Vehicle longitudinal PID closed-loop control method and system during automatic parking

Abstract

The invention discloses a vehicle longitudinal PID closed-loop control method and system during automatic parking, and belongs to the field of automatic parking. The method comprises the steps that when it is judged that a vehicle has an overspeed trend, an I value is frozen; if the real-time vehicle speed is greater than the vehicle speed upper limit after freezing for a period of time, activating the D loop and resetting the I value; if the real-time vehicle speed is still greater than the vehicle speed upper limit after a period of time, continuing to activate the D loop and resetting the I value until the real-time vehicle speed is not greater than the vehicle speed upper limit, and returning to the D loop inactivation state; when it is judged that the vehicle has the low-speed trend, the D loop is activated, and the I value is reset; if the real-time vehicle speed is smaller than the vehicle speed lower limit after a period of time, continuing to activate the D loop and resetting the I value until the real-time vehicle speed is not smaller than the vehicle speed lower limit, and returning to the D loop inactivation state. According to the method, after the risk that the speed of the vehicle is out of control is judged, the vehicle speed is converged by freezing the I value, if the vehicle speed still cannot be converged, the vehicle speed is converged by activating the D loop and resetting the I value, and the automatic parking efficiency is improved by utilizing the improved PID control logic.

Description

Technical Field

[0001] The present application relates to the field of automatic parking, and in particular to a method and system for controlling a longitudinal PID closed-loop of a vehicle during automatic parking. Background Art

[0002] The automatic parking process usually involves moving the car in a small space at a low speed, which requires both efficiency (the speed cannot be too low) and extremely high longitudinal driving accuracy (if the driving distance is not enough, it cannot be parked smoothly in the target parking space, and if the driving distance is over-adjusted, there is a risk of collision). How to achieve the longitudinal control of automatic parking quickly and well is a difficult problem in the industry. At present, the longitudinal control in the automatic parking process generally adopts PID closed-loop control, and the closed-loop target can be the vehicle speed or the longitudinal driving distance.

[0003] The three loops of the PID controller include proportional (P), integral (I) and differential (D) units. These three units correspond to the current error, past accumulated error and future error respectively, and together achieve precise control of the system.

[0004] The proportional term (P) is the most basic part of the PID controller. It directly adjusts the control amount according to the size of the system deviation. The larger the deviation, the more the control amount is adjusted; the smaller the deviation, the less the control amount is adjusted. The role of the proportional term is to quickly respond to system deviations so that the system output can quickly approach the set value. However, it is often difficult to eliminate steady-state errors by relying solely on the proportional term, because when the system deviation approaches zero, the control effect of the proportional term will gradually weaken, causing the system output to be unable to stabilize at the set value.

[0005] The integral term (Integral, I) is introduced to eliminate steady-state errors. It integrates the system deviation to obtain an integral term that is proportional to the duration of the deviation and adds it to the control quantity. The role of the integral term is to gradually reduce the steady-state error so that the system output stabilizes near the set value. However, the integral term may also cause the system response to slow down or produce integral saturation. Integral saturation means that when the system deviation remains in the same direction for a long time, the integral term will continue to accumulate and increase, resulting in excessive or too small control quantity, which will cause the system output to overshoot or undershoot.

[0006] The derivative term (Derivative, D) is introduced to improve the dynamic performance of the system. It performs a differential operation on the system deviation to obtain a derivative term proportional to the rate of change of the deviation, and adds it to the control quantity. The role of the derivative term is to predict the changing trend of the system deviation and adjust the control quantity in advance, thereby speeding up the system response speed and reducing the overshoot. The derivative term plays an important role in suppressing system oscillation and improving system stability. However, the derivative term may also amplify high-frequency noise signals and have an adverse effect on the system.

[0007] Taking the speed closed loop as an example, the conventional PID control logic is: PIDControl = (Kp*SpeedError) + (Ki*IntegrationError) + (Kd*DiffError), where Kp*SpeedError is a proportional term, Kp is a proportional coefficient, Ki*IntegrationError is an integral term, Ki is an integral coefficient, Kd*DiffError is a differential term, and Kd is a differential coefficient. As the driving time increases, the value of the accumulated integral term, that is, the I value, will become larger and larger. When overshoot occurs on the vehicle (for example, the speed is too high), the I value cannot change quickly, and only when the I value drops can the speed drop to a reasonable range. If the I value cannot drop quickly, the speed will be too high for a long time, and then the driving distance will overshoot or even cause a collision risk. Therefore, the proportional coefficient and the integral coefficient are generally set to be small. However, setting a small value will also bring about the problem that the speed rises very slowly at the starting stage, and the parking efficiency is reduced accordingly.

