AC Servo Research Articles

The Design of Motor Precision Positioning System Based on STM32 Single Chip Microcomputer

Aiming at the problem that the positioning accuracy of the motor is not high when the electric hoist vertical lifting industrial material is working, the PC + motion control card + digital AC servo motor positioning cost is too high. The system uses the STM32F103 core controller + incremental photoelectric encoder control scheme, which can locate the position of the material tray accurately. The test results show that the system has the characteristics of high positioning accuracy, stable operation and low cost, The average error is within 0.2mm, it has a certain guiding significance for industrial measurement, automatic control, electrical transmission and other fields of application.

Design of an AC Servo Controller for a Dynamic Simulation Test System for Hydraulic Excavators Based on a System-on-chip Architecture

The AC servo system of hydraulic excavator dynamic simulation test system is studied in this paper.The AC servo controller based on C8051F410 on-chip system is designed in this paper. The dynamic characteristics of AC servo are tested and the fault treatment measures of AC servo controller are improved. Comparison between traditional PID and improved PID algorithm in AC Servo Controller by dynamic Simulation Test system, the improved PID algorithm suitable for dynamic simulation test system is obtained, and the response characteristics of the improved PID algorithm to AC servo system are tested. At the same time, the reliability of AC servo controller is tested.

High-Productivity Forge Welding of AZ80 Magnesium Alloy to A2024 Aluminum Alloy Using an AC Servo Press

We have developed a high-productivity dissimilar bonding technology intended for the automobile sector, which is increasingly becoming multimaterial oriented. The forge-welding process, which involves diffusion bonding with plastic deformation in the open air, was used to bond AZ80 magnesium (Mg) alloy with A2024 aluminum (Al) alloy with a pure titanium (Ti) sheet interlayer using a high-speed, high-precision AC servo press. The influences of the preheat temperature, Ti sheet thickness, and the pressure holding time on the tensile strength were surveyed. In addition, the influence of the polishing of the bonding surfaces was examined. A pressure holding time of 0.1 seconds with a cycle time of less than 2 seconds provided high-strength bonding. Furthermore, a high-strength bond could be achieved with a Ti sheet thickness of only 0.3 mm and without needing polishing before bonding or heat treatment after bonding. Cross-sectional textures of the macro- and micro-fracture surfaces and elemental analyses of the bonded interface were examined. The fracture side of the bonded interface, the Ti-Mg alloy side, had a thin (ca. 5 nm) Ti-Al reaction layer (RL), which confirmed a diffusion bonding mechanism between the Ti and Al elements present in the Mg alloy. Despite processing in air with an extremely short processing time, this impacting press method provided good plastic deformability and sufficient elemental diffusion to result in high-strength bonding with a tensile strength ranging from 130 to 150 MPa.

Anti load disturbance method for AC servo motor power system

A dimensionality reduction load torque observed is designed to provide compensation control for the motor with the observation value of load torque converted over for the problem that load disturbance decreases the control precision of servo system. A three-loop mathematical model is established for the servo control system. Use of two-/three-order optimal model theory contributed to the derivation of the tuning formula for three-loop control parameters. A simulation model is established for the space vector control of AC servo system. The simulation experiment validates that the tuned three-loop parameter provides the system with good dynamic performance. An experiment platform is built. The load sudden change experiment of the motor demonstrates the feasibility that torque compensation control improves the control precision of servo system in the presence of load disturbance.

Estimation of disturbance torque for ballscrew drive system with using high resolution encoder

Ballscrew drive system has high mechanical efficiency and is able to get high gear ratio easily. But it also has non liner friction elements like rolling friction and viscous friction, so it makes ballscrew control accuracy worse. For that reason, it is proposed that inserting disturbance observer into control system and compensating disturbance torque. Generally, rotary encoder is used for position sensor in ballscrew control, but its resolution affects accuracy of drive control and disturbance observer. In this paper, we propose a speed control system using AC servo motor ball screw drive system, compare driving characteristics in low speed range when using low resolution encoder and high resolution encoder as position sensor. Also we examine effects for driving characteristics by using and compensating disturbance observer. These verifications were carried out by simulation and actual machine.

