Preview decision-making method for speed following of self-driving automobile

Abstract

The invention discloses an automatic driving automobile speed following preview decision-making method, which comprises the following steps of: selecting a preview target and determining a preview distance; calculating a preview tracking error according to the preview vehicle speed and the expected vehicle speed by taking the travelled distance on the target path as a longitudinal motion distance based on the preview target and the preview distance, and controlling the preview tracking error within a preset following precision error threshold range through a multi-section preview method based on a motion primitive to obtain a preview result; determining an expected longitudinal acceleration according to a preview result, following the longitudinal acceleration of the automobile through an expected longitudinal acceleration following method, and performing load compensation on the longitudinal acceleration of the automobile; and selecting an actuating phase of the automobile chassis mechanism according to the compensated following acceleration, and deciding an operation command quantity. According to the invention, a vehicle speed change driving scheme planned based on space requirements can be followed.

Description

Technical Field

[0001] The present invention relates to the technical field of autonomous driving vehicles, and in particular to a preview decision method for speed following of an autonomous driving vehicle. Background Art

[0002] With the development of science and technology, self-driving cars have become one of the fastest-growing and most concerned technology growth points in the current automotive industry. Among them, speed following is one of the important functions required by self-driving cars. Self-driving cars have been commercially applied in urban scenarios. In urban scenarios, self-driving cars need to handle various traffic regulations well, such as speed limit signs, stop signs, traffic lights, etc. The speed requirements of this type of traffic regulations are all based on spatial positions. Self-driving cars in urban scenarios need to follow the speed requirements in space. The speed following achieved by current self-driving technology is mostly a time-following method for completing the driving plan. The implementation effect of the above-mentioned spatial speed requirements is not ideal, mainly manifested in large speed following lag, large speed fluctuations, and large speed errors at designated spatial positions. Summary of the invention

[0003] The present invention proposes a preview decision method for speed following of an autonomous driving vehicle, so as to solve the deficiency of the existing autonomous driving vehicle in following a speed target set based on space.

[0004] To achieve the above object, the present invention provides a preview decision method for speed following of an automatic driving vehicle, comprising:

[0005] Selecting a preview target and determining a preview distance, wherein the preview target is any section in the list of speeds to be followed provided by the upstream vehicle speed planning function module of the system;

[0006] Based on the preview target and the preview distance, the mileage on the target path is used as the longitudinal movement distance, the preview tracking error is calculated according to the preview vehicle speed and the expected vehicle speed, and the preview tracking error is controlled within a preset following accuracy error threshold range through a multi-segment preview method based on motion primitives to obtain a preview result;

[0007] Determining an expected longitudinal acceleration according to the preview result, following the longitudinal acceleration of the vehicle by an expected longitudinal acceleration following method, and performing load compensation on the longitudinal acceleration of the vehicle;

[0008] The actuation phase of the vehicle chassis mechanism is selected according to the compensated following acceleration to determine the control command amount.

[0009] Preferably, selecting the preview target and determining the preview distance comprises:

[0010] The Frenet coordinate system is established with the expected following path as the s-axis. The geodetic coordinates of the main vehicle at the current moment are (X e , Y e ), the vehicle speed is V, and the preview distance is T P ;

[0011] According to the conversion relationship between the current earth coordinate system and the frenet coordinate system, the earth coordinates of the main vehicle are converted into frenet coordinates (s e , d e ), the preview target is obtained as [s e ,s Tp ], where s Tp =s e +d; d is the preview distance, d = max (VT P , Δs min ), Δs min The shortest sight distance.

[0012] Preferably, calculating the preview tracking error comprises:

[0013] err i =|V i -V preview，i |;

[0014] In the formula, err i is the preview tracking error, V i is the expected speed corresponding to the mileage, V preview，i To preview the vehicle speed;

[0015]

[0016] Where V start is the starting speed, a x is the preview acceleration, s i is the mileage of the preview point, s1 is the starting mileage, V N is the speed of the vehicle at the last speed point in the speed list, and Δs is the difference in mileage between the start and end points.

