Walking motor-based lawn mower robot slip or collision detection method

Abstract

The application discloses a mowing robot slip or collision detection method based on a walking motor, which comprises the following steps: (1) continuously monitoring the walking motor rotating speed of the mowing robot and collecting the working current of the walking motor; (2) judging whether the mowing robot slips or collides by setting a threshold value. The application only relies on the walking motor, and realizes the slip or collision detection of the mowing robot.

Description

Technical Field

[0001] This invention belongs to the field of robotics technology, and specifically relates to a method for detecting slippage or collisions in lawn mowing robots. Background Technology

[0002] As a mechanical tool used to trim lawns, vegetation, and other plants, lawn mowing robots can walk and mow automatically without human intervention. They can also maintain a stable mowing height and quality, effectively saving lawn mowers' working time and reducing a significant amount of human resources. Therefore, they are widely used in the field of lawn mowing technology.

[0003] Currently, lawnmowers lack slip detection capabilities, so when slippage occurs, they are prone to digging holes in place, which can damage the lawn.

[0004] Collision detection is a crucial aspect of safety protection for intelligent lawnmowers. Currently, lawnmowers primarily detect collisions using contact sensors distributed around the robot's body, which presents a cost problem. Summary of the Invention

[0005] The purpose of this invention is to provide a method for detecting slippage or collision of a lawnmower robot based on a walking motor, which relies on the walking motor to detect slippage or collision of the lawnmower robot.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for detecting slippage or collision in a lawnmower robot based on a walking motor includes the following steps:

[0008] (1) Continuously monitor the speed of the walking motor of the lawnmower and collect the working current of the walking motor;

[0009] (2) By setting a threshold, it is determined whether the lawnmower robot slips or collides.

[0010] For slip detection, step (2) includes:

[0011] (211) Calculate the average fluctuation rate of the walking motor speed;

[0012] (212) Take the current value of the walking motor in the previous period of time at the current moment and multiply it by a coefficient to obtain the current reference value;

[0013] (213) Determine the increase or decrease of the slip detection counter based on the average fluctuation rate of the walking motor speed and the current value at the current moment;

[0014] (214) Determine whether to set or clear the slip occurrence flag based on the slip detection counter.

[0015] In step (211), the average volatility is calculated as follows: the sample values ​​collected over a continuous period of time are subtracted from the benchmark value one by one, and then the absolute value is taken. The sum of all the absolute values ​​is then divided by the number of samples, and the result is divided by the benchmark value to obtain the average volatility index.

[0016] In step (212), when the average fluctuation rate of the walking motor speed is greater than a given threshold and the current value at the current moment is greater than the current reference value, the slip detection counter is incremented by 1; otherwise, the slip detection counter is decremented by 1.

[0017] In step (213), when the slip detection counter reaches the upper limit of the given threshold, a slip occurrence flag is set; when the slip detection counter is less than the lower limit of the given threshold, the slip occurrence flag is cleared.

[0018] For collision detection, step (2) includes:

[0019] (221) When the current walking motor speed is detected to be lower than the first speed setting threshold, the current value of the previous period at the current moment is recorded as the reference current for collision detection. When the current speed is detected to be higher than the first speed setting threshold, the collision counter is reduced by 1.

[0020] (222) When the current walking motor speed is detected to be lower than the second speed setting threshold and the current walking motor operating current value is detected to be greater than the set collision detection current threshold, then the collision counter is incremented by 1; otherwise, the collision counter is decremented by 1.

[0021] (223) When the collision counter is greater than the set threshold, a collision occurrence flag is set.

[0022] In steps (221) and (222), the first speed setting threshold and the second speed setting threshold are dynamic thresholds that are automatically calculated based on the current given speed and combined with empirical coefficients.

[0023] The relationship between the first speed setting threshold and the second speed setting threshold is as follows:

[0024] The first speed threshold is set at 50% of the second speed threshold, but not lower than 2;

[0025] The relationship between the second speed setting threshold and the currently given speed is as follows:

[0026] When the current given speed is 0 to 19, the second speed setting threshold is 50% of the current given speed, but not lower than 4.

[0027] When the current given speed is 20-29, the second speed setting threshold is 40% of the current given speed;

[0028] When the current given speed is 30-39, the second speed setting threshold is 30% of the current given speed;

[0029] When the current given speed is 40-79, the second speed setting threshold is 20% of the current given speed;

[0030] When the current given speed is 80-99, the second speed setting threshold is 15% of the current given speed;

[0031] When the current given speed is 100-119, the second speed setting threshold is 10% of the current given speed.

[0032] In step (222), the collision detection current threshold is equal to the reference current value multiplied by an empirical coefficient, which is obtained through experimentation.

[0033] In step (223), when the collision counter is 0, the collision flag is cleared and the current reference value is zeroed to prepare for the next collision detection.

