CN109916362B - Method and system for detecting rotation angle of steering wheel - Google Patents
Method and system for detecting rotation angle of steering wheel Download PDFInfo
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- CN109916362B CN109916362B CN201910160489.1A CN201910160489A CN109916362B CN 109916362 B CN109916362 B CN 109916362B CN 201910160489 A CN201910160489 A CN 201910160489A CN 109916362 B CN109916362 B CN 109916362B
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Abstract
The invention discloses a method and a system for detecting the rotation angle of a steering wheel, wherein the system comprises two units, wherein the first unit is provided with a first singlechip, a first gravity acceleration sensor, a first Bluetooth module, a serial communication module and a power supply module for other users, and the first gravity acceleration sensor, the first Bluetooth module, the serial communication module and the power supply module are connected with the first singlechip through data lines; the second unit is provided with a second single chip microcomputer, a second gravity acceleration sensor, a third gravity acceleration sensor, a second Bluetooth module and a self-powered power supply module, wherein the second gravity acceleration sensor, the third gravity acceleration sensor, the second Bluetooth module and the self-powered power supply module are connected with the second single chip microcomputer through data lines. The method comprises the steps of system initialization, establishment of mathematical relational expression, data output and the like. The invention has the advantages of simple structure, easy installation, clear test method, lower operation requirement on drivers and the like.
Description
Technical Field
The invention relates to the field of driver driving behavior information acquisition, in particular to a method and a system for detecting a steering wheel rotation angle.
Background
With the development of national economy, the vehicle holding amount is increasing year by year, and in order to ensure driving safety and reduce traffic accidents, information detection and related experiments of vehicles become more and more important. At present, in a plurality of detection schemes and experiments such as vehicle driving safety early warning, wheel steering and the like, steering wheel angle data of a vehicle need to be collected, and a microcomputer integrates other information after acquiring the steering wheel angle data and judges driving conditions through analysis. However, many vehicles are not equipped with a steering wheel angle detection sensor, and steering wheel angle data cannot be detected; even if some middle and high-end cars are equipped with the sensor, interfaces such as OBD (on-Board diagnostics) generally do not provide steering wheel angle data; even if the OBD interface provides steering wheel angle data, the communication protocol is very complex, and the steering wheel angle data is difficult to effectively read from the OBD interface; if install vehicular steering wheel angle sensor additional, then with high costs and install very inconvenient, and can influence very much after the installation of the steering wheel angle sensor of non-vehicular drives the impression. The invention provides a method and a device for detecting the steering wheel angle of a vehicle (application publication No. CN 107585210A). The method and the device for detecting the steering wheel angle of the vehicle adopt a vehicle-mounted intelligent terminal MCU and a 3D acceleration sensor thereof, calculate the wheel angle by acquiring parameters of vehicle acceleration, speed and the like in real time, and indirectly detect the steering wheel angle of the vehicle, and have the advantages of troublesome measuring method and complex installation. Therefore, the invention provides a method and a system for detecting the rotation angle of a steering wheel.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: the method and the system for detecting the rotation angle of the steering wheel are provided so as to overcome the defects that the existing steering wheel rotation angle acquisition system is difficult to install, large in size, high in cost, low in accuracy and the like, and the driving is influenced after the existing steering wheel rotation angle acquisition system is installed.
The invention adopts the following technical scheme for solving the technical problems:
the invention provides a detection system for a steering wheel rotation angle, which comprises two units, wherein: the first unit is provided with a first singlechip, a first gravity acceleration sensor, a first Bluetooth module, a serial port communication module and a power supply module for other users, wherein the first gravity acceleration sensor, the first Bluetooth module, the serial port communication module and the power supply module are connected with the first singlechip through data lines; the second unit is provided with a second single chip microcomputer, a second gravity acceleration sensor, a third gravity acceleration sensor, a second Bluetooth module and a self-powered power supply module, wherein the second gravity acceleration sensor, the third gravity acceleration sensor, the second Bluetooth module and the self-powered power supply module are connected with the second single chip microcomputer through data lines.
The power supply is a name corresponding to self-power supply, and means that power is supplied by other devices or equipment.
The first unit is arranged on the vehicle body and is supplied with electric energy by a vehicle-mounted power supply; the first gravity acceleration sensor is arranged on the central shaft of the steering wheel and close to the steering wheel, and a space rectangular coordinate system A which takes the advancing direction of the vehicle as the positive direction of an x axis, takes the downward direction of a vertical vehicle body as the positive direction of a z axis and is orthogonal to the z axis and is in a plane vertical to the vehicle body and accords with the right-hand spiral rule is established.
