Single-blade hedge trimmer retracting detection control method, system and equipment

Abstract

The invention relates to the technical field of hedge trimmer control, in particular to a single-blade hedge trimmer retracting detection control method, system and equipment, and the method comprises the steps: obtaining the load current and rotating speed of each moment in the operation process of a hedge trimmer; recording a plurality of moments before each moment as local time periods of each moment; calculating a first characterization value and a second characterization value at each moment; determining a jamming evaluation value at each moment, and evaluating a jamming state of the hedge trimmer; when the hedge trimmer is in the cutter clamping state, cutter retracting control is conducted on the hedge trimmer. According to the invention, the misjudgment of the cutter clamping state caused by the foreign matter collision phenomenon can be reduced, the evaluation accuracy of the cutter clamping state of the hedge trimmer is improved, and then the cutter retracting detection precision and the cutter retracting effect of the hedge trimmer are improved.

Description

Technical Field

[0001] The present application relates to the technical field of hedge trimmer control, and particularly relates to a method, a system and a device for detecting and controlling the retraction of a single-edge hedge trimmer blade. Background Art

[0002] A hedge trimmer, also known as a hedge pruning machine, is a professional mechanical device for garden maintenance, mainly used for trimming various hedges, shrubs and shaped plants. The plant branches, leaves and trunks are quickly trimmed by a high-speed rotating cutting tool. However, during the trimming process of the hedge trimmer, due to the limitation of the extrusion of branches, the tool is prone to jamming, which affects the continuity and efficiency of trimming.

[0003] When the prior art performs automatic retraction control on a hedge trimmer, it usually uses a fixed rotational speed threshold to judge whether the hedge trimmer is in a jammed state and realizes retraction by reversing. However, in practical applications, the vegetation faced by the hedge trimmer is complex and diverse, and the resistance characteristics during jamming will vary significantly due to different vegetation types. Moreover, when the blade collides with foreign objects, the blade will get stuck and the rotational speed will decrease. Therefore, judging whether there is a jamming phenomenon by a fixed rotational speed threshold will cause misjudgment of the jamming phenomenon, reduce the judgment accuracy of the jammed state of the hedge trimmer, affect the detection accuracy of the retraction of the hedge trimmer, and result in poor retraction effect. Summary of the Invention

[0004] In order to solve the above technical problems, a method, a system and a device for detecting and controlling the retraction of a single-edge hedge trimmer blade are provided to solve the existing problems.

[0005] The solution of the present application to solve the technical problems is to provide a method, a system and a device for detecting and controlling the retraction of a single-edge hedge trimmer blade, including the following steps: In a first aspect, an embodiment of the present application provides a method for detecting and controlling the retraction of a single-edge hedge trimmer blade, the method including the following steps: Obtain the load current and rotational speed at each moment during the operation of the hedge trimmer; record multiple moments before each moment as the local time period of each moment; Perform curve fitting on the rotational speeds at different moments within the local time period, analyze the deviation of the rotational speed at each moment, as well as the change in the number of extreme points on the fitting curve and the fitting degree of the fitting curve, and calculate the first characterization value at each moment; Calculate the second characterization value at each moment based on the change trend of the load current at all moments within the local time period and the offset degree of the load current; Based on the first characterization value and the second characterization value, determine the jamming evaluation value at each moment, evaluate the jamming state of the hedge trimmer; when the hedge trimmer is in a jammed state, perform retraction control on the hedge trimmer.

[0006] Preferably, the fitting degree is measured by goodness of fit, specifically: calculating the goodness of fit of the fitting curve as the fitting degree of the fitting curve.

[0007] Preferably, the calculation of the first characterization value at each moment includes: Calculating the ratio of the rotational speed at each moment to the preset rated no-load rotational speed, denoted as the speed ratio; Obtaining the number of extreme points of the fitting curve and performing a positive mapping on the number; calculating the sum of the result of the positive mapping and the speed ratio; The first characterization value is the ratio of the fitting degree to the sum value.

