PLC-based annular shuttle vehicle S speed curve planning and control method

Abstract

The invention belongs to the field of factory logistics storage, and particularly relates to a PLC-based annular shuttle vehicle S speed curve planning and control method, which comprises the following steps: 1) a WCS system issues a command to an annular shuttle vehicle; meanwhile, according to the path information of the annular shuttle vehicles, it is judged that a certain docking station needs the shuttle vehicles, and a certain annular shuttle vehicle is determined to execute a task; (2) after the annular shuttle vehicle receives the instruction, the annular shuttle vehicle is controlled and operated according to the generated speed curve; (3) in the task execution process of the annular shuttle vehicle, the path state is detected in real time, and vehicle body collision is prevented; (4) in the task execution process of the annular shuttle vehicle, the state of each butt joint platform is monitored; whether the target replacement action is executed or not is judged in real time; and 5) the shuttle vehicle arrives at the target position for docking until the task is completed. According to the invention, by introducing interruption or task change actions, the problem that a traditional annular shuttle vehicle has to continuously run around a loop wire due to a fault of a docking platform is well solved.

Description

Technical Field

[0001] The invention belongs to the field of factory logistics warehousing, and in particular to a PLC-based annular shuttle vehicle S speed curve planning and control method. Background Art

[0002] A circular shuttle is a vehicle that has multiple shuttles running on a circular track at the same time. In the field of warehousing and logistics, circular shuttles are increasingly favored by customers because of their high speed, high efficiency, and strong expansion and upgradeability. They have set new benchmarks in throughput, cycle efficiency, flexibility, and subsequent scalability. In order to reduce costs, most customers will increase the number of shuttles on a circular line as much as possible to improve efficiency. In this case, planning the shuttle's travel speed is the top priority for improving efficiency.

[0003] At present, under the premise of reducing costs, there are generally two ways to plan the walking speed of the circular shuttle:

[0004] 1) Speed ​​control

[0005] 2) S-curve control without feedback

[0006] The first control method has the advantages of low cost, relatively simple application and debugging. However, the disadvantages of this method are:

[0007] ① Because the speed is set according to the distance differential interval, this jump-type speed control will cause the actual operating speed to change due to load changes, which will make the equipment run unsteadily.

[0008] ② In order to leave enough safety distance for large loads, the operating range of each single speed should be appropriately enlarged, which results in too long low-speed operation time when no-load, affecting efficiency.

[0009] Compared with the first control method, the second control method overcomes the problem of unstable equipment operation to a certain extent, but it still has the following shortcomings:

[0010] ①Without the introduction of state feedback, the speed cannot be adjusted in real time. If there is a freeze or sliding situation, the device will still experience jitter and inaccurate positioning problems.

[0011] ② Without interrupting or changing task actions, it is still difficult to achieve higher efficiency.

[0012] At the same time, when the docking station at the target location of the traditional circular shuttle fails or other factors and cannot dock, the shuttle will circle on the loop, which has a great impact on the efficiency of the system. If the task can be interrupted or changed in time, this problem can be well solved. Summary of the invention

[0013] The purpose of the present invention is to provide a control method for planning an S-speed curve that can adjust the speed in real time, interrupt or change the task at will, and interrupt or change the target, so as to improve the accuracy of position control by using more stable speed control, so as to solve the shortcomings of the existing planning of the walking speed of the circular shuttle.

[0014] The technical solution adopted by the present invention to achieve the above-mentioned purpose is: a PLC-based circular shuttle S speed curve planning and control method, comprising the following steps:

[0015] 1) The WCS system sends commands to the circular shuttle via the ground control console PLC; at the same time, based on the path information of the circular shuttle, it determines that a docking station needs a shuttle, and based on the shuttle status and position of each circular shuttle, it determines which circular shuttle performs the task;

[0016] 2) After receiving the command, the circular shuttle generates a speed curve; the circular shuttle is controlled and operated according to the speed curve;

[0017] 3) When the circular shuttle is performing its mission, it detects the path status in real time to prevent collisions of the circular shuttle;

[0018] 4) During the mission, the circular shuttle vehicle monitors the status of each docking station at the same time, and determines in real time whether to execute the target change action;

[0019] 5) The shuttle arrives at the target location and performs docking until the current task is completed.

