Curve speed limit calculation system and method

Abstract

This invention discloses a cornering speed limit calculation module for use in an intelligent driving assistance system. It includes: a lateral acceleration speed limit unit, a vehicle motion state estimation curvature radius speed limit unit, a steering wheel angle speed limit unit, and a perception data estimation curvature speed limit unit. These units obtain the desired acceleration, a first acceleration rate of change limit, and a second acceleration rate of change limit based on different parameters. An acceleration limiting output unit takes the minimum value among the desired accelerations obtained by the above units to obtain the cornering desired acceleration to be limited. It then takes the smaller value of the first and second acceleration rate of change limits to obtain the minimum acceleration rate of change limit, performs limiting processing on the cornering desired acceleration to be limited, and calculates the final vehicle cornering desired acceleration. This invention improves the smoothness of cornering pre-deceleration and speed limiting, enhances cornering speed limiting performance, and improves vehicle cornering safety.

Description

Technical Field

[0001] This invention relates to the automotive field, and in particular to a curve speed limit calculation system and method for intelligent driving assistance systems. Background Technology

[0002] Thanks to its lower cost and superior applicability and effectiveness, vision-based intelligent driving assistance systems still dominate the market, with the number of vehicles equipped with these systems increasing daily and their full-scenario coverage gradually improving.

[0003] In cornering-assisted driving scenarios, consumers have raised more demands for features such as corner pre-deceleration and speed limiting, increasing the requirements for smooth cornering performance. However, adaptive cruise control systems based on vision perception often lack corner pre-deceleration or have uneven speed limiting processes in cornering scenarios. This not only affects passenger comfort on curves but also significantly impacts the control performance of lateral assist functions.

[0004] Chinese patent CN201610837956.6 discloses a machine vision-based method for calculating speed limits on curves and an overspeed warning device. The method includes the following steps: measuring the visible distance on curves and other road sections with poor visibility; calculating a safe speed that ensures the vehicle can stop in time when encountering a tight situation based on the visible distance; comparing the safe speed with the current speed, and issuing a warning to the driver if the current speed exceeds the safe speed. This method is based on an onboard device, requires no road infrastructure cooperation, and has advantages such as low cost, simple calculation, fast processing speed, and high reliability. It prevents drivers from assuming good road conditions ahead, leading to insufficient braking distance and traffic accidents, and provides support for theoretical methods of safe speed control on poor road sections. However, this solution fails to address the technical problem of lack of pre-deceleration or uneven speed limiting processes in curve scenarios, which affects passenger comfort during curve rides.

[0005] Chinese patent CN202211288424.3 discloses a method for limiting the speed of autonomous vehicles on curves, comprising: obtaining the longitudinal cumulative distance and scattered curvature radius of each path point of the reference path to obtain the curvature radius of each path point, and obtaining the target speed limit value through a comfort cornering speed calibration table for the current curve speed limit scenario; calculating the predicted position of the vehicle at a preset time based on a preset kinematic model, solving for the target speed limit value to obtain a speed sequence, and determining the current intention of the autonomous vehicle; matching the corresponding entry-to-curve aiming time or exit-to-curve aiming time according to the current intention, determining the entry-to-curve deceleration action or exit-to-curve acceleration action, and performing a linear transition on the speed sequence through a quadratic programming algorithm to generate a curve speed limit control strategy for the autonomous vehicle. Therefore, this application can be applied to different scenarios, improves the rationality of curve speed limit planning, and greatly improves the user's driving experience while ensuring vehicle safety. Summary of the Invention

[0006] The summary of this invention introduces a series of simplified concepts, all of which are simplifications of existing technologies in the field, and will be further explained in detail in the detailed description section. This summary is not intended to limit the key features and essential technical features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.

[0007] The technical problem this invention aims to solve is to provide a method for selecting desired acceleration based on vehicle kinematics data and visual perception data, limiting the upper limit of lateral acceleration for curves with different curvatures, thereby improving the smoothness of pre-deceleration and speed limiting in curves and enhancing vehicle safety during cornering.

[0008] To solve the above-mentioned technical problems, the present invention provides a curve speed limit calculation module for use in an intelligent driving assistance system, comprising:

[0009] The lateral acceleration limiting unit obtains the desired acceleration for the curve and the first acceleration rate of change limit by querying the desired acceleration table and the acceleration rate of change limit table based on the lateral acceleration and vehicle speed.

[0010] The vehicle motion state estimation curvature radius speed limiting unit obtains the curvature radius of the curve based on the vehicle's lateral acceleration and speedometer, and obtains the expected acceleration of the curve by looking up the expected acceleration table based on the curvature radius of the curve and the lateral acceleration.

[0011] The steering wheel angle speed limiting unit looks up the desired acceleration table based on the vehicle's steering wheel angle and vehicle speed, and looks up the acceleration change rate limit table by linear interpolation based on the vehicle's steering wheel angle and vehicle speed to obtain the desired acceleration for cornering and the second acceleration change rate limit.

[0012] The perception data estimation curvature speed limiting unit estimates the curvature of the vehicle's current and forward positions based on the lane line equations output by the visual perception data, calculates the curve radius of the vehicle's current and forward positions, and constructs a desired speed table by taking the smallest radius among the curve radii. Different curvature radii correspond to different desired vehicle speeds. Based on the speed error input, it uses PID control to divide the error segments and constructs an upper and lower limit table of desired acceleration to obtain the desired acceleration for the curve.

