Automatic precise plate stopping method of SMT high-speed chip mounter

Abstract

The invention discloses an automatic precise plate stopping method of an SMT high-speed chip mounter, which comprises the following steps: when a middle detection sensor s3 is triggered, a control unit records and obtains an actual step length number h3 of a conveying motor, the control unit obtains a step length deviation for a standardized step length number, and the control unit calculates and obtains a node SN3 by combining the step length deviation; the control unit is used for controlling the conveying motor to rotate by a specific step length, so that the PCB continues to advance at the maximum constant speed Vmax, the conveying motor is controlled to start to decelerate when a node SN3 is reached, the speed of the PCB is reduced to 0, and the PCB is accurately stopped at the final position a2. The conveying efficiency is improved, and meanwhile the influence caused by sudden factors is eliminated.

Description

Technical Field

[0001] The invention relates to the technical field of control systems for SMT high-speed placement machines, and in particular to an automatic and precise board stopping method for SMT high-speed placement machines. Background Art

[0002] The SMT placement machine is equipped with a conveyor belt, which is used to automatically and accurately transport the PCB board (printed circuit board) stopped at the starting position to the end position for subsequent placement work. When conveying PCB boards, the conveyor belt uses acceleration and deceleration mode to quickly transport them in order to improve the conveying efficiency. However, PCB boards come in a variety of sizes, and the conveyor belt may also have aging and fatigue problems. If the acceleration and deceleration settings during the conveying process are not ideal, in addition, unexpected factors such as slipping may occur during the conveying process, resulting in the inability to accurately and stably transport the PCB board to the specified end position, which will have an adverse effect on subsequent placement work.

[0003] The current solution is mainly to set a baffle or baffle plate at the end position where the PCB board needs to stop, and drive the baffle or baffle plate through the action of a micro cylinder to limit the stopping position of the PCB board. During the transportation process, after triggering the intermediate detection sensor set before the end position, the conveyor belt is controlled to start decelerating to a relatively small speed, and then continue to maintain a constant speed for a period of time. The limit and restriction of the baffle bar are used to ensure that the PCB board can reach and stop at the end position. However, this control solution may inevitably take more time. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide an automatic and precise board stopping method for an SMT high-speed placement machine, which automatically and timely adjusts the acceleration and deceleration mode of the conveying, while improving the conveying efficiency, eliminating the influence caused by sudden factors, and conveying the PCB board to the specified end position more stably and accurately.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is: (the content is too much and will not be copied for the time being)

[0006] Compared with the prior art, the present invention has the following advantages: the present invention introduces feedback control, thereby eliminating the influence of sudden factors such as PCB board slippage or belt aging, and timely adjusting the acceleration and deceleration mode of the conveyor, thereby improving the conveying efficiency of the conveyor belt and ensuring that the PCB board is conveyed to the specified terminal position more stably and accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 A schematic structural diagram of a PCB board conveying device for an SMT high-speed placement machine according to the present invention.

[0008] Figure 2A schematic diagram of conveying PCB boards according to the present invention.

[0009] Figure 3 Trajectory diagram of the acceleration and deceleration mode of the present invention.

[0010] Figure 4 Flowchart of the control method of the present invention.

[0011] Figure 5 Flowchart of the feedback control of the present invention.

[0012] Figure 6 A control flow chart of error identification of the present invention. DETAILED DESCRIPTION

[0013] An automatic and accurate board stopping method for a SMT high-speed placement machine. Figures 1 to 6 As shown, the following steps are included:

[0014] The conveyor belt is driven by the conveyor motor to convey the PCB board. The control unit controls the conveyor motor by controlling the number of steps of the conveyor motor. The SMT high-speed placement machine conveys the PCB board stopped at the starting position a1 to the end position a2 specified by the SMT high-speed placement machine through the conveyor belt. Each PCB board goes through the acceleration stage, the uniform speed stage and the deceleration stage in sequence.

[0015] In the uniform speed stage, the PCB board moves at the set maximum uniform speed V max go ahead,

[0016] An intermediate detection sensor s3 is provided between the starting position a1 and the end position a2.

[0017] When the PCB reaches the position of the intermediate detection sensor s3 in the uniform speed stage, the intermediate detection sensor s3 is triggered.

[0018] The conveying motor for conveying the PCB from the starting position a1 to the intermediate detection sensor s3 needs a standardized step length h1.

[0019] The number of standardized steps h2 is required for the conveying motor to convey the PCB board from the middle detection sensor s3 to the end position a2.

[0020] The step node where the PCB board starts to decelerate is set to node SN3.

