Nacházíte se zde: Úvodní stránka - Snímače polohy - Optické lineární snímače - Systém pro lineární snímače FASTRACK™ s absolutní nebo inkrementální stupnicí - Přesnost

Výhoda přesnosti systému FASTRACK™ pro optické lineární snímače

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In addition to the ruggedness of hardened stainless steel construction, quick installation and the convenience of easy scale removal/replacement (even with limited access), FASTRACK with RESOLUTE™ and TONiC™ also offers real-world performance advantages!

Higher accuracy for linear encoders

Typical accuracy graph for FASTRACK­™ linear encoder scaleThanks to Renishaw’s advanced graduation process, RTLC and RTLA scales for FASTRACK provide ±5 µm/m specified accuracy without compensation. Even more impressively, the actual installed accuracy results are typically close to ±2 µm/m; a significant leap ahead of the competition in a key performance criterion. Furthermore, linearity is strictly controlled to enable very high accuracy to be achieved with a simple 2-point compensation using Renishaw’s XL-80 calibration laser.

The graph shown displays a typical accuracy result of RTLC and FASTRACK without compensation.

Click on the graph to enlarge

Metrology advantages

Typical FASTRACK™ linear encoder system hysteresis graphFASTRACK’s unique design is capable of retaining scale securely at very high acceleration loads, yet minimises drag between the two components to allow free expansion of the scale at its defined expansion coefficient. Hysteresis is therefore also kept to a minimum… less than 1 µm on a centre-clamped 2 metre axis on an aluminium substrate, over the entire operating temperature range!

Another unique metrology advantage of FASTRACK comes from the clamping method that locks the scale to the substrate at a single point without distorting the scale; a significant improvement over the clamps used on traditional carrier-type encoders. This arrangement enables the system builder to clamp the scale at the ideal point for the machine without compromising accuracy in that region; a feature that’s particularly important for centre-clamping of a high accuracy axis.

Click on the graph to enlarge

Improved motion control performance

Typical jitter graph for FASTRACK™ linear encoder scale with TONiC™ incremental encoderTONiC uses the latest generation of Renishaw’s unique filtering optics, tuned for even lower noise (jitter), further enhanced by dynamic signal processing including Auto Gain Control and Auto Offset Control. The result is low sub-divisional error (SDE) giving smoother velocity control for improved scanning performance and increased positional stability. The 1 nm version of TONiC (available from September 2009) features additional noise reduction to achieve an amazing jitter level of 0.5 nm RMS!

Typical sub-divisional error graph for RESOLUTE™ absolute encoderRESOLUTE’s astonishing performance is the result of a sophisticated, reliable and completely unique method of operation. Think of RESOLUTE as an ultra-fast miniature digital camera, taking photos of a scale that consists of a long, non-repeating bar code. RESOLUTE analyses these photos to determine position to resolutions as small as 1 nanometre (1 billionth of a metre) and with remarkable low noise (jitter) and SDE (Sub-Divisional Error, the error within a scale grating period). This provides encoder feedback of superior fidelity, to ensure smoother velocity control and rock-solid positional stability.

Click on the graphs to enlarge

Ultimate toughness!

FASTRACK is specifically designed for applications that may expose the scale to damage. Both the FASTRACK and scale is made from hardened stainless steel to resist damage from dropped glass panes, dropped tools, or other accidental impact. Even when damage occurs, sophisticated optics and high dirt immunity mean that incurred damage often has negligible effect upon signal level.

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Typical FASTRACK™ linear encoder system hysteresis graph

This graph is used to determine the hysteresis of a FASTRACK installation on any substrate and for any temperature range. The x axis represents “relative dilation”, ie, the difference between substrate expansion and scale expansion. The y axis shows the hysteresis that occurs due to drag of the substrate expansion on the scale. To use this graph, first calculate the relative dilation using the formula:

Relative dilation = (substrate expansion coefficient – scale expansion coefficient) x temperature change

Now move along the y axis until you reach the line that most closely matches the “free length” of the scale, ie, the length between the end of the scale and the position of the clamp.

Example: a 2 metre axis clamped in the centre, mounted on a granite substrate, with a temperature range of 20°C.

Relative dilation = (8 µm/m/°C – 10.6 µm/m/°C) x 20 = 52 µm/m

At a relative dilation of 52 µm/m, the 1 metre free length line is at 0.426 µm. Therefore, for the conditions described, the hysteresis will be 0.426 µm.

Další kroky

Kontaktujte nás on-line, požadujete-li další informace nebo máte dotaz na cenu, případně můžete chtít hovořit přímo s vaším místním zastoupením společnosti Renishaw.