Created November 29, 2023

AquaGuide

Assistive swimming technology for the blind

Things used in this project

Hardware components

Blues Swan

Ultrasonic Sensor - HC-SR04 (Generic)

Used instead of Waterproof Ultrasonic Sensors

Jumper wires (generic)

Buzzer

Used instead of the waterproof bone conduction bluetooth headphones

Breadboard (generic)

SparkFun Breadboard Power Supply 5V/3.3V

I used a USB cable to supply power from my Laptop port

Software apps and online services

Arduino IDE

Story

Swimming has been a sport that has been undertaken by many individuals of all ages. Moreover, it is an easily adaptive sport for athletes who are blind or partially sighted. This has been proven so ever since the inception of para-swimming at the first Paralympic Games in Rome in 1960. But the advent of para-swimming never came without its fair share of challenges; with the two main challenges being improper lane navigation and poor flip-turn timing.

The Swim Lane Navigation System

The swim lane navigation system uses some the basic principles in Linear Algebra, Geometry & Trigonometry.

Illustration I

As shown in the illustration above, two ultrasonic sensors are placed in close promixity with each other with the distance between their midpoints known- Distance M.

The left and right ultrasonic sensors are programmed to capture the distance of the swimmer as Distance L & Distance R respectively.

Using the Hero's Formula,

Hero's Formula

The area of the triangle formed can be calculated whereby;

s - Half perimeter
a - Distance M
b - Distance R
c - Distance L

But since the area of a triangle is given by the formula below,

Area of Triangle

we use that formula to calculate the angle L in the illustration below which is represented as the gamma symbol in the formula

Illustration II

With Angle L now known, we use it to calculate the Angle M in the illustration below

Illustration III

We do so by using the Cosine Rule,

Cosine Rule

whereby;

a - Half Distance M
b - Distance R
c - Midline
gamma - Angle L

We then use the Sine Rule to calculate the Angle M,

Sine Rule

whereby;

B - Angle M
b - Distance R
C - Angle L
c - Midline

Once we have calculated our Angle M, we subtract 90 degrees from it to give us our Deviation Angle as shown in the illustration below.

Illustration IV

Thus we can calculate the deviation of the swimmer.

Illustration V

Building Instructions

Connect the Ultrasonic Sensors to the Swan as instructed below,

VCCs to 5V Power Supply
GNDs to GND of Power Supply and on Swan
TRIGs to Pin 13 on Swan
ECHO of Left Ultrasonic Sensor to A1 on Swan
ECHO of Right Ultrasonic Sensor to A3 on Swan

Connect the Buzzers to the Swan as instructed below,

- VE Pins to GND on Swan
+ VE PIn of Left Buzzer to Pin 10 on Swan
+ VE Pin of Right Buzzer to Pin 11 on Swan

After all connections are made it should look as shown below.

Setup

How it Works

The above setup is just a model of what the actual prototype was meant to be. The actual prototype was to consist of;

Wireless Waterproof Bone Conduction Headphones which would be a wearble and would be connected to the swan via an external Bluetooth module
Waterproof Ultrasonic sensors placed on the edge of the pool

Since I didnt have Wireless Waterproof Bone Conduction Headphones, I opted to use Buzzers. Also, I used the Generic Ultrasonic Sensors instead of the Waterproof Ultrasonic Sensors due to financial constraints. Nonetheless, I am very sure that the model I prepared above can sufficiently explain what I am trying to acheive.

When the swimmer has deviated to far to the left the left buzzer will ring. The same applies in vice versa. This is the working principle of the swim lane navigation system. When the swimmer is close enough to the ultrasonic sensors both Buzzers will ring. So in some way it also helps the swimmer to know when to make a flip turn.

But what I had in mind for the actual prototype is that when the swimmer has deviated to far to the left the left earpiece of the bone conduction headphones would ring and vice versa; and when the swimmer is almost at the edge, both earpieces of the hedphones would ring.

I believe this to be a simple and sufficient way to acheive both proper swim lane navigation and good flip turn timing.

The following video show how the setup above in action!

https://drive.google.com/file/d/1JarQm1GeeKzHbrqHrLQta7P6KtoeBqI6/view?usp=sharing

Please ignore the background noises :)

AquaGuide

int trig = 13;
int echol = A1;
int echor = A3;
int dtime = 10;
float distr=5, distl=5;
int timeout=10;

int lBuzzer = 10, rBuzzer = 11;

void setup() {
  pinMode(trig, OUTPUT);
  pinMode(echol, INPUT);
  pinMode(echor, INPUT);
  pinMode(trig, OUTPUT);

  pinMode(lBuzzer, OUTPUT);
  pinMode(rBuzzer, OUTPUT);

  Serial.begin(115200);
}

void loop(){ 
  delay(1000);
  pulse();
  float deviation[2];
  deviation[0] = get_deviation(0);
  deviation[1] = get_deviation(1);


  if(deviation[1] < 10){
    digitalWrite(lBuzzer, HIGH);
    digitalWrite(rBuzzer, HIGH);
  }else{
    digitalWrite(lBuzzer, LOW);
    digitalWrite(rBuzzer, LOW);
  }

  if(deviation[1] < 0 && abs(deviation[0]) > 5){
    digitalWrite(lBuzzer, HIGH);
    digitalWrite(rBuzzer, LOW);
  }else if(deviation[1] > 0 && abs(deviation[0]) > 5){
    digitalWrite(rBuzzer, HIGH);
    digitalWrite(lBuzzer, LOW);
  }

Serial.print("distl: "); Serial.print(distl);
Serial.print("\tdistr: "); Serial.println(distr);
Serial.print("deviation_degrees:"); Serial.print(deviation[1]);
Serial.print("\tdistance: "); Serial.println(deviation[0]);

 
}

void pulse(){
  timeout = 100000;  
  digitalWrite(trig, LOW);
  delay(dtime);
  digitalWrite(trig, HIGH);
  delay(dtime);
  digitalWrite(trig, LOW);
  distl = (pulseIn(echol, HIGH, timeout))*15/900.0;

  digitalWrite(trig, HIGH);
  delay(dtime);
  digitalWrite(trig, LOW);
  // convert echo time to centimetres
  distr = (pulseIn(echor, HIGH, timeout))*15/900.0;

}

float get_deviation(int i){
  float sep_distance = 8.5;
  float half_per = (sep_distance+distl+distr)*0.5;
  float area = sqrt(half_per*(half_per-distl)(half_per-distr)(half_per-sep_distance));//8.5 is the separation distance btwn the HC-SRO4s
  float theta_p = asin(area/(distl*sep_distance/2.0));
  float midline = sqrt(pow(distl,2)+pow((sep_distance/2.0),2)-distl*sep_distance*cos(theta_p));
  // convert radians to degrees
  float theta = 90-((asin((distl*sin(theta_p))/midline)))*180*7/22.0;


  if (i == 1){
    if (distl<distr){
      return -theta;
    }
    else{
      return theta;
    }
  }
  if (i == 0){
    return midline;
  }
}

Credits

Daniel Wakayamba

1 project • 1 follower

Contact

Thanks to Trevor Muhavi Mwanzi.

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AquaGuide

AquaGuide

Things used in this project

Hardware components

Software apps and online services

Story

Code

AquaGuide

Credits

Daniel Wakayamba

Comments