Renishaw's RESOLUTE true-absolute optical rotary and linear encoders are now available with a DRIVE-CLiQ interface to enable machine builders to achieve higher performance and greater reliability. Siemens DRIVE-CLiQ is an innovative, powerful communications interface to connect encoder and direct measurement systems with Sinumerik and Sinamics drive components. Renishaw RESOLUTE encoders determine their position immediately upon switch-on and so are particularly suitable for use in high-performance lathe spindles as well as DDR torque motors requiring high levels of precision and motion control integrity. Note that RESOLUTE encoders are available with several other serial protocols as well as DRIVE-CLiQ for connection to a variety of industry-standard drives and controllers.
RESOLUTE DRIVE-CLiQ encoders are said to offer outstanding motion control performance. RESOLUTE's operating principle is analogous to an ultra-high-speed digital camera, capturing images of the scale so that resolutions of up to 1nm can be achieved (32-bit on rotary) even at speeds up to 100m/s (36,000 rev/min on rotary). Advanced optics mean the detection scheme also has intrinsic low Sub-Divisional Error (SDE) and very low noise (jitter), so users can benefit from lower velocity ripple and solid positional stability.
Rugged, reliable and non-contact
Such high-fidelity motion control performance is normally only associated with much more fragile encoders, but RESOLUTE encoders add ruggedness and reliability, with sealed readheads and scales constructed from dependable shatter-proof engineering materials. The non-contact format eliminates bearings, seals, couplings and guideways from the encoder design, thereby also eliminating the most common causes of shock/vibration-induced encoder failure. Even if the main seals on the axis fail, RESOLUTE readheads are sealed against the ingress of oil and coolant; the readhead and scale can simply be wiped, then they will start working again. Downtime is minimised and servicing/repair is simplified.
The non-contact format also helps to improve system metrology. RESOLUTE rotary encoders read a solid stainless steel scale that is locked to the axis shaft so the encoder does not suffer from the mechanical backlash, wind-up and coupling losses that affect traditional enclosed encoders. Rotary scales include options with accuracy better than +/-1 arc second, low-inertia versions and sizes from 52mm to 550mm, with custom sizes also available. Furthermore, the large through-hole enables the encoder to be mounted much closer to the point of interest without complicating the routing of services to payloads. The result is a system with greater dynamic capability, faster settling times and improved repeatability.
Precision-graduated single-track absolute code
Linear encoders, with both stainless steel and ZeroMet (a low-expansion nickel-iron alloy) scales share many of these advantages, mounting directly on the machine's structure or track-guided. With precision-graduated single-track absolute code, linear scales include options with accuracy better than +/-1 micron, or tape scales up to 10m long.
The detection scheme is inherently dependable, featuring advanced cross-checking and high levels of redundancy. Position is calculated when the encoder receives a position request, so true-absolute position is determined every time, meaning miscounting or 'run-away' is impossible. Safety is also enhanced by RESOLUTE's built-in position-checking algorithms. Each time the encoder receives a position request, RESOLUTE determines the position using one algorithm, then verifies that result using an independent position checking algorithm. Any errors can therefore be flagged to the controller before any servo control problem can develop. As a true-absolute encoder, RESOLUTE determines position immediately at switch-on, so complete control of the axis is achieved without any movement, reference returns or battery back-up. Proof of the effectiveness of these safety features is that RESOLUTE is being used in a variety of medical, defence and aerospace applications where reliability of position data is of primary and critical importance.
For machine builders, RESOLUTE encoders are said to be quick and simple to install; the scales are designed for easy installation, the readhead has large set-up tolerances, and the readhead features an integral set-up LED that indicates, by colour, the signal strength being detected and flashes to warn of coding errors. This LED (repeated on the remote DRIVE-CLiQ interface) provides simple diagnostics throughout the life of the encoder too, without the need for specialised set-up boxes.
Follow the link for more information about RESOLUTE true-absolute optical encoders from Renishaw.