[0008] In addition, for curbs and speed bumps on the parking path, the inability of the I value to change quickly will also make it difficult for the side beam to cross obstacles, reducing the obstacle-crossing ability of automatic parking. After the vehicle takes too long to cross the bump, the I value accumulates too much. After crossing the obstacle, the road resistance decreases, the vehicle speed will increase sharply, and the I value cannot be reduced quickly, and the vehicle state cannot be quickly converged through the PID logic. It should be emphasized that the PID control logic used in automatic parking only uses the P loop and the I loop, and generally does not use the D loop.

[0009] In summary, if the PID value is set aggressively, although the vehicle speed during parking can be increased, the probability of overshoot of the vehicle speed or longitudinal driving distance will increase, resulting in frequent emergency braking during parking; if the PID value is set conservatively, the vehicle speed will be too slow, the parking efficiency will be reduced, and the customer experience will be poor. Summary of the invention

[0010] The present application provides a method and system for longitudinal PID closed-loop control of a vehicle during automatic parking, which can solve the technical problem of low efficiency of automatic parking in the prior art.

[0011] In a first aspect, an embodiment of the present application provides a vehicle longitudinal PID closed-loop control method during automatic parking, characterized in that the method comprises:

[0012] When it is determined that the vehicle has a tendency to exceed the speed limit, the I value is frozen; if the real-time vehicle speed is greater than the upper speed limit after being frozen for a period of time, a rapid speed control action is performed, and the rapid speed control action includes activating the D loop and resetting the I value; if the real-time vehicle speed is still greater than the upper speed limit after the rapid speed control action is performed for a period of time, the action is continued to be performed until the real-time vehicle speed is no greater than the upper speed limit, and then the D loop is returned to the inactive state;

[0013] When it is determined that the vehicle is showing a slow speed trend, a rapid speed control action is executed; if the real-time vehicle speed is less than the lower speed limit after the rapid speed control action has been executed for a period of time, the action is continued until the real-time vehicle speed is not less than the lower speed limit, and then the D circuit returns to the inactive state.

[0014] In combination with the first aspect, in one implementation, when determining that the vehicle has a speeding trend, freezing the I value specifically includes the following steps:

[0015] The D loop inactive state is used as the starting state of the state machine. If the real-time vehicle speed is within the preset vehicle speed range within the first time period, the first timing state is entered and timing is performed;

[0016] After entering the first timing state, if the vehicle acceleration is less than the first acceleration lower limit, the system returns to the starting state;

[0017] After entering the first timing state and the accumulated time exceeds the first time, if the real-time vehicle speed is within the preset vehicle speed range and the vehicle acceleration is greater than the first acceleration upper limit, it is determined that there is a speeding trend and the I value freezing state is entered. In the I value freezing state, the I value remains unchanged.

[0018] In combination with the first aspect, in one implementation, when determining that the vehicle has a speeding trend, freezing the I value specifically includes the following steps:

[0019] After entering the first timing state and the accumulated time exceeds the first time, if the real-time vehicle speed is greater than the upper speed limit of the preset vehicle speed range, a vehicle speed rapid control action is executed;

[0020] If the real-time vehicle speed is still greater than the upper speed limit after the vehicle speed rapid control action is executed for a period of time, the action will continue to be executed until the real-time vehicle speed is no greater than the upper speed limit, and then the D circuit will return to the inactive state.

[0021] In combination with the first aspect, in one implementation, after entering the first timing state and the accumulated duration exceeds the first duration, it is first determined whether the real-time vehicle speed is within a preset vehicle speed range and the vehicle acceleration is greater than a first acceleration upper limit, and then it is determined whether the real-time vehicle speed is greater than the vehicle speed upper limit.

[0022] In combination with the first aspect, in one implementation, after the I value is frozen for a period of time, if the real-time vehicle speed is still greater than the upper speed limit, a vehicle speed rapid control action is performed, specifically including the following steps:

[0023] After the I value is frozen and the cumulative duration exceeds the second duration, if the real-time vehicle speed is not greater than the upper speed limit of the preset speed range, the D circuit returns to the inactive state; if the real-time vehicle speed is greater than the upper speed limit of the preset speed range, the D circuit is activated and the I circuit is reset. In the D circuit activated and I value reset state, the D circuit is activated and the I value is reset.

