Analysis of tension control system of crosscutting machine
During the design of a crosscutting machine, it is important to take into account the effect that tension control system has on the process. If this factor is not considered, it will result in failure of the cutting tool. The following article will discuss the importance of tension control in a crosscutting machine and will give an example of its use. It will also cover the advantages and disadvantages of using various control systems.
Closed loop speed control
Closed loop speed control of a crosscutting machine for paper was a challenge. The task was made a little easier with the help of a cleverly designed PWM modulator. The resulting gizmo is a bit of a hybrid - a circuit board comprised of a microcontroller (MCU) and a host of sensors. The MCU handles the actuation while the sensors monitor the rest of the system in real time.
The most important component is the aforementioned PWM modulator. Aside from controlling the bauble's direction, it also regulates the direct speed of the DC motor. The result is a highly efficient and low-maintenance drive. During transient operations, the aforementioned rated current is augmented by two to 3.5 times that amount.
To maximize torque and to minimize the cost of operating a converter, a closed loop speed control scheme is in order. The drive is tasked with monitoring and calculating a series of outputs from an embedded current sensor. This allows for algorithmic torque calculations that are relevant to the machine's applictions.
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Closed loop torque control
The closed loop torque control of crosscutting machine is an effective method of regulating the motor speed, especially when used with a DC drive. The most common use of this technique is in electric cars and locomotives. The limiting factor in current/torque resolution is the resolution of the reference signal. The following criteria can be applied to evaluate the torque/current response of a drive:
The magnitude of the output/input ratio. The Bode plot represents this metric. The input/output ratio is usually expressed in a ratio of one to ten. The input/output ratio of a torque/current system is often compared with the open loop torque/current performance specifications.
The most important aspect of a closed loop system is its ability to automatically regulate itself. This is achieved by the integration of an encoder into the drive.
A good example of this type of torque control is the ABB ACS850 direct torque control, which provides highly accurate motor torque control. The ACS850 can be incorporated into a variety of machinery applications to meet the performance and production needs of system integrators.
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Open loop tension control
Slitting machine tension is an important factor in the cutting result. In order to improve slitting speed and uniformity, it is essential to control tension in the equipment. There are two main types of tension control systems. The first is open loop motor control and the other is closed loop tension control.
The advantages of using open loop tension control of slitting machine include the simplicity of operation, cost and the ability to be implemented in many different applications. However, open loop control is often not sufficient for a system with a lot of variations. This type of control is sometimes called non-feedback control.
Closed loop tension control, on the other hand, is a more accurate and sophisticated system. It is able to adjust quickly and efficiently to a change in speed or torque. Unlike open loop control, a closed loop system requires direct tension measurement. The most common type of control used in closed loop systems is a dancer roller.
Dancer roll system
A dancer roll system is a control system that uses a preloaded idler roll to impart tension into the web of material. The force produced is dependent on the position of the dancer and the web tension. These are used in closed loop tension control systems to balance the force of the roller with the force of the web.
A dancer can be either a single or double roller. It is usually loaded with air cylinders. However, if a dancer is loaded with mass, it can cause inertia problems.
The main purpose of a dancer is to accumulate a certain amount of web in the direction of the machine. This ensures mechanical stability for large roll build ratios. It also helps to absorb fluctuations in tension. It is especially useful for indexing.
A dancer is controlled by a potentiometer located on the arm of the dancer. It also controls a DC-indexing motor that rotates the winding roll away from the rider roll.
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