The second unit is arranged on a steering wheel, is provided with electric energy by a power supply module with a battery, and is arranged on the upper part of a central shaft of the steering wheel when the steering wheel does not rotate, so as to establish a space rectangular coordinate system B1 which is in accordance with a right-hand spiral rule and takes the inward direction of the central shaft of the steering wheel as the positive direction of a z-axis, the positive direction of an axis vertical to the axis of the steering wheel as the positive direction of an x-axis and the orthogonal direction of the y-axis and the x-axis on the plane of the steering wheel; the third gravitational acceleration sensor and the second gravitational acceleration sensor are mutually and vertically arranged at the left part of the central shaft of the steering wheel when the steering wheel is not rotated, and a space rectangular coordinate system B2 which is in accordance with the right-hand spiral rule and takes the axial inner direction in the steering wheel as the positive direction of the z axis, takes the axial positive direction of the vertical steering wheel as the positive direction of the y axis and has the x axis orthogonal to the y axis on the plane of the steering wheel is established; the origins of the space rectangular coordinate systems B1 and B2 coincide with the two gravity acceleration sensors, and the space rectangular coordinate systems B1 and B2 rotate along with the two gravity acceleration sensors and the steering wheel in a fixed connection mode.
The three gravitational acceleration sensors detect the gravitational acceleration and the component numerical value of the motion acceleration of the vehicle on each axis of the sensors, the second single chip microcomputer reads and processes the detection data of the second gravitational acceleration sensor and the third gravitational acceleration sensor, the first single chip microcomputer reads and processes the detection data of the first gravitational acceleration sensor and the receiving data of the first Bluetooth module, the rotating angle of the steering wheel is calculated, data are output through the serial port communication module, and the first single chip microcomputer is in data communication with the second Bluetooth module.
The maximum interval time of the detection data of the gravity acceleration sensor is 2 milliseconds, the time interval for reading the detection data of the gravity acceleration sensor by the single chip microcomputer is freely set between 10 milliseconds and 200 milliseconds by a user, and the single chip microcomputer acquires the detection data of the gravity acceleration sensor according to the time interval set by the user.
The invention provides a method for detecting the rotation angle of a steering wheel, which comprises the following steps:
step1, initializing a system, and establishing spatial rectangular coordinate systems A, B1, B2 and C; the second single chip microcomputer sends synchronous time data to the first single chip microcomputer through the second Bluetooth module, and the single chip microcomputer can process the data at the same time after receiving the detection data of the three gravity acceleration sensors;
step2, when the vehicle is in a static state, the first gravity acceleration sensor detects that the value of the gravity acceleration in the z-axis direction in the space rectangular coordinate system A is a1zDecomposing according to the parallelogram rule to obtain the mathematical relation a1zCalculating an included angle theta between the vehicle and the horizontal road surface, namely the road surface gradient;
step3, when the vehicle is in a static state, a driver operates the steering wheel to slowly rotate clockwise for one circle and then slowly rotate anticlockwise for one circle, the second and third gravitational acceleration sensors detect the acceleration of the vehicle, when the second gravitational acceleration sensor detects the maximum point of the numerical value on the x axis and the third gravitational acceleration sensor detects the maximum point of the numerical value on the y axis, the position is defined as the initial position S of the steering wheel, and the points where the second and third gravitational acceleration sensors are located are respectively the origin o and o';
step4, when the vehicle is running, the vehicle generates total acceleration
The first, second and third gravitational acceleration sensors detect the acceleration of each axis;
step5, the second single chip microcomputer acquires data detected by the second gravitational acceleration sensor and the third gravitational acceleration sensor, data processing is carried out, the acceleration data and the time data are sent to the first single chip microcomputer through the second Bluetooth module, the first single chip microcomputer receives the data through the first Bluetooth module, and the first single chip microcomputer receives the data transmitted by the first gravitational acceleration sensor;
step6, the first single chip computer processes the detection data at the same time according to the time data, and when the steering wheel is positioned at the initial position S, the vehicle acceleration is processed
Decomposed to space rectangular coordinate systemC, the value of a is set to be on each axiscx、acy、acz. When the driver operates the steering wheel to rotate by an angle gamma, the second and third gravity acceleration sensors detect an acceleration value a on the x axis2x'、a3x' acceleration value a is detected on the y-axis2y'、a3y' acceleration value a is detected on the z-axis2z'、a3zIn this case, the second and third gravitational acceleration sensors detect the total acceleration of the vehicle in the respective axes of the spatial rectangular coordinate systems B1 and B2, and can calculate the steering wheel rotation angle γ11、γ12The formula is as follows:
steering wheel steering angle gamma1The calculation formula of (2) is as follows:
the rotation angle gamma of the steering wheel can be solved by using the data measured by the third gravitational acceleration sensor based on the space rectangular coordinate system C21、γ22The formula is as follows:
steering wheel steering angle gamma2The calculation formula of (2) is as follows:
therefore, the steering angle γ of the steering wheel is calculated by the following formula:
step7, after the steering wheel angle is calculated by the first single chip microcomputer, data are filtered, converted into serial data according to the JC communication protocol, and then the data are output through the serial communication module.
