Mowing robot and automatic steering calibration method thereof

Abstract

The invention discloses a mowing robot and an automatic steering calibration method thereof, and the method comprises the following steps: controlling a steering wheel to rotate towards a first limit position until the steering wheel reaches the first limit position, and recording a first voltage outputted by at least one linear Hall sensor at the moment; controlling the steering wheel to rotate towards a second limit position until the steering wheel reaches the second limit position, and recording a second voltage output by at least one linear Hall sensor at the moment; according to the first voltage and the second voltage, the mapping relation between the output voltage of the linear Hall sensor and the steering angle is determined or corrected, and corresponding third voltage output by at least one linear Hall sensor when the steering wheel is located right ahead is obtained; and controlling the steering motor to rotate until the voltage output by at least one linear Hall sensor is equal to the third voltage.

Description

Technical Field

[0001] The invention belongs to the field of autonomous operation equipment, and in particular relates to a lawn mowing robot and an automatic steering calibration method thereof. Background Art

[0002] The lawn mowing robot can automatically complete the precise mowing of the lawn, greatly facilitating the user's lawn maintenance, and has a good application prospect. The existing lawn mowing robot includes a top cover, a chassis, and a moving mechanism, wherein the moving mechanism is used to drive the chassis to move along the walking path, generally including wheels and a motor driving the wheels to walk. The chassis is connected to the moving mechanism and is used to carry a blade or motor for cutting the lawn. The top cover is covered on the top of the chassis, which can protect the chassis from damage on the one hand, and also play a role in aesthetics on the other hand.

[0003] The moving mechanism generally includes two left and right driving wheels at the back and a steering wheel at the front. The two driving wheels are controlled by differential steering, and the steering wheel is controlled by a steering motor. Figure 1 As shown, the linear Hall sensor 10 is arranged directly above the square magnet 20, and the square magnet 20 is located directly above the output shaft 40 of the steering motor 30, and the square magnet 20 turns synchronously with the direction of the motor. The steering calibration method of the existing lawn mowing robot is that it first needs to be manually pre-positioned. Specifically, the steering motor needs to be manually rotated to the front before leaving the factory. Because of the error of the magnet itself, the data recorded by all machines are different, so it is necessary to read the position of the manually adjusted magnet first; then record it through the EEPROM in the single-chip computer, and then control it. Otherwise, the motor steering cannot be controlled. Because it needs to be manually positioned in advance, it is very troublesome and the work efficiency is low. At the same time, there are errors in manual alignment, which reduces the accuracy of the steering calibration. Summary of the invention

[0004] The purpose of the present invention is to provide a lawn mowing robot and an automatic steering calibration method thereof to solve the above problems. To this end, the technical solution adopted by the present invention is as follows:

[0005] According to one aspect of the present invention, a method for automatically calibrating the steering of a lawn mower robot is provided, wherein the lawn mower robot comprises a driving wheel and a steering wheel, wherein the steering wheel controls the steering by a steering motor, wherein the lawn mower robot further comprises at least one linear Hall sensor and a permanent magnet, wherein the permanent magnet is arranged on a component that rotates synchronously with an output shaft of the steering motor, and the positions of the at least one linear Hall sensor and the one permanent magnet are arranged so that an output voltage of the at least one linear Hall sensor has a unique mapping relationship with a steering angle of the steering wheel, and the method for automatically calibrating the steering comprises the following steps:

[0006] Controlling the steering wheel to rotate toward a first limit position until the steering wheel reaches the first limit position, and recording a first voltage output by the at least one linear Hall sensor at this time;

[0007] Controlling the steering wheel to rotate toward a second limit position until the steering wheel reaches the second limit position, and recording a second voltage output by the at least one linear Hall sensor at this time;

[0008] Determine or modify the unique mapping relationship according to the first voltage and the second voltage to obtain a third voltage output by the at least one linear Hall sensor corresponding to when the steering wheel is in the front;

[0009] The steering motor is controlled to rotate until the voltage output by the at least one linear Hall sensor is equal to the third voltage.

[0010] In one embodiment, the at least one linear Hall sensor includes two linear Hall sensors, wherein the two linear Hall sensors are located on both sides of a central plane and directly above the motion trajectory of the permanent magnet, wherein the central plane is parallel to the front of the lawn mowing robot, the output shaft of the steering motor is located on the central plane, and the first limit position and the second limit position are symmetrical about the central plane; wherein the distance between the permanent magnet and the linear Hall sensor on the first side is a=2r sin(α / 2), and the distance between the permanent magnet and the linear Hall sensor on the second side is b=2r cos(α / 2), wherein r is the distance from the permanent magnet to the rotation center of the steering motor, and α is the angle between the permanent magnet-the rotation center-the linear Hall sensor on the first side; wherein the ratio of a and b represents the direction of the steering motor.

