Published March 2017. Revised and extended January 2018.
The development of robotic exoskeletons already began in the second half of the 20th century. Around 1965, General Electric (in the US) started to develop the Hardiman, a large full-body exoskeleton designed to augment the user’s strength to enable the lifting of heavy objects. The first exoskeletons for gait assistance were developed at the end of the 1960s at the Mihajlo Pupin Institute Serbia, and in the early 1970s at the University of Wisconsin-Madison in the US (exoskeleton is second robot in the video below. It is shown after around 2 minutes).
Because of the technical limitations of their time, and the lack of experience and knowledge, it still took several decades until the technology matured and the first exoskeletons were ready for the market.
With the beginning of the 21st century, the first exoskeleton products made their way to the market and are accessible to an increasing number of users. One of the first applications was gait rehabilitation in stroke and spinal cord injured patients. An early example is the gait rehabilitation exoskeleton Lokomat that was released in 2001 and is used in hospitals and rehabilitation centers worldwide. In 2013, the company behind the Lokomat (Hocoma AG) announced the shipment of the 500th device.
Development continued in the first decade of the 21st century at an increasing number of research labs and companies. Towards the end of the decade, several prototypes of military exoskeletons that aim to augment their user’s strength and endurance were presented. Examples are the Raytheon XOS exoskeleton, which is a full body exoskeleton, and Lockheed Martin’s “Human Universal Load Carrier” (HULC) that supports its users to carry a heavy backpack.
Since 2010, several gait assistance and restoration exoskeletons have been presented and gradually introduced to the market. Most of them are designed to enable paraplegic users to leave the wheelchair and walk upright with the support of the device. Examples are the Rewalk device (ReWalk Robotics), and the Indego exoskeleton (Parker Hannifin) that is based on a research system from Vanderbilt University.
More and more of these exoskeletons receive certification (for example, CE in Europe or FDA in the US) for clinical use and also for use outside of medical facilities, which is an important step towards the home market. In September 2016, the company ReWalk announced the 100th exoskeleton delivered for home use.
Besides medical and military applications, several companies started developing exoskeletons for industrial use and just recently (around 2014-2015), the first systems were introduced. Especially for this application, passive systems (not actuated) are increasingly popular, as actuators are not necessary to relieve the exoskeleton user of a payload or bodyweight. For certain applications, even single articulated exoskeletons (only one joint) are sufficient to provide support. This results in devices that are lighter and cheaper than their actuated counterparts.
In an effort to further reduce constraints that can be caused by the size, weight and rigid structure of exoskeletons, the concept of exosuits has emerged in the past couple of years. These soft, robotic devices are primarily made of textiles and can be worn like clothes. They provide support by actuated cables that are integrated into the textiles, or by soft and lightweight actuators (e.g., special pneumatic actuators) situated at the joints.
Pioneering work was conducted by the Wyss Institute at Harvard University that developed exosuits to support walking. Today, several research labs around the world are developing exosuits. In 2017, Rewalk Robotics announced that it licensed the Harvard exosuit technology and plans to release the first exosuit for stroke patients in 2018.
In addition to all the development efforts, exoskeleton producers started to promote their systems to a wider audience to demonstrate their capability and increase awareness. In 2012, Claire Lomas, who has paraplegia, used a ReWalk to participate in the London marathon and crossed the finish line after 16 days. In 2016, she participated in a half marathon and finished after 5 days.
In 2014, a paralyzed exoskeleton user executed a symbolic kick-off at the World Cup in Brazil. He was assisted by a ‘mind controlled‘ (EEG controlled) exoskeleton that was developed as part of the Walk Again project.
In October 2016, ETH Zürich in Switzerland hosted the first Cybathlon, a sporting competition for people with disabilities using robotic assistive aids. One discipline was an exoskeleton race on an obstacle course for people with paraplegia (called pilots). At this demonstration of pilot skills and technology, the exoskeleton users had to solve tasks such as sitting down on a couch and standing up again, walking up and down slopes, stepping on stones (like you would cross a shallow mountain river) and conquer stairs. None of the participating pilots was able to solve all obstacles, and it took the fastest teams more than 8 minutes to finish the 50 m long obstacle course. The next event has already been announced and will take place in 2020. It will show what progress has been made since.
This look back shows that exoskeletons have been around for quite some time, but only recently the developments in the field of robotic exoskeletons really took off and the first systems became available outside of research labs. While today many systems are still limited in their performance, it will be very exciting to see where the technology goes and what opportunities it will present in the future.