[0017] Preferably, controlling the preview tracking error within a preset error range by a multi-segment preview method based on motion primitives comprises:

[0018] Update the list of speeds to be followed according to the preview speed points;

[0019] Get the preset shortest running distance information, and determine whether the mileage covered by the list is greater than the shortest running distance. If so, proceed to the next step, otherwise return;

[0020] Set the following accuracy error threshold, perform motion primitive, i.e., expected acceleration preview, and determine whether the following error is less than the threshold under the description of the motion primitive. If so, continue to insert the subsequent speed points. Otherwise, insert the preview result of the previous step into the acceleration / deceleration-mileage list, and delete the remaining speed points in the following speed point list except the last two speed points.

[0021] Repeat the above steps until the list of speeds to be followed is empty, and the list of acceleration and deceleration intensity-mileage [(a x1 ,s1)),…),(a xn ,s n ))] is the decision result, where a xi is the preview acceleration of the i-th segment, s i is the starting mileage of the i-th segment, i=1,2,…,n;

[0022] Finally, the current mileage signal of the controlled vehicle is obtained, and the expected longitudinal acceleration is determined based on the acceleration and deceleration intensity-mileage list to be executed and the current mileage of the autonomous driving vehicle.

[0023] Preferably, determining the expected longitudinal acceleration comprises:

[0024]

[0025] In the formula, is the expected longitudinal acceleration, a xi is the preview acceleration of the i-th segment, s i is the mileage of the preview point, s e It is the current mileage signal of the controlled vehicle.

[0026] Preferably, following the longitudinal acceleration of the vehicle by the expected longitudinal acceleration following method comprises:

[0027] A closed-loop acceleration tracking module with direct feedforward is used. When there is an error in acceleration tracking, the error is eliminated through closed-loop tracking. When the feedback sensor fails, the closed-loop module is disconnected to degenerate the acceleration tracking method into an open-loop compensation correction to ensure the normal driving of the car.

[0028] Among them, the anti-integral saturation PID is used as the closed-loop tracking method, specifically:

[0029]

[0030] Where, e is the acceleration error, K p , K I , K D They are proportional coefficient, integral coefficient, differential coefficient, K b is the inverse calculation coefficient, Δu is the difference between the output control amount and the directly calculated control amount, Δax It is the interpolation between the ideal acceleration and the current actual acceleration.

[0031] Preferably, performing load compensation on the longitudinal acceleration of the vehicle includes:

[0032] F c =F slope +F wind +F friction +F access_load ;

[0033]

[0034] In the formula, F c F is the total resistance that needs to be overcome for the longitudinal movement of the vehicle. slope is the slope resistance, F wind is the air resistance, F friction is the rolling resistance, F access_load is the equivalent resistance generated by the electrical load, f c is the load specific force, and M is the vehicle mass.

[0035] Preferably, selecting the actuation phase of the vehicle chassis mechanism according to the compensated following acceleration includes:

[0036]

[0037] Where phase is the working phase of the vehicle longitudinal motion chassis system, f * For the ratio after compensation, is the minimum specific force of the driving phase, is the maximum specific force of the driving phase, is the minimum specific force of the braking phase, is the maximum specific force of the braking phase.

[0038] Preferably, the final drive specific force is determined or brake force According to the driving force and the vehicle speed steady value V determine the accelerator pedal opening α T , according to the braking force and vehicle speed steady value V to determine the brake master cylinder pressure P B .

[0039] Preferably, the final drive specific force is determined or brake force Specifically:

[0040]

[0041] Determine α T Specifically:

[0042]

[0043] Determine P B Specifically:

[0044]

[0045] Where VSD -1 is the inverse model of vehicle system dynamics, α T is the accelerator pedal opening, P B is the brake master cylinder pressure.

[0046] Compared with the prior art, the present invention has the following advantages and technical effects:

[0047] The present invention proposes a preview decision method for speed following of an automatic driving vehicle, which can follow a speed change driving plan planned based on space requirements. Through the spatial preview method, the expected vehicle speed is decomposed into multiple segments in space with motion primitives, and the segmentation points are determined according to the preview error to ensure that the preview following error is within the allowable error range, thereby reducing the decrease in driving stability and comfort caused by frequent driving operations. The expected longitudinal acceleration is determined according to the preview result, and an expected longitudinal acceleration following method is established to follow the longitudinal acceleration of the vehicle to ensure the rapid realization of the expected speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0049] Figure 1 A schematic diagram of preview target selection according to an embodiment of the present invention;

[0050] Figure 2 A schematic diagram of target speed and preview speed in single-stage preview following according to an embodiment of the present invention;