[0021] When the PCB board starts to be transported forward from the starting position a1, the control unit starts to count the step length of the conveyor motor driving the conveyor belt. When the intermediate detection sensor s3 is triggered, the control unit records the actual step length h3 of the conveyor motor.

[0022] Count the steps of the conveyor motor. If the conveyor motor driving the conveyor belt is in open-loop pulse control mode, record the number of pulses issued by the control unit. If the conveyor belt is driven by bus control mode, the control unit records the number of pulses fed back by the encoder or reads the absolute position of the current conveyor motor in real time.

[0023] The control unit compares the standardized step length h1 with the actual step length h3 and obtains the step length deviation.

[0024] The control unit calculates node SN3 by combining the step size deviation and the standardized step size number h2.

[0025] The control unit controls the conveying motor to rotate at a specific step length, so that the PCB board continues to rotate at a maximum uniform speed V max The PCB board moves forward at a speed until node SN3, at which the conveying motor is controlled to start decelerating, until the speed of the PCB board drops to 0 and the PCB board stops precisely at the end position a2. The present invention combines feedforward control and step length control to ensure that the PCB board always stops precisely at the end position a2.

[0026] When the PCB board triggers the intermediate detection sensor s3, if the step deviation obtained by comparison is greater than the set range, the control unit determines that the conveying state is abnormal. If the PCB board suddenly becomes abnormal due to sudden factors during the conveying process, the control unit will modify the deceleration in the deceleration stage to the minimum deceleration b. min And in the deceleration stage of conveying the PCB board, the minimum deceleration b min Slow down.

[0027] The conveying track corresponding to the PCB board includes node SN0, node SN1, node SN2, node SN3 and node SN4 in sequence, where N is 1-4. Figure 3 As shown,

[0028] Node SN0 corresponds to the step node starting from the starting position a1, corresponding to the starting position a1;

[0029] Node SN1 corresponds to the node where acceleration is completed and uniform motion step starts;

[0030] Node SN2 corresponds to the step length node reaching the position of the intermediate detection sensor s3, that is, the position where the PCB board triggers the intermediate detection sensor s3;

[0031] Node SN3 corresponds to the step length node for uniform speed completion and deceleration;

[0032] Node SN4 corresponds to the step length node that reaches the location of the end position a2, corresponding to the end position a2;

[0033] The node SN0 corresponds to the point SN1 which is the acceleration stage, and the speed of the PCB board increases from 0 to the set uniform speed;

[0034] Node SN1 to node SN3 corresponds to the uniform speed stage.

[0035] Node SN3 to node SN4 corresponds to the deceleration stage, during which the speed of the PCB board decreases from the set uniform speed to 0.

[0036] The present invention presets a standard conveying trajectory, a minimum conveying trajectory, a maximum conveying trajectory and an abnormal conveying trajectory in the memory of the control unit.

[0037] The control method of the standard conveying trajectory is to use the standard acceleration a in the acceleration stage s Acceleration, in the uniform speed stage, the maximum uniform speed V set based on the specific SMT high-speed placement machine is used max Move forward at a constant speed, and use the standard deceleration b during the deceleration stage s Deceleration, standard acceleration a s and standard deceleration b s It is a moderate value determined based on the structure of the conveyor belt.

[0038] The control method of the minimum conveying trajectory is to use the minimum acceleration a in the acceleration stage. min , the deceleration in the deceleration phase adopts the minimum deceleration b min , minimum acceleration a min and minimum deceleration b min It is the minimum value determined based on the structure of the conveyor belt to ensure that no PCB board will slip, which will take more time accordingly.

[0039] The maximum conveying trajectory is controlled in such a way that the acceleration in the acceleration phase adopts the maximum acceleration a max , the deceleration in the deceleration stage adopts the maximum deceleration b max , maximum acceleration a max and maximum deceleration b max It is the maximum value determined based on the structure of the conveyor belt; it reduces the time spent by the PCB board in the conveying process.

[0040] The control method for abnormal conveying trajectory is to modify the deceleration in the deceleration stage to the minimum deceleration b min .

[0041] In the batch placement production process of the SMT high-speed placement machine, if the conveyor belt conveys the first PCB board of this batch, the control unit uses the preset standard conveying trajectory control method to convey the PCB board;

[0042] When the intermediate detection sensor s3 is triggered, the control unit makes a judgment based on the step deviation. If the step deviation is within the set range, it is judged that the conveying state of the first PCB board is normal, and the first PCB board is controlled to be conveyed according to the preset standard conveying trajectory, and continues to be conveyed at the maximum uniform speed V after the first PCB board triggers the intermediate detection sensor s3. max Go forward a step length S u , until reaching node S13,

[0043] S u The calculation method is

[0044]

[0045] Where D m-d is the standardized step length from the intermediate detection sensor s3 to the end position a2, D m-d is a fixed value.

