Method for controlling autonomous mobile robot

Abstract

The present disclosure relates to a path-following control method for an autonomous mobile robot (AMR) in which the front wheels and rear wheels are each equipped with roller sections of an omnidirectional drive type. According to one embodiment of the present disclosure, a method for controlling path-following of an autonomous mobile robot comprises: a step of obtaining information regarding a starting point and an ending point of a path; a step of setting the coordinates of a plurality of intermediate points between the starting point and the ending point of the path; a step of obtaining the coordinates of a first point, which is the closest intermediate point among the plurality of intermediate points; a step of calculating a heading error, which is the difference value between the normal angle of the first point and the attitude angle of the autonomous mobile robot; a step of calculating a cross-track error, which is the distance value between the coordinates of the first point and the coordinates of the autonomous mobile robot; a step of calculating a steering angle based on the front wheel based on the heading error, the cross-track error, and the driving speed; a step of calculating a turning radius based on the steering angle; and a step of calculating the steering angle of the front wheel and the steering angle of the rear wheel based on the turning radius. and includes a step of controlling the front wheels and rear wheels respectively based on the steering angle of the front wheels and the steering angle of the rear wheels.

Description

Technology Field

[0001] The present disclosure relates to a path-following control method for an autonomous mobile robot (AMR), and more specifically, to a path-following control method for an autonomous mobile robot in which the front wheels and rear wheels are each equipped with roller parts of an omnidirectional drive type. Background Technology

[0002] With the recent acceleration of automation in industrial sites and logistics warehouses, the introduction of Autonomous Mobile Robots (AMRs), which drive autonomously along predetermined paths to transport goods, is rapidly increasing. Conventional mobile robots have primarily adopted differential drive systems using two drive wheels or steer drive systems using front-wheel steering. However, these methods have technical limitations, such as limited maneuverability in confined spaces due to a large turning radius, and reduced driving stability because load distribution is not efficiently achieved when carrying heavy loads.

[0003] To overcome this, a Quad Drive structure in the form of an omni-directional drive in which each of the four wheels is independently steered and driven can be introduced. The Quad Drive system enables forward, backward, left, right, and meandering movement without changing the direction of the main body, providing high maneuverability and offering advantages for transporting heavy loads and precision driving.

[0004] However, since quad-drive systems have high degrees of freedom and complex drive mechanisms, precise control algorithms are required for the robot to accurately follow a planned path. While existing PID-based, Pure-Pursuit-based, or Predictive Control-based path tracking techniques demonstrate useful performance in specific environments, they have limitations in simultaneously satisfying requirements such as high-precision steering in spaces with significant structural constraints—including narrow corridors, sharp turns, precise stopping positions, and heavy loads in semiconductor factories—as well as ensuring control stability under dynamic load changes, real-time performance, computational efficiency, and ease of maintenance in industrial operating environments. The problem to be solved

[0005] The purpose of the present disclosure is to provide a control method capable of improving path following precision of an autonomous driving robot having a quad drive structure of an omnidirectional driving type.

[0006] In addition, the present disclosure aims to provide a control method capable of rapidly and stably converging to a target path without overshoot or oscillation phenomena, even in complex path environments. means of solving the problem

[0007] According to one embodiment of the present disclosure, a method for controlling path following of an autonomous mobile robot (AMR), wherein the front wheel and the rear wheel are each equipped with a roller part of an omnidirectional drive type, comprises: a step of obtaining information regarding the path of the autonomous mobile robot and the starting point and ending point of the path; a step of setting the coordinates of a plurality of intermediate points between the starting point and the ending point of the path; a step of obtaining the coordinates of a first point, which is the intermediate point closest to the autonomous mobile robot among the plurality of intermediate points; a step of calculating a heading error, which is the difference between the normal angle of the first point and the attitude angle of the autonomous mobile robot; a step of calculating a cross-track error, which is the distance between the coordinates of the first point and the coordinates of the autonomous mobile robot; a step of calculating a steering angle based on the front wheel based on the heading error, the cross-track error, and the driving speed; a step of calculating a turning radius based on the steering angle; a step of calculating the steering angle of the front wheel and the steering angle of the rear wheel based on the turning radius; and a step of controlling the front wheel and the rear wheel, respectively, based on the steering angle of the front wheel and the steering angle of the rear wheel.

