09,22,2026 26 views
1 Explanation
Measuring the tilt angle of an object isAccelerator sensorA common application. Although its basic principle is very simple, there are still many difficulties encountered in practical implementation, such as the accuracy of the tilt angle and the complexity of mathematical calculations. This article will discuss in detail the issue of accuracy and provide a simplified calculation method.
2 Basic principles
Due to the gravitational force acting on the accelerometer when it is placed at rest, there will be a gravitational acceleration of 1g. By utilizing this property, the tilt angle of the accelerometer in the vertical plane can be calculated by measuring the components of gravity acceleration on the X-axis and Y-axis of the accelerometer.
In this way, based on the above principle, a 2-axis accelerometer can measure the tilt angle in the X-Y plane.
It should be noted that the 2-axis accelerometer can only measure gravity components on the X-axis and Y-axis, and therefore can only measure tilt angles on the X-Y plane. However, due to the difficulty in ensuring that the object is tilted in the X-Y plane when tilted in space, using only a 2-axis accelerometer for measurement may have limitations. Therefore, we consider using a 3-axis accelerometer. As shown in the figure below, the 3-axis accelerometer can measure the gravity components of the X, Y, and Z axes. The formula for calculating the spatial tilt angle can be extended to
This formula is the basic principle used in this article to measure the tilt angle of an object. It should be noted that the property used here is that an object is subject to gravity when at rest. If the object also experiences motion acceleration, then this formula will no longer be accurate. So it is necessary to add a constraint to the formula, that is
3 Hardware Implementation
At present, acceleration sensors used in consumer products are divided into two types: digital output (such as ADXL345) and analog output (such as ADXL335). The acceleration sensor with digital output can be directly connected to the MCU through I2C or SPI bus; Analog output acceleration sensors require the use of ADC for sampling. Nowadays, most commonly used MCUs have built-in ADC channels, so both digital and analog output acceleration sensors can be easily connected to the MCU to achieve measurement functions.