High cycle deep drawing of PA6 matrix carbon fiber reinforced thermoplastics by servo-driven screw press

To accomplish high cycle deep drawing of carbon fiber reinforced thermoplastics, a new AC servo driven screw press is manufactured with die cushion to avoid rebounding of upper tool at bottom dead center. If the forming process is conducted during cooling stage, the process time will be drastically reduced. To finish and shorten the forming process before hardening of resin in cooling process, the die temperature must be kept to as possible as lower and the forming velocity must be as possible as higher. At the forming speed 300 mm/s, 2 mm thickness hemisphere shape is successfully deformed in 10 s at die temperature 80 °C. The new Screw press is confirmed to be most suitable to shorten the cycle time of forming carbon fiber reinforced thermoplastics.

Study on a Floating Point Absorber Type Wave Energy Converter with One Line Tension Leg Mooring

Motions and load characteristics of a floating point absorber type wave energy converter (WEC) were investigated by tank test considering operation modes. Four typical operation modes of a movable float, namely fixed mode, free mode, controlled mode without power generation, and controlled mode with power generation, were examined by the WEC model with an AC servo motor and a rack and pinion mechanism as a power take-off system in the tank test. The test results show that the operation modes have little effects on surge and pitch motions of the WEC. The measured load, such as mooring tension and axial force on the WEC, on the contrary, were strongly affected by the operation modes. The measured bending moment of the WEC, however, was affected by the WEC surge and pitch motions rather than the operation modes. Additionally, a numerical simulation using a commercial code, the Orcaflex, was conducted, and the simulation results were compared with measured ones. The WEC motions and mooring tension of the simulation results were comparable to those of measured ones in regular waves. The simulated power spectrum density of surge, pitch and mooring tension qualitatively matched measured ones, but they slightly underestimated measured ones at peak wave frequency in irregular waves.

Real-Time Swing-up and Stabilization Control of a Cart-Pendulum System with Constrained Cart Movement

Abstract The cart-pendulum system is a typical benchmark problem in the control field. It is a fully underactuated system having one control input for two degrees-of-freedom (DOFs) system. It has highly nonlinear structure, which can be used to validate different nonlinear and linear controllers and has wide range of real-time (realistic) applications like rockets propeller, tank missile launcher, self-balancing robot, stabilization of ships, design of earthquake resistant buildings, etc. In this work, modeling, simulation and real-time control of a cart-pendulum system is performed. The mathematical model of the system is developed using Euler-Lagrange approach. In order to achieve a more realistic model, the actuator dynamics is considered in the mathematical model. The main aim of this work is to investigate the performance of two different control strategies- first to swing-up the pendulum to near unstable equilibrium region and second to stabilize the pendulum at unstable equilibrium point. The swing-up problem is addressed by using energy controller in which cart is accelerated by providing a force to the cart with a AC servo motor with the help of timing pulley arrangement. The initial velocity of the cart is taken into account to confirm swing-up in the restricted track length. The cart displacement in the restricted track length is verified by simulation and experimental test-run. The regulation problem of stabilization of pendulum is addressed by developing the controller using Pole Placement Controller (PPC) and LQR Controller (LQRC). Both the control strategies are performed analytically and experimentally using the Googoltech Linear Inverted Pendulum (GLIP) setup. The analytical results, simulated in MATLAB and SIMULINK environment, are found in close agreement with the experimental results. In order to demonstrate the effect of both the stabilizing controllers on the performance of the system, comparison of the experimental results is reported in this work. It is demonstrated experimentally that LQR controller outperforms the Pole Placement controller, in terms of reduction in the oscillations of the inverted pendulum (56 %), as well as the magnitude of maximum control input (66.7 %). Further, robustness of the closed-loop system is investigated by providing external disturbances.

Estimation and Compensation of the LuGre Friction Model in High-Speed Micro-Motion Control

Static friction compensation is usually required to reduce friction in precision motion control and manufacturing processes. Micro-motion control is a current trend for precision machining in the electronics industry. Dynamic friction plays an important role in systems using micro-scale motion at high-speed and high-frequency command. The Lund–Grenoble (LuGre) friction model is suitable for coping with the dynamic friction effect. However, the parameters of this model are difficult to accurately identify to ensure satisfactory control performance in miniature machining. This paper proposes an efficient and systematic three-step parameter estimation method for LuGre modeling. The friction compensation of the proposed approach was successfully demonstrated on a 400W AC servo motor. Furthermore, under a peck drilling command on DYNA 1007 CNC machine, the LuGre model also improved motion precision by 72.0% in the maximum peak error.

