Magnetic nail positioning arrangement method suitable for double magnetic sensing and agv tracking control method

Abstract

The application relates to a magnetic nail positioning arrangement method suitable for double magnetic sensing, and belongs to the fields of component positioning arrangement methods in magnetic sensing technology and tracking control technologies for automatic driving. The chassis system of a vehicle adopting the magnetic nail positioning arrangement method is a chassis system with front and rear wheels, wherein the front and rear wheels are provided with front and rear axles and can be independently controlled to turn. Magnetic sensors are arranged at the centers of the front and rear axles. The magnetic nail positioning arrangement method comprises a magnetic nail arrangement process. According to the front and rear magnetic sensors, a magnetic nail route is divided into a straight line and an arc, and the straight line route and the arc route are combined into an AGV movement route. In an AGV tracking control method, the two magnetic sensors on the AGV vehicle sense the magnetic nails on the path. The tracking control method comprises tracking control of a straight line path, which is recorded as a straight line mode, and tracking control of a turning path, which is recorded as a turning mode. The tracking control of the straight line mode and the turning mode comprises tracking control of the front and rear wheels.

Description

Technical Field

[0001] The present invention relates to the field of component positioning and arrangement methods in magnetic sensing technology and the field of tracking control technology for autonomous driving. Background Art

[0002] Magnetic nail navigation is a navigation system based on magnetic nail technology that provides precise positioning and navigation capabilities. Magnetic nails, small magnetic objects placed on the ground, generate unique magnetic field signals. Using these signals, the magnetic nail navigation system can locate and navigate the vehicle. This requires the development of corresponding positioning and navigation algorithms to calculate the optimal navigation path based on the vehicle's current and target positions, and provide real-time navigation guidance to help the vehicle accurately reach its destination. Magnetic nail navigation technology utilizes magnetic field sensors, positioning algorithms, map construction and calibration, and navigation algorithms to achieve precise positioning and navigation in indoor environments. This technology has broad application prospects in indoor navigation, unmanned vehicles, intelligent robots, and other fields. Magnetic nail navigation uses different positioning and navigation methods depending on the magnetic nails used and the arrangement of the magnetic field sensors. Magnetic nails with ID information can provide higher positioning accuracy, while ordinary magnetic nails can only provide relatively simple positioning functions. Ordinary magnetic nails still have a wide range of application scenarios due to their lower prices, but there are more stringent requirements for the layout of the magnetic nails. The use of dual magnetic field sensors can provide heading information, but for vehicles that cannot turn on the spot, the layout of the magnetic nail route will be more complicated.

[0003] Existing magnetic nail positioning solutions are mainly aimed at chassis systems that can rotate in place. However, in autonomous driving logistics transportation vehicles, automatic inspection operation robots, etc., there are many intelligent transport vehicles and robots whose chassis systems cannot rotate in place. Therefore, the application of existing magnetic nail positioning solutions has great limitations.

[0004] Tracking control technology for autonomous driving refers to the technology used to track and control vehicles within autonomous driving systems. It is a crucial component of autonomous driving systems, ensuring that the vehicle accurately follows its chosen path and performing control based on real-time environmental and sensor data for safe, stable, and efficient driving. Tracking control technology uses control algorithms to calculate vehicle control commands to achieve the desired trajectory. Common control algorithms include PID control and model predictive control (MPC). Model predictive control uses vehicle dynamics and environmental models to predict vehicle behavior over a period of time and then implements control based on the predicted results to achieve more accurate tracking. Tracking control technology requires real-time control and adjustments based on vehicle status and environmental changes. By collecting and processing sensor data in real time, the tracking control system continuously updates vehicle status and environmental information and adjusts control commands based on this feedback to achieve precise tracking. In general, using the appropriate tracking control algorithm for the specific scenario and vehicle can maximize the algorithm's performance and achieve optimal control results.

[0005] Existing tracking control technologies primarily target differential chassis models. Few control methods exist for chassis models with independent front and rear wheel steering and no rotational capability. Furthermore, existing PID tracking control methods exhibit large tracking errors in cornering scenarios. This invention addresses these limitations by proposing a method for tracking control along a path composed of straight lines and circular arcs for a chassis model with independent front and rear wheel steering and no rotational capability. Summary of the Invention

[0006] The object of the present invention is to provide a magnetic nail positioning arrangement method suitable for dual magnetic sensing, which can be adapted to a chassis system with four-wheel independent steering and cannot rotate in situ.

[0007] Another object of the present invention is to provide an AGV tracking control method that combines the above-mentioned magnetic nail positioning arrangement method suitable for dual magnetic sensing to perform sensor positioning tracking control. In response to the limitations of the background technology, it proposes a chassis model in which the front and rear wheels can independently steer and cannot rotate in place, and a method for implementing tracking control on a path composed of straight lines and circular arcs.

