Current-based agv lifting speed control method

Abstract

The present application relates to the technical field of industrial control, and aims to provide a current-based AGV lifting speed control method, which specifically comprises the following contents: in the initialization stage, the servo motor is initialized and set to obtain the total lifting stroke L of the fork arm; in the lifting stage, the actual current C and the current position S of the servo motor are read in real time, the walking proportion of the current position S in the total lifting stroke L of the fork arm is calculated, a calculation formula is selected according to the walking proportion, and the control speed V of the servo motor is calculated, wherein when the walking proportion is less than the no-load proportion, the fork arm is in the no-load state, V = K * S, K is a constant; when the walking proportion is greater than or equal to the no-load proportion, the fork arm is in the load lifting state, V = K / C; and the servo motor is controlled to run at the control speed V in real time. The lifting speed can be adjusted in real time according to the lifting of goods of different weights, so that the maximum work efficiency is achieved.

Description

Technical Field

[0001] This invention relates to the field of industrial control technology, and in particular to a current-based AGV lifting speed control method. Background Technology

[0002] Currently, the lifting speed control methods applied to AGVs are basically based on pre-designed speed formulas. Typically, a mechanical engineer first provides the displacement-force formula for the AGV lifting mechanism, and then a software engineer converts it into a displacement-speed formula for programming implementation. Therefore, the following problems mainly exist:

[0003] 1. Because mechanical structures are usually quite complex and involve many parameters, the displacement and force formulas are often high-order exponential piecewise functions. Software engineers can usually only use piecewise polynomials to fit the actual functions and debug various parameters, which is a huge workload.

[0004] 2. Different AGV models have different maximum loads or different mechanical structures due to upgrades and improvements to the lifting mechanism, resulting in different final force-displacement functions. Therefore, it is difficult for software engineers to use a single algorithm to match multiple different models, leading to high software maintenance costs.

[0005] 3. The pre-designed displacement speed formula, in order to ensure the working stability of the lifting mechanism under maximum load, has relatively conservative parameter settings. In actual lifting of goods of different weights, the speed is the same as under maximum load. This results in the AGV being unable to increase the lifting speed when actually lifting lighter goods, making it difficult to achieve maximum work efficiency. Summary of the Invention

[0006] To address the aforementioned shortcomings, the present invention aims to propose a current-based AGV lifting speed control method. This method eliminates the need for software engineers to fit actual functions using piecewise polynomials and debug various parameters, thus avoiding a huge workload. It also facilitates adaptation to different lifting mechanisms, allowing a single algorithm to be used to match multiple different vehicle models. The software maintenance cost is low, and the lifting speed can be adjusted in real time according to the weight of the goods being lifted, achieving maximum work efficiency.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] During the initialization phase, the servo motor is initialized and the total lifting stroke L of the fork arm is obtained;

[0009] During the lifting phase, the actual current C of the servo motor and the current position S are read in real time. The percentage of the current position S relative to the total lifting stroke L of the fork arm is calculated. Based on the percentage of ...

[0010] Preferably, in the initialization phase, the fork arm is set to move from the lowest point of lifting to the highest point of lifting at a constant speed V1, the positions of the lowest and highest points are recorded, and the total lifting stroke L of the fork arm is calculated.

[0011] Preferably, the empty load ratio is a preset ratio;

[0012] Alternatively, it may include the step of obtaining the unloaded percentage, obtaining the lowest point position of the fork lifting and the contact position of the fork contacting the bottom of the pallet, calculating the unloaded distance between the lowest point position and the contact position, and the percentage of the unloaded distance to the total stroke L is the unloaded percentage.

[0013] Preferably, during the lifting phase, when the walking proportion is greater than 95%, the servo motor is controlled to operate at a preset low speed V. A Run it.

[0014] Preferably, during the lifting phase, a time interval is set to periodically read the actual current C and current position S of the servo motor, and the control speed of the servo motor is calculated based on this data.