[0008] According to one embodiment of the present disclosure, in the step of calculating the adjustment angle based on the front wheel, the adjustment angle based on the front wheel can be calculated according to the following mathematical formula.

[0009] <Mathematical Formula>

[0010]

[0011] Here, is the adjustment angle based on the front wheels, is heading error, is the cross-track error tracking control gain, is cross-track error, is driving speed.

[0012] According to one embodiment of the present disclosure, in the step of calculating the turning radius based on the adjustment angle, the directional angle of the center of gravity corresponding to the adjustment angle is calculated, and the turning radius can be calculated based on the calculated directional angle of the center of gravity and the wheelbase distance.

[0013] According to one embodiment of the present disclosure, in the step of calculating the steering angle of the front wheel and the steering angle of the rear wheel, the arctangent function value of the wheelbase distance relative to the turning radius is determined as the steering angle of the front wheel, and the negative value of the steering angle of the front wheel is determined as the steering angle of the rear wheel.

[0014] According to one embodiment of the present disclosure, in the step of setting the coordinates of an intermediate point, an extension point can be additionally set that is extended by a certain extension distance in the path direction from the end point.

[0015] In addition, other configurations may be added to control the path following of the autonomous driving robot. Effects of the invention

[0016] According to one embodiment of the present disclosure, by controlling the path following of an autonomous driving robot based on heading error and cross-track error, it is possible to follow a target path without overshoot even in a complex path environment.

[0017] In addition, according to one embodiment of the present disclosure, by securing a minimized turning radius through quad drive and simultaneous steering technology, maneuverability in confined spaces can be maximized, and the transport efficiency and return reliability of heavy goods can be substantially improved through effective load distribution. Brief explanation of the drawing

[0018] FIG. 1 is a diagram exemplarily showing an autonomous driving robot following a path according to one embodiment of the present disclosure. FIG. 2 is a drawing exemplarily showing the lower structure of an autonomous driving robot according to one embodiment of the present disclosure. FIG. 3 is a drawing showing in detail a roller part of an omnidirectional driving type corresponding to the front and rear wheels of an autonomous driving robot according to one embodiment of the present disclosure. FIG. 4 is an operation flowchart illustrating a path-following control method for an autonomous driving robot according to one embodiment of the present disclosure. FIG. 5 is a diagram illustrating a method for setting intermediate points according to the shape of a driving path according to one embodiment of the present disclosure. FIG. 6 is a diagram illustrating the process of searching for the nearest intermediate point from the current position (pRo) of an autonomous driving robot according to one embodiment of the present disclosure. FIG. 7 is a drawing for explaining the process of calculating heading error and cross-track error according to one embodiment of the present disclosure. FIG. 8 is a diagram showing a geometric structure for calculating the turning radius and the directional angle of the center of gravity of an autonomous driving robot according to one embodiment of the present disclosure. FIG. 9 is a diagram showing comparison data for verifying the performance of a path-following control algorithm of an autonomous driving robot according to one embodiment of the present disclosure. Specific details for implementing the invention

[0019] The embodiments described below are illustrative for the purpose of explaining the technical concept of the present disclosure, and the scope of the rights of the present disclosure is not limited to the embodiments presented below or the specific descriptions thereof.

[0020] All technical and scientific terms used in this specification have the meaning generally understood by those skilled in the art to which this disclosure pertains, unless otherwise defined, and all terms used in this specification are selected for the purpose of further clarifying this disclosure and are not selected to limit the scope of the rights of this disclosure.

[0021] Expressions used in this specification, such as “comprising,” “comprising,” “having,” etc., should be understood as open-ended terms implying the possibility of including other embodiments unless otherwise stated in the phrase or sentence containing such expressions.

[0022] Hereinafter, preferred embodiments of the present disclosure are described in detail with reference to the attached drawings so that those skilled in the art can easily implement them.

[0023] FIG. 1 is a diagram exemplarily showing an autonomous driving robot following a path according to one embodiment of the present disclosure.