[0008] To achieve the above objectives, the technical solution of the present invention is: a magnetic nail positioning arrangement method suitable for dual magnetic sensing, a vehicle using the magnetic nail positioning arrangement method of the present invention, wherein the chassis system is a chassis system in which the front wheels and rear wheels respectively have front axles and rear axles capable of independent steering control, and magnetic sensors are respectively provided at the center of the front axle and the center of the rear axle on the vehicle. The magnetic nail positioning arrangement method includes a magnetic nail arrangement process, and the specific magnetic nail arrangement process is as follows:

[0009] 1) With the center point of the front and rear axles of the vehicle as the reference point, the magnetic nail layout route is determined according to the movement trajectory of the reference point. The magnetic nail layout route is composed only of straight lines and various arcs of fixed radius. The intersection of the arc and the straight line in the magnetic nail layout route forms an arc intersection segment and a straight line intersection segment. The two ends of the arc intersection segment and the straight line intersection segment are the intersection points of the straight line and the arc.

[0010] 2) Determine the wheelbase between the front axle and the rear axle, use the wheelbase as the magnetic pin induction spacing distance d, divide the magnetic pin induction spacing distance d by an integer, and determine the magnetic pin arrangement spacing distance s;

[0011] 3) Take a point on the non-straight intersection of a straight line or a point on the non-circular intersection of an arc as the first placement starting point, and start from the first placement starting point to place magnetic nails in sequence at equal intervals on the straight line or arc according to the arrangement interval s;

[0012] 4) Ensure that magnetic pins are placed at both intersections of the straight line (or arc) and the arc (or straight line);

[0013] 5) Continue to place magnetic nails on the arcs connected by straight lines or continue to place magnetic nails on the straight lines connected by arcs. The interval point of the connected arc or straight line from the first intersection point of the previous straight line or arc is the set intersection interval distance ss as the second placement starting point. Starting from the second placement starting point, magnetic nails are arranged in sequence on the connected straight line or arc according to the arrangement interval distance s. The intersection interval distance ss should be greater than or less than the arrangement interval distance s to ensure that the magnetic nails on the arc intersection segment and the straight line intersection segment are staggered.

[0014] The AGV tracking control method on the path of the magnetic nails is arranged by the magnetic nail positioning arrangement method suitable for dual magnetic sensing. The two magnetic sensors on the AGV vehicle respectively sense the magnetic nails on the path. The tracking control method includes tracking control of a straight path, which is recorded as a straight mode, and tracking control of a turning path, which is recorded as a turning mode. The tracking control execution of the straight mode and the turning mode includes tracking control of the front wheels and the rear wheels. Since the front wheels and the rear wheels can be independently steered, the tracking control method is described by taking the tracking control execution of the front wheels as an example. The execution method steps of the rear wheels can be obtained by referring to the front wheels. The steps of the front wheel tracking control method in the straight mode and the turning mode are as follows:

[0015] Straight line mode:

[0016] 1) Obtain magnetic navigation positioning;

[0017] 2) The given linear speed is a fixed value;

[0018] 3) Calculate the lateral offset error, cumulative lateral offset error, and heading error from the center of the front axle of the front wheel to the straight path;

[0019] 4) Determine the PID coefficient and calculate the dynamic front wheel deflection angle value corresponding to the PID;

[0020] 5) Determine the final front wheel deflection angle value;

[0021] 6) The calculated final front wheel deflection angle w is output to the controller as the actual control value, controlling the front wheel to deflect according to the set value;

[0022] 7) Return to step 2) and perform calculations in a loop to achieve PID tracking control of the vehicle's front wheels;

[0023] Turning Mode:

[0024] S1) Obtain magnetic navigation positioning;

[0025] S2) The given linear speed is a fixed value;

[0026] S3) calculating the lateral offset error, cumulative lateral offset error, and heading error from the center of the front axle of the front wheel to the arc path;

[0027] S4) determining the PID coefficient and calculating the dynamic front wheel deflection angle value corresponding to the PID;

[0028] S5) determining a static deflection angle value corresponding to the front tire;

[0029] S6) determining a final front wheel deflection angle value;

[0030] S7) outputting the calculated final front wheel deflection angle w as the actual control value to the controller to control the front wheel to deflect according to the set value;

[0031] S8) Return to step 2) and perform calculation in a loop.

