CN113049002A - Conical motion testing method of tilt sensor - Google Patents

Abstract

The invention discloses a conical motion testing method of an inclination angle sensor, which comprises the following steps: a follow-up coordinate system is established, and the motion controller controls the servo motor to drive the branched chain to move so as to generate conical motion around the Z axis; the method comprises the steps that kinematic parameters such as a spherical hinge coordinate, a Hooke hinge coordinate and an initial offset of a telescopic leg of the Stewart platform are calibrated through a laser tracker, an accurate position forward model of the Stewart platform is established, and amplitude attenuation and phase lag influence of closed-loop response of a servo motor are eliminated; and then, the MEMS tilt sensor is arranged on the movable platform, the actual conical motion track is calculated through a position forward solution model to be used as a reference measurement value, and the reference measurement value is compared with the measurement value of the MEMS tilt sensor, so that the test and calibration of the MEMS tilt sensor are completed. And the Stewart platform can generate conical motion around the Z axis, and the conical point can be changed according to the requirement, compared with one-dimensional rotary motion, the conical motion has more superiority.

Description

A method for testing cone motion of inclination sensor

technical field

The invention belongs to the field of metrology testing, and is especially suitable for dynamic testing of a micro-electromechanical system (MEMS) inclination sensor and an inertial measurement unit.

Background technique

The MEMS dynamic inclination sensor is a high-performance inertial measurement device that can measure the attitude parameters of the moving carrier, and is suitable for inclination measurement under motion and vibration. It is mainly composed of an accelerometer and a gyroscope. Since the measurement data of the accelerometer is usually affected by the interference of the external environment and generates noise, and the measurement data of the gyroscope has drift error due to the integration, the real-time real-time data can be realized through the information fusion algorithm of the two. Dynamic inclination output, and improve work stability.

In order to ensure the validity of the measurement results, the MEMS inclination sensor needs to be tested. At present, the turntable and the indexing head are usually used to test the inclination sensor, and the accelerometer and gyroscope are tested by the multi-point tumbling method and the rate test method. Existing test methods are mainly used to determine the static error model of MEMS inclination sensors, including scale factor, bias, and non-orthogonality. With the increasing demand for dynamic measurement applications, the dynamic performance of MEMS inclination sensors has received more attention. Therefore, it is necessary to study the testing equipment and methods for the dynamic characteristics of the MEMS inclination sensor. A complete tilt motion is a two-DOF angular motion about an orthogonal axis in the horizontal plane. The existing multi-axis turntable can generate multi-axis angular motion, but it can only rotate around its own axis, and its motion form is limited by the mechanical structure of the turntable. The origin of the angular motion is the intersection of the two orthogonal axes of the turntable, and its position cannot be adjusted. .

Therefore, in view of the problems of insufficient dynamic characteristics and single motion form of the current MEMS inclination sensor tested by the turntable, the present invention proposes a conical motion test method of the inclination sensor, which tests the dynamic characteristics of the inclination sensor through the inclination motion of two degrees of freedom. , to obtain the response characteristics of the actual measurement environment of the sensor, to ensure the effectiveness and reliability of the inclination measurement system, and to meet the urgent needs of high-performance inclination sensors in various engineering application fields.

SUMMARY OF THE INVENTION

The purpose of the present invention is to propose a conical motion testing method of an inclination sensor, which generates a two-degree-of-freedom inclination motion through a Stewart platform, tests the dynamic characteristics of the inclination sensor, and solves the shortcomings of the rotary table test method such as insufficient dynamic characteristics and single motion form. .

In order to achieve the above object, the technical solution adopted in the present invention is to test the dynamic characteristics of the MEMS inclination sensor through the conical motion around the Z axis generated by the Stewart platform. The method includes: establishing a follow-up coordinate system, controlling a servo motor to drive the motion of a branch chain through a motion controller, and generating a conical motion around the Z-axis; calibrating the spherical joint coordinates, Hooke joint coordinates, and initial telescopic legs of the Stewart platform through a laser tracker Offset and other kinematic parameters, establish an accurate positive position solution model of the Stewart platform to eliminate the influence of amplitude attenuation and phase lag of the closed-loop response of the servo motor; then install the MEMS inclination sensor on the moving platform, and solve the actual conical motion through the positive solution model of the position The trajectory is used as a reference measurement value, which is compared with the measurement value of the inclination sensor to complete the test and calibration of the MEMS inclination sensor.

