Child using robot-driven TPAD training method to improve crouch gait, symptom of cerebral palsy.
—Photo courtesy of Sunil Agrawal/Columbia Engineering

In the U.S., 3.6 out of 1000 school-aged children are diagnosed with cerebral palsy (CP). Their symptoms include abnormal gait patterns which results in joint degeneration over time. Slow walking speed, reduced range of motion of the joints, small step length, large body sway, and absence of a heel strike are other difficulties that children with CP experience. A subset of these children exhibit crouch gait which is characterized by excessive flexion of the hips, knees, or ankles.

A team led by Sunil Agrawal, professor of mechanical engineering and of rehabilitation and regenerative medicine at Columbia Engineering, has published a pilot study in Science Robotics that demonstrates a robotic training method that improves posture and walking in children with crouch gait by enhancing their muscle strength and coordination.

Crouch gait is caused by a combination of weak extensor muscles that do not produce adequate muscle forces to keep posture upright, coupled with tight flexor muscles that limit the joint range of motion. Among the extensor muscles, the soleus, a muscle that runs from just below the knee to the heel, plays an important role in preventing knee collapse during the middle of the stance phase when the foot is on the ground. Critical to standing and walking, the soleus muscle keeps the shank upright during the mid-stance phase of the gait to facilitate extension of the knee. It also provides propulsive forces on the body during the late stance phase of the gait cycle.

“One of the major reasons for crouch gait is weakness in soleus muscles,” says Agrawal, who is also a member of the Data Science Institute. “We hypothesized that walking with a downward pelvic pull would strengthen extensor muscles, especially the soleus, against the applied downward pull and would improve muscle coordination during walking. We took an approach opposite to conventional therapy with these children: instead of partial body weight suspension during treadmill walking, we trained participants to walk with a force augmentation.”

The research group knew that the soleus, the major weight-bearing muscle during single stance support, is activated more strongly among the lower leg muscles when more weight is added to the human body during gait. They reasoned that strengthening the soleus might help children with crouch gait to stand and walk more easily.

To test their hypothesis, the team used a robotic system — Tethered Pelvic Assist Device (TPAD) — invented in Agrawal’s Robotics and Rehabilitation (ROAR) Laboratory. The TPAD is a wearable, lightweight cable-driven robot that can be programmed to provide forces on the pelvis in a desired direction as a subject walks on a treadmill. The researchers worked with six children diagnosed with CP and exhibiting crouch gait for fifteen 16-minute training sessions over a duration of six weeks. While the children walked on treadmills, they wore the TPAD as a lightweight pelvic belt to which several wires were attached. The tension in each TPAD wire was controlled in real time by a motor placed on a stationary frame around the treadmill, based on real-time motion capture data from cameras. The researchers programmed the TPAD to apply an additional downward force through the center of the pelvis to intensively retrain the activity of the soleus muscles. They used a downward force equivalent to 10 percent of body weight, based on the results of healthy children carrying backpacks. This was the minimum weight needed to show notable changes in posture or gait during walking.

“TPAD is a unique device because it applies external forces on the human body during walking,” says Jiyeon Kang, PhD candidate and lead author of the paper. “The training with this device is distinctive because it does not add mass/inertia to the human body during walking.”

The team examined the children’s muscle strength and coordination using electromyography data from the first and last sessions of training and also monitored kinematics and ground reaction forces continuously throughout the training. They found that their training was effective; it both enhanced the children’s upright posture and improved their muscle coordination. In addition, their walking features, including step length, range of motion of the lower limb angles, toe clearance, and heel-to-toe pattern, improved.

“Currently, there is no well-established physical therapy or strengthening exercise for the treatment of crouch gait,” Agrawal notes.

Heakyung Kim, A. David Gurewitsch Professor of Rehabilitation and Regenerative Medicine and Professor of Pediatrics at the Columbia University Medical Center, who treats these patients, added “Feedback from the parents and children involved in this study was consistent. They reported improved posture, stronger legs, and faster walking speed, and our measurements bear that out. We think that our robotic TPAD training with downward pelvic pull could be a very promising intervention for these children.”

