Multi-scene multiplexing single-rail automatic board feeding control method for high-speed SMT chip mounter

Abstract

The invention discloses a high-speed SMT chip mounter multi-scene multiplexing single-rail automatic board feeding control method, which comprises the following steps that: an SMT chip mounter forwards conveys a substrate through a conveying belt, and the conveying belt is divided into three areas, namely a board feeding waiting area, a mounting working area corresponding to a mounting working area of the SMT chip mounter and a board discharging waiting area; in the substrate conveying process, each detection sensor is polled through the control unit, the control unit creates and updates the logic state sequence table according to the combinational logic of trigger signals of each detection sensor, the automatic substrate conveying device has the advantages of perfect control algorithm logic, low cost and high substrate conveying speed, the conveying belt can convey substrates with different lengths in a mixed mode, and the production efficiency is improved. The substrate length range of the substrate is judged in real time after the conveying belt is started each time, a substrate cavity processing method is arranged, and the robustness of the system is greatly enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of control systems for high-speed SMT placement machines, and in particular to a control method for single-track automatic board feeding for multi-scene multiplexing of high-speed SMT placement machines. Background Art

[0002] SMT equipment (surface mounted technology) that absorbs and mounts electronic components onto circuit substrates is usually equipped with a conveying device to transport substrates processed by upstream equipment to this equipment for mounting. After mounting is completed, the substrates are transported to downstream equipment, allowing the entire assembly line to operate automatically and stably.

[0003] In recent years, in pursuit of higher production efficiency, many SMT-related technical personnel have been improving mounting efficiency from all aspects, such as increasing the mounting speed of SMT placement machines as much as possible and optimizing the mounting path as much as possible. However, with the development of technology, the optimization of SMT mounting speed and mounting path has become very difficult, and the efficiency of substrate entry and exit of SMT equipment has also become a research hotspot, as shown in the Chinese patents with patent announcement numbers CN103717008A, CN103813645A and CN116588636A.

[0004] Among them, the patent with announcement number CN103717008A proposes a substrate conveying control method, which divides the working modes of the board conveying device into three types, but only describes the substrate control process during the substrate conveying process, and there is no critical logic related to the substrate being able to accurately stop at a preset position in the mounting work area.

[0005] The patent with announcement number CN103813645A provides an automatic board feeding device and control method. The four-stage board feeding device can quickly transport substrates with a length of 300 mm. However, when the length of the substrate exceeds 300 mm, its advantages no longer exist and its application scenarios are limited. Compared with the single-stage board feeding structure, its software and hardware complexity and cost increase exponentially, and later maintenance is more difficult.

[0006] The patent with announcement number CN116588636A provides a single-track multi-stage conveying control method. The patent content is only a general control method for some international products. It does not mention the judgment logic of the substrate length. It only uses the board length data input by the host computer before initialization. There is no continuous detection and judgment during the operation of the equipment. Then this is precisely the most important thing, because once the substrate is too long, if there is a slight logical error, the micro-cylinder under the substrate will lift the stop rod, which will have very serious consequences; secondly, it does not mention the processing logic of the presence of voids in the substrate.

[0007] The prior art generally adopts a three-stage substrate conveying technology, which is divided into three tracks: a board entry waiting area, a mounting work area, and a board exit waiting area. A parallel processing method is adopted. For example, when there are substrates in the mounting work area for mounting operations, the board entry waiting area can receive upstream substrates in real time if there are no substrates. The board exit waiting area can also actively respond to downstream board request signals to reduce waiting time, improve space utilization, and thus improve overall mounting efficiency.

[0008] However, there may be vibration and impact in the transition area between the tracks, which will affect the positioning accuracy of the electronic components on the substrate. In addition, the use of multi-section tracks means higher costs due to the increase in the number of motors and other components. Summary of the invention

[0009] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a control method for a single-track automatic board feeding for a high-speed SMT placement machine with multi-scenario multiplexing, which has low cost, fast board feeding speed, dynamic adjustment of application scenarios, and enhanced system robustness.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is: a control method for a single-track automatic board feeding for a high-speed SMT placement machine with multiple scenes, comprising the following steps:

[0011] The SMT placement machine transports the substrate forward through a conveyor belt, which is divided into three areas: the board entry waiting area, the placement work area corresponding to the SMT placement machine's placement work area, and the board exit waiting area.