[0032] In the straight line mode:

[0033] Step 3) is this:

[0034] Through steps 1) and 2), first, calculate the lateral offset error of the front wheel from the center of the front axle to the arc path and record it as , and the lateral error is set to positive when the front wheel is outside the path, and negative when the front wheel is inside the path;

[0035] Next, calculate the cumulative lateral offset error and record it as , the cumulative lateral offset error is the cumulative sum of the lateral offset errors calculated from the starting time to the current time;

[0036] Then, the heading error is calculated as , with counterclockwise as positive, the heading error is the front wheel heading and is recorded as and the reference heading is recorded as The difference, that is , where the reference heading is the corresponding tangent direction of the front wheel at the nearest point on the arc;

[0037] Step 4) is to calculate the lateral error in step 3) , cumulative lateral error and heading error After that, the PID parameters are determined through debugging and the corresponding dynamic front wheel deflection angle is obtained. ;

[0038] Step 5) is as follows, the final front wheel deflection angle used for control is recorded as , the dynamic front wheel deflection angle obtained by step 4) As the final front wheel deflection angle value used for control, that is ;

[0039] And / or, in the turning mode:

[0040] Step S3) is as follows:

[0041] Through step S1) and step S2), first, calculate the lateral offset error of the front wheel from the center of the front axle to the arc path and record it as , and the lateral error is set to positive when the front wheel is outside the path, and negative when the front wheel is inside the path;

[0042] Next, calculate the cumulative lateral offset error and record it as , the cumulative lateral offset error is the cumulative sum of the lateral offset errors calculated from the starting time to the current time;

[0043] Then, the heading error is calculated as , with counterclockwise as positive, the heading error is the front wheel heading and is recorded as and the reference heading is recorded as The difference, that is , where the reference heading is the corresponding tangent direction of the front wheel at the nearest point on the arc;

[0044] Step S4) is to calculate the lateral error in step S3) , cumulative lateral error and heading error After that, the PID parameters are determined through debugging, and the corresponding dynamic front wheel deflection angle is recorded as ,

[0045] ;

[0046] Step S5) is based on the wheelbase The turning radius is recorded as R, and the static deflection angle value corresponding to the front tire is recorded as ,

[0047] ;

[0048] Step 6) is to calculate the final front wheel deflection angle used for control based on the dynamic front wheel deflection angle and the static front wheel deflection angle: .

[0049] Both step 1) and step S1) obtain the magnetic navigation positioning of the two magnetic sensors; both step 3) and step S3) are performed as follows: when the two magnetic sensors simultaneously sense the magnetic nail, the true value of the lateral error directly sensed by the magnetic sensor is used as the correction value instead of the lateral offset error for calculation; when the two magnetic sensors do not simultaneously sense the magnetic nail, the sensor data of the odometer or inertial measurement unit is obtained to calculate the lateral offset error based on the latest correction value.

[0050] AGV vehicles use different modes for control in different sections of the road. Straight mode is used for straight sections and turning mode is used for arc sections. The mode is automatically switched at the connection point between the straight section and the arc section. The rule for switching modes is as follows: taking the center of the line connecting the front and rear wheel axles of the vehicle as the reference point, the driving trajectory of the reference point is connected by a straight line and an arc. Taking the straight section as an example, starting from the straight section, it is controlled in straight mode; when the reference point runs to the connection point of the straight track and the arc track, it switches from straight mode to turning mode for control and moves along the arc; when the reference point continues to run to the connection point of the arc and the straight track, it switches from turning mode to straight mode for control.

[0051] By adopting the above technical solution, the beneficial effects of the present invention are as follows: a magnetic nail positioning method suitable for front and rear dual magnetic sensors of the present invention is suitable for vehicles with independent steering chassis control of the front and rear axles. According to the two front and rear magnetic sensors, the magnetic nail route is divided into two combinations of straight lines and fixed radius arcs. The straight line route and the arc route are combined into the entire AGV movement route. An equally spaced straight line magnetic nail arrangement is adopted in pure straight lines, an equally spaced arc arrangement is adopted in pure arcs, and a staggered arrangement is adopted in mixed sections. The staggered arrangement can avoid the situation where one sensor senses a magnetic nail in another position on a mixed section. The magnetic nail positioning information can be sensed by two sensors simultaneously to be considered valid data, which can avoid the magnetic sensor reading and processing erroneous magnetic nail data. The present invention is conducive to the implementation of a pure magnetic nail positioning method for AGVs in factory logistics.

[0052] The above-mentioned AGV tracking control method is based on the above-mentioned magnetic nail positioning arrangement method suitable for dual magnetic sensing. The tracking control method on the path of the magnetic nail arrangement is mainly suitable for AGV vehicles whose front wheel axle and rear wheel axle can be independently steered and controlled, and whose chassis system cannot be turned in place. It performs tracking control on straight and circular paths. This method is a magnetic navigation control method that combines two control modes, straight line and turning. Its turning control method is a dynamic deflection angle calculation of a fixed radius turning mode plus a PID control method of a static deflection angle. The method of the present invention adds a fixed control amount corresponding to the turning radius. When tracking a circular path with a fixed radius, the tracking effect of the AGV when performing a fixed radius turn is similar to that when tracking a straight path, thereby avoiding the situation where the larger the turning radius during magnetic navigation, the larger the tracking error, resulting in AGV tracking loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 The present invention relates to a schematic diagram of a route from a straight line to an arc in a magnetic nail positioning arrangement method suitable for dual magnetic sensing.