[0015] Preferably, before controlling the servo motor to run at the control speed V in real time, a speed judgment and protection step is included: judging the current running speed V of the servo motor. 实 If the difference between the calculated control speed V and the actual control speed V is within the set difference range, then the control speed V = V. 实 ±V 最大阈 value.

[0016] Preferably, the AGV lifting speed control method based on current according to claim 1 is characterized in that: the lifting stage further includes a positioning judgment step: after the forklift stops lifting, it is judged whether the current goods have been lifted to the highest point; if so, one forklift lifting is completed.

[0017] Preferably, when both the left and right forks perform lifting movements simultaneously, the method further includes a control step for synchronous lifting of the left and right forks: calculating the control speed V of the servo motors of the left and right forks respectively. 左 V 右 ; Calculate the average value V = (V左 +V 右 ) / 2; Calculate the travel difference ΔS = (S) / 2 in real time between the left and right forks. 左 -S 右 ), where S 左 S represents the current position of the left fork arm. 右 The current position of the right fork arm; the actual control input speed of the left and right servo motors is compensated based on the average speed and the travel difference. The compensation algorithm is as follows: Left servo motor control speed V 左’ =V±K*ΔS, where V is the speed controlled by the right servo motor. 右’ =V±K*ΔS.

[0018] The technical solution provided by this invention may include the following beneficial effects:

[0019] 1. The algorithm directly simplifies the control of the servo motor speed into an inverse proportional function of the current, thus avoiding the complex implementation of solving high-order exponential equations in a program, and making it easy to unify the working modes of different vehicle models and forklifts.

[0020] 2. It can automatically control and adjust the lifting speed according to the actual weight of the goods lifted by the AGV. The algorithm is simplified, which can greatly improve the efficiency when lifting light objects and improve the stability of the mechanism when lifting heavy objects.

[0021] 3. The existence of the left and right forklift lifting synchronous control method ensures the success rate of forklift operation and can reduce additional losses caused by poor algorithm design. Attached Figure Description

[0022] Figure 1 This is a flowchart of the lifting stage in an AGV lifting speed control method based on current according to the present invention. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0024] like Figure 1 As shown in the figure, one embodiment of the present invention proposes a current-based AGV lifting speed control method, comprising the following steps:

[0025] During the initialization phase, the servo motor is initialized and the total lifting stroke L of the fork arm is obtained;

[0026] During the lifting phase, the actual current C of the servo motor and the current position S are read in real time. The percentage of the current position S relative to the total lifting stroke L of the fork arm is calculated. Based on the percentage of ...

[0027] Furthermore, this invention proposes a current-based AGV lifting speed control method, which fully considers the problems that the algorithm program needs to solve during the lifting motion, and proposes solutions and implementation methods.

[0028] One current-based AGV lifting speed control method adjusts the lifting speed based on the actual current of the servo motor. This adjustment principle is simple and clear, and the speed adjustment is convenient and quick. It eliminates the need for software engineers to use piecewise polynomials to fit the actual function and debug various parameters, avoiding a huge workload. It also facilitates the adaptation to different lifting mechanisms, as a single algorithm can be used to match multiple different vehicle models. The software maintenance cost is low. In addition, the lifting speed can be adjusted in real time according to the weight of the goods being lifted, achieving maximum work efficiency.

[0029] Specifically, the no-load state during the lifting phase refers to the initial stage of lifting, before the fork arm touches the bottom of the pallet. At this point, the speed control method can be set as a linear function of speed. The no-load percentage refers to the proportion of the total travel L from the lowest point of lifting to the bottom of the pallet. When the travel percentage is greater than or equal to the no-load percentage, i.e., the fork arm contacts the bottom of the pallet, the fork arm begins actual lifting with load. At this time, the lifting speed is adjusted based on the actual current of the servo motor.

[0030] To further explain, during the initialization phase, the fork arm is set to move from the lowest point of the lifting to the highest point of the lifting at a constant speed V1. The positions of the lowest and highest points are recorded, and the total lifting stroke L of the fork arm is calculated.

