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In harsh environments, we typically must install resolvers as feedback devices to survive the extremes of the application. Very few of the stepper drives/controls are configured to support resolvers, so Empire Magnetics has for many years provided an RDE product - Resolver to Digital Encoder - to support the resolver and output Encoder type A, B, Z signals. Some customers have issues with loss of power which equals loss of position, and for multi-turn applications, absolute position information is better than incremental. EMPIRE MAGNETICS INC has addressed BOTH THESE ISSUES in the new product, ENCODER RESOLVER DIGITIZER or ERD.
For those who are happy with incremental feedback, Empire has retained the primary function of resolver to encoder A, B, Quadrature and Z reference signals. They have also added an up/down counter that tracks absolute position over multiple turns. In addition, there is a feature that captures the last position in the case of a power failure. This absolute position information is available via Ethernet. Commands to zero or install an offset number are also available.
Incremental resolution is set at 1,024 cycles per revolution. Common quadrature detection circuitry will decode this to provide 4,096 counts per revolution. However, a software command can be change resolution to 16,384 counts per turn of the resolver.
The up-down counter has a range of -2147483648 to counts. At a resolution of 4096 counts per turn of the resolver, that unit supports 524,288 turns in either + or – direction from the zero point. Of course, operating in a mode where the direction reverses will keep the counters centered around the zero reference.
Model ERD converts brushless resolver signals to two-phase quadrature signals similar to the signals generated by an incremental encoder. A once-per-rev index pulse is also generated. These three signals are available on complementary TTL compatible open collector outputs, which are internally "pulled up" to an external 5 volts through 1,000 ohms. Incremental resolution is set at 1,024 cycles per revolution. Common quadrature detection circuitry will decode this to provide 4,096 counts per revolution.
The ERD supports two options to allow a computer to read out the position. The user must choose which option is to be installed at the factory at the time of purchasing. The option cannot be changed in the field.
Model EDR provides a Web Client server that reports a position as a string of ASCII digits in HTML format. At power on the EDR reads the absolute position of the resolver and then keeps track of the position until the next power cycle.
Model EDR provides a TCP/IP connection that upon receipt of a “p” command reports a position as a string of ASCII digits terminated with a carriage return/line feed. At power on the EDR reads the absolute position of the resolver and then keeps track of the position until the next power cycle. The receipt of a “z” command will make the current position zero. The receipt of an “x” command will close the Ethernet socket connection.
For complete details see: Empire Magnetics ERD.
Cross Company is Empire Magnetic's local engineering resource. If there is anything you need help with as it relates to an application of their products please let us know. Cross Company has many supplier partners that can provide complementary equipment for your motion control solution, including machine and motion controllers, HMI's, motors and drives, feedback devices, and mechanical systems and components. We will be happy to help you from product sizing and selection to price and delivery information.