The vehicle environment is mainly affected by bumps in the vehicle body, and the use environment such as power supply must be properly considered. Short working duration The single test of automobile sports, such as braking, handling stability, etc., can generally be completed in a few seconds to several tens of seconds. Therefore, this article describes it as a short-term inertial measurement system. Short measurement duration can reduce the accuracy requirements of inertial sensors and help reduce costs.
When real-time data processing SINS is used as navigation, navigation data must be solved in real time. As an automobile test, data can be recorded until the single test is completed and the test model is solved and output. This is very beneficial to the post-processing of data and error compensation. It plays an important role in the accuracy requirements of the test.
No need to measure absolute heading angle The absolute heading angle is relative to the true north angle. This helps to reduce the gyroscope's accuracy requirements. The following proposes the test system program and analyzes relevant issues. Test system composition and function system composition and function are shown. Mainly by the integrated sensor components, portable computers, pedal force sensor, steering wheel angle sensor, interface circuit and data channels, car power supply and other components.
The integrated sensor assembly is a key part of the system and consists of a 3-axis accelerometer, a 3-axis rate gyroscope, and a dual-axis level sensor. The accelerometer is used to sense the acceleration of the vehicle body in 3 vertical directions, and the gyro senses the angular velocity of the vehicle body around 3 vertical directions. With 6-dimensional measurement information, the movement of the vehicle body in space can be completely determined. A biaxial level sensor is used to measure the initial attitude. The integrated sensor assembly should be installed close to the center of mass of the car, in the same direction as the body coordinate system.
The portable computer completes the collection, processing, calculation, storage, management, and output of data. It is also the main man-machine interface. The computer is required to have fast speed and large capacity. The computer needs to complete the processing and calculation function parameters, including preprocessing, motion resolution, motion transformation, performance analysis and so on.
The pedal force sensor is used to measure the brake pedal force as an auxiliary signal when analyzing the braking performance, such as measuring the brake delay. The steering wheel angle sensor is used to measure the input steering angle of the steering wheel, which is indispensable in the analysis and calculation of various characteristics and parameters of the steering stability. If the test turns to light, additional steering wheel torque sensors are needed. The interface circuit converts the output signal of each sensor into an A/D input signal. It requires the circuit to work reliably and stably, and has excellent anti-interference performance. The on-board power supply provides the required working voltage for each part and is powered by a car battery or a dedicated battery. It requires small size, light weight, high efficiency, and high power.
Test Calculation Methods Data Preprocessing Measurement data should first be preprocessed to eliminate high-frequency random disturbances and occasional errors in sensors, interface circuits, and signal transmission. Checkpoint processing is an effective way to eliminate occasional errors. Tests with particularly large deviations from neighboring data are rejected and checked out. This reduces the noise level, but the selection of tolerance values ​​should be based on the statistical analysis of the entire data. .
The digital filter is applied after the processing of the checkpoint to filter out the high frequency noise. To select the appropriate upper limit frequency in order to save the useful signal. The movement of the car is relatively strong. In order not to lose the real change signal and remove the interference, the data should be processed in segments. Distinguish between the steady change section and the drastic change section, select different tolerable tolerance values ​​and upper limit frequencies.
The simplified model of the inertial measurement system of motion solution method is as follows: Vep=f+g(1)Wpb=Wib-Wie(2) where Vep is the velocity vector of the body navigation platform coordinate system with respect to the earth; f is the accelerometer's Specific gravity vector; g is the gravity acceleration vector; Wpb is the system structure of the body coordinate system relative to the body navigation platform coordinate system and the angular velocity vector of the functional test; Wib is the angular velocity vector of the body coordinate system relative inertial coordinate system; Wie is the earth Rotary angular velocity vector of the relative inertial coordinate system.
Solving Eqs. (1) and (2), you can get the 33 error correction inertial sensor of the car body coordinate system relative to the navigation coordinate system. The small error of the inertial sensor will cause the movement measurement error to diverge, which is caused by the integral principle of inertial measurement. . The error model of the sensor is very complicated, it is impossible to recognize the error model and its parameters well, and many parameters will change with time and external conditions.
In the short-term working situation, it can be considered that the sensor error is mainly a constant bias. Calculate the equivalent error according to the boundary value condition. After correcting the sensor signal, recalculate equations (1) and (2), which can greatly improve the measurement accuracy. The boundary condition is as follows: In the formula, the yaw angle of the vehicle body (in the navigation, it is called the heading angle), the pitching angle and the roll angle; x, y, z are the position coordinates of the vehicle body; tf is the measurement final time. The sensor bias error can be determined according to equations (3) and (4).
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