Disturbance observer control for AC speed servo with improved noise attenuation

The paper deals with a noise attenuation design of a modification of the disturbance observer (DO) based PI control for an AC servo drive with the dominant first-order dynamics. The achieved results are compared with the traditional PI control. The DO based filtered PI (DO-FPI) controller consists of the P control with adjustable filter. It is augmented with an integral action based on load reconstruction using equally filtered plant dynamics inversion. The availability of broadly scalable filters requires a simple one-parameter based tuning. In looking for a possibly good noise attenuation, it allows changing the filter order and time constants by keeping nearly the same speed of disturbance responses as in the PI control. An application to the speed servo control with an incremental position sensor brings to light interesting properties of the compared solutions. The DO FPI and PI control give nearly equally robust solutions. However, in case of PI control it is at the expense of significantly increased torque ripple.

Indirect adaptive fuzzy wavelet neural network with self- recurrent consequent part for AC servo system

This paper proposes a novel indirect adaptive fuzzy wavelet neural network (IAFWNN) to control the nonlinearity, wide variations in loads, time-variation and uncertain disturbance of the ac servo system. In the proposed approach, the self-recurrent wavelet neural network (SRWNN) is employed to construct an adaptive self-recurrent consequent part for each fuzzy rule of TSK fuzzy model. For the IAFWNN controller, the online learning algorithm is based on back propagation (BP) algorithm. Moreover, an improved particle swarm optimization (IPSO) is used to adapt the learning rate. The aid of an adaptive SRWNN identifier offers the real-time gradient information to the adaptive fuzzy wavelet neural controller to overcome the impact of parameter variations, load disturbances and other uncertainties effectively, and has a good dynamic. The asymptotical stability of the system is guaranteed by using the Lyapunov method. The result of the simulation and the prototype test prove that the proposed are effective and suitable.

Novel AC Servo Rotating and Linear Composite Driving Device for Plastic Forming Equipment

The existing plastic forming equipment are mostly driven by traditional AC motors with long transmission chains, low efficiency, large size, low precision and poor dynamic response are the common disadvantages. In order to realize high performance forming processes, the driving device should be improved, especially for complicated processing motions. Based on electric servo direct drive technology, a novel AC servo rotating and linear composite driving device is proposed, which features implementing both spindle rotation and feed motion without transmission, so that compact structure and precise control can be achieved. Flux switching topology is employed in the rotating drive component for strong robustness, and fractional slot is employed in the linear direct drive component for large force capability. Then the mechanical structure for compositing rotation and linear motion is designed. A device prototype is manufactured, machining of each component and the whole assembly are presented respectively. Commercial servo amplifiers are utilized to construct the control system of the proposed device. To validate the effectiveness of the proposed composite driving device, experimental study on the dynamic test benches are conducted. The results indicate that the output torque can attain to 420 N·m and the dynamic tracking errors are less than about 0.3 rad in the rotating drive. the dynamic tracking errors are less than about 1.6 mm in the linear feed. The proposed research provides a method to construct high efficiency and accuracy direct driving device in plastic forming equipment.

Modeling and simulation for heavy-duty mecanum wheel platform using model predictive control

This paper presents a study on a control system for a heavy-duty four Mecanum wheel platform. A mathematical model for the system is synthesized for the purpose of examining system behavior, including Mecanum wheel kinematics, AC servo motor, gearbox, and heavy duty load. The system is tested for velocity control, using model predictive control (MPC), and compared with a traditional PID setup. The parameters for the controllers are determined by manual tuning. Model predictive control was found to be more effective with reference to a linear velocity.

Experimental Study on Dynamic Behavior of High Precision Servo Motor for Machine Tools

In the field of machining industries it is always required to improve the accuracy of precise products, die and molds. The feed drive system for the machine tools consists of an AC servo motor, an amplifier and rolling elements etc. It is well known that the nonlinear behaviors of the rolling elements influence the motion accuracy of the feed drive system. However, in spite of the analysis of static behaviors have been done, the dynamic behaviors are not so examined. Our special interest is how to control the nonlinear behaviors of the rolling elements and to operate the feed drive system with high accuracy. In order to model the nonlinear behaviors of the feed drive system, we measure the transient response when the step inputs of microscopic displacement are input to the AC servo motor and the detail analysis will be done. Experimental results show that the step responses become slow as the input displacement becomes microscopic. It means that with the ball bearing built into the AC servo motor used to feed driving system have the nonlinear behavior in microscopic displacement range.

