In motion control, feedback devices often play a vital role. For the precise coordination of both speed and position, servomotors often leverage the feedback from encoders. Without getting into the technical operation of an encoder, it is an effective feedback device that needs to be applied with various conditions in mind. To make it worthwhile, one has to correctly specify the condition and application for the encoder and ensure a proper environment.
Things to Consider
Depending on the application, an encoder is selected. Here are the factors to take into account:
Firstly, environmental conditions have to be taken into consideration. Things like moisture, temperatures, vibration, shock, contamination, and so on. The type of motion that the feedback (unidirectional or bidirectional). It would help if you also accounted for the magnitude of movement, the sensitivity to rehoming, and so on.
You need to also have a budget in mind; while the mechanical design, compliance, and electrical requirement are also important considerations, having a budget as a beginning point is crucial. Accumulate as much information as you can before you opt for a model.
Feedback Location
As for servomotor-powered systems, the motor controls ought to be accurate, reliable, and fast. However, even the most expensive ones are subject to external degrading factors. Also, servo applications may utilize more than one feedback scheme. These are dependent on location, operation type, and mechanism.
For location control of feedback devices, the best location is around the load. However, mechanical play can create errors in regard to position, which is why slippage may also place loads in areas where it should not. When mounted in the load directly, the sensors would eliminate errors such as the ones mentioned.
Absolute VS. Incremental Encoders
The position reporting done by feedback devices happens in either of the two ways: Absolute or Incremental. An absolute position operates by sending reports that emphasize its literal position through an electrical system-power-up cycle. On the other hand, the incremental position reporting sensor usually would only provide output pulses for an increment of motion. The system locates the signal by counting its pulses.
The ones equipped with incremental encoders have to be homed or set to a known position. Setting it at a known starting position helps in tracking how far the load has traveled through incremental movements. With the help of a position memory, the system is able to provide an absolute position. When the power is gone, the system forgets the position, however. To mitigate the issue, one can connect the controller to a UPS.
Finding the Right Encoder for you
If there is motion, there is an encoder involved. Mainly two types of encoders are commonly seen, which are linear and rotary. The linear ones measure linear speed and motion, while the rotary measures rotation. The second one is more common than the first.
The ones used with motors come either equipped with bearings. Some modular encoders utilize a bearing set that is pre-equipped. The ones that have bearings are usually employed when the shaft has a high chance of axial runout.
Modular encoders, on the other hand, use a stable application shaft that’s achieved through a mechanical system. The shaft holds the rotation code wheel in location depending on the sensor capability of the encoder. Such encoders like these must be applied to the application shaft. This does not, however, increase the expense in any way.
Rotary and linear encoders may utilize magnetic or optical technology as means of position detection. Optical ones are more common, providing higher resolution and accuracy, whereas the magnetic encoders have an advantage in applications where you do not want to control the environment where it is operating in tightly. It’s more adaptable and can be used in a comparatively harsher environment. Not all encoders are built the same way as to why finding a quality encoder from a qualified encoder manufacturing company is recommended.