Self-propelled equipment and its collision detection method

Abstract

This application discloses a collision detection method for a self-propelled device. The self-propelled device includes a self-propelled motor that drives the wheels to rotate. The collision detection method includes: real-time detection of the current of the self-propelled motor and calculation of the rate of change of the current of the self-propelled motor; real-time detection of the rotational speed of the self-propelled motor and calculation of the rate of change of the rotational speed of the self-propelled motor; and determining whether the self-propelled device has collided based at least on the rate of change of the current and the rate of change of the rotational speed.

Description

[0001] This application claims priority to Chinese Patent Application No. 202110316484.0, filed with the Chinese Patent Office on March 25, 2021, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to a self-propelled device and a collision detection method thereof. Background Technology

[0003] Self-propelled devices, such as intelligent lawnmowers, are automatic lawnmowers that can move autonomously within a certain area and complete the mowing work without requiring prolonged user operation. They are intelligent, convenient, and save labor costs, making them increasingly popular. Self-propelled devices need to sense obstacles and perform corresponding obstacle avoidance maneuvers. Traditional sensing methods often involve a double-layered casing structure with Hall effect sensors installed at the junction. Upon collision, the relative displacement of the casings causes a change in the Hall effect signal, which is used to determine if a collision has occurred. This sensing method increases production costs and device size because it requires adding a casing around or partially around the self-propelled device. Summary of the Invention

[0004] This application provides a low-cost, high-accuracy collision detection method and a corresponding self-propelled device.

[0005] The technical solution adopted in this application is as follows:

[0006] In a first aspect, this application provides a collision detection method for a self-propelled device, the self-propelled device including a self-propelled motor that drives the wheels to rotate, the collision detection method including: real-time detection of the current of the self-propelled motor and calculation of the rate of change of the current of the self-propelled motor; real-time detection of the rotational speed of the self-propelled motor and calculation of the rate of change of the rotational speed of the self-propelled motor; and determining whether the self-propelled device has collided based at least on the rate of change of the current and the rate of change of the rotational speed.

[0007] Furthermore, when the rate of change of the current of the self-propelled motor increases to a first threshold and the rate of change of the rotational speed of the self-propelled motor decreases to a second threshold, a counter value is increased. When the counter value is greater than a third threshold, it is determined that the self-propelled device has collided.

[0008] Furthermore, the collision detection method further includes: detecting the acceleration of the self-propelled device, calculating the change value of the acceleration, and dynamically adjusting the first threshold and the second threshold based on the change value of the acceleration.

[0009] Furthermore, when the change in acceleration increases, the first threshold is decreased and the second threshold is increased.

[0010] Furthermore, the collision detection method further includes: detecting the first acceleration of the self-propelled device in the x-axis direction and the second acceleration in the y-axis direction; calculating the change value of the first acceleration and the change value of the second acceleration respectively; obtaining a composite acceleration change value based on the change value of the first acceleration and the change value of the second acceleration; and determining that the self-propelled device has collided when the composite acceleration change value is greater than a fourth threshold.

[0011] Furthermore, the collision detection method further includes: after the self-propelled device collides, determining the direction of the collision based on the first acceleration and the second acceleration.

[0012] Furthermore, the collision detection method further includes: detecting the acceleration of the self-propelled device; when the rate of change of the current of the self-propelled motor increases to a first threshold and the rate of change of the rotational speed of the self-propelled motor decreases to a second threshold, calculating the change value of the acceleration; if the change value of the acceleration is greater than a fourth threshold, it is determined that the self-propelled device has collided.

[0013] Secondly, this application provides a self-propelled device, comprising: wheels configured to support the self-propelled device and drive it to walk; a self-propelled motor configured to drive the wheels to rotate to achieve self-propelled function; a current detection device configured to measure the current of the self-propelled motor in real time; a speed measuring device configured to measure the rotational speed of the self-propelled motor in real time; and a control module configured to determine whether the self-propelled device has collided; wherein the control module calculates the rate of change of current based on the current measured by the current detection device, calculates the rate of change of rotational speed based on the rotational speed measured by the speed measuring device, and determines whether the self-propelled device has collided based at least on the rate of change of current and the rate of change of rotational speed.

[0014] Furthermore, the control module is further configured to: when the rate of change of the current of the self-propelled motor increases to a first threshold and the rate of change of the rotational speed of the self-propelled motor decreases to a second threshold, increase the value of a counter; when the value of the counter is greater than a third threshold, determine that the self-propelled device has collided.