[0054] Figure 2 The present invention relates to a schematic diagram of a route from an arc to a straight line in a magnetic nail positioning arrangement method suitable for dual magnetic sensing.

[0055] Figure 3 The present invention relates to a route diagram of a straight line divided into two circular arcs in different directions in a magnetic nail positioning arrangement method suitable for dual magnetic sensing.

[0056] Figure 4 The present invention relates to a route diagram of a magnetic nail positioning arrangement method suitable for dual magnetic sensing, in which a straight line is extended and divided into an arc.

[0057] Figure 5 The present invention relates to a route diagram of multiple combinations of straight lines and circular arcs in a magnetic nail positioning arrangement method suitable for dual magnetic sensing.

[0058] Figure 6 and Figure 7 The present invention relates to a magnetic nail positioning arrangement method suitable for dual magnetic sensing, which is applicable to a dual PID tracking control method of an AGV with independent steering of the front and rear axles, and schematic diagrams of three coordinate systems of the vehicle in different modes.

[0059] Figure 8 The present invention relates to a magnetic nail positioning arrangement method suitable for dual magnetic sensing, which is applicable to a schematic diagram of the connection points of the switching mode in the dual PID tracking control method of the front and rear axle independent steering AGV. DETAILED DESCRIPTION

[0060] In order to further explain the technical solution of the present invention, the present invention is described in detail below through specific embodiments.

[0061] This embodiment discloses a magnetic nail positioning arrangement method suitable for dual magnetic sensing. A vehicle using the magnetic nail positioning arrangement method of the present invention has a chassis system in which the front wheels and rear wheels respectively have front axles and rear axles that can be independently steered. Magnetic sensors are respectively provided at the center of the front axle and the center of the rear axle on the vehicle, that is, the vehicle has dual magnetic sensors. The magnetic nail positioning arrangement method includes a magnetic nail arrangement process, and the specific magnetic nail arrangement process is as follows.

[0062] 1) With the center point of the front axle and rear axle of the vehicle as the reference point, the magnetic nail layout route is determined according to the moving trajectory of the reference point. The magnetic nail layout route is composed of only straight lines and various arcs of fixed radius. The various arcs of fixed radius, that is, the turning radius of each turning section, is a fixed value, such as Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 and Figure 5 As shown in the schematic diagrams of several routes, according to the vehicle driving, the dual magnetic sensors sense the intersection of the arc and the straight line in the magnetic nail arrangement route to form a mixed section of arc intersection segments and straight line intersection segments. The two ends of the arc intersection segment and the straight line intersection segment are the intersection points of the straight line and the arc, such as intersection point 1 and intersection point 2 shown in the figure.

[0063] 2) Determine the wheelbase between the front axle and the rear axle, use the wheelbase as the magnetic pin induction spacing distance d, divide the magnetic pin induction spacing distance d by an integer, and determine the magnetic pin arrangement spacing distance s.

[0064] 3) Take a point on the non-straight intersection of one of the straight lines or a point on the non-arc intersection of one of the arcs as the first placement starting point, and start from the first placement starting point to place the magnetic nails in sequence at equal intervals on the straight line or arc according to the arrangement interval distance s.

[0065] 4) Ensure that magnetic pins are placed at both intersection points of the straight line (or arc) and the arc (or straight line).

[0066] 5) Continue to place magnetic nails on the arcs connected by straight lines or continue to place magnetic nails on the straight lines connected by arcs. The interval point of the connected arc or straight line from the first intersection point of the previous straight line or arc is the set intersection interval distance ss as the second placement starting point. Starting from the second placement starting point, magnetic nails are arranged in sequence on the connected straight line or arc according to the arrangement interval distance s. The intersection interval distance ss should be greater than or less than the arrangement interval distance s to ensure that the magnetic nails on the arc intersection segment and the straight line intersection segment are staggered.

[0067] If there are more connected straight lines or arcs to be arranged with magnetic pins, repeat step 5) to place magnetic pins until the arrangement is completed.

[0068] When the above-mentioned magnetic nail positioning arrangement method is used, its program processing is such that the front and rear magnetic sensors pass along the magnetic nail arrangement route as the vehicle moves. The program only considers the data as valid data for processing when the two magnetic sensors read the magnetic nail data at the same time. This can avoid the situation where, on mixed road sections, one magnetic sensor misreads the magnetic nail data of other sections. The other magnetic sensor will not sense the magnetic nail due to the misplaced magnetic nail arrangement, and the erroneous data will not be processed at this time. That is, only correct data will be sensed and processed by the two magnetic sensors at the same time or nearly at the same time.