[0046] If an unexpected factor occurs when conveying the first PCB board using the standard conveying trajectory control method, and the step deviation exceeds the set range, the control unit will determine that the conveying state of the first PCB board is abnormal.

[0047] The control unit uses the preset abnormal conveying trajectory control method to convey the PCB board.

[0048] First, the standard deceleration b s Change to the preset minimum deceleration b min The step length node for the early deceleration is node S43. After the first PCB board triggers the intermediate detection sensor s3, the step length for the section that continues to move forward and reaches node S43 is S u Shorten to ΔS u , ,ΔS u The calculation method is as follows:

[0049]

[0050] If the conveying state of the PCB board with the sudden factor is abnormal, the control unit calls the preset minimum conveying trajectory control method to convey the next PCB board, and gradually increases the acceleration of the next PCB board in the acceleration stage and the deceleration in the deceleration stage.

[0051] The increasing scheme of acceleration and deceleration is:

[0052]

[0053] where a n and b nare the acceleration and deceleration of the nth PCB board produced in the batch after the PCB board with the current sudden factor, a0 and b0 are the acceleration and deceleration of the PCB board with the current sudden factor before changing the acceleration and deceleration mode,

[0054] The influencing factor coefficient k is inversely proportional to the step deviation according to the recorded number of steps of the conveying motor rotation and the standardized step deviation. According to the recorded number of steps of the conveying belt motor rotation and the standardized step deviation, that is, the influence degree of the sudden factor on the conveying efficiency, the convergence speed of the acceleration and deceleration is adjusted in time. If the deviation is too large, the factor coefficient k is reduced accordingly to reduce the convergence speed. Otherwise, the factor coefficient k is increased to improve the convergence speed. The present invention introduces the factor coefficient k in combination with the influence degree of the sudden factor on the conveying efficiency, dynamically adjusts the convergence speed of the acceleration and deceleration of the subsequent PCB board conveying of this batch, and enhances the flexibility of the system.

[0055] If there is no sudden factor when conveying the first PCB board in the control mode of the standard conveying trajectory, the control unit determines that its conveying state is normal according to the step deviation.

[0056] Each time a PCB is transported, the acceleration in the acceleration phase and the deceleration in the deceleration phase are gradually increased until the acceleration of the transport trajectory is equal to the maximum acceleration a. max , deceleration is equal to the maximum deceleration b max The control unit keeps calling the preset maximum conveying trajectory control mode to convey the next PCB board.

[0057] The present invention has error identification and response measures, timely diagnoses abnormal situations and informs operators. Specifically, the control unit starts timing when the PCB board starts to be transported, which is used for error identification and alarm. There are two conditions for judging the timing stop:

[0058] First, under normal circumstances, the control unit stops timing when the intermediate detection sensor s3 is triggered;

[0059] Second, in abnormal situations, the control unit is equipped with a timeout judgment.

[0060] When the timing time exceeds the preset time threshold TimeThreshold_1 and the intermediate detection sensor s3 is not triggered, the control unit determines that the PCB board continues to slip, and the control unit controls the conveying motor to reduce the speed to the minimum deceleration b. min Slow down to the minimum uniform speed, clear the timing time and restart, and continue to move for a period of time to continuously determine whether the timing time exceeds the preset time threshold TimeThreshold_2;

[0061] If the intermediate detection sensor s3 is triggered within the time threshold TimeThreshold_2, the control unit stops timing. If the intermediate detection sensor s3 is not triggered within the time threshold TimeThreshold_2, the control unit controls the conveying motor to stop conveying and reports an error message. When the host computer of the SMT high-speed placement machine receives the error message, the SMT high-speed placement machine stops the current placement machine and alarms, and feeds back the error message to the operator, who then cancels the alarm and resumes normal operation. The time threshold TimeThreshold_1 is set to 3-10s, and the time threshold TimeThreshold_2 is set to 3-10s. In a preferred embodiment, the time threshold TimeThreshold_1 is set to 4-6s, and the time threshold TimeThreshold_2 is set to 4-6s.

[0062] The present invention proposes a more stable and accurate stop plan, which improves the conveying efficiency while eliminating the impact caused by sudden factors.