[0013] The acceleration limiting output unit takes the minimum value among the desired accelerations obtained by the above units to obtain the desired acceleration for the curve to be limited. It takes the smaller value of the first acceleration change rate limit and the second acceleration change rate limit to obtain the minimum acceleration change rate limit. It performs limiting processing on the desired acceleration for the curve to be limited and calculates the final desired acceleration for the vehicle in the curve.

[0014] Optional, the lateral acceleration limiting unit processing includes;

[0015]

[0016] a1(k)=a(v h (k),a Lat (k)) (2);

[0017] j1(k)=j(v h (k),a Lat (k)) (3);

[0018] ω(k) represents the yaw rate of the vehicle, v h (k) represents the vehicle speed, a Lat (k) represents the lateral acceleration, a1(k) represents the desired acceleration in the curve, and j1(k) represents the first acceleration rate limit.

[0019] Optional, the vehicle motion state estimation curvature radius speed limiting unit processing includes;

[0020]

[0021]

[0022] v h (k) represents the vehicle speed, a Lat (k) represents the vehicle's lateral acceleration. Let a2(k) represent the radius of curvature of the curve, and let a2(k) represent the desired acceleration of the curve.

[0023] Optional, the steering wheel angle speed limiting unit processing includes;

[0024]

[0025]

[0026]

[0027] k represents the current calculation time, and θ(k) represents the steering wheel angle in units of angle. v represents the steering wheel angle in radians. h (k) represents the vehicle speed, a3(k) represents the desired acceleration in the curve, and j2(k) represents the second acceleration change rate limit.

[0028] Optional, the processing of the perceived data estimation curvature limiting unit includes;

[0029] y(k)=c0(k)+c1(k)·x(k)+c2(k)·x(k) 2 +c3(k)·x(k) 3(9);

[0030] y′(k)=c1(k)+2c2(k)·x(k)+3c3(k)·x(k) 2 (10);

[0031] y″(k)=2c2(k)+6c3(k)·x(k) (11);

[0032] x pre (k)=x(v h (k)) (12);

[0033]

[0034]

[0035] R′(k)=min{R cur (k),R pre (k)} (15);

[0036] v dsr (k)=v(R′(k)) (16);

[0037] Δv(k)=v dsr (k)-v h (k) (17);

[0038] a4(k)=min{max{a4(k-1),a lo (Δv(k))},a up (Δv(k))} (18);

[0039] Equation (9) represents the lane line equation output by visual perception data, Equation (10) represents the expression for calculating the first derivative of Equation (9), and Equation (11) represents the expression for calculating the second derivative of Equation (9).

[0040] k represents the current calculation time, y represents the lateral position with the vehicle camera position as the origin, x represents the vehicle's position in the positive direction of travel, the x and y axes follow the left-hand rule, c0, c1, c2, and c3 represent the lane line equation coefficients, x pre (k) represents the aiming distance at different vehicle speeds, v h (k) represents the vehicle speed, R cur (k) represents the radius of curvature of the vehicle's current position, R pre (k) represents the radius of curvature of the vehicle's pre-aiming position, R′(k) represents the estimated minimum radius, v dsr (k) represents the desired vehicle speed corresponding to the radius of curvature of the curve, Δv(k) represents the speed error, and a4(k) represents the desired acceleration of the curve.

[0041] Optional, the acceleration limiting output unit processing includes;

[0042]

[0043] j(k)=min{j1(k),j2(k)} (20);

[0044]

[0045] T represents the calculation step size. Let j(k) represent the minimum expected acceleration in a curve to be limited, j(k) represent the minimum rate of change of acceleration limit, and a(k) represent the final expected acceleration of the vehicle in a curve.

[0046] To solve the above-mentioned technical problems, the present invention provides a method for calculating the speed limit on curves, which is used in an intelligent driving assistance system and includes the following steps;

[0047] S1. Based on the lateral acceleration and vehicle speed, query the expected acceleration table and the acceleration rate of change limit table to obtain the expected acceleration for the curve and the first acceleration rate of change limit;

[0048] S2, obtain the curve radius of curvature based on the vehicle's lateral acceleration and speedometer, and obtain the desired curve acceleration by looking up the desired acceleration table based on the curve radius of curvature and lateral acceleration;

[0049] S3. Based on the vehicle steering wheel angle and vehicle speed, look up the expected acceleration table, and based on the vehicle steering wheel angle and vehicle speed, look up the acceleration change rate limit linear interpolation table to obtain the expected acceleration for the curve and the second acceleration change rate limit.

[0050] S4 estimates the curvature of the vehicle's current and forward positions based on the lane line equations output from the visual perception data, calculates the curve radius of the vehicle's current and forward positions, and constructs a desired speed table by taking the smallest radius among the curve radii. Different curvature radii correspond to different desired vehicle speeds. Based on the speed error input, it uses PID control to divide the error segments and constructs an upper and lower limit table of desired acceleration to obtain the desired acceleration for curves.

[0051] S5. Take the minimum value among the expected accelerations obtained in the above units to obtain the expected acceleration of the curve to be limited. Take the smaller value of the first acceleration change rate limit and the second acceleration change rate limit to obtain the minimum acceleration change rate limit. Perform the curve limiting process on the expected acceleration of the curve to be limited, and calculate the final expected acceleration of the vehicle in the curve.

[0052] The execution order of steps S1 to S4 is not limited.