[0069] The above methods can be used for Figure 1-Figure 5 The magnetic positioning layout method of several routes and the combination of these routes is applied.

[0070] like Figure 1 As shown, the magnetic nail arrangement route from a straight line to an arc path. Assuming that the starting point is a straight line, for the starting straight line path, the magnetic nails are arranged at equal intervals of s starting from the starting point of the straight line in the figure until they are arranged at the last intersection of the straight line and the arc, which is intersection 2 in the figure.

[0071] After the straight lines and intersections are arranged, start arranging the magnetic pins on the arc. If you start arranging them at equal intervals starting from the magnetic pins at intersection 1 in the figure, the magnetic pins on the arc and the magnetic pins on the straight line will be too close in the mixed section, and they will be sensed at the same time during work, which will interfere with the calculation of the magnetic pin positioning. Therefore, the arc cannot be arranged starting from the position corresponding to intersection 1 in the figure. Instead, the intersection spacing distance ss set from the intersection magnetic pin interval should be used as the new starting point, and the intersection spacing distance ss should be less than or greater than the arrangement spacing distance s to ensure that the magnetic pins on the arc are completely staggered with the magnetic pins on the straight line.

[0072] like Figure 2 As shown in the figure, the arrangement of magnetic pins from an arc to a straight line path is as follows. Assuming that the starting point is somewhere in the arc, for the arc path, the magnetic pins are arranged at equal intervals s from the starting point until they are arranged at the last intersection of the arc and the straight line. Figure 2 Intersection point 2.

[0073] After the arc is arranged, start to arrange the magnetic nails on the straight line. Figure 2 If the magnetic pins are arranged at equal intervals starting from the intersection point 1, the mixed sections of the straight and arc magnetic pins will be too close, which will interfere with the positioning of the magnetic pins. Therefore, the straight line cannot use the intersection point as the starting magnetic pin. Instead, the new starting point should be set at the intersection interval distance ss away from the intersection magnetic pin. ss should be less than or greater than s. Then, starting from the new starting point, the magnetic pins are arranged at equal intervals s to ensure that the arc magnetic pins are completely staggered with the straight path.

[0074] There may be three routes converging into one section. Figure 3 The figure shows a situation where a straight line segment is divided into two arcs (arc 1 and arc 2 in the figure). This situation is equivalent to the superposition of two straight line-arc segments. To simplify the arrangement of magnetic nails, the intersection of the two straight line-arc segments is set to the same point. Then the arrangement of magnetic nails is equivalent to the superposition of a straight line-left turn arc and a straight line-right turn arc. Figure 1 Then add the arc arrangement on the other side.

[0075] Figure 4 In the figure, a straight line is divided into an arc and a straight line at a certain point. This is even simpler. Just continue to distribute the straight lines at equal intervals and then start as above. Figure 1 The magnetic nails are arranged in a circular arc manner.

[0076] Through the above specific implementation methods, it can be seen that the above methods can form any path, such as Figure 5 As shown, the entire route consists of straight lines and arcs, that is, a straight line-arc-straight line route, which is Figure 1 Add the following method after Figure 2 Arrangement of the method.

[0077] The AGV tracking control method for arranging magnetic nails on a path using the magnetic nail positioning arrangement method suitable for dual magnetic sensing is implemented. The front axle of the front wheels and the rear axle of the rear wheels of the AGV vehicle can be independently steered. The tracking control method includes tracking control of a straight path, which is recorded as a straight line mode, and tracking control of a turning path, which is recorded as a turning mode. Since the present invention is directed to AGV vehicles with independently steerable front and rear axles, the front and rear wheels of the vehicle can be independently steered. Whether in the straight line mode or the turning mode, the method steps executed in the tracking control method for the rear wheels can be obtained equivalently with reference to the front wheels. The following mainly describes the tracking control method steps using the front wheels as an example.

[0078] In the linear mode, it is a common PID control mode, and the tracking control method steps are as follows:

[0079] 1) Obtain magnetic navigation positioning.

[0080] During tracking control, we focus on three coordinate systems: the vehicle front wheel coordinate system, the vehicle rear wheel coordinate system, and the vehicle center coordinate system. Figure 6 As shown, through the relationship between these coordinate systems, the positioning of the vehicle center relative to the magnetic navigation coordinate system is obtained, and the positioning of the vehicle center in the magnetic navigation coordinate system is obtained.

[0081] 2) The given linear speed is a fixed value.

[0082] The linear speed of the front and rear wheels of the vehicle is consistent, and a linear speed value is given.

[0083] 3) Calculate the lateral offset error, cumulative lateral offset error, and heading error from the center of the front axle of the front wheel to the straight path.