[0020] The circular shuttle vehicle includes: a vehicle body PLC, a frequency converter, a motor, an encoder, and a barcode scanner;

[0021] The vehicle body PLC is connected to the barcode scanner and the frequency converter respectively, and is used to receive the position and positioning information detected by the barcode scanner; at the same time, the speed curve is planned according to the torque and speed information fed back by the frequency converter;

[0022] The encoder is arranged at the tail of the motor and is used to collect the code disk value of the motor and send it to the frequency converter;

[0023] The frequency converter is used to convert the received code disk value of the motor into torque and speed information, and send it to the vehicle body PLC;

[0024] The barcode scanner is installed on the vehicle body for position detection and positioning, and sends the obtained position and positioning information to the WCS system through the vehicle body PLC and the ground control console PLC;

[0025] The circular shuttle adopts speed closed-loop control, and the PLC plans the speed curve according to the torque and speed information fed back by the motor tail encoder and the frequency converter.

[0026] In step 2), after receiving the instruction, the PLC of the circular shuttle generates a speed curve, which is specifically:

[0027] After receiving the command through the ground control console PLC transfer, the shuttle body PLC analyzes the target address, plans an S-shaped speed curve according to the displacement difference, and starts running, controlling and running the circular shuttle according to the speed curve.

[0028] In step 2), the circular shuttle is controlled and operated according to the speed curve, specifically:

[0029] 2-1) The inverter follows the speed setting value V_ given by the PLC set , output to the motor;

[0030] 2-2) The inverter collects the torque information T_ act and speed information V_ act Real-time feedback to PLC;

[0031] 2-3) When V_ set When the motor speed is 20% or less than the rated value, if the difference between the set speed and the actual speed is ΔV = V_ set -V_ act The value is greater than V set If the speed is 30% of the actual speed, the PLC will increase the torque setting value and control the inverter to run in torque mode until the speed difference ΔV is within V_ set within 30% of

[0032] 2-4) When V_ set When the motor speed is above 20% of the rated value, if the speed difference ΔV = V_ set -V_ act The absolute value of ABS (ΔV) is greater than V_ set If the speed difference ΔV is within 10% of V_ set within 10% of the range.

[0033] The step 3) is specifically:

[0034] In real time, determine whether there are other shuttles blocking the vehicle from executing the task based on the shuttle position value sent by the WCS system; if so, drive away the corresponding circular shuttle; if not, continue to execute the task.

[0035] The step 4) is specifically:

[0036] 4-1) When the shuttle detects that the docking station is unavailable and there is no alternative location, the shuttle determines the nearest available stop based on its current location and speed;

[0037] 4-2) When the docking equipment at the target point cannot perform the docking task, and there is an alternative platform, and the shuttle vehicle has not run to the deceleration point of the platform, the shuttle vehicle automatically changes the target to the alternative platform target position;

[0038] 4-3) When the docking device at the target point cannot perform the docking task and there is an alternative platform, but the shuttle has exceeded the deceleration point of the platform: the shuttle does not perform the target change action, continues to execute the original target action, and sends a change failure message to the WCS system. The WCS re-searches for an alternative platform. If an available platform is found, the target change action is executed; otherwise, if it is not found, the current task is interrupted and an interrupt task instruction is sent to the PLC.

[0039] The step 4-1) is specifically:

[0040] When the vehicle runs at or before the set point, it will choose to stop at the nearest corresponding station;

[0041] Then the distance S from the set point to the platform docking point _dec The minimum distance for the shuttle to actually slow down and stop is:

[0042] S _dec =S _cal +S _f +S _pos

[0043] According to the real-time speed V_ act The calculated distance S _cal ,Right now:

[0044]

[0045] Among them, V _max is the maximum speed of the motor, t _dec_max is the maximum deceleration time, S _f S is the distance traveled by the vehicle body PLC and the inverter in one communication cycle. _pos is the distance the shuttle travels at the positioning speed;

[0046] Minimum distance for deceleration and stopping S _dec With real-time feedback speed V_ act The decrease is a square decrease, then S _dec The minimum value is obtained when running at a set low speed, so that the shuttle can modify the target position to the greatest extent during the movement, that is, determine the nearest stop.

