I Tilt and Go

This project focused on developing an independent mobility device for children with Cerebral Palsy (CP). It’s a condition caused by damage to the motor control centres of the brain – the regions which control body movements. Most children who are affected with CP lack independent mobility and are restricted to wheelchairs.

My work under the guidance of Dr. Sujatha Srinivasan at the R2D2 (Rehabilitation Research and Device Development) lab, Department of Mechanical Engineering, IIT Madras, was to design a wheelchair that could be controlled by children affected with CP by using gross movements of their body. We call it the I Tilt and Go, or ITaG, wheelchair.

The extent of mobility in children with CP varies widely: some can only move their head, while others can move only their left hand or right hand. The existing powered wheelchairs are not ideal, because they have to be controlled with a joystick, which requires fine motor skills that these children lack. Hence, a new wheelchair control mechanism had to be designed.

We knew that children with CP have the ability to move their body as a whole and that they can improve their control of this motion over time, with practice. So we decided to use gross body motion as the input to control the wheelchair we were designing. When the user moves forwards or sideways, the wheelchair could be made to move in the corresponding direction.

Coming up with a new design wasn’t straightforward. The key features required in the design were that it should be practical, user friendly, affordable and flexible to each child’s needs. Initially, we worked on developing an existing mechanism (designed as a part of the B.Tech project of Prashant Poondla), which used a seat that could rotate about two directions (universal joint) based on the motion of the user’s body. When the user moved forward/sideways, the seat rotated in the forward/sideways direction. The rotation of the seat was measured by angle sensors and the wheelchair controlled accordingly.

This mechanism was developed and tested with a healthy seven-year-old child. However, the child found it difficult to control the wheelchair because of the moving seat. This difficulty was expected only to be amplified for children with Cerebral Palsy. So, a new mechanism had to be designed which could provide a rigid seat.

One day, while guiding some juniors with their Centre for Innovation (CFI) project, I hit upon a new design. Their project used load cells to find the weight of water cans; moving the water cans on the platform caused changes in the load cell reading. I realized that the same concept could be used to detect gross body movements of the user. The effect caused by the shift of the water can is the same as that of the user moving their body; that is, a shift of the centre of gravity. This effect could be detected by placing a few load cells beneath the seat.

After performing basic calculations, the system seemed feasible. The rest was a matter of investing time and making the idea work in practice. The major challenge here was the scale of the project, which had to be completed in the required amount of time. The wheelchair had to be designed and manufactured, both mechanically and electronically.

Our design uses force sensors placed beneath the seat to detect a shift in the centre of gravity of the user. This method has several advantages which makes it ideal for children with CP. For one, the load cells are inexpensive. These sensors are placed beneath the seat and do not require any additional attachments to the user. The seat itself is virtually rigid and can detect, as input, a wide range of motion, such as that of the head, the trunk or the limbs. In fact, even fine movement, such as that of the head by as little as 30 degrees, can be detected. Moreover, the same system can be used for children weighing from 10 to 30 kgs, and can be calibrated according to the requirements of the child.

We were attempting to build a device which would be a product, so wanted to include the required mechanical features as well. The design, therefore, includes a mechanism for transporting and portability as shown below – where the backrest and armrest fold down, making the wheelchair compact, which can then be lifted by the user much like a briefcase; the arms and the foot rests are also removable.

Mechanism to make the wheelchair compact. Courtesy: Vivek Sarda
Mechanism to make the wheelchair compact. Courtesy: Vivek Sarda

Safety is a key consideration while designing any assistive device such as a wheelchair. Various safety measures incorporated include an ultrasonic distance sensor placed in front of the wheelchair for collision prevention and a wireless joystick which can be operated by a caregiver to override user instructions. Other electronic features included are data collection through an SD card to track the improvement in the body control of the user through repetitive usage of the wheelchair, and an LCD display providing feedback to the parents or the teacher. It displays the battery level, error messages in case problems arise, and sensor readings to understand the position of the children.

All this design, of course, had to work practically and not remain a model which would work only in the lab. So we field-tested the basic proof-of-concept model at Vidya Sagar, Chennai – an organization that works with children who have CP and other neurological disabilities
– for a period of three months with the help of ten children who were severely affected (GMFCS level: 4 and 5) with CP. It was also tested at the Spastics Society of Tamil Nadu (SPASTN) and Blossom Rehab Centre, both in Chennai.

Overall, we were delighted with the positive feedback from all these places. The children enjoyed the independent mobility and also improved their body control in the process. The design seems to provide a good solution for a wheelchair control mechanism for children with CP.

This was my dual degree project, and along the way, it took me to various exhibitions and competitions. I participated in the Inclusive Innovation Resfearch Expo 2013 in Pune and also in the 3rd International Conference on Biomedical Engineering and Assistive Technologies (BEATS) 2014 in Chandigarh, where the project won the best paper award. It won the Jed-i Project Challenge 2014, Bangalore, in the Electrical Division and the Sri Chinmay Deodhar Award 2014 for the Innovative Student Project, IC&SR projects, IIT-M. The design also has a patent pending.

Currently, I am at the R2D2 lab at IIT-M, which aims at developing affordable assistive technology like ITaG, the standing wheelchair, and various other orthotic and prosthetic devices. Although this mechanism was developed for people with CP, its flexibility makes it adaptable to people with other disabilities such as tetraplegia. We are working on developing a product version of the ITaG for adults and children, which would include an industrial design, apart from the design for manufacturing and assembly. The challenge here is to make the device affordable, as motorized wheelchairs are costly. Also, the device may possibly be beneficial for people with CP throughout the world, as well as for people with high levels of spinal cord injury. On developing the commercial version, we will look for ways to reach out to as many people as possible.

I would like to thank Dr. Sujatha Srinivasan for being an amazing guide. I would also like to thank Dr. Anil Prabhakar and Dr. Namita Jacob for bringing us this project and for helping in various aspects of the process of making this a product. I am grateful to Vidya Sagar, SPASTN and Blossom Rehab Centre for giving us the opportunity to field-test our prototype. I also thank CFI and the Central Workshop here at IIT Madras for providing the manufacturing facility. Finally, I want to thank all the tech junta of CFI and my hostel, Jamuna, for providing various inputs on the project