[0011] In one embodiment, the two linear Hall sensors are respectively arranged at the first extreme position and the second extreme position.

[0012] In one embodiment, when the steering wheel faces straight ahead, the permanent magnet is located on the central plane.

[0013] In one embodiment, the at least one linear Hall sensor includes a linear Hall sensor, which is located directly above the motion trajectory of the permanent magnet, wherein the distance between the permanent magnet and the linear Hall sensor is d=2r sin(α / 2), wherein r is the distance from the permanent magnet to the rotation center of the steering motor, and α is the angle between the permanent magnet-the rotation center-the linear Hall sensor; wherein the d value or the corresponding output voltage of the linear Hall sensor represents the direction of the steering motor.

[0014] In one embodiment, the permanent magnet is located at the first extreme position or the second extreme position.

[0015] In one embodiment, the at least one linear Hall sensor is arranged on a main control board of the lawn mowing robot.

[0016] In one embodiment, the permanent magnet is a circular magnetic steel.

[0017] In one embodiment, the unique mapping relationship is determined by establishing a mapping function or a mapping table.

[0018] In one embodiment, the steering automatic calibration method further includes:

[0019] Before the mowing robot departs from a parking station each time, the steering wheels are automatically calibrated.

[0020] In one embodiment, the steering automatic calibration method further includes:

[0021] When the lawn mowing robot is in a working state, when it is detected that the difference between the first voltage or the second voltage and the first voltage or the second voltage recorded during the last steering automatic calibration is greater than an error threshold, the steering automatic calibration is performed.

[0022] In one embodiment, the lawn mowing robot is controlled to return to the docking station and then perform automatic steering calibration.

[0023] In one embodiment, the modification of the unique mapping relationship includes modifying parameters of the linear Hall sensor.

[0024] According to another aspect of the present invention, a lawn mowing robot is provided. The lawn mowing robot includes a main control board storing a computer program, wherein the main control board implements the steps of the automatic steering calibration method as described above when executing the computer program. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a partial cross-sectional view of a steering wheel assembly of an existing lawn mowing robot, wherein the arrangement structure of a magnetic steel and a linear Hall sensor is shown;

[0026] Figure 2 is a side view of the lawn mowing robot of the present invention;

[0027] Figure 3 yes Figure 2 An exploded view of the steering wheel assembly of the lawn mowing robot is shown;

[0028] Figure 4 is a schematic diagram of the arrangement of the magnetic steel and the linear Hall sensor according to the first embodiment of the present invention;

[0029] Figure 5 is a schematic diagram of the steering detection principle of the first embodiment of the present invention;

[0030] Figure 6 is a schematic diagram of the arrangement of a magnetic steel and a linear Hall sensor according to a second embodiment of the present invention;

[0031] Figure 7 is a schematic diagram of the steering detection principle of the second embodiment of the present invention;

[0032] Figure 8 The figure is a flow chart of the automatic steering calibration method of the lawn mowing robot of the present invention. DETAILED DESCRIPTION

[0033] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings so that the purpose, features and advantages of the present invention can be more clearly understood. It should be understood that the embodiments shown in the accompanying drawings are not intended to limit the scope of the present invention, but are only intended to illustrate the essential spirit of the technical solution of the present invention.

[0034] In the following description, certain specific details are set forth for the purpose of illustrating the various disclosed embodiments to provide a thorough understanding of the various disclosed embodiments. However, those skilled in the relevant art will recognize that the embodiments may be practiced without one or more of these specific details. In other cases, well-known devices, structures, and techniques associated with the present application may not be shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

[0035] References throughout the specification to "one embodiment" or "an embodiment" indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of "in one embodiment" or "in an embodiment" in various places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any manner in one or more embodiments.

[0036] In the following description, in order to clearly show the structure and working mode of the present invention, many directional words will be used for description, but the words "front", "back", "left", "right", "outside", "inside", "outward", "inward", "up", "down", etc. should be understood as convenient terms and should not be understood as restrictive terms.

