JP2004125731A - Attitude angle detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a useful communication algorithm for an attitude angle detector communicating between an arithmetic means and sensor parts by a long-distance communication, wherein the detector is provided with gyroscopes detecting angular velocity around three axes, acceleration sensors sensing at least around two axes, magnetic sensors detecting at least two-axis earth magnetism, and an arithmetic means for calculating the attitude angles. <P>SOLUTION: This attitude angle detector is capable of securing a responsiveness of the detector without reducing a precision of the attitude angle detector by executing data communication between the sensor parts and the arithmetic means in such a way that it transfers the data output from the gyroscopes detecting the angular velocity every time, and transfers data output from the acceleration sensors and the magnetic sensors alternatively every other time. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is a head mounted display used for posture detection and posture control of a moving body, virtual reality, and the like. A tracker for detecting a posture angle of a head, a 3D game pad, and the like for measuring an object to be measured in a three-dimensional space. The present invention relates to a posture angle detection device suitable for detecting a posture angle (a rotation angle of three axes).
[0002]
[Prior art]
In the attitude angle detecting device used for measuring and controlling the attitude of an airplane or a ship, accuracy and reliability have been emphasized, so that the size and the price did not matter relatively. However, in applications to consumer use such as 3D games, size and price are most important. There is a demand for the use of small and low-priced products for all components as well as sensors such as gyros, acceleration sensors, and magnetic sensors.
[0003]
Microcomputers are no exception. In the attitude angle detection device using the gyro, the acceleration sensor, and the magnetic sensor, various calculations are performed on the output from the sensor to determine the attitude angle. If this calculation is performed by a microcomputer, a microcomputer capable of floating-point arithmetic is required, and miniaturization and cost reduction cannot be realized.
[0004]
Thus, a method is conceivable in which the output value from the sensor is directly sent to a host machine such as a personal computer, and the calculation for obtaining the attitude angle is performed by the CPU of the host machine. In this method, there is no need for the microcomputer to perform the calculation, and it is only necessary to take the data of the sensor output and communicate with the host machine. Therefore, miniaturization and cost reduction can be easily realized.
[0005]
At present, the most suitable communication method is USB communication / low speed device / interrupt transfer. The reason why USB communication is optimal is that multiple connections are easy and power is supplied.
[0006]
[Problems to be solved by the invention]
However, when the above method is used, the communication cycle is 8 ms from the USB standard, and the amount of data that can be transferred at one time is 8 bytes. If the data to be transferred is within 8 bytes, the data is transmitted every 8 ms. If the data to be transferred is 8 to 16 bytes, the data is divided into two, such as data 1 for the first 8 ms and data 2 for the next 8 ms. Sent. On the other hand, the sensor output value data to be transferred is at least 10 bits A / D × 7 = 70 bits and exceeds 8 bytes. Accordingly, if the data is sent as it is, the data is divided and transmitted twice, so that one cycle becomes 16 ms, and there is a problem that responsiveness cannot be secured.
[0007]
In addition, if the A / D resolution is set to 9 bits in order to ensure responsiveness, the data amount can be suppressed to within 8 bytes. However, there has been a problem that the accuracy of the result of calculating the attitude angle deteriorates.
[0008]
The present invention is directed to a communication algorithm which solves the above-described problem of the attitude angle detecting device, and which ensures responsiveness and does not reduce accuracy. With this algorithm, an ideal posture angle detecting device is provided.
[0009]
[Means for Solving the Problems]
The present invention provides a gyro that detects angular velocities around three axes, an acceleration sensor that detects at least two axes of acceleration, a sensor unit that includes at least two axes of magnetic sensors that detect geomagnetism, Calculating means for calculating, wherein the sensor unit and the calculating means are attitude angle detecting devices for transferring data by remote communication, and in the communication of data between the sensor unit and the calculating means, the gyro is used. Is output every time, and at least data output from the acceleration sensor and the magnetic sensor are alternately transferred every other time.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this case, the posture angle detecting device having nine sensors (three gyros, three acceleration sensors, and three magnetic sensors) will be described. However, the same applies to those having seven or more sensors.