The researchers are planning more clinical trials, to test a larger group and changing more variables. They are also considering studying children with hemiplegic/quadriplegic CP.

Click here to view the research paper.

Image: MIT CSAIL

Singapore and MIT have been at the forefront of autonomous vehicle development. First, there were self-driving golf buggies. Then, an autonomous electric car. Now, leveraging similar technology, MIT and Singaporean researchers have developed and deployed a self-driving wheelchair at a hospital.

Spearheaded by Daniela Rus, the Andrew (1956) and Erna Viterbi Professor of Electrical Engineering and Computer Science and director of MIT’s Computer Science and Artificial Intelligence Laboratory, this autonomous wheelchair is an extension of the self-driving scooter that launched at MIT last year — and it is a testament to the success of the Singapore-MIT Alliance for Research and Technology, or SMART, a collaboration between researchers at MIT and in Singapore.

Rus, who is also the principal investigator of the SMART Future Urban Mobility research group, says this newest innovation can help nurses focus more on patient care as they can get relief from logistics work which includes searching for wheelchairs and wheeling patients in the complex hospital network.

“When we visited several retirement communities, we realized that the quality of life is dependent on mobility. We want to make it really easy for people to move around,” Rus says.

Image: Kenguru

Robocars are broadly going to be a huge boon for many people with disabilities, especially disabilities that make it difficult to drive or those that make it hard to get in and out of vehicles. Existing disability regulations and policies were written without robocars in mind, and there are probably some improvements that need to be made.

While I was at Google, I helped slightly with the project to show the first non-employee getting to use the car to run errands. The subject we selected was 95% blind, and of course he can’t drive, and even using transit is a burden. It was obvious to him immediately how life-changing the technology will be.

Some background on disabled transport

There are two rough policy approaches to making things more accessible. One requires that we make everything accessible. The other uses special accommodations for the disabled.

Making everything accessible is broadly preferred by advocates. Wheelchair ramps on all public buildngs etc. Doing less than this runs a risk of “separate but equal” which quickly becomes separate and inferior. It’s also hugely expensive, and while that cost is borne by people like building owners and society, there is not unlimited budget, and there are arguments that there may be more efficient ways to spend the resources that are available. There are also lots of very different disabilities, and you need very different methods to deal with impairments in sight, mobility, hearing, cognition and the rest.

Over 50 million people in the USA have some sort of disability, so this is no minor matter.

In transportation, there is a general goal to make public transit accessible. To supplement that, or where that is not done, there are the paratransit rules. Paratransit offers people who meet certain tests an alternate ride (usually in a door to door van) for themselves and a helper for no more than twice the cost of a regular bus ticket. That sounds great until you learn you also have to schedule it a day in advance, and have a one-hour pickup window (which the disabled hate) and it’s hugely expensive, with an average cost per ride of over $30, which cities hate. (In the worst towns, it is $60/ride.) In some cities it approaches half the transit budget. Some cities, looking at that huge cost, let some disabled customers just use taxis for short trips, which provide much better service and cost much less. (Though to avoid over-use they put limitations on this.)

There are Americans with Disabilities Act rules for taxis. Regular sedan taxis are not directly regulated though there can be no discrimination of disabled customers who are capable of riding in a sedan. Any new van of up to 8 seats has to been accessible, which often means things like wheelchair lifts. In addition, once a taxi fleet has accessible vans, it has to offer “equivalent service” levels. This might mean that if it has 200 sedans, it can’t buy just one van because there would be much longer wait times to get that van. To get around this, a lot of companies use a loophole and purchase only used vans. The law only covers the use of new vans. Companies like Uber and Lyft don’t own vehicles at all, and so are not governed in the same way by fleet requirements, though they do offer accessible vehicle services in some cities.

When Uber and similar companies move to offering robotaxi service with vehicles they own, these laws would apply to them. Unlike some companies, the used van loophole will also be difficult since most robotaxis will be custom built new.