[0051] Figure 3 A schematic diagram of speed preview error in single-stage preview following according to an embodiment of the present invention;

[0052] Figure 4 A flow chart of a multi-segment preview method based on motion primitives according to an embodiment of the present invention;

[0053] Figure 5 This is an overall block diagram of the longitudinal acceleration following according to an embodiment of the present invention. DETAILED DESCRIPTION

[0054] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0055] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0056] This embodiment proposes a preview decision method for speed following of an autonomous driving vehicle, including:

[0057] Select a preview target and determine a preview distance, wherein the preview target is any section in the list of speeds to be followed provided by the upstream vehicle speed planning function module of the system;

[0058] Based on the preview target and the preview distance, the mileage on the target path is used as the longitudinal movement distance, the preview tracking error is calculated according to the preview vehicle speed and the expected vehicle speed, and the preview tracking error is controlled within a preset following accuracy error threshold range through a multi-segment preview method based on motion primitives to obtain a preview result;

[0059] Determine the expected longitudinal acceleration according to the preview result, follow the longitudinal acceleration of the vehicle by the expected longitudinal acceleration following method, and perform load compensation on the longitudinal acceleration of the vehicle;

[0060] The actuation phase of the vehicle chassis mechanism is selected according to the compensated following acceleration to determine the control command amount.

[0061] Specifically, this embodiment can follow the speed change driving plan planned based on space requirements. Through the spatial preview method, the expected vehicle speed is decomposed into multiple segments in space with motion primitives, and the segmentation points are determined according to the preview error to ensure that the preview following error is within the allowable error range, thereby reducing the decline in driving stability and comfort caused by frequent driving operations. The expected longitudinal acceleration is determined based on the preview result, and the expected longitudinal acceleration following method is established to follow the longitudinal acceleration of the vehicle to ensure the rapid realization of the expected speed.

[0062] Furthermore, selecting a preview target and determining a preview distance include:

[0063] The Frenet coordinate system is established with the expected following path as the s-axis. The geodetic coordinates of the main vehicle at the current moment are (X e ,Y e ), the vehicle speed is V, and the preview distance is T P ;

[0064] According to the conversion relationship between the current earth coordinate system and the frenet coordinate system, the earth coordinates of the main vehicle are converted into frenet coordinates (s e , d e ), the preview target is obtained as [se ,s Tp ], where s Tp =s e +d; d is the preview distance, d = max (VT P ,Δs min ), Δs min The shortest sight distance.

[0065] Specifically, the speeds that the driver wants to follow vary. In order to uniformly express the target speed, this embodiment describes the desired speed in the form of a discrete point sequence. When the target speed to be followed is given in the form of a spatial sequence, (V i ),s i ) to describe the expected vehicle speed, s i is the mileage on the desired path, V i is the expected speed corresponding to the mileage.

[0066] When a person is driving, the expected target will move forward along the expected driving path. Therefore, it is assumed that the preview target is always selected along the direction of the follow-up path, and a preview target selection method is proposed based on this. Figure 1 As shown in Figure 1, the Frenet coordinate system is established with the expected following path as the s-axis. The geodetic coordinates of the main vehicle at the current moment are (X e ,Y e ), the vehicle speed is V, the preview distance is T P , d=max(VT P ,Δs min ) is the preview distance, where Δs min is the shortest sight distance. First, the geodetic coordinates of the main vehicle are converted into frenet coordinates (s e , d e ). The preview target is [s e ,s Tp ] The following target between mileages, where s Tp =s e +d. That is, the mileage distance in the Frenet coordinate system is used as the preview distance. Obviously, when the mileage difference remains unchanged and the curvature of the expected following path is greater, the straight-line distance from the driver to the preview point is shorter, which is consistent with the characteristics that when the driver is driving a vehicle, the greater the road curvature, the smaller the field of view, and the shorter the forward distance.

[0067] Furthermore, the preview tracking error is calculated, including:

[0068] For speed following, constant longitudinal acceleration motion is used as the longitudinal motion primitive. When the speed following target is in the speed-mileage sequence [(V1, s1)),…), (V N ,s N))], since the error between the lateral motion and the target path is not large, the mileage on the target path is used as the longitudinal motion distance. The longitudinal acceleration is calculated as shown in formula (1). The preview speed formula is shown in formula (2).

