Created September 4, 2024 © CC BY

Proximity Sensed Haptic System for Visually Impaired

A wearable solution for visually impaired people which will help them avoid obstacles & navigate indoor better by receiving haptic feedback

IntermediateFull instructions provided4 hours17

Proximity Sensed Haptic System for Visually Impaired

Story

Introduction

The Idea

We spend a big part of our lives indoor, whether it is home or office or school. Indoor places are usually full of stuffs - furniture, electrical appliances, everyday objects and much more. A visually impaired person may stumble or bump into things while trying to navigate indoor environments. This is a problem that can cause injuries and suffering.

Suggested Solution

I propose following solution to address this problem: "" Proximity Sensed Haptic Feedback Shoes for Visually Impaired Persons "" This solution will have infrared proximity sensors on shoes to detect objects, walls indoor. As the visually impaired person tries to navigate indoor, the sensor will sense obstacles, there will be vibration motors that will vibrate and inform the user. The closer the obstacle is the frequent will be the vibrating pulses to inform user. This way, a visually impaired person can navigate indoor without seeing.

FEEDBACK FROM CONTEST MASTERS:
"The solution you propose is very simple in concept and seems very practical with a real potential to work and provide benefit to the user. Maybe you could say more about the design and the proposed functionality. What is the detection angle of the IR sensor, just a forward arc, some side detection, or all around? Is there any difference in the coverage between the two shoes (forward and left for the left shoe and forward and right for the right shoe)? Also, you will need to consider when someone is taking a step forward, at the last stage when the foot is being lifted to come forward, the foot itself is briefly pointed downwards, so this would give an unwanted detection. You may need to detect this and suppress the triggering of the vibration."

Feedback Integration :

As pointed out in the feedback by the contest master, the shoes proposed in this project may cause unwanted triggering when foot is pointing downwards

So, I have changed my solutions to be:-

"Proximity Sensed Haptic System for Visually Impaired" which is a wearable knee-pad that can act as a radar system for indoor navigation.

Features of the System

Detect Obstacles in Indoor Environment up to 1 meter Distance
Alerts User with Haptic Feedback System
More frequent Vibration Indicates objects are closer
Very low cost design
Can work for bright or dark surfaces

Limitations

Can detect only for a narrow angle
Inconvenience of recharging/replacing battery
May miss objects with hollow structure

While the limitations can easily be eliminated with much more expensive sensors like LiDAR, this project intends to build an affordable tech, not something that cost thousands of dollars !

Feedback Integration that was skipped

The contest masters asked to integrate piezoelectric generator into this project. However, I find it will make the solution more expensive and unnecessarily complicated. The goal of this project is to demo a very affordable solution that can be easily manufactured with commonly available parts which costs little. That's why I didn't implemented this feedback into my solution.

Demonstration Video

Following video demonstrates obstacle detection and increase of frequency of vibration (indicated by fast blinking blue light):

Hardware Build

The hardware consists of following parts :

Infrared Proximity Sensor GP2Y0A21YK / GP2Y0A02YK0F
Atmeag32u Microcontroller
3 Vibration Motors
8.4 Lipo Battery Pack
UNL2803 Driver IC
A Knee Strap Belt (reused from a knee joint heating strap)
Black Face Mask 3 pcs
Conductive Thread (stainless steel thread)

The following image shows the knee strap belt, 8.4 V LiPo battery pack and the finished haptic obstacle sensing prototype.

Putting things together !

I have sewed 3 vibration motors with and put them in parallel connection with conductive stainless steel thread to create the haptic pad.

Homemade Vibration Pat

The substrate material is just 3 face masks 😆. This vibration pad is flexible so it can take the shape of knee when strapped on knee belt.

On the Next image, the vibration pad, the controller hardware and the power pack battery all are attached together both physically and electrically on the knee strap.

Please check schematic at the end of this page to see details for electrical connections.