[0053] Optionally, when implementing step S1, the following may be included:

[0054]

[0055] a1(k)=a(v h (k),a Lat (k)) (2);

[0056] j1(k)=j(v h (k),a Lat (k)) (3);

[0057] ω(k) represents the yaw rate of the vehicle, v h (k) represents the vehicle speed, a Lat (k) represents the lateral acceleration, a1(k) represents the desired acceleration in the curve, and j1(k) represents the first acceleration rate limit.

[0058] Optionally, when implementing step S2, the following may be included:

[0059]

[0060]

[0061] v h (k) represents the vehicle speed, a Lat (k) represents the vehicle's lateral acceleration. Let a2(k) represent the radius of curvature of the curve, and let a2(k) represent the desired acceleration of the curve.

[0062] Optionally, when implementing step S3, the following may be included:

[0063]

[0064]

[0065]

[0066] k represents the current calculation time, and θ(k) represents the steering wheel angle in units of angle. v represents the steering wheel angle in radians. h (k) represents the vehicle speed, a3(k) represents the desired acceleration in the curve, and j2(k) represents the second acceleration change rate limit.

[0067] Optionally, when performing step S4, the following may be included:

[0068] y(k)=c0(k)+c1(k)·x(k)+c2(k)·x(k) 2 +c3(k)·x(k) 3 (9);

[0069] y′(k)=c1(k)+2c2(k)·x(k)+3c3(k)·x(k) 2 (10);

[0070] y″(k)=2c2(k)+6c3(k)·x(k) (11);

[0071] x pre (k)=x(v h (k)) (12);

[0072]

[0073]

[0074] R′(k)=min{R cur (k),R pre (k)} (15);

[0075] v dsr (k)=v(R′(k)) (16);

[0076] Δv(k)=v dsr (k)-v h (k) (17);

[0077] a4(k)=min{max{a4(k-1),a lo (Δv(k))},a up (Δv(k))} (18);

[0078] Equation (9) represents the lane line equation output by visual perception data, Equation (10) represents the expression for calculating the first derivative of Equation (9), and Equation (11) represents the expression for calculating the second derivative of Equation (9).

[0079] k represents the current calculation time, y represents the lateral position with the vehicle camera position as the origin, x represents the vehicle's position in the positive direction of travel, the x and y axes follow the left-hand rule, c0, c1, c2, and c3 represent the lane line equation coefficients, x pre (k) represents the aiming distance at different vehicle speeds, v h (k) represents the vehicle speed, R cur (k) represents the radius of curvature of the vehicle's current position, R pre (k) represents the radius of curvature of the vehicle's pre-aiming position, R′(k) represents the estimated minimum radius, v dsr (k) represents the desired vehicle speed corresponding to the radius of curvature of the curve, Δv(k) represents the speed error, and a4(k) represents the desired acceleration of the curve.

[0080] Optionally, when implementing step S5, the following may be included:

[0081]

[0082] j(k)=min{j1(k),j2(k)} (20);

[0083]

[0084] T represents the calculation step size. Let j(k) represent the minimum expected acceleration in a curve to be limited, j(k) represent the minimum rate of change of acceleration limit, and a(k) represent the final expected acceleration of the vehicle in a curve.

[0085] This invention considers vehicle kinematics data and visual perception data, proposing a vision-based cornering speed limiting strategy. By sensing the corner curvature and vehicle motion state in advance, it rationally plans the desired acceleration, improving the smoothness of pre-deceleration and speed limiting in corners, and enhancing cornering speed limiting performance. Simultaneously, this strategy can limit the upper limit of lateral acceleration in corners with different curvatures, improving vehicle cornering safety, and has broad application prospects and high market value. Attached Figure Description

[0086] The accompanying drawings are intended to illustrate the general characteristics of the methods, structures, and / or materials used in specific exemplary embodiments of the invention, supplementing the description in the specification. However, the drawings are schematic diagrams not drawn to scale and may not accurately reflect the precise structural or performance characteristics of any of the given embodiments. The drawings should not be construed as limiting or restricting the range of numerical values ​​or properties covered by exemplary embodiments of the invention. The invention will now be described in further detail with reference to the accompanying drawings and specific embodiments:

[0087] Figure 1 This is a block diagram of the control principle of the present invention. Detailed Implementation

[0088] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can fully understand other advantages and technical effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through different specific embodiments, and various details in this specification can also be applied based on different viewpoints, with various modifications or changes made without departing from the overall design concept of the invention. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. The following exemplary embodiments of the present invention can be implemented in many different forms and should not be construed as being limited to the specific embodiments set forth herein. It should be understood that these embodiments are provided to make the disclosure of the present invention thorough and complete, and to fully convey the technical solutions of these exemplary embodiments to those skilled in the art. It should be understood that when an element is referred to as "connected" or "combined" to another element, the element can be directly connected or combined to the other element, or there may be intermediate elements. The difference is that when an element is referred to as "directly connected" or "directly combined" to another element, there are no intermediate elements. Throughout the drawings, the same reference numerals always denote the same elements. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0089] First embodiment;

[0090] The curve speed limit calculation module provided by this invention is used in an intelligent driving assistance system and includes:

[0091] The lateral acceleration limiting unit obtains the desired acceleration for the curve and the first acceleration rate of change limit by querying the desired acceleration table and the acceleration rate of change limit table based on the lateral acceleration and vehicle speed.