[0034] The principle of this invention is as follows: When the machine slips, the rubber spikes on the wheels cause changes in the operating state of the drive motor, manifesting as unstable motor speed with increased fluctuations and a rise in motor current. Because the drive motor uses speed feedback control, the speed instability is subtle and not obvious; furthermore, instantaneous speed fluctuations caused by accidental interference must be excluded. Although the motor current change is significant, many situations can cause sudden changes in the drive motor current, such as driving into areas with thick grass. Therefore, judging slippage solely based on unstable speed or large current changes can easily lead to missed or false alarms. This invention combines these two aspects, monitoring the unstable speed for a sustained period (slippage is usually a steady-state phenomenon that requires a certain duration, unlike a collision which is transient), and only triggering a slippage alarm when an increase in the current value is observed.

[0035] Beneficial Effects: This invention relies solely on the walking motor to achieve slippage or collision detection for the lawnmower robot. To characterize speed fluctuations, an average volatility index is established. Using this average volatility index also helps filter out occasional speed anomalies and prevent false detections. Furthermore, the invention indirectly measures motor speed by measuring the motor commutation interval, improving the accuracy of motor speed measurement and enabling the identification of less noticeable average speed fluctuations. This invention employs a dynamic threshold method for collision detection. The speed and current change thresholds used for collision detection are dynamically changed, especially the collision current value, which is automatically generated during operation, thus adapting well to system variations. Attached Figure Description

[0036] Figure 1This is a flowchart of the collision detection method for a lawnmower robot based on a walking motor, as described in Example 2. Detailed Implementation

[0037] The present invention will be further explained below with reference to the accompanying drawings and embodiments.

[0038] Example 1

[0039] This embodiment is a method for detecting slippage in a lawnmower robot based on a walking motor, including the following steps:

[0040] (1) Continuously monitor the speed of the walking motor of the lawnmower robot and collect the working current of the walking motor; among them, the motor speed is indirectly measured by measuring the commutation interval of the walking motor.

[0041] (2) Calculate the average volatility of the walking motor speed. The average volatility is calculated by subtracting the benchmark value from the sample values ​​collected over a continuous period of time and then taking the absolute value. Then, sum all the absolute values ​​and divide by the number of samples. The result is then divided by the benchmark value to obtain the average volatility index.

[0042] (3) Take the operating current value of the walking motor a certain period of time before the current moment (e.g., 2 seconds) and multiply it by a coefficient as the current reference value; where the coefficient is 150% to 350%.

[0043] (4) If the average fluctuation rate of the travel motor speed calculated according to step (2) is greater than the given threshold and the current value at the current moment is greater than the current reference value, then the slip detection counter is incremented by 1; otherwise, the slip detection counter is decremented by 1.

[0044] (5) When the slip detection counter reaches the upper limit of the given threshold, a slip occurrence flag is set; when the slip detection counter is less than the lower limit of the given threshold, the slip occurrence flag is cleared. In one embodiment, the slip detection execution interval is set to 100ms. For a continuous 2-second detection process, the upper limit of the given threshold for the slip detection counter is set to 16, and the lower limit of the given threshold is set to 8.

[0045] The following is an example of calculating the average volatility in this embodiment:

[0046] Under normal operating conditions, the walking motor speeds are collected at the following 256 sampling points:

[0047]

[0048] The average of the 256 rotational speeds is calculated as the baseline value, which is 33.4.

[0049] Subtracting the baseline value from each of the 256 speed values ​​above and taking the absolute value of the result, we get:

[0050]

[0051]

[0052] The sum of the absolute values ​​above is 317.56;

[0053] Summing the absolute values ​​and dividing by the number of rotational speed values ​​(256) yields an average absolute error of 1.24. Therefore, the average volatility is: (Average absolute error / Baseline value) * 100% = 3.71%.

[0054] Under slippage operation conditions, the following 256 sampling points were used to collect the walking motor speed:

[0055]

[0056]

[0057] The average of the 256 rotational speeds is calculated as the baseline value, which is 33.93.

[0058] Subtracting the baseline value from each of the 256 speed values ​​above and taking the absolute value of the result, we get:

[0059]

[0060]

[0061] The sum of the absolute values ​​above is: 1108.41

[0062] The sum of absolute values ​​divided by the number of rotational speed values ​​(256) yields an average absolute error of 4.33.

[0063] The average volatility is: (Average absolute value of error / Benchmark value) * 100% = 12.76%

[0064] The average speed fluctuation rate during normal driving is 3.71%, while the average speed fluctuation rate during skidding is 12.76%, showing a clear distinction between the two.

[0065] Example 2

[0066] This embodiment describes a collision detection method for a lawnmower robot based on a walking motor. Figure 1 As shown, it includes the following steps:

[0067] (1) Continuously collect the operating current of the walking motor of the lawnmower;

[0068] (2) Continuously monitor the speed of the walking motor of the lawnmower;

[0069] (3) When the current walking motor speed is detected to be lower than the first speed setting threshold, the current value of the previous period (e.g., hundreds of milliseconds) is recorded as the reference current for collision detection. When the current speed is detected to be higher than the first speed setting threshold, the collision counter is reduced by 1.