[0015] Furthermore, the self-propelled device also includes an accelerometer configured to detect the acceleration of the self-propelled device.

[0016] Furthermore, the control module is further configured to: calculate the change value of the acceleration of the self-propelled device based on the acceleration detected by the accelerometer; and dynamically adjust the first threshold and the second threshold based on the change value of the acceleration.

[0017] Furthermore, the control module is further configured to: acquire a first acceleration in the x-axis direction and a second acceleration in the y-axis direction of the self-propelled device from the accelerometer; calculate the change value of the first acceleration and the change value of the second acceleration respectively; obtain a composite acceleration change value based on the change value of the first acceleration and the change value of the second acceleration; and determine that the self-propelled device has collided when the composite acceleration change value is greater than a fourth threshold.

[0018] Furthermore, after determining that a collision has occurred, the control module determines the direction of the collision based on the first acceleration and the second acceleration.

[0019] Furthermore, the self-propelled device further includes an accelerometer configured to detect the acceleration of the self-propelled device; the control module is further configured to: calculate the change value of the acceleration when the rate of change of the current of the self-propelled motor increases to a first threshold and the rate of change of the rotational speed of the self-propelled motor decreases to a second threshold; if the change value of the acceleration is greater than a fourth threshold, then it is determined that the self-propelled device has collided.

[0020] Furthermore, the self-propelled device is an intelligent lawnmower.

[0021] This application achieves high-accuracy collision recognition by combining multiple parameters without adding additional devices. By adjusting the threshold and parameters, it can be applied to various tools and working conditions. Attached Figure Description

[0022] Figure 1 This is a system schematic diagram of an intelligent lawnmower according to an embodiment of this application;

[0023] Figure 2A This is a flowchart of a collision detection method according to an embodiment of this application;

[0024] Figure 2B This is a sub-flowchart of a collision detection method according to an embodiment of this application;

[0025] Figure 3A This is another sub-flowchart of a collision detection method according to an embodiment of this application;

[0026] Figure 3B yes Figure 3A A list of implementation examples of some steps in the flowchart;

[0027] Figure 4A It is a graph showing the change of the mean current value over time within different sampling points;

[0028] Figure 4B It is a graph showing the rate of change of current value over time within different sampling points;

[0029] Figure 5 This is a schematic diagram of the structure of a smart lawnmower according to another embodiment of this application;

[0030] Figure 6 This is a flowchart of a collision detection method according to another embodiment of this application. Detailed Implementation

[0031] The following uses a smart lawnmower as an example to illustrate the collision detection method for self-propelled devices, along with accompanying drawings.

[0032] like Figure 1 As shown, the intelligent lawnmower 100 includes: a power module 24, a control module 25, a detection module 26, a drive module 21, wheels 27, and blades 28. The drive module 21 includes: a cutting drive controller 222 and its drive switch circuit 223, and a cutting motor 221; a self-propelled drive controller 232 and its drive switch circuit 233, and a self-propelled motor 231. The cutting motor 221 drives the working components, such as the blades 28, to achieve the cutting function; the self-propelled motor 231 drives the wheels 27 to rotate, achieving the self-propelled function. When the intelligent lawnmower collides with an obstacle in its direction of travel, the self-propelled motor 231 experiences a decrease in speed while the current increases due to the obstructed movement. Based on this characteristic, the detection module 26 is connected to the self-propelled motor 231 to detect the current and speed of the self-propelled motor 231 in real time, and sends the current and speed of the self-propelled motor 231 to the control module 25. The control module 25 then makes a judgment on whether a collision has occurred based on the changes in the current and speed of the self-propelled motor 231.

[0033] See Figure 2A The basic steps of the collision detection method, as one of the embodiments, are as follows:

[0034] S1: Obtain the current and speed of the self-propelled motor 231.

[0035] S2: Filter and calculate the current and speed respectively to obtain the rate of change of current and the rate of change of speed.

[0036] S3: Collision identification is performed based on the rate of change of current and the rate of change of rotation speed.

[0037] Since collision detection is performed continuously during the operation of the self-propelled equipment, the above basic steps are also continuously repeated.