[0008] Preferably, the deviation degree is measured by the mean absolute deviation, specifically: calculating the mean absolute deviation of the load current at all moments within the local time period as the deviation degree of the local time period.

[0009] Preferably, the calculation of the second characterization value at each moment includes: Performing linear fitting on the load current at all moments within the local time period to obtain the slope of the fitting straight line; calculating the trend strength of the load current at all moments within the local time period; Calculating the product value of the slope and the trend strength; The second characterization value is the ratio of the product value to the deviation degree.

[0010] Preferably, the tool jamming evaluation value is the normalized result of the sum of the first characterization value and the second characterization value.

[0011] Preferably, the evaluation of the tool jamming state of the hedge trimmer includes: if there are consecutive moments when the tool jamming evaluation values are all greater than the preset segmentation threshold, the hedge trimmer is in the tool jamming state; otherwise, it is not in the tool jamming state.

[0012] Preferably, the retraction control of the hedge trimmer includes: when the hedge trimmer is in the tool jamming state, performing retraction control on the blade of the hedge trimmer by the positive and negative pulse method.

[0013] In a second aspect, an embodiment of the present application further provides a single-blade hedge trimmer retraction detection control system, the system includes a memory, a processor, and a computer program stored in the memory and running on the processor, and when the processor executes the computer program, it implements the steps of the single-blade hedge trimmer retraction detection control method described in any one of the above.

[0014] In a third aspect, an embodiment of the present application further provides a single-blade hedge trimmer retraction detection control device, and the process of retraction detection control of the device adopts the implementation of the single-blade hedge trimmer retraction detection control method described in any one of the above.

[0015] The present application has at least the following beneficial effects: By performing curve fitting on the rotational speeds at different times within a local time period in the present application, analyzing the change in the number of extreme points on the fitting curve, the fitting effect of the fitting curve, and the deviation of the rotational speeds at each time, calculating the first characterization value at each time, the beneficial effect lies in considering the process of the smooth decrease in rotational speed within a local time period when the tool jamming phenomenon occurs. When the tool is impacted by foreign objects, the blade will bounce, and then the rotational speed within the local time period shows a fluctuating decrease. By analyzing the fluctuation of the rotational speed within the local time period and the degree of deviation of the rotational speed, the possibility of tool jamming in the hedge trimmer is preliminarily evaluated. Furthermore, by the change trend and deviation degree of the load current at different times within the local time period, calculating the second characterization value at each time, the beneficial effect lies in considering the changes in the load current caused by tool jamming and foreign object impact respectively to further evaluate the possibility of tool jamming in the hedge trimmer, determining the tool jamming evaluation value at each time, and evaluating the tool jamming state of the hedge trimmer. When the hedge trimmer is in the tool jamming state, performing a tool retraction control on the hedge trimmer, the beneficial effect lies in comprehensively evaluating the tool jamming state of the hedge trimmer through the changes in rotational speed and load current, reducing the misjudgment of the tool jamming state caused by foreign object impact, improving the accuracy of evaluating the tool jamming state of the hedge trimmer, and then performing tool retraction control by the positive and negative pulse method, improving the flexibility and practicality of tool retraction control in complex states, and further improving the tool retraction detection accuracy and tool retraction effect of the hedge trimmer. Description of the Drawings

[0016] The following further elaborates on a tool retraction detection and control method for a single - blade hedge trimmer according to the present application with reference to the drawings.

[0017] Figure 1 is the step - flow chart of a tool retraction detection and control method for a single - blade hedge trimmer provided by an embodiment of the present application; Figure 2 is the step - flow chart of a method for obtaining the first characterization value at each time provided by an embodiment of the present application; Figure 3 is the step - flow chart of a method for obtaining the second characterization value at each time provided by an embodiment of the present application. Detailed Embodiments

[0018] In order to make the objectives, technical solutions, and advantages of the present application clearer, the following further elaborates on a tool retraction detection and control method, system, and device for a single - blade hedge trimmer proposed in the present application with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0020] Please refer to Figure 1 , which shows a step flow chart of a single-edge hedge trimmer retraction detection control method provided by an embodiment of the present application. The method includes the following steps: Step 1, obtain the load current and rotational speed at each moment during the operation of the hedge trimmer.

