Merilnik navora in moči kolesarja

Brecl, Gabrijela (author), Pirc, Matija (mentor)

V amaterskem kolesarstvu se vedno pogosteje uporabljajo različni merilniki, vendar je na voljo le malo cenovno ugodnih merilnikov moči. Izdelan je bil merilnik, ki meri navor in moč, s katero kolesar poganja kolo. Na gonilko kolesa so pritrjeni uporovni merilni lističi, ki se v skladu z obremenitvijo gonilke raztezajo ali krčijo. Vezani so v Wheatstoneov mostič in na izhod podajo napetost sorazmerno uporabljeni sili. Napetost nam ojačevalnik in analogno-digitalni pretvornik HX711 pretvori v digitalno vrednost. Z mikroprocesorjem iz družine STM32 to vrednost preberemo in izračunamo silo. S podatkom o dolžini gonilke pa izračunamo še navor. S pomočjo žiroskopa in pospeškometra MPU6050 dobimo podatek o kotni hitrosti gonilke. Moč izračunamo kot produkt navora in kotne hitrosti in jo preko brezžične povezave pošljemo uporabniku. Za komunikacijo je uporabljen modul HC-05, ki porablja brezžični protokol Bluetooth. Podatke lahko sprejemamo in prikazujemo s programom na osebnem računalniku. Z drugim programom izvedemo kalibracijo merilnika, kjer nastavimo dolžino gonilke in z meritvijo znane obremenitve določimo parametre za izračun sile. Končni izdelek je primeren za pritrditev na gonilko kolesa in uporabniku omogoča vpogled v izmerjene ter izračunane podatke v realnem času.

• Language: Slovenian
• Keywords: merilnik moči, moč, navor, kolo, uporovni merilni listič, Wheatstoneov mostič, Bluetooth, mikroprocesor
• Work type: Bachelor thesis/paper
• Organization: FE - Faculty of Electrical Engineering
• Year: 2023
• PID: 20.500.12556/RUL-150062
• COBISS.SI-ID: 165082371
• Publication date in RUL: 13.09.2023

Secondary language

• Language: English
• Title: Cycling Torque and Power Meter

Abstract

Amateur cycling is increasingly using a variety of power meters, but there are not many affordable power meters available. This thesis describes the power meter that measures the torque and power that a cyclist uses to spin the crank arm of a bicycle. Strain gauges are attached to the crank of the bicycle. They either stretch or contract as the crank is loaded. The connection of four strain gauges in a Wheatstone bridge provides a voltage output proportional to the applied force. The voltage is converted to a digital value by the HX711 amplifier and analogue-to-digital converter. This value is read and the force is calculated using an STM32 family microprocessor. Using the length of the crank arm, we can then calculate the torque. The MPU6050 gyroscope and accelerometer is used to obtain the angular velocity of the crank arm. The power is calculated as the product of the torque and the angular velocity and sent to the user via a wireless connection. A HC-05 module was used that works with the Bluetooth protocol. The data can be received and displayed using a program on a personal computer. A second program is used to perform the calibration of the power meter, where the length of the crank arm is set and the parameters for the force calculation are determined by a measurement using a known load. The final product is suitable for attachment to a bicycle crank arm and allows the user to view the measured and calculated data in real time.

• Keywords: power meter, power, torque, bike, strain gauge, Wheatstone bridge, Bluetooth, microprocessor