[0024] Referring to FIG. 1, an autonomous mobile robot (100, Autonomous mobile robot, AMR) according to one embodiment of the present disclosure may be configured to autonomously drive along a set path in an industrial site or a logistics warehouse, and to transport goods or perform a specific process. The autonomous mobile robot (100) may include a main body forming the shape of the robot and a driving unit provided at the bottom of the main body to move the robot.

[0025] FIG. 2 is a drawing illustrating an exemplary lower structure of an autonomous driving robot according to one embodiment of the present disclosure. Referring to FIG. 2, the driving unit of the autonomous driving robot (100) may have a Quad Drive structure in which the front wheel (121) and the rear wheel (122) are each equipped with roller parts in an omni-directional driving form, and one or more auxiliary wheels (130) on both sides are configured to maintain the horizontal level of the vehicle body. This Quad Drive structure provides high maneuverability by enabling free movement in four directions, such as straight, reverse, left, and right, and has the advantage of having a small turning radius and being advantageous for transporting heavy loads and precision driving.

[0026] FIG. 3 is a detailed drawing showing a roller section (120) of an omnidirectional driving type corresponding to the front and rear wheels of an autonomous driving robot according to one embodiment of the present disclosure. Referring to FIG. 3, the roller section (120) is provided on the front wheel (121) and rear wheel (122) of the autonomous driving robot (100), respectively, and performs independent steering and driving functions. Specifically, the roller section (120) may be configured to include a steering section (310), a driving wheel (320), and a driving motor (330). The steering section (310) controls the steering angle of the driving wheel (320) in an omnidirectional manner of 360 degrees, and the driving motor (330) provides rotational power to the driving wheel (320) to move the robot.

[0027] In this way, through a drive unit with a structure in which steering and driving are controlled individually, the autonomous driving robot (100) can provide mobility that allows it to move freely in forward, backward, left, right, and diagonal directions without changing the direction of the main body. In addition, the quad drive method effectively distributes the load to enable the transport of heavy loads, and supports precise path-following driving with a minimized turning radius even in narrow spaces.

[0028] Referring again to FIG. 1, the autonomous driving robot (100) may be equipped with a robotic arm (110, Robotic Arm) on its upper part, which can perform tasks such as grasping or assembling items according to the purpose of the work. In addition, the autonomous driving robot (100) may be equipped with warning lights and various sensors to indicate the operating status of the robot to the surroundings.

[0029] The autonomous driving robot (100) can be controlled to identify a target path in real time and follow it. Specifically, the autonomous driving robot (100) can perform precise path-following driving by determining intermediate points on the path in real time, calculating and correcting a heading error based on the attitude angle of the autonomous driving robot and the normal angle at the intermediate point, and a cross-track error based on the distance between the intermediate point and the autonomous driving robot. Below, a path-following control method for such an autonomous driving robot (100) will be described in detail.

[0030] FIG. 4 is an operation flowchart illustrating a path-following control method for an autonomous driving robot according to one embodiment of the present disclosure.

[0031] Referring to FIG. 4, the autonomous driving robot (100) first obtains information regarding the path to be driven and the starting point and ending point of the path (S401). At this time, the starting point (pS) refers to the coordinates where the driving operation is initiated, and the ending point (pE) refers to the coordinates of the target point that the robot must ultimately reach. This path information can be obtained through map data that is received in real time from an upper control system or stored in advance in the robot's internal memory. The coordinate information of the starting and ending points obtained at this stage can be used as basic data to subdivide the entire driving path and generate multiple intermediate points.

[0032] Afterward, the autonomous driving robot (100) sets the coordinates of a plurality of intermediate points between the starting point (pS) and the ending point (pE) of the path (S403). At this time, the path may be planned in a straight line or a curved shape depending on the driving environment and the destination, and the coordinates of each intermediate point may be calculated in a different way depending on the shape of the path.

[0033] FIG. 5 is a diagram illustrating a method for setting intermediate points according to the shape of a driving path according to one embodiment of the present disclosure. FIG. 5 (a) illustrates a straight path, and FIG. 5 (b) illustrates a curved path (R-Turn).

