This article explores the cost-effectiveness of employing controllers with reduced bit depth for managing electric drives, considering the potential use of more affordable controllers in situations where it may be envisaged for the purpose of cost savings. The paper examines scenarios in which it is permissible to employ simpler control devices and whether this would be advantageous for large enterprises.
Keywords: electric drive, controller, industry, motor, bit depth.
В данной статье рассматривается рентабельность применения контроллеров с пониженной разрядностью для управления электроприводом в контексте возможности использования более дешевых контроллеров в случаях, где это может быть предусмотрено в целях экономии. Статья рассматривает случаи, когда допустимо применять более простые контролирующие устройства, и будет ли это выгодно для крупных предприятий.
Ключевые слова: электропривод, контроллер, промышленность, двигатель, разрядность.
Modern drive controllers typically operate with various bit depths depending on the specific application and system requirements. The most common types of bit depths today include:
- 32 bits: controllers with a 32-bit bit depth are quite common and provide a good balance of performance and accuracy for many applications.
- 16 bits: in simpler systems or cases where resource efficiency is required, controllers with a 16-bit bit depth may be used.
- 64 bits: In some more demanding applications, such as high-precision positioning or complex motion control, controllers with a 64-bit bit depth may be employed.
It can be said that 8-bit controllers are definitely outdated, and finding them in the PLC market is no longer possible. Speaking of 64-bit controllers, devices with such chips on board are considerably more expensive than 32-bit and 16-bit ones, and the use of such PLCs is not always justified since their power is excessive for many tasks [1].
Therefore, the paper will focus on the cost-effectiveness of using 16-bit devices instead of 32-bit ones where feasible.
Evaluating the impact of bit depth in the context of drive control is crucial for understanding the computational resources required to perform operations in the control system, especially when using digital controllers. Bit depth influences the representation of numbers and operations on them, as well as memory consumption and performance.
Let's highlight the key aspects of evaluating the impact of bit depth:
1) range limitation: lower bit depth will limit the range of number representation, which can be a concern when working with large or small values.
2) Speed: increasing bit depth can increase computational costs as more bits require more time for processing.
3) Memory usage: higher bit depth requires more memory to store numbers, which can be critical in systems with limited resources.
4) Energy consumption: higher bit depth may consume more energy, which is important for portable or energy-efficient systems.
5) Refresh rate: increasing bit depth may reduce the refresh rate, which is important for systems requiring rapid response.
6) Operation execution time: higher bit depth may increase the time taken for mathematical operations, which is crucial for real-time systems.
7) Control precision: the impact of bit depth on the accuracy of controlling drive parameters, such as speed and position.
The use of 16-bit controllers instead of 32-bit ones will decrease control precision, increase the program cycle closure time, and reduce the refresh rate. However, is this critical for all types of motors?
Speaking about control precision, it can be said that for many motors, it is critical as they are involved in specific technological processes that require adherence to acceptable standards and where significant computational power is implemented [2]. However, for many motors involved in other processes, this level of control precision may not be as critical. The majority of such motors are represented by motors with a voltage class of 0.4 kV, which are used in the following industries:
- Industrial manufacturing.
In many industrial complexes, where electric motors are used to drive conveyors, pumps, or fans, precision may be less critical.
- Materials processing. Начало формы
In areas related to materials processing, such as in the woodworking industry, precision may not play a decisive role, especially if the motors drive mechanical devices with low precision positioning requirements.
- Pump systems: in pump systems where continuous liquid supply is required, the main criteria are reliability and efficiency. Precision may not be as critical in such systems as compared to other applications.
Speaking about the update frequency in the control system of electric motors, it can be said that the following types of motors do not require high performance in this criterion:
1) Industrial drives:
In industrial drives, such as those used on conveyors, fans, or pumps, the update frequency can be relatively low, for example, within the range of 100–500 Hz, as these systems typically do not require very high dynamic precision.
2) Lifting and Transport Equipment:
In lifting and transport equipment systems, such as cranes or elevators, the update frequency can be moderate, typically within the range of 100–500 Hz, to ensure reliability and precise control.
Speaking about the program cycle closure time, it can be said that this parameter will not be critical for motors used in machining centers, elevators, pumps, and ventilation systems. This is because the cycle for controlling the drives of such motors is short and does not require significant computational power [3].
This approach to using more affordable 16-bit controllers in industrial facilities, such as defense industry objects, furniture manufacturing, and pumping stations, can be justified. It becomes especially advantageous in cases where control over a large number of motors is required in a facility with numerous workplaces. Let's perform an economic calculation for a facility in the processing industry, where multiple workplaces are typically present.
To determine the economic feasibility of using 16-bit controllers, let's analyze the overall costs for controllers for 100 workplaces in a processing industry facility. As of today, the median cost of a controller with a 16-bit processor is 12,000 rubles, while for a 32-bit processor, it is 30,000 rubles. The calculation will look as follows: The cost of 100 16-bit controllers will be:
where
Similarly, the cost of 100 32-bit controllers will be:
where
The average service life, as stated by the manufacturers of controllers, is 8 years with the specified cost.
Let's find the cost of devices, taking into account depreciation:
where
where
Thus, the difference will be 6000000–2400000 = 3600000 rubles.
By conducting the calculation for a hypothetical processing industry facility, where many motors do not require high precision control, it can be inferred that having a large number of suitable workplaces makes it advantageous to use more affordable 16-bit controllers for electric drive control. Simultaneously, within the same enterprise, 32-bit controllers can be employed where high precision control is necessary (such as various CNC machines, metrological equipment, etc.). It can also be concluded that a thoughtful approach to selecting the bit depth of the controller can contribute to cost savings without significant losses in quality.
References:
- Practical Approaches to Establishing Infrastructure for an Industrial Cyber Polygon / O. D. Arkhangelsky, D. V. Syutov, A. V. Kuznetsov // Automation in Industry. — 2020. — No. 11. — P. 52–57.
- Selevtsov L. I. Automation of Technological Processes / L. I. Selevtsov, A. L. Selevtsov. — 3rd edition. — Moscow: Academy, 2014. — 351 p. — ISBN 978–5–4468–0615–7.
- Ivanova T. N. Automation of Production as a Direction for the Development and Improvement of Productive Forces / T. N. Ivanova, A. V. Zhukov // Karelian Scientific Journal. — 2016. — No. 4. — P. 118–120.