[0047] The present invention has the following beneficial effects and advantages:

[0048] 1. Based on the S speed curve planned by PLC, the present invention combines feedback torque to perform torque control when running at low frequency, and combines speed feedback to perform speed control when running at high frequency. This method makes the output speed of the execution end, that is, the motor, more stable, and makes the equipment run more smoothly.

[0049] 2. On the basis of stable equipment operation, the real-time position measurement and calculation accuracy of PLC are greatly guaranteed in the present invention, especially when the shuttle runs with different loads, the difference in the low-speed positioning process is very small, which improves the overall system efficiency.

[0050] 3. The present invention solves the problem that the traditional circular shuttle has to run around the loop continuously due to the failure of the docking platform by introducing the interruption or modification of the task action. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a schematic diagram of the network configuration of the circular shuttle system of the present invention;

[0052] Figure 2 It is a schematic diagram of the hardware configuration of the shuttle vehicle of the present invention;

[0053] Figure 3 is a flow chart of the overall method of the present invention;

[0054] Figure 4 The speed planning curve and the speed actual curve are the ones without introducing feedback in the embodiment of the present invention;

[0055] Figure 5 A speed planning curve and a speed actual curve are introduced as feedback for the embodiment of the present invention;

[0056] Figure 6 Schematic diagram of the control principle of the circular shuttle system in an embodiment of the present invention. DETAILED DESCRIPTION

[0057] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0058] like Figure 3 As shown in FIG. 1 , it is a flow chart of the overall method of the present invention. The S speed curve planning and control method of the circular shuttle based on PLC of the present invention comprises the following steps:

[0059] 1) The WCS system sends commands to the circular shuttle via the ground control console PLC; at the same time, based on the path information of the circular shuttle, it determines that a docking station needs a shuttle, and based on the shuttle status and position of each circular shuttle, it determines which circular shuttle performs the task;

[0060] 2) After receiving the command through the ground control console PLC, the shuttle body PLC analyzes the target address, plans an S-shaped speed curve according to the displacement difference, and starts running. The circular shuttle is controlled and operated according to the speed curve. The speed planning curve and the actual speed curve without feedback are shown in the figure. Figure 4 As shown in the figure, the speed planning curve and actual speed curve with feedback are as follows: Figure 5 As shown;

[0061] 3) When the circular shuttle vehicle is executing the task, the path status is detected in real time to prevent the circular shuttle vehicle from colliding. In the present invention, it is determined in real time based on the position value of the shuttle vehicle sent by the WCS system whether there are other shuttle vehicles blocking the vehicle from executing the task; if there are, the corresponding circular shuttle vehicle is driven away; if not, the task is continued.

[0062] 4) During the mission, the circular shuttle vehicle monitors the status of each docking station at the same time, and determines in real time whether to execute the target change action;

[0063] Under the premise of stable speed control, the present invention also adds the interruption or modification of the task process, which avoids the problem that a shuttle vehicle in the system keeps circling on the loop line due to a fault in the task terminal equipment, thereby improving the efficiency of the system.

[0064] 5) The shuttle arrives at the target location and performs docking until the current task is completed.

[0065] like Figure 1 The following is a schematic diagram of the network configuration of the circular shuttle system:

[0066] WCS system: responsible for issuing mission instructions

[0067] Ground PLC: Collect the status information of all ground docking stations. Collect the status, speed, location and other information of all shuttle vehicles. Transmit the ground docking station information and shuttle vehicle information.