[0069]

[0070] Where V start is the starting speed, a x is the preview acceleration, V N is the speed of the vehicle at the last speed point in the speed list, and Δs is the difference in mileage between the start and end points.

[0071]

[0072] In the formula, a x is the preview acceleration, s i is the mileage of the preview point, s1 is the starting mileage, V preview，i To preview the vehicle speed.

[0073] Calculate the preview tracking error based on the preview speed and the expected target speed:

[0074] err i =|V i -V preview , i |(3);

[0075] In the formula, err i is the preview tracking error, V i is the expected speed corresponding to the mileage.

[0076] When using a single-segment motion primitive for preview, if the target to be followed does not match the motion primitive, there may be a large error between the preview speed and the target speed, such as Figure 2 and Figure 3 shown.

[0077] Furthermore, the preview tracking error is controlled within a preset error range by a multi-segment preview method based on motion primitives, including:

[0078] Update the list of speeds to be followed according to the preview speed points;

[0079] Get the preset shortest running distance information, and determine whether the mileage covered by the list is greater than the shortest running distance. If so, proceed to the next step, otherwise return;

[0080] Set the following accuracy error threshold, perform motion primitive, i.e., expected acceleration preview, and determine whether the following error is less than the threshold under the description of the motion primitive. If so, continue to insert the subsequent speed points. Otherwise, insert the preview result of the previous step into the acceleration / deceleration-mileage list, and delete the remaining speed points in the following speed point list except the last two speed points.

[0081] Repeat the above steps until the list of speeds to be followed is empty, and the list of acceleration and deceleration intensity-mileage [(a x1 ,s1)),…),(a xn ,s n ))] is the decision result; the acceleration and deceleration intensity-mileage list is obtained in sequence according to the advancement of the preview target, s i is the starting mileage of the i-th segment, i=1,2,…,n, a xi is the preview acceleration of the i-th segment.

[0082] Finally, the current mileage signal of the controlled vehicle is obtained, and the expected longitudinal acceleration is determined based on the acceleration and deceleration intensity-mileage list to be executed and the current mileage of the autonomous driving vehicle.

[0083] Specifically, in order to solve the problem of excessive error when the tracking target does not match the motion primitive, a multi-segment preview method based on motion primitives is proposed. When a preview target is given, the preview target is previewed through the motion primitive, and the segmentation points are determined by the preview error. In this process, the preview error can be positively controlled within a reasonable error range.

[0084] First, the speed-mileage point (V i ,s i ) is inserted into the following speed mileage list. Since the car needs to travel a long enough distance to perform maneuvering operations, it is determined whether the difference between the first and last mileage points of the following speed point exceeds the shortest distance required for maneuvering operations. If the distance is insufficient, continue to insert speed points until the mileage difference exceeds the shortest distance required for maneuvering operations. When the distance is sufficient, the speed is previewed. The preview method is shown in formula (1) and formula (2).

[0085] If the preview tracking error (calculated as formula (3)) is less than the allowable error, more speed points are inserted. Otherwise, the preview result of the previous step (a xi ,s i )), where a xi is the acceleration of the i-th segment, s i Insert the acceleration / deceleration intensity-mileage list for the starting mileage of the i-th segment, and delete the remaining speed points in the follow speed point list except the last two speed points. Repeat the above steps until the speed list to be followed is empty. Acceleration / deceleration intensity-mileage list [(a x1,s1),…,(a xn ,s n )] is the decision result.

[0086] According to the acceleration and deceleration intensity mileage list to be executed [(a x1 ,s1),…,(a xn ,s n )], and the current mileage of the autonomous vehicle s e Determine the expected longitudinal acceleration.

[0087]

[0088] In the formula, is the expected longitudinal acceleration, a xi is the preview acceleration of the i-th segment, s i is the mileage of the preview point, s e It is the current mileage signal of the controlled vehicle.

[0089] Furthermore, the longitudinal acceleration of the vehicle is followed by an expected longitudinal acceleration following method, including:

[0090] A closed-loop acceleration tracking module with direct feedforward is used. When there is an error in acceleration tracking, the error can be eliminated through closed-loop tracking. When the feedback sensor fails, due to the use of a closed-loop method with direct feedforward, the acceleration tracking method can be degraded to an open-loop compensation correction by disconnecting the closed-loop module to ensure that the car can drive normally.