In the method, the first single chip microcomputer carries out filtering processing on the steering wheel angle data, and the filtering processing mode is as follows: the first single chip microcomputer randomly obtains and stores steering wheel rotation angle data at five continuous moments, performs curve fitting, predicts steering wheel rotation angle data at the next moment according to curve variation trend, and outputs the steering wheel rotation angle data of curve fitting at the moment.
In the above method, the JC communication protocol specifies: all data is converted into ASCII (American standard code for information interchange) to be sent, each data packet comprises 25 data/characters, and the 1 st bit and the 2 nd bit are data packet headers (JC); the 3 rd to 11 th bits are time bits in the format of "two hours + two minutes + two seconds + three milliseconds"; the 12 th to 13 th bits are direction bits in the format of 'one bit rotation direction bit + one bit whole turn digit', the rotation direction bit is specified to be 0 anticlockwise and 1 clockwise; the 14 th to 18 th bits are the current steering wheel rotation angle number, and the format is three integer numbers + decimal point + one decimal; the 19 th to 20 th bits are check bits, the check rule is that the previous 1 st to 18 th bits are converted into hexadecimal and then summed, and the remainder of dividing the sum by 256 is obtained; the 21 st to 25 th digits are the expected number of degrees of the steering wheel rotation angle, and the format is "three whole degrees + decimal point + one decimal".
Compared with the prior art, the invention has the following main advantages:
(1) the size is small, the structure is simple, the installation is easy, and the driving feeling of a driver is not greatly influenced;
(2) the time interval for the singlechip D1 to acquire data can be set by a user, the time requirement of different users on the data acquisition can be met, the universality is strong, the steering wheel angle measurement of racing driving can be met when the time interval is 20ms, the steering wheel angle measurement of urban road driving of general users can be met when the time interval is 100-200 ms, and the steering wheel angle measurement of low-speed driving can be met when the time interval is 500 ms;
(3) the test method is clear, has low operation requirements on the driver and cannot interfere the driving of the driver;
(4) filtering processing is carried out on output data, effective fitting is carried out, errors of data measurement are reduced, the precision of steering wheel angle data measurement is improved, the errors during online real-time measurement are less than 10%, and the measurement errors after offline secondary processing are less than 5.4%;
(5) when the time interval of the data acquisition of the singlechip D1 is less than 200ms, the predicted error of the steering wheel angle at the next moment is less than 12%.
(6) The steering wheel corner data is output in a serial port data form, the communication protocol is simple, and a user can read and process the data conveniently.
Drawings
Fig. 1 is a schematic diagram of an overall structure of a method and a system for detecting a rotation angle of a steering wheel according to an embodiment of the present invention.
Fig. 2 is an enlarged schematic view of the steering wheel 2 and the second unit 3 in fig. 1.
Fig. 3 is a spatial rectangular coordinate system A, B1, B2, C established by a method and system for detecting a rotation angle of a steering wheel according to an embodiment of the present invention.
Fig. 4 is an enlarged schematic view of the steering wheel 2 and the second unit 3 in fig. 3.
Fig. 5 is a schematic structural diagram of a first unit of a method and a system for detecting a rotation angle of a steering wheel according to an embodiment of the present invention.
Fig. 6 is a schematic circuit diagram of a first unit of a method and a system for detecting a rotation angle of a steering wheel according to an embodiment of the present invention.
Fig. 7 is a schematic structural diagram of a second unit of the method and system for detecting a rotation angle of a steering wheel according to the embodiment of the present invention.
Fig. 8 is a schematic circuit diagram of a second unit of a method and a system for detecting a rotation angle of a steering wheel according to an embodiment of the present invention.