[0092] The vehicle motion state estimation curvature radius speed limiting unit obtains the curvature radius of the curve based on the vehicle's lateral acceleration and speedometer, and obtains the expected acceleration of the curve by looking up the expected acceleration table based on the curvature radius of the curve and the lateral acceleration.

[0093] The steering wheel angle speed limiting unit looks up the desired acceleration table based on the vehicle's steering wheel angle and vehicle speed, and looks up the acceleration change rate limit table by linear interpolation based on the vehicle's steering wheel angle and vehicle speed to obtain the desired acceleration for cornering and the second acceleration change rate limit.

[0094] The perception data estimation curvature speed limiting unit estimates the curvature of the vehicle's current and forward positions based on the lane line equations output by the visual perception data, calculates the curve radius of the vehicle's current and forward positions, and constructs a desired speed table by taking the smallest radius among the curve radii. Different curvature radii correspond to different desired vehicle speeds. Based on the speed error input, it uses PID control to divide the error segments and constructs an upper and lower limit table of desired acceleration to obtain the desired acceleration for the curve.

[0095] The acceleration limiting output unit takes the minimum value among the desired accelerations obtained by the above units to obtain the desired acceleration for the curve to be limited. It takes the smaller value of the first acceleration change rate limit and the second acceleration change rate limit to obtain the minimum acceleration change rate limit. It performs limiting processing on the desired acceleration for the curve to be limited and calculates the final desired acceleration for the vehicle in the curve.

[0096] Optionally, the lateral acceleration limiting unit queries the desired acceleration table and the acceleration rate of change limit table based on the lateral acceleration and vehicle speed to obtain the desired cornering acceleration and the first acceleration rate of change limit, including:

[0097] The absolute value of the vehicle's yaw rate ω(k) is converted to radians and then compared with the vehicle speed v. h (k) multiplied together yields the lateral acceleration a. Lat (k),

[0098] Using the lateral acceleration and vehicle speed as two-dimensional information inputs, the desired acceleration a1(k) is obtained by looking up a table, where a1(k) = a(v). h (k),a Lat (k)) (2);

[0099] Using this two-dimensional information as input, the acceleration rate of change limit is calculated by a two-dimensional lookup table to obtain the acceleration rate of change limit value j1(k), j1(k) = j(v h (k),a Lat (k)) (3);

[0100] ω(k) represents the yaw rate of the vehicle, v h (k) represents the vehicle speed, a Lat (k) represents the lateral acceleration, a1(k) represents the desired acceleration in the curve, and j1(k) represents the first acceleration rate limit.

[0101] For example, a(v h (k),a Lat (k)) and j(v) h (k),a Lat The two-dimensional tables of (k) are shown in Table 1 and Table 2 below;

[0102] Table 1

[0103]

[0104]

[0105] Table 2

[0106]

[0107] Optionally, the vehicle motion state estimation curvature radius speed limiting unit obtains the curve curvature radius based on the vehicle's lateral acceleration and speedometer readings, and then queries the desired acceleration table based on the curve curvature radius and lateral acceleration to obtain the desired curve acceleration, including:

[0108] The vehicle lateral acceleration a obtained by the lateral acceleration limiting unit Lat (k) and vehicle speed v h (k) Further calculation yields the radius of curvature of the curve.

[0109] Using the radius and lateral acceleration as two-dimensional information inputs, the desired acceleration a2(k) under this condition is calculated by looking up a table.

[0110] v h (k) represents the vehicle speed, a Lat (k) represents the vehicle's lateral acceleration. Let a2(k) represent the radius of curvature of the curve, and let a2(k) represent the desired acceleration of the curve.

[0111] For example, The two-dimensional table is shown in Table 3 below;

[0112] Table 3

[0113]

[0114] Optionally, the steering wheel angle speed limiting unit queries the desired acceleration table based on the vehicle's steering wheel angle and speed, and then queries the acceleration change rate limit table using linear interpolation based on the vehicle's steering wheel angle and speed to obtain the desired cornering acceleration and the second acceleration change rate limit, including:

[0115] The vehicle steering wheel angle θ(k) is converted to radians and the vehicle speed is used as two-dimensional information input for looking up the desired acceleration in a table.

[0116] Convert the vehicle steering wheel angle θ(k) to radians and use the vehicle speed as input for linear interpolation with acceleration rate of change constraint, then look up the table.

[0117] The desired acceleration and the limit values ​​of the rate of change of acceleration under these conditions are obtained. (8);

[0118] k represents the current calculation time, and θ(k) represents the steering wheel angle in units of angle.

[0119] v represents the steering wheel angle in radians.h (k) represents the vehicle speed, a3(k) represents the desired acceleration in the curve, and j2(k) represents the second acceleration change rate limit.

[0120] For example, and The two-dimensional tables are shown in Table 4 and Table 5 below;

[0121] Table 4

[0122]

[0123] Table 5

[0124]

[0125]

[0126] Optionally, the perception data estimation curvature speed limiting unit estimates the curvature of the vehicle's current and forward-aimed positions based on the lane line equations output from the visual perception data. It then calculates the curve radius at both positions and constructs a desired speed table using the smallest curve radius. Different curvature radii correspond to different desired vehicle speeds. Furthermore, it uses PID control to divide the error range based on the speed error input and constructs an upper and lower limit table for desired acceleration to obtain the desired curve acceleration, including:

[0127] When there are lane lines or curbs on the road where the vehicle is traveling, the lane line equation output by the visual perception data is shown in equation (9), and the calculation expressions of its first derivative and second derivative are shown in equation (10) and equation (11).

