TWI404932B - Nuclear control module for tri-axis accelerometer - Google Patents

Abstract

The present invention relates to a nuclear control module for a tri-axis accelerometer, which comprises an accelerator, a transmission interface, a single chip controller and a display; wherein the single chip controller is provided with a low-pass digital filter and a vector algorithm unit. As a result, the linear acceleration values captured by the accelerator can be transmitted to the single chip controller via the transmission interface, and a low-pass digital filter inside the single chip controller can be used to filter out the undesired situations of drift jumping resulted from the drift errors at the time when the accelerator captures data. At last the vector algorithm unit may use the tri-axis vector components to do analysis and further determine the angular values, which can be outputted to and shown on the display.

Description

Core control module for three-axis accelerometer

The invention relates to a core control module of a three-axis accelerometer, in particular to a structural innovation design of a core control module of a three-axis accelerometer with more accurate and stable sensing results and fast response time.

According to the survey, the three-axis accelerometers currently seen on the market are often used for rotation and angle detection. However, the acceleration sensing components used in the market usually correspond to the acceleration values with non-linear values, so angular errors often occur; in addition, the existing accelerations Although the state can be judged in the application, there is no indication accuracy.

Please refer to the new patent case of "Model-type motion measuring device with three-axis accelerometer" in China No. M332833. This patent is to sense the movement of the hand in a first axial direction. The motion signals generated by the two axial directions and the third axial direction are transmitted to the microprocessor, and the microprocessor then processes the received motion signals into motion information of the athletes, and the display unit is used to display the micro processing. The motion information processed by the device.

However, the measuring device can only determine the direction in actual implementation, and cannot make the angle measurement, so the measurement result is more easily distorted and inaccurate.

Now, the present inventors have developed a design for a three-axis accelerometer that is more accurate, stable, and has a fast response time in view of the lack of accelerometers as described above. The core control module, which in turn improves the lack of prior art, is the primary purpose of the present invention.

In order to achieve the above-mentioned main purpose, the present invention provides a core control module of a three-axis accelerometer; the core control module of the three-axis accelerometer comprises an accelerometer, a transmission interface, a single-chip controller and a display; Wherein the single-wafer controller has a low-pass digital filter and a vector calculation unit; accordingly, the accelerometer is used to transmit the linear acceleration value obtained by the acceleration to the single-chip controller through the transmission interface, and the single-chip controller The internal low-pass digital filter filters out the drift of the accelerometer caused by the drift error when the data is captured, and then the vector calculation unit analyzes the numerical component of the triaxial direction vector to determine the angle value, and This angle value is output to the display.

(1)‧‧‧ Accelerator

(11)‧‧‧Variable Capacitance

(111)‧‧‧ electrodes

(112)‧‧‧ electrodes

(2) ‧‧‧Transport interface

(3) ‧‧‧Single chip controller

(31)‧‧‧Low-pass digital filter

(32)‧‧‧Vector calculation unit

(4) ‧ ‧ display

First: Schematic block diagram of the core control module of the three-axis accelerometer of the present invention

Second: Schematic diagram of low-pass digital filter overlay sampling

Figure 3: Accelerometer architecture diagram

For a more complete and clear disclosure of the technical means, the object of the invention and the effect of the present invention, the following detailed description, and the accompanying drawings,

Please refer to the first figure, which shows the core of the triaxial accelerometer of the present invention. Schematic diagram of the architecture of the heart control module. The core control module of the three-axis accelerometer of the present invention comprises: an accelerometer (1), a transmission interface (2), a single chip controller (3) and a display (4); wherein the single chip control The device (3) further includes a low-pass digital filter (31) and a vector calculation unit (32).

Accordingly, the linear acceleration value obtained by the accelerometer (1) is transmitted to the single-chip controller (3) through the transmission interface (2), and the single-chip controller (3) is borrowed from the internal low-pass The digital filter (31) filters out the drift of the accelerometer (1) due to the drift error when grabbing the data, and then the vector calculation unit (32) analyzes the numerical component of the triaxial direction vector to determine the angle value. And output the angle value to the display (4) display.