[0068] Car body PLC: mainly controls the car body operation logic

[0069] like Figure 2 As shown, it is a schematic diagram of the hardware configuration of the shuttle vehicle of the present invention. The circular shuttle vehicle of the present invention includes: a vehicle body PLC, a frequency converter, a motor, an encoder, and a barcode scanner;

[0070] The vehicle body PLC is connected to the barcode scanner and the frequency converter respectively to receive the position and positioning information detected by the barcode scanner; at the same time, the speed curve is planned according to the torque and speed information fed back by the frequency converter;

[0071] The encoder is located at the tail of the motor and is used to collect the motor's code disk value and send it to the inverter;

[0072] The frequency converter is used to convert the received motor code disk value into torque and speed information and send it to the vehicle body PLC;

[0073] The barcode scanner is installed on the vehicle body for position detection and positioning, and sends the obtained position and positioning information to the WCS system through the vehicle body PLC and the ground control console PLC;

[0074] The circular shuttle adopts speed closed-loop control, and the PLC plans the speed curve according to the torque and speed information fed back by the motor tail encoder and the inverter.

[0075] like Figure 3 As shown, in step 2), the circular shuttle is controlled and operated according to the speed curve, specifically:

[0076] 2-1) The inverter follows the speed setting value V_ given by the PLC set , output to the motor;

[0077] 2-2) The inverter collects the torque information T_ act and speed information V_ act Real-time feedback to PLC;

[0078] 2-3) When V_ set When the motor speed is 20% or less than the rated value, if the difference between the set speed and the actual speed is ΔV = V_ set -V_ act The value is greater than V set If the speed is 30% of the actual speed, the PLC will increase the torque setting value and control the inverter to run in torque mode until the speed difference ΔV is within V_ set within 30% of

[0079] 2-4) When V_ set When the motor speed is above 20% of the rated value, if the speed difference ΔV = V_ set -V_ act The absolute value of ABS (ΔV) is greater than V_ set If the speed difference ΔV is within 10% of V_ set within 10% of the range.

[0080] like Figure 4 The curve shown is the planned speed curve, such as Figure 5 The curve shown is the actual running speed curve. It can be seen that after adding feedback, the running stability and followability are greatly improved.

[0081] Step 4), specifically:

[0082] 4-1) When the shuttle detects that the docking station is unavailable and there is no alternative location, the shuttle determines the nearest available stop based on its current location and speed;

[0083] When the vehicle runs at or before the set point, it will choose to stop at the nearest corresponding station;

[0084] Then the distance S from the set point to the platform docking point _dec The minimum distance for the shuttle to actually slow down and stop is:

[0085] S _dec =S _cal +S _f +S _pos

[0086] According to the real-time speed V_ act The calculated distance S _cal ,Right now:

[0087]

[0088] Among them, V _max is the maximum speed of the motor, t _dec_max is the maximum deceleration time, S _f S is the distance traveled by the vehicle body PLC and the inverter in one communication cycle. _pos is the distance the shuttle travels at the positioning speed;

[0089] Minimum distance for deceleration and stopping S _dec With real-time feedback speed V_ act The decrease is a square decrease, then S _dec The minimum value is obtained when running at a set low speed, so that the shuttle can modify the target position to the greatest extent during the movement, that is, determine the nearest stop.

[0090] 4-2) When the docking equipment at the target point cannot perform the docking task, and there is an alternative platform, and the shuttle vehicle has not run to the deceleration point of the platform, the shuttle vehicle automatically changes the target to the alternative platform target position;

[0091] 4-3) When the docking device at the target point cannot perform the docking task and there is an alternative platform, but the shuttle has exceeded the deceleration point of the platform: the shuttle does not perform the target change action, continues to execute the original target action, and sends a change failure message to the WCS system. The WCS re-searches for an alternative platform. If an available platform is found, the target change action is executed; otherwise, if it is not found, the current task is interrupted and an interrupt task instruction is sent to the PLC.

[0092] Embodiment 1:

[0093] like Figure 6 As shown, the current task is to let car No. 3 go to docking station E to pick up the goods.

