Design considerations for an exoskeleton for children.

Exoskeleton for children maxon DC motors

 

 

Developing Exoskeletons for children present their own engineering challenges simply because children are still growing.

Exoskeletons were largely developed for people that have sustained paralysis or suffer muscular dystrophy. For adults who have stopped growing there is no risk of outgrowing the exoskeleton. However for children their growth and ability present a multitude of challenges for design engineers. An exoskeleton that fits a six-year old perfectly may be much too small by the time the child turns seven. For a child with spinal muscular atrophy an exoskeleton is designed to recognise users are not completely paralysed but are able to move their legs to a certain extent. Sensors within the frame detect weak leg movements and respond immediately to provide support. As a result, the child is able control the exoskeleton directly with the legs.

Spanish company, Marsi Bionics, manufactures exoskeletons mainly for adults but have developed two exoskeletons for children, the Atlas 2020 and Atlas 2030. Weighing approximately 14 kgs it is made for children from 3 years up who have a neuromuscular disease. The exoskeleton can be adapted to various leg lengths and hip widths, so that it also fits teenagers up to about 14 years of age. The “Atlas 2030 is an upgrade of Atlas 2020”, explains Elena García, creator and co-founder of Marsi Bionics. “The main difference is that Atlas 2020 is intended for use in hospitals for gait training and rehabilitation, while Atlas 2030 is designed for use in private homes as an integral part of the patient’s everyday life. Both devices are ready for industrial production and until then, Atlas 2020 will continue to be used in hospitals for clinical research.”

maxon motor have five drive systems in each leg of the children’s exoskeleton. Brushless flat EC45 motors deliver very high torque in a compact design, coupled with inductive MILE encoders that act as sensors. The motors are controlled by servo controllers from maxon’s ESCON series.  “EC flat motors provide the best power-to-weight and power-to-volume ratio”, explained Elena García. “This is a variable of paramount importance, as gait exoskeletons require high power but a very low weight and volume.” The exoskeletons will be made available commercially once CE certification marks have been received.

For more information contact maxon motor Australia Tel. +61 2 9457 7477.

Exoskeleton joint actuator.

 

Gen.1 maxon exoskeleton DC motor drive system

maxon motor have developed the Exoskeleton Drive GEN.1 for use in hip and knee exoskeletons.

The global Exoskeleton market is growing in both market share and technological developments at a rapid rate each year. Maxon motor have several global customers we have worked with to develop brushless DC motor solutions for use in robotic limbs.

Available from the beginning of October 2017 is a complete joint actuation unit consisting of a pancake brushless DC motor (EC90 flat) with inertia optimised rotor, Internal high resolution 4096 MILE Encoder, planetary gearhead with absolute encoder and EPOS4 position controller with CAN and RS232 interface. Fitting the 17bit SSI absolute encoder directly at the joint rotation to a degree will negate the effect of gearhead backlash giving designers increased positioning accuracy. The unit will deliver 54Nm of continuous torque and 120Nm on a 20% duty cycle. The system can be operated on supplies between 10 and 50V DC and the actuation speed is up to 22rpm. Drawings and pricing are now available contact maxon motor Australia for further information.

Tel. +61 2 9457 7477.

DC motor with right angle gear and planetary gear.

photo450pxDC motor with right angle gear and inline gear combined © 2016 maxon motor

A unique DC motor and gearhead combination developed for an Australian customer providing solutions for robotic rehabilitation.

When high power levels and tight space constraints are required, maxon motor tailor a solution. maxon motor Australia recently developed this motor and dual gearhead design for a robotic exoskeleton application for rehabilitation of children with disabilities. Gearing with the high efficiency level of over 98% on the right angle transfer has been achieved with the use of an sealed, oil filled helical bevel design. A custom adaptor section has then been specifically manufactured to affix a 52mm 113:1 ceramic planetary gearhead at the helical gearbox input. The use of ceramic components within the planetary gearhead increases the lifespan typically by three times compared to traditional steel planetary gearboxes. The 50mm diameter 48V 200W DC maxon motor also achieves the high efficiency of 94%. maxon motor are renowned for high efficiency DC motors but the careful design and selection of the drivetrain components in this gear motor system has set new benchmarks. A common 500cpt incremental encoder has been fitted to the motor back shaft and when combined with the gear ratio and maxon motor control software quad counting, gives a system positioning capability of 0.001 degree. Such a fine positioning capability is also only possible with the assistance of the patented maxon motor rhombic coreless winding that gives a completely smooth motion void of any mechanical detent or magnetic cogging.

For assistance with the design and supply of customised DC gear motor combinations contact maxon motor Australia Ph: +61 2 9457 7477.