[0084] Through steps 1) and 2), first, calculate the lateral offset error of the front wheel from the center of the front axle to the straight path and record it as ,like Figure 6 As shown, that is, the shortest distance between the front wheel and the path, and when the front wheel is outside the path, the lateral error is set to be positive, and when it is inside the path, the lateral error is set to be negative;

[0085] Next, calculate the cumulative lateral offset error and record it as , the cumulative lateral offset error is the cumulative sum of the lateral offset errors calculated from the starting time to the current time;

[0086] Then, the heading error is calculated as ,like Figure 6 As shown, counterclockwise is positive, and the heading error is the front wheel heading. and the reference heading is recorded as The difference, that is , where the reference heading is the corresponding tangent direction of the front wheel at the nearest point on the arc, such as Figure 6 Direction of arrow shown.

[0087] 4) Determine the PID coefficient and calculate the dynamic front wheel deflection angle value corresponding to the PID.

[0088] In step 3) calculate the lateral error , cumulative lateral error and heading error After that, the PID parameters are determined through debugging and the corresponding dynamic front wheel deflection angle is obtained. .

[0089] 5) Determine the final front wheel deflection angle value.

[0090] The final front wheel deflection angle used for control is recorded as , the dynamic front wheel deflection angle obtained by step 4) As the final front wheel deflection angle value used for control, that is The calculation method for the rear wheel deflection angle is the same as that for the front wheel deflection angle.

[0091] 6) The final calculated front wheel deflection angle w is output to the controller as the actual control value, controlling the front wheel to deflect according to the set value.

[0092] 7) Return to step 2) and perform calculations in a loop to achieve PID tracking control of the vehicle's front wheels.

[0093] The method steps for PID tracking control of the rear wheels of the vehicle are consistent with the method steps for PID tracking control of the front wheels. Those skilled in the art can directly substitute the above content to deduce it. They will not be repeated in this embodiment, and will not affect the clear understanding of the technical solution of the present invention by those skilled in the art.

[0094] In the turning mode with a fixed turning radius, a PID control method with a static value plus dynamic adjustment is used. The tracking control method steps are as follows:

[0095] S1) Obtain magnetic navigation positioning.

[0096] During tracking control, we focus on three coordinate systems: the vehicle front wheel coordinate system, the vehicle rear wheel coordinate system, and the vehicle center coordinate system. Figure 7 As shown, through the relationship between these coordinate systems, the positioning of the vehicle center relative to the magnetic navigation coordinate system is obtained, and the positioning of the vehicle center in the magnetic navigation coordinate system is obtained.

[0097] S2) The given linear speed is a fixed value.

[0098] The linear speed of the front and rear wheels of the vehicle is consistent, and a linear speed value is given.

[0099] S3) Calculate the lateral offset error, cumulative lateral offset error, and heading error from the front axle center of the front wheel to the arc path.

[0100] Through step S1) and step S2), first, calculate the lateral offset error of the front wheel from the center of the front axle to the arc path and record it as ,like Figure 7 As shown, that is, the shortest distance between the front wheel and the path, and when the front wheel is outside the path, the lateral error is set to be positive, and when it is inside the path, the lateral error is set to be negative;

[0101] Next, calculate the cumulative lateral offset error and record it as , the cumulative lateral offset error is the cumulative sum of the lateral offset errors calculated from the starting time to the current time;

[0102] Then, the heading error is calculated as ,like Figure 7 As shown, counterclockwise is positive, and the heading error is the front wheel heading. and the reference heading is recorded as The difference, that is , where the reference heading is the corresponding tangent direction of the front wheel at the nearest point on the arc, such as Figure 7 Direction of arrow shown.

[0103] S4) Determine the PID coefficient and calculate the dynamic front wheel deflection angle value corresponding to the PID.

[0104] In step S3) the lateral error is calculated , cumulative lateral error and heading error After that, the PID parameters are determined through debugging, and the corresponding dynamic front wheel deflection angle is recorded as .

[0105] .

[0106] S5) is recorded according to the wheelbase The turning radius is recorded as R, and the static deflection angle value corresponding to the front tire is recorded as .

[0107]

[0108] S6) Calculate the final front wheel deflection angle value.

[0109] According to the dynamic front wheel deflection angle and the static front wheel deflection angle, the final front wheel deflection angle used for control is calculated as The calculation method for the rear wheel deflection angle is the same as that for the front wheel deflection angle.

[0110] S7) The calculated final front wheel deflection angle w is output to the controller as the actual control value, and the front wheel is controlled to deflect according to the set value.

[0111] S8) Return to step S2) and perform calculations in a loop to achieve PID tracking control of the front wheels of the vehicle.

[0112] The method steps for PID tracking control of the rear wheels of the vehicle are consistent with the method steps for PID tracking control of the front wheels. Those skilled in the art can directly substitute the above content to deduce it. They will not be repeated in this embodiment, and will not affect the clear understanding of the technical solution of the present invention by those skilled in the art.