Claims

1. An automatic and accurate board stopping method for a SMT high-speed placement machine, characterized in that: The following steps are included: The conveyor belt is driven by the conveyor motor to convey the PCB board. The control unit controls the conveyor motor by controlling the number of steps of the conveyor motor. The SMT high-speed placement machine conveys the PCB board stopped at the starting position a1 to the end position a2 specified by the SMT high-speed placement machine through the conveyor belt. Each PCB board goes through the acceleration stage, the uniform speed stage and the deceleration stage in sequence. In the uniform speed stage, the PCB board moves at the set maximum uniform speed V max go ahead, An intermediate detection sensor s3 is provided between the starting position a1 and the end position a2. When the PCB reaches the position of the intermediate detection sensor s3 in the uniform speed stage, the intermediate detection sensor s3 is triggered. The conveying motor for conveying the PCB from the starting position a1 to the intermediate detection sensor s3 needs a standardized step length h1. The number of standardized steps h2 is required for the conveying motor to convey the PCB board from the middle detection sensor s3 to the end position a2. The step node where the PCB board starts to decelerate is set to node SN3. When the PCB board starts to be transported forward from the starting position a1, the control unit starts to count the step length of the conveyor motor driving the conveyor belt. When the intermediate detection sensor s3 is triggered, the control unit records the actual step length h3 of the conveying motor. The control unit compares the standardized step length h1 with the actual step length h3 and obtains the step length deviation. The control unit calculates node SN3 by combining the step size deviation and the standardized step size number h2. The control unit controls the conveying motor to rotate at a specific step length, so that the PCB board continues to rotate at a maximum uniform speed V max The conveying motor is controlled to decelerate at the node SN3 until the speed of the PCB board drops to 0 and the PCB board stops precisely at the end position a2.

2. The automatic and accurate board stopping method of an SMT high-speed placement machine according to claim 1, characterized in that: The control unit is preset with an abnormal conveying trajectory, The control method for abnormal conveying trajectory is to modify the deceleration in the deceleration stage to the minimum deceleration b min , If the step length deviation is greater than the set range, the control unit determines that the conveying state is abnormal. The control unit modifies the deceleration in the deceleration phase to the minimum deceleration b min And in the deceleration stage of conveying the PCB board, the minimum deceleration b min Slow down.

3. The automatic and accurate board stopping method of an SMT high-speed placement machine according to claim 1 or 2, characterized in that: The control unit is preset with a standard conveying trajectory. The control method of the standard conveying trajectory is to use the standard acceleration a in the acceleration stage s Acceleration, in the uniform speed stage, the maximum uniform speed V set based on the specific SMT high-speed placement machine is used max Move forward at a constant speed, and use the standard deceleration b during the deceleration stage s Deceleration, standard acceleration a s and standard deceleration b s is a moderate value determined based on the structure of the conveyor belt; In the batch mounting production process of the SMT high-speed placement machine, if the conveyor belt conveys the first PCB board of this batch, the control unit conveys the PCB board in a control mode of a preset standard conveying trajectory; When the intermediate detection sensor s3 is triggered, the control unit makes a judgment based on the step deviation. If the step deviation is within the set range, it is judged that the conveying state of the first PCB board is normal, and the first PCB board is controlled to be conveyed according to the preset standard conveying trajectory, and continues to be conveyed at the maximum uniform speed V after the first PCB board triggers the intermediate detection sensor s3. max Go forward a step length S u , until reaching node S13, S u The calculation method is Where D m-d is the standardized step length from the intermediate detection sensor s3 to the end position a2, D m-d is a fixed value.

4. The automatic and accurate board stopping method of an SMT high-speed placement machine according to claim 3 is characterized in that: The control unit is preset with an abnormal conveying trajectory, If an unexpected factor occurs when conveying the first PCB board in the control mode of the standard conveying trajectory, and the step deviation exceeds the set range, the control unit determines that the conveying state of the first PCB board is abnormal. The control unit uses the preset abnormal conveying trajectory control method to convey the PCB board. First, the standard deceleration b s Change to the preset minimum deceleration b min The step length node for the early deceleration is node S43. After the first PCB board triggers the intermediate detection sensor s3, the step length for the section that continues to move forward and reaches node S43 is S u Shorten to ΔS u , ΔS u The calculation method is as follows:

5. The automatic and accurate board stopping method of an SMT high-speed placement machine according to claim 4, characterized in that: The control unit is preset with a minimum conveying trajectory, The control method of the minimum conveying trajectory is to use the minimum acceleration a in the acceleration stage. min , the deceleration in the deceleration phase adopts the minimum deceleration b min , minimum acceleration a min and minimum deceleration b min It is the minimum value determined based on the structure of the conveyor belt; When the conveying state of the PCB board due to the sudden factor is abnormal, the control unit calls the preset minimum conveying trajectory control method to convey the next PCB board, and gradually increases the acceleration of the next PCB board in the acceleration stage and the deceleration in the deceleration stage. The increasing scheme of acceleration and deceleration is: where a n and b n are the acceleration and deceleration of the nth PCB board produced in the batch after the PCB board with the current sudden factor, a0 and b0 are the acceleration and deceleration of the PCB board with the current sudden factor before changing the acceleration and deceleration mode, The influence factor coefficient k is based on the recorded number of steps of the conveying motor rotation and the normalized step deviation. The influence factor coefficient k is inversely proportional to the step deviation.