[0024] In combination with the first aspect, in one implementation, after the I value is frozen and the accumulated duration exceeds a second duration, it is first determined whether the real-time vehicle speed is not greater than the vehicle speed upper limit, and then it is determined whether the real-time vehicle speed is greater than the vehicle speed upper limit.

[0025] In combination with the first aspect, in one implementation, after the vehicle speed rapid control action is executed for a period of time, the D circuit is returned to an inactive state, which specifically includes the following steps:

[0026] After executing the vehicle speed rapid control action and the cumulative time exceeds the third time period, if the real-time vehicle speed is not greater than the upper speed limit of the preset speed range, the D circuit returns to the inactive state; if the real-time vehicle speed is greater than the upper speed limit of the preset speed range, the vehicle speed rapid control action continues to be executed until the real-time vehicle speed is no greater than the upper speed limit of the preset speed range, and then the D circuit returns to the inactive state.

[0027] In combination with the first aspect, in one implementation, when it is determined that the vehicle has a low speed trend, executing a vehicle speed rapid control action specifically includes the following steps:

[0028] The D loop inactive state is used as the starting state of the state machine. If the real-time vehicle speed is less than the lower speed limit of the preset speed range and the vehicle acceleration is less than the second acceleration lower limit, it is determined that a low speed trend occurs and the second timing state is entered.

[0029] After entering the second timing state, if the vehicle acceleration is greater than the second acceleration upper limit, the D circuit returns to the inactive state;

[0030] After entering the second timing state and the accumulated time exceeds the fourth time, if the real-time vehicle speed is less than the lower limit of the preset vehicle speed range, the vehicle speed rapid control action is executed until the real-time vehicle speed is not less than the lower limit of the vehicle speed, and then the D circuit returns to the inactive state.

[0031] In combination with the first aspect, in one implementation, the D value of the D loop is calculated using the following formula:

[0032] Fd=Kd×a

[0033] Wherein, Fd represents the D value of the D loop; Kd represents the differential coefficient; and a represents the vehicle acceleration.

[0034] In a second aspect, an embodiment of the present application provides a vehicle longitudinal PID closed-loop control system during automatic parking, the system comprising:

[0035] A control module, which is used to freeze the I value when it is determined that the vehicle has a tendency to exceed the speed limit; if the real-time vehicle speed is greater than the upper speed limit after freezing for a period of time, a vehicle speed rapid control action is performed, and the vehicle speed rapid control action includes activating the D loop and resetting the I value; if the real-time vehicle speed is still greater than the upper speed limit after the vehicle speed rapid control action is performed for a period of time, the action is continued to be performed until the real-time vehicle speed is no greater than the upper speed limit, and then the D loop is returned to an inactive state;

[0036] The control module is also used to execute a rapid speed control action when it is determined that the vehicle is showing a slow speed trend; if the real-time vehicle speed is less than the lower speed limit after the rapid speed control action has been executed for a period of time, the action will continue to be executed until the real-time vehicle speed is no less than the lower speed limit, and then the D circuit will return to the inactive state.

[0037] The beneficial effects brought by the technical solution provided by the embodiments of the present application include:

[0038] After determining that the vehicle is at risk of losing speed control, the vehicle speed is first converged by freezing the I value. If the vehicle speed still cannot converge, the D loop is activated and the I value is reset to converge the vehicle speed. The improved PID control logic is used to improve the efficiency of automatic parking. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a flow chart of an embodiment of a method for controlling a longitudinal PID closed loop of a vehicle during automatic parking when the vehicle has a tendency to overspeed in the present application;

[0040] Figure 2 It is a flow chart of an embodiment of a method for determining whether a vehicle has a speeding trend when a vehicle longitudinal PID closed-loop control method is used for automatic parking when the vehicle has a low speed trend in this application;

[0041] Figure 3 This is a control logic diagram of the state machine of this application. DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0043] First, some technical terms in the present application are explained to facilitate those skilled in the art to understand the present application.

[0044] In order to make the objectives, technical solutions and advantages of the present application clearer, the implementation methods of the present application will be further described in detail below with reference to the accompanying drawings.