2 m望远镜主轴交流伺服控制系统设计

2 m望远镜主轴交流伺服控制系统设计

A Frequency Domain Approach for Tuning Control Parameters of CNC Servomotors to Enhance its Circular Contouring Accuracy

The machining of a cone frustum as specified in National Aerospace Standard NAS-979 is a widely accepted test to evaluate the performance of five-axis machining centers. By measuring the cross-sectional circularity or roundness of the cone, the contouring accuracy of five-axis computer numerical control (CNC) can be evaluated. Thus, reduction of circularity is directly related to improvement of the contouring accuracy in circular motions. Most CNC actuators are AC servo motors that are precisely controlled via two closed loops—one each for position and velocity. The circular contouring accuracy of a five-axis CNC can be improved by adjusting the loop gains and the time constant of velocity loop integration. Although higher gains enable the servomotors to reach the desired positions faster, the resulting contouring accuracy may not be satisfactory. Furthermore, excessively high gains may cause vibrations. This paper proposes a frequency domain approach for tuning the control parameters for each axis so that their frequency responses are very similar, thus reducing the circularity value of the cross sections of a manufactured cone frustum. The paper also describes a method to obtain the frequency response of each axis by using properly engineered input chirp sine signals. Simulated results showing the effect of tuning the control loop parameters based on the frequency response of each axis are presented. Moreover, a case study was conducted to show the variation in the circularity value when the control parameters of each axis were tuned to obtain similar frequency responses of the linear and rotary axes within a frequency range.

レーザレンジファインダを用いたガイドレスな AGV の開発に関する研究

The purpose of this research is to develop an AGV (Automatic Guided Vehicle) which has high accurate position control and mapping using a laser rangefinder. Recently, some factories are introducing AGVs in order to respond flexibly to a variety of conveyance request. Generally, a method of driving an AGV is using markers, wires or magnets. We manufactured an AGV which do self-location estimation by using a laser rangefinder without markers, wires or magnets. The AGV consists of a servo driver, AC servo motors, two batteries and a laser rangefinder. On this study, we have created a map of the experimental environment with SLAM (Simultaneous Localization and Mapping). The AGV performed the self-position estimation using a created map and it could move autonomously from a start position to an end position that we set in advance. We aim to improve the accuracy the AGV move by Spline interpolation.

Fuzzy Logic Controller for Speed and Torque in AC Servo System

Fuzzy Logic Controller for Speed and Torque in AC Servo System

Active vibration control of structure by Active Mass Damper and Multi-Modal Negative Acceleration Feedback control algorithm

In this study, an Active Mass Damper (AMD) consisting of an AC servo motor, a movable mass connected to the AC servo motor by a ball-screw mechanism, and an accelerometer as a sensor for vibration measurement were considered. Considering the capability of the AC servo motor which can follow the desired displacement accurately, the Negative Acceleration Feedback (NAF) control algorithm which uses the acceleration signal directly and produces the desired displacement for the active mass was proposed. The effectiveness of the NAF control was proved theoretically using a single-degree-of-freedom (SDOF) system. It was found that the stability condition for the NAF control is static and it can effectively increase the damping of the target natural mode without causing instability in the low frequency region. Based on the theoretical results of the SDOF system, the Multi-Modal NAF (MMNAF) control is proposed to suppress the many natural modes of multi-degree-of-freedom (MDOF) systems using a single AMD. It was proved both theoretically and experimentally that the MMNAF control can suppress vibrations of the MDOF system.

Optimization of blank shape and segmented variable blank holder force trajectories in deep drawing using sequential approximate optimization

Blank holder force (BHF) is one of the important process parameters for successful sheet metal forming. Variable blank holder force (VBHF) that the BHF varies through the forming process is recognized as an advanced forming technology. It has also been reported that segmented VBHF (S-VBHF) is valid to a complex shape forming, but the optimal S-VBHF trajectories are rarely discussed and used. In addition to BHF, blank shape has an influence on the product quality. The blank shape minimizing the earing is still an important issue in sheet metal forming. Simultaneous optimization of both S-VBHF trajectories and blank shape is one of the crucial issues in industries. This paper proposes a method to simultaneously optimize both the segmented VBHF trajectories and the blank shape. Numerical simulation in sheet metal forming is so intensive that a sequential approximate optimization (SAO) using a radial basis function (RBF) network is adopted for the simultaneous design optimization. Based on the numerical result, the experiment using the AC servo press (H2W300, Komatsu Industry Corp.) that can conduct the optimal S-VBHF trajectories is carried out. It has been confirmed from the numerical and experimental result that the proposed approach is valid.