Development of PLC-based Tension Control System
reaction schemeREN Sheng-le*, LU Hua, WANG Yong-zhang, FU Hong-ya
Department of Mechanical Engineering, Harbin Institute of Technology, Harbin 150001, China
Received 22 May 2006; accepted 22 November 2006
Abstract
Fiber winding tension is an important factor in the molding techniques of composite material which influences the quality of winding product directly, and the tension control is a key technique in fiber winding techniques. This paper introduces a closed-loop tension control system with the programmable logic controller (PLC) with function modules as its control kernel, the alternating current (AC) servo motor as execute element and the radius-following device to accomplish the real-time radius compensation. The mechanism of the tension control system is analyzed and the numerical model is set up. The compensation technique of the radius of the scroll is analyzed. Experimental results show that the system is well qualif
ied with high control precision and high reaction speed.
*The components of composite material fiber winding possess such advantages as low weight, high strength, and high corrosion resistance, and they are widely applied in aviation and aerospace industry. Many researches have shown that improper or unstable tension leads to a strength loss of 20%-30% of the fiber wound components. An ideal tension control system should provide stable and adjustable tension during the winding process [1-3].
With the development of the winding machine, tension controllers have, so far, undergone three stages of development, i.e., mechanical tension controller, electrical tension controller and computerized tension controller[4-5]. With the development of electronic technology and the appearance of the microprocessor of higher cost performance, computerized tension controller came into use. Microprocessor becomes the kernel of the control system and thus cuts down the number of circuits of the electronic control system, which greatly simplifies the system, improves its reliability and makes possible the application of advanced control methods. Therefore, this type of controllers is widely used[6-7].
The tension control techniques are becoming mature and the specifications are being improved in some developed countries. However, the fiber winding industry of China started up late and still drops behind compared with the western countries.
Mechanical tensioners, with low precision and slow response, account for the main part of domestically- applied tensioners, and cannot meet the tension requirements. Therefore, this paper presents a PLC-based tension control system.
1 Set-up of the System Scheme
1.1 Construction of the system
A winding tension control system generally consists of three main parts, namely the unwinder, the processer and the winder, and it may also include the measuring and control parts, ancillary transport apparatus, and a load cell. The type of the winder and that of the unwinder may be one of the two drive types, surface drive or center drive. The surface drive means that a scroll or belt is set on the surface of the winding material and the drive f
orce is generated through friction. The center drive is to set a drive mechanism on the center shaft of the scroll, where the linear speed and the tension force of the winding fiber vary with the radius of the scroll, leading to the so-called “scroll thick”[8]. The phenomenon of “scroll thick” makes the tension control very complex, but the center drive mode is widely applied due to its wide applicability.
1.2 Design of tension control scheme
This system adopts a scheme with a center drive and outward-draw fiber configuration. Since the output torque of the AC digital servo motor is in direct proportion to the fiber tension force and the scroll radius, the output torque should decrease as the scroll radius decreases to acquire a constant fiber tension. The change of the scroll radius can be measured by a radius following device and the sampled radius change then passes through an analog digital converter and is sent to the PLC. By reading the desired value of the tension force, the radius and tension force are calculated with the preset calculating algorithm. The speed instruction and torque limit instruction are issued and digital- to-analo
g converted to output the analog voltage signal to control the servo driver. The servo driver controls the rotating speed and output torque to control the fiber tension. The servo motor’s speed and torque are measured by the pulse encoder and the Hall element and fed back to the PLC system to compose a closed loop system. The mechanism of the system is shown in Fig.1.
The main components in the system include
(1) A Panasonic programmable controller (FP0-C10RS), a 12-bit FP0-A80 and an FP0-A04V
ancilliary conversion module.
(2) A Panasonic AC digital servo driver and servo motor.
(3) A radius-following device including a radiusfollowing arm and a rotary potentiometer.
2 Mathematical Mode
Effective control of the fiber tension is required in fiber winding. Due to the versatility of the core mold shape and winding shape, the linear speed of the fiber is difficult to be kept constant and
the variation principle is extremely complex. Therefore, the influence of the speed on the tension force should be taken into consideration in the mechanical analysis of the controlled object. The PLC with function modules as the control system’s control kernel, and the needed tension can be enacted from man-machine interface through the serial communication between PLC and upper computer. The input of the radius value, the torque feedback and the velocity feedback, the running of the preset calculating algorithm and the output of the system are done by the PLC with function modules.

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