Multi-axis Servo Research Articles

Discrete Time-Varying Internal Model-Based Control of a Novel Parallel Kinematics Multi-Axis Servo Gantry

This paper presents an internal model-based approach for trajectory tracking in the discrete time-varying setting. A newly designed parallel kinematics servo gantry is well suited for high precision contouring at high speed ranges. The discrete time-varying internal model-based control is developed for controlling the servo gantry system to track complicated trajectories generated by linear time-varying systems. Based on a novel parallel time-varying internal model structure, a low order robust discrete time-varying stabilizer is synthesized. The proposed tracking control architecture is deployed on the novel parallel kinematics servo gantry system to achieve high precision contour tracking performance for frequency-varying signals generated by high order time-varying autonomous system.

Analysis and Modeling of Air-Core Monopole Linear Motor for Nanopositioning System

In the ultra-precision system, the multi-axis servo system is composed of air-core monopole linear motors (AMLM) for achieving nanopositioning. In the AMLM system, the thrust varies according to the changes of the relative position of motor's primary and secondary. In this paper, the concept of thrust stiffness is proposed in order to illustrate the phenomenon of varieties of thrust according to changes in position. By using the surface charge model, the air-gap magnetic flux density of AMLM is predicted. Based on this prediction, the whole winding's thrust, including straight and corner segments of winding, is calculated. Then, this winding thrust model is simplified to replace the original complicated analytical model. The accuracy of the simplified model is verified by the corresponding experimental tests. Thus, the thrust stiffness simplification model can be used in the feedforward compensation model in the control system of AMLM and efficiently decrease the calculation time of DSP.

Small mechanical press with double-axis servo system for forming of small metal products

Multi-axis servo systems have been applied to many machine tools in recent decades, but they are not commonly used for press machines. They are particularly uncommon for small presses because it is still believed that the precision of a small press is dependent on the precision of its components and parts. However, high-precision components and parts are difficult to manufacture and assemble, so the costs of small precision presses are roughly equal to or higher than those of large press machines. Moreover, the accuracy of conventional small presses worsens over long operation times, particularly when dealing with off-center loading frequency. Therefore, we propose a small mechanical press with an adjustable driving system, using a slide and double-axis servo system, for manufacturing small products. Through this proposed design, we expect higher-quality products to be produced for lesser cost than conventional small presses.

Electronic Anti-Cut for Automatic High Speed Horizontal Flow Wrapper with ECAM

In this paper, a DSP-based servo motion controller is developed for the horizontal flow wrapper, where the multi-axis servo drives and electronic anti-cut are designed to improve automatization and safety for the packaging system. This paper relates generally to high speed packaging machinery with electronic cam and more particularly to the process of electronic anti-cut, where product-out-of-registration conditions can be sensed and automatically passed without damage to the seal heads and without manual intervention.

The Research Based on the Movement Control CARDS of NC Machining

The paper’s the main research object is the multi-axis servo motor’s sports control using the movement CARDS. It researches and designs the four shafts servo motor control system by using the comprehensive application of movement control CARDS, motor drive, DLL function library and VB high-level language of software and hardware platform. The control system finishes NC machining of the function, using VB program called the function in the movement control CARDS function library.

Linear Interpolation Control of Numerical Control Machine Tools and its Realization Based on Multi-Axis Motion Control Card

The servo system consisting of PC computer, multi-axis motion control card, servo driver, servo motor and load was constructed. The paper studied the interpolation principle and edited the procedure of linear interpolation for two axis servo motors. After the communication between PC computer and servo driver based on the motion control card, the paper edited the control interface program calling the interpolation procedure, which could realize the simulation control and real time control to servo motors. The compare results show the control accuracy of the experiment is higher.

Development of a Liquid Packaging Machine Positioning Control on Moving Film

A liquid packaging machine produces liquid packaging bags from roll film by cooperatively controlling the vertical seal roller, horizontal seal roller, and cut roller. These rollers are driven separately by servomotors as a multi-axis servo mechanism. Positioning control on the moving film is essential to make bags of accurate size. To achieve accurate positioning without lowering productivity, we propose two control methods. One is a two-step velocity control of the horizontal seal roller. This method enables continuous and high speed production of bags of arbitrary size. The second is phase control, which determines the accuracy of the cutting position on the film according to the sealing position. Phase control changes the rotary phase difference of the horizontal seal roller and the cut roller by adjusting the high feeding velocity of the cut roller, or by adjusting the low feeding velocity of the cut roller. The control system developed was applied to a DANGANV liquid packaging machine.