[0038] In step S1, the detection module 26 acquires the current and speed of the self-propelled motor 231. For example, the detection module 26 includes a current-sensing resistor connected in series with the self-propelled motor 231 to sample the current flowing through the self-propelled motor 231. In one embodiment, the self-propelled motor 231 is a sensor motor, including a Hall sensor, and the real-time speed of the self-propelled motor 231 can be calculated based on the output change frequency of the Hall sensor. In another embodiment, the self-propelled motor 231 is a sensorless motor, including a back EMF detection unit, and the real-time speed of the self-propelled motor 231 can be calculated based on the frequency of the back EMF zero-crossing point. This application does not limit the type of self-propelled motor 231, nor does it limit the method of measuring the current and speed of the self-propelled motor 231. The detection module 26 samples the current and speed of the self-propelled motor 231 at predetermined intervals (e.g., a sampling frequency of 20 Hz and a predetermined time interval of 50 ms). The detection module 26 is connected to the control module 25 and transmits the sampled current and speed of the self-propelled motor 231 to the control module 25.

[0039] In step S2, the control module 25 filters the latest n current and speed data of the self-propelled motor 231 to obtain the rate of change of both at a preset number of sampling points n. In one embodiment, taking the first-order RC filtering of the current data as an example, the specific formula is:

[0040]

[0041] In the above formula, t represents the current time, and n represents the number of sampling points. This represents the sum of the cumulative sampled values ​​of the current value I within the sampling point n at the current time t. It is the sum of the cumulative sampled values ​​of the current I within the sampling points n at the previous time t-1. t Let I be the current value at the current time t. This represents the average value of the current I within the sampling points n at the previous time t-1. In other words, as time progresses, this filtering algorithm subtracts the average value of the sampling points n from the sum of accumulated sampled values, adds the current sampled value, and repeats this process forward. Furthermore, based on the current sampled value and the average value of the sampling points n from the previous time, the relative rate of change ΔI of the current value I at sampling points n can be calculated. The specific formula is:

[0042]

[0043] The above method is an example of processing the current data of the self-propelled motor 231 using a first-order RC filter. It can also be applied to process the speed data of the self-propelled motor 231 to obtain the relative rate of change Δω of the speed ω of the self-propelled motor 231 under the number of sampling points n. The above formulas and algorithms are just examples, and this application does not limit the specific algorithm used in the filtering process.

[0044] In step S3, the control module 25 performs collision identification based on the relative rate of change of the current and speed of the self-propelled motor 231. Specifically, the control module 25 can preset some thresholds, such as a first threshold, a second threshold, etc., and compare the real-time relative rate of change of the current and speed of the self-propelled motor 231 with these thresholds. If the current increases to a certain extent while the speed decreases to a certain extent, a collision judgment is made. Specifically, in one embodiment, the collision identification algorithm can be as follows: Figure 2B The flowchart is shown. After the intelligent lawnmower 100 is turned on, the counter c is initialized to an initial value of 0, as shown in step 201. During the operation of the intelligent lawnmower 100, as described in S1, the current and speed data of the self-propelled motor 231 are continuously collected, and as described in S2, the current change rate and speed change rate are repeatedly calculated and updated. That is, the current change rate ΔI and speed change rate Δω will be continuously updated during the cycle, as shown in step 202. Each time a new set of current change rate ΔI and speed change rate Δω is obtained, a judgment is made. In step 203, it is judged whether the current change rate ΔI is greater than the first threshold Th1 and whether the speed change rate Δω is less than the second threshold Th2 (the second threshold Th2 is a negative value, and the more the speed decreases, the smaller Δω becomes): when the current change rate ΔI or the speed change rate Δω does not reach the threshold, that is, when the current change rate ΔI is less than or equal to the first threshold Th1 or the speed change rate Δω is greater than or equal to the second threshold Th2, the process jumps to step 201: the counter c is reset to zero and the next cycle begins. If and only if both the rate of change of current ΔI and the rate of change of speed Δω reach a threshold (i.e., the rate of change of current ΔI is greater than the first threshold Th1 and the rate of change of speed Δω is less than the second threshold Th2), the process jumps to step 204: the counter c value is increased. After increasing the counter c value in step 204, the process proceeds to step 205 to determine if the counter c value is greater than the third threshold Th3. If the counter c value is less than or equal to the third threshold Th3, the process jumps to step 202: the current rate of change ΔI and the rate of change of speed Δω are updated, and the next cycle begins. If the counter c value is greater than the third threshold Th3, a collision is determined to have occurred. After a collision is identified, the control module 25 can control the machine operation according to the post-collision strategy, which will not be detailed here. In this detection process, the counter c is used to accumulate the number of times the current increases and the speed decreases, reducing false alarms and improving the accuracy of collision detection. At the same time, since no additional devices are added, only the original parameters of the self-propelled motor 231 are used, the cost is extremely low and it is easy to promote.

