Project March IVc – Exoskeleton in action on obstacle course
Exoskeletons that you can don to gain superhuman powers are best known from games and sci-fi movies. Although they are not yet commonplace in everyday life, companies, research institutes and universities have been experimenting with them for years. This happens at TU Delft, for example, where a new student team works on Project March every year.
The aim of this project, which has been running for five years now, is to improve the quality of life of people with spinal cord injury. Project March has been working with spinal cord injury patient Sjaan Quirijns for several years, who can stand up and walk again with the help of an exoskeleton that is tailor-made for her. The goal isn’t to make an exoskeleton that actually hits the market; the project focuses entirely on the research and development of techniques.
With the latest version of the robot suit, the March IVc, the team would compete against eighteen international teams during the Powered Exoskeleton Race at the Cybathlon in Switzerland this year. This is a competition that takes place once every four years and is known unofficially as the Bionic Games. Due to the corona pandemic, the event was canceled, but because the team still wanted to show what it is capable of, it recreated the course with obstacles in Rijswijk and gave an extensive demonstration.
March IVc instead of March V
Project March has been around for five years now and a new exoskeleton has been made every time in the past four years. There were significant changes every year, such as the addition of additional joints. This year, for the first time, last year’s version was used as a basis and further developed. The new exoskeleton is therefore called March IVc. That c stands for Cybathlon, because the choice to develop further was made with that competition in mind. The competition should have taken place in May and the team would not have had enough time to develop and test a completely new exoskeleton.
The March IVc has many similarities to last year’s March IV. It is basically the same as the previous version with its eight joints. The big innovation in that model was the addition of extra hip joints for lateral movements. The exoskeleton therefore has two hip joints per side, a knee joint and an ankle joint.
The exoskeleton also includes shoes, equipped with eight pressure sensors. These provide the team with insight into the distribution of the weight and that insight can be used to maintain the correct balance. To withstand the high pressure that can be put on the shoes, the soles are reinforced with carbon fiber.
Improved handling
Quirijns, who has been involved with Project March as a pilot for three years, controls the harness with a controller incorporated in a crank. The operation is one of the points that have been considerably improved with the March IVc. The controller consists of a screen and a joystick with which the pilot can select and activate various movement options. With a button, the next movement can be selected while the exoskeleton is still moving. It is also possible to adjust the step size without having to stop the skeleton first. This is possible thanks to improvements to the software.
All movements that the exoskeleton can make are pre-programmed with a gait generator . For example, the current version has three different step sizes: small, medium, and large. The exoskeleton now makes a transition gap itself, when switching from a small to a large step, for example. Such an intermediate step is necessary to make the transition with a smooth movement.
In addition to different step sizes, the menu includes numerous moves that are precisely tailored to the obstacles of the Cybathlon’s obstacle course. These movements are first tested in extensive simulation software. That simulator takes into account numerous factors, such as gravity. The pilot must also be simulated. According to chief engineer Eline Gigengack, this is a complicated task, because it is difficult to predict exactly how the pilot will lean during certain movements. By improving this software, the team has made a lot of progress this year.
EtherCAT and dashboard
The exoskeleton works completely wireless. The backpack contains a battery and a master computer that controls all motor controllers. That master is connected to the motors via EtherCAT , or Ethernet for Control Automation Technology. This is an Ethernet-based protocol, intended for industrial applications, with an emphasis on fast synchronization.
Unlike Ethernet, EtherCAT does not work with hubs or switches. Data is sent from the master to all nodes and processed on-the-fly or supplemented and forwarded again. The technology has also been compared to a train that passes a station and can load and unload passengers without having to stop.
The team reads all data generated by the sensors and motors via a dashboard. The dashboard shows the live status and movement of all components. The software can also create minutes semi-automatically. On the basis of this data, the team has improved the reliability of the exoskeleton and has made great strides in the field of balance.
Better fixtures and more feedback
A big improvement for pilot Quirijns are the new fixtures . These are the leg shells with which she is attached to the exoskeleton with her upper legs. These are custom made for optimal support. This makes getting up and sitting down much easier and walking less strenuous. Quirijns has also walked with commercial exoskeletons. They are not custom-made and the March IVc is a big improvement in that respect, she says.
Another new feature of the March VIc is that the exoskeleton provides more feedback to the environment. The backpack contains a speaker and an LED that continuously indicate the state of the robot suit. This allows the team to act quickly if something goes wrong.
When Sjaan uses the exoskeleton, she is always assisted by a number of students for safety. They do as little as possible, but can intervene if necessary. For example, someone walks with an emergency button, with which the device can be stopped. There are also built-in software security measures. For example, if a foot gets caught while climbing stairs, the entire exoskeleton freezes as a precaution.
Competition in November and March VI in 2021
The international Cybathlon in which Project March would participate will therefore not take place this year in its original form, but an adapted competition will follow in mid-November . Teams set up their own infrastructure per country and record the race on video.
The current Project March team will continue until November to participate in that competition, but the next student team is now also ready to throw itself into the project in the new academic year. That team will receive all knowledge and will use it to develop a completely new exoskeleton: the March VI.
In what ways the next exoskeleton will be modified and renewed is not yet known. The current chief engineer does give an example of what the new team could focus on: making the crutches superfluous. The team has already experimented with this in simulations this year, but to actually achieve this, major adjustments to the hardware and software are still needed. Whether that will succeed next year remains to be seen, but it is a follow-up step that will be taken in the future.