[0091] This embodiment adopts the anti-integral saturation PID as the closed-loop tracking method, specifically:

[0092]

[0093] Where, e is the acceleration error, K p , K I , K D They are proportional coefficient, integral coefficient, differential coefficient, K b is the inverse calculation coefficient, Δu is the difference between the output control amount and the directly calculated control amount, Δa x It is the interpolation between the ideal acceleration and the current actual acceleration.

[0094] Furthermore, load compensation is performed on the longitudinal acceleration of the vehicle, including:

[0095] The car needs to overcome various resistances during driving. When the car works in different working conditions, the driving force of the car is the same when the control quantity is the same, but the acceleration is different at this time. In order to make the method applicable to all working conditions, the acceleration is load compensated, specifically:

[0096] Fc =F slope +F wind +F friction +F access_load (6);

[0097]

[0098] In the formula, F c F is the total resistance that needs to be overcome for the longitudinal movement of the vehicle. slope is the slope resistance, F wind is the air resistance, F friction is the rolling resistance, F access_load is the equivalent resistance generated by the electrical load, f c is the load specific force, and M is the vehicle mass.

[0099] Furthermore, the working phase is determined according to the compensated specific force, the current stable speed value of the autonomous driving vehicle, and the working area of ​​each working phase, so as to select and activate different assemblies of the vehicle chassis to achieve different working states such as driving, sliding, and braking of the vehicle, including:

[0100]

[0101] Where phase is the working phase of the vehicle longitudinal motion chassis system, f * For the ratio after compensation, is the minimum specific force of the driving phase, is the maximum specific force of the driving phase, is the minimum specific force of the braking phase, is the maximum specific force of the braking phase.

[0102] Further, determine the final drive specific force or brake force According to the driving force and the vehicle speed steady value V determine the accelerator pedal opening α T , according to the braking force and vehicle speed steady value V to determine the brake master cylinder pressure P B .

[0103] Determining the final drive force or brake force Specifically:

[0104]

[0105] Determine α T Specifically:

[0106]

[0107] Determine PB Specifically:

[0108]

[0109] Where VSD -1 is the inverse model of vehicle system dynamics, α T is the accelerator pedal opening, P B is the brake master cylinder pressure.

[0110] In order to more clearly express the technical solution of the present invention, the following specific embodiments are provided to introduce the solution:

[0111] S1. Preview the expected acceleration:

[0112] S2, selecting a preview point according to the expected speed plan to be followed;

[0113] First, obtain the following information: the system preset preview time T P , shortest sight distance Δs min ; The conversion relationship between the current geodetic coordinate system and the frenet coordinate system.

[0114] Secondly, the following signals are obtained: the expected speed plan to be followed is obtained from the leading module, which consists of a sequence of mileage and corresponding speed data pairs; the current vehicle status, such as position and speed, is obtained from the controlled vehicle.

[0115] Calculate preview distance d = max(VT P ,Δs min ), which means the mileage length in the Frenet coordinate system. Based on the preview distance, the corresponding preview speed (V i ,s i ).

[0116] S3, determine the ideal acceleration based on the preview point speed;

[0117] like Figure 4 As shown:

[0118] First, update the speed list to be followed according to the preview speed point.

[0119] Secondly, obtain the system preset shortest travel distance information, and determine whether the mileage covered by the list is greater than the shortest travel distance. If it is greater, continue to the next step, otherwise return.

[0120] Then, the system preset tracking accuracy error threshold information is obtained, and the motion primitive, i.e., the expected acceleration, is previewed according to formulas (1) and (2), and it is determined whether the following error is less than the threshold under the description of the primitive. If so, the subsequent speed points are inserted. Otherwise, the preview result of the previous step is inserted into the acceleration / deceleration-mileage list, and the remaining speed points in the following speed point list except the last two speed points are deleted.

[0121] Repeat the above steps until the list of speeds to be followed is empty. Acceleration / deceleration intensity-mileage list [(a x1 ,s1),…,(a xn ,s n )] is the decision result.

[0122] Finally, obtain the current mileage signal s of the controlled vehicle e , the expected longitudinal acceleration is determined based on the acceleration / deceleration intensity-mileage list to be executed and the current mileage of the autonomous vehicle.