The Stewart platform generates conical motion around the Z-axis, including:

The conical motion around the Z axis is formed by rotating a certain angle α around the vector OL in the XOY plane, and OL rotates in the XOY plane with an angular velocity ω, and the quaternion method is used to describe the conic motion:

The angular velocity of the conic motion around the Z axis is given by:

A follow-up coordinate system of the moving platform is established, so that the origin of the coordinate system coincides with the cone point of the conical motion. According to the position coordinates of the spherical hinge center in the moving platform coordinate system and the Hooke hinge center in the static platform coordinate system, the length command of each telescopic leg is calculated in real time through the inverse position solution of the Stewart platform. Through the motion controller, the servo motor is controlled to drive the motion branch to extend or shorten, and the moving platform is driven to generate a conical motion around the Z axis.

The actual measurement method of conical motion around the Z axis includes:

A laser tracker was used to calibrate the kinematic parameters of the Stewart platform, such as the spherical hinge coordinates, the Hooke hinge coordinates, and the initial offset of the telescopic legs, and an accurate positive solution model of the Stewart platform was established. Collect the readings of the encoders of each telescopic leg in real time, obtain the real leg length information, solve the actual pose of the moving platform through the positive solution model of the position, and obtain the actual conical motion around the Z axis. Eliminates the amplitude decay and phase lag effects of the closed-loop frequency response of the servo motor.

The test methods of the MEMS tilt sensor based on conical motion include:

The MEMS inclination sensor is installed on the upper surface of the moving platform of the Stewart platform, and the Stewart platform is controlled to generate a series of conical motions with different frequencies and angles. Through the positive solution model of the position, the actual cone motion trajectory is calculated by the encoder as a reference measurement value; compared with the measurement value of the inclination sensor, the test and calibration of the MEMS inclination sensor are completed.

The MEMS tilt sensor is mainly composed of a three-axis accelerometer and a gyroscope, which can provide the angular velocity and acceleration of the three coordinate axes.

With respect to the reference coordinate system of the tilt sensor, the sensitivity of the accelerometer is:

和

是在圆锥运动激励下加速度计的X和Y轴振幅。in,

and

are the X and Y axis amplitudes of the accelerometer under cone motion excitation.

The sensitivity of the gyroscope is:

和

是在圆锥运动激励下陀螺仪的X和Y轴振幅。in,

and

are the X and Y axis amplitudes of the gyroscope under the excitation of conic motion.

和俯仰角θ来表示，其灵敏度如下所示：The sensitivity of the tilt sensor is determined by its roll angle

and the pitch angle θ to represent, its sensitivity is as follows:

和

是倾斜输出

的振幅。in

and

is the ramp output

amplitude.

Description of drawings

Fig. 1 is the Stewart platform schematic diagram in the specific embodiment of the method of the present invention;

Fig. 2 is the cone motion control and measurement flow chart around Z axis in the concrete real-time example of the present invention;

3 is a schematic diagram of a Stewart platform generating a conical motion around the Z-axis in a specific embodiment of the present invention;

Fig. 4 is the cone motion that generates around Z-axis in the specific embodiment of the present invention;

Fig. 5 is the sensitivity axis coordinate system of gyroscope and accelerometer in the present invention;

Fig. 6 is the deviation of the gyroscope sensitivity of the conical motion and the traditional turntable test in the specific embodiment of the present invention;

FIG. 7 is the deviation of the output sensitivity of the inclination angle of the cone motion in the specific embodiment of the present invention and the traditional turntable test.