[0113] When AGV vehicles are in use, different modes are used for control in different sections of the road. The principle is to use the straight line mode control in the straight section and the turning mode control in the arc section, and stop and switch at the connection point. The purpose of stopping and switching is to prevent the vehicle from deviating too much from the track. Figure 8As shown, when starting from the left straight line, the vehicle is in straight line mode control. When it moves to connection point 1, it switches from straight line mode to turning mode control. When the vehicle continues to move to connection point 2, it switches from turning mode to straight line mode control. Specific description: Taking the center of the line connecting the front and rear wheel axles of the vehicle as the reference point, the driving trajectory of the reference point is connected by a straight line and an arc. Taking starting from a straight section as an example, the mode switching rules are as follows: starting from a straight section, control is performed in straight line mode; when the reference point moves to the connection point of the straight line trajectory and the circular arc trajectory (i.e., as shown in the figure, connection point 1, about to enter the circular arc section), control is switched from straight line mode to turning mode and moves along the arc; when the reference point continues to move to the connection point of the circular arc and the straight line trajectory (i.e., as shown in the figure, connection point 2, about to enter the straight line section), control is switched from turning mode to straight line mode and returns to step 2 of straight line mode).

[0114] In addition, the AGV vehicle in this embodiment is respectively provided with a magnetic sensor at the center of the front axle of the front wheel and the center of the rear axle of the rear wheel, and the two magnetic sensors respectively sense the magnetic nails on the path. During operation; step 1) and step S1) both obtain the magnetic navigation positioning of the two magnetic sensors; step 3) and step S3) are both performed in the following manner: when the two magnetic sensors sense the magnetic nails at the same time, the true value of the lateral error obtained by direct sensing by the magnetic sensors is used as the correction value instead of the lateral offset error for calculation; when the two magnetic sensors do not sense the magnetic nails at the same time, the data of any sensor such as the odometer or inertial measurement unit that can perform relative motion inference is obtained, and the lateral offset error is calculated based on the latest correction value, that is, the data of the two magnetic sensors is used as the correction value, and the data of other sensors such as the odometer or inertial measurement unit is used as the predicted value to calculate the lateral error of the front wheel or rear wheel relative to the reference path.

[0115] The above embodiments and drawings do not limit the product form and style of the present invention. Any appropriate changes or modifications made by ordinary technicians in the relevant technical field should be deemed to be within the patent scope of the present invention.

Claims

1. A magnetic nail positioning method suitable for dual magnetic sensing, characterized in that: A vehicle including a magnetic pin positioning arrangement has a chassis system in which the front wheels and rear wheels respectively have a front axle and a rear axle capable of independent steering control. The vehicle is provided with magnetic sensors at the center of the front axle and the center of the rear axle, respectively. The magnetic pin positioning arrangement method includes a magnetic pin arrangement process, and the specific magnetic pin arrangement process is as follows: 1) With the center point of the front and rear axles of the vehicle as the reference point, the magnetic nail layout route is determined according to the movement trajectory of the reference point. The magnetic nail layout route is composed only of straight lines and various arcs of fixed radius. The intersection of the arc and the straight line in the magnetic nail layout route forms an arc intersection segment and a straight line intersection segment. The two ends of the arc intersection segment and the straight line intersection segment are the intersection points of the straight line and the arc. 2) Determine the wheelbase between the front axle and the rear axle, use the wheelbase as the magnetic pin induction spacing distance d, divide the magnetic pin induction spacing distance d by an integer, and determine the magnetic pin arrangement spacing distance s; 3) Take a point on the non-straight intersection of a straight line or a point on the non-circular intersection of an arc as the first placement starting point, and start from the first placement starting point to place magnetic nails in sequence at equal intervals on the straight line or arc according to the arrangement interval s; 4) Ensure that magnetic pins are placed at both intersections of the straight line and the arc; 5) Continue to place magnetic nails on the arcs connected by straight lines or continue to place magnetic nails on the straight lines connected by arcs. The interval point of the connected arc or straight line from the first intersection of the previous straight line or arc to the set intersection interval ss is the second placement starting point. Starting from the second placement starting point, magnetic nails are arranged in sequence on the connected straight line or arc according to the arrangement interval s. The intersection interval ss should be greater than or less than the arrangement interval s to ensure that the magnetic nails on the arc intersection segment and the straight line intersection segment are staggered.