[0037] like Figure 1-3 As shown, the lawn mowing robot includes a top cover 1, a chassis 2 and a moving mechanism, wherein the moving mechanism is used to drive the chassis 2 to move along the walking path. The chassis 2 is connected to the moving mechanism and is used to carry a blade or a motor for cutting the lawn. The top cover 1 covers the top of the chassis 2, which can protect the chassis from damage on the one hand, and also play a role in aesthetics on the other hand.

[0038] Various functional modules such as energy module, detection module, interaction module, control module (also called main control board) are also installed on the chassis 2. The energy module is configured to provide energy for various operations of the lawn mower robot. The detection module is configured to be at least one sensor for sensing the environmental parameters of the lawn mower robot or its own operating parameters. The interaction module is configured to at least receive control instruction information input by a user, send information that needs to be sensed by the user, communicate with other systems or devices to send and receive information, etc. The main control board usually includes at least one processor and at least one non-volatile memory, in which a pre-written computer program or instruction set is stored, and the processor controls the execution of the movement, work, and other actions of the lawn mower robot according to the computer program or instruction set. The main control board can be a printed circuit board (PCB) or a flexible circuit board (FPC), etc.

[0039] The mobile mechanism generally includes two left and right driving wheels 3 in the front and a steering wheel 4 in the rear. The two driving wheels 3 can be steered by differential control, and the steering wheel 4 can be steered by a steering motor 5. Specifically, the steering motor 5 is fixedly mounted in the seat body 6, and the steering wheel 4 is mounted on the wheel fork 7, and the wheel fork 7 is drivingly connected to the output shaft 51 of the steering motor 5. The seat body 6 includes a base 61 and a cover body 62 located on the top of the base 61, and the base 61 can be connected to the chassis 2 by screws, or connected to the chassis 2 by other means. The cover body 62 covers the top surface of the base 61 and can be clamped with the base 61. In addition, the seat body 6 is provided with a receiving cavity, and the steering motor 5 is mounted in the receiving cavity and the end of its output shaft 51 passes through the cover body 62. The end of the output shaft 51 is fixed with a flange 52. The first gear 53 is fixed (for example, by a spline) on the output shaft 51. The wheel fork 7 includes a fork portion and a rotating shaft 71, and the fork portion is U-shaped, and the steering wheel 4 is mounted between the two arms of the fork portion. The bottom end of the rotating shaft 71 is fixed to the fork and movably penetrates the accommodating cavity of the base 61. The second gear 54 is fixed (for example, through a spline) on the rotating shaft 71 and meshes with the first gear 53. Therefore, the steering motor 5 can drive the steering wheel 4 to steer.

[0040] A first limiting portion 541 is provided on the second gear 54, and a second limiting portion 611 is provided on the base 61 of the seat body 6. The first limiting portion 541 and the second limiting portion 611 cooperate to limit the steering angle range (for example, ±90°) of the steering wheel 4. The steering angle of the steering wheel 4 is usually determined by detecting the output voltage generated by the magnetic steel 9 by a linear Hall sensor (not shown). In the present invention, the magnetic steel 9 is usually eccentrically arranged relative to the output shaft 51 of the steering motor 5, so that the output voltage of the linear Hall sensor has a unique mapping relationship with the steering angle of the steering wheel 4. Therefore, as long as the output voltage of the linear Hall sensor is detected, the steering angle of the steering wheel 4 can be obtained according to the mapping relationship determined in advance. Preferably, the magnetic steel 9 is fixed on a component that rotates synchronously with the output shaft 51 of the steering motor 5. In a specific embodiment, the magnetic steel 9 is fixedly mounted on the flange of the flange 52, for example, by gluing it on the flange of the flange 52, or processing an installation groove on the flange of the flange 52, and then embedding the magnetic steel 9 in the installation groove. The present invention does not limit the installation method of the magnetic steel 9. The size of the flange 52 can be scaled according to actual needs, thereby adjusting the rotation radius of the magnetic steel 9. When the steering wheel assembly is installed on the lawn mower robot, the magnetic steel 9 can be within the effective detection range of the linear Hall sensor. Preferably, the linear Hall sensor 8 can be fixedly installed on the main control board (not shown) of the lawn mower robot to avoid wiring. At this time, the main control board is required to be installed in a position close to the magnetic steel 9.

[0041] How to determine the mapping relationship between the output voltage of the linear Hall sensor and the steering angle of the steering wheel 4 is described in detail below.