[0094] During the mission, the shuttle will monitor the status of each docking station (AB C...) at the same time. The conditions for determining whether to change the target are as follows:

[0095] In combination with steps 4-1) to 4-3) in the method of the present invention,

[0096] In step 4-1), this embodiment performs the following steps: When point E cannot perform the docking task due to a fault or other factors, and the task cannot be replaced by another platform: Car No. 3 will interrupt the current task and automatically change the target to the nearest stop ahead (generally the docking point). For example, when the car runs at or before point P2, it will stop at platform B. Among them:

[0097] The distance S from P2 to the docking point of platform B _dec The minimum distance for the shuttle to actually slow down and stop is:

[0098] S _dec =S _cal +S _f +S _pos

[0099] S _cal is the distance calculated based on the real-time speed V_act, calculated as:

[0100]

[0101] Among them, V _max is the maximum speed of the motor, t _dec_max is the maximum deceleration time, S _f S is the distance traveled by the PLC and the inverter in one communication cycle. _pos is the distance the shuttle travels at the positioning speed.

[0102] In this embodiment, when the shuttle detects that the docking station is unavailable and there is no alternative position, the shuttle will determine the nearest available stop based on the current position and speed.

[0103] Because the minimum distance for deceleration and stopping is S _dec As the real-time feedback speed V_act decreases, it decreases in square, so S _dec The minimum value will be obtained when running at a low speed, so that the shuttle can modify the target position to the greatest extent during the movement, thereby improving the system efficiency.

[0104] In step 4-2), this embodiment performs the following steps: When point E cannot perform the docking task due to factors such as failure, and there is an alternative platform, and the shuttle car has not run to the deceleration point of the platform (such as point P2 of platform B): car No. 3 will automatically change its target to the target position of the alternative platform.

[0105] In step 4-3), this embodiment performs the following steps: When point E cannot perform the docking task due to a fault or other factors, and there is an alternative platform, but the shuttle car has exceeded the deceleration point of the platform (such as point P2 of platform B): Car No. 3 will not perform the target replacement action, continue to perform the original target action, and send a replacement failure message to the WCS. The WCS will search for an alternative platform again. If an available platform can be found, the target replacement action will be performed. If not found, the current task will be interrupted and an interrupt task instruction will be sent to the PLC.

[0106] Arrival: The shuttle arrives at the target location and performs docking until the current task is completed.

[0107] In summary, combined with the above embodiments, it can be concluded that the present invention, based on the S speed curve planned by PLC, combines feedback torque to perform torque control when running at low frequency; and combines speed feedback to perform speed control when running at high frequency. This method makes the output speed of the execution end, that is, the motor, more stable, and makes the equipment run more smoothly.

[0108] Those skilled in the art will appreciate that the above are only preferred embodiments of the present invention, and the various embodiments of the present disclosure and / or the features described in the claims may be combined or combined in various ways, even if such combinations or combinations are not explicitly described in the present disclosure. It is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art may still modify the technical solutions described in the aforementioned embodiments, or perform equivalent substitutions on some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

[0109] Although preferred embodiments of the present invention have been described, additional changes and modifications may be made to these embodiments by those skilled in the art once the basic inventive concepts are known. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention. Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. The S-speed curve planning and control method of the circular shuttle based on PLC is characterized by: The following steps are involved: 1) The WCS system sends commands to the circular shuttle via the ground control console PLC; at the same time, based on the path information of the circular shuttle, it determines that a docking station needs a shuttle, and based on the shuttle status and position of each circular shuttle, it determines which circular shuttle performs the task; 2) After receiving the command, the circular shuttle generates a speed curve; the circular shuttle is controlled and operated according to the speed curve; 3) When the circular shuttle is performing its mission, it detects the path status in real time to prevent collisions of the circular shuttle; 4) During the mission, the circular shuttle vehicle monitors the status of each docking station at the same time, and determines in real time whether to execute the target change action; 5) The shuttle arrives at the target location and performs docking until the current task is completed.

