Design of a low-cost force insoles to estimate ground reaction forces during human gait

This paper proposes a low-cost electronic system for estimating ground reaction forces (GRF) during human gait. The device consists of one master node and two slave nodes. The master node sends instructions to slave nodes that sample and store data from two force insoles located at the participant's feet. These insoles are equipped with 14 piezo-resistive FlexiForce A301 sensors (FSR). The slave nodes are attached to the ankles and feet of each participant. Subsequently, the start command is transmitted through the master node, which is connected to the USB port of a personal computer (PC). Once the walking session is completed, the information obtained by the slave nodes can be downloaded by accessing the access point generated by these devices through Wi-Fi communication. The GRF estimation system was validated with force platforms (<i>BTS Bioengineering P6000, Italy</i>), giving on average a <i>fit</i> measure equal to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>68</mml:mn> <mml:mo>.</mml:mo> <mml:mn>71</mml:mn> <mml:mtext>%</mml:mtext> <mml:mo>±</mml:mo> <mml:mn>4</mml:mn> <mml:mo>.</mml:mo> <mml:mn>80</mml:mn> <mml:mtext>%</mml:mtext></mml:mrow> </mml:math> in dynamic situations. Future versions of this device are expected to increase this <i>fit</i> by using machine learning models.