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RESOLUTE data sheet - .PDF file.

Materials testing specialist Instron is using Renishaw’s RESOLUTE optical encoders in both axes on its ElectroPuls E10000 and E3000 all-electric test instrument for linear-torsion testing in biomedical/biomechanical research applications.

ElectroPuls systems are intended for fatigue testing, which examines the behavior of materials under fluctuating or cyclic loads in the elastic regime.

Conventional servo-hydraulic test instruments use a linear variable differential transformer (LVDT), a type of inductive absolute encoder, to determine the linear direction of travel and position of the actuator.

ElectroPuls is driven by a linear synchronous motor and requires additional high-quality velocity feedback for precise dynamic control – due to the challenges of driving linear motors with lower inherent damping than traditional rotary designs. While suitable for position control, an LVDT suffers from relatively poor signal stability and cannot therefore produce accurate velocity measurements. An LVDT may also be susceptible to magnetic fields produced within a linear motor and exhibits increasing non-linearity over longer axes.

Optical encoders, with their intrinsically better signal stability and higher accuracy, are superior in this application. Instron selected the RESOLUTE from Renishaw.

The ElectroPuls E3000 linear-torsion machine requires both linear and rotary absolute encoders for the linear and rotational axes respectively. Linear position is provided by a RESOLUTE readhead and an RTLA tape scale with ±5µm/m accuracy and 5nm resolution. Angular position is determined by another RESOLUTE reading a 115mm-diameter RESA ring, offering a resolution of 0.019 arc second and an encoder accuracy of ±2.5 arc second.

Click on the link above to download the RESOLUTE data sheet.

Key application benefits

  • Instron specified that the chosen encoder be reliable, highly accurate, compatible with BiSS serial communications, easy to set up and install, and non-contacting to eliminate friction/wear and therefore mechanical hysteresis error. Renishaw’s RESOLUTE met all the requirements.
  • RESOLUTE offers linear resolutions of 1nm and speeds beyond 20m/sec.
  • Graham Mead, principal mechanical engineer for Instron ElectroPuls, said: ‘With the RESOLUTE absolute linear encoder, we are able to get all the functionality and accuracy from one device. The reduced assembly complexity and number of parts allows much simpler set-up and maintenance-free operation.’
  • He added: ‘The use of the RESOLUTE ring encoder for the rotary axis perfectly complements the linear encoder. It provides superior resolution, accuracy and mechanical simplicity over our previous belt-driven, conventional rotary encoder.’
  • RESOLUTE with BiSS protocol offers Instron advanced capabilities that continue to support new developments in the ElectroPuls series.

Renishaw

A world leader in engineering technologies, Renishaw’s core skills in measurement and precision machining serve sectors as diverse as dimensional metrology, spectroscopy, machine calibration, motion control, dentistry and surgical robotics.

A world leader in engineering technologies, Renishaw’s core skills in measurement and precision machining serve sectors as diverse as dimensional metrology, spectroscopy, machine calibration, motion control, dentistry and surgical robotics.

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