[0031] Furthermore, the positions of the lowest and highest points of the forklift lifting motion (e.g., the height of the lowest / highest points) are recorded for calculation of the total lifting stroke L. This can be achieved using existing methods for calculating the total stroke, which will not be elaborated upon here. The total stroke L helps to clarify the specific acceleration and deceleration positions of the servo motor, as well as to set the specific travel distance of the goods and thus adjust the required lifting control speed of the forklift.

[0032] To further clarify, the no-load percentage is a pre-set percentage; in a specific embodiment, the no-load percentage can be a pre-set percentage, generally referring to about 10% of the total stroke L. At this time, using a linear function as a speed control method in the initial no-load operation phase can efficiently increase the lifting speed and make it reach the working requirements as soon as possible.

[0033] Furthermore, the empty load percentage can be accurately calculated based on actual application scenarios, making it highly adaptable. In a specific embodiment, the method also includes obtaining the empty load percentage by acquiring the lowest point of the fork arm lifting and the contact point of the fork arm contacting the bottom of the pallet, calculating the empty load distance between the lowest point and the contact point, and defining the empty load percentage as the proportion of the empty load distance to the total stroke L.

[0034] To further explain, during the lifting phase, when the walking percentage is greater than 95%, the servo motor is controlled to operate at a preset low speed V. A Run it.

[0035] Furthermore, when the walking percentage exceeds 95%, the fork arm is about to reach its highest point. Before reaching the highest point, set the servo motor's low-speed V... A This can prevent the servo motor from controlling the speed too fast. If it needs to stop suddenly, the inertia of the fork arm lifting is too large, the lifting is unstable, and it may exceed the total stroke L, causing an accident.

[0036] To further explain, during the lifting phase, a time interval is set to periodically read the actual current C and current position S of the servo motor, and the control speed of the servo motor is calculated based on this data.

[0037] Furthermore, periodically reading the actual current of the servo motor is beneficial for monitoring its movement. The ability to arbitrarily set the reading period allows for real-time adjustments to the servo motor's motion, reducing the likelihood of unexpected events.

[0038] In one specific embodiment, the time interval for each timing step is fixed at 20 milliseconds, and one "beat" is one of these time intervals. Assuming the lifting takes a total of 30 seconds, and data is read every 20 milliseconds, a total of 1500 reads are performed, which is 1500 beats.

[0039] To further explain, before the servo motor is controlled to run at the control speed V in real time, a speed judgment and protection step is also included: judging the current running speed V of the servo motor. 实 If the difference between the calculated control speed V and the actual control speed V is within the set difference range, then the control speed V = V. 实 ±V 最大阈值 .

[0040] Furthermore, this is achieved by comparing the current operating speed with the calculated control speed. If the current operating speed V of the servo motor decreases during deceleration... 实 The difference between the calculated control speed V and the actual speed V is more than 5 revolutions per second, or the current operating speed V of the servo motor during acceleration. 实 If the calculated control speed V differs from the actual speed by more than 2 revolutions per second, the servo motor's control speed will be adjusted by adding or subtracting a maximum threshold V from the current operating speed. 最大阈值 Typically, a maximum threshold of 5 revolutions per second can be set for deceleration, and a maximum threshold of 2 revolutions per second for acceleration. Adding a speed protection mechanism can make speed changes during servo motor operation relatively smooth, preventing damage to the equipment from strong vibrations generated by the servo motor during large speed changes.

[0041] To further explain, the lifting phase also includes a positioning judgment step: after the forklift stops lifting, it is determined whether the current goods have been lifted to the highest point; if so, one forklift lift is completed.

[0042] Furthermore, the judgment process can clearly understand the current working status of the forklift, preventing the forklift from stopping prematurely before reaching its highest point, which could lead to cargo loss and personal injury.