[0034] Referring to FIG. 5 (a), when the driving path is in the form of a straight line, the autonomous driving robot (100) can set the coordinates of the intermediate point according to the coordinate relationship between the starting point (pS) and the ending point (pE). Specifically, in the case of a vertical path where the X-axis coordinates of the starting point and the ending point are the same (i.e., pS.x = pE.x) based on an arbitrary straight-line coordinate system and a linear function does not hold, the coordinates of the intermediate point for each index can be set according to the following mathematical formula 1.

[0035] <Mathematical Formula 1>

[0036]

[0037]

[0039] Here, deltaIndex represents the difference in index based on the total number of intermediate points.

[0040] In addition, for a straight path with a slope where the X-axis coordinates of the starting point and the ending point are different (i.e., pS.x ≠ pE.x) based on an arbitrary straight-line coordinate system, the coordinates of the intermediate point can be set according to the following mathematical formula 2.

[0041] <Mathematical Formula 2>

[0042]

[0043]

[0045] Referring to FIG. 5(b), when the driving path is in the form of a curve, the autonomous driving robot (100) can manage the path by subdividing it into straight sections (pS~pM1), arc sections (pM1~pM2), and straight sections (pM2~pE). At this time, the total path length (dist) is calculated as the sum of the distances for each section, distStoM1, distR (arc distance), and distM2toE, and the total index can be distributed according to the ratio of the distances of each section. The intermediate point coordinates in the arc sections (pM1~pM2) can be calculated according to the following mathematical formula 3 using the center point (pC), the radius of rotation (radius), and the radian value of the corresponding index.

[0046] <Mathematical Formula 3>

[0047]

[0048]

[0050] The multiple intermediate points calculated in this way can form precise reference trajectory data that the autonomous driving robot (100) must follow during actual driving.

[0051] According to one embodiment of the present disclosure, in order to maintain steering stability and prevent sudden changes in control when the autonomous driving robot (100) approaches a target point (pE), an extension point can be additionally set that is extended by a certain extension distance in the direction of path progression from the end point (pE). Accordingly, the entire reference trajectory data may be configured to include not only intermediate points from the start point to the end point, but also a plurality of extended intermediate points set in the interval between the end point (pE) and the extension point (pExt). Through this path extension technique, the robot can secure sufficient forward path data until the moment it reaches the target point, so that it can stably stop at the target point or transition to the next path without control delay or vibration due to driving speed.

[0052] When multiple intermediate points for a reference path are set in step (S403), the autonomous driving robot (100) can search for the intermediate point closest to its current location in real time and obtain the corresponding coordinates (S405).

[0053] FIG. 6 is a diagram illustrating the process of searching for the nearest intermediate point from the current position (pRo) of an autonomous driving robot according to one embodiment of the present disclosure. Referring to FIG. 6, the autonomous driving robot (100) calculates the distance between its current coordinates (pRo) obtained through a sensor (e.g., LiDAR, encoder, etc.) and a plurality of intermediate points (e.g., pI[0] to pI

[0599] ) set in step (S403). At this time, the distance (distance[i]) between the intermediate point corresponding to each index (i) and the robot's current position can be calculated through the following mathematical formula 4.

[0054] <Mathematical Formula 4>

[0055]

[0057] The autonomous driving robot (100) searches for an index (iMin) that has the minimum value (distMin) among the distance values ​​calculated through loop operations. As a result of the search, the coordinates (pI[iMin]) of the first point corresponding to the minimum distance are finally obtained, which becomes the closest reference point on the path that the robot must currently follow.

[0058] After obtaining the coordinates of the first point closest to the point in step (S405), the autonomous driving robot (100) calculates a heading error by comparing the path direction at the point with the direction of travel of the autonomous driving robot (S407). In addition, a cross-track error is calculated by comparing the coordinates of the point with the coordinates of the autonomous driving robot (S409).

[0059] FIG. 7 is a drawing for explaining the process of calculating heading error and cross-track error according to one embodiment of the present disclosure.

[0060] Referring to FIG. 7, the autonomous driving robot (100) can analyze how far the robot's posture and position deviate from the target path based on the first point, which is the nearest intermediate point.