In the figure: 1. the automobile steering wheel comprises a steering wheel center shaft, 2 a steering wheel, 3 a second unit, 4 a first unit, 5 a vehicle body, 6 a gravity acceleration sensor J1, 7 a gravity acceleration sensor J2, 8 a gravity acceleration sensor J3.
Detailed Description
The invention relates to a method and a system for detecting a rotation angle of a steering wheel. The purpose is to provide a novel detection method and system for the steering wheel rotation angle, which are small in size and high in accuracy. The steps for realizing the detection of the steering wheel angle data are as follows: two units are installed to realize system initialization, the gravity acceleration sensor detects acceleration components in real time, and the single chip microcomputer reads and processes data and then outputs the data. The invention can reduce the size of the steering wheel corner sensor, improve the measurement accuracy, has simple operation, can automatically set the data acquisition period based on the user requirement and has strong universality.
The present invention will be further described with reference to the following examples and drawings, but the present invention is not limited thereto.
The invention provides a detection system for a steering wheel rotation angle, which comprises a first unit 4 and a second unit 3, as shown in figures 1-4. The first unit is shown in fig. 5, and comprises a single chip microcomputer D1, a J1 (gravity acceleration sensor 6) connected with the single chip microcomputer through a data line, a bluetooth module L1, a serial communication module, and a power supply module C1. The second unit is shown in fig. 7, and includes a single chip microcomputer D2, a J2 (gravity acceleration sensor 7), a J3 (gravity acceleration sensor 8), a bluetooth module L2, and a self-powered power module C2.
The gravity acceleration sensors are 3 in type GY-291, 5v in power supply and TTL serial TTL communication protocol in communication mode, and are used for detecting the components of the total acceleration of the vehicle on each axis in real time.
The single chip microcomputer selects 2 single chip microcomputers with models of C8052F580DK and 5v of power supply, the single chip microcomputer D1 is used for reading and processing detection data of the gravity acceleration sensor J1 and receiving data of the Bluetooth module L1, the rotating angle of the steering wheel is calculated, data are output through the serial port communication module, and the single chip microcomputer D2 is used for reading and processing detection data of the gravity acceleration sensor J2 and the gravity acceleration sensor J3.
The Bluetooth modules are 2 in HC-06 model and 5v power supply, and are used for sending and receiving the processing data of the single chip microcomputer.
The serial communication module is a serial communication module with the model number TELESKY, the CP2102 kernel chip and the power supply of 5v, and is used for sending serial data by the singlechip D1.
The power module C1 directly gets electricity from the vehicle-mounted power supply, and the power module C2 selects a power module with the model of LRS-50-24 and the voltage of 5v and is used for supplying power for the second unit.
The specific circuit of the first unit is shown in fig. 6, and includes four parts, where: 2 ends and 3 ends of the gravity acceleration sensor J1 are connected with P0.4 and P0.5 ports of the singlechip D1, 1 port of the gravity acceleration sensor J1 is connected with the positive end of the power supply, and 4 ports of the gravity acceleration sensor J1 are grounded. The 2 ends and the 3 ends of the Bluetooth module L1 are connected with the P1.3 and the P1.2 ports of the singlechip D1, the 1 port of the Bluetooth module L1 is connected with the positive end of the power supply, and the 4 ports of the Bluetooth module L1 are grounded. The 2 end and the 3 end of the serial communication module are connected with the P1.7 port and the P1.6 port of the singlechip D1, the 1 port of the serial communication module is connected with the positive end of the power supply, and the 4 port of the serial communication module is grounded. The VCC end of the singlechip D1 is connected with the positive end of the power supply, and the GND end is grounded. The ports 1 and 2 of the power supply module C1 are connected with a vehicle-mounted power supply, and the positive terminal port of the power supply module C1 is connected with the 5V terminal of each sensor.
The specific circuit of the second unit is shown in fig. 8, and includes five parts, where: 2 ends and 3 ends of the gravity acceleration sensor J2 are connected with P0.4 and P0.5 ports of the singlechip D1, a 1 port of the gravity acceleration sensor J2 is connected with the positive end of the power supply, and a 4 port of the gravity acceleration sensor J2 is grounded; 2 ends and 3 ends of the gravity acceleration sensor J3 are connected with P1.3 and P1.2 ports of the singlechip D1, 1 port of the gravity acceleration sensor J3 is connected with the positive end of the power supply, and 4 ports of the gravity acceleration sensor J3 are grounded. The 2 ends and the 3 ends of the Bluetooth module L1 are connected with the P1.7 and the P1.6 ports of the singlechip D1, the 1 port of the Bluetooth module L2 is connected with the positive end of the power supply, and the 4 port of the Bluetooth module L2 is grounded. The VCC end of the singlechip D2 is connected with the positive end of the power supply, and the GND end is grounded. The 2 port of the power supply module C2 is connected with the positive electrode of the battery, and the 1 port of the power supply module C2 is connected with the negative electrode of the power supply.