[0012] Detection sensors are set in the board entry waiting area, mounting work area and board exit waiting area to detect whether there is a substrate at the corresponding position.

[0013] During the substrate conveying process, the control unit polls each detection sensor, and the control unit creates and updates the logic state sequence table according to the combination logic of the trigger signal of each detection sensor.

[0014] In the logic state sequence table, the board entry waiting area, the mounting work area and the board exit waiting area are respectively provided with corresponding substrate conveying instructions according to the combination logic of different trigger signals of the detection sensors set in the corresponding areas.

[0015] In the process of continuously conveying the substrate, the control unit controls the board entry waiting area, the mounting work area and the board exit waiting area to respectively execute the corresponding substrate conveying instructions according to the combination logic of the updated logic state sequence table;

[0016] The control unit reads the substrate length of the substrate entering the board waiting area input from the host computer, and obtains the substrate length range and the maximum mountable range in real time through the detection sensor. The substrate length range is the length of the largest substrate that can be accommodated in the board waiting area, and the maximum mountable range is the maximum distance of the placement head of the SMT placement machine from the board entry position to the end point of the placement work area in the X-axis direction.

[0017] The control unit compares the length of the substrate with the maximum length range of the substrate that can be accommodated in the board waiting area. If the length of the substrate is not greater than the substrate length range, the single-track three-stage substrate conveying mode is entered. If the length of the substrate is greater than the substrate length range, the substrate length continues to be compared with the maximum mountable range. If the length of the substrate is not greater than the maximum mountable range, the single-track single-stage substrate conveying mode is entered. If the length of the substrate is greater than the maximum mountable range, the SMT placement machine is stopped or the substrate is stopped at the maximum mountable position of the placement head in the X-axis direction. The control unit automatically switches to the corresponding substrate conveying mode for substrates of different lengths.

[0018] In a further technical solution, the detection sensor comprises sensors s1 to s5 arranged in sequence along the board feeding direction.

[0019] Sensors s1 and s2 are respectively arranged at the front and rear sides of the board entry waiting area.

[0020] Sensor s3 is arranged in the mounting work area.

[0021] Sensors s4 and s5 are respectively arranged at the front and rear sides of the board exit waiting area.

[0022] The control unit polls the sensors s1 to s5, and the control unit reads the trigger signals of the sensors s1 to s5 to create and update the logic state sequence table;

[0023]

[0024] In the logic state sequence table,

[0025] The board entry waiting area is provided with corresponding combination logic and substrate conveying instructions corresponding to the board entry waiting area according to the trigger signals of sensors s1 and s2. The corresponding relationship is combination logic 00: idle, combination logic 01: start board entry, combination logic 10: start board stop or wait for placement, combination logic 11: L1 logic, L1 logic is the single-track single-stage substrate conveying mode.

[0026] The mounting work area is provided with corresponding combination logic and substrate conveying instructions corresponding to the mounting work area according to the trigger signal of sensor s3. The corresponding relationship is combination logic 0: idle, combination logic 1: start to stop the board or mount work.

[0027] The board waiting area is provided with corresponding combination logic and substrate conveying instructions corresponding to the board waiting area according to the trigger signals of sensors s4 and s5, and the corresponding relationship is combination logic 00: idle, combination logic 01: start board feeding, combination logic 10: start board stop or wait for board output, combination logic 11: L3 logic, L3 logic is the single-track three-stage substrate conveying mode;

[0028] For substrates of different lengths entering the board waiting area, the control unit that conforms to the L1 logic automatically switches to the single-track single-stage substrate conveying mode, and the control unit that conforms to the L3 logic automatically switches to the track three-stage substrate conveying mode.

[0029] A further technical solution is that when conveying the substrate, the maximum uniform speed of the substrate in the board-out waiting area is less than the maximum uniform speed of the substrate entering the board-in waiting area and the maximum uniform speed of the substrate entering the mounting work area; the conveyor belt adopts the standard SMEMA protocol when requesting boards from upstream equipment and delivering boards to downstream equipment.

[0030] A further technical solution is that three baffles are arranged at intervals on the conveyor belt, and the control unit drives the baffles through corresponding cylinders to block the substrate from moving forward or release the substrate, and the three baffles are used to separate the conveyor belt into three areas: the board entry waiting area, the mounting work area and the board exit waiting area.