[0070] (4) When the current walking motor speed is detected to be lower than the second speed setting threshold and the current walking motor operating current value is detected to be greater than the set collision detection current threshold, then the collision counter is incremented by 1; otherwise, the collision counter is decremented by 1.

[0071] (5) When the collision counter is greater than the set threshold, a collision occurrence flag is set; when the collision counter is 0, the collision flag is cleared and the current reference value is zeroed to prepare for the next collision detection.

[0072] The first and second speed setting thresholds are dynamic thresholds that are automatically calculated based on the current given speed and an empirical coefficient.

[0073] Collision detection current threshold = reference current value * empirical coefficient.

[0074] The experience coefficient is obtained based on the testing method for each model.

[0075] Table 1 provides an example of how to obtain the first speed setting threshold, the second speed setting threshold, and the empirical coefficient.

[0076] Table 1

[0077]

[0078] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for detecting slippage or collision in a lawnmower robot based on a walking motor, characterized in that: Includes the following steps: (1) Continuously monitor the speed of the walking motor of the lawnmower and collect the working current of the walking motor; (2) By setting a threshold, determine whether the lawnmower robot slips or collides; For slip detection, step (2) includes: (211) Calculate the average fluctuation rate of the walking motor speed; (212) Take the current value of the walking motor in the previous period of time at the current moment and multiply it by a coefficient to obtain the current reference value; (213) Determine whether the slippage detection counter increases or decreases based on the average fluctuation rate of the walking motor speed and the current value at the current moment; (214) Based on the slip detection counter, determine whether to set or clear the slip occurrence indicator; For collision detection, step (2) includes: (221) When the current walking motor speed is detected to be lower than the first speed setting threshold, the current value of the previous period at the current moment is recorded as the reference current for collision detection. When the current speed is detected to be higher than the first speed setting threshold, the collision counter is reduced by 1. (222) When the current walking motor speed is detected to be lower than the second speed setting threshold and the current walking motor operating current value is detected to be greater than the set collision detection current threshold, then the collision counter is incremented by 1; otherwise, the collision counter is decremented by 1. (223) When the collision counter is greater than the set threshold, a collision occurrence flag is set.

2. The method for detecting slippage or collision of a lawnmower robot based on a walking motor according to claim 1, characterized in that: In step (211), the average volatility is calculated as follows: the sample values ​​collected over a continuous period of time are subtracted from the benchmark value one by one and then the absolute value is taken. Then, all the absolute values ​​are summed and divided by the number of samples. The result is then divided by the benchmark value to obtain the average volatility index.

3. The method for detecting slippage or collision of a lawnmower robot based on a walking motor according to claim 1, characterized in that: In step (212), when the average fluctuation rate of the walking motor speed is greater than the given threshold and the current value at the current moment is greater than the current reference value, the slip detection counter is incremented by 1; otherwise, the slip detection counter is decremented by 1.

4. The method for detecting slippage or collision of a lawnmower robot based on a walking motor according to claim 1, characterized in that: In step (213), when the slip detection counter reaches the upper limit of the given threshold, a slip occurrence flag is set; when the slip detection counter is less than the lower limit of the given threshold, the slip occurrence flag is cleared.

5. The method for detecting slippage or collision of a lawnmower robot based on a walking motor according to claim 1, characterized in that: In steps (221) and (222), the first speed setting threshold and the second speed setting threshold are dynamic thresholds that are automatically calculated based on the current given speed and combined with empirical coefficients.

6. The method for detecting slippage or collision of a lawnmower robot based on a walking motor according to claim 1 or 5, characterized in that: The relationship between the first speed setting threshold and the second speed setting threshold is as follows: The first speed threshold is set at 50% of the second speed threshold, but not less than 2. The relationship between the second speed setting threshold and the currently given speed is as follows: When the current given speed is 0~19, the second speed setting threshold is 50% of the current given speed, but not lower than 4; When the current given speed is 20~29, the second speed setting threshold is 40% of the current given speed; When the current given speed is 30~39, the second speed setting threshold is 30% of the current given speed; When the current given speed is 40~79, the second speed setting threshold is 20% of the current given speed; When the current given speed is 80~99, the second speed setting threshold is 15% of the current given speed; When the current given speed is 100~119, the second speed setting threshold is 10% of the current given speed.

7. The method for detecting slippage or collision of a lawnmower robot based on a walking motor according to claim 1, characterized in that: In step (222), the collision detection current threshold is equal to the reference current value multiplied by an empirical coefficient, which is obtained through experimentation.

8. The method for detecting slippage or collision of a lawnmower robot based on a walking motor according to claim 1, characterized in that: In step (223), when the collision counter is 0, the collision flag is cleared and the reference current of the collision detection recorded in step (221) is reset to prepare for the next collision detection.

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