Use Encoders to Enhance Step Motor System Performance
Because of their low cost, high resolution, precise positioning, minimal control electronics and low cost, step motors are popular in automation. Traditional step motors can be driven in an open loop system without the need to have sensors to send information back to a controller. However, open loop step motors pose challenges.
Complex projects such as quadcopters require enhanced position control. The stepper motors are designed to provide excellent precision and predictable performance. This is possible when both the gearbox ratio and step angle are known.
Stepper motors are now the preferred choice for many electronic devices.
Some engineers go one step further than the stepper motor's excellent visibility into velocity and position.
They have also added encoders in their motor systems to the stepper's open loop control.
The Motor Encoder: Closed Loop Control is essential
An Stepper Motor w/ Encoder can be attached to an electric motor. It can be attached to an electric motor shaft to provide closed-loop feedback signals.
This functionality may seem redundant at first. Is precision control not what the stepper does by itself? It seems that both yes and no. Recent research has demonstrated that even though it may seem unnecessary, the encoder can make a huge difference in the performance of a stepper motor.
Galil, a motion controller manufacturer, conducted side-by-side tests between closed and open loop stepper motors. The team found that an encoder can make a significant difference in performance metrics.
The closed loop system offers:
Significantly improved velocity smoothness
Reduction in overall consumption
Three-phase brushless motors with comparable torque outputs can produce higher torque at lower speeds than comparable three phase brushless servomotors.
Galil's researchers found that stepper motors could achieve "dramatic" performance improvements by integrating a positional-feedback device with a two phase brushless amplifier. Their website contains their testing methods and results.
These are exciting developments in the world of motion control. Engineers of all levels can make stepper motors more powerful and economically viable by using readily available encoder technology.
Which ENCODERS IS BEST?
Optic encoders are a well-established technology. They offer reliable and accurate performance with a wide range resolutions. However, they can be subject to degradation and loss due to oil, dust, and other contaminants. They work best in clean environments. Capacitive encoders use newer technology and offer similar benefits. They provide the same speed and position information as optical encoders. They are also immune to environmental contaminants.
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