[0031] A further technical solution is that along the board feeding direction, the cylinder includes a board feeding waiting cylinder a1, a mounting working cylinder a2 and a board exiting waiting cylinder a3 which are sequentially arranged above or on one side of the conveyor belt, and the board feeding waiting cylinder a1, the mounting working cylinder a2 and the board exiting waiting cylinder a3 are respectively connected to a corresponding stopper rod.

[0032] When the board entry waiting cylinder a1, the mounting working cylinder a2 or the board exit waiting cylinder a3 remains in a closed state, the corresponding baffle rod is lifted; when the board entry waiting cylinder a1, the mounting working cylinder a2 or the board exit waiting cylinder a3 remains in an open state, the corresponding baffle rod descends to a position capable of blocking the advancement of the substrate.

[0033] A further technical solution is that the substrate length range is the maximum distance from the substrate entry position entering the substrate waiting area to the substrate entry waiting cylinder a1, and the maximum mountable range is the maximum distance from the placement head of the SMT placement machine in the X-axis direction from the substrate entry position to the placement working cylinder a2. The control unit detects and obtains the substrate length range and the maximum mountable range in real time through pairwise coupling of sensors s1 to s5.

[0034] According to a further technical solution, the control unit polls the sensors s1 to s5 at a polling frequency of 1-20 kHz. After the control unit establishes the logic state sequence table, if a trigger signal of any of the sensors s1 to s5 changes in the polling results of the control unit cyclically polling the sensors s1 to s5, the control unit does not immediately update the logic state sequence table and continues to poll the sensors s1 to s5. When the polling results are consistent for at least three times, the logic state sequence table of the corresponding area is updated to prevent substrate voids.

[0035] A further technical solution is that in the single-track single-stage substrate conveying mode, the conveyor belt conveys the substrate through the board entry waiting area and directly enters the mounting work area, and the final stop position of the substrate is determined by combining the substrate length input by the host computer and the coupling logic of the detection sensor set in the mounting work area;

[0036] In the single-track three-stage substrate conveying mode, the control unit determines whether there is an idle area and no substrate in the area through the trigger signal of each detection sensor.

[0037] If the board entry waiting area is idle, a board request signal will be sent to the upstream device.

[0038] If the mounting work area is idle, the substrates in the waiting area will be transported to the mounting work area.

[0039] If the board waiting area is free, the substrates in the board waiting area and the mounting work area will be transported to the corresponding next area at the same time.

[0040] If all areas are free, the board will be sent directly to the mounting work area.

[0041] A further technical solution is that in the single-track single-stage substrate conveying mode, the board-feeding waiting cylinder a1 is continuously locked to be in a closed state, and the state switching of the mounting working cylinder a2 depends on the substrate length of the substrate. When the substrate length is not greater than the maximum mountable range, the mounting working cylinder a2 is opened to stop the substrate at the mounting working cylinder a2; when the substrate length is greater than the maximum mountable range, the mounting working cylinder a2 is locked to be in a closed state until the board is released and the mounting working cylinder a2 is opened after the board is discharged;

[0042] The state of the plate-out waiting cylinder a3 depends on the downstream device. After the control unit sends a plate-sending signal to the downstream device, if the control unit does not receive a plate-requesting signal from the downstream device, the plate-out waiting cylinder a3 will be kept in an open state. After the control unit receives a plate-requesting signal from the downstream device, the cylinder a3 will be unlocked and kept in a closed state to ensure smooth plate output.

[0043] Compared with the prior art, the advantages of the present invention are: the present invention has a complete control algorithm logic, low cost, fast board feeding speed, the conveyor belt can mix substrates of different lengths, the substrate length range of the substrate is judged in real time after each start of the conveyor belt, and a substrate void processing method is provided, which greatly enhances the robustness of the system.