[0045] It is worth noting that the first threshold Th1, the second threshold Th2, and the third threshold Th3, including parameters such as the number of sampling points n and the change in counter c, can be adjusted and changed according to different tools and working conditions. These parameters can be determined through extensive experiments during tool manufacturing and pre-stored in the control program, or they can be stored as variables in the control program and adjusted in real-time / dynamically based on real-time parameters during tool operation. For example, compared to an indoor intelligent sweeper, an intelligent lawnmower faces greater friction when moving normally on grass; correspondingly, its first threshold Th1 is higher, while its second threshold Th2 is lower. As another example, the filtering results of the current of the self-propelled motor 231 of the intelligent lawnmower 100 when selecting different numbers of sampling points n (e.g., n = 2, 8, and 32 samples) are as follows: Figures 4A-4B As shown. Figure 4A This is a graph showing the change of the mean current value I within the sampling point n over time when n is 2, 8, and 32.

[0046] Figure 4B This is a graph showing the rate of change of current ΔI over time within the sampling point n when n is 2, 8, and 32. Based on... Figures 4A-4B The experimental results show that the larger the number of sampling points n, the slower the tracking effect, meaning the mean value of the current I changes more slowly within the sampling points n. However, the integration effect is more significant, meaning the rate of change of current ΔI within the sampling points n is larger. In the experiment, different sampling point numbers n (n = 2, 8, 16, 32) were selected. The changes in the filtering results of the self-propelled motor 231 of the intelligent lawnmower 100 were similar to those of the current, and will not be elaborated here. In specific implementation, the number of sampling points for detecting current changes and the number of sampling points for detecting speed changes do not need to be the same; they can be selected based on a combination of the significance of the changes and the computational load. For example, after testing the intelligent lawnmower 100, the number of sampling points for detecting current changes was selected as n = 32, while the number of sampling points for detecting speed changes was selected as n = 16.

[0047] In one embodiment, the counter c is not only used to simply record the number of times both the real-time current change rate ΔI and the speed change rate Δω reach the threshold, but can also reflect the proportion of the current change rate ΔI and the speed change rate Δω and / or the specific values ​​of the current change rate ΔI and the speed change rate Δω by adjusting the change in the counter c, such as... Figures 3A-3B As shown. Figure 3A and Figure 2BThe difference lies in that when the rate of change of current ΔI or the rate of change of rotational speed Δω does not reach the threshold, i.e., the rate of change of current ΔI is less than or equal to the first threshold Th1 or the rate of change of rotational speed Δω is greater than or equal to the second threshold Th2, the process jumps to step 306: the counter c decreases, and a new cycle begins. Specifically, the amount of change in the counter c increment in step 304 and the counter c decrement in step 306 can be found in [reference needed]. Figure 3B Examples in the table. Example 1 is... Figure 2B The described process is as follows: In Example 2, when both the rate of change of current ΔI and the rate of change of speed Δω reach the threshold (i.e., the rate of change of current ΔI is greater than the first threshold Th1 and the rate of change of speed Δω is less than the second threshold Th2), the counter c increases by 3 in step 304. When the rate of change of current ΔI is less than or equal to the first threshold Th1 and the rate of change of speed Δω is less than the second threshold Th2, the counter c decreases by 1 in step 306 (counter c is greater than or equal to 0). When the rate of change of current ΔI is greater than the first threshold Th1 and the rate of change of speed Δω is greater than or equal to the second threshold Th2, the counter c decreases by 2 in step 306 (counter c is greater than or equal to 0). When neither the rate of change of current ΔI nor the rate of change of speed Δω reaches the threshold, the counter c returns to zero. Therefore, the weights of the rate of change of current and the rate of change of speed can be adjusted by setting the amount of change in counter c. In Example 3, the change in counter c is variable and reflects the magnitude of the change rate. For example, when both the current change rate ΔI and the speed change rate Δω reach a threshold (i.e., the current change rate ΔI is greater than the first threshold Th1 and the speed change rate Δω is less than the second threshold Th2), the increment of counter c in step 304 is equal to the sum of the absolute values ​​of the current change rate ΔI and the speed change rate Δω. When the current change rate ΔI is less than or equal to the first threshold Th1 and the speed change rate Δω is less than the second threshold Th2, the absolute value of counter c is decreased by the current change rate ΔI in step 306 (counter c is greater than or equal to 0). When the current change rate ΔI is greater than the first threshold Th1 and the speed change rate Δω is greater than or equal to the second threshold Th2, the absolute value of counter c is decreased by the speed change rate Δω in step 306 (counter c is greater than or equal to 0). When neither the current change rate ΔI nor the speed change rate Δω reaches a threshold, counter c is reset to zero. Therefore, by setting the change in counter c, the magnitude of the change rate can be accumulated. Besides the examples above, there are many other ways to set the change in counter c, such as combining Example 2 with Example 3, which will not be detailed here. Customizing the change in counter c allows this collision detection method to be better applied to different tools and / or operating conditions, improving the accuracy of collision detection.

