification model is an approximate model, so if a more accurate model of ultrasonic motor can be obtained, the analysis and design of motor control system will be more effective. Characteristic model is a kind of identification model which can accurately describe the characteristics of TWUSM. Based on the tested data, this paper proposes the modeling method of ultrasonic motor’s characteristic model. The paper also makes a comparison of the effectiveness of different identification algorithms. Aiming at the speed control of ultrasonic motor, the influence of the parameter’s initial values on the precision of model is discussed. The calculating results indicate the availability of this characteristic model.

Position control of ultrasonic motor using PID-IMC combined with neural network based on probability

In this paper, a novel control scheme of PID type internal model control (PID-IMC) using neural network (NN) is proposed for the position control of ultrasonic motor (USM). In the proposed scheme, a new NN controller combined with particle swarm optimization (PSO) based on probability is introduced. The NN controller is employed for tuning the control parameter in PID-IMC for compensating the characteristic changes and non-linearity in USM. On one hand, the application of the proposed method avoids the Jacobian estimation in conventional back-propagation (BP) type NN. On the other hand, the PSO based on probability, originated from tribes-PSO, simplifies the PSO setting by reducing the parameters to be set in USM control. For confirming the effectiveness of the proposed method in position control, a group of experiments have been done on an existent USM servo system and the results are studied in this paper.