[0044] The present invention combines the substrate length range detected in real time by the detection sensors on the conveyor belt coupled in pairs to automatically switch to the corresponding substrate conveying mode for substrates of different lengths and dynamically adjust the application scenarios. The three areas of the conveyor belt execute corresponding substrate conveying instructions in all substrate conveying modes according to the created and updated logic state sequence table. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Schematic diagram of the conveying device of the chip mounter according to the embodiment of the present invention

[0046] Figure 2 Schematic diagram of single-track single-stage conveying of a conveying device of a chip mounter according to an embodiment of the present invention

[0047] Figure 3 Schematic diagram of single-track three-stage conveying of the conveying device of the chip mounter according to the embodiment of the present invention

[0048] Figure 4 Rear view of the conveying device assembly of the chip mounter according to the embodiment of the present invention

[0049] Figure 5 Flow chart of switching mode of conveying substrate of conveying device of chip mounter according to an embodiment of the present invention

[0050] Figure 6 Single-track single-stage control logic flow chart of the conveying device of the chip mounter conveying substrate according to the embodiment of the present invention

[0051] Figure 7 A single-track three-stage control logic flow chart of a conveying device of a placement machine according to an embodiment of the present invention for conveying a substrate. DETAILED DESCRIPTION

[0052] A control method for single-track automatic board feeding for high-speed SMT placement machines with multiple scenes. Figures 1 to 7 As shown, the following steps are included:

[0053] The SMT placement machine conveys the substrate forward through a conveyor belt, and separates the three areas on the conveyor belt into a board-in waiting area, a mounting work area corresponding to the mounting work area of ​​the SMT placement machine, and a board-out waiting area. Specifically, three baffles are arranged at intervals on the conveyor belt, and the control unit drives the baffles through corresponding cylinders to block the substrate from moving forward or release the substrate. The three baffles separate the three areas on the conveyor belt into an board-in waiting area, a mounting work area, and a board-out waiting area. Along the board feeding direction, the cylinders include a board feeding waiting cylinder a1, a mounting working cylinder a2 and a board exiting waiting cylinder a3 which are sequentially arranged above or on one side of the conveyor belt. The board feeding waiting cylinder a1, the mounting working cylinder a2 and the board exiting waiting cylinder a3 are respectively connected to a corresponding baffle rod. When the board feeding waiting cylinder a1, the mounting working cylinder a2 or the board exiting waiting cylinder a3 remains in a closed state, the corresponding baffle rod is lifted; when the board feeding waiting cylinder a1, the mounting working cylinder a2 or the board exiting waiting cylinder a3 remains in an open state, the corresponding baffle rod descends to a position capable of blocking the advancement of the substrate.

[0054] Detection sensors for detecting whether there are substrates at corresponding positions are respectively arranged in the board entry waiting area, the mounting work area and the board exit waiting area. The detection sensors include sensors s1 to s5 arranged in sequence along the board entry direction. Sensors s1 and s2 are respectively arranged at the front and rear sides of the board entry waiting area, sensor s3 is arranged in the mounting work area, and sensors s4 and s5 are respectively arranged at the front and rear sides of the board exit waiting area.

[0055] The control unit reads the substrate length of the substrate entering the board waiting area input from the host computer, and the control unit detects in real time through the sensors s1~s5 in pairs and obtains the substrate length range and the maximum mountable range. Among them, the substrate length range is the length of the maximum substrate that can be accommodated in the board waiting area, the substrate length range is the maximum distance from the board entry position of the substrate entering the board waiting area to the board entry waiting cylinder a1, and the maximum mountable range is the maximum distance from the board entry position to the end point of the mounting work area of ​​the SMT mounting machine in the X-axis direction, that is, the maximum mountable range is the maximum distance from the board entry position to the mounting work cylinder a2 of the SMT mounting machine in the X-axis direction.

[0056] The control unit compares the length of the substrate with the maximum length range of the substrate that can be accommodated in the board waiting area. If the length of the substrate is not greater than the length range of the substrate, the single-track three-stage substrate conveying mode is entered. If the length of the substrate is greater than the length range of the substrate, the length of the substrate is further compared with the maximum mountable range. If the length of the substrate is not greater than the maximum mountable range, the single-track single-stage substrate conveying mode is entered. If the length of the substrate is greater than the maximum mountable range, the L2 logic is met. If the L2 logic is met, the SMT placement machine is stopped or the substrate is stopped at the maximum mountable position of the placement head in the X-axis direction. The control unit automatically switches to the corresponding substrate conveying mode for substrates of different lengths.

