Laser communications terminal from Tesat-SpacecomLaser communications terminal from Tesat-Spacecom
Additive manufacturing industry leader Renishaw has, in collaboration with Tesat-Spacecom GmbH, announced the launch of a new space-qualified encoder, with high-radiation hardness, high-accuracy and qualification for 15 years' lifetime in a GEO space environment.
The encoder has been developed using Renishaw's advanced encoder technology, combined with Tesat-Spacecom's knowledge and widespread experience of developing ruggedised electronic systems for use in space applications.
The readhead is designed to survive harsh environments, with 150 g vibration resistance and wide operating temperature range, combined with an extremely robust optical detection principle. Particular attention has been paid to radiation hardness, resulting in the encoder achieving qualification for 15 years use in GEO space conditions. The readhead has a mass of only 300 g and power consumption is typically less than 1 W.
The scale comprises a stainless steel ring with graduations marked directly onto the periphery, thus eliminating shock and vibration-induced breakages associated with traditional glass discs. The graduations include IN-TRAC™ reference marks that are directly embedded into the incremental channel, arranged in a distance-coded pattern so that the distance between any two adjacent reference marks is unique. This means that only a small rotation is required before absolute position is determined by the on-board FPGA (field-programmable gate array). The ring format enables easy integration into rotary axes, with a large through-hole to allow easy routing of supplies.
The ring is mounted directly to the rotor, with the head mounted to the stator. There is no contact between the two parts, so there is no need for separate bearings or flexible couplings. This arrangement improves reliability and eliminates backlash, shaft wind-up (torsion) and other irregular metrology effects that plague traditional enclosed encoders.
High accuracy has been achieved, with short-range error less than 0.5 µrad RMS and long-range error less than 5 µrad (without mechanical errors). Combined with resolution of less than 0.5 µrad, the system is well-suited to applications demanding precision metrology.