Design MARCH IV

 

The MARCH IV is the fourth prototype in the series of MARCH exoskeletons. The design of the suit was presented on 24 April 2019 by the fourth team of Project MARCH.

Some important improvements are the hip joint that can move sideways, a large software update and pressure soles that make research into balance possible. The complete exoskeleton is revealed on August 13th. Subsequently, it will participate in the Cybathlon Experience in September 2019. The following year, the fifth team of Project MARCH will work on the fourth exoskeleton to improve it in the run-up to the Cybathlon in May 2020.


Curious about the entire presentation of the design? Click here (https://youtu.be/UC1nYerdwLY) to see the design presentation of April 24th.

 
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SIDEWAYS MOTION

MARCH IV is the first MARCH exoskeleton where lateral movement of the hip is possible. The addition of this joint provides extra freedom of movement. In the short term, the hip will help in the event of an obstacle of the Cybathlon in which the exoskeleton has to walk on an inclined slope.

In the long run, the hip could help to make walking with the exoskeleton more stable and natural.

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BALANCE

In the MARCH IV, the sole of the foot has been extended to three different layers: a layer for comfort, a layer that forms the supporting base and a layer with pressure sensors. The layer with pressure sensors measures how the exoskeleton stands on the ground with the user. In this way, data is collected that can be used to conduct research into the balance of the exoskeleton. Another place where sensors come back that can contribute to the future balance of the exoskeleton is the upper body of the user. Here, sensors are placed that measure the position of the upper body. This information can ultimately help to better determine the movement of the user with the exoskeleton.

In the longer term, this can contribute to an important wish of users: an exoskeleton in which the crutches are no longer needed.

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COMPACT FIT

Current exoskeletons are still regularly labeled as large. One of the long term goals is to make the exoskeleton smaller and lighter. This will contribute to the ease of use. For example, a smaller and lighter exoskeleton can be more easily carried around in the car.

In the MARCH IV, different ways have been worked on achieving this goal. For example, the thighs have almost double the amount of electronics compared to the previous model. The thigh has become a compact package. This makes the electronics an important limitation for reducing the size of the exoskeleton. In order to be able to take steps, there are two solutions that we have used with the MARCH IV. The first is to replace the functionality of the electronics with software. The second solution is to make the electronics smaller and more efficient. A good example of this is the Power Distribution Board (PDB). The PDB is the electronics that distributes all the energy over the entire exoskeleton. By using smaller components and using both sides of the board, the surface area of the PDB is reduced by 20% and it is also a lot flatter compared to its predecessor.

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MODULAR

Previously, the metal bones of the MARCH exoskeleton had different functions requiring a complex shape. The complex metal shape was relatively difficult to produce. The MARCH IV therefore looked at how the bones could be made simpler, the answer was modularity. In the MARCH IV, the bone is divided into several pieces. For example, there is a metal core that absorbs the forces through the exoskeleton and there is a plastic part around it that carries the electronics. The modular design also makes it easier for the fifth MARCH team to implement improvements.

In the long term, modularity contributes to an exoskeleton in which parts can easily be replaced, so that the exoskeleton can be personalized. This will make the exoskeleton accessible to a larger group of users, from large to small.

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FUTUREPROOF SOFTWARE

Another place where modularity can be seen is the new software of the exoskeleton. Modularity has been applied here in order to be able to continue to use the current software in the coming years. Software is often completely discarded when it is no longer understandable or usable. By applying modularity to the software, you can turn one complex system into divided building blocks. This allows teams to easily add, replace or dispose of software blocks in the coming years. It is therefore no longer necessary to start all over again if an important change needs to be made.

Combine modularity with clear documentation and good version management and you have a system that will save future teams a lot of time.

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USER COMFORT

As in previous years, we put the user's controls back on the handle of the stool. The big advantage of this is that the user does not have to let go of the crutches, which are essential for the balance, when operating the exoskeleton. This year again steps have been taken in the user-friendliness of the control system. For example, the menu for the user is easier to navigate due to simple images and an improved structure.

Other important places that improve the ease of use for the user are the contact points with the exoskeleton. The contact points, or fixtures, in the MARCH IV are perfectly tailored for the pilot. This reduces the risk of pressure scuffs, which is something people with paraplegia are sensitive to. The shoe has been given a completely new design in which the entire insole has been replaced with functional layers. The hip fixture is shaped like a corset around the user, which improves the stability.

 

VIDEO DESIGN MARCH IV

 

 

 
 
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