[0057] At the same time, during the substrate conveying process, the control unit polls each detection sensor, and the control unit creates and updates the logic state sequence table according to the combination logic of the trigger signal of each detection sensor.

[0058] In the logic state sequence table, the board entry waiting area, the mounting work area and the board exit waiting area are respectively provided with corresponding substrate conveying instructions according to the combination logic of different trigger signals of the detection sensors set in the corresponding areas.

[0059] The control unit polls sensors s1~s5, and the control unit reads the trigger signals of sensors s1~s5 to create and update the logic state sequence table, as shown in Table 1; the control unit polls sensors s1~s5 at a polling frequency of 1-20kHz. After the control unit establishes the logic state sequence table, if the trigger signal of any sensor s1~s5 changes in the polling results of the control unit cyclically polling sensors s1~s5, the control unit does not immediately update the logic state sequence table and continues to poll sensors s1~s5. When at least 3 polling results are consistent, the logic state sequence table of the corresponding area is updated to prevent substrate voids.

[0060]

[0061]

[0062] Table 1 - Logical state sequence table

[0063] In the logic state sequence table,

[0064] The board entry waiting area is set with corresponding combination logic and substrate conveying instructions corresponding to the board entry waiting area according to the trigger signals of sensors s1 and s2. The corresponding relationship is combination logic 00: idle, combination logic 01: start board entry, combination logic 10: start board stop or wait for placement, combination logic 11: L1 logic, L1 logic is a single-track single-stage substrate conveying mode,

[0065] The mounting work area is provided with corresponding combination logic and substrate conveying instructions corresponding to the mounting work area according to the trigger signal of sensor s3. The corresponding relationship is combination logic 0: idle, combination logic 1: start to stop the board or mount work.

[0066] The board waiting area is provided with corresponding combination logic and substrate conveying instructions corresponding to the board waiting area according to the trigger signals of sensors s4 and s5. The corresponding relationship is combination logic 00: idle, combination logic 01: start board feeding, combination logic 10: start board stop or wait for board output, combination logic 11: L3 logic, L3 logic is a single-track three-stage substrate conveying mode;

[0067] For substrates of different lengths entering the board waiting area, the control unit that conforms to the L1 logic automatically switches to the single-track single-stage substrate conveying mode, and the control unit that conforms to the L3 logic automatically switches to the track three-stage substrate conveying mode.

[0068] During the continuous conveying of substrates, the control unit controls the board entry waiting area, the mounting work area and the board exit waiting area to respectively execute corresponding substrate conveying instructions according to the combinational logic of the updated logic state sequence table.

[0069] When conveying substrates, the maximum uniform speed of the substrates in the outgoing board waiting area is less than the maximum uniform speed of the substrates entering the incoming board waiting area and the maximum uniform speed of the substrates entering the mounting work area; the conveyor belt adopts the standard SMEMA protocol when requesting boards from upstream equipment and delivering boards to downstream equipment.

[0070] In the single-track single-stage substrate conveying mode, the conveyor belt conveys the substrate through the board waiting area and directly enters the mounting work area. The final stop position of the substrate is determined by combining the substrate length input by the host computer and the coupling logic of the detection sensor set in the mounting work area, Table 2;

[0071]

[0072] Table 2 Sensor coupling logic

[0073] Specifically, in the single-track single-stage substrate conveying mode, the board-feeding waiting cylinder a1 is continuously locked in the closed state, and the state switching of the mounting working cylinder a2 depends on the substrate length of the substrate. When the substrate length is not greater than the maximum mountable range, the mounting working cylinder a2 is opened, and the substrate is stopped at the mounting working cylinder a2; when the substrate length is greater than the maximum mountable range, the mounting working cylinder a2 is locked in the closed state until the board is released and the mounting working cylinder a2 is opened.

[0074] The state of the plate-out waiting cylinder a3 depends on the downstream device. After the control unit sends a plate-sending signal to the downstream device, if the control unit does not receive a plate-requesting signal from the downstream device, the plate-out waiting cylinder a3 will be kept in an open state. After the control unit receives a plate-requesting signal from the downstream device, the cylinder a3 will be unlocked and kept in a closed state to ensure smooth plate output.