[0021] To obtain the operating state of the hedge trimmer device in real time, by installing an intelligent sensor at the brushless DC motor of the hedge trimmer, when the hedge trimmer device is running, the load current and rotational speed at each moment are collected in real time; In this embodiment, the acquisition time interval of the intelligent sensor is 20 ms. As other implementation manners, the implementer can set it according to the actual situation. Secondly, since it often takes several seconds from the start of the hedge trimmer device to the trimming of vegetation by the hedge trimmer, therefore, the data collected within the first 2 s after the device is started and run is not processed.

[0022] Thus, the load current and rotational speed at each moment during the operation of the hedge trimmer are obtained.

[0023] Step 2, perform curve fitting on the rotational speeds at different moments within a local time period, analyze the deviation of the rotational speeds at each moment, as well as the change in the number of extreme points on the fitting curve and the fitting degree of the fitting curve, and calculate the first characterization value at each moment.

[0024] During the trimming and cutting process of the blade on the hedge trimmer, the blade is easily squeezed by the lateral branches, resulting in an increase in resistance or even stopping, and a jamming phenomenon occurs. Therefore, a certain control method is required to enable the blade to withdraw from the jammed condition and ensure the smoothness of the hedge trimmer trimming process.

[0025] In traditional retraction control algorithms, it often judges whether the motor has a jamming phenomenon based on a fixed rotational speed threshold or load current threshold of the motor. However, during the operation of the hedge trimmer, different tree vegetation often needs to be trimmed, and the toughness, hardness, and thickness of different trees are different, resulting in changes in the rotational speed and load current of the hedge trimmer motor, which will reduce the applicable range of traditional jamming detection and affect the operating efficiency of the hedge trimmer device.

[0026] Secondly, during the process of trimming vegetation with a hedge trimmer, the motor is connected to the blade through a connection structure. The rotation of the motor drives the blade to move back and forth, thereby achieving the trimming of vegetation. Generally, the output power of the motor is constant, that is, the rotation speed of the motor under no-load conditions is constant. When the hedge trimmer is trimming vegetation, affected by the toughness and resistance of the vegetation branches, the rotation speed of the motor decreases. However, during the cutting of vegetation, foreign objects such as stones and metals may appear in the branches. When the blade collides with the foreign object, it will also get stuck, resulting in a decrease in the rotation speed of the motor. Therefore, when the blade collides with the foreign object, it will be misjudged as a knife jamming phenomenon of the hedge trimmer.

[0027] Based on the above analysis, knife jamming mainly occurs when trimming tree branches. The side wall of the blade is squeezed by the tree, increasing the resistance of the blade. As the cutting depth of the blade increases during the squeezing of the tree, the resistance of the blade cutting gradually increases, and the rotation speed of the motor shows a gradually smooth decrease. When the blade collides with a foreign object, affected by the high rotation speed of the blade, the blade will bounce, and the rotation speed of the motor will show a fluctuating decrease. Therefore, by analyzing the change trend of the rotation speed, the first characteristic value is calculated. Among them, the step flow chart of the acquisition method of the first characteristic value at each moment provided by the embodiments of the present application is as Figure 2 shown, specifically including: Multiple moments before each moment are recorded as a local time period; In this embodiment, 50 moments before each moment are recorded as a local time period. As other implementation manners, the implementer can set it according to the actual situation.

[0028] Perform curve fitting on the rotation speeds at all moments within the local time period, and calculate the goodness of fit of the fitting curve; In this embodiment, the least squares method is used for curve fitting. Among them, the calculations of the least squares method and the goodness of fit are both well-known technologies and will not be elaborated here.

[0029] Obtain the number of extreme points of the fitting curve, and perform a positive mapping on the number; In this embodiment, the derivative method is used to obtain the extreme points. Among them, the process of obtaining the extreme points by the derivative method is a well-known technology and will not be elaborated here; secondly, the process of positive mapping is: perform a positive mapping on the number through a logarithmic function. Assume that the number is denoted as M, and take the calculation result as the result of positive mapping, where is a logarithmic function with the natural constant as the base.