[0128] y(k)=c0(k)+c1(k)·x(k)+c2(k)·x(k) 2 +c3(k)·x(k) 3 (9);

[0129] y′(k)=c1(k)+2c2(k)·x(k)+3c3(k)·x(k) 2 (10);

[0130] y″(k)=2c2(k)+6c3(k)·x(k) (11);

[0131] Design a one-dimensional lookup table using vehicle speed as input to obtain the preview distance x at different vehicle speeds. pre (k), x pre (k)=x(v h (k))(12);

[0132] The radius of curvature R of the vehicle's current position and the target position is obtained by equations (13) and (14) and the corresponding filtering process.cur (k) and R pre (k);

[0133]

[0134]

[0135] By comparing the two equations (15), we can obtain the minimum radius R′(k), R′(k)=min{R cur (k),R pre (k)} (15);

[0136] The minimum radius is used as the input to design the one-dimensional desired speed lookup table, as shown in equation (16). Different radii of curvature correspond to different desired vehicle speeds, v dsr (k)=v(R′(k)) (16);

[0137] To improve the smoothness of pre-deceleration in corners, a lookup table of upper and lower limits for the desired acceleration is designed with a single input and single output, as shown in Table a. lo (Δv(k)) and a up (Δv(k)), the input is the speed error input Δv(k), which represents the difference between the expected speed on the curve and the current speed, as shown in equation (17);

[0138] Δv(k)=v dsr (k)-v h (k) (17);

[0139] To improve the smoothness of pre-deceleration in corners, a lookup table of upper and lower limits for the desired acceleration is designed with a single input and single output, as shown in Table a. lo (Δv(k)) and a up The input terminal (Δv(k)) is the speed error input Δv(k), which represents the difference between the desired speed on the curve and the current vehicle speed, as shown in equation (17). Using the PID control concept, the error segment is reasonably divided, and a two-dimensional upper and lower limit table of desired acceleration is designed offline. Thus, the desired acceleration on the curve under this condition can be obtained, and its calculation expression is shown in equation (18).

[0140] a4(k)=min{max{a4(k-1),a lo (Δv(k))},a up (Δv(k))} (18);

[0141] k represents the current calculation time, y represents the lateral position with the vehicle camera position as the origin, x represents the vehicle's position in the positive direction of travel, the x and y axes follow the left-hand rule, c0, c1, c2, and c3 represent the lane line equation coefficients, x pre (k) represents the aiming distance at different vehicle speeds, v h(k) represents the vehicle speed, R cur (k) represents the radius of curvature of the vehicle's current position, R pre (k) represents the radius of curvature of the vehicle's pre-aiming position, R′(k) represents the estimated minimum radius, v dsr (k) represents the desired vehicle speed corresponding to the radius of curvature of the curve, Δv(k) represents the speed error, and a4(k) represents the desired acceleration of the curve.

[0142] For example, x(v h (k)), v(R′(k)), a lo (Δv(k)) and a up The one-dimensional tables of (Δv(k)) are shown in Tables 6, 7, 8 and 9 below;

[0143] Table 6

[0144] <![CDATA[x(v h (k))]]> 20 40 50 60 80

[0145] Table 7

[0146] v(R′(k)) 11.11 13.89 16.67 19.44 22.22 27.78 34.72 37.50

[0147] Table 8

[0148]

[0149]

[0150] Table 9

[0151] <![CDATA[a up (Δv(k))]]> -1.5 -1.2 -1.0 -0.5 0.0 0.4 1.0 1.65

[0152] Optionally, the acceleration limiting output unit takes the minimum value among the desired accelerations obtained by the above units to obtain the desired cornering acceleration to be limited. It takes the smaller value of the first and second acceleration rate of change limits to obtain the minimum acceleration rate of change limit, performs limiting processing on the desired cornering acceleration to be limited, and calculates the final desired cornering acceleration of the vehicle, including:

[0153] The expected acceleration of the curve to be limited is calculated.

[0154] The minimum acceleration rate limit is obtained by taking the smaller value of the first and second acceleration rate limit, j(k)=min{j1(k),j2(k)} (20);

[0155] The final expected acceleration of the vehicle in the curve is obtained by limiting the amplitude calculation.

[0156]

[0157] T represents the calculation step size. Let j(k) represent the minimum expected acceleration in a curve to be limited, j(k) represent the minimum rate of change of acceleration limit, and a(k) represent the final expected acceleration of the vehicle in a curve.

[0158] Second embodiment;

[0159] This invention provides a method for calculating speed limits on curves, which is used in intelligent driving assistance systems, and includes the following steps;

[0160] S1. Based on the lateral acceleration and vehicle speed, query the expected acceleration table and the acceleration rate of change limit table to obtain the expected acceleration for the curve and the first acceleration rate of change limit;

[0161] S2, obtain the curve radius of curvature based on the vehicle's lateral acceleration and speedometer, and obtain the desired curve acceleration by looking up the desired acceleration table based on the curve radius of curvature and lateral acceleration;

[0162] S3. Based on the vehicle steering wheel angle and vehicle speed, look up the expected acceleration table, and based on the vehicle steering wheel angle and vehicle speed, look up the acceleration change rate limit linear interpolation table to obtain the expected acceleration for the curve and the second acceleration change rate limit.

