Design And Prototyping of Passive Exoskeleton For Lower Limb To Assist Walking

Millions of people worldwide suffer from stroke, spinal cord injuries, and neurological disorders. Currently in Pakistan there are over 1 Million people which are affected by strokes. In order to cover this gap, our group has decided to develop passive exoskel

Project Title

Design And Prototyping of Passive Exoskeleton For Lower Limb To Assist Walking

Project Area of Specialization

Wearables and Implantable

Project Summary

Millions of people worldwide suffer from stroke, spinal cord injuries, and neurological disorders. Currently in Pakistan there are over 1 Million people which are affected by strokes. In order to cover this gap, our group has decided to develop passive exoskeleton for people suffering from lower limb disorder. Our group opted for passive exoskeleton as there are already hybrid and electronic exoskeletons in the market. A constraint of power exoskeletons is that the patients are not able to control leg movement in all directions, while in case of passive exoskeleton its movement is totally under the control of user. The other concerning problem with these types of exoskeleton is cost. As the parts in these exoskeletons are usually imported so it increases the overall price of the product. On the other hand, passive exoskeletons consist of mechanical parts. By making a mechanism of different components assistance is provided to the user. The background area in the field of exoskeleton shows that passive exoskeletons help a lot in reduce the cost of maintaining the normal gait cycle. Passive exoskeletons are normally made with springs, and the springs are utilized for two purposes. One is to store energy and the other is to return energy during each gait cycle. In order to compensate the gravity, we have used spring mechanism with mating gears to overcome the influence of gravity. This allow us to make our design compact, lighter in weight and cost efficient. The main reason for choosing a passive skeleton is that it will not only allow the user to control movement of gait cycle but also allow us to make a compact design for the user. Thus, less space is required in the design of passive exoskeleton.

Project Objectives

In the design of exoskeleton, we have used spring mechanism that will help a lot in gravity compensation. A couple of mating gears is utilized to convert tension force into settling torques to adjust forces at the knee and hip joints to beat the impact of gravity. The main goals of our project are:

• To provide walking assistance to people suffer from lower limb disorder.
• To manage the leg movement according to normal gait cycle.
• To achieve torque reduction at hip and knee joint.
• To fabricate a compact, economical and lighter in weight exoskeleton.

Project Implementation Method

The passive exoskeleton is mainly comprised of mechanical components. In these types of exoskeletons; springs, gears, revolute joints, artificial tendons and other different un powered modules are used to equip with user to insist him/her to walk effectively. The combination of these mechanical components are arranged in such a way that user can control the walking behavior according to their need. 

Passive designs attempt to improve the energy exchange between potential and kinetic energy of body segments and to reduce the energy consumed by muscles in producing
motion.Passive exoskeletons are more viable as don’t require any external energy source, and their movements are under the control of those wearing them. They commonly designed by using springs, the spring attachments replicates the stance and swing motion of the leg. They store and release the energy according to the movement of the lower body.

Benefits of the Project

Our group aim was to help these people by developing a user friendly passive exoskeleton which help these people to do their basic life activities. We thought to develop an exoskeleton to those people who have lower limb walking problem. Around 10 percent people around the world who are effected by spinal cord injury are unable to control their lower body which causes immobility. Due to immobility person become depended on others and it effects the mental health conditions of the person and its guardians. By providing them with an exoskeleton it will help that person to perform the normal life activities. It wouldn’t perform exactly like the human organs but will help out to develop the mobility and in dependency on others.

Technical Details of Final Deliverable

The prototype product can be compromise of following major parts:

     1. Mating Gear System

This is an internal revolute spur gear system. It is mainly used to replicate the joint motion at Hip and Knee joint. The Hip joint gear is attached with the first portion of the base plate at the thigh and similarly the Knee joint gear at the shank portion of the exoskeleton. As the body will perform the walking movement the gears mechanism at these two joints will get active and will help out to make adjustment of the spring attached to it.

     2.Tension Springs

There are two tension springs in this exoskeleton. The first one is at the thigh and the other one is at the shank. These tension springs are usually used to absorb and release the energy as the leg movement performs a gait cycle. The stiffness and the displacement of these springs is calculated in such a manner that it assists in gravity compensation of the body.

     3. Connecting Rods

The connecting rods are used between two parts of the mechanism. A two to three connecting rods are used to join base plate of thigh and shank of the exoskeleton system. As the exoskeleton is attached with leg so to make a firm connection of it with leg so that there is synchronization of the exoskeleton and human leg.

     4. Lead Screws

The lead screw is used to adjust the length of tension spring. As the exoskeleton could be used by different types of people having a relative mass so to make this exoskeleton universal with an average human height but of different weight, the lead screw mechanism is used.   

Final Deliverable of the Project

Hardware System

Core Industry

Health

Other Industries

Medical

Core Technology

Wearables and Implantables

Other Technologies

3D/4D Printing

Sustainable Development Goals

Good Health and Well-Being for People, Affordable and Clean Energy

Required Resources

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