[0048] In one example, the values ​​of the first threshold Th1 and the second threshold Th2 differ depending on the operating direction of the intelligent lawnmower 100. Typically, when the intelligent lawnmower 100 is moving forward, the absolute values ​​of the first threshold Th1 and the second threshold Th2 (negative values) are at their maximum, used to detect collisions from the forward direction. When the intelligent lawnmower 100 turns left or right, the absolute values ​​of the first threshold Th1 and the second threshold Th2 (negative values) are slightly lower, used to detect collisions from the left or right side. When the intelligent lawnmower 100 is moving backward, the absolute values ​​of the first threshold Th1 and the second threshold Th2 (negative values) are at their minimum, used to detect collisions from the backward direction. Therefore, when the intelligent lawnmower 100 changes its operating direction, it also simultaneously switches to the corresponding first threshold Th1 and second threshold Th2. The values ​​of the first threshold Th1 and the second threshold Th2 change at different operating speeds because the rotational speed and current of the self-propelled motor 231 differ at different speeds, resulting in different rates of change for the same collision force. Therefore, the intelligent lawnmower 100 uses the corresponding first set of first thresholds Th1 and Th2 at the first operating speed; and uses the corresponding second set of first thresholds Th1' and Th2' at the second operating speed. When the first operating speed is greater than the second operating speed, the first set of first thresholds Th1 is greater than the second set of first thresholds Th1', and the first set of second thresholds Th2 is less than the second set of second thresholds Th2'. The thresholds are dynamically adjusted in real time according to the operating conditions, resulting in higher collision detection accuracy and reduced omissions and false positives.

[0049] As described above, collisions from the direction of travel of the intelligent lawnmower 100 can be detected based on the current and rotational speed of the self-propelled motor 231. To detect collisions from directions other than the direction of travel, such as a side collision while the intelligent lawnmower 100 is moving forward, the intelligent lawnmower 100 may also include an accelerometer 29, and the readings of the accelerometer 29 are used to assist in determining whether a collision has occurred and the direction of the collision. Figure 5 As shown, for ease of description, Figure 5 The document also defines the x-axis, y-axis, and z-axis of the accelerometer 29 and the forward, backward, left, and right directions of the intelligent lawnmower 100. The specific process for collision detection using acceleration is as follows... Figure 6As shown, in step 601, accelerometer 29 is used to acquire the acceleration in the x-axis and y-axis directions of the intelligent lawnmower 100. In fact, common accelerometers are triaxial accelerometers, such as those used in microelectromechanical systems (MEMS), which can provide acceleration in the x-axis, y-axis, and z-axis directions. However, considering that most collisions during the movement of the device originate from the front-back, left-right, and right directions, only the acceleration in the x-axis and y-axis directions needs to be acquired. In step 602, the synthetic acceleration change value 'a' is obtained through median filtering and / or average filtering. Specifically, the difference between the current acceleration value in the x-axis direction and the mean or median of the acceleration in the x-axis direction within the sampling points n can be defined as Δx, and the difference between the current acceleration value in the y-axis direction and the mean or median of the acceleration in the y-axis direction within the sampling points n can be defined as Δy. The synthetic acceleration change value 'a' is defined as Δx. 2 +Δy 2 The synthesized acceleration change value 'a' represents the superposition of the acceleration changes along the two axes. It is understandable that other filtering and synthesis calculation methods can also be used. In step 603, the synthesized acceleration change value 'a' is compared to the fourth threshold Th4. If 'a' is less than or equal to the fourth threshold Th4, it is determined that no collision has occurred, and the process jumps to step 601 to continue the loop. If 'a' is greater than the fourth threshold Th4, the process jumps to step 604, where a collision is determined, and the direction of the object causing the collision is determined based on the acceleration along the x-axis and y-axis. For example, when the acceleration along the x-axis is positive, it is determined that the self-propelled device was impacted by an object located in the opposite direction of the x-axis, i.e., in front; when the acceleration along the x-axis is negative, it is determined that the self-propelled device was impacted by an object located in the positive direction of the x-axis, i.e., behind. When the acceleration along the y-axis is positive, it is determined that the self-propelled device was impacted by an object located in the opposite direction of the y-axis, i.e., to the left; when the acceleration along the y-axis is negative, it is determined that the self-propelled device was impacted by an object located in the positive direction of the y-axis, i.e., to the right.

