White Paper: Robotics, Automation & Control

RLS Magnetic Encoders Enable Marsi Bionics to Build “Life-Changing” Exoskeletons

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Marsi Bionics S.L. is a technology start-up based in Madrid, Spain that designs and builds custom exoskeletons for medical applications with the aim of potentially replacing the wheelchair in everyday life for some patients. Recent advances in robotics have allowed treatment with powered (active) robot exoskeletons that support the patient’s body and enable greatly improved outcomes. The exoskeletons give physically disabled people the freedom to stand, move, and interact with their environment.

RLS, a Renishaw associate company, was chosen by Marsi Bionics to supply the latest in magnetic encoder technology for the creation of two new products: the ATLAS 2030 exoskeleton for children and the MB-Active Knee (MAK) single-joint exoskeleton for adults.

The ATLAS 2030 exoskeleton has up to six degrees of freedom per limb. This device enables the user to perform both unaided and self-actuated actions such as walking and sitting. Full exoskeletons consist of motorized joints, limbs, electronic control, and power systems.

Successful dynamic walking requires precise control of the legs’ joint angles in terms of position, velocity and acceleration via rotary encoder feedback. This is difficult to achieve as each mechanical joint is compliant and includes elastic elements to help mimic and support the real joints and muscles of the human user.

Previously, Marsi used its own custom-made PCB encoders that were fully linked to the kinematic structures of the MAK and ATLAS exoskeletons. But problems regularly occurred because the joint motors generate stray magnetic fields that can interfere with magnetic encoders and cause faulty readings.

Marsi Bionics selected the RLS Orbis encoder for its ATLAS exoskeleton and the RLS RM08 encoder for its MAK knee-joint exoskeleton. The Orbis encoder is a component-level absolute rotary encoder designed for space constrained applications. The encoders met Marsi Bionics’ performance criteria without adding excess weight and volume, as any excess in the structure could be detrimental to the user’s mobility and might hamper the walking movement.

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