diff --git a/README.md b/README.md index abbdb5d..9d648c5 100644 --- a/README.md +++ b/README.md @@ -12,7 +12,7 @@ Fusion is a sensor fusion library for Inertial Measurement Units (IMUs), optimis The Attitude And Heading Reference System (AHRS) algorithm combines gyroscope, accelerometer, and magnetometer data into a single measurement of orientation relative to the Earth. The algorithm also supports systems that use only a gyroscope and accelerometer, and systems that use a gyroscope and accelerometer combined with an external source of heading measurement such as GPS. -The algorithm is based on the revised AHRS algorithm presented in chapter 7 of [Madgwick's PhD thesis](https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.681552). This is a different algorithm to the better-known initial AHRS algorithm presented in chapter 3, commonly referred to as the *Madgwick algorithm*. +The algorithm is based on the revised AHRS algorithm presented in chapter 7 of [Madgwick's PhD thesis](https://x-io.co.uk/downloads/madgwick-phd-thesis.pdf). This is a different algorithm to the better-known initial AHRS algorithm presented in chapter 3, commonly referred to as the *Madgwick algorithm*. The algorithm calculates the orientation as the integration of the gyroscope summed with a feedback term. The feedback term is equal to the error in the current measurement of orientation as determined by the other sensors, multiplied by a gain. The algorithm therefore functions as a complementary filter that combines high-pass filtered gyroscope measurements with low-pass filtered measurements from other sensors with a corner frequency determined by the gain. A low gain will 'trust' the gyroscope more and so be more susceptible to drift. A high gain will increase the influence of other sensors and the errors that result from accelerations and magnetic distortions. A gain of zero will ignore the other sensors so that the measurement of orientation is determined by only the gyroscope.