[0061] First, the autonomous driving robot (100) has a normal angle of the first point ( ) and the current attitude angle of the autonomous driving robot( Heading error, which is the difference between ) ) is calculated (S407). The heading error is an indicator representing how closely the robot's direction of movement aligns with the tangent direction of the target path in terms of angle, and can be calculated using the relative coordinate change between the first point (pI[iMin]) and the next point (pI[iMinNext]) at that index. Specifically, the heading error ( ) can be calculated according to the following mathematical formula 5.

[0062] <Mathematical Formula 5>

[0063]

[0064]

[0065]

[0066]

[0067] (However, the sign may be determined based on the steering direction)

[0069] Next, the autonomous driving robot (100) has a cross-track error (the distance between the coordinates of the first point and the current coordinates (pRo) of the autonomous driving robot. ) is calculated (S409). For example, if the path is a straight line direction with a slope, the cross-track error can be calculated by deriving the straight line equation ax+by+c=0 passing through adjacent intermediate points and finding the distance from the robot's current position (pRo). This can be expressed as Equation 6 below.

[0070] <Mathematical Formula 6>

[0071]

[0073] Heading error ( ) and cross-track error( When ) is calculated, the autonomous driving robot (100) calculates the front wheel-based adjustment angle based on this (S411). In one embodiment, the front wheel-based adjustment angle can be calculated by applying a Stanley Controller algorithm. Specifically, the front wheel-based adjustment angle can be calculated according to the following mathematical formula 7.

[0074]

[0075]

[0076] Here, is the adjustment angle based on the front wheels, and is the heading error, is a cross-track error tracking control gain (set to a value between 0.1 and 2.0), and is the cross-track error, refers to the driving speed of the autonomous driving robot. Among these, the driving speed of the autonomous driving robot ( (t)) can be calculated by referring to the rotational speed of the drive motor (330) of the roller part (120).

[0077] Here, is the adjustment angle based on the front wheels, and is the heading error, is a cross-track error tracking control gain (set to a value between 0.1 and 2.0), and is the cross-track error, refers to the driving speed of the autonomous driving robot. Among these, the driving speed of the autonomous driving robot ( (t)) can be calculated by referring to the rotational speed of the drive motor (330) of the roller part (120).

[0078] According to this, the autonomous driving robot (100) can secure variable path return performance according to speed by first correcting the angle difference from the path (heading error) and reflecting the distance of deviation from the path (cross track error) in conjunction with the driving speed. At this time, the range of the correction value is limited to within a certain angle (e.g., within 90 degrees) by the arctangent function, thereby preventing the steering part from turning excessively even when the error is large and enabling stable steering control.

[0079] When the adjustment angle based on the front wheel is determined, the autonomous driving robot (100) calculates the turning radius corresponding to the actual driving trajectory of the robot's center of gravity based on this (S413).

[0080] Referring to FIG. 8, the autonomous driving robot (100) has a direction angle (A) of the front wheel (A). ), direction angle of the rear wheel (B) ), and the wheelbase distance, which is a geometric specification of the autonomous driving robot ( , The radius of rotation (R) can be calculated using the correlation between ). First, the direction angle ( of the center of gravity (C) of the autonomous driving robot (100) ) is calculated according to the following mathematical formula 8.

[0081] Referring to FIG. 8, the autonomous driving robot (100) has a steering angle (A) of the front wheel (A). ), steering angle of the rear wheel (B) ), and the wheelbase distance, which is a geometric specification of the autonomous driving robot ( , The turning radius (R) can be calculated using the correlation between ). First, the autonomous driving robot (100) has a direction angle of the center of gravity (C) corresponding to the adjustment angle based on the front wheel ( ) is calculated according to the following mathematical formula 8.

[0082] <Mathematical Formula 8>

[0083]

[0084] In one embodiment, the distance from the axles of the front and rear wheels to the center of gravity and is identically ( = ) can be set. When calculating the initial turning radius, the direction angle of the rear wheel ( Assuming ) is 0, the direction angle of the center of gravity( ) is the direction angle of the front wheel( It can be determined by ) and robot specifications (i.e., the distance from the axles of the front and rear wheels to the center of gravity). Here, the steering angle of the front wheel ( ) is the front-wheel-based adjustment angle calculated through mathematical formula 7 ( It can be the same as ). Subsequently, the autonomous driving robot (100) has a calculated center of gravity direction angle ( The final radius of rotation (R) is calculated using ) according to the following mathematical formula 9.

