Acceleration resolving algorithm parameter optimization method based on inertial measurement unit and computer system

Abstract

The invention discloses an acceleration resolving algorithm parameter optimization method based on an inertial measurement unit (IMU), which comprises the following steps of: deducing an acceleration resolving algorithm considering an IMU attitude error based on multi-body dynamics; an acceleration sensor is installed at a vehicle body point with the acceleration to be calculated, a high-precision IMU is installed in a vehicle cabin, and the distance between the vehicle body point to be calculated and the IMU is measured through a tape; a vehicle is driven to run on a non-flat road surface, and acceleration sensor signals and IMU signals are acquired through data acquisition equipment; selecting at least 50 groups of data under the working condition that the automobile moves violently, and establishing a target function; solving optimal parameters by adopting a genetic algorithm; and substituting the solved optimal parameter to obtain a calculation formula for calculating the acceleration of any point by the IMU. The method has the advantages that the measurement mode of the position of the calculation point in the IMU coordinate system is simplified, the optimal parameter is obtained through the genetic algorithm, and the accuracy of calculating the acceleration by the IMU is greatly improved.

Description

Technical Field

[0001] The present invention relates to the field of vehicle control systems, and in particular to an acceleration solution algorithm parameter optimization method and a computer system based on an inertial measurement unit. Background Art

[0002] The precise control of the active suspension system and the electronic stability control system ESC (Electronic Stability Control) of the vehicle depends on the measurement of the vertical acceleration by the vehicle acceleration sensor. The traditional acceleration sensor layout scheme is relatively complex, requires a large number of electrical channels and is costly. With the development of intelligent driving technology, more and more vehicles are equipped with vehicle inertial measurement units IMU (Inertial Measurement Unit). If only one IMU is used to obtain the acceleration of each point on the vehicle body, the electrical environment can be greatly simplified and costs can be saved. However, the IMU's solution of the acceleration of various parts of the vehicle body requires precise measurement of the position of each point in the IMU coordinate system. Even if measured by precision instruments, there is still a certain error. The error comes from the instrument measurement error on the one hand, and from the attitude error of the IMU installation on the other hand. The farther the solution point is from the IMU straight-line distance, the greater the error of the solution result. This is where the application needs to focus on improvement. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method and a computer system for optimizing the parameters of an acceleration solution algorithm based on an inertial measurement unit, thereby simplifying the measurement method of the position of a solution point in an IMU coordinate system and improving the accuracy of acceleration solution by the IMU.

[0004] In order to solve the above technical problems, the present invention provides an acceleration solution algorithm parameter optimization method based on an inertial measurement unit, comprising the following steps:

[0005] Step S1, based on multi-body dynamics, derive an acceleration solution algorithm that takes into account IMU attitude errors;

[0006] Assume that the vector basis composed of three orthogonal unit vectors in the absolute coordinate system is the reference basis e r , the vector basis composed of three orthogonal unit vectors of the IMU coordinate system is the conjoined basis e b , e r With e b The relationship is:

[0007] e r =Ae b (1)

[0008] Where: A is the rotation coordinate matrix; Assume that a point fixed in the conjoined basis moves from P to P″, according to Euler's theorem of general motion of rigid bodies: in the reference basis, the displacement r of this point is decomposed into the sum of the displacement R of the translation with the conjoined basis and the displacement u of the rotation around the base point of the conjoined basis, that is,

[0009]

[0010] In order to measure the position of a point in the reference basis and the conjoined basis, the coordinate matrix of point P in the reference basis is [x i ,y i ,z i ] T , then the coordinate matrix of point P′ in the reference basis is [x i ,y i ,z i ] T +R,P″’s coordinate matrix is ​​A[z i ,y i ,z i ] T +R, which can be written as:

[0011]

[0012] Assuming that the vehicle body is a rigid body, the coordinate matrix of any point on the vehicle body in the conjoined basis is unchanged; when calculating the rotation matrix A, first consider the rotation yaw angle α around the Z axis of the IMU coordinate system, then consider the rotation pitch angle β around the Y axis, and finally consider the rotation roll angle γ around the X axis, then the rotation matrix is:

[0013] A=A γ A β A α (4)

[0014]

[0015] The time derivative of both sides of formula (5) is:

[0016]

[0017] In the formula, ω x ,ω y ,ω z are the angular velocities around the X-axis, Y-axis, and Z-axis respectively;

[0018] Therefore, the time derivative of the rotation matrix A is:

[0019]

[0020] Then, the velocity and acceleration of point P can be obtained by differentiating both ends of equation (3) with respect to time:

[0021]

[0022] The acceleration sensor installed at the suspension position measures the acceleration in the direction perpendicular to the plane of the vehicle body. The absolute acceleration vector calculated by the IMU is converted along the Z i Axis projection, The vector expression converted to the absolute coordinate system is:

[0023]

[0024] Where: subscript A represents the vector expression in the absolute coordinate system;

[0025] According to the vector dot product formula, the absolute acceleration is equal to Z i Axis angle and IMU acceleration (a I ) The acceleration perpendicular to the plane of the vehicle body at P is solved as:

[0026]

[0027] Combining (9) to (11), we can get the acceleration perpendicular to the vehicle body plane at P″:

[0028]

[0029] Similarly, the acceleration parallel to the plane of the vehicle body is derived as:

[0030]

[0031] The above derivation is based on the fact that the IMU has no installation attitude error, that is, the IMU coordinate system is parallel to the vehicle coordinate system; in fact, there is always an error in the IMU installation attitude, so when solving the acceleration, there is an angle between the calculated acceleration direction and the actual direction, that is, the actual acceleration:

[0032]

[0033] Among them: cos a, cosb, cosc ​​are the cosine values ​​of the angles between the acceleration direction of the vehicle body point to be solved and the X-axis, Y-axis and Z-axis of the IMU coordinate system, that is, the IMU installation attitude error parameters, and it is assumed that the angle will not exceed 90 degrees, that is,

[0034] Step S2, installing an acceleration sensor at the point on the vehicle body where the acceleration is to be calculated, and installing a high-precision IMU in the vehicle cabin, and using a distance measuring tool to measure the distance l from the point on the vehicle body to be calculated to the IMU;

[0035] Step S3: driving the vehicle on a non-flat road and collecting acceleration sensor signals through a data acquisition device and IMU signal Make the sampling frequency consistent;

[0036] Step S4: Select at least 50 sets of data of automobile movement under severe working conditions and establish the objective function:

[0037]

[0038] Create a constraint function:

[0039] g(x i ,y i ,z i )=x i2 +y i2 +z i2 <l 2 ;

[0040] Step S5: Using genetic algorithm, in the constraint function g(x i ,y i ,z i ) <l 2 Under the condition of i ,y i ,z i ) is minimized and five parameters are optimized;

[0041] Step S6: Substitute the optimal parameters obtained in step S5 into equation (15) to obtain the IMU solution formula for calculating the acceleration of any point.

[0042] The present invention provides a computer system, comprising a memory, a processor and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of an acceleration solution algorithm parameter optimization method based on an inertial measurement unit.

[0043] The beneficial effects of the present invention are: simplifying the measurement method of the position of the solution point in the IMU coordinate system, eliminating the need to accurately measure the position of the solution point in the IMU coordinate system, and correcting the attitude error of the acceleration sensor in the IMU coordinate system. The optimal parameters are obtained through a genetic algorithm, which greatly improves the accuracy of the IMU solution acceleration. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0045] Figure 1 is the coordinate system and vector definition of a specific embodiment of the present invention;

[0046] Figure 2 is a flow chart of a specific embodiment of the present invention;

[0047] Figure 3 It is a comparison diagram of optimization solution effects of a specific embodiment of the present invention. DETAILED DESCRIPTION

[0048] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0049] like Figure 2 As shown, the present invention provides a method for optimizing parameters of an acceleration solution algorithm based on an inertial measurement unit, comprising the following steps:

[0050] Step 1: Based on multi-body dynamics, derive the acceleration solution algorithm considering the IMU attitude error;

[0051] Assume that the vector basis composed of three orthogonal unit vectors in the absolute coordinate system is the reference basis (set as e r ), the vector basis composed of three orthogonal unit vectors of the IMU coordinate system is the conjoined basis (set as e b ), e r With e b The relationship is:

[0052] e r =Ae b (1)

[0053] Where: A is the rotation coordinate matrix; Assume that a point fixed in the conjoined basis moves from P to P″, according to Euler's theorem of general motion of rigid bodies: in the reference basis, the displacement r of this point is decomposed into the sum of the displacement R (i.e. R′) of the translation with the conjoined basis and the displacement u of the rotation around the base point of the conjoined basis, i.e.