2. The PLC-based circular shuttle S speed curve planning and control method according to claim 1 is characterized in that: The circular shuttle vehicle includes: a vehicle body PLC, a frequency converter, a motor, an encoder, and a barcode scanner; The vehicle body PLC is connected to the barcode scanner and the frequency converter respectively, and is used to receive the position and positioning information detected by the barcode scanner; at the same time, the speed curve is planned according to the torque and speed information fed back by the frequency converter; The encoder is arranged at the tail of the motor and is used to collect the code disk value of the motor and send it to the frequency converter; The frequency converter is used to convert the received code disk value of the motor into torque and speed information, and send it to the vehicle body PLC; The barcode scanner is installed on the vehicle body for position detection and positioning, and sends the obtained position and positioning information to the WCS system through the vehicle body PLC and the ground control console PLC; The circular shuttle adopts speed closed-loop control, and the PLC plans the speed curve according to the torque and speed information fed back by the motor tail encoder and the frequency converter.

3. The PLC-based circular shuttle S-speed curve planning and control method according to claim 1 is characterized in that: In step 2), after receiving the instruction, the PLC of the circular shuttle generates a speed curve, which is specifically: After receiving the command through the ground control console PLC transfer, the shuttle body PLC analyzes the target address, plans an S-shaped speed curve according to the displacement difference, and starts running, controlling and running the circular shuttle according to the speed curve.

4. The PLC-based circular shuttle S-speed curve planning and control method according to claim 1 is characterized in that: In step 2), the circular shuttle is controlled and operated according to the speed curve, specifically: 2-1) The inverter follows the speed setting value V_ given by the PLC set , output to the motor; 2-2) The inverter collects the torque information T_ act and speed information V_ act Real-time feedback to PLC; 2-3) When V_ set When the motor speed is 20% or less than the rated value, if the difference between the set speed and the actual speed is ΔV = V_ set -V_ act The value is greater than V set If the speed is 30% of the actual speed, the PLC will increase the torque setting value and control the inverter to run in torque mode until the speed difference ΔV is within V_ set within 30% of 2-4) When V_ set When the motor speed is above 20% of the rated value, if the speed difference ΔV = V_ set -V_ act The absolute value of ABS (ΔV) is greater than V_ set If the speed difference ΔV is within 10% of V_ set within 10% of the range.

5. The PLC-based circular shuttle S-speed curve planning and control method according to claim 1 is characterized in that: The step 3) is specifically: In real time, determine whether there are other shuttles blocking the vehicle from executing the task based on the shuttle position value sent by the WCS system; if so, drive away the corresponding circular shuttle; if not, continue to execute the task.

6. The PLC-based circular shuttle S-speed curve planning and control method according to claim 1 is characterized in that: The step 4) is specifically: 4-1) When the shuttle detects that the docking station is unavailable and there is no alternative location, the shuttle determines the nearest available stop based on its current location and speed; 4-2) When the docking equipment at the target point cannot perform the docking task, and there is an alternative platform, and the shuttle vehicle has not run to the deceleration point of the platform, the shuttle vehicle automatically changes the target to the alternative platform target position; 4-3) When the docking device at the target point cannot perform the docking task and there is an alternative platform, but the shuttle has exceeded the deceleration point of the platform: the shuttle does not perform the target change action, continues to execute the original target action, and sends a change failure message to the WCS system. The WCS re-searches for an alternative platform. If an available platform is found, the target change action is executed; otherwise, if it is not found, the current task is interrupted and an interrupt task instruction is sent to the PLC.

7. The PLC-based circular shuttle S-speed curve planning and control method according to claim 6 is characterized in that: The step 4-1) is specifically: When the vehicle runs at or before the set point, it will choose to stop at the nearest corresponding station; Then the distance S from the set point to the platform docking point _dec The minimum distance for the shuttle to actually slow down and stop is: S _dec =S _cal +S _f +S _pos According to the real-time speed V_ act The calculated distance S _cal ,Right now: Among them, V _max is the maximum speed of the motor, t _dec_max is the maximum deceleration time, S _f S is the distance traveled by the vehicle body PLC and the inverter in one communication cycle. _pos is the distance the shuttle travels at the positioning speed; Minimum distance for deceleration and stopping S _dec With real-time feedback speed V_ act The decrease is a square decrease, then S _dec The minimum value is obtained when running at a set low speed, so that the shuttle can modify the target position to the greatest extent during the movement, that is, determine the nearest stop.

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