[0043] To further explain, when both the left and right forks are performing lifting movements simultaneously, the process also includes a control step for the synchronous lifting of the left and right forks: calculating the control speed V of the servo motors of the left and right forks respectively. 左 V 右 ; Calculate the average value V = (V 左 +V 右 ) / 2; Calculate the travel difference ΔS = (S) / 2 in real time between the left and right forks. 左 -S 右 ), where S 左 S represents the current position of the left fork arm. 右 The current position of the right fork arm; the actual control input speed of the left and right servo motors is compensated based on the average speed and the travel difference. The compensation algorithm is as follows: Left servo motor control speed V 左’ =V±K*ΔS, where V is the speed controlled by the right servo motor. 右’ =V±K*ΔS.

[0044] During the lifting motion, if the load on the pallet supporting the goods is unevenly distributed from left to right, it will result in a large difference in the force on the left and right forks. By controlling the lifting of the left and right forks synchronously, it can be ensured that the lifting height of the left and right forks is consistent, thus preventing the goods from tipping over.

[0045] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A current-based AGV lifting speed control method, characterized in that, Includes the following steps: During the initialization phase, the servo motor is initialized and the total lifting stroke L of the fork arm is obtained; During the lifting phase, the actual current C of the servo motor and the current position S are read in real time. The percentage of the current position S relative to the total lifting stroke L of the fork arm is calculated. Based on the percentage of ... The no-load percentage is the percentage of the total travel L from the lowest point of the lifting fork arm to the bottom of the pallet.

2. The current-based AGV lifting speed control method according to claim 1, characterized in that: During the initialization phase, the fork arm is set to move from the lowest point of the lifting to the highest point of the lifting at a constant speed V1. The positions of the lowest and highest points are recorded, and the total lifting stroke L of the fork arm is calculated.

3. The current-based AGV lifting speed control method according to claim 1, characterized in that: The empty load ratio is a pre-set ratio; Alternatively, it may include the step of obtaining the unloaded percentage, obtaining the lowest point position of the fork lifting and the contact position of the fork contacting the bottom of the pallet, calculating the unloaded distance between the lowest point position and the contact position, and the percentage of the unloaded distance to the total stroke L is the unloaded percentage.

4. The current-based AGV lifting speed control method according to claim 1, characterized in that: In the lifting phase, when the walking proportion is greater than 95%, the servo motor is controlled to run at a pre-set low speed V A .

5. The current-based AGV lifting speed control method according to claim 1, characterized in that: During the lifting phase, a time interval is set to periodically read the actual current C and current position S of the servo motor, and the control speed of the servo motor is calculated based on this data.

6. The current-based AGV lifting speed control method according to claim 1, characterized in that: Before the servo motor is controlled to run at the control speed V in real time, a speed judgment and protection step is further included: judging whether the difference between the current running speed Vact of the servo motor and the calculated control speed V is within a set difference range, and when not within the set difference range, the control speed V = V 实 ± V 最大阈值 .

7. The current-based AGV lifting speed control method according to claim 1, characterized in that: The lifting phase also includes a positioning judgment step: after the forklift stops lifting, it is determined whether the current goods have been lifted to the highest point; if so, one forklift lift is completed.

8. The current-based AGV lifting speed control method according to claim 1, characterized in that: When both the left and right forks are performing lifting movements simultaneously, the control steps for synchronous lifting of the left and right forks also include: calculating the control speed V of the servo motors of the left and right forks respectively. 左 V 右 ; Calculate the average value V = (V 左 +V 右 ) / 2; Calculate the travel difference ΔS between the real-time positions of the left and right forks = (S 左 - S 右 ), where S 左 S represents the current position of the left fork arm. 右 The current position of the right fork arm; the actual control input speed of the left and right servo motors is compensated based on the average speed and the travel difference. The compensation algorithm is as follows: Left servo motor control speed V 左’ =V±K*ΔS, where the right servo motor controls the speed V. 右’ = V±K*ΔS.

Images