Next, lets talk about the power source

Here is a closer look at the 8.4 battery pack. It originally came with the thermal knee strap but it's just basically 2x 18650 cylinder LiPo in series with charging/protection circuits.

How Does it Work ?

The working principle of this obstacle detection is quite simple actually.

For this project the infrared proximity sensor GP2Y0A21YK was used.

This Infrared proximity sensor which is made by Sharp has an analog output that varies from 3.1V at 10cm to 0.4V at 80cm. The sensor has a JST Connector. It can be operated with a DC voltage between 4.5 V to 5.5 V

Infrared Proximity Sensor from Sharp GP2Y0A21YK

The proximity sensor sends out infrared beam which reflects back from objects.It emits a pulse of light with a wavelength range of 850nm ± 70nm, which then reflects off an object or doesn't return at all. The angle at which the light returns depends on the distance of the object.
By measuring this angle, the system can calculate the distance to the reflecting object. This angle measurement is called Triangulation. Triangulation operates by detecting the angle of the reflected beam. Once this angle is known, the distance can be calculated.
A precision lens directs the reflected light onto a linear CCD array, which is housed within the device. This CCD array, using the triangulation angle, determines the angle of the reflected light. The output of the IR proximity sensor is an analog voltage which varies depending on the distance of the detected object.
AtmegaU32 mcu's ADC measures this analog voltage and calculates the distance of any detected obstacle. Then depending on the distance of the object detected, PWM signals are generated to drive the vibration motors.The closer the obstacle/objects the stronger is the vibration from the motor.

This vibration gives visually impaired person the haptic feedback they need to make a guess how close they are to any obstacle in front of them.

Conclusion

In conclusion, this project offer several advantages, such as simplicity, some degree of reliability and cost-effectiveness, making it suitable for short to medium-range measurements for obstacle detection. However, they also have limitations, including sensitivity to environmental factors like ambient light and surface reflectivity, which can affect accuracy. Additionally, their narrow angle of detection can restrict their effectiveness in broader measurement contexts. Performance may also decline over longer distances or in challenging conditions.

This project offers a very low cost solution for visually impaired persons to help them navigate indoor environments. Utilizing LiDAR can help make this project more reliable and give users deeper insights into detection of obstacles but the cost will ramp up 10 folds !

Code

main.c

int i;
int val_in_cm = 100;
int sensor_pin = A2; // Analog Input for IR proximity sensor
int blue_led = 13;  // viusal indicator of vibration
int vibe_drive = 10; // UNL2803 chip drive pin to run vibration motors


void setup() 
{
 pinMode(blue_led,OUTPUT);
 pinMode(vibe_drive,OUTPUT);
}

void loop() 
{
  
  // read analog val from IR proximity sensor output
  
    i=analogRead(sensor_pin);
  
  // convert in cm distance of obstacle
    val_in_cm=(6762/(i-9))-4;
  
    
    if (val_in_cm <= 10)
    val_in_cm = 10;
    
    if (val_in_cm >= 99)
    val_in_cm = 100;
  
  // change haptic sensation based on obstacle distance
  // closer object will have stronger vibration
  
    int pwm_scaling = val_in_cm*2.55;
    analogWrite (blue_led, (255-pwm_scaling));
    analogWrite (vibe_drive, (255-pwm_scaling));
    delay (val_in_cm*3);
    analogWrite (blue_led, 0);
    analogWrite (vibe_drive, 0);
    delay (val_in_cm*3);
  
}

Credits

Sunny

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Proximity Sensed Haptic System for Visually Impaired

Story

Introduction

Feedback Integration :

Demonstration Video

Hardware Build

How Does it Work ?

Conclusion

Schematics

Schematic

Code

main.c

Credits

Sunny

Comments

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Proximity Sensed Haptic System for Visually Impaired

Proximity Sensed Haptic System for Visually Impaired

Story

Introduction

Feedback Integration :

Demonstration Video

Hardware Build

How Does it Work ?

Conclusion

Schematics

Schematic

Code

main.c

Credits

Sunny

Comments