[0042] Please refer to Figure 4 , Figure 4 The arrangement structure of the magnetic steel and the linear Hall sensor of the first embodiment of the present invention is shown. In this embodiment, a magnetic steel 9 and two linear Hall sensors 8A and 8B are included. For the convenience of description, it is defined that when the lawn mowing robot walks in a straight line, the direction X of the steering wheel 4 is directly in front; at the same time, a central plane A is defined, and the central plane A is parallel to the front, and the output shaft 51 of the steering motor 5 is located on the central plane A. Usually, the left and right steering limit positions of the steering wheel 4 are mirror-symmetrical about the central plane A. In a specific embodiment, taking the central plane as the starting point (denoted as 0°), the left turn limit angle is 90° (denoted as -90°), and the right turn limit angle is also 90° (denoted as +90°). It should be understood that the limit angle is not limited to ±90°.

[0043] In this embodiment, when the steering wheel 4 faces straight ahead, the magnetic steel 9 is located on the central plane A. The two linear Hall sensors 8A and 8B are respectively arranged on both sides of the central plane. In this embodiment, the two linear Halls are symmetrical about the central plane, for example, the linear Hall sensor 8A is located on the first side (for example, the right side), and the linear Hall sensor 8B is located on the second side (for example, the left side). Ideally, the two linear Hall sensors 8A and 8B are located directly above the motion trajectory of the magnetic steel 9. Since the scale change of the linear Hall sensors 8A and 8B and the magnetic steel 9 on the rotation plane of the magnetic steel 9 is much greater than the height difference between the two in the axial direction, the magnetic steel 9 and the linear Hall sensors 8A and 8B can be regarded as being on the same plane. That is, the distance between the linear Hall sensor and the magnetic steel 9 and the output shaft 51 of the steering motor 5 is regarded as equal.

[0044] With the above structure, when the steering motor is controlled to rotate left and right, the distance between the magnet 9 and the two linear Hall sensors 8A and 8B changes, and the two linear Hall sensors 8A and 8B will output different voltage values. Since the output voltage value of the linear Hall sensors 8A and 8B is linearly related to the distance x to the magnet 9, that is, E=k·x+p, where k and p are linear Hall sensor parameters; therefore, the distance to the magnet 9 can be used to characterize the magnitude of the output voltage value of the linear Hall sensor. For details, please refer to Figure 5 , let the distance from the magnet 9 to the rotation center be r, the distance from the right linear Hall sensor 8A to the rotation center o be l1, the distance from the left linear Hall sensor 8B to the rotation center o be l2, and the angle between the magnet 9-rotation center o-right linear Hall sensor 8A be α, then the distance from the magnet to the right linear Hall sensor 8A is Distance from magnet 9 to left linear Hall sensor 8B The ratio of a to b is different at any two positions of the magnet 9 from the right limit position to the left limit position, so the ratio of a to b can reflect the steering direction of the steering wheel. a =k1·a+p1, the output voltage E of the left linear Hall sensor 8B b =k2·b+p2. Preferably, the two linear Hall sensors are of the same model, that is, the linear Hall sensor parameters k and p are the same to simplify the calculation. Therefore, (E a -p) / (E b That is, the ratio of the output voltages of the linear Hall sensors 8A and 8B minus p can reflect the direction of the steering wheel.

[0045] When the left and right linear Hall sensors 8A and 8B are symmetrical about the center plane, when the magnet is located in the center plane (i.e., the direction of the steering wheel is directly forward), a=b, l1=l2, and α=π / 2, then a / b=1. Based on this setting, it is not necessary to consider the error between the magnets during production, and the direction directly in front of the steering wheel can be determined more conveniently and accurately. Because usually, the consistency of the magnets is relatively low, while the consistency of the linear Hall sensors is relatively high. That is, the errors between different magnets in the same batch cannot be ignored, while the errors between different linear Halls in the same batch, or even between different batches of linear Halls, can be ignored.

[0046] Therefore, when calibrating the steering of the steering wheel, there is no need to manually align the steering wheel 4, but the mowing robot automatically performs it according to a preset program, which improves production efficiency, reduces production costs, and can improve the steering calibration accuracy.