The invention provides a detection system for the rotation angle of a steering wheel, which comprises the following working processes:
(1) the first unit is arranged on the vehicle body and is supplied with electric energy by a vehicle-mounted power supply. The second unit is fixed to the steering wheel 2 by plastic. After the two units are installed, the system is initialized, the clock synchronization of the two single-chip microcomputers is realized, a corresponding coordinate system is established, and a driver operates a steering wheel to determine the initial position:
(2) the gravity acceleration sensor detects the components of the total acceleration of the vehicle on each axis and transmits the acquired data to the single-chip microcomputers D1 and D2;
(3) the singlechip D2 reads the detection data of the gravity acceleration sensors J2 and J3, and the detection data are transmitted to the singlechip D1 through the Bluetooth device L2 after being processed; the singlechip D1 reads data of the singlechip D2 and the gravity acceleration sensor J1, and the data are transmitted in a serial port mode after being filtered.
The invention provides a method for detecting the rotation angle of a steering wheel, which specifically comprises the following steps:
firstly, two units are installed, the initialization of the system is realized, and a corresponding space rectangular coordinate system is established.
Firstly, the singlechip D2 sends synchronous time data to the singlechip D1 through the Bluetooth module L2, and the singlechips D1 and D2 can process data at the same time after receiving detection data of the gravity acceleration sensors J1, J2 and J3;
secondly, as shown in figures 3-4 and 6, the first unit is arranged on the vehicle body and is supplied with electric energy by a vehicle-mounted power supply. The first gravity acceleration sensor J1 is positioned on the vehicle body and close to the steering wheel, and a space rectangular coordinate system A which takes the vehicle advancing direction as the positive direction of an x axis, takes the vertical vehicle body downward as the positive direction of a z axis and is orthogonal to the z axis and is in the plane of the vertical vehicle body and accords with the right-hand spiral rule is established;
thirdly, as shown in fig. 5 and 7, the second unit is fixedly installed on the steering wheel by plastic, the power module C2 provides power, the gravity acceleration sensor J2 is installed on the upper portion of the central axis of the steering wheel when the steering wheel is not rotated, and a spatial rectangular coordinate system B1 which is in accordance with the right-hand screw rule and takes the central axis of the steering wheel inward as the positive direction of the z axis, the axial line of the vertical steering wheel upward as the positive direction of the x axis, and the y axis and the x axis are orthogonal on the plane of the steering wheel is established; the gravity acceleration sensor J3 and the gravity acceleration sensor J2 are mutually vertically arranged at the left part of the central shaft of the steering wheel when the steering wheel does not rotate, and a space rectangular coordinate system B2 which is in accordance with the right-hand spiral rule and takes the axial direction in the steering wheel as the positive direction of a z axis, the axial direction of a vertical steering wheel as the positive direction of a y axis and the orthogonal direction of the x axis and the y axis on the plane of the steering wheel is established; the origins of the space rectangular coordinate systems B1 and B2 are superposed with the acceleration sensors J2 and J3 and rotate along with the fixed connection between the acceleration sensors J2 and J3 and the steering wheel;
establishing a space rectangular coordinate system C which is in accordance with a right-hand spiral rule and takes the axial inner direction in the steering wheel as the positive direction of a z axis, the axial positive direction vertical to the steering wheel as the positive direction of an x axis and the y axis and the x axis are orthogonal on the plane of the steering wheel, wherein the space rectangular coordinate system C does not rotate and is used as a reference standard of space rectangular coordinate systems B1 and B2; the space rectangular coordinate system C is equivalent to the space rectangular coordinate system A rotating the transverse included angle alpha (alpha is more than 0 and less than 90 degrees) between the plane of the steering wheel and the vehicle body around the y axis anticlockwise (from the positive direction of the y axis to the negative direction).