Design of Precise and Efficient Synchronized Multi-Axis Control Servo System

Having studied the synchronized multi-axis control servo system, some type automatic wire striping and terminal crimping system is developed in the paper. In order to realize the precise and efficient synchronized multi-axis control, the PVT (Position-Velocity-Time) algorithm is adopted. This algorithm allows user to specify the time interval of each axis’ motion segment, so the multi-axis working sequence can be easily established in a tight way which augments the system processing speed and guarantees the system stability. Besides, by specifying the position and speed value at the processing point, the positioning accuracy and speed requirement at the processing point can be reached. In the design of the system control software, the modularization design is employed. This modularization idea simplifies the complex software design and allows people use the software more easily. Finally, the experimental result shows the system has a good synchronization performance, and meets the requirements of high efficiency, stability and positioning accuracy in practical production.

Precise position synchronous control of multi-axis servo system

This paper describes a precise position synchronous control of multi-axis rotating system. The control strategies to achieve precise servo system are summarized in two main points: an acceleration control is adopted in an inner loop to ensure robustness of speed of each axis against disturbances, and then a maximum error comparison method has been introduced to minimize not only position synchronous errors but also speed errors of all motor axes. At first, the system dynamics including dc motor drive are rigorously presented by using motor circuit equations and Newton’s formulation. Next, the acceleration and speed controllers are readily designed via proportional-integral (PI) control law. Also, to reduce position synchronous errors caused by different motor dynamics, each axis is coupled by the maximum error comparison scheme. The control system presented is investigated through extensive simulations under step- and sinusoidal-type disturbances. Finally, it has been shown that experimental results successfully demonstrate the effectiveness of the proposed control system for four-axis position synchronous control.

1P1-C22 液体充填包装機の開発(第2報) : ロール制御の最適化による位置決め精度の向上(生産システム・生産機器メカトロニクス)

A liquid packaging machine produces liquid packaging bags by controlling a side seal roll, an end seal roll, a cut roll coordinately. These rolls are driven by servo-motors separately as a multi-axis servo mechanism. In this paper we propose a two steps velocity controller to produce bags of arbitrary size and a phase control system which determines the cut position on a film according to the seal position. The control system changes the rotary phase difference of two rolls by changing the velocity reference of the cut roll. Experimental results using a liquid packaging machine show the effectiveness of the proposed control system.

Design on Odd-even Steps Third Order Approach Interpolation Algorithm for Logarithmic Curve

Logarithmic curve interpolation is essential for precise machining conical cutters with constant rake and spiral angle in CNC machine. In this paper, a novel odd-even steps third order approach algorithm is presented to realize the logarithmic interpolation. In each interpolating cycle there are odd and even steps divided. At the odd step, the interpolating point moves in tangent direction for an instruction interpolation length. The even step is in succession to interpolate same length through the coordinate increments computed by using the Taylor Mean-value Theorem in third order approach algorithm for the interpolation point approaching the ideal curve closely. The third order approach interpolating formulae for calculating coordinate increments are deduced in the results with simplified arithmetic operations that can be quickly computed for real time application. Test results indicate the third order approach algorithm is featured with high accuracy, suitable to be executed by the 32-bit micro-processor in ARM9 embedded CNC system for multi-axis servo control to accurate grind the conical teeth.

Synchronisation control of parallel dual inverted pendulums driven by linear servomotors

Synchronisation control of multi-axis servosystems has recently attracted the attention of researchers, but the issue of synchronisation for multiple inverted pendulums (IPs) is rarely discussed. With this in mind, the authors present a control design of a parallel dual IP system (PDIPS) in which two IPs driven by a pair of linear servomotors allow for parallel movement. The control problem of coupling IPs involves both balancing and synchronous tracking control. A robust design is investigated to enhance internal dynamic stiffness and achieve balance control of the PDIPS. Furthermore, a synchronisation control scheme with a coordinated compensator is proposed to perform a viably congruent dual-axis motion. Experimental results are given to verify the feasibility of the illustrated method. When compared with the classical master-slave control, the proposed control scheme has the advantage in that it can significantly reduce the synchronisation error in command tracking and can generate coordinated motion on both axes.

Real-time NURBS interpolation using FPGA for high speed motion control

Modern motion control adopts NURBS (Non-Uniform Rational B-Spline) interpolation for the purpose of achieving high-speed and high-accuracy performance. However, in conventional control architectures, the computation of the basis functions of a NURBS curve is very time-consuming due to serial computing constraints. In this paper, a novel FPGA (Field Programmable Gate Array) based motion controller utilizing its high-speed parallel computing power is proposed to realize the Cox–de Boor algorithm for second and higher degrees NURBS interpolation. The motion control algorithm is also embedded in the FPGA chip to implement real-time control and NURBS interpolation simultaneously for multi-axis servo systems. The proposed FPGA-based motion controller is capable of performing the Cox–de Boor algorithm and the IIR (Infinite Impulse Response) control algorithm in about 46 clock cycles, as compared to the 1303 clock cycles by the traditional approach. Numerical simulations and experimental tests using an X – Y table verify the outstanding computation performance of the FPGA-based motion controller. The result indicates that shorter sampling time (10 μs) can be achieved for NURBS interpolation which is highly critical to the success of high-speed and high-accuracy motion control.