What is the difference between an encoder and a resolver in an ac servo motor?

Hey there! As an AC servo motor supplier, I've been getting a lot of questions lately about the difference between an encoder and a resolver in an AC servo motor. So, I thought I'd take a few minutes to break it down for you.

Let's start with the basics. An AC servo motor is a type of electric motor that's used in a wide range of applications, from industrial automation to robotics. These motors are known for their high precision, speed, and torque control, which makes them ideal for tasks that require accurate positioning and movement.

Now, when it comes to controlling an AC servo motor, two of the most common feedback devices are encoders and resolvers. But what exactly are they, and how do they differ?

Encoders

An encoder is a device that measures the position, speed, and direction of a motor shaft. It works by converting the mechanical motion of the shaft into an electrical signal that can be read by the motor controller. There are two main types of encoders: incremental and absolute.

Incremental Encoders

Incremental encoders are the most common type of encoder used in AC servo motors. They work by generating a series of pulses as the motor shaft rotates. The number of pulses generated is proportional to the amount of rotation, which allows the motor controller to determine the position and speed of the shaft.

One of the advantages of incremental encoders is that they're relatively inexpensive and easy to install. They're also very accurate, with resolutions ranging from a few hundred to several thousand pulses per revolution. However, one of the drawbacks of incremental encoders is that they lose their position information when the power is turned off. This means that the motor controller has to perform a homing operation every time the system is powered up to determine the initial position of the shaft.

Absolute Encoders

Absolute encoders, on the other hand, provide a unique position value for every position of the motor shaft. They work by using a series of tracks and sensors to generate a binary code that represents the position of the shaft. Unlike incremental encoders, absolute encoders don't lose their position information when the power is turned off, which means that the motor controller doesn't have to perform a homing operation every time the system is powered up.

One of the advantages of absolute encoders is that they provide accurate position information even after a power outage. They're also very reliable and have a long lifespan. However, one of the drawbacks of absolute encoders is that they're more expensive and complex than incremental encoders. They also require more wiring and programming to install and configure.

Resolvers

A resolver is another type of feedback device that's used in AC servo motors. It works by using a rotating transformer to generate a sine and cosine signal that represents the position of the motor shaft. The motor controller then uses these signals to determine the position and speed of the shaft.

One of the advantages of resolvers is that they're very rugged and reliable. They can operate in harsh environments, such as high temperatures, vibrations, and electromagnetic interference. They're also very accurate, with resolutions ranging from a few degrees to less than a degree.

Another advantage of resolvers is that they don't require any external power to operate. They're powered by the motor's electrical supply, which means that they're very energy-efficient. However, one of the drawbacks of resolvers is that they're more expensive and complex than encoders. They also require more wiring and programming to install and configure.

Differences between Encoders and Resolvers

Now that we've covered the basics of encoders and resolvers, let's take a look at some of the key differences between the two.

Accuracy

Both encoders and resolvers can provide accurate position and speed information. However, encoders are generally more accurate than resolvers, especially at high speeds and resolutions. Encoders can provide resolutions of up to several thousand pulses per revolution, while resolvers typically provide resolutions of a few degrees to less than a degree.

Cost

Encoders are generally less expensive than resolvers, especially incremental encoders. Incremental encoders are relatively simple and inexpensive to manufacture, which makes them a popular choice for many applications. Resolvers, on the other hand, are more complex and expensive to manufacture, which makes them a more expensive option.

Reliability

Resolvers are generally more reliable than encoders, especially in harsh environments. They can operate in high temperatures, vibrations, and electromagnetic interference, which makes them a popular choice for industrial applications. Encoders, on the other hand, are more sensitive to environmental factors and can be damaged by dust, dirt, and moisture.

Installation and Configuration

Encoders are generally easier to install and configure than resolvers. They require less wiring and programming, which makes them a popular choice for DIY enthusiasts and small businesses. Resolvers, on the other hand, require more wiring and programming to install and configure, which makes them a more complex option.

Which One Should You Choose?

So, which one should you choose: an encoder or a resolver? Well, it depends on your specific application and requirements.

If you need accurate position and speed information at high speeds and resolutions, then an encoder is probably the best choice for you. Encoders are also a good choice if you're on a budget and need a simple and easy-to-install feedback device.

On the other hand, if you need a rugged and reliable feedback device that can operate in harsh environments, then a resolver is probably the best choice for you. Resolvers are also a good choice if you need accurate position information even after a power outage.

Our AC Servo Motors

At our company, we offer a wide range of AC servo motors that are equipped with both encoders and resolvers. Our 4000rpm Servo Motor is a high-performance motor that's designed for applications that require high speed and precision. It's equipped with an incremental encoder that provides accurate position and speed information.

Our High Speed Servo Motor is another popular motor that's designed for applications that require high speed and torque. It's equipped with an absolute encoder that provides accurate position information even after a power outage.

Finally, our CNC Lathe Machine Servo Motor is a specialized motor that's designed for use in CNC lathe machines. It's equipped with a resolver that provides accurate position and speed information in harsh environments.

Conclusion

In conclusion, encoders and resolvers are both important feedback devices that are used in AC servo motors. They provide accurate position and speed information, which allows the motor controller to control the motor's movement and performance. While encoders are generally more accurate and less expensive than resolvers, resolvers are more rugged and reliable.

If you're in the market for an AC servo motor, we encourage you to contact us to discuss your specific application and requirements. Our team of experts can help you choose the right motor and feedback device for your needs. We also offer a wide range of accessories and services to help you install and configure your motor system. So, don't hesitate to reach out and let us help you take your application to the next level!

References

• "Servo Motors and Drives: Basics, Selection, and Application" by Peter Nachtwey
• "Motion Control Basics" by Yaskawa America, Inc.
• "Encoder and Resolver Basics" by Honeywell International Inc.