6. The automatic and accurate board stopping method of an SMT high-speed placement machine according to claim 3, characterized in that: The control unit is preset with a maximum conveying trajectory, The maximum conveying trajectory is controlled in such a way that the acceleration in the acceleration phase adopts the maximum acceleration a max , the deceleration in the deceleration stage adopts the maximum deceleration b max , maximum acceleration a max and maximum deceleration b max It is the maximum value determined based on the structure of the conveyor belt; If no sudden factors occur when conveying the first PCB board in the control mode of the standard conveying trajectory, the control unit determines that the conveying state is normal according to the step deviation. Each time a PCB is transported, the acceleration in the acceleration phase and the deceleration in the deceleration phase are gradually increased until the acceleration of the transport trajectory is equal to the maximum acceleration a. max , deceleration is equal to the maximum deceleration b max The control unit keeps calling the preset maximum conveying trajectory control mode to convey the next PCB board.

7. The automatic and accurate board stopping method of an SMT high-speed placement machine according to claim 1, characterized in that: The step length of the conveying motor is counted. If the conveying motor driving the conveyor belt is an open-loop pulse control method, the number of pulses issued by the control unit is recorded. If the conveyor belt is driven by a bus type control method, the control unit records the number of pulses fed back by the encoder or reads the absolute position of the current conveying motor in real time.

8. The automatic and accurate board stopping method of a SMT high-speed placement machine according to claim 1, characterized in that: The conveying track corresponding to the PCB board includes node SN0, node SN1, node SN2, node SN3 and node SN4 in sequence, where N is 1-4. Node SN0 corresponds to the step node starting from the starting position a1, corresponding to the starting position a1; Node SN1 corresponds to the node where acceleration is completed and uniform motion step starts; Node SN2 corresponds to the step length node reaching the position of the intermediate detection sensor s3, that is, the position where the PCB board triggers the intermediate detection sensor s3; Node SN3 corresponds to the step length node for uniform speed completion and deceleration; Node SN4 corresponds to the step length node that reaches the location of the end position a2, corresponding to the end position a2; The node SN0 corresponds to the point SN1 which is the acceleration stage, and the speed of the PCB board increases from 0 to the set uniform speed; Node SN1 to node SN3 corresponds to the uniform speed stage. Node SN3 to node SN4 corresponds to the deceleration stage, during which the speed of the PCB board decreases from the set uniform speed to 0.

9. The automatic and accurate board stopping method of an SMT high-speed placement machine according to any one of claims 1 to 8, characterized in that: The control unit starts timing when the PCB board starts to be transported, and there are two conditions for determining when timing stops: First, under normal circumstances, the control unit stops timing when the intermediate detection sensor s3 is triggered; Second, in abnormal situations, the control unit is equipped with a timeout judgment. When the timing time exceeds the preset time threshold TimeThreshold_1 and the intermediate detection sensor s3 is not triggered, the control unit determines that the PCB board continues to slip, and the control unit controls the conveying motor to reduce the speed to the minimum deceleration b. min Slow down to the minimum uniform speed, clear the timing time and restart, and continue to move for a period of time to continuously determine whether the timing time exceeds the preset time threshold TimeThreshold_2; If the intermediate detection sensor s3 is triggered within the time threshold TimeThreshold_2, the control unit stops timing. If the intermediate detection sensor s3 is not triggered within the time threshold TimeThreshold_2, the control unit controls the conveying motor to stop conveying and reports error information. When the host computer of the SMT high-speed placement machine receives the error information, the SMT high-speed placement machine stops the current placement machine and alarms, and feeds back the error information to the operator, who then cancels the alarm and resumes normal operation. The time threshold TimeThreshold_1 is set to 3-10s, and the time threshold TimeThreshold_2 is set to 3-10s.

10. The automatic and accurate board stopping method of a SMT high-speed placement machine according to claim 9, characterized in that: The time threshold TimeThreshold_1 is set to 4-6s, and the time threshold TimeThreshold_2 is set to 4-6s.

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