Detailed ways

In order to test the dynamic characteristics of the inclination sensor and solve the shortcomings of the rotary table test method such as insufficient dynamic characteristics and single motion form, the present invention proposes a conical motion test method of the inclination sensor, which generates a two-degree-of-freedom inclination motion through the Stewart platform. The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

1 is a schematic diagram of an embodiment of the method of the present invention. The device mainly includes: Hook hinge 1, movable joint 2, ball hinge 3, lower branch 4, upper branch 5, static platform 6, moving platform 7, MEMS Inclination sensor 8, servo motor 9. The upper branch chain 5 and the lower branch chain 4 are connected by the moving joint 2, the upper branch chain 5 is connected with the moving platform 7 through the ball hinge 3, and the lower branch chain 4 is connected with the static platform 6 through the Hooke hinge 1; the servo motor 9 is installed on the support. On the chain, the branch chain is driven to move, which in turn drives the moving platform 7 to move to generate a conical motion around the Z-axis, and the cone point can be changed as required.

The MEMS inclination sensor 8 is installed on the moving platform 7 to measure the conical motion generated by the moving platform 7 in real time.

Referring to Figure 2, it is the control and measurement flow chart of the cone motion, which mainly includes the following steps:

Step S10: setting the predetermined conical motion of the Stewart moving platform;

Step S20: according to the predetermined motion trajectory, calculate the length of six motion branch chains by the position inverse solution;

Step S30: controlling the rotational motion of the servo motor through the motion controller;

Step S40: converting the rotational motion into the telescopic motion of the motion branch chain through the ball screw, and driving the moving platform to move by the six motion branch chains;

Step S50: at this time, the MEMS inclination sensor measures the conical motion of the moving platform in real time;

Step S60: feedback the measured value of the encoder to the driver and the motion controller;

Step S70: Obtain the real leg length information according to the encoder, and solve the actual pose of the moving platform through the positive position solution model to obtain the actual conical motion around the Z axis.

6 and 7 are experimental verifications of the test results of the present invention and the conventional turntable. It can be seen that the difference between the sensitivity deviation of the output of the gyroscope and the inclinometer and the test results of the traditional turntable is only 0.2dB and 0.1dB. The conical motion test method based on the Stewart platform is in good agreement with the results of the traditional turntable test method. effectiveness of the proposed method. Compared with traditional testing methods, the conical motion generated by the Stewart platform provides two degrees of freedom inclination motion, and completes multi-axial testing of accelerometers, gyroscopes and inclination output without reinstallation; the conical motion generated by the Stewart platform is The cone point can be flexibly adjusted according to the needs, which has a good advantage.

The above detailed description is a specific embodiment of the method of the present invention, and is not intended to limit the application scope of the present invention. Those skilled in the art can make a series of optimizations, improvements, equivalent modifications and the like on the basis of the present invention. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims (6)

1. A cone motion testing method of a tilt sensor is characterized by comprising the following steps: the method comprises the following steps: a follow-up coordinate system is established, and the motion controller controls the servo motor to drive the branched chain to move so as to generate conical motion around the Z axis; the method comprises the steps that kinematic parameters such as a spherical hinge coordinate, a Hooke hinge coordinate and an initial offset of a telescopic leg of the Stewart platform are calibrated through a laser tracker, an accurate position forward model of the Stewart platform is established, and amplitude attenuation and phase lag influence of closed-loop response of a servo motor are eliminated; then, the MEMS tilt sensor is installed on a movable platform, the actual conical motion track is calculated through a position forward solution model to be used as a reference measurement value, and the reference measurement value is compared with the measurement value of the MEMS tilt sensor to finish the test and calibration of the MEMS tilt sensor; and the Stewart platform generates conical motion around the Z axis, and the conical point is changed according to the requirement.