[0054]

[0055] In order to measure the position of a point in the reference basis and the conjoined basis, such as Figure 1 As shown, let the coordinate matrix of point P in the reference basis be [x i ,y i ,z i ] T , then the coordinate matrix of point P′ in the reference basis is [x i ,y i ,z i ] T +R,P″’s coordinate matrix is ​​A[x i ,y i ,z i ] T +R, which can be written as:

[0056]

[0057] Assuming that the vehicle body is a rigid body, the coordinate matrix of any point on the vehicle body in the conjoined basis is unchanged; when calculating the rotation matrix A, first consider the rotation around the Z axis of the IMU coordinate system (yaw angle α), then consider the rotation around the Y axis (pitch angle β), and finally consider the rotation around the X axis (roll angle γ), then the rotation matrix is:

[0058] A=A γ A β A α (4)

[0059]

[0060] The time derivative of both sides of formula (5) is:

[0061]

[0062] In the formula, ω x ,ω y ,ω z They are the angular velocities around the X-axis, Y-axis, and Z-axis respectively; therefore, the time derivative of the rotation matrix A is:

[0063]

[0064] Then, the velocity and acceleration of point P can be obtained by differentiating both ends of equation (3) with respect to time:

[0065]

[0066] From formula (9), we can know that the acceleration of a point in the connected base is composed of the displacement acceleration of the connected base point, the tangential acceleration of this point and the centripetal acceleration. Since the acceleration sensor installed at the suspension position measures the value along the plane perpendicular to the vehicle body (the plane is defined as the horizontal plane with the average height of each spring position, the plane perpendicular to this plane is Z i The acceleration in the Z-axis direction is the absolute acceleration vector calculated by the IMU. i Axis projection, The vector expression converted to the absolute coordinate system is

[0067]

[0068] Where: subscript A represents the vector expression in the absolute coordinate system;

[0069] According to the vector dot product formula, the absolute acceleration is equal to Z i Axis angle and IMU acceleration (a I ) The acceleration perpendicular to the vehicle body plane at P is solved as:

[0070]

[0071] Combining (9) to (11), we can obtain the acceleration perpendicular to the vehicle body plane at P″:

[0072]

[0073] Similarly, the acceleration parallel to the plane of the vehicle body is derived as:

[0074]

[0075] The above derivation is based on the fact that the IMU has no installation attitude error, that is, the IMU coordinate system is parallel to the vehicle coordinate system; in fact, there is always an error in the IMU installation attitude, so when solving the acceleration, there is an angle between the calculated acceleration direction and the actual direction, that is, the actual acceleration:

[0076]

[0077] Among them: cos a, cosb, cosc ​​are the cosine values ​​of the angles between the acceleration direction of the vehicle body point to be solved and the X-axis, Y-axis and Z-axis of the IMU coordinate system, that is, the IMU installation attitude error parameters, and it is assumed that the angle will not exceed 90 degrees, that is,

[0078] Step 2: Install an acceleration sensor at the point on the vehicle body where the acceleration is to be calculated, and install a high-precision IMU in the vehicle cabin. Use a tape measure to measure the distance l from the point on the vehicle body to be calculated to the IMU.

[0079] Step 3: Drive the vehicle on a bumpy road and collect acceleration sensor signals through data acquisition equipment and IMU signal Ensure consistent sampling frequency;

[0080] Step 4: Select 50 sets of data under conditions where the car moves violently and establish the objective function:

[0081]

[0082] Create a constraint function:

[0083] g(x i ,y i ,z i )=x i2 +y i2 +z i2 <l 2 ;

[0084] Step 5: Use genetic algorithm to find the constraint function g(x i ,y i ,zi ) <l 2 Under the condition of i ,y i ,z i ) is minimized and five parameters are optimized;

[0085] Step S6: Substitute the optimal parameters obtained in step S5 into equation (15) to obtain the IMU solution formula for calculating the acceleration of any point.