[0011]
FIG. 1 shows an arrangement of a gyro, an acceleration sensor, and a magnetic sensor in the posture angle detecting device of the present invention. In the sensor coordinate system shown in FIG. 1, a first gyro 11, a second gyro 12, and a third gyro 13 for detecting angular velocities around three axes (Xs axis, Ys axis, and Zs axis) orthogonal to each other. Are arranged parallel to the Xs axis, the Ys axis, and the Zs axis, that is, orthogonal to each other. The first acceleration sensor 14, the second acceleration sensor 15, and the third acceleration sensor 16 are arranged in parallel to three axes, the Xs axis, the Ys axis, and the Zs axis, which are orthogonal to each other. Similarly, the first magnetic sensor 17, the second magnetic sensor 18, and the third magnetic sensor 19 are arranged in parallel to three axes, the Xs axis, the Ys axis, and the Zs axis, which are orthogonal to each other.
[0012]
FIG. 2 is a diagram illustrating an overall configuration of the posture angle detecting device according to the embodiment of the present invention. The gyro 22, the acceleration sensor 23, and the magnetic sensor 24 output angular velocity (ωx, ωy, ωz), acceleration (Ax, Ay, Az), and geomagnetism (Mx, My, Mz), respectively. Each sensor output is converted into digital data by an A / D converter built in the microcomputer 25, and is transferred to the personal computer 26 by USB communication which is one of remote communication. The attitude angle calculation means 28 of the personal computer 26 calculates the attitude angle of the sensor module 21 based on the A / D data of each sensor, and outputs the calculated angle to the application 27.
[0013]
First, a transfer method of USB communication will be described. At present, USB communication / low-speed device / interrupt transfer is optimal as a communication method. The USB communication is suitable for a sensor device as in the present invention because a plurality of USB connections are easy and a power supply is provided. A low-speed device is a device standard with little data, and is used for data transfer of a keyboard and a mouse. The high-speed device and full-speed device standards are used for printers and scanners having a large amount of data. Interrupt transfer is a transfer method used when data is sent periodically. By selecting these methods, the microcomputer can be reduced in size and cost.
[0014]
However, when the above method is used, the communication cycle is 8 ms from the USB standard, and the amount of data that can be transferred at one time is 8 bytes. If the data to be transferred is within 8 bytes, the data is transmitted every 8 ms. If the data to be transferred is 8 to 16 bytes, the data is transmitted in two parts, such as data 1 for the first 8 ms and data 2 for the next 8 ms. Can be On the other hand, the output of each sensor is converted into digital data by the A / D converter, and the resolution of the A / D converter is 10 bits.
[0015]
FIG. 4 shows a data format in a conventional communication method. Conventionally, the data amount of 9 × 10 = 90 bits (= 12 bytes) was obtained because nine sensor outputs were directly transferred. Accordingly, the communication cycle was 16 ms, and a sufficient communication cycle for smoothing the moving image of the application could not be obtained. Bt1 and Bt2 are button data for sending a reset signal or a signal corresponding to a mouse click. N / A is an unused area and its value is undefined.
[0016]
FIG. 4 shows a data format in the communication method of the present invention. Sensor1 to Sensor3 are gyro outputs (ωx, ωy, ωz). From Sensor4 to Sensor6, the output (Ax, Ay, Az) of the acceleration sensor and the output (Mx, My, Mz) of the magnetic sensor are alternately transferred. Flag is a flag indicating which sensor data is from Sensor4 to Sensor6. For example, Flag is 0 for an acceleration sensor and 1 for a magnetic sensor.