[0085] In one embodiment, the distance from the axles of the front and rear wheels to the center of gravity and is identically ( = ) can be set. When calculating the initial turning radius, the steering angle of the rear wheels ( Assuming ) is 0, the direction angle of the center of gravity( ) is the steering angle of the front wheels ( It can be determined by ) and robot specifications. Subsequently, the autonomous driving robot (100) has a calculated center of gravity direction angle ( The final radius of rotation (R) is calculated using ) according to the following mathematical formula 9.

[0086] <Mathematical Formula 9>

[0087]

[0089] When the turning radius (R) is calculated, the autonomous driving robot (100) uses this as a basis to control the steering angle of the front wheel ( ) and rear wheel steering angle( ) is finally calculated (S415). In order for the autonomous driving robot (100) to drive along the target path while maintaining the calculated turning radius (R), the steering angle of the front wheel ( The negative value of ) is the rear wheel steering angle ( It can be made to follow an arc trajectory by determining ) ). At this time, the direction angle of the center of gravity in Fig. 8 ( ) becomes 0, and according to the sine law, the steering angle of the front wheel ( ) is the wheelbase distance relative to the turning radius (R) It can be determined by the arctangent function value of ). This can be expressed as Equation 10 below.

[0090] When the turning radius (R) is calculated, the autonomous driving robot (100) uses this as a basis to control the steering angle of the front wheel ( ) and rear wheel steering angle( ) is finally calculated (S415). In order for the autonomous driving robot (100) to drive along the target path while maintaining the calculated turning radius (R), the steering angle of the front wheel ( The negative value of ) is the rear wheel steering angle ( It can be made to follow an arc trajectory by determining ) ). At this time, the direction angle of the center of gravity in Fig. 8 ( ) becomes 0, and according to the sine law, the steering angle of the front wheel ( ) is the wheelbase distance relative to the turning radius (R) It can be determined by the arctangent function value of ). This can be expressed as Equation 10 below.

[0091]

[0092]

[0094] The control unit of the autonomous driving robot (100) calculates the steering angle of the front wheel ( ) and rear wheel steering angle( ) information is transmitted to the steering unit (310) positioned in each roller unit (120). The steering unit of each roller unit (120) precisely rotates the angle of the drive wheel (320) to a set steering angle through a servo motor or the like. At the same time, the autonomous driving robot (100) reaches a target driving speed ( The drive motor (330) of each roller part (120) is controlled based on ). At this time, the four wheels can be driven at different speeds and angles according to independent control algorithms, thereby enabling omnidirectional movement and precise driving characteristic of the quad drive structure.

[0095] The control unit of the autonomous driving robot (100) calculates the steering angle of the front wheel ( ) and rear wheel steering angle( ) information is transmitted to the steering unit (310) positioned in each roller unit (120). The steering unit of each roller unit (120) precisely rotates the angle of the drive wheel (320) to a set steering angle through a servo motor or the like. At the same time, the autonomous driving robot (100) reaches a target driving speed ( The drive motor (330) of each roller part (120) is controlled based on ). At this time, the four wheels can be driven at different speeds and angles according to independent control algorithms, thereby enabling omnidirectional movement and precise driving characteristic of the quad drive structure.

[0096] Through this control process, the autonomous driving robot (100) can ensure that its actual driving trajectory follows a pre-planned reference path with minimal error. During driving, the autonomous driving robot (100) can return to step (S405) according to the set driving cycle, recalculate the error at the current position, and repeatedly perform a feedback loop to update the control amount, thereby stably reaching the target point.

[0097] FIG. 9 is a diagram showing comparison data for verifying the performance of a path-following control algorithm of an autonomous driving robot according to one embodiment of the present disclosure. FIG. 9 (a) illustrates a driving result to which the control method of the present invention is applied, and FIG. 9 (b) illustrates a driving result of a comparison group (e.g., parameter non-optimization or conventional control method).

