Motor Position Servo Research Articles

QUICK AND PRECISE POSITION CONTROL OF ULTRASONIC MOTORS WITH TWO CONTROL INPUTS

ABSTRACT Ultrasonic motor (USM) has an excellent performance and many useful features. Since this motor is superior in holding torque and high response characteristic, it has been expected to use as position servomotor for small motors. There have been reported some mathematical models of the ultrasonic motor. however, these models are too complex to apply for control of the motor. Therefore position controllers based on PI control or fuzzy control have been proposed in recent years. It is difficult to control the ultrasonic motor with high-performance using such controllers, thus simple and convenient mathematical model is necessary for precise control. This paper presents a new position control scheme of ultrasonic motor, it consists of a PI controller and an adaptive controller which compensates the speed characteristic variations with online parameter identification. Moreover, this system controls both driving frequency and phase difference in order to achieve a quick and precise position control. The effectiveness of proposed control.scheme is demonstrated by experiments.

High-Precision Control of AC Servo Motor Positioning Systems by Friction Compensation

In the AC servo motor positioning system, friction and elastic deformation significantly degrade the positioning accuracy. We propose a method of compensating for those effects based on the estimated load torque by a disturbance observer. The proposed observer is driven by a motor current command and an encoder signal without adding any external sensors. Experimental investigation was carried out using a newly developed system for driving an AC servo motor. Torque ripple of the AC servo motor was estimated in detail and modeled as a Fourier expansion for compensation in real time on DSP. This torque ripple model drastically improves the accuracy of torque estimation up to 2% against the added torque under load torque, that is, 4% to 40% of the nominal motor torque. Moreover, the coupled behavior of friction and elastic deformation was estimated by the above method, and it was confirmed that the stiffness and friction can be precisely and simultaneously estimated.

Variable slope pulse pump controller for stepping position servo control system using frequency-locked technique

A stepping position servomotor system based on frequency-locked technique is proposed for high-performance incremental position control. A novel microcomputer-based variable slope pulse pump controller (VSPPC) using multi-rate sampling technique is exploited. The proposed VSPPC can adaptively generate motor motion profile, and it can replace the traditional PID controller for applications in stepping motor position control. System models are constructed for stability study and computer simulation. A prototype is designed and implemented to verify the theoretical studies and examine the performance of the proposed system. Position and speed responses of a realized system for 0-50 cm movement with 10 mm resolution is investigated. With the variable slope technique employed in VSPPC, the acquisition time for long-distance movement is reduced significantly and is close to that of short-range movement. In particular, the position acquisition time has improved about 67-79% compared to the conventional position control system.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

High Performance Servo-System by Rotational Machines. Quick and Precise Position Control of Ultrasonic Motors Using Hybrid Control.

The ultrasonic motor has an excellent performance and many useful features, which electromagnetic type motors do not possess, such as high torque, low speed, compactness in size, no electromagnetic interferences and so on. Particularly, this motor has a large holding torque and a high response characteristic. So, it has been expected to use as position servomotor. The driving principle of ultrasonic motors is, however, different from those of electromagnetic type motors and its mathematical model has not been developed yet. Moreover, its speed characteristics vary with the driving conditions. Therefore, it is difficult to control ultrasonic motors with high performance. In this paper, the position control method of this motor by adaptive control is proposed. The usefulness and validity of proposed control method is examined in experiment.

Fuzzy precompensated PID controllers

While proportional integral derivative (PID) controllers are widely used in industrial applications, they exhibit poor performance when applied to systems containing unknown nonlinearities, such as deadzones, saturation, and hysteresis. In this paper, the authors propose a fuzzy logic-based precompensation approach for PID controllers. The authors demonstrate the performance of their scheme via experiments performed on a DC servomotor position control testbed under varying load conditions. The authors' results show that the fuzzy precompensated PID controllers have superior performance compared to conventional PID controllers. In addition, the proposed scheme is robust to variations in load. In the experimental testbed, the variations in loading conditions correspond to variations in the level of nonlinearities in the plant. The authors' scheme is easily implemented in practice simply by adding a fuzzy precompensator to an existing PID controller.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An adaptive controller for induction position servo motor drives

Abstract A high performance discrete adaptive induction position servo motor drive is designed and implemented in this paper. First, an indirect field‐oriented induction motor drive is implemented and its dynamic model is estimated from the measurements. Then a two‐degree‐of‐freedom (2‐DOF) servo controller is quantitatively designed to match the prescribed drive specifications. In order to reduce the effects of machine and load parameter variations on the performance of the servo drive, an adaptive controller is proposed. The reference model of the adaptive controller is chosen as the transfer function of the controlled drive system by the 2‐DOF controller in the nominal case, since it possesses the desired drive dynamic behavior. The simulation and experimental results show that good following and regulating control performances are achieved. Moreover, the performances are rather insensitive to the parameter variations.

High-Precision Control of AC Servo Motor Positioning Systems by Friction Compensation.

In the AC servo motor positioning system, friction and elastic deformation significantly degrade the positioning accuracy. This paper proposes a method of compensating for those effects based on the estimated load torque by a disturbance observer. The proposed observer is driven by a motor current command and an encoder signal without adding any external sensors. Experimental investigation was carried out using a newly developed system for driving an AC servo motor. Torque ripple of AC servo motor was estimated in detail and modeled as a Fourier expansion for the compensation in real time on DSP. This torque ripple model drastically improves the accuracy of torque estimation up to 2% against the added torque under load torque that is 4% to 40% of the maximum motor torque. Moreover, the coupled motion of friction and elastic deformation was estimated by the above method, and it was confirmed that the stiffness and friction can be precisely and simultaneously estimated.

サーボモータの適応制御

A practical simple discrete time adaptive control system for servo motor positioning system is presented. It is assumed that the controlled system has characteristics with unknown inertia load and disturbance force (including friction etc.).The proposed method is applied to the 2nd and 3rd axis of robot HA-100. It is confirmed that this adaptive controller has high performance in case the modeling error is small.

Identification of Thermally Safe Load Cycles for An Induction Motor Position Servo

Advances in the available performance of induction motor-inverter systems permit these drive systems to meet progressively more demanding performance criteria. High-performance servos require the induction motor to produce high torque and power. The severely repetitive load cycles stress the motor's insulation with high operating temperatures. The traditional rating of the induction motor based on ac line operation is not useful under these circumstances. In spite of the complexity of the thermal problem, an approximate thermal calculation procedure will allow servo designers and users alike to predetermine thermally safe load cycles for induction motor servo drives. Study is directed to the formulation of a simplified thermal model of vector-controlled induction motor servos rated between 1 and 15 kW and to the subsequent use of this model to predict thermally safe load cycles. A set of normalized curves relating duty cycle and torque is presented for the available classes of motor insulation. Theoretical results are supported by experimental verification on an existing vector-controlled induction motor servo system.

On the Dynamics and Control of a Flexible Industrial Robot

There are several advanced manufacturing tasks like the highly accurate cutting of geometrically difficult metal surfaces which have not yet been solved in the past by means of industrial robots because of their flexible properties mainly, caused by elasticity, plasticity or backlash within the gears. In this paper contrary to the majority of conventional position control algorithms which are based on rigid multibody system models, an alternative control concept is proposed that refers to a more realistic flexible multi-body system model. It provides both a better tracking and disturbance behaviour because not only the servo motor position but also the deflection of each joint and its time derivatives are considered in the closed-loop algorithm. Disturbing nonlinear effects of slip-stick friction can be compensated by the injection of high-frequency “dithering”. The performance quality of the proposed control concept which has been implemented on a microcomputer system will be thoroughly investigated.