[0017]
The method of calculating the posture angle will be described later. Since the output of the gyro is used to determine the amount of change from the posture angle one cycle before, its responsiveness is required. On the other hand, the output of the acceleration sensor or the magnetic sensor is used to correct the output obtained by the gyro, so that the response is relatively unnecessary. Therefore, it suffices to transfer the data of the acceleration sensor and the magnetic sensor at least alternately at least once. When the number of sensors is small, it is also possible to perform sensor data communication with reduced accuracy by using the margin.
[0018]
Next, FIG. 5 illustrates a method of calculating the posture angle calculated by the posture angle calculation means inside the personal computer. The angular velocity (ωx, ωy, ωz), acceleration (Ax, Ay, Az), and magnetism (Mx, My, Mz) detected by the gyro 52, the acceleration sensor 53, and the magnetic sensor 54 are transferred from the USB. The motion angle computing device 56a computes and outputs motion angles (Δα, Δβ, Δγ), which are attitude angles moved in unit time, from the angular velocities (ωx, ωy, ωz) output from the gyro. The static angle calculation device 56b calculates a static angle (φ, P) that is a temporary attitude angle from the acceleration (Ax, Ay, Az) output from the acceleration sensor and the magnetism (Mx, My, Mz) output from the magnetic sensor. , R) is calculated and output. The determination device 57 compares the motion angle and the stationary angle to determine whether the stationary angle is correct, and outputs a result to the attitude angle detecting device. The attitude angle calculation device 56c calculates the attitude angles (α, β, γ) finally output from the motion angles (Δα, Δβ, Δγ), the stationary angles (φ, P, R) and the output of the discriminating device, Output to the outside.
[0019]
Next, the contents of the motion angle calculation device will be described. The outputs (ωx, ωy, ωz) of the respective gyros according to the angular velocity applied to the attitude angle detection device are subjected to coordinate transformation, and output α (n−1), β (n) one unit time past in unit time to be calculated. -1) and γ (n-1) are converted into the current movement angle (movement angle) (Δα, Δβ, Δγ) in the reference coordinate system as in the following equation.
Δα (n) = ωy · sinγ (n−1) / cosβ (n−1) + ωz · cosγ (n−1) / cosβ (n−1)
Δβ (n) = ωy · cosγ (n−1) −ωz · sinγ (n−1)
Δγ (n) = ωx + ωy · tanβ (n−1) · sinγ (n−1) + ωz · tanβ (n−1) · cosγ (n−1)
[0020]
Next, the static angle calculation device of FIG. 5 will be described. The acceleration sensors 14, 15 and 16 shown in FIG. 1 detect the component component forces Ax (n), Ay (n) and Az (n) of the gravitational acceleration in the sensor coordinate system on the Xs, Ys and Zs axes, respectively. Are located in Further, the magnetic sensors 17, 18 and 19 shown in FIG. 1 are arranged to detect the geomagnetic component forces Mx (n), My (n) and Mz (n) on the Xs, Ys and Zs axes, respectively. .
[0021]
The outputs Ax (n), Ay (n) and Az (n) of the acceleration sensor are inclination angles with respect to the horizontal plane (XY plane) of the reference coordinate system by the roll angle calculation means and the pitch angle calculation means according to the following equation. A temporary roll angle R (n) and a temporary pitch angle P (n) are calculated.
P (n) = sin ^-1 Ax (n)
R (n) = tan ^-1 [-Ay (n) /-Az (n)]
[0022]
In order to determine the provisional yaw angle φ (n) in the reference coordinate system, the geomagnetic components HX and HY in the reference coordinate system are calculated by using the outputs Mx (n), My (n) and Mz (n) of the geomagnetic sensor as the provisional values. Using the pitch angle P (n) and the provisional roll angle R (n), coordinate conversion is performed as in the following equation.