2. The AGV tracking control method on the path of the magnetic nails arranged in the magnetic nail positioning method suitable for dual magnetic sensing according to claim 1 is characterized in that: The two magnetic sensors on the AGV vehicle respectively sense the magnetic nails on the path. The tracking control method includes tracking control of a straight path, which is recorded as a straight mode, and tracking control of a turning path, which is recorded as a turning mode. The tracking control execution of the straight mode and the turning mode includes tracking control of the front wheels and the rear wheels. Since the front wheels and the rear wheels can be independently steered, the tracking control method is described using the tracking control execution of the front wheels as an example. The execution method steps of the rear wheels can be obtained by referring to the front wheels. The steps of the front wheel tracking control method in the straight mode and / or the turning mode are as follows: Straight line mode: 1) Obtain magnetic navigation positioning; 2) The given linear speed is a fixed value; 3) Calculate the lateral offset error, cumulative lateral offset error, and heading error from the center of the front axle of the front wheel to the straight path; 4) Determine the PID coefficient and calculate the dynamic front wheel deflection angle value corresponding to the PID; 5) Determine the final front wheel deflection angle value; 6) The calculated final front wheel deflection angle w is output to the controller as the actual control value, controlling the front wheel to deflect according to the set value; 7) Return to step 2) and perform calculations in a loop to achieve PID tracking control of the vehicle's front wheels; Turning Mode: S1) Obtain magnetic navigation positioning; S2) The given linear speed is a fixed value; S3) calculating the lateral offset error, cumulative lateral offset error, and heading error from the center of the front axle of the front wheel to the arc path; S4) determining the PID coefficient and calculating the dynamic front wheel deflection angle value corresponding to the PID; S5) determining a static deflection angle value corresponding to the front tire; S6) determining a final front wheel deflection angle value; S7) outputting the calculated final front wheel deflection angle w as the actual control value to the controller to control the front wheel to deflect according to the set value; S8) Return to step 2) and perform calculation in a loop; In the straight line mode: Step 3) is this: Through steps 1) and 2), first, calculate the lateral offset error of the front wheel from the center of the front axle to the arc path and record it as , and the lateral error is set to positive when the front wheel is outside the path, and negative when the front wheel is inside the path; Next, calculate the cumulative lateral offset error and record it as , the cumulative lateral offset error is the cumulative sum of the lateral offset errors calculated from the starting time to the current time; Then, the heading error is calculated as , with counterclockwise as positive, the heading error is the front wheel heading and is recorded as and the reference heading is recorded as The difference, that is , where the reference heading is the corresponding tangent direction of the front wheel at the nearest point on the arc; Step 4) is to calculate the lateral error in step 3) , cumulative lateral error and heading error After that, the PID parameters are determined through debugging and the corresponding dynamic front wheel deflection angle is obtained. , Step 5) is as follows, the final front wheel deflection angle used for control is recorded as , the dynamic front wheel deflection angle obtained by step 4) As the final front wheel deflection angle value used for control, that is ; And / or, in the turning mode: Step S3) is as follows: Through step S1) and step S2), first, calculate the lateral offset error of the front wheel from the center of the front axle to the arc path and record it as , and the lateral error is set to positive when the front wheel is outside the path, and negative when the front wheel is inside the path; Next, calculate the cumulative lateral offset error and record it as , the cumulative lateral offset error is the cumulative sum of the lateral offset errors calculated from the starting time to the current time; Then, the heading error is calculated as , with counterclockwise as positive, the heading error is the front wheel heading and is recorded as and the reference heading is recorded as The difference, that is , where the reference heading is the corresponding tangent direction of the front wheel at the nearest point on the arc; Step S4) is to calculate the lateral error in step S3) , cumulative lateral error and heading error After that, the PID parameters are determined through debugging, and the corresponding dynamic front wheel deflection angle is recorded as , ； Step S5) is based on the wheelbase The turning radius is recorded as R, and the static deflection angle value corresponding to the front tire is recorded as , ； Step 6) is to calculate the final front wheel deflection angle used for control based on the dynamic front wheel deflection angle and the static front wheel deflection angle: ; Both step 1) and step S1) obtain the magnetic navigation positioning of the two magnetic sensors; both step 3) and step S3) obtain the true value of the lateral error by direct sensing through the magnetic sensors as the correction value instead of the lateral offset error for calculation when the two magnetic sensors sense the magnetic nail at the same time, and when the two magnetic sensors do not sense the magnetic nail at the same time, obtain the sensor data of the odometer or inertial measurement unit and calculate the lateral offset error based on the latest correction value.

3. The AGV tracking control method according to claim 2, characterized in that: AGV vehicles use different modes for control in different sections. The straight line mode is used for straight sections, and the turning mode is used for arc sections. The mode is automatically switched at the connection point between the straight and arc sections. The rule for switching modes is as follows: the center of the line connecting the front and rear wheel axles of the vehicle is used as the reference point, and the driving trajectory of the reference point is connected by a straight line and an arc. Taking the straight line section as an example, the AGV vehicle is controlled in the straight line mode when it starts from the straight line section. When the reference point moves to the connection point of the straight track and the circular arc track, the control is switched from the straight line mode to the turning mode and moves along the arc; when the reference point continues to move to the connection point of the circular arc and the straight line track, the control is switched from the turning mode to the straight line mode.

Images