[0030] Calculate the ratio of the rotation speed at each moment to the preset rated no-load rotation speed, denoted as the rotation speed ratio; In this embodiment, the preset rated no-load speed is set to 6900 r / min. As an alternative embodiment, the implementer can set it according to the production data of the hedge trimmer equipment.

[0031] Calculate the sum of the result of the positive mapping and the speed ratio, and use the ratio of the goodness of fit to the sum as the first characterization value at each moment. In this embodiment, taking the first characterization value at the

[0032] moment as an example, its calculation process is as follows: where is the first characterization value at the moment, is the goodness of fit at the moment, is the speed ratio at the moment, is the corresponding quantity at the moment,

[0033] is the result of the positive mapping, and

[0034] is the logarithmic function with the natural constant as the base.

[0035] It should be noted that if the hedge trimmer jams, the speed of the motor drops smoothly and the number of extreme points is small, then the goodness of fit is high, the result of the positive mapping is small, and the speed ratio is small, and the larger the obtained first characterization value, the greater the possibility that the hedge trimmer jams at this time; on the contrary, when the blade bounces due to being hit by a foreign object, the speed of the motor fluctuates greatly, the obtained goodness of fit is small, and the degree of speed drop of the motor is small. The speed ratio is relatively higher than that during jamming. Due to the fluctuation during speed drop, the number of extreme points is large, the result of the positive mapping is large, and the obtained first characterization value is small, indicating that the possibility of the hedge trimmer jamming at this time is small.

[0036] During the operation of the hedge trimmer, the electric energy continuously output by the battery in the hedge trimmer is converted by the motor into kinetic energy through the action of the magnetic field to drive the blade to move and realize the trimming process. When the hedge trimmer is operating normally to trim vegetation, the toughness of the branches will generate a certain resistance to the blade, causing a small fluctuation in the load of the motor, so the load current of the motor will also fluctuate slightly accordingly; when the blade of the hedge trimmer is stuck by a branch or other object, the rotational speed of the motor decreases, resulting in a rapid increase in the load current of the motor. If the rotational speed of the motor completely stops, at this time the motor is equivalent to becoming a resistive device, and the current will reach the highest and tend to be stable; when the blade of the hedge trimmer is stuck and bounces due to a collision with a foreign object, since the collision time between the blade and the foreign object is short, the impact on the load current is small, and it will not cause a rapid increase in the load current as in the case of a stuck blade, but only increase the volatility of the load current.

[0037] Based on the above analysis, the second characterization value is calculated through the change of the load current within a local time period. Among them, the flowchart of the steps of the method for obtaining the second characterization value at each moment provided in the embodiments of the present application is as Figure 3 shown, and specifically includes: Perform linear fitting on the load currents at all moments within the local time period to obtain the slope of the fitting straight line; In this embodiment, the least squares method is used for linear fitting. Among them, the least squares method is a well-known technology and will not be elaborated here.

[0038] Calculate the trend intensity of the load currents at all moments within the local time period; In this embodiment, the STL (Seasonal and Trend decomposition using Loess) trend decomposition algorithm is used to calculate the trend intensity. Among them, the calculation of the trend intensity is a well-known technology and will not be elaborated here; the specific process is: decompose the load currents at all moments within the local time period into a trend term and a residual term through the STL trend decomposition algorithm. Then, the calculation formula for the trend intensity is: where is the trend intensity, is the variance of the residual term, is the variance of the trend term and the residual term, is the maximum value function.

[0039] Calculate the mean absolute deviation of the load currents at all moments within the local time period; It should be noted that the calculation of the mean absolute deviation is a well-known technology, and the calculation formula is: where is the mean absolute deviation at the th moment, At the moment, the load current at the moment, At the moment, the average value of the load currents at all moments within the local time period, At the moment, the number of all moments within the local time period.