[0163] S4 estimates the curvature of the vehicle's current and forward positions based on the lane line equations output from the visual perception data, calculates the curve radius of the vehicle's current and forward positions, and constructs a desired speed table by taking the smallest radius among the curve radii. Different curvature radii correspond to different desired vehicle speeds. Based on the speed error input, it uses PID control to divide the error segments and constructs an upper and lower limit table of desired acceleration to obtain the desired acceleration for curves.

[0164] S5. Take the minimum value among the expected accelerations obtained in the above units to obtain the expected acceleration of the curve to be limited. Take the smaller value of the first acceleration change rate limit and the second acceleration change rate limit to obtain the minimum acceleration change rate limit. Perform the curve limiting process on the expected acceleration of the curve to be limited, and calculate the final expected acceleration of the vehicle in the curve.

[0165] The execution order of steps S1 to S4 is not limited.

[0166] Optionally, step S1 includes: taking the absolute value of the vehicle's yaw rate ω(k) and converting it to radians and vehicle speed v. h (k) multiplied together yields the lateral acceleration a. Lat (k),

[0167] Using the lateral acceleration and vehicle speed as two-dimensional information inputs, the desired acceleration a1(k) is obtained by looking up a table, where a1(k) = a(v).h (k),a Lat (k)) (2);

[0168] Using this two-dimensional information as input, the acceleration rate of change limit is calculated by a two-dimensional lookup table to obtain the acceleration rate of change limit value j1(k), j1(k) = j(v h (k),a Lat (k)) (3);

[0169] ω(k) represents the yaw rate of the vehicle, v h (k) represents the vehicle speed, a Lat (k) represents the lateral acceleration, a1(k) represents the desired acceleration in the curve, and j1(k) represents the first acceleration rate limit.

[0170] For example, a(v h (k),a Lat (k)) and j(v) h (k),a Lat The two-dimensional tables of (k) are shown in Table 1 and Table 2 below;

[0171] Table 1

[0172]

[0173] Table 2

[0174]

[0175] Optionally, step S2 includes:

[0176] The vehicle lateral acceleration a obtained by the lateral acceleration limiting unit Lat (k) and vehicle speed v h (k) Further calculation yields the radius of curvature of the curve.

[0177] Using the radius and lateral acceleration as two-dimensional information inputs, the desired acceleration a2(k) under this condition is calculated by looking up a table.

[0178] v h (k) represents the vehicle speed, a Lat (k) represents the vehicle's lateral acceleration. Let a2(k) represent the radius of curvature of the curve, and let a2(k) represent the desired acceleration of the curve.

[0179] For example, The two-dimensional table is shown in Table 3 below;

[0180] Table 3

[0181]

[0182] Optionally, step S3 includes:

[0183] The vehicle steering wheel angle θ(k) is converted to radians and the vehicle speed is used as two-dimensional information input for looking up the desired acceleration in a table.

[0184] Convert the vehicle steering wheel angle θ(k) to radians and use the vehicle speed as input for linear interpolation with acceleration rate of change constraint, then look up the table.

[0185] The desired acceleration and the limit values ​​of the rate of change of acceleration under these conditions are obtained.

[0186] k represents the current calculation time, and θ(k) represents the steering wheel angle in units of angle. v represents the steering wheel angle in radians. h (k) represents the vehicle speed, a3(k) represents the desired acceleration in the curve, and j2(k) represents the second acceleration change rate limit.

[0187] For example, and The two-dimensional tables are shown in Table 4 and Table 5 below;

[0188] Table 4

[0189]

[0190] Table 5

[0191]

[0192] Optionally, step S4 includes:

[0193] When there are lane lines or curbs on the road where the vehicle is traveling, the lane line equation output by the visual perception data is shown in equation (9), and the calculation expressions of its first derivative and second derivative are shown in equation (10) and equation (11).

[0194] y(k)=c0(k)+c1(k)·x(k)+c2(k)·x(k) 2 +c3(k)·x(k) 3 (9);

[0195] y′(k)=c1(k)+2c2(k)·x(k)+3c3(k)·x(k) 2 (10);

[0196] y″(k)=2c2(k)+6c3(k)·x(k) (11);

[0197] Design a one-dimensional lookup table using vehicle speed as input to obtain the preview distance x at different vehicle speeds. pre (k), x pre (k)=x(v h (k))(12);

[0198] The radius of curvature R of the vehicle's current position and the target position is obtained by equations (13) and (14) and the corresponding filtering process. cur (k) and R pre (k);

[0199]

[0200]

[0201] By comparing the two equations (15), we can obtain the minimum radius R′(k), R′(k)=min{R cur (k),R pre (k)} (15);

[0202] The minimum radius is used as the input to design the one-dimensional desired speed lookup table, as shown in equation (16). Different radii of curvature correspond to different desired vehicle speeds, v dsr (k)=v(R′(k)) (16);

[0203] To improve the smoothness of pre-deceleration in corners, a lookup table of upper and lower limits for the desired acceleration is designed with a single input and single output, as shown in Table a. lo (Δv(k)) and a up (Δv(k)), the input is the speed error input Δv(k), which represents the difference between the expected speed on the curve and the current speed, as shown in equation (17);

[0204] Δv(k)=v dsr (k)-v h (k) (17);

[0205] To improve the smoothness of pre-deceleration in corners, a lookup table of upper and lower limits for the desired acceleration is designed with a single input and single output, as shown in Table a. lo (Δv(k)) and a up The input terminal (Δv(k)) is the speed error input Δv(k), which represents the difference between the desired speed on the curve and the current vehicle speed, as shown in equation (17). Using the PID control concept, the error segment is reasonably divided, and a two-dimensional upper and lower limit table of desired acceleration is designed offline. Thus, the desired acceleration on the curve under this condition can be obtained, and its calculation expression is shown in equation (18).