Further, when the vehicle is in a stationary state, the gravitational acceleration sensor J1 detects that the value of the gravitational acceleration in the x, y, z-axis directions in the spatial rectangular coordinate system a is a1x、a1y、a1zThe gravity acceleration g can be decomposed according to the x and z axes of the parallelogram normal space rectangular coordinate system A to obtain a mathematical relation formula
The included angle theta between the vehicle and the horizontal road surface, namely the road surface gradient, can be calculated by the formula
Further, when the vehicle is in a stationary state, the driver operates the steering wheel to rotate clockwise and counterclockwise slowly for one turn, the gravity acceleration sensors J2 and J3 detect the acceleration of the vehicle, when the gravity acceleration sensor J2 detects the maximum point of the value on the x axis and the gravity acceleration sensor J3 detects the maximum point of the value on the y axis, the positions are defined as the initial position S of the steering wheel, and the points where the gravity acceleration sensors J2 and J3 are located are the original points o and o', respectively.
When the steering wheel is at the initial position S, the acceleration sensors J2, J3 detect a value a on the x, y, and z axes, respectively2xAnd a3x、a2yAnd a3y、a2zAnd a3zAnd satisfies the following conditions:
a2z＝a3z，
because the directions of the gravity acceleration are vertical and downward, the gravity acceleration g can be decomposed according to the x and z axes of a parallelogram normal space rectangular coordinate system A, and a mathematical relation can be obtained:
the angle alpha between the steering wheel plane and the transverse direction of the vehicle body can be formed by
And (6) obtaining.
Further, when the vehicle is running, the vehicle generates a total acceleration
The acceleration of each axis is detected by the gravity acceleration sensors J1, J2 and J3, the maximum interval time of data detection of the gravity acceleration sensors J1, J2 and J3 is 2 milliseconds, and the time interval of data detection of the gravity acceleration sensors J1, J2 and J3 read by the single-chip microcomputers D1 and D2 can be from 10 milliseconds to 10 milliseconds by a userThe time interval is freely set between 200 milliseconds, and the single-chip microcomputers D1 and D2 acquire detection data of the gravity acceleration sensors J1, J2 and J3 according to the time interval set by a user.
Further, singlechip D2 obtains the data that gravity acceleration sensor J2, J3 detected, carries out data processing, sends acceleration data and time data to singlechip D1 through bluetooth module L2, and singlechip D1 receives data through bluetooth module L1, and singlechip D1 receives the data of gravity acceleration sensor J1 conveying simultaneously.
Further, the single chip microcomputer D1 processes the detection data at the same time according to the time data, and when the steering wheel is located at the initial position S, the vehicle acceleration is detected
Decomposing the data into each axis of a space rectangular coordinate system C, and setting the value of each axis as acx、acy、aczThe calculation formula is
When the driver operates the steering wheel to rotate by an angle gamma, the acceleration sensors J2, J3 detect an acceleration value a on the x-axis2x'、a3x' acceleration value a is detected on the y-axis2y'、a3y' acceleration value a is detected on the z-axis2z'、a3zAt this time, the acceleration sensors J2 and J3 detect the values of the acceleration of the entire vehicle after the axes are decomposed in the spatial rectangular coordinate systems B1 and B2, and the data measured by the acceleration sensor J2 satisfies the condition that the spatial rectangular coordinate system C is used as a reference
The simultaneous equations (1), (2) can be obtained:
the steering wheel rotation angle γ is solved from the first equation of the equation set (3)11The formula is as follows:
the second equation of the equation set (3) is used to solve for the steering wheel rotation angle γ12The formula is as follows:
steering wheel steering angle gamma1The calculation formula of (2) is as follows:
based on the rectangular space coordinate system C, the data measured by the acceleration sensor J3 satisfy the following conditions:
the simultaneous equations (1), (4) can be obtained:
the steering wheel rotation angle γ is solved from the first equation of the system of equations (5)21The formula is as follows:
the second equation of the system of equations (5) solves for the steering wheel rotation angle γ22The formula is as follows:
steering wheel steering angle gamma2The calculation formula of (2) is as follows:
therefore, the steering angle γ of the steering wheel is calculated by the following formula:
when the singlechip D1 calculates to obtain gamma11-γ12|≥2°、|γ21-γ22|≥2°、|γ1-γ2When | ≧ 2 °, the single-chip microcomputer D1 does not output a data packet, prompting an error in result.