[0040] Calculate the product value of the slope and the trend strength, and use the ratio of the product value to the mean absolute deviation as the second characterization value for each moment; It should be noted that when the hedge trimmer has a knife jamming phenomenon, the load current of its motor increases rapidly, and the obtained slope and the trend strength are relatively large. After the blade is completely jammed, the motor stops rotating and loses the back electromotive force. The current is only determined by the resistance and the input voltage, and the current stabilizes at the maximum value. Then, the overall deviation of the current decreases relatively, and the larger the obtained second characterization value, the more likely the hedge trimmer is to have a knife jamming situation at this time; on the contrary, when the blade bounces due to being collided by foreign objects, the motor is affected by the load, causing the current to fluctuate greatly, resulting in a relatively small overall trend, a relatively small slope, and a relatively large mean absolute deviation of the load current. The smaller the obtained second characterization value, the less likely the hedge trimmer is to have a knife jamming situation at this time.

[0041] Thus, the second characterization value for each moment is obtained.

[0042] Step 4, based on the first characterization value and the second characterization value, determine the knife jamming evaluation value for each moment, and evaluate the knife jamming state of the hedge trimmer; when the hedge trimmer is in the knife jamming state, perform a retracting control on the hedge trimmer.

[0043] Furthermore, based on the first characterization value and the second characterization value, determine the knife jamming evaluation value, specifically: Use the normalized result of the sum of the first characterization value and the second characterization value as the knife jamming evaluation value for each moment; In this embodiment, the sigmoid function is used for normalization processing. Among them, the sigmoid function is a well-known technology and will not be elaborated here. As other implementation manners, implementers can use other methods of existing technologies, such as the softmax function, etc. This embodiment does not make special restrictions on this.

[0044] It should be noted that the larger the knife jamming evaluation value, the higher the probability that the hedge trimmer has a knife jamming at this time.

[0045] Secondly, in order to more accurately determine whether the hedge trimmer has a stuck knife, an experimental data set is formed by collecting the load current and rotational speed during multiple runs of the hedge trimmer when cutting different trees. Among them, 20% of the data in the experimental data set is when the knife is stuck, 20% is when there is a foreign object collision, and 60% is when cutting normally; Calculate the stuck-knife evaluation value corresponding to each run in the experimental data set, and obtain the optimal segmentation threshold of the stuck-knife evaluation values of all runs. Among them, the segmentation threshold corresponding to the highest accuracy and recall rate of the stuck-knife state evaluation is recorded as the optimal segmentation threshold, and the optimal segmentation threshold is used as the preset segmentation threshold. Thus, the optimal segmentation threshold can effectively distinguish the situations of the stuck knife, foreign object collision, and normal cutting during all runs.

[0046] If there are consecutive multiple moments when the stuck-knife evaluation value is greater than the preset segmentation threshold, the hedge trimmer is in the stuck-knife state; otherwise, it is not in the stuck-knife state; In this embodiment, if there are consecutive 5 moments when the stuck-knife evaluation value is greater than the preset segmentation threshold, the hedge trimmer is in the stuck-knife state; as other implementation manners, the implementer can set it according to the actual situation.

[0047] When it is determined that the hedge trimmer has a stuck knife, the running resistance of the blade increases. By adjusting the torque of the motor, the motor is controlled to move back and forth, so that the blade can withdraw from the stuck position, thereby realizing the retraction operation. Specifically: By controlling the voltage through the positive and negative pulse method, adjusting the pulse period and PWM duty cycle, the running state of the motor can be changed. Thus, the optional interval of the pulse period is set to {2ms, 4ms, 6ms}, and the PWM duty cycle of the motor is {70%, 80%, 90%, 100%}. During the retraction process, in order to improve the flexibility and practicability of the retraction, during the retraction process, the pulse period and PWM duty cycle of the motor drive pulse voltage are randomly selected for combination to realize the retraction process of the hedge trimmer. Among them, the process of controlling the retraction by the positive and negative pulse method is a well-known technology and will not be elaborated here.

[0048] The embodiment of the present application also provides a single-edge hedge trimmer retraction detection control system, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of any one of the above-mentioned single-edge hedge trimmer retraction detection control methods.