[0206] a4(k)=min{max{a4(k-1),a lo (Δv(k))},a up (Δv(k))} (18);

[0207] k represents the current calculation time, y represents the lateral position with the vehicle camera position as the origin, x represents the vehicle's position in the positive direction of travel, the x and y axes follow the left-hand rule, c0, c1, c2, and c3 represent the lane line equation coefficients, x pre (k) represents the aiming distance at different vehicle speeds, v h (k) represents the vehicle speed, R cur (k) represents the radius of curvature of the vehicle's current position, R pre (k) represents the radius of curvature of the vehicle's pre-aiming position, R′(k) represents the estimated minimum radius, v dsr (k) represents the desired vehicle speed corresponding to the radius of curvature of the curve, Δv(k) represents the speed error, and a4(k) represents the desired acceleration of the curve.

[0208] For example, x(v h (k)), v(R′(k)), a lo (Δv(k)) and a up The one-dimensional tables of (Δv(k)) are shown in Tables 6, 7, 8 and 9 below;

[0209] Table 6

[0210] <![CDATA[x(v h (k))]]> 20 40 50 60 80

[0211] Table 7

[0212] v(R′(k)) 11.11 13.89 16.67 19.44 22.22 27.78 34.72 37.50

[0213] Table 8

[0214] <![CDATA[a lo (Δv(k))]]> -1.8 -1.5 -1.2 -0.69 0.0 0.30 0.80 1.60

[0215] Table 9

[0216] <![CDATA[a up (Δv(k))]]> -1.5 -1.2 -1.0 -0.5 0.0 0.4 1.0 1.65

[0217] Optionally, step S5 includes:

[0218] The expected acceleration of the curve to be limited is calculated.

[0219] The minimum acceleration rate limit is obtained by taking the smaller value of the first and second acceleration rate limit, j(k)=min{j1(k),j2(k)} (20);

[0220] The final expected acceleration of the vehicle in the curve is obtained by limiting the amplitude calculation.

[0221]

[0222] T represents the calculation step size. Let j(k) represent the minimum expected acceleration in a curve to be limited, j(k) represent the minimum rate of change of acceleration limit, and a(k) represent the final expected acceleration of the vehicle in a curve.

[0223] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It will also be understood that, unless expressly defined herein, terms such as those defined in a general dictionary shall be interpreted as having the meaning consistent with their meaning in the relevant field context, and not as having an idealized or overly formal meaning.

[0224] The present invention has been described in detail above through specific embodiments and examples, but these are not intended to limit the invention. Many modifications and improvements can be made by those skilled in the art without departing from the principles of the invention, and these should also be considered within the scope of protection of the present invention.

Claims

1. A curve speed limit calculation module for use in an intelligent driving assistance system, characterized in that, include: The lateral acceleration limiting unit obtains the desired acceleration for the curve and the first acceleration rate of change limit by querying the desired acceleration table and the acceleration rate of change limit table based on the lateral acceleration and vehicle speed. The vehicle motion state estimation curvature radius speed limiting unit obtains the curvature radius of the curve based on the vehicle's lateral acceleration and speedometer, and obtains the expected acceleration of the curve by looking up the expected acceleration table based on the curvature radius of the curve and the lateral acceleration. The steering wheel angle speed limiting unit looks up the desired acceleration table based on the vehicle's steering wheel angle and vehicle speed, and looks up the acceleration change rate limit table by linear interpolation based on the vehicle's steering wheel angle and vehicle speed to obtain the desired acceleration for cornering and the second acceleration change rate limit. The perception data estimation curvature speed limit unit estimates the curvature of the vehicle's current position and the target position based on the lane line equation output by the visual perception data, calculates the curve radius of the vehicle's current position and the target position, and constructs the expected speed table by taking the smallest radius among the curve radii. Different curvature radii correspond to different expected vehicle speeds. It uses PID control to divide the error range based on the speed error input and constructs an upper and lower limit table of the desired acceleration to obtain the desired acceleration for cornering. The acceleration limiting output unit takes the minimum value among the desired accelerations obtained by the above units to obtain the desired acceleration for the curve to be limited. It takes the smaller value of the first acceleration change rate limit and the second acceleration change rate limit to obtain the minimum acceleration change rate limit. It performs limiting processing on the desired acceleration for the curve to be limited and calculates the final desired acceleration for the vehicle in the curve.

2. The curve speed limit calculation module as described in claim 1, characterized in that... : （1）； （2）； （3）； Indicates the yaw rate of the vehicle. Indicates vehicle speed. Indicates lateral acceleration. This represents the expected acceleration during a curve. This represents the first acceleration rate of change limit.

3. The curve speed limit calculation module as described in claim 2, characterized in that... : （4）； （5）； Indicates vehicle speed. Indicates the lateral acceleration of the vehicle. Indicates the radius of curvature of the curve. This represents the expected acceleration during a curve.