[0075] In the single-track three-stage substrate conveying mode, the control unit determines whether there is an idle area and there is no substrate in the area through the trigger signals of each detection sensor. If the board waiting area is idle, a board request signal will be sent to the upstream equipment. If the mounting work area is idle, the substrate in the board waiting area will be transported to the mounting work area. If the board out waiting area is idle, the substrates in the board waiting area and the mounting work area will be transported to the corresponding next area at the same time. If all areas are idle, the board will be sent directly to the mounting work area.

[0076] Specifically, in the single-track three-stage substrate conveying mode, the control unit polls sensors s1~s5 and determines whether all areas on the conveyor belt are idle and have no substrates. If so, a board request signal is sent upstream until sensor s1 is triggered. The control unit controls the motor to start conveying the substrate. When sensor s2 is triggered, the control unit updates the logic state sequence table in real time and obtains the substrate length threshold on the conveyor belt, determines the substrate length range of the substrate, and determines whether it complies with the L1 logic. If not, it complies with the L3 logic (three-stage control logic). The control unit opens the mounting working cylinder a2, locks the board waiting cylinder a1 to the closed state, and continues to maintain a uniform speed of conveying. When sensor s3 is triggered, the control motor starts to decelerate and finally stops the substrate accurately at the mounting working cylinder a2, and then starts the mounting work.

[0077] If there is an idle area on the conveyor belt and there is no substrate in the area, if the board entry waiting area is idle, a board request signal is sent upstream; if the mounting work area is idle, the board entry waiting cylinder a1 is closed, and the motor is controlled to start conveying until the sensor s3 is triggered, and the board is decelerated and stopped, and then the board entry waiting cylinder a1 is opened; if the board exit waiting area is idle, the board exit waiting cylinder a3 is opened, the board entry waiting cylinder a1 and the mounting work cylinder a2 are closed, and the motor is started to convey the substrate, and the substrates in the board entry waiting area and the mounting work area are simultaneously conveyed to the corresponding next area. When the substrate entering the board entry waiting area triggers the sensor s5, the mounting work cylinder a2 is opened, and the motor is controlled to decelerate to the minimum uniform speed and then maintain a uniform speed to ensure that the substrate entering the mounting work area can reach the mounting work cylinder a2, and then the motor is stopped for conveying. Because the length of the mounting work area is greater than the length of the board exit waiting area, the substrate is conveyed to the mounting work area while being conveyed to the board exit waiting area, which effectively improves the conveying efficiency.

[0078] Among them, sensors s2~s4 are opposite-beam sensors, with a receiving end and a transmitting end. Since the installation positions of sensors s3 and s4 are relatively close, if the transmitting ends are on the same side, coupling interference will occur at the receiving end, and the detection accuracy cannot be well guaranteed. The transmitting ends of sensors s3 and s4 should be installed on the opposite sides. As for the specific selection of the installation position of the transmitting end, the best effect of the actual test shall prevail. The specific installation strategy adopted in the embodiment of the present invention is that the transmitting end of sensor s3 is installed on the side close to the micro cylinder, and the transmitting end of sensor s4 is installed on the side away from the micro cylinder (the rectangle in the schematic diagram is the transmitting end, and the circle is the receiving end). Of course, the conveyor belt also includes other components, such as the conveying motor, width adjustment motor, and clamping device that control the conveyor belt, which are not further indicated in the schematic diagram. The control unit of the embodiment of the present invention adopts NXP high-performance MCU as the core, which has high performance, low power consumption and rich peripheral interfaces, and is very suitable for motor control. All sensors and components are electrically connected to the control unit, and the method is implemented based on the control unit.

[0079] The length and specifications of the substrates transported by the conveyor belt are determined by actual production needs and cannot be limited. Therefore, in order to meet flexible and changeable production needs, the conveying mode of the conveyor belt needs to be adaptively adjusted, such as Figure 5 As shown, the control unit reads the trigger status of the detection sensor in real time, and through pairwise coupling (coupling logic shown in Table 2), combined with the substrate length input by the host computer, it ensures that the system can accurately and real-time obtain the threshold value of the substrate length transported on the conveyor belt, determine the current mode of conveying the substrate on the conveyor belt, and avoid the situation in which the placement machine does not operate normally due to the disorder of the sequence of substrates of different lengths during the upstream board delivery process.