2. The cone motion testing method of a tilt sensor of claim 1, wherein: the method for generating the conical motion around the Z axis by the Stewart platform specifically comprises the following steps:

the conical motion about the Z-axis is formed by rotation by an angle α about a vector OL in the XOY plane, and OL rotates at an angular velocity ω in the XOY plane, describing the conical motion in a quaternion approach:

the angular velocity of the conical motion about the Z-axis is as follows:

establishing a follow-up coordinate system of the movable platform, and enabling the origin of the coordinate system to coincide with the cone point of the conical motion; according to the position coordinates of the center of the spherical hinge in the moving platform coordinate system and the center of the Hooke hinge in the static platform coordinate system, calculating in real time through the position inverse solution of the Stewart platform to obtain the length command of each telescopic leg; the motion controller controls the servo motor to drive the motion branched chain to extend or shorten, so as to drive the movable platform to generate conical motion around the Z axis.

3. The cone motion testing method of a tilt sensor of claim 1, wherein: the actual method for measuring the conical motion around the Z axis specifically comprises the following steps:

calibrating kinematic parameters such as a spherical hinge coordinate, a Hooke hinge coordinate and an initial offset of a telescopic leg of the Stewart platform by using a laser tracker, and establishing an accurate position forward model of the Stewart platform; acquiring the encoder reading of each telescopic leg in real time to obtain real leg length information, and resolving the actual pose of the moving platform through a position forward solution model to obtain the actual conical motion around the Z axis; the amplitude attenuation and the phase lag influence of the closed loop frequency response of the servo motor are eliminated.

4. The cone motion testing method of a tilt sensor of claim 1, wherein: the test method of the MEMS tilt angle sensor based on conical motion specifically comprises the following steps:

the MEMS tilt angle sensor is arranged on the upper surface of a movable platform of the Stewart platform, and the Stewart platform is controlled to generate a series of conical motions with different frequencies and angles; calculating an actual conical motion track by an encoder reading through a position forward solution model to be used as a reference measurement value; comparing the measured value with the measured value of the tilt sensor, and completing the test and calibration of the MEMS tilt sensor;

the MEMS tilt angle sensor consists of an accelerometer and a gyroscope of three axes and provides axial angular velocities and accelerations of three coordinate axes;

the sensitivity of the accelerometer with respect to the tilt sensor reference frame is:

wherein ,

and

is the X and Y axis amplitude of the accelerometer under cone motion excitation;

the sensitivity of the gyroscope is:

wherein ,

and

is the X and Y axis amplitude of the gyroscope under cone motion excitation;

sensitivity of tilt sensor is determined by its roll angle

And pitch angle θ, the sensitivity of which is shown below:

wherein

And

is a tilting output

The amplitude of (d).

5. The cone motion testing method of a tilt sensor of claim 1, wherein: the method of generating a conical motion comprises the steps of:

step S10: setting the preset conical motion of a Stewart moving platform;

step S20: calculating the lengths of six moving branched chains through position inverse solution according to a preset moving track;

step S30: the servo motor is controlled to rotate by the motion controller;

step S40: the rotary motion is converted into the telescopic motion of the motion branched chains through the ball screw, and the six motion branched chains drive the movable platform to move;

step S50: at the moment, the MEMS tilt angle sensor measures the conical motion of the movable platform in real time;

step S60: feeding back the measured value of the encoder to the driver and the motion controller;

step S70: and (3) obtaining real leg length information according to the encoder, and resolving the actual pose of the moving platform through a position forward solution model to obtain the actual conical motion around the Z axis.

6. A conical motion testing apparatus for a tilt sensor designed by the method of claim 1, wherein:

the device includes: the system comprises a Hooke hinge, a movable joint, a spherical hinge, a lower branched chain, an upper branched chain, a static platform, a movable platform, an MEMS (micro-electromechanical system) tilt angle sensor and a servo motor; the upper branched chain is connected with the lower branched chain through a movable joint, the upper branched chain is connected with the movable platform through a spherical hinge, and the lower branched chain is connected with the static platform through a Hooke hinge; the servo motor is arranged on the branched chain and drives the branched chain to move so as to drive the movable platform to move and generate conical motion around the Z axis, and the conical point is changed according to the requirement; the MEMS tilt angle sensor is arranged on the movable platform and used for measuring the conical motion generated by the movable platform in real time.

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