Embedded System Project on Foot Pronation Detection

In general, while walking or running we can observe the inward roll of the foot, which is called as pronation or eversion and it is measured in terms of the degree of inward roll. But, we can look at pronation even in other terms like when foot pushes off at the end of each step or at the end of the gait cycle. The pattern in which animals or human beings move their limbs during many manifestations such as running or walking or swimming etc. is called as gait. The pronation has to be measured to avoid the underpronation and overpronation, as these may lead to foot, knee, ankle and hip injuries. But, how to measure pronation?

How to Measure Pronation?

Even though there are different detection systems for foot pronation but, the embedded systems projects are the best choice for measuring foot pronation. The feet will absorb the shock of impacting the ground during normal motion as they roll inwards towards the center of the body and the weight will be distributed evenly across the foot. In fact, only a few are neutral footed while others are facing problems due to over and under pronations.

Pronation Detection with Embedded System Projects

Many electrical and electronics engineering projects students and professionals are researching on several embedded system projects for foot pronation detection. Let us consider one typical embedded system project in which mainly three functions are involved: data measurement, data processing and data storage or output.

Data Measurement

The data measurement function in a particular manner consists of capabilities of the inertial measurement unit. This embedded system project consists of an inertial measurement unit, accelerometers, gyroscopes, analog-to-digital converters and force sensitive resistors. Force sensitive resistors will decrease their resistance based on the force applied to the surface. Sensors are used at proper strategic locations for detecting the relative force distributions across the foot.

Data Processing

Data processing is used for conducting multiple functions like sensing the user steps, detecting the pronation of a user, angular movement of the foot and gives the output curves of the user. The network of sensors is embedded in this embedded system project for generating a basic model of the movement of the user.

Data Storage/Output

Primarily we use EEPROM for storing the output values as even after shutdown also the data can be retained. But due to certain limitations such as the requirement of AVR studio and the dataset is limited to 2000 values at a sampling rate of 100ms, EEPROM can be used to store limited data. So, we preferred to use an external storage for storing more data.

Embedded System Circuit Hardware for Foot Pronation Detection

The major blocks used for this project are as follows:

• ATMega644 Target Board
• Free scale MMA1260D Accelerometer
• Sensitronic/Interlink Force Sensitive Resistors
• LPR503AL Dual-Axis gyroscope
• SD Card Module
• 5V to 3.3V Voltage Converter

ATMega Target Board

ATMega644 chip is interfaced with the ATMega644 development board for interfacing with other hardware elements easily with the pins of ATMega644 chip being routed as ports of the board at its edge. Resistors and bypass capacitors are mounted on a customized PCB for protection.

Free Scale MMA1260D Accelerometer

Among the various variants of accelerometers, 1260D is chosen by preferring the resolution than bandwidth with a maximum acceleration of +/- 1.5g. The accelerometer will be approximately 1g during the normal standing position. The analog output of the accelerometer is converted using ADC rather than SPI interface. The clock noise can be removed using a simple RC-low pass filter and a decoupling capacitor is connected between the Vcc and ground.

Sensitronic/Interlink Force Sensitive Resistors

The change in resistance of the force sensing resistor will change with the change in force or pressure applied on that electrical resistor. It is also called as Force Sensitive Resistor.   These FSRs consists of a conductive polymer which has a property of changing the resistance based on the force or pressure applied on the polymer surface. In the circuit it is connected to Vcc in a voltage divider. Generally a 1Kohm resistor is used and in case of heel as less force is applied a 330ohm is preferred for this sensor (values are determined through trial and error method).

LPR503AL Dual-Axis Gyroscope

It is used for measuring the angular velocity with a full access of +/-300 degrees/s along the pitch and roll axis. The LPR503AL dual-axis gyroscope is used to measure the rate of angular movement of the shoe.

SD Card Module

SD card is used for storing the data and because of the problems raised due to soldering of SD card pins directly to the header pins. So, an external SD card breakout board is soldered on large solder board. Between the pin of SD card and 3.3V Vcc, a diode is used and a 1K resistor is connected between the microcontroller pin and SD card pin. If the diode is driven logic high, then the diode conducts and SD card pin is held at about 3.3V because of a low forward voltage drop of the diode. If the diode is driven logic low, then diode does not conduct and the SD card pin is at logic0. On MISO, pin a 57K resistor is used as a pull-up resistor.

5V to 3.3V Voltage Converter

The microcontroller voltage is 5V but the power supply required for the SD card and gyroscope is 3.3V only. So, a voltage converter is used for converting 5V into 3.3V and an adjustable voltage regulator LT1584 is used.

A simple voltage divider circuit is used for adjusting the output voltage based on the reference voltage. The formula for output voltage can be given as

Vout = Vref (1+R2/R1) + Iadj*R2

The overall embedded system circuit of these electrical components is shown in the figure and this circuit is used for measuring the foot pronation with each hardware part of performing the intended operation as discussed above. The results of these foot pronation are helpful to resolve the problems with over and under pronations.

We hope that this article with its brief explanation about the foot pronation detection might have helped you to understand the concept. Further, this project can be implemented using a wireless communication between the shoe circuit and the control panel for collecting and storing the data. Post your comments and queries for detailed information regarding this article such that other readers get awareness about these types of new innovative embedded system based electrical and electronic projects.

Photo Credits:

• Foot Pronation Detection by brooksmalaysia
• Embedded System Project on Pronation Detection by people.ece
• ATMega Target Board by hobbytronics
• MMA1260D Accelerometer by cit.cornell
• Sensitronic/Interlink FSR by interlinkelectronics
• LPR503AL Dual-Axis Gyroscope by hwkitchen
• SD Card Module by aliimg
• Foot Pronation Embedded System Circuit by cornell