[0045] In a first aspect, an embodiment of the present application provides a method for controlling a longitudinal PID closed-loop control of a vehicle during automatic parking. The method for controlling a longitudinal PID closed-loop control of a vehicle during automatic parking includes:

[0046] When it is determined that the vehicle is speeding, the I value is frozen. If the real-time vehicle speed is greater than the upper speed limit after freezing for a period of time, the vehicle speed rapid control action is executed, which includes activating the D loop and resetting the I value. If the real-time vehicle speed is still greater than the upper speed limit after the vehicle speed rapid control action is executed for a period of time, the action is continued until the real-time vehicle speed is no greater than the upper speed limit, and then the D loop is returned to the inactive state.

[0047] When it is determined that the vehicle has a low speed trend, the vehicle speed rapid control action is executed. If the real-time vehicle speed is less than the lower speed limit after the vehicle speed rapid control action is executed for a period of time, the action will continue to be executed until the real-time vehicle speed is not less than the lower speed limit, and then the D circuit will return to the inactive state.

[0048] For ease of explanation, the control methods when the vehicle has an overspeeding tendency and the vehicle has an underspeed tendency are described separately.

[0049] Reference Figure 1 and Figure 3 , Figure 1 This is a flow chart of an embodiment of a method for controlling a longitudinal PID closed-loop control of a vehicle during automatic parking when the vehicle has a tendency to overspeed in this application. Figure 3 This is a control logic diagram of the state machine of this application. Figure 1 and Figure 3 As shown, the vehicle longitudinal PID closed-loop control method for automatic parking when the vehicle has an overspeeding trend includes:

[0050] Step S1a: the state machine is in the D loop inactive state.

[0051] Step S2a, determining whether the real-time vehicle speed is within a preset vehicle speed range within the first time period:

[0052] If yes, go to step S3a.

[0053] If not, the state machine continues to be in the D loop inactive state.

[0054] Step S3a: The state machine enters the first timing state and starts timing.

[0055] Step S4a, judging whether the vehicle acceleration is less than the first acceleration lower limit:

[0056] If so, the state machine continues to be in the D loop inactive state.

[0057] If not, go to step S5a.

[0058] Step S5a, judging whether the accumulated time of entering the first timing state exceeds the first time, the real-time vehicle speed is within the preset vehicle speed range, and the vehicle acceleration is greater than the first acceleration upper limit:

[0059] If yes, go to step S7a.

[0060] If not, go to step S6a.

[0061] Step S6a, judging whether the accumulated time of entering the first timing state exceeds the first time and the real-time vehicle speed is greater than the upper speed limit:

[0062] If yes, go to step S9a.

[0063] If not, the state machine returns to the first timing state.

[0064] S7a, the state machine enters the I value freezing state and starts timing. In the I value freezing state, the value of the integral item no longer continues to accumulate, that is, it no longer increases.

[0065] S8a, judging whether the accumulated freezing time of the I value exceeds the second time and the real-time vehicle speed is greater than the upper speed limit:

[0066] If yes, go to step S9a.

[0067] If not, the state machine returns to the D loop inactive state.

[0068] S9a, the state machine enters the D loop activation and I value reset state and starts timing.

[0069] Step S10a, judging whether the D circuit is activated and the accumulated time of resetting the I value exceeds the third time and the real-time vehicle speed is greater than the upper speed limit:

[0070] If so, the state machine continues in the D loop active and I value reset state.

[0071] If not, the state machine returns to the D loop inactive state.

[0072] In this embodiment, in the default mode, only the P loop and the I loop are activated in the PID control logic, and the D loop is not activated. The D loop is activated only when the set conditions are met. The D loop inactive state is used as the starting state of the state machine.

[0073] Reference Figure 3 In branch 1, when the vehicle starts to park, the speed will slowly increase or decrease at a certain slope. Generally, the real-time speed is not much different from the target speed and is in a certain range. For example, the difference between the target speed and the real-time speed is Verror, then -0.6km / h≤Verror≤0.6km / h. At this time, the vehicle can be controlled according to the basic PI parameters, but the process needs to last for t, t is the duration of the first time period mentioned above, and then the state machine enters the first timing state. For the sake of convenience, the target speed is set to 5km / h, then the preset speed range corresponding to the real-time speed is [4.4, 5.6], in km / h. It can be seen that the lower speed limit is 4.4km / h and the upper speed limit is 5.6km / h.