[0086] like Figure 3 As shown, when the vehicle is traveling under pulse input conditions, the vertical acceleration of the vehicle body (blue line) calculated by the optimization method of the present invention has higher accuracy and smaller root mean square error than the acceleration calculated by the algorithm that does not consider the posture and error (green line).

[0087] The present invention provides a computer system, comprising a memory, a processor and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of an acceleration solution algorithm parameter optimization method based on an inertial measurement unit.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for optimizing parameters of an acceleration solution algorithm based on an inertial measurement unit, comprising the following steps: Step S1, based on multi-body dynamics, derive an acceleration solution algorithm that takes into account IMU attitude errors; Assume that the vector basis composed of three orthogonal unit vectors in the absolute coordinate system is the reference basis e r , the vector basis composed of three orthogonal unit vectors of the IMU coordinate system is the conjoined basis e b , e r With e b The relationship is: And r =Ae b (1) in: A is the rotation coordinate matrix; suppose a point fixed in the conjoined basis moves from P to P″, in the reference basis, the displacement r of this point is decomposed into the sum of the displacement R of the translation with the conjoined basis and the displacement u of the rotation around the base point of the conjoined basis, that is, In order to measure the position of a point in the reference basis and the conjoined basis, the coordinate matrix of point P in the reference basis is [x i ,y i ,z i ] T , then P ′ The coordinate matrix of the point in the reference basis is px i ,y i ,z i ] T +R,P″’s coordinate matrix is ​​A[x i ,y i ,z i ] T +R, which can be written as: Assuming that the vehicle body is a rigid body, the coordinate matrix of any point on the vehicle body in the conjoined basis is unchanged; when calculating the rotation matrix A, first consider the rotation yaw angle α around the Z axis of the IMU coordinate system, then consider the rotation pitch angle β around the Y axis, and finally consider the rotation roll angle γ around the X axis, then the rotation matrix is: A=A γ A β A α (4) The time derivative of both sides of formula (5) is: In the formula, ω x ,ω y ,ω z are the angular velocities around the X-axis, Y-axis, and Z-axis respectively; The time derivative of the rotation matrix A is: Then, the velocity and acceleration of point P can be obtained by differentiating both ends of equation (3) with respect to time: The acceleration sensor installed at the suspension position measures the value along the plane perpendicular to the vehicle body Z i The acceleration in the Z direction is calculated by the IMU. i Axis projection, The vector expression converted to the absolute coordinate system is: Where: subscript A represents the vector expression in the absolute coordinate system; According to the vector dot product formula, the absolute acceleration is equal to Z i Axis angle and IMU acceleration (a I ) The acceleration perpendicular to the vehicle body plane at P is solved as: Combining (9) to (11), we can obtain the acceleration perpendicular to the vehicle body plane at P″: Similarly, the acceleration parallel to the plane of the vehicle body is derived as: When solving for acceleration, there is an angle between the calculated acceleration direction and the actual direction, that is, the actual acceleration: Among them: cos a, cos b, cos c are the cosine values ​​of the angles between the acceleration direction of the vehicle body point to be solved and the X-axis, Y-axis and Z-axis of the IMU coordinate system, that is, the IMU installation attitude error parameters, and it is assumed that the angle will not exceed 90 degrees, that is, Step S2, installing an acceleration sensor at the point on the vehicle body where the acceleration is to be calculated, and installing a high-precision IMU in the vehicle cabin, and using a tape measure tool to measure the distance l from the point on the vehicle body to be calculated to the IMU; Step S3: driving the vehicle on a non-flat road and collecting acceleration sensor signals through a data acquisition device and IMU signal Step S4: Select at least 50 sets of data of automobile movement under severe working conditions and establish the objective function: Create a constraint function: Step S5: Using genetic algorithm, in the constraint function g(x i ,y i ,z i ) <l 2 Under the condition of f(cos a,cos b,x i ,y i ,z i ) is minimized and five parameters are optimized; Step S6: Substitute the optimal parameters obtained in step S5 into equation (15) to obtain the IMU solution formula for calculating the acceleration of any point.

2. A computer system comprising a memory, a processor and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of the method of claim 1.

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