[0123] S4. Acceleration following:

[0124] like Figure 5 The figure shows the overall framework of the longitudinal acceleration following of this embodiment, specifically S5-S7.

[0125] Among them, V is the steady speed value of the autonomous vehicle; is the expected longitudinal acceleration; a x is the actual longitudinal acceleration of the vehicle; f c is the load compensation specific force; f * is the total specific force requirement; The driving force for distribution; is the distributed braking force; α T is the accelerator pedal opening; P B is the brake master cylinder pressure; specific force is the ratio of force to vehicle mass, and has the same dimension as acceleration.

[0126] S5, determining PID following acceleration based on ideal acceleration;

[0127] The longitudinal acceleration signal of the current controlled vehicle is obtained, the error between it and the expected longitudinal acceleration is calculated, and the closed-loop acceleration tracking module with direct feedforward is executed to decide the following acceleration.

[0128] S6, determine the driving force requirement corresponding to the current load and perform following acceleration compensation;

[0129] Execute the load compensation function module, first obtain the current road slope signal i, and calculate the slope resistance:)

[0130] F slope =Mg sin i(13);

[0131] Where g is the standard acceleration due to gravity.

[0132] Then calculate the rolling resistance:

[0133] F friction =Mgk cos i(14);

[0134] Where k is the pre-calibrated rolling resistance coefficient.

[0135] After that, get the current vehicle speed V and calculate the air resistance:

[0136]

[0137] In the formula, C D is the drag coefficient, and A is the windward area.

[0138] Finally, obtain the curve of the equivalent resistance generated by the pre-calibrated electrical load as a function of vehicle speed, and determine F by looking up the table based on the vehicle speed. access_load .

[0139] The load compensation amount is calculated according to formulas (6) and (7).

[0140] S7. Select the actuation phase of the vehicle chassis mechanism according to the compensated following acceleration and decide the control command amount.

[0141] Get the pre-calibrated driving, coasting, and braking thresholds versus vehicle speed curves, and determine the thresholds based on the current vehicle speed. and

[0142] Determine the working phase to be selected at present, and determine the final driving force according to formulas (9) and (10): or brake force

[0143] According to the accelerator pedal opening α calibrated in advance according to the vehicle field test T The inverse model of the controlled vehicle powertrain system identified by the longitudinal acceleration change curve, such as formula (11), realizes the steady-state compensation of the drive and determines α T .

[0144] According to the brake master cylinder pressure P pre-calibrated according to the vehicle field test B The inverse model of the controlled vehicle powertrain system identified by the longitudinal deceleration change curve, such as formula (12), realizes the steady-state compensation of the drive and determines P B , output α T or P B ,

[0145] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A preview decision method for speed following of an autonomous driving vehicle, characterized in that: include: Selecting a preview target and determining a preview distance, wherein the preview target is any section in the list of speeds to be followed provided by the upstream vehicle speed planning function module of the system; Based on the preview target and the preview distance, the mileage on the target path is used as the longitudinal movement distance, the preview tracking error is calculated according to the preview vehicle speed and the expected vehicle speed, and the preview tracking error is controlled within a preset following accuracy error threshold range through a multi-segment preview method based on motion primitives to obtain a preview result; Determining an expected longitudinal acceleration according to the preview result, following the longitudinal acceleration of the vehicle by an expected longitudinal acceleration following method, and performing load compensation on the longitudinal acceleration of the vehicle; The actuation phase of the vehicle chassis mechanism is selected according to the compensated following acceleration to determine the control command amount.

2. The preview decision method for speed following of an automatic driving vehicle according to claim 1, characterized in that: Selecting the preview target and determining the preview distance includes: The Frenet coordinate system is established with the expected following path as the s-axis. The geodetic coordinates of the main vehicle at the current moment are (X e ,Y e ), the vehicle speed is V, and the preview distance is T P ; According to the conversion relationship between the current earth coordinate system and the frenet coordinate system, the earth coordinates of the main vehicle are converted into frenet coordinates (s e , d e ), the preview target is obtained as [s e ,s Tp ], where s Tp =s e +d; d is the preview distance, d = max (VT P ,Δs min ), Δs min The shortest sight distance.