Claims

1. A control method for single-track automatic board feeding for high-speed SMT placement machines with multiple scenes, characterized by: The following steps are involved: The SMT placement machine transports the substrate forward through a conveyor belt, which is divided into three areas: the board entry waiting area, the placement work area corresponding to the SMT placement machine's placement work area, and the board exit waiting area. Detection sensors are set in the board entry waiting area, mounting work area and board exit waiting area to detect whether there is a substrate at the corresponding position. During the substrate conveying process, the control unit polls each detection sensor, and the control unit creates and updates the logic state sequence table according to the combination logic of the trigger signal of each detection sensor. In the logic state sequence table, the board entry waiting area, the mounting work area and the board exit waiting area are respectively provided with corresponding substrate conveying instructions according to the combination logic of different trigger signals of the detection sensors set in the corresponding areas. In the process of continuously conveying the substrate, the control unit controls the board entry waiting area, the mounting work area and the board exit waiting area to respectively execute the corresponding substrate conveying instructions according to the combination logic of the updated logic state sequence table; The control unit reads the substrate length of the substrate entering the board waiting area input from the host computer, and obtains the substrate length range and the maximum mountable range in real time through the detection sensor. The substrate length range is the length of the largest substrate that can be accommodated in the board waiting area, and the maximum mountable range is the maximum distance of the placement head of the SMT placement machine from the board entry position to the end point of the placement work area in the X-axis direction. The control unit compares the length of the substrate with the maximum length range of the substrate that can be accommodated in the board waiting area. If the length of the substrate is not greater than the substrate length range, the single-track three-stage substrate conveying mode is entered. If the length of the substrate is greater than the substrate length range, the substrate length continues to be compared with the maximum mountable range. If the length of the substrate is not greater than the maximum mountable range, the single-track single-stage substrate conveying mode is entered. If the length of the substrate is greater than the maximum mountable range, the SMT placement machine is stopped or the substrate is stopped at the maximum mountable position of the placement head in the X-axis direction. The control unit automatically switches to the corresponding substrate conveying mode for substrates of different lengths.

2. According to claim 1, a control method for a single-track automatic board feeding for a high-speed SMT placement machine with multiple scenes is characterized by: The detection sensor includes sensors s1 to s5 arranged in sequence along the board feeding direction. Sensors s1 and s2 are respectively arranged at the front and rear sides of the board entry waiting area. Sensor s3 is arranged in the mounting work area. Sensors s4 and s5 are respectively arranged at the front and rear sides of the board exit waiting area. The control unit polls the sensors s1 to s5, and the control unit reads the trigger signals of the sensors s1 to s5 to create and update the logic state sequence table; In the logic state sequence table, The board entry waiting area is provided with corresponding combination logic and substrate conveying instructions corresponding to the board entry waiting area according to the trigger signals of sensors s1 and s2. The corresponding relationship is combination logic 00: idle, combination logic 01: start board entry, combination logic 10: start board stop or wait for placement, combination logic 11: L1 logic, L1 logic is the single-track single-stage substrate conveying mode. The mounting work area is provided with corresponding combination logic and substrate conveying instructions corresponding to the mounting work area according to the trigger signal of sensor s3. The corresponding relationship is combination logic 0: idle, combination logic 1: start to stop the board or mount work. The board waiting area is provided with corresponding combination logic and substrate conveying instructions corresponding to the board waiting area according to the trigger signals of sensors s4 and s5, and the corresponding relationship is combination logic 00: idle, combination logic 01: start board feeding, combination logic 10: start board stop or wait for board output, combination logic 11: L3 logic, L3 logic is the single-track three-stage substrate conveying mode; For substrates of different lengths entering the board waiting area, the control unit that conforms to the L1 logic automatically switches to the single-track single-stage substrate conveying mode, and the control unit that conforms to the L3 logic automatically switches to the track three-stage substrate conveying mode.

3. According to claim 1, a control method for a single-track automatic board feeding for a high-speed SMT placement machine with multiple scenes is characterized by: When conveying the substrate, the maximum uniform speed of the substrate in the board-out waiting area is less than the maximum uniform speed of the substrate entering the board-in waiting area and the maximum uniform speed of the substrate entering the mounting work area; the conveyor belt adopts the standard SMEMA protocol when requesting boards from upstream equipment and delivering boards to downstream equipment.

