Vehicle positioning system based on sound and light detection
Since the infrared array is formed by connecting N functionally identical infrared modules in series, in the production process, 5 to 10 modules are used to form a circuit board assembly, and the plug-in mounting structure is adopted, and the components of the components are the same and can be replaced with each other. Arbitrary series connection can meet the requirements of different working area lengths and minimize the time required to replace faulty modules in the field.
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When installing on site, segmentation calibration is required to avoid accumulation of errors.
2.3 Scanning intensity processing
In heavy fog or heavy rainfall, the infrared penetrating ability is reduced, which reduces the reliability of infrared scanning, and is usually solved by increasing the infrared emission power. To this end, infrared scanning sets three scan intensity modes: normal, enhanced, and super strong. In normal mode infrared scanning, infrared transceiver is â€œone-to-oneâ€ operation, and only one infrared module transmits, one bit at a time; enhanced mode infrared scanning, infrared transceiver becomes â€œone-twoâ€ work, and there are 2 An adjacent infrared module transmits one bit at a time; in the super mode infrared scanning, the infrared transceiver becomes a "one to three" operation, and three adjacent infrared modules are emitted. Obviously, the infrared emission power of the latter two modes is 2 times and 3 times that of the first mode, respectively. The positioning accuracy of the latter two scanning modes will be reduced, but the maximum does not exceed 2 â–³ L.
2.4 infrared anti-interference treatment
Since the positioning device works in an outdoor field, anti-interference measures against background infrared rays such as sunlight should be considered in the circuit design. Specifically, three measures were taken:
(1) Close the receiver. Place the receiving head in the windowed cabinet to avoid direct sunlight.
(2) Dynamic infrared emission. The background infrared rays such as daylight generally do not fluctuate greatly. Therefore, the infrared ray is pulse-modulated, and the dynamic infrared ray emission effect is better.
(3) Select anti-interference receiver. The circuit uses anti-interference to directly detect infrared signals in direct sunlight and infrared interference. In order to achieve the optimal operating point of the SBXl6i0-02 receiving head, the frequency of the oscillating signal generated by the pulse generator should be between (38 Â± 0.5) kHz.
2.5 Large-span electronic shift circuit switching signal loss processing
The electronic shift circuit is usually composed of about 100 pieces of 74LSl64 series, and the circuit length is up to several 10 m. Due to the influence of the distribution parameters, the shift clock signal CLK of each piece of 74LSl64 is not synchronized, which easily leads to the switching signal during the shifting process. Lost, making the scan "halfway." To this end, the shift clock signal CLK of each piece of 74LSl64 should be driven in parallel, and ensure that the clock signals of each piece of 74LSl64 are on the same drive stage, while minimizing the circuit impedance and increasing the power of the drive circuit.
3 Ranging system circuit design and debugging
Figure 3 shows the ranging system circuit. The circuit consists of a single-chip microcomputer and four sets of ultrasonic transceiver units. Only one set of ultrasonic transceiver units is shown in the figure. The transmitter unit consists of a 40 kHz oscillator and gate. The gate circuit produces a low frequency pulse signal with a small duty cycle with a pulse duration of 160 it and a pulse interval of 30 to 50 ms (adjusted as needed). This pulse signal is used as a set pulse of the oscillator; the other is sent to the microcontroller as the start pulse of the timer. During set, the oscillator outputs a modulated pulse signal at a frequency of 40 kHz, which is transmitted by the ultrasonic transmitter T40-16. The echo receiving adopts the universal FPS409I infrared receiving component, but only needs to change the infrared receiving tube PH302 to the ultrasonic receiving head R40-16, so that in the effective ranging range, the output of the received signal can be guaranteed to reach the TTL level. The received signal is shaped and amplified and sent to the microcontroller as a stop pulse of the timer. The single chip calculates the time t between the start pulse and the stop pulse, and finds the distance s according to the equation (1).
Figure 3 Ranging system circuit
The ranging system adopts the â€œone for fourâ€ structure. In order to avoid mutual interference of multiple sets of ultrasonic units, they should work under the control of the single-chip microcomputer. The pulse interval in this circuit is 30 to 50 ms, and the corresponding ranging range is about 5 to 15 m. If the ranging range is increased, the pulse interval needs to be increased. In addition, the distance measuring circuit has a blind spot of about 30 cm, and the distance between the distance measuring device and the measuring object should be more than 30 cm. At the same time, when the single chip microcomputer counts the start and stop pulses, it also avoids the interference of the false stop pulse in the blind zone. .
4 control software design
The control software includes host software and single-chip software. The main software flow is shown in Figure 4. The single chip microcomputer 1 generates a switching signal and a shift clock required for the infrared electronic shift progressive scan circuit, and collects the receiving state data once every shift clock cycle, and uploads the data to the host after completing one scan; Change the scanning speed and scanning intensity by program control. The single-chip microcomputer 2 controls and detects four ultrasonic devices respectively, and the calculated time is simply processed and then uploaded to the host. Because there is a blind zone, to avoid the interference of the false stop pulse coming from this interval, the delay open interrupt is used, that is, after the start pulse starts the timer, wait for the blind zone to open the interrupt again, so that the MCU interrupt port receives the actual effective stop. The pulse stops the timer. The host program takes the active query mode to read the longitudinal detection data and the horizontal detection data from the two single-chip microcomputers, and then processes and analyzes the detection data according to a certain algorithm, first determines whether there is a car, judges the vehicle type when there is a car, and calculates the parking position parameter. And car geometry parameters.
The host software is written in Delphi and can be used to display measurement parameters and set operating parameters.
