Design and Fabrication of a wearable exoskeleton for power augmentation of arm
Disability is a human condition characterized by reduced or non functioning of body parts of human being . Almost every person , in his life span at some time will face temporarily or permanently impairment.Those who will make it to old age ,will experience increasing difficulties in performing vari
2025-06-28 16:31:29 - Adil Khan
Design and Fabrication of a wearable exoskeleton for power augmentation of arm
Project Area of Specialization RoboticsProject SummaryDisability is a human condition characterized by reduced or non functioning of body parts of human being . Almost every person , in his life span at some time will face temporarily or permanently impairment.Those who will make it to old age ,will experience increasing difficulties in performing various body functions specially those involving movements. About 15 percent of the world’s population lives with some form of disability, of whom 2-4 percent experience significant difficulties in functioning .This project is about building a power augmenting device for arm which will multiply the
power of hand and forearm for doing multiple tasks that require greater lifting powers which under normal circumstances , either an individual can apply for short time , or is unable to apply (disability). The driving signals for this partial exoskeleton will be the ones resulting from neural activity. These signals will be taken from muscles using
any suitable electromyographic device for the individuals who have reduced or normal motor functioning and from an indigenously developed fNIRS (functional nearinfrared
spectroscopy) headset for quadriplegic individuals. Building the fNIRS headset is an optional part of this project but training this exoskeleton on fNIRS offline dataset is one
of our objective.
- Design and Fabrication of a wearable exoskeleton for upper limb.
- Controlling the exoskeleton through real-time EMG data by using a pre-built EMG sensor.
- Modelling of both mechanical structure and electrical circuitry: This part includes designing and analysis of devices and its various parts on paper. Rough drafts were made and static analysis was performed to have an initial idea of where and how much forces will be acting on the device. The finalized design was then drawn on Solid works (CAD software). The model was then animated to see, whether it is giving required DOF.
- Acquiring signals:
It involves acquisition of input signals. We will use MayoArm Band , an EMG 13 Introduction signal acquiring device commonly used these days for integrating with prototypes involving functioning dependent on muscle signals (indirect BCI) . This will be a real-time process and will result in a delayed action due to processing limitations. We also plan to get control commands from an indigenously developed fNIRS headset . However it will be limited to only certain movements. - Preprocessing (includes various filtering and noise reduction techniques): Noise removal techniques both in terms of hardware (for indigenously developed fNIRS headset) and software , like Kalman filter will be used to make sure no unwanted signals gets into the system.
- Training of our algorithm with real-time data:
Machine learning algortihms like neural networks are generally used for these type of applications. However classifiers like LDA and SVM can also be used for the purpose. This stage refines decision of MC after every training session. The algorithm is trained by giving it values by moving the exoskeleton externally and assigning the values obtained by encoders to a specific posture. The more training attempts are done, the more accurate the control of exoskeleton. Training of EMG signals on neural networks is a an effective technique. 
- Testing actuation by generating control commands: A mathematical model of angular displacement of all moving joints of exoskeleton will be formed. This will give us some equations having angular displacement of one joint as a function of other. These defines the overall motion of exoskeleton provided certain change of angle in any one joint. These equations are known as forward kinematics. When we specifies the end point of manipulator (which in our case is hand tips of exoskeleton)and find the projections of each previous joint, the process results in equation which are basically the inverses of forward kinematic equations. These are know as Inverse Kinematics.
- The project will benefit alot of people who have a weak or disabled arm, subject to the availablility of EMG signals.
- Any healthy person can use the exoskeleton to augment his power to suit his work requirements, like in heavy industries.
- The exoskeleton does not lsome specific types of load to be detrimental to the person wearing the exoskeleton.
- Easier gripping of objects.
- For a disabled person, not being able to do his/her daily chores, which requires negligible effort, results in negative psychological effects which sometime leads to anxiety and depression. Also in our daily life we came across instances in which we have to lift heavy loads for a significant time period which results in aches. This greatly declines our ability to perform other tasks after we are done with
activity which requires such lifting. This problem is not only confined to disables and
normal peoples, but also to individuals working in environment which requires direct manned and precise control like fixing space craft in outer space. These all problems simply get eliminated by using this exoskeleton.
Block Diagram of the system:
Flow chart of the system:
Initial CAD model of the exoskeleton (idea):
The CAD model was prepared in SolidWorks. The material we considered for the analysis is aluminum alloy. This exoskeleton is capable of exhibiting 3 DOF. Different views are shown below to give an overview of how our device will look like:
This frame is basically a combination of 6 basic parts. More parts will be used but they will be just a mere extension of either of these parts. These parts gives the basic shape to our exoskeleton and will provide a rigid surface to mount bearings and actuators on it .These parts are designed , keeping in view the comfort ability of the user and aiming to make this device wearable.
Scope of the project:
- Real-time functioning of exoskeleton using EMG.
- The exoskeleton will have an augmenting factor in the range of 1.3 - 1.5 approximately.
- Retaining of position by mechanical locks, rather than electric brakes.
- Expected approximate weight is 6 kg.
- Exoskeleton will be capable of lifting weight from 120 degrees elbow angle up to 60 degrees (acute angle) approximately.
| Item Name | Type | No. of Units | Per Unit Cost (in Rs) | Total (in Rs) |
|---|---|---|---|---|
| Total in (Rs) | 80000 | |||
| EMG band | Equipment | 1 | 30000 | 30000 |
| Li-ion battery | Miscellaneous | 1 | 10000 | 10000 |
| Carbon fibre assembly | Equipment | 1 | 30000 | 30000 |
| Multiple driving and connectivity modules | Equipment | 1 | 10000 | 10000 |