4. According to claim 1, a control method for a single-track automatic board feeding for a high-speed SMT placement machine with multiple scenes is characterized by: Three baffles are arranged at intervals on the conveyor belt. The control unit drives the baffles through corresponding cylinders to block the substrate from moving forward or release the substrate. The three baffles are used to separate the conveyor belt into three areas: the board entry waiting area, the mounting working area and the board exiting waiting area.

5. According to claim 4, a control method for a single-track automatic board feeding for a high-speed SMT placement machine with multiple scenes is characterized in that: Along the board feeding direction, the cylinder includes a board feeding waiting cylinder a1, a mounting working cylinder a2 and a board exiting waiting cylinder a3 which are sequentially arranged above or on one side of the conveyor belt. The board feeding waiting cylinder a1, the mounting working cylinder a2 and the board exiting waiting cylinder a3 are respectively connected to a corresponding stopper rod. When the board entry waiting cylinder a1, the mounting working cylinder a2 or the board exit waiting cylinder a3 remains in a closed state, the corresponding baffle rod is lifted; when the board entry waiting cylinder a1, the mounting working cylinder a2 or the board exit waiting cylinder a3 remains in an open state, the corresponding baffle rod descends to a position capable of blocking the advancement of the substrate.

6. The control method for a single-track automatic board feeding for a high-speed SMT placement machine with multiple scenes according to claim 5 is characterized by: The substrate length range is the maximum distance from the substrate entry position entering the substrate waiting area to the substrate entry waiting cylinder a1, and the maximum mountable range is the maximum distance from the substrate entry position to the mounting working cylinder a2 in the X-axis direction of the mounting head of the SMT mounting machine. The control unit detects and obtains the substrate length range and the maximum mountable range in real time through the coupling of sensors s1~s5 in pairs.

7. A control method for a single-track automatic board feeding for a high-speed SMT placement machine with multiple scenes according to any one of claims 1 to 6, characterized in that: The control unit polls the sensors s1 to s5 at a polling frequency of 1-20 kHz. After the control unit establishes the logic state sequence table, if a trigger signal of any of the sensors s1 to s5 changes in the polling results of the control unit cyclically polling the sensors s1 to s5, the control unit does not immediately update the logic state sequence table and continues to poll the sensors s1 to s5. When at least three polling results are consistent, the logic state sequence table of the corresponding area is updated to prevent substrate voids.

8. The control method for a single-track automatic board feeding for a high-speed SMT placement machine with multiple scenes according to claim 7 is characterized by: In the single-track single-stage substrate conveying mode, the conveyor belt conveys the substrate through the board entry waiting area and directly enters the mounting work area, and the final stop position of the substrate is determined by combining the substrate length input by the host computer and the coupling logic of the detection sensor set in the mounting work area; In the single-track three-stage substrate conveying mode, the control unit determines whether there is an idle area and no substrate in the area through the trigger signal of each detection sensor. If the board entry waiting area is idle, a board request signal will be sent to the upstream device. If the mounting work area is idle, the substrates in the waiting area will be transported to the mounting work area. If the board waiting area is free, the substrates in the board waiting area and the mounting work area will be transported to the corresponding next area at the same time. If all areas are free, the board will be sent directly to the mounting work area.

9. The control method for a single-track automatic board feeding for a high-speed SMT placement machine with multiple scenes according to claim 8 is characterized by: In the single-track single-stage substrate conveying mode, the board-feeding waiting cylinder a1 is continuously locked and is in a closed state. The state switching of the mounting working cylinder a2 depends on the length of the substrate. When the length of the substrate is not greater than the maximum mountable range, the mounting working cylinder a2 is opened and the substrate is stopped at the mounting working cylinder a2; when the length of the substrate is greater than the maximum mountable range, the mounting working cylinder a2 is locked and is in a closed state until the board is released and the mounting working cylinder a2 is opened. The state of the plate-out waiting cylinder a3 depends on the downstream device. After the control unit sends a plate-sending signal to the downstream device, if the control unit does not receive a plate-requesting signal from the downstream device, the plate-out waiting cylinder a3 will be kept in an open state. After the control unit receives a plate-requesting signal from the downstream device, the cylinder a3 will be unlocked and kept in a closed state to ensure smooth plate output.

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