[0050] Acceleration-based collision detection can supplement the collision detection using the current and rotational speed of the self-propelled motor 231 in the previous embodiment. That is, when the current-plus-rotational-speed method detects a collision, it is considered a collision in the direction of travel; if the current-plus-rotational-speed method does not detect a collision, but the acceleration method does, it is considered a collision and the collision direction is calculated using acceleration. Furthermore, the two sets of judgment criteria can be superimposed to improve the accuracy of collision detection and reduce false alarms. Specifically, when the rate of change of the current ΔI of the self-propelled motor 231 is greater than the first threshold Th1 and the rate of change of the rotational speed Δω of the self-propelled motor 231 is less than the second threshold Th2, the composite acceleration change value a of the intelligent lawnmower 100 is calculated. When the composite acceleration change value a is greater than the fourth threshold Th4, it is determined that the intelligent lawnmower 100 has collided; when the composite acceleration change value a is less than or equal to the fourth threshold Th4, it is considered that no collision has occurred. Alternatively, when the resultant acceleration change value 'a' of the intelligent lawnmower 100 is greater than the fourth threshold Th4, the current change rate ΔI of the self-propelled motor 231 is verified. If the current change rate ΔI is greater than the first threshold Th1, then the intelligent lawnmower 100 is determined to have collided; if the current change rate ΔI is less than or equal to the first threshold Th1, then it is considered that no collision has occurred. Alternatively, when the resultant acceleration change value 'a' of the intelligent lawnmower 100 is greater than the fourth threshold Th4, the rotational speed change rate Δω of the self-propelled motor 231 is verified. If the rotational speed change rate Δω is less than the second threshold Th2, then the intelligent lawnmower 100 is determined to have collided; if the rotational speed change rate Δω is greater than the second threshold Th2, then it is considered that no collision has occurred.

[0051] In one embodiment, the first threshold Th1 and the second threshold Th2 can be dynamically adjusted in real time based on the change value of the synthetic acceleration a. For example, the intelligent lawnmower 100 uses the corresponding first set of first thresholds Th1 and second thresholds Th2 under the first synthetic acceleration change value a1; under the second synthetic acceleration change value a2, it uses the corresponding second set of first thresholds Th1' and second thresholds Th2'; when the first synthetic acceleration change value a1 is greater than the second synthetic acceleration change value a2, the first set of first thresholds Th1 is less than the second set of first thresholds Th1', and the first set of second thresholds Th2 is greater than the second set of second thresholds Th2'. Alternatively, f(ΔI,Δω,a) = αΔI + βΔω + γa is defined, where f(ΔI,Δω,a) is a collision state quantity, the value of which varies with the following parameters: ΔI—current change rate, Δω—rotational speed change rate, a—synthetic acceleration change value. α, β, and γ are coefficients corresponding to each parameter, where α is a positive value, β is a negative value, and γ is a positive value. When the collision state variable f(ΔI,Δω,a) reaches a certain threshold, a collision is determined to have occurred in the intelligent lawnmower 100. By combining the current-plus-speed method and the acceleration method, the shortcomings of a single method are overcome, enabling the self-propelled device to identify collisions from both the running direction and non-running directions, thus improving the collision recognition rate. Multiple verifications and real-time threshold adjustment further enhance the accuracy of collision detection. The self-propelled device in this application is not limited to intelligent lawnmowers; other self-propelled devices, such as intelligent sweepers and intelligent snowplows, are also possible.

