Novel exoskeleton enables wheelchair users to rise up and walk

The ReWalk concept was modelled in CAD software by Taga, who did the design, mechanical and electro-mechanical aspects (though not the electronics and software) for Argo.
All rights reserved to Taga
Date:1 February 2013 Tags:, , , ,

A novel robotic exoskeleton suit holds out hope for wheelchair users. By Anthony Doman

We know that it’s pure fantasy when billionaire industrialist Tony Stark slips on his ingenious powered suit to transform himself into Marvel Comics’ Iron Man. But, although today’s real-world robotic suits may not provide superhero powers, they promise something equally unimaginable for wheelchair-bound people: the ability to stand and walk unaided – just about – on their own.

One man pursuing this dream is Andrew Merryweather of Cape Town, left paralysed after an attack at a filling station convenience store six years ago (see “A life-changing moment”). Merryweather has begun raising the formidable R700 000 necessary to obtain an Argo ReWalk exoskeleton suit. The suit consists of a light wearable brace support suit. Motors power knee and hip movement, monitored by a range of sensors under the control of a computer. Built-in algorithms analyse body movements, and trigger and maintain gait patterns for up to eight hours.

Besides mobility, such a device could improve – through regular activity – areas such as bone density and muscle strength, cardiorespiratory and bowel/bladder function, and sitting posture.

Born out of necessity

Amit Goffer has a very personal interest in the ReWalk. You see, Dr Goffer – an electrical engineer – is himself quadriplegic. Just four years after the 1997 car accident that left him paralysed, he founded Argo Medical Technologies in Israel.

According to Argo, the principles of its original ReWalk technologies, already in use at rehabilitation centres, have been developed into the ReWalk Personal, designed for use in everyday life.

The ReWalk controls movement by sensing subtle changes in centre of gravity. A forward tilt of the upper body triggers the first step. Repeated body shifting generates a sequence of steps. The more efficient the ReWalk wearer makes his walking movement, the faster he can go.
The suit has different modes (from sitting and standing to walking up a flight of stairs), selectable from a wrist-worn remote control. This effectively restores self-initiated walking without needing tethers or switches to begin stepping, says Argo.

The system can accommodate users between 1,6 and 1,9 metres tall and weighing up to 100 kg. As long as they can use their hands and shoulders, and have a healthy cardiovascular system and bone density, they are able to use the device.

The UK’s first ReWalk user, Claire Lomas, completed this year’s London Marathon to raise funds for spinal research. Lomas has a T4 spinal cord injury – effectively, paralysis from the chest down – after a riding accident.

Argo is by no means alone in its quest for personal re-mobility tech. Ekso Bionics of California expects to launch a personal version of its therapy device in 2014. Its previous products included a walking aid, the Exohiker, and the Human Universal Load Carrier, licensed to Lockheed Martin, an American defence contractor.

The current Ekso uses two high-capacity lithium batteries to drive the hip and knee motors. Like the ReWalk, it fits people between 1,6 and 1,9 metres tall and weighing up to 100 kg. Fitting and adjustment takes just 10 minutes; according to Ekso, an experienced user can strap the device on or remove it in under 5 minutes.

The user’s physiotherapist operates the Ekso with a remote control, teaching the patient body positioning, balance, and how to shift weight in preparation for taking a step. Intermediate patients can trigger successive steps themselves with a pushbutton, allowing the physio a more hands-on approach.

Advanced users trigger the device by leaning forward and shifting their weight laterally. A recent upgrade involves a wireless networked monitor that provides feedback, allowing patients to control the unit autonomously. As the patient progresses, the walking pattern – that is, speed and stride length – can be adjusted. A speed of up to 1,6 km/h is possible. Prices are reported to be around R1,4 million, though that is expected to drop significantly as the market develops.

The sky’s the limit

Of course, with technologies such as these, the military are never far away. The abilities of an exoskeleton suit could be a boon to soldiers in the field, a “power assist” for individuals engaged in extreme manual labour – and a workout aid for astronauts.

Nasa’s X1 suit was created to help astronauts work out effectively during long spells in outer space. Developed in collaboration with the Florida Institute for Human and Machine Cognition (IHMC) and Oceaneering Space Systems of Houston, it is a spin-off of Nasa’s Robonaut 2 project to send robots
to space.

Its “inhibit” mode provides resistance, giving a workout that would not otherwise be possible in zero-gravity conditions. Its reverse mode helps movement and stability, and could benefit paraplegics.

The X1 is worn over the legs with a harness that reaches up the back and around the shoulders. It has 10 degrees of freedom, or joints: four motorised joints at the hips and the knees, and six passive joints that allow for sidestepping, turning and pointing, and flexing a foot. Multiple adjustment points allow the X1 to be used in many different ways and it can measure, record and stream back, in real-time, data to flight controllers on Earth. In time, the technology could provide a robotic power boost to astronauts as they work on the surface of distant planetary bodies with different gravity to Earth’s.
But down here on the ground, the needs are simpler.

“I’m hoping I will be able to move away from the wheelchair,” Merryweather says. “I could walk in the suit for 10 hours a day instead of having to be seated.”

Costs are a huge factor, of course. Having said that, even his wheelchair costs R45 000 – and it is meant to be changed every five years. “The suit,” he says, “is forever.”

Related material
Video: Argo ReWalk exoskeleton
Video: Nasa’s X1 robotic