4. The curve speed limit calculation module as described in claim 3, characterized in that... : （6）； （7）； （8）； Indicates the current calculation time. This represents the steering wheel angle in units of degrees. This represents the steering wheel angle in radians. Indicates vehicle speed. This represents the expected acceleration during a curve; This indicates the limit for the rate of change of the second acceleration.

5. The curve speed limit calculation module as described in claim 4, characterized in that... : （9）； （10）； （11）； （12）； （13）； （14）； （15）； （16）； （17）； （18）； Equation (9) represents the lane line equation output by visual perception data, Equation (10) represents the expression for calculating the first derivative of Equation (9), and Equation (11) represents the expression for calculating the second derivative of Equation (9). Indicates the current calculation time. This indicates the lateral position with the vehicle's camera location as the origin. Indicates the vehicle's position in the positive direction of travel. The axis follows the left-hand rule. , , , Represents the coefficients of the lane line equation. Indicates the aiming distance at different vehicle speeds. Indicates vehicle speed. Indicates the radius of curvature of the vehicle's current position. Indicates the radius of curvature of the vehicle's pre-aiming position. This represents the estimated minimum radius. This represents the expected vehicle speed corresponding to the radius of curvature of the curve. Indicates speed error, This represents the expected acceleration during a curve.

6. The curve speed limit calculation module as described in claim 5, characterized in that... : （19）； （20）； （21）； Indicates the calculation step size. This represents the minimum expected acceleration for the curve to be limited. This represents the minimum rate of change of acceleration limit. This represents the expected acceleration of the vehicle during the final curve.

7. A method for calculating speed limits on curves, used in an intelligent driving assistance system, characterized in that, Includes the following steps; S1. Based on the lateral acceleration and vehicle speed, query the expected acceleration table and the acceleration rate of change limit table to obtain the expected acceleration for the curve and the first acceleration rate of change limit; S2, obtain the curve radius of curvature based on the vehicle's lateral acceleration and speedometer, and obtain the desired curve acceleration by looking up the desired acceleration table based on the curve radius of curvature and lateral acceleration; S3. Based on the vehicle steering wheel angle and vehicle speed, look up the expected acceleration table, and based on the vehicle steering wheel angle and vehicle speed, look up the acceleration change rate limit linear interpolation table to obtain the expected acceleration for the curve and the second acceleration change rate limit. S4. Based on the lane line equation output by the visual perception data, the curvature of the vehicle's current position and the target position is estimated, the curve radius of the vehicle's current position and the target position is calculated, and the minimum radius among the curve radii is used to construct the expected speed table. Different curvature radii correspond to different expected vehicle speeds. It uses PID control to divide the error range based on the speed error input and constructs an upper and lower limit table of the desired acceleration to obtain the desired acceleration for cornering. S5, take the minimum value of the desired acceleration to obtain the desired acceleration of the curve to be limited. Take the smaller value of the first acceleration change rate limit and the second acceleration change rate limit to obtain the minimum acceleration change rate limit. Perform the curve limiting process on the desired acceleration of the curve to be limited, and calculate the final desired acceleration of the vehicle in the curve. In S1 to S4, the execution order of the steps is not limited.

8. The method for calculating speed limits on curves as described in claim 7, characterized in that, When implementing step S1, the following is included: (1); （2）； （3）； Indicates the yaw rate of the vehicle. Indicates vehicle speed. Indicates lateral acceleration. This represents the expected acceleration during a curve. This represents the first acceleration rate of change limit.

9. The method for calculating speed limits on curves as described in claim 8, characterized in that, When implementing step S2, the following is included: （4）； （5）； Indicates vehicle speed. Indicates the lateral acceleration of the vehicle. Indicates the radius of curvature of the curve. This represents the expected acceleration during a curve.

10. The method for calculating speed limits on curves as described in claim 9, characterized in that, When implementing step S3, the following is included: （6）； （7）； （8）； Indicates the current calculation time. This represents the steering wheel angle in units of degrees. This represents the steering wheel angle in radians. Indicates vehicle speed. This represents the expected acceleration during a curve; This indicates the limit for the rate of change of the second acceleration.

11. The method for calculating speed limits on curves as described in claim 10, characterized in that, When implementing step S4, the following is included: （9）； （10）； （11）； （12）； （13）； （14）； （15）； （16）； （17）； （18）； Equation (9) represents the lane line equation output by visual perception data, Equation (10) represents the expression for calculating the first derivative of Equation (9), and Equation (11) represents the expression for calculating the second derivative of Equation (9). Indicates the current calculation time. This indicates the lateral position with the vehicle's camera location as the origin. Indicates the vehicle's position in the positive direction of travel. The axis follows the left-hand rule. , , , Represents the coefficients of the lane line equation. Indicates the aiming distance at different vehicle speeds. Indicates vehicle speed. Indicates the radius of curvature of the vehicle's current position. Indicates the radius of curvature of the vehicle's pre-aiming position. This represents the estimated minimum radius. This represents the expected vehicle speed corresponding to the radius of curvature of the curve. Indicates speed error, This represents the expected acceleration during a curve.

12. The method for calculating speed limits on curves as described in claim 11, characterized in that, When implementing step S5, the following is included: (19); （20）； （21）； Indicates the calculation step size. This represents the minimum expected acceleration for the curve to be limited. This represents the minimum rate of change of acceleration limit. This represents the expected acceleration of the vehicle during the final curve.

Images