Claims

1. A collision detection method for a self-propelled device, the self-propelled device comprising a self-propelled motor for driving wheels to rotate, the collision detection method comprising: The current of the self-propelled motor is detected in real time, and the rate of change of the current of the self-propelled motor is calculated. The rotational speed of the self-propelled motor is detected in real time, and the rate of change of the rotational speed of the self-propelled motor is calculated. The self-propelled device is determined to have collided based at least on the rate of change of the current and the rate of change of the rotational speed. When the rate of change of the current of the self-propelled motor increases to a first threshold and the rate of change of the rotational speed of the self-propelled motor decreases to a second threshold, a counter value is increased. When the counter value is greater than a third threshold, it is determined that the self-propelled device has collided. Detect the acceleration of the self-propelled device and calculate the change in the acceleration. The first threshold and the second threshold are dynamically adjusted based on the change in acceleration.

2. The collision detection method as described in claim 1, wherein: When the change in acceleration increases, the first threshold is decreased and the second threshold is increased.

3. The collision detection method as described in claim 1, further comprising: The first acceleration of the self-propelled device in the x-axis direction and the second acceleration in the y-axis direction are detected. Calculate the changes in the first acceleration and the second acceleration respectively; A composite acceleration change value is obtained based on the change values ​​of the first acceleration and the second acceleration; when the composite acceleration change value is greater than a fourth threshold, it is determined that the self-propelled device has collided.

4. The collision detection method as described in claim 3, further comprising: After the self-propelled device collides, the direction of the collision is determined based on the first acceleration and the second acceleration.

5. The collision detection method as described in claim 1, further comprising: Detect the acceleration of the self-propelled device; When the rate of change of the current of the self-propelled motor increases to a first threshold and the rate of change of the rotational speed of the self-propelled motor decreases to a second threshold, the change value of the acceleration is calculated. If the change value of the acceleration is greater than a fourth threshold, it is determined that the self-propelled device has collided.

6. A self-propelled device, comprising: Wheels are provided to support the self-propelled device and drive it to move. The self-propelled motor is configured to drive the wheels to rotate in order to achieve the self-propelled function; The current detection device is configured to measure the current of the self-propelled motor in real time; The speed measuring device is configured to measure the rotational speed of the self-propelled motor in real time; The control module is configured to determine whether the self-propelled device has collided. The control module calculates the rate of change of current based on the current measured by the current detector, calculates the rate of change of rotational speed based on the rotational speed measured by the speed measuring device, and determines whether the self-propelled device has collided based at least on the rate of change of current and the rate of change of rotational speed. The control module is further configured to: when the rate of change of the current of the self-propelled motor increases to a first threshold and the rate of change of the rotation speed of the self-propelled motor decreases to a second threshold, increase the value of a counter; when the value of the counter is greater than a third threshold, determine that the self-propelled device has collided. An accelerometer is configured to detect the acceleration of the self-propelled device; The control module is further configured to: calculate the change value of the acceleration of the self-propelled device based on the acceleration detected by the accelerometer; and dynamically adjust the first threshold and the second threshold based on the change value of the acceleration.

7. The self-propelled device as described in claim 6, wherein: The control module is further configured to: acquire a first acceleration in the x-axis direction and a second acceleration in the y-axis direction of the self-propelled device from the accelerometer; calculate the change value of the first acceleration and the change value of the second acceleration respectively; obtain a composite acceleration change value based on the change value of the first acceleration and the change value of the second acceleration; and determine that the self-propelled device has collided when the composite acceleration change value is greater than a fourth threshold.

8. The self-propelled device as described in claim 7, wherein: After determining that a collision has occurred, the control module determines the direction of the collision based on the first acceleration and the second acceleration.

9. The self-propelled device as described in claim 6, further comprising: An accelerometer is configured to detect the acceleration of the self-propelled device; the control module is further configured to: calculate the change value of acceleration when the rate of change of the current of the self-propelled motor increases to a first threshold and the rate of change of the rotational speed of the self-propelled motor decreases to a second threshold; if the change value of acceleration is greater than a fourth threshold, it is determined that the self-propelled device has collided.

10. The self-propelled device as described in claim 6, wherein: The self-propelled device is an intelligent lawnmower.

Images