Encoders and speed sensors play a key role in many motion control applications, especially in precision low-speed control applications, such as industrial experiments and measurement, automation and safety monitoring systems.
When a design engineer uses the word "motion control," the first reaction may be a high-speed system that quickly changes direction and speed. High speed and high dynamic motion control applications present technical challenges, but also for the other extreme case, very low speed motion control. Accurate low-speed control is an important issue for many motion control applications, such as industrial experiments and measurement, automation and safety monitoring systems.
For today's applications, it is not uncommon for a high zoom optical system to focus clearly on a target 20 km away. But when the long-distance target moves, things become difficult because of limited vision, and if the target is not followed smoothly, the target will quickly disappear from the field of vision.
If the target is moving at 20 km / h in the range of 20 km, this is equivalent to 0.05 rpm, super slow speed. In order to keep the target in the center of the user's field of view, it is necessary to accurately control the low speed and make a good response to the change of target speed and direction. To keep the target in the center of the field of vision, this means that a coding point greater than 200K or an 18 bit encoding position is required for a range of 20 km. To be in 20, you need to be steady.
The traditional method is to use an encoder on the system drive motor and multiply it by the RPM measured by the gearbox connected to the motor. The higher the gear reduction ratio, the greater the effect of multiplication. This also means more recoil and worse overall response of servo system. Such a system limits the dynamic range and usually cannot track fast moving objects at an appropriate distance of less than 1 km, just as it cannot achieve the required performance at higher speeds.
The updated approach is to use a high-resolution position encoder on the transmission output shaft, which maximizes the dynamic performance of the servo and helps to avoid backlash. As high-resolution encoders are no longer so expensive, this approach is being used more and more widely.
Because the traditional high-resolution position sensing technology has some limitations, design engineers turn to new sensors. These sensors can be considered as a new generation of inductive encoders, especially for high resolution measurements up to 4 million counts per revolution (22 bits). Inductive encoders apply the same basic physics to decoders, allowing them to provide high-resolution, non-contact measurements in harsh operating environments. For operation in dirty or humid environment, engineers no longer need the seals, gaskets or O-rings required by optical encoder or capacitive encoder.
Different from the traditional winding transformer structure seen in the decoder, the encoder uses printed circuit board as its main component. This reduces the form factor, axial height, and allows the use of large calibres. The new design makes it easier for cables, shafts and pipes to pass through the center of the sensor. At the same time, the encoder provides a simple electrical interface with the following characteristics: DC power supply and absolute value, digital output.