Figure 4 main software flow
5 Tests and results
The test was conducted at an outdoor industrial site. The working area is 5 m Ã— 21 ITI, the spacing of the infrared modules is 5 cm, and the number of modules in the infrared transceiver array is 425. The positioning of 100 vehicles in a row, including a variety of models, has been successfully positioned. The positioning data of 5 cars extracted during the day and night were compared with the physical data, and the results are shown in Table 1. The car length and front distance measurement error does not exceed 5 cm, the car width and margin measurement error does not exceed 6 cln, and the single positioning time can be as fast as 1 s.
The results show that the acousto-optic detection technology can realize the non-contact positioning of objects in the plane. The vehicle positioning system based on sound and light detection, whether it is positioning speed, positioning accuracy or positioning reliability, is significantly improved compared with other current positioning methods. At present, the system has been used in the automatic sampling control system of automobile materials, and has been applied in many steel power enterprises, and the operation effect is good.
The vehicle positioning system is used to detect the parking position parameters of the vehicle and the geometric parameters of the vehicle, and provides plane coordinate data for the robot to work in the range of the car. It is an integral part of the automatic operation control system for the vehicle. At present, the automobile positioning system mostly uses a mechanical displacement infrared scanning method of a gear transmission or a manual drawing method based on a video image. The former has a slow positioning speed, the latter has low positioning accuracy and poor reliability, and it is difficult to satisfy the actual positioning speed, accuracy and reliability. Sexual requirements. In this paper, infrared electronic shift progressive high-speed scanning technology and ultrasonic ranging technology are used to realize vehicle positioning. It has adjustable positioning speed and ability to adapt to bad weather. It also adopts various measures to improve the system's anti-interference ability and maintainability. The goal of fast, high precision, and high reliability positioning. The main control software developed by Delphi is used to realize data processing, complete display and output of positioning results, working parameter setting and status detection, and has good openness and convenient interface with various control systems.
1 Working principle and system composition
1.1 Working principle
The combination of a transmissive infrared photoelectric sensor and an ultrasonic distance measuring device enables positioning of objects in a planar area. The transmissive infrared photoelectric sensor is composed of an infrared transmitting module and an infrared receiving module. When an object blocks the optical path between the transceiver modules, the receiving state of the receiving module is changed, thereby whether the non-contact detecting object exists.
If a plurality of transmitting modules and a plurality of receiving modules are arranged in parallel in two rows at a fixed interval, the infrared modules at corresponding positions on the transmitting and receiving sides are alternately turned on in a one-to-one manner, and the inter-area region is subjected to progressive scanning detection. According to the scanning result, not only can the object be present in the area, but also the length of the object and its longitudinal relative position in the area.
Ultrasonic ranging usually uses the transit time method, the distance between the transceiver and the measured object:
Where v is the propagation velocity of the ultrasonic wave in the medium; t is the round-trip time interval of the ultrasonic wave. An ultrasonic distance measuring device is installed at a calibration position on both sides of the object to measure the distance from the object, and the width of the object and its lateral relative position in the area can be calculated.
1.2 System components
Figure 1 shows the composition of an automotive positioning system based on acousto-optic detection.
In the figure, the single chip microcomputer 1, the infrared emitting array, the infrared receiving array and the electronic shifting circuit constitute an infrared electronic shift progressive scanning circuit for measuring the length of the car and the longitudinal parking position. The distance measuring system consisting of a single chip microcomputer 2 and four ultrasonic distance measuring devices is used for measuring the width of the car and the position of the lateral parking position.
Figure 1 System composition
The infrared emission array and the infrared receiving array are installed at the height of the middle part of the vehicle compartment on both sides of the working area, and are respectively composed of N transmitting modules and N receiving modules, which are evenly arranged in parallel, and have one-to-one correspondence. Four ultrasonic distance measuring devices are installed on both sides of the work area, and are divided into two groups to measure the front car and the rear car.
The host comprehensively processes and analyzes the data of the longitudinal detection and the lateral detection to determine whether there is a car or a vehicle in the work area, and calculates the parking position parameter and the vehicle geometry of the vehicle in the area.
2 Infrared electronic shift progressive scan circuit design and debugging
2.1 Circuit design
2 is an infrared electronic shift progressive scan circuit. Only a pair of circuits for the infrared transmitting and receiving modules are shown, and the pulse generator circuit is omitted. The pulse generator generates an oscillating signal of 38 kHz, which is modulated by low frequency pulses and sent to the transmitting module. The electronic switch of the infrared transmitting module is turned on when the control signal is high level, and the signal sent by the pulse generator is transmitted; the electronic switch of the infrared receiving module is also turned on when the control signal is high, and the receiving of the infrared receiving head is received. The status output is sent to the MCU 1. The electronic shift circuit consists of 74LSl64 series, with N output terminals, each of which controls an infrared module. The switching signal is a high level pulse that moves one bit forward for each shift clock cycle. Since the shifting clocks on both sides of the transmitting and receiving are synchronized, the infrared modules at corresponding positions on the transmitting and receiving sides are turned on in a one-to-one manner in sequence, thereby achieving the purpose of electronic shift progressive scanning.
2.2 Scanning speed and precision processing
The scanning speed mainly depends on the period of the shift clock, and the time to complete one scan:
This circuit has good reception reliability at Î”f â‰¥ 2 ms. The single-chip microcomputer l can be controlled by the program to make Î”t 2~10 ms to meet the needs of different scanning speeds.
In the infrared array, the adjacent module spacing Î”Z is the highest positioning accuracy in the longitudinal direction. The number N of modules in the infrared array is determined according to the requirement of the longitudinal maximum length L of the working area, and NÃ—A/=L is required.
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