[0047] In order to further simplify the calculation and save computing power, in terms of structure, the two linear Hall sensors 8A and 8B are both arranged directly above the rotation track of the magnetic steel 9. At this time, l1=l2=r, then a=2r sin(α / 2), b=2rcos(α / 2), a / b=tan(α / 2). During the steering process of the steering wheel from the right extreme position to the left extreme position, α changes from 0° to 180°. Therefore, a / b is always different during the steering process of the steering wheel, and the rotation angle of the steering wheel can be inferred from the a / b value. Specifically, when the value of a / b is the smallest (i.e., the output voltage of the right linear Hall sensor 8A is the largest and the output voltage of the left linear Hall sensor 8B is the smallest), it indicates that the steering wheel 4 is at the right limit position; when a / b=1 (the output voltage of the right linear Hall sensor 8A is equal to the output voltage of the left linear Hall sensor 8B), it indicates that the steering wheel 4 is in the front; and when the value of a / b is the largest (i.e., the output voltage of the left linear Hall sensor 8B is the largest and the output voltage of the right linear Hall sensor 8A is the smallest), it indicates that the steering wheel 4 is at the left limit position. It is pointed out here that because the above calculations are all under ideal conditions, that is, the magnetic steel and the Hall are regarded as points and in the same plane, and the two coincide at the limit position, there will be a or b is 0, but in actual use, a and b will only have maximum and minimum values, that is, the output voltages of the two linear Hall sensors 8A and 8B will have maximum and minimum values, and then the ratio of the two is a maximum or minimum value, and it is judged to be at the limit position. These maximum and minimum values ​​are determined in experiments and tests.

[0048] In some embodiments, the technical solution of one magnet and two linear Hall sensors can be used to automatically align and / or correct the front direction of the lawn mowing robot. At this time, the steering control of the steering motor can be achieved by, for example, a magnetic code disk installed inside the motor. Furthermore, since the above scheme can obtain the deviation angle of the motor relative to the initial direction (front), it can be used to verify the control data of the magnetic code disk. Furthermore, for some embodiments, the magnetic code disk can be omitted and the above scheme can be used alone to control the direction of the steering wheel, further reducing costs.

[0049] Please refer to Figure 6 , Figure 6 The arrangement of the magnetic steel and the linear Hall sensor of the second embodiment of the present invention is shown. In this embodiment, a magnetic steel 9 and a linear Hall sensor 8 are included. That is, compared with the first embodiment, the structure of this embodiment is simplified, and only a magnetic steel 9 and a corresponding linear Hall sensor 8 are retained.

[0050] Since the maximum central angle corresponding to the movement trajectory of the magnet is 180°, the voltage value output by the linear Hall sensor 8 is unique at any position within the movement range of the magnet 9, so the absolute value of the voltage output by the linear Hall sensor can be used to characterize the steering of the steering wheel.

[0051] Specifically refer to Figure 7 , let the distance from the linear Hall sensor 8 to the rotation center o be l, the distance from the magnet 9 to the rotation center o be r, the angle between the linear Hall sensor 8-rotation center o-the magnet 9 at the right limit position be α, and the distance from the linear Hall sensor 8 to the magnet 9 at the right limit position be The distance from the linear Hall sensor 8 to the magnet 9 at the left limit position The distance from the linear Hall sensor 8 to the magnetic steel 9 in the middle position is Then, when the output voltage of the linear Hall sensor 8 is E right =k·a+p, the control module of the mowing robot can determine that the steering wheel has rotated to the right to the limit position. left = k·b+p, the control module of the mowing robot can determine that the steering wheel has rotated right to the limit position. mid =k·c+p, the control module of the lawn mower robot can determine that the steering wheel has rotated to the center position (i.e., directly in front). Among them, k and p are linear Hall sensor parameters. Similarly, the mapping relationship between the steering wheel rotation angle and the Hall output voltage can be determined through the characteristics of the linear Hall sensor 8 and a limited number of tests, and then the steering wheel rotation angle can be inferred from the output voltage of the linear Hall sensor 8.

[0052] In order to simplify the calculation and save computing power, the linear Hall sensor 8 is structurally arranged just above the rotation track of the magnetic steel 9 and at the extreme position on one side, for example, at the right extreme position. At this time, the angle between the magnetic steel 9-rotation center o-linear Hall sensor 8 is , then the distance between the linear Hall sensor 8 and the magnetic steel 9 is d=2r sin(α / 2), and the output voltage of the linear Hall sensor 8 is E=2kr sin(α / 2)+p. Since k, r, and p are known parameters, the steering angle of the steering wheel 4 can be inferred from the output voltage of the linear Hall sensor 8. For example, when the output voltage of the linear Hall sensor 8 is the maximum value, it indicates that the steering wheel 4 is at the right extreme position; and when the output voltage of the linear Hall sensor 8 is the minimum value, it indicates that the steering wheel 4 is at the left extreme position.