[0049] Based on the same inventive concept as the above method, the embodiment of the present application also provides a single-edge hedge trimmer retraction detection control device, and the retraction detection control process of the device adopts the implementation of any one of the above-mentioned single-edge hedge trimmer retraction detection control methods.

[0050] It should be understood that although Figure 1 the steps in the flowchart are shown sequentially according to the indication of the arrows, these steps are not necessarily executed sequentially in the order indicated by the arrows. Unless there is a clear description in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 1 at least a part of the steps in can include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed alternately or in turn with at least a part of other steps or sub-steps or stages of other steps.

[0051] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0052] The above-described embodiments only represent several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation to the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made. Therefore, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application all belong to the protection scope of the technical solution of the present application.

Claims

1. A method for detecting and controlling the tool retraction of a single-edge hedge trimmer, characterized in that, The method includes the following steps: Obtain the load current and rotational speed at each moment during the operation of the hedge trimmer; Denote multiple moments before each moment as the local time period of each moment; Perform curve fitting on the rotational speeds at different moments within the local time period, analyze the deviation of the rotational speed at each moment, as well as the change in the number of extreme points on the fitting curve and the fitting degree of the fitting curve, and calculate the first characterization value at each moment; Calculate the second characterization value at each moment based on the change trend of the load current at all moments within the local time period and the deviation degree of the load current; Based on the first characterization value and the second characterization value, determine the knife jamming evaluation value at each moment, and evaluate the knife jamming state of the hedge trimmer; When the hedge trimmer is in the knife jamming state, perform a retracting control on the hedge trimmer.

2. The single-edge hedge trimmer retraction detection control method according to claim 1, wherein, Measure the fitting degree through the goodness of fit, specifically: Calculate the goodness of fit of the fitting curve as the fitting degree of the fitting curve.

3. A single-edge hedge trimmer retraction detection control method according to claim 1, characterized in that, The calculating the first characterization value at each moment includes: Calculate the ratio of the rotational speed at each moment to the preset rated no-load rotational speed, denoted as the rotational speed ratio; Obtain the number of extreme points of the fitting curve and perform a positive mapping on the number; Calculate the sum value of the result of the positive mapping and the rotational speed ratio; The first characterization value is the ratio of the fitting degree to the sum value.

4. The single-edge hedge trimmer retraction detection and control method according to claim 1, wherein Measure the deviation degree through the mean absolute deviation, specifically: Calculate the mean absolute deviation of the load current at all moments within the local time period as the deviation degree of the local time period.

5. A single-edge hedge trimmer retraction detection control method according to claim 1, characterized in that, The calculating the second characterization value at each moment includes: Perform linear fitting on the load current at all moments within the local time period to obtain the slope of the fitting straight line; Calculate the trend intensity of the load current at all moments within the local time period; Calculate the product value of the slope and the trend intensity; The second characterization value is the ratio of the product value to the deviation degree.

6. The single-edge hedge trimmer retraction detection and control method according to claim 1, wherein, The knife jamming evaluation value is the normalized result of the sum of the first characterization value and the second characterization value.

7. The single-edge hedge trimmer retraction detection control method according to claim 1, wherein The evaluating the knife jamming state of the hedge trimmer includes: If there are consecutive multiple moments where the knife jamming evaluation values are all greater than the preset segmentation threshold, then the hedge trimmer is in the knife jamming state; Otherwise, it is not in the knife jamming state.

8. The single-edge hedge trimmer retraction detection and control method according to claim 1, wherein, The performing a retracting control on the hedge trimmer includes: When the hedge trimmer is in the knife jamming state, perform a retracting control on the blade of the hedge trimmer through the positive and negative pulse method.

9. A single-edge hedge trimmer retraction detection control system, the system comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the steps of a single-edge hedge trimmer retracting detection and control method according to any one of claims 1-8.

10. A single-edge hedge trimmer retraction detection and control device, characterized in that, The process of the retracting detection and control of the device is implemented by using a single-edge hedge trimmer retracting detection and control method according to any one of claims 1-8.

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