Manual Wheelchair Obstacle Detection System in Reverse Motion

Disability is the result of a complex relationship between a person’s health condition and personal factors, and external factors representing the circumstances in which that person lives, which may have positive or negative effects.

On the other hand, motor disability defines as the alteration of the motor apparatus that hinders or makes impossible the development of capacities that allow to participate in activities of daily life, such as standing, walking, move, take and manipulate objects with hands, talk, make gestures, among other actions that require movement and control of body posture.

This is why people with disabilities require technical aids that allow or facilitate the performance of tasks. One of the technical aids most used by people with motor disabilities is the wheelchair, whose function is the mobility of the user.

However, the problem of lack of rear visibility and the inability to see obstacles in wheelchairs is multifaceted and can have serious consequences for the safety and quality of life of people who depend on these mobility devices, there are several risks of accidents, difficulties in congested spaces, architectural barriers and psychological and emotional challenges.

For this reason, it was decided to create a system to detect obstacles when the wheelchair user moves in reverse direction, with the aim of improving the safety of the individual when moving.

• Accelerometer DXL345
• Ultrasonic sensor HC-SR04
• Buzzer
• Arduino Nano
• DuPont cables

The electrical diagram was made to verify the connections of the ultrasonic sensor, the accelerometer and the buzzer with the Arduino NANO module.

The HC-SR04 ultrasonic sensor was connected to the Arduino:

• VCC of HC-SR04 to 5V of breadboard
• GND of HC-SR04 to GND of breadboard
• Trig to digital pin 3 of the Arduino
• Echo to digital pin 4 of the Arduino

The ADXL345 accelerometer sensor was connected to the Arduino:

• VCC of the ADXL345 to 3.3V of the Arduino
• GND of ADXL345 to GND of Arduino
• SDA to A4 (SDA pin) of the Arduino
• SCL to A5 (SCL pin) of the Arduino

The buzzer was connected to the Arduino:

• A buzzer terminal was connected to digital pin 8
• The other terminal of the buzzer was connected to GND of the Arduino

The circuit was assembled on a protoboard, with each component connected accurately to ensure optimal performance. 

This circuit featured a buzzer that acted as an auditory alarm when the ultrasonic sensor detected an object at the same time as the accelerometer detected that the wheelchair was in reverse.

The circuit was programmed so that the ultrasonic sensor detects objects from 50 cm away and turns on an auditory alarm, exclusively when the wheelchair user advances in reverse. This function was done using the accelerometer, which was instructed to measure acceleration on the negative Y axis.

In addition, a function was added so that when it detects positive Y-axis acceleration, i.e., when the person is moving forward, the sensor does not detect objects or turn on the alarm.

Another function was added to ensure that the detection of objects is effective in the position in which the circuit was placed in the chair, which is flat on a horizontal axis, eliminating inclination factors.

This step includes the file containing the Obstacle detection system code.

The proximity sensor was strategically placed on the rear seatback of a wheelchair, where its ability to detect obstacles was maximized. Adjustments were made to ensure that the sensor was positioned optimally, allowing for sensitive and accurate detection of any nearby object.

Tests of the system were performed to verify its effectiveness, which were successful. The system was able to detect the objects when the wheelchair was moving in reverse, at which point the audible alarm turned on. At the end if the wheelchair is stationary, the sensor will not activate and will not send an alert that there is an object behind the wheelchair.

A video was attached showing the system in operation.

Finally, a casing was designed to protect the circuit from external environmental agents such as rain, dust, etc.

A box was designed in Solidworks with the size of the breadboard and a 5V battery. It was later printed with PLA material on a 3D printer.

The files for the box and lid design are attached below.