[0053] According to the mapping relationship between the rotation angle of the steering wheel and the output voltage of the linear Hall sensor 8, even when an error occurs in the linear Hall sensor 8, the control module of the lawn mowing robot can compare the maximum and minimum values ​​of the output voltage of the linear Hall sensor 8, and then re-establish a mapping table based on these maximum values. Then, according to the mapping table, it can automatically move to the middle position for self-startup positioning without manual intervention, thereby greatly improving work efficiency.

[0054] In the above example, the shape of the magnetic steel 9 is not limited. The present invention preferably uses a circular magnetic steel because multiple circular magnetic steels have been used in other positions of the lawn mower robot (such as the emergency stop button, the lift sensor, etc.), and the use of magnetic steels of the same specification is conducive to reducing costs. It should be understood that the magnetic steel 9 can also be other permanent magnets as long as they can be detected by the linear Hall sensor.

[0055] In the above embodiment, the magnetization direction and the polarity direction of the magnetic steel 9 after installation are not limited, as long as they can be compatible with the selected linear Hall sensor.

[0056] In the above embodiment, the positions of the linear Hall sensor and the magnet are not limited, as long as the linear Hall sensor can detect the magnet signal at any point within the rotation range of the steering wheel, and the magnet signals at any two positions are different. Furthermore, since there is a mechanical limit at the extreme rotation position of the steering wheel and the mechanical limit is symmetrical about the center plane, it is not necessary to limit the positions of the magnet and the linear Hall sensor on the horizontal projection plane, that is, when the steering wheel is facing forward, the magnet may not be located on the center plane; the linear Hall sensor may not be symmetrical relative to the center plane, and may not be located at the extreme position corresponding to the rotation of the steering wheel.

[0057] like Figure 8As shown, based on the above embodiment, the automatic steering calibration method of the lawn mowing robot of the present invention may include the following steps:

[0058] 100. Control the steering wheel 4 to rotate toward the first limit position (e.g., the right limit position) until the steering wheel 4 reaches the first limit position, and record the first voltage output by the linear Hall sensor at this time. For example, for the first embodiment, record the first voltage output by the two linear Hall sensors 8A and 8B and For the second embodiment, the first voltage E1 output by the linear Hall sensor 8 is recorded.

[0059] 200. Control the steering wheel 4 to rotate toward the second limit position (e.g., the left limit position) until the steering wheel 4 reaches the second limit position, and record the second voltage output by the linear Hall sensor at this time. For example, for the first embodiment, record the second voltage output by the two linear Hall sensors 8A and 8B and For the second embodiment, the second voltage E2 output by the linear Hall sensor 8 is recorded.

[0060] 300. According to the mapping relationship between the output voltage of the linear Hall sensor 8 and the steering angle of the steering wheel 4, the mapping relationship between the first voltage and the second voltage is determined (for example, when leaving the factory or when used for the first time) and / or corrected (for example, during subsequent use), and the third voltage E3 output by the linear Hall sensor corresponding to when the steering wheel 4 is in the front is obtained. Specifically, according to the linear Hall sensor output voltage formula E=k·x+p, the two equations corresponding to E1 and E2 are combined to determine the two parameters k and p, and then the distance x3 between the linear Hall sensor and the magnetic steel when the steering wheel 4 is in the front is substituted into E=k·x+p to obtain the third voltage E3. Since the distance between the linear Hall sensor and the magnetic steel corresponds to the steering angle of the steering wheel one-to-one, and the functional relationship thereof has been described above, the mapping relationship between the output voltage of the linear Hall sensor and the steering angle of the steering wheel can be further determined.

[0061] 400. Control the steering motor 4 to rotate until the voltage output by the linear Hall sensor 8 (or 8A and 8B) is equal to the third voltage E3, at which time the steering wheel 4 faces straight ahead, and the steering automatic calibration is completed. In the case where the steering motor itself has a steering detection sensor, the accuracy of the calibration can be further verified by comparing whether the steering direction of the steering wheel obtained by the steering motor at this time faces straight ahead.

[0062] Since the third voltage E3 is calculated according to the first voltage E1 and the second voltage E2 measured in real time through a preset program in the control module, the steering error caused by the linear Hall sensor in different working environments can be avoided, ensuring that the lawn mowing robot can turn correctly. At the same time, since the steering calibration is performed automatically, the work efficiency is improved and the error caused by manual alignment in the prior art is solved.

