Harsh environments require resolvers to be installed as feedback devices. However, very few stepper drives/controls are configured to support resolvers.
To counteract this, Empire Magnetics – one of the leading manufacturers of quality motor products designed to perform in environments and applications where ordinary motors are unsuitable – have, for many years, provided an RDE product to support the resolver and output Encoder type A,B,Z signals.
Whilst an acceptable interim solution, the RDE has resulted in some customers having issues with loss of power, culminating in the loss of position and, for multi-turn applications, absolute position information. But, Empire Magnetics has addressed both these issues in their new ERD product, which has:
- Retained the primary function of the resolver to encoder A,B, Quadrature and Z reference signals (for those happy with incremental feedback)
- Added an up-down counter that tracks absolute position over many turns
- Additional feature to capture the last position in the case of power failure. This absolute position information is available via Ethernet. Commands to zero or install an offset number are 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 jumper change on the board supports a resolution of 16,384 counts per turn of the resolver.
The up-down counter has a range of – 2147483648 to + 2147483647 counts.
At a resolution of 4,096 counts per turn of the resolver, the unit supports 524,288 turns in either + or – direction from the zero point, operating in a mode where the direction reverses will keep the counters centered around the zero reference.