[0098] Referring to FIG. 9 (a), it can be seen that the actual driving trajectory of the autonomous driving robot (100) converges smoothly along the reference path without overshoot or vibration and reaches the target point accurately. On the other hand, in the comparison group of FIG. 9 (b), it is confirmed that the driving efficiency is reduced as oscillation occurs, causing the autonomous driving robot to shake left and right around the reference path.

[0099] Although the present disclosure has been described above with specific details such as specific components, limited embodiments, and drawings, this is provided only to aid in a more comprehensive understanding of the present disclosure and is not limited to the above embodiments, and a person skilled in the art to which the present disclosure belongs may make various modifications and variations from this description.

[0100] Accordingly, the concept of the present disclosure should not be limited to the embodiments described above, and should be interpreted as falling within the scope of the concept of the present disclosure, including the claims set forth below as well as all equivalent or equivalent variations thereof. Explanation of the symbols

[0101] 100: Autonomous driving robot 110: Robot arm 120: Roller section 121: Front wheel 122: Rear-wheel drive 130: Training wheels 310: Steering unit 320: Drive wheel 330: Drive motor

Claims

Claim 1 A path-following control method for an autonomous mobile robot (AMR) in which the front wheels and rear wheels are each equipped with roller sections of an omnidirectional drive type, comprising: a step of obtaining information regarding the path of the autonomous mobile robot and the start and end points of said path; if said path is in the form of a curve, a step of subdividing said path into a first straight section (pS~pM1), an arc section (pM1~pM2), and a second straight section (pM2~pE), calculating the total path length as the sum of the distances for each section, and then distributing the total index according to the ratio of the distances of each section to set the coordinates of a plurality of intermediate points between said path and said end points, and additionally setting an extension point extended by a certain extension distance in the path direction from said end points; a step of obtaining the coordinates of a first point, which is the intermediate point closest to the autonomous mobile robot among said plurality of intermediate points and said extension point; a step of calculating a heading error, which is the difference between the normal angle of said first point and the attitude angle of said autonomous mobile robot; and between the coordinates of said first point and the coordinates of said autonomous mobile robot A path-following control method for an autonomous driving robot, characterized by comprising: a step of calculating a cross-track error, which is a distance; a step of calculating a steering angle based on the front wheel based on the heading error, the cross-track error, and the driving speed; a step of calculating the direction angle of the center of gravity according to the following mathematical formula 1, and a step of calculating the turning radius according to the following mathematical formula 2 based on the calculated direction angle of the center of gravity and the distance from the axle of the front wheel to the center of gravity; a step of calculating the steering angle of the front wheel and the steering angle of the rear wheel according to the following mathematical formula 3 based on the turning radius; and a step of controlling the front wheel and the rear wheel, respectively, based on the steering angle of the front wheel and the steering angle of the rear wheel. <Mathematical Formula 2> <Mathematical Formula 3> In mathematical formulas 1 to 3 is the angle of the center of gravity, is the distance from the front axle to the center of gravity, is the rear wheel direction angle, is the distance from the rear axle to the center of gravity, is the direction angle of the front wheel, The radius of rotation, is the steering angle of the front wheels. Claim 2 A path-following control method for an autonomous driving robot according to claim 1, characterized in that the autonomous driving robot is used in an industrial environment requiring mobility in confined spaces and conditions for transporting heavy loads, such as a semiconductor process or logistics automation environment. Claim 3 A path-following control method for an autonomous driving robot according to claim 1, wherein in the step of calculating the adjustment angle based on the front wheel, the adjustment angle based on the front wheel is calculated according to the following mathematical formula, and the direction angle of the front wheel is determined by the calculated adjustment angle based on the front wheel. <Mathematical Formula> Here, is the adjustment angle based on the front wheels, is heading error, is the cross-track error tracking control gain, is cross-track error, is driving speed. Claim 4 A path-following control method for an autonomous driving robot according to claim 1, wherein in the step of calculating the steering angle of the front wheel and the steering angle of the rear wheel, the negative value of the steering angle of the front wheel is determined as the steering angle of the rear wheel. Claim 5 A path-following control method for an autonomous driving robot according to claim 1, characterized in that the extension point is set to maintain steering stability and suppress sudden changes in control when approaching the end point.

Images