Further, after the single chip microcomputer D1 calculates the steering wheel angle, the acceleration may fluctuate in a sawtooth shape due to vehicle vibration and other reasons, and therefore, the data needs to be filtered, and the filtering method is as follows: the single chip microcomputer D1 randomly acquires and stores steering wheel rotation angle data at five continuous moments, performs curve fitting, predicts the next steering wheel rotation angle data according to the curve variation trend, and outputs the steering wheel rotation angle data of the curve fitting at the moment;
for data transmission, the single chip microcomputer D1 firstly converts steering wheel corner data into serial port data according to a JC communication protocol, wherein the JC communication protocol specifies: all data is converted into ASCII (American standard code for information interchange) to be sent, each data packet comprises 25 data/characters, and the 1 st bit and the 2 nd bit are data packet headers (JC); the 3 rd to 11 th bits are time bits in the format of "two hours + two minutes + two seconds + three milliseconds"; the 12 th to 13 th bits are direction bits in the format of 'one bit rotation direction bit + one bit whole turn digit', the rotation direction bit is specified to be 0 anticlockwise and 1 clockwise; the 14 th to 18 th bits are the current steering wheel rotation angle number, and the format is three integer numbers + decimal point + one decimal; the 19 th to 20 th bits are check bits, the check rule is that the previous 1 st to 18 th bits are converted into hexadecimal and then summed, and the remainder of dividing the sum by 256 is obtained; the 21 st to 25 th bits are the predicted steering wheel rotation angle number, and the format is three integer number + decimal point + one decimal; the singlechip D1 outputs the data packet, 8 data bits, 1 stop bit and no parity check in the time period through the serial port communication module, and the Baud rate range is 9600 bps-115200 bps.
While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (7)
1. A method for detecting the rotation angle of a steering wheel is characterized by comprising the following steps:
step1, initializing a system, and establishing spatial rectangular coordinate systems A, B1, B2 and C; the second single chip microcomputer sends synchronous time data to the first single chip microcomputer through the second Bluetooth module, the second single chip microcomputer can receive detection data of the second gravity acceleration sensor and the third gravity acceleration sensor, and the first single chip microcomputer can process data according to the same time after receiving the detection data of the first gravity acceleration sensor;
the first gravity acceleration sensor is positioned on the vehicle body and close to a steering wheel, and a space rectangular coordinate system A which takes the forward direction of the vehicle as the positive direction of an x axis, takes the downward direction of a vertical vehicle body as the positive direction of a z axis and is orthogonal to the z axis and is in a plane vertical to the vehicle body and accords with a right-hand spiral rule is established;
the second gravity acceleration sensor is arranged at the upper part of the central shaft of the steering wheel when the steering wheel does not rotate, and a space rectangular coordinate system B1 which is in accordance with the right-hand spiral rule and takes the inward direction of the central shaft of the steering wheel as the positive direction of the z axis, takes the positive direction of the vertical axis of the steering wheel as the positive direction of the x axis and takes the y axis and the x axis orthogonal to each other on the plane of the steering wheel is established; a third gravitational acceleration sensor and a second gravitational acceleration sensor are vertically arranged at the left part of the central shaft of the steering wheel when the steering wheel is not rotated, and a space rectangular coordinate system B2 which is in accordance with the right-hand spiral rule and takes the inward central shaft of the steering wheel as the positive direction of the z axis, takes the positive direction of the vertical axis of the steering wheel as the positive direction of the y axis and has the x axis orthogonal to the y axis on the plane of the steering wheel is established; the origin points of the space rectangular coordinate systems B1 and B2 are superposed with the two gravity acceleration sensors and rotate along with the fixed connection of the two gravity acceleration sensors and the steering wheel;
establishing a space rectangular coordinate system C which is in accordance with a right-hand spiral rule and takes the inward direction of a central axis of a steering wheel as the positive direction of a z axis, the positive direction of an axis of a vertical steering wheel as the positive direction of an x axis and the y axis and the x axis are orthogonal on the plane of the steering wheel;
step2, when the vehicle is in a static state, the first gravity acceleration sensor detects that the value of the gravity acceleration in the z-axis direction in the space rectangular coordinate system A is a1zDecomposing according to the parallelogram rule to obtain the mathematical relation a1zCalculating an included angle theta between the vehicle and the horizontal road surface, namely the road surface gradient;
step3, when the vehicle is in a static state, a driver operates the steering wheel to slowly rotate clockwise for one circle and then slowly rotate anticlockwise for one circle, the second and third gravitational acceleration sensors detect the acceleration of the vehicle, when the second gravitational acceleration sensor detects the maximum point of the numerical value on the x axis and the third gravitational acceleration sensor detects the maximum point of the numerical value on the y axis, the position is defined as the initial position S of the steering wheel, and the points where the second and third gravitational acceleration sensors are located are respectively the origin o and o';