[0074] Reference Figure 3 In branch 1.1, after entering the first timing state, if the vehicle starts to decelerate, for example, a<-0.5m / s 2 , here -0.5m / s 2 This is the first acceleration lower limit mentioned above, indicating that the current PI parameters can control the vehicle state more accurately. Then the state machine returns to the D loop inactive state, the timer is reset, and the timing is restarted.

[0075] Reference Figure 3 In branch 1.2, after entering the first timing state, the accumulated time t1 exceeds the first time, for example, t1>0.05s, where 0.05s is the first time, if the real-time speed is not much different from the target speed, for example, it is still in the range of -0.6km / h≤Verror≤0.6km / h, at this time -0.6km / h≤real-time speed≤0.6km / h, but the vehicle acceleration is too large, for example, a>0.3m / s 2 , here 0.3m / s 2 This is the first acceleration upper limit mentioned above, indicating that the vehicle has a tendency to accelerate too much at this time. If the basic PI parameters are allowed to control at this time, since I is the integral cumulative value, I will become larger and larger over time, and the vehicle is likely to exceed the speed limit. To avoid this situation, the current I value should be frozen and not allowed to increase, that is, enter the I value freezing state. When the I value freezing time t2> a certain time, for example t2> 0.05s, the 0.05s here is the second time length mentioned above, and the current state of the vehicle is re-evaluated.

[0076] Reference Figure 3In branch 1.2.1, if t2>0.05, the vehicle still inevitably exceeds the speed limit. When the speed difference exceeds a certain limit, for example, Verror<-0.6, the real-time vehicle speed is>5.6km / h, then the D control logic needs to be introduced to quickly converge the vehicle state. At this time, the accumulated I value is not suitable for vehicle state control, so the I value needs to be reset synchronously and the I value starts to accumulate again from 0.

[0077] Reference Figure 3 In branch 1.4, when the logic is triggered, the D operation time t3 is recorded. When t3 exceeds a certain time, for example, t3>0.05, where 0.05 is the third time length, the vehicle state is re-evaluated. If the vehicle speed is restored to a controllable state at this time, and the actual vehicle speed is not too large, for example, Verror≥-0.6, and the real-time vehicle speed is ≤5.6km / h, then the D logic control can be stopped. If the vehicle speed is still not restored to a controllable state at this time, and the actual vehicle speed is still too large, for example, Verror<-0.6, and the real-time vehicle speed is>5.6km / h, then the D logic control needs to be continued until the vehicle is restored to a controllable state.

[0078] Reference Figure 3 In branch 1.2.2, if t2>0.05, the speeding status of the vehicle is improved and the actual speed is not too much, for example, Verror≥-0.6, and the real-time speed is ≤5.6km / h, it is judged that the I freeze at this time has taken effect and the normal PI control logic can be restored, then the t timer is reset and restarted.

[0079] Among them, the logic priority of branch 1.1 is higher than the logic priority of branch 1.2, the logic priority of branch 1.2 is higher than the logic priority of branch 1.3, and the logic priority of branch 1.1.1 is higher than the logic priority of branch 1.1.2.

[0080] In summary, the I value freezing and I value resetting logic can effectively solve the problem of excessive accumulation of I value abnormalities and continuous side effects of I circuit. When the I value freezing still cannot reduce the vehicle speed to a reasonable range, the D circuit control is started to assist the P circuit and I circuit to control the vehicle speed, so as to quickly control the vehicle speed within a reasonable range.

[0081] Reference Figure 2 and Figure 3 , Figure 2 This is a flow chart of an embodiment of a method for controlling a longitudinal PID closed-loop control of a vehicle during automatic parking when the vehicle is in a low-speed trend in this application. Figure 3 This is a control logic diagram of the state machine of this application. Figure 2 and Figure 3As shown, the vehicle longitudinal PID closed-loop control method for automatic parking when the vehicle has a low speed trend includes:

[0082] Step S1b: the state machine is in the D loop inactive state.

[0083] Step S2b, judging whether the real-time vehicle speed is less than the vehicle speed lower limit and the vehicle acceleration is less than the second acceleration lower limit:

[0084] If yes, go to step S3b.

[0085] If not, the state machine continues to be in the D loop inactive state.

[0086] Step S3b: the state machine enters the second timing state and starts timing.

