The Evolution of Rotary Encoders: From Incremental to Absolute
In the world of industrial control systems, rotary encoders have played a crucial role in providing precise position tracking and measurement. With the advancement in technology, two types of rotary encoders have emerged: incremental and absolute encoders. In this blog post, we will delve into the working principles, advantages, and limitations of both types, helping you understand the significance of rotary encoders in industrial automation.
Incremental Encoders: The Basics
Incremental encoders, also known as rotary absolute encoders, use a circular grating code disc with two or four photoelectric eyes that read the lines of encoding. Each pulse period corresponds to a specific angle, typically 1 degree. The phase difference between the two eyes (or the four eyes in some cases) allows for direction detection, making it possible to determine the rotation direction.
The phase shift between the two eyes is crucial in determining the rotation direction. For example, a 1/4 phase shift corresponds to a 90-degree phase difference, while a 3/4 phase shift corresponds to a 270-degree phase difference. In addition, each revolution of the encoder produces a zero pulse, known as phase Z, which serves as the reference point for each cycle.
Incremental encoders are often constructed using metal or plastic materials, with the metal engraving limited by its accuracy. However, this type of encoder has limitations in industrial control systems where signals can be affected by external interference, leading to cumulative errors.
The Need for Absolute Encoders
To overcome the limitations of incremental encoders, absolute encoders were developed. These encoders utilize a unique binary code, known as a Gray code, which changes from a power level of 2 to 2^N-1. Each position of the code disc produces a unique Gray code, making it possible to determine the absolute position without any reference point.
Absolute encoders use an optical code disc with lines of different lengths, which are read by multiple optical eyes. This allows for accurate position tracking, unaffected by external interference or device failures. In industrial control systems, this technology has become increasingly popular due to its high reliability and anti-interference capabilities.
The Evolution of Absolute Encoders
In recent years, the development of absolute encoders has led to the creation of multiple-turn absolute encoders. These encoders can measure rotations exceeding 360 degrees by using multiple code discs and reading lines of different lengths. This allows for accurate position tracking, even in cases where the device rotates more than a full circle.
One example of a multiple-turn absolute encoder is the clock mechanism-based encoder, which uses mechanical speed code discs to achieve precise position tracking. This technology eliminates the need for resetting the counter, making it ideal for applications where frequent position changes occur.
Conclusion
In conclusion, the development of rotary encoders has revolutionized the world of industrial control systems. From incremental to absolute encoders, each type has its unique advantages and limitations. Incremental encoders are simple and cost-effective, but they can be affected by external interference. Absolute encoders, on the other hand, offer high accuracy and reliability, making them an essential component in industrial automation.
As the demand for precise position tracking continues to grow, manufacturers are developing new and innovative solutions that address the limitations of traditional encoders. The future of rotary encoders will likely revolve around the development of more advanced materials, improved signal processing, and the integration of artificial intelligence and machine learning. By understanding the evolution of rotary encoders, manufacturers can design more efficient and reliable systems that drive innovation in industrial automation.