step4, when the vehicle is running, the vehicle generates total acceleration
The first, second and third gravitational acceleration sensors detect the acceleration of each axis;
step5, the second single chip microcomputer acquires data detected by the second gravitational acceleration sensor and the third gravitational acceleration sensor, data processing is carried out, the acceleration data and the time data are sent to the first single chip microcomputer through the second Bluetooth module, the first single chip microcomputer receives the data through the first Bluetooth module, and the first single chip microcomputer receives the data transmitted by the first gravitational acceleration sensor;
Step6、the first single chip microcomputer processes the detection data at the same moment according to the time data, and when the steering wheel is located at the initial position S, the vehicle acceleration is detected
Decomposing the data into each axis of a space rectangular coordinate system C, and setting the value of each axis as acx、acy、acz(ii) a When the driver operates the steering wheel to rotate by an angle gamma, the second and third gravity acceleration sensors detect an acceleration value a on the x axis2x'、a3x' acceleration value a is detected on the y-axis2y'、a3y' acceleration value a is detected on the z-axis2z'、a3zIn this case, the second and third gravitational acceleration sensors detect the total acceleration of the vehicle in the respective axes of the spatial rectangular coordinate systems B1 and B2, and can calculate the steering wheel rotation angle γ11、γ12The formula is as follows:
in the formula: a is1xDetecting a value of the acceleration in the x-axis direction in a space rectangular coordinate system A for the first gravity acceleration sensor; a is1yDetecting a value of the acceleration in the y-axis direction in a space rectangular coordinate system A for the first gravity acceleration sensor;
steering wheel steering angle gamma1The calculation formula of (2) is as follows:
taking a space rectangular coordinate system C as a reference, and using a third gravitational acceleration sensorThe measured data can be used to solve for the steering wheel rotation angle gamma21、γ22The formula is as follows:
steering wheel steering angle gamma2The calculation formula of (2) is as follows:
therefore, the steering angle γ of the steering wheel is calculated by the following formula:
step7, after the steering wheel angle is calculated by the first single chip microcomputer, data are filtered, converted into serial data according to the JC communication protocol, and then the data are output through the serial communication module.
2. The method for detecting the steering wheel rotation angle according to claim 1, wherein the first single chip microcomputer performs filtering processing on the steering wheel rotation angle data in a manner that: the first single chip microcomputer randomly obtains and stores steering wheel rotation angle data at five continuous moments, performs curve fitting, predicts steering wheel rotation angle data at the next moment according to curve variation trend, and outputs the steering wheel rotation angle data of curve fitting at the moment.
3. The method of claim 1, wherein the JC communication protocol specifies: all data is converted into ASCII (American standard code for information interchange) to be sent, each data packet comprises 25 data/characters, and the 1 st bit and the 2 nd bit are data packet headers (JC); the 3 rd to 11 th bits are time bits in the format of "two hours + two minutes + two seconds + three milliseconds"; the 12 th to 13 th bits are direction bits in the format of 'one bit rotation direction bit + one bit whole turn digit', the rotation direction bit is specified to be 0 anticlockwise and 1 clockwise; the 14 th to 18 th bits are the current steering wheel rotation angle number, and the format is three integer numbers + decimal point + one decimal; the 19 th to 20 th bits are check bits, the check rule is that the previous 1 st to 18 th bits are converted into hexadecimal and then summed, and the remainder of dividing the sum by 256 is obtained; the 21 st to 25 th digits are the expected number of degrees of the steering wheel rotation angle, and the format is "three whole degrees + decimal point + one decimal".
4. The method for detecting the rotation angle of the steering wheel according to claim 1, wherein a first unit is formed by a first single chip microcomputer, a first gravitational acceleration sensor, a first Bluetooth module, a serial communication module and an electricity-taking power supply module which are connected with the first single chip microcomputer through data lines; the second unit is composed of a second singlechip, a second gravity acceleration sensor, a third gravity acceleration sensor, a second Bluetooth module and a self-powered power module which are connected with the second singlechip through data lines.
5. The method for detecting a rotation angle of a steering wheel according to claim 4, wherein the first unit is mounted on a vehicle body and is powered by a vehicle-mounted power supply.
6. The method for detecting the rotation angle of the steering wheel according to claim 4, wherein the second unit is mounted on the steering wheel and is powered by a power module with a battery.
7. The method for detecting the rotation angle of the steering wheel according to claim 1, wherein the maximum interval time of the detection data of the acceleration sensor is 2 milliseconds, the time interval for reading the detection data of the acceleration sensor is freely set by a user between 10 milliseconds and 200 milliseconds, and the single chip acquires the detection data of the acceleration sensor according to the time interval set by the user.
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