[0063] Since the positional relationship between the magnet and the linear Hall sensor and the extreme position of the steering wheel are fixed, the parameters of the linear Hall sensor (e.g., k and p) can be corrected through E1, E2 and other known parameters to achieve the correction of the linear Hall sensor error. In some embodiments, the direction control parameters of the steering wheel can be calculated in real time according to the above function. In other embodiments, after the lawn mowing robot is calibrated before departure, a mapping table between the steering angle and the Hall output voltage is established or corrected according to E1, E2 and other known parameters, and the direction control parameters of the steering wheel 4 can be obtained by retrieving the mapping table.

[0064] Preferably, the above-mentioned automatic steering calibration method is performed before the mowing robot departs from the docking station each time. That is, when the mowing robot is parked at the docking station, when the departure conditions are met (the preset departure time is reached or during the working period), before leaving the docking station and entering the working area to work, the steering angle deviation of the steering wheel is calibrated first, and after the calibration is completed, the mowing robot leaves the docking station and enters the working area to work.

[0065] In some embodiments, when the lawn mower robot is in working state and needs to control the steering wheel to rotate to the extreme position, the steering motor is controlled to rotate to the preset direction to the stalled state (i.e., the steering wheel reaches the extreme position on one side), and the output voltage of the linear Hall sensor in the stalled state is recorded. The current detection value is compared with the output voltage of the linear Hall sensor at the extreme position recorded during the last calibration. If the difference between the two exceeds the error threshold, it is determined that a non-negligible error occurs in the linear Hall sensor, and the lawn mower robot is controlled to perform the steering wheel angle deviation calibration (i.e., automatic steering calibration) according to the above method. In some embodiments, the lawn mower robot is controlled to return to the docking station before performing the automatic steering calibration. In some embodiments, the lawn mower robot is controlled to stop walking and perform the automatic steering calibration on the spot on the lawn. However, on-site calibration is easy to damage the lawn, so it is generally not recommended.

[0066] An embodiment of the present invention further provides a lawn mowing robot, which includes a main control board, a processor and a memory, wherein the memory stores a computer program, wherein the processor implements the steps of the above-mentioned automatic steering calibration method when executing the computer program. Preferably, the main control board is arranged at a position close to the magnetic steel, so that the linear Hall sensor installed on the main control board can detect the magnetic steel signal, that is, during the steering process of the steering wheel, the magnetic steel is always within the effective detection range of the linear Hall sensor.

[0067] Exemplarily, the computer program may be divided into one or more modules / units, which are stored in the memory and executed by the processor to complete the method of the present invention. The one or more modules / units may be a series of computer program instruction segments capable of completing specific functions, which are used to describe the execution process of the computer program in the robot.

[0068] The control module of the lawn mowing robot may include but is not limited to a processor and a memory. For example, it may also include input and output devices, network access devices, a bus, etc.

[0069] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor, etc. The processor is the control center of the lawn mower robot, and various interfaces and lines are used to connect various parts of the entire lawn mower robot.

[0070] The memory can be used to store computer programs and / or modules. The processor implements various functions of the mowing robot, such as walking, positioning, mowing, regression charging, and automatic steering calibration, by running or executing the computer programs and / or modules stored in the memory and calling the data stored in the memory. The memory can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, an application required for at least one function, etc.; the data storage area can store working data of the mowing robot, such as a linear Hall sensor and a steering angle mapping table. In addition, the memory can include a high-speed random access memory, and can also include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (SecureDigital, SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0071] The present invention can realize automatic steering calibration by optimizing the arrangement structure of the magnetic steel and the linear Hall sensor, thereby improving work efficiency and calibration accuracy.

[0072] The preferred embodiments of the present invention have been described in detail above, but it should be understood that after reading the above teachings of the present invention, those skilled in the art may make various changes or modifications to the present invention. These equivalent forms also fall within the scope defined by the appended claims of this application.