3. The preview decision method for speed following of an automatic driving vehicle according to claim 1, characterized in that: Calculating the preview tracking error includes: err i =|V i -V preview , i |; In the formula, err i is the preview tracking error, V i is the expected speed corresponding to the mileage, V preview , i To preview the vehicle speed; Where V start is the starting speed, a x is the preview acceleration, s i is the mileage of the preview point, s1 is the starting mileage, V N is the speed of the vehicle at the last speed point in the speed list, and Δs is the difference in mileage between the start and end points.

4. The preview decision method for speed following of an automatic driving vehicle according to claim 3, characterized in that: Controlling the preview tracking error within a preset error range by a multi-segment preview method based on motion primitives includes: Update the list of speeds to be followed according to the preview speed points; Get the preset shortest running distance information, and determine whether the mileage covered by the list is greater than the shortest running distance. If so, proceed to the next step, otherwise return; Set the following accuracy error threshold, perform motion primitive, i.e., expected acceleration preview, and determine whether the following error is less than the threshold under the description of the motion primitive. If so, continue to insert the subsequent speed points. Otherwise, insert the preview result of the previous step into the acceleration / deceleration-mileage list, and delete the remaining speed points in the following speed point list except the last two speed points. Repeat the above steps until the list of speeds to be followed is empty, and the list of acceleration and deceleration intensity-mileage [(a x1 ,s1)),…),(a xn ,s n ))] is the decision result, where a xi is the preview acceleration of the i-th segment, s i is the starting mileage of the i-th segment, i=1,2,…,n; Finally, the current mileage signal of the controlled vehicle is obtained, and the expected longitudinal acceleration is determined based on the acceleration and deceleration intensity-mileage list to be executed and the current mileage of the autonomous driving vehicle.

5. The preview decision method for speed following of an automatic driving vehicle according to claim 1, characterized in that: Determining the expected longitudinal acceleration includes: In the formula, is the expected longitudinal acceleration, a xi is the preview acceleration of the i-th segment, s i is the mileage of the preview point, s e It is the current mileage signal of the controlled vehicle.

6. The preview decision method for speed following of an automatic driving vehicle according to claim 5, characterized in that: Following the vehicle longitudinal acceleration by the expected longitudinal acceleration following method includes: A closed-loop acceleration tracking module with direct feedforward is used. When there is an error in acceleration tracking, the error is eliminated through closed-loop tracking. When the feedback sensor fails, the closed-loop module is disconnected to degenerate the acceleration tracking method into an open-loop compensation correction to ensure the normal driving of the car. Among them, the anti-integral saturation PID is used as the closed-loop tracking method, specifically: Where, e is the acceleration error, K p , K I , K D They are proportional coefficient, integral coefficient, differential coefficient, K b is the inverse calculation coefficient, Δu is the difference between the output control amount and the directly calculated control amount, Δa x It is the interpolation between the ideal acceleration and the current actual acceleration.

7. The preview decision method for speed following of an automatic driving vehicle according to claim 1, characterized in that: The load compensation for the longitudinal acceleration of the vehicle includes: F c =F slope +F wind +F friction +F access_load ; In the formula, F c F is the total resistance that needs to be overcome for the longitudinal movement of the vehicle. slope is the slope resistance, F wind is the air resistance, F friction is the rolling resistance, F access_load is the equivalent resistance generated by the electrical load, f c is the load specific force, and M is the vehicle mass.

8. The preview decision method for speed following of an automatic driving vehicle according to claim 1, characterized in that: The actuation phases of the vehicle chassis mechanism are selected according to the compensated following acceleration, including: Where phase is the working phase of the vehicle longitudinal motion chassis system, f * For the ratio after compensation, is the minimum specific force of the driving phase, is the maximum specific force of the driving phase, is the minimum specific force of the braking phase, is the maximum specific force of the braking phase.

9. The preview decision method for speed following of an automatic driving vehicle according to claim 8, characterized in that: Determining the final drive force or brake force According to the driving force and the vehicle speed steady value V determine the accelerator pedal opening α T , according to the braking force and vehicle speed steady value V to determine the brake master cylinder pressure P B .

10. The preview decision method for speed following of an automatic driving vehicle according to claim 9, characterized in that: Determining the final drive force or brake force Specifically: Determine α T Specifically: Determine P B Specifically: Where VSD -1 is the inverse model of vehicle system dynamics, α T is the accelerator pedal opening, P B is the brake master cylinder pressure.

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