[0087] Step S4b: determine whether the vehicle acceleration is greater than the second acceleration upper limit:

[0088] If so, the state machine returns to the D loop inactive state.

[0089] If not, go to step S5b.

[0090] Step S5b, judging whether the accumulated time of entering the second timing state exceeds the fourth time and the real-time vehicle speed is less than the lower speed limit:

[0091] If yes, go to step S6b.

[0092] If not, the state machine continues to be in the second timing state.

[0093] Step S6b: the state machine enters the D loop activation and I value reset state and starts timing.

[0094] Step S7a, judging whether the D circuit is activated and the accumulated time of resetting the I value exceeds the fifth time and the real-time vehicle speed is less than the lower speed limit:

[0095] If so, the state machine continues in the D loop active and I value reset state.

[0096] If not, the state machine returns to the D loop inactive state.

[0097] In this embodiment, refer to Figure 3 Branch 2.1 in the figure, when parking starts, there are also special cases (for example, the driver actively brakes during parking, resulting in a low real-time speed but a high target speed. Or at this time, the vehicle encounters resistance, such as speed bumps, curbs, etc., which hinders the vehicle's travel and the real-time speed cannot be increased. The judgment condition is that the speed difference is too large and the vehicle has a deceleration trend, such as Verror>0.6 and a<-0.5m / s 2 , here -0.5m / s 2This is the second lower acceleration limit, which means that the actual vehicle speed is less than the target speed and the vehicle is still decelerating. If the condition is met, the vehicle is controlled according to the basic PI parameters and enters the second timing state to record the duration of this situation t4.

[0098] Reference Figure 3 In branch 2.1.1, after entering the second timing state, if the basic PI control vehicle acceleration a returns to a certain value, for example, a>0.3m / s 2 , here 0.3m / s 2 That is, the second acceleration upper limit mentioned above, which means that the current PI parameter can be that the vehicle state is restored to the convergence state. The monitoring mode of this situation is exited, and the state machine returns to the inactive state of the D loop.

[0099] Reference Figure 3 In branch 2.1.2, after the accumulated time t4 after entering the second timing state exceeds the fourth time, for example, t1>0.05s, where 0.05s is the fourth time, the vehicle state is re-judged. If there is still a large speed difference and the vehicle acceleration is still too small, for example, Verror>-0.6, the real-time vehicle speed is <4.4km / h, indicating that the basic PI parameters cannot quickly adjust the vehicle to the convergence state, then the D control loop needs to be introduced. At this time, the accumulated I value is not suitable for vehicle state control, so the I value needs to be reset synchronously, and the I value starts to accumulate again from 0. When the logic is triggered, the D working time t5 is recorded. When t5 exceeds a certain time, for example, tD>0.05, where 0.05 is the fifth time, the vehicle state is re-evaluated. If the vehicle speed is restored to a controllable state at this time and the actual vehicle speed is not too large, for example, Verror≤0.6, the vehicle speed at this time is ≥4.4km / h, then the control of the D logic can be stopped. If the vehicle speed has not returned to a controllable state at this time, and the actual vehicle speed is still too much, for example, Verror>0.6, and the vehicle speed at this time is <4.4km / h, then it is necessary to continue D logic control until the vehicle returns to a controllable state.

[0100] Furthermore, in one embodiment, the D value of the above D loop is calculated using the following formula (1):

[0101] Fd=Kd×a(1)

[0102] Where, Fd represents the D value of the D loop, Kd represents the differential coefficient, and a represents the vehicle acceleration.

[0103] Compared with the differential control (D loop control) of traditional PID control logic, this patent proposes a new D control logic method. Based on the above scenario, it can be seen that when the D control logic needs to intervene, it means that the vehicle control at this time tends to diverge (out of control). In order to quickly correct the vehicle to the target state, it is necessary to set a more reasonable D intervention logic, and it is necessary to avoid the negative impact of the D control logic on the comfort or control target of the whole vehicle. After actual vehicle verification, it is found that Fd = Kd*a has the best effect, where Kd is a coefficient (this value needs to be calibrated based on the actual vehicle, for example, for a 2.5T vehicle, this value is set to 100, and the actual vehicle effect is better), and a is the current vehicle acceleration.

[0104] The advantage of this method is that Fd outputs the control amount based on the current vehicle acceleration, which can quickly correct the trend of actual vehicle speed divergence and make V vehicle tend to V target more quickly. During the D action period, FI is reset to further eliminate the impact