Servo Motor Encoder

Reduce Costs
The most obvious advantage of servo motor encoders is the reduction of replacement and inventory costs. Instead of stocking encoders of different line counts, one servo motor encoder will suffice. However, as any frequent user of encoders may realize, programming only the line count does not account for other parameters, such as the output signal voltage or marker pulse alignment. The best option is to obtain an encoder that offers several programmable parameters.

Save Time
Setting the marker pulse (marker pulse indicates an absolute position within a revolution of the encoder) at any given point based on the user’s preference reduces setup time of an encoder. Usually, when an incremental encoder is installed, the marker/zero pulse is used as a reference signal. In some applications, an oscilloscope is used to monitor the channel so the encoder shaft can be carefully adjusted to trace the starting point.

Gain Flexibility
Another great benefit of using servo motor encoders is the flexibility they offer. Programmable encoders are an indispensable tool for OEMs and machine designers when component procurement is required for a project but the actual design requirements are not fully defined. Programmability offers the flexibility to match any changing needs of the end user.

Increase Programming Options
With all the advantages programming offers, end users need to be aware of the different programming methods available in the market. The programming options include DIP switches, stand-alone tools,

serial/USB interface and control system
integration using a PLC or an HMI unit. Selecting the appropriate tool is dictated by the end user’s preference, with greater prominence given to the simplicity and accessibility of the programming tool.

Improve Diagnostics/Condition Monitoring
The programming software interface can be used as a condition monitoring tool as well as for monitoring parameters like position or angle during the initial integration, or when performing maintenance or making adjustments while running operations. Programming tools can be used in the field to remotely read label information of encoders that are not easily accessible, reading the electrical parameters that the servo motor encoders are currently set to and also testing operation of the encoder when in use on the line by displaying the position and pulse count data.

The next factor impacting servo motor encoder selection is the mounting option, and the most common options are:

Shafted servo motor encoders: Uses a coupling method to connect the servo motor encoder shaft to the motor shaft. The coupling provides mechanical and electrical isolation from the motor shaft but can add cost via the coupling and the longer shaft length required to mount the servo motor encoder.

Hub/Hollow shaft servo motor encoders: Hollow shaft encoders directly mount to the motor shaft via a spring-loaded tether. This method is easy to install and requires no shaft alignment, but proper care must be taken to provide electrical isolation.

Bearingless servo motor encoders: Also known as ring mount, this mounting option comprises a magentic sensor assembly in the form of a ring mounted on the motor face and a magnetic wheel mounted on the motor shaft. This type of servo motor encoder mounting configuration is mostly found in heavy-duty applications like paper, steel, and cranes

An encoder attached to a servo motor is used with a controller, computer, and special software that knows the mechanical setup of the system and the relation between the actual position and the position commanded by the controller. This “closed loop” control method gives precise position feedback to control motors and other electromechanical systems for accuracy and precision.

A PC or personal computer can run the software that controls these servo systems. Still, more specialized controllers are now available from companies that perform this function with greater reliability.

The closed loop concept maintains continuous two-way communication between the controller and encoder. The controller gets feedback on how far it has moved from its zero point at all times as it moves toward the desired position.

Choosing the right encoder for your servo motor
The right choice of the encoder is very important for normal operation. It always combines accuracy, ease of use, and price.

There are several aspects of a servo system that determine which servo motor encoder type will work best.

Linear or Rotary
Linear encoders are used to track motion along a straight line, as in a laser scanner or cut-to-length machine.
Rotary encoders (aka shaft encoders) are used when there is rotational movement, as in a robotic arm, milling machine or flight simulator.

Incremental or Absolute
Absolute encoders track position using a unique bit of code for every point of rotation. Because absolute encoders can report exact position without homing, they’re used in applications like surgical robots and other instances where re-homing would be problematic.
Incremental encoders track position by using a reference point, which means they need movement to report change in angular position. Servo motor incremental encoders are highly customizable and used in many different motion control applications where re-homing on startup is not an issue.

Solid or Hollow Shaft
Solid shaft encoders have a rod which must be matched to the width and length of the servo motor’s actuator dimensions using a mounting flange and coupling. Typically, larger than hollow shaft encoders, solid shaft encoders are commonly used in applications with measuring wheels such as conveyor belts.
Hollow shaft encoders are mounted directly on a servo motor. Hollow shaft encoders that use integral bearings in their construction will use a spring tether, making them more resistant to shock and vibration. Bearingless hollow shaft encoders mount directly to the motor frame. Hollow shaft encoders are ideal for dynamic motor control applications.

Operating Environment
The environmental conditions where the servo motor encoder will be used are an important consideration. Temperature, moisture, shock, vibration, presence of chemicals, particulates or electromagnetic interference can all affect encoder performance. A fully enclosed (IP66) optical rotary encoder such as the QR145 is ideal for use in demanding environments.
Applications in tight spaces may require a compact or low-profile encoder. Quantum Devices offers miniature rotary encoders with built-in commutation, reduced space requirements and low-to-no-noise operating profiles.

Electrical Requirements
Incremental encoders use an output driver to send digital signals to a readout device. Output driver selection should be based on the voltage requirements of the controller and drive. Without sufficient voltage, the signals can’t be transmitted across the network. Quantum Devices encoders offer versatile electrical configurations and several commutation options.