The single-wafer controller (3) sets the acceleration speed of the accelerometer (1) to 100 or 400 Hz via the transmission interface (2). In the present embodiment, the sampling speed of 400 Hz is used to capture the three axes (X, Y, Z). The data command captures an acceleration data of 2.5m (Sec). Since the accelerometer (1) has drift error, the drift jitter condition is filtered out by the low-pass digital filter (31) after the data is captured. The low-pass digital position The filter works as shown in the second figure. It adds the first to the 50th as an average. When the 51st data comes in, the second to the 51th data are accumulated for averaging, and so on. This method can be calculated for each stroke. This is called The iteration method. In general, the average method is averaged from the first to the 50th data, and the 51st to the 100th data are averaged. This method has two disadvantages: (1) Although there is an average action, the time interval is required. 50 strokes are calculated, so the sampling speed is reduced; (2) each acceleration is fixed without moving The value is still slightly different from the 3~5 numerical error, so the value of the LCD display will see that the value has 2~3 jitter instability. However, the low-pass digital filtering method adopted by the present invention can react faster in the case of rapid change of motion, and the numerical value can be displayed without jumping at every 1 degree scale.

The structure of the accelerometer (1) is as shown in the third figure. The principle of determining the angle is: using two electrodes (111) and (112) of the variable capacitor (11), one for the fixed electrode (111), and the other One block is a movable electrode (112), and a mass is attached to the movable electrode (112). When an external force generates an acceleration, the mass is displaced by the inertia, thereby changing the fixed electrode (111) and the movable electrode (112). The distance between the two electrodes (111) and (112) changes, and the capacitance value also changes, and the acceleration value is obtained through the capacitance value measuring circuit and the amplifying circuit.

The transmission interface (2) of the present invention adopts a Serial Peripheral Interface (SPI), and the accelerometer (1) uses a three-axis accelerometer of ST company model LIS302DL as a sensing element; the LIS302DL three-axis direction The internal calculation of the accelerometer is transmitted to the single-chip controller (3) with a linear acceleration value of 18 mg at 1 LSB. The single-chip controller (3) uses Microchip's 16-bit digital signal single-chip dsPIC30F4011 as the control core.

The core control module of the three-axis accelerometer of the present invention captures the three-axis acceleration data in an iterative manner through the accelerometer (1), and transmits the captured linear acceleration value to the single-chip controller (3), and then The low-pass digital filter (31) inside the single-chip controller (3) filters out the drift jitter, and uses the vector calculation unit (32) to determine the angle value by the three-axis direction vector component. Compared with the protractor, the error value is within 0.5 degrees, and its overall entity has been reduced, which is convenient to carry.

The above is only a part of the embodiments of the present invention, and is not intended to limit the present invention. It is intended to be included in the scope of the present invention.

In summary, the embodiments of the present invention can achieve the expected use efficiency, and the specific structure disclosed therein has not been seen in similar products, nor has it been disclosed before the application, and has completely complied with the provisions of the Patent Law. And the request, the application for the invention of a patent in accordance with the law, please forgive the review, and grant the patent, it is really sensible.

(1)‧‧‧ Accelerator

(2) ‧‧‧Transport interface

(3) ‧‧‧Single chip controller

(31)‧‧‧Low-pass digital filter

(32)‧‧‧Vector calculation unit

(4) ‧ ‧ display

Claims (5)

A core control module for a three-axis accelerometer includes: an accelerometer, a transmission interface, a single-chip controller, and a display; wherein the accelerometer uses two electrodes of a variable capacitor, one of which is a fixed electrode The other piece is a movable electrode, and the movable electrode is attached with a mass. When an external force generates acceleration and acts on the mass, the distance between the fixed electrode and the movable electrode is changed, and the capacitance value thereof is also changed, and thereby the Acceleration value; the accelerometer uses two electrodes of variable capacitance, one is a fixed electrode, the other is a movable electrode, and the movable electrode is provided with a mass. When an external force generates acceleration and acts on the mass, the fixed electrode is changed. The distance between the movable electrodes and the capacitance value thereof will also change, and the acceleration value thereof will be known; the accelerometer transmits the captured linear acceleration value to the single chip controller through the transmission interface, the single chip controller A low-pass digital filter and a vector calculation unit are provided therein, and the low-pass digital filter is used to filter out the accelerometer. The beating of the drift, and then by the vector arithmetic unit vector components in three axial directions, the angle values determined, and this value is output to the display to display an angle. For example, the core control module of the three-axis accelerometer described in claim 1 of the patent scope, wherein the low-pass digital filter filters out the drifting behavior is adopted in an iterative manner. The core control module of the three-axis accelerometer according to claim 1, wherein the accelerometer sets the sampling speed to be 100 or 400 Hz. For example, the core control module of the three-axis accelerometer described in claim 1, 2 or 3, wherein the transmission interface uses a sequence peripheral interface. The core control module of the three-axis accelerometer as described in claim 1, 2 or 3 Wherein the transmission interface uses a sequence peripheral interface.