SEATTLE — It's the dumb device that makes precision movement possible. Rotary encoders play a crucial role in motor control systems, providing information on the position and movement of motor shafts. This information, in turn, can be used by developers to control motor action for such purposes as precision movement and energy efficiency.
For the most part rotary encoders are dumb devices that simply provide pulse signals to a higher-level controller, but their intelligence may well be growing.
Last year, CUI, Inc., introduced its AMT line of capacitive rotary encoders with built-in intelligence. More recently, the company released its AMT Viewpoint GUI software to help unlock the intelligence of its encoders. The combination has earned the AMT line a finalist position in the upcoming Golden Mousetrap Awards competition by EE Times' sister publication Design News.
The key to the AMT family's intelligence, according to CUI's VP of motion control Jeff Smoot, is the inclusion of a microcontroller and custom ASIC in the design. The use of a microcontroller, Smoot told EE Times, gives the encoder a considerable degree of versatility, providing developers with the ability to quickly configure the encoder's resolution, zero position, pole count, and the like. Configurable resolution, for instance, lets a developer adjust the encoder for optimum match with a PID control algorithm, Smoot noted, rather that changing parts. A configurable zero position, he added, can greatly reduce the time needed to install and align the encoder/motor combination by eliminating the need to manually rotate them to the index position before locking them down.
Intelligence in the encoder also allows the device to offer built-in diagnostics, which Smoot notes can help both developers and end-system users. Diagnostic data helps the developer during design by working to eliminate the encoder from the suspect list during debugging. Diagnostics help in the field by providing insight into encoder health before failures occur, and help separate encoder behavior from any preventative maintenance analysis of motor operation that might seek to identify issues such as misalignment or bearing wear. Smoot adds that the built-in diagnostics can also allow systems to verify that encoders are operating before engaging motors in critical motion-control applications, to avoid possible damage.
For now, this degree of intelligence in rotary encoders appears to be unique to CUI, but the concept may well grow on motor control developers. Smoot will be making a presentation outlining the value of such controllers at this week's Motor & Drive Systems Conference in Orlando. The company also offers a whitepaper on the subject.
— Rich Quinnell, Editor, Industrial Control DesignLine, EE Times