New Types of Vehicles

Robotaxi service offers the promise of a vehicle on demand, and it offers the potential of a vehicle well fitted to the trip. Mostly I talk about things like the ability to use a small and inexpensive one person vehicle for solo urban trips (which are 80% of trips, so this is a big deal) but it also means sending an SUV when 3 people want to go skiing, or a pickup-truck for a work run, or a van designed for socializing when a group of people want to travel together.

It also offers the ability to create vehicles just for people with certain disabilities. One example I find quite interesting is the Kenguru — a small, single person vehicle which is hollow, and allows a user in a wheelchair to just roll in the back and steer it with hand controls. For wheelchair users with working arms, this is hugely superior to designs that require you to get out of your chair into a car seat, or which involve the time delays of using a wheelchair lift. Especially with nobody to assist. Roll-in, roll-out can match the convenience of the able-bodied. The current Kenguru is to be steered, but a self-driving vehicle like this could handle even those in power chairs, and offer a fold-down bench for an able-bodied companion.

Being computerized, these vehicles will also offer accessible user interfaces. Indeed, they may mostly rely on the user’s phone, which will already be customized to their needs.

Custom-designed to meet particular disabilities, these vehicles will both serve the disabled better and frankly be not that useful for others. As such, regimes that require adapting all vehicles to handle both types of customers may have the right spirit, but provide inferior service.

Another key benefit of robotaxi service for the disabled will be the low price. Reduced job prospects drive many with disabilities into poverty. Service that is naturally low in price will be enabling.

Equivalent service or Separate but Superior

Providing “equivalent” service is difficult with traditional taxis, particularly for smaller fleets. Robotaxis, which don’t mind waiting around because no human driver is waiting, make this easier to do. The service level of a robotaxi service is based on the density of currently unused vehicles in your area. Increase fleet size with the same demand, and service level goes up. As long as fleet size is not way overblown, so that vehicles still wear out by the mile rather than by the year, increasing fleet size is not nearly as expensive as it is for regular cars or human driven taxis.

This means you can, fairly readily, offer equivalent or even superior service at a pretty reasonable cost. As long as disabled-designed vehicles are made in decent quantities to keep their costs low, the cost should be close to the cost of regular vehicles. In the public interest, regular vehicle customers might subsidize the slightly higher cost of these lower volume vehicles.

With increased fleets, service levels would generally be superior to the regular fleets, but not always. The law generally allows this, but the disabled community will need to understand a few unequal things that probably will happen:

• Slightly more advanced notice of rides will often make it possible to provide service at lower cost. Regular vehicles will naturally be present on every block. Disabled vehicles might be present with less density during high use times, but the ability to reposition lets even slight advance notice do a lot.
• For those in groups, it may not be easy to carry a person in a wheelchair along with several non-wheelchair passengers. This might mean the wheelchair passenger goes in their own vehicle (with videoconference link.) This is not as good, but is much more cost effective than requiring every van to have a wheelchair lift.
• To increase service levels, it is likely competing companies would cooperate on serving the disabled, and pool fleets. Until the disabled become a profitable market rather than one done to meet goals of public good, companies will prefer to work together. As such if you call for an Uber, you might often get a Lyft or other small fleet car.
• Low cost disabled transport may mean that accessible public transit and paratransit slowly fade. Public transit which has its own tracks will continue to be accessible as it offers a speed advantage which may not be met on the roads, but otherwise it may be much cheaper to offer private robotaxis than to make all transit accessible. This would mean a group of people might not be able to ride transit together if it’s not accessible.
• Small electric vehicles may be allowed to enter buildings, dropping passengers right at elevator lobbies or other destinations.

The biggest trade-off will be the loss of social group experiences. There certainly will be buses and vans with lifts which allow groups of mixed-ability passengers to travel together, but it is unlikely these would be so common as to offer the same service level as ordinary vans. With advance notice of just 10 minutes, they could probably be available.

If you liked this post on robocars, you’ll also enjoy these articles:

• What if the city ran Waze and you had to obey it? Could this cure congestion?
• Google car is now Waymo
• Comma.ai cancels comma-one add-on box after threats from NHTSA
• Robocar news: Comma One goes open source, creating simulations for robocars in New Zealand earthquakes

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