HX (n) = Mx · cosP (n) + [My · sinR (n) + Mz · cosR (n)] · sinP (n)
HY (n) = My · cosR (n) −Mz · sinR (n)
[0023]
The provisional yaw angle φ (n) in the reference coordinate system is
φ (n) = − tan ⁻¹ [HY (n) / HX (n)] − φ (0)
Is represented by Here, φ (0) is the azimuth at the origin.
[0024]
Next, a discriminating device in the posture angle detecting device of the present invention will be described. Since the outputs Ax, Ay, and Az of the acceleration sensor become a composite vector of the Xs, Ys, and Zs axis direction components of the gravitational acceleration and the Xs, Ys, and Zs axis components of the motion acceleration, when there is a motion acceleration, The temporary pitch angle P calculated by the static angle calculation device does not become a correct pitch angle. Also, the provisional yaw angle φ may not be a correct yaw angle depending on the magnetic field environment. The determination device determines whether or not the outputs φ (n), P (n), and R (n) of the static angle calculation device are correct.
[0025]
In the state where no motion acceleration is applied, the combined vector of Ax, Ay and Az is 1 G,
| (Ax ² + Ay ² + Az ² ) ^1/2 −1 | <ε
Holds, φ, P, and R are determined to be correct.
[0026]
Next, a description will be given of a calculation method performed by the attitude angle calculation device that obtains a final output by calculating the output of the motion angle calculation device and the output of the static angle calculation device according to the determination result of the determination device.
If the discriminating device determines that φ, P, and R are correct,
α (n) = α (n−1) + Δα−k [α (n−1) + Δα−φ (n)],
β (n) = β (n−1) + Δβ−k [β (n−1) + Δβ−P (n)],
γ (n) = γ (n−1) + Δγ−k [γ (n−1) + Δγ−R (n)],
When the discriminating apparatus determines that φ, P, and R are incorrect,
α (n) = α (n−1) + Δα,
β (n) = β (n−1) + Δβ,
γ (n) = γ (n−1) + Δγ,
To calculate the posture angle.
[0027]
【The invention's effect】
As described above, according to the present invention, the conventional attitude angle detecting device is obtained by dividing the sensor data into those requiring responsiveness and those unnecessary, and compressing the data to be actually transferred to 8 bytes. A communication algorithm that ensures responsiveness and does not reduce accuracy has been obtained. With this algorithm, an ideal attitude angle detection device was realized.
[Brief description of the drawings]
FIG. 1 is a sensor module of a posture angle detecting device according to the present invention.
FIG. 2 is an explanatory diagram relating to an overall configuration of a posture angle detecting device according to the present invention.
FIG. 3 is an explanatory diagram relating to a conventional USB communication data format.
FIG. 4 is an explanatory diagram relating to a USB communication data format in the present invention.
FIG. 5 is an explanatory diagram relating to a method of calculating a posture angle according to the present invention.
[Explanation of symbols]
11 First gyro 12 Second gyro 13 Third gyro 14 First acceleration sensor 15 Second acceleration sensor 16 Third acceleration sensor 17 First magnetic sensor 18 Second magnetic sensor 19 Third magnetic Sensor 21 Sensor module 22 Gyro 23 Acceleration sensor 24 Magnetic sensor 25 Microcomputer 26 Personal computer 27 Application 28 Attitude angle calculation means 29 USB controller 52 Gyro 53 Acceleration sensor 54 Magnetic sensor 56 Calculation device 56c Posture angle calculation device 57 Discrimination device 59 Output

Claims (1)

A sensor unit including a gyro for detecting angular velocities around three axes, an acceleration sensor for detecting at least two axes of acceleration, and a magnetic sensor for detecting at least two axes of terrestrial magnetism; The sensor unit and the arithmetic unit are posture angle detecting devices that transfer data by remote communication, and are output from the gyro in data communication between the sensor unit and the arithmetic unit. A posture angle detecting device, wherein data is transferred every time, and data output from at least the acceleration sensor and the magnetic sensor are alternately transferred every other time.

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