Claims

1. A method for automatically calibrating the steering of a lawn mower robot, wherein the lawn mower robot comprises a driving wheel and a steering wheel, wherein the steering of the steering wheel is controlled by a steering motor, wherein: The lawn mowing robot further includes at least one linear Hall sensor and a permanent magnet, wherein the permanent magnet is arranged on a component that rotates synchronously with the output shaft of the steering motor, and the positions of the at least one linear Hall sensor and the one permanent magnet are arranged so that the output voltage of the at least one linear Hall sensor has a unique mapping relationship with the steering angle of the steering wheel, and the steering automatic calibration method includes the following steps: Controlling the steering wheel to rotate toward a first limit position until the steering wheel reaches the first limit position, and recording a first voltage output by the at least one linear Hall sensor at this time; Controlling the steering wheel to rotate toward a second limit position until the steering wheel reaches the second limit position, and recording a second voltage output by the at least one linear Hall sensor at this time; Determine or modify the unique mapping relationship according to the first voltage and the second voltage to obtain a third voltage output by the at least one linear Hall sensor corresponding to when the steering wheel is in the front; The steering motor is controlled to rotate until the voltage output by the at least one linear Hall sensor is equal to the third voltage.

2. The automatic steering calibration method of a lawn mowing robot as claimed in claim 1, characterized in that: The at least one linear Hall sensor includes two linear Hall sensors, wherein the two linear Hall sensors are located on both sides of a central plane and directly above the motion trajectory of the permanent magnet, wherein the central plane is parallel to the front of the lawn mowing robot, the output shaft of the steering motor is located on the central plane, and the first limit position and the second limit position are symmetrical about the central plane; wherein the distance between the permanent magnet and the linear Hall sensor on the first side is a=2rsin(α / 2), and the distance between the permanent magnet and the linear Hall sensor on the second side is b=2r cos(α / 2), wherein r is the distance from the permanent magnet to the rotation center of the steering motor, and α is the angle between the permanent magnet-the rotation center-the linear Hall sensor on the first side; wherein the ratio of a and b represents the direction of the steering motor.

3. The automatic steering calibration method of a lawn mowing robot as claimed in claim 2, characterized in that: The two linear Hall sensors are arranged at the first extreme position and the second extreme position respectively.

4. The automatic steering calibration method of a lawn mowing robot as claimed in claim 2 or 3, characterized in that: When the steering wheel faces straight ahead, the permanent magnet is located on the central plane.

5. The automatic steering calibration method of a lawn mowing robot as claimed in claim 1, characterized in that: The at least one linear Hall sensor includes a linear Hall sensor, which is located directly above the motion trajectory of the permanent magnet, wherein the distance between the permanent magnet and the linear Hall sensor is d=2r sin(α / 2), wherein r is the distance from the permanent magnet to the rotation center of the steering motor, and α is the angle between the permanent magnet-the rotation center-the linear Hall sensor; wherein the d value or the corresponding output voltage of the linear Hall sensor represents the direction of the steering motor.

6. The automatic steering calibration method of a lawn mowing robot as claimed in claim 5, characterized in that: The permanent magnet is located at the first extreme position or the second extreme position.

7. The automatic steering calibration method of a lawn mowing robot as claimed in claim 1, characterized in that: The at least one linear Hall sensor is arranged on the main control board of the lawn mowing robot.

8. The automatic steering calibration method of a lawn mowing robot as claimed in claim 1, characterized in that: The permanent magnet is a circular magnetic steel.

9. The automatic steering calibration method of a lawn mowing robot as claimed in claim 1, characterized in that: The unique mapping relationship is determined by establishing a mapping function or a mapping table.

10. The automatic steering calibration method of a lawn mowing robot as claimed in claim 1, characterized in that: The steering automatic calibration method also includes: Before the mowing robot departs from a parking station each time, the steering wheels are automatically calibrated.

11. The automatic steering calibration method of a lawn mowing robot as claimed in claim 1, characterized in that: The steering automatic calibration method also includes: When the lawn mowing robot is in a working state, when it is detected that the difference between the first voltage or the second voltage and the first voltage or the second voltage recorded during the last steering automatic calibration is greater than an error threshold, the steering automatic calibration is performed.

12. The automatic steering calibration method of a lawn mowing robot as claimed in claim 11, characterized in that: The lawn mowing robot is controlled to return to the docking station and then automatically calibrate the steering.

13. The automatic steering calibration method of a lawn mowing robot as claimed in claim 11, characterized in that: The correction of the unique mapping relationship includes correcting parameters of the linear Hall sensor.

14. A lawn mowing robot, comprising a main control board, wherein the main control board stores a computer program, wherein: When the main control board executes the computer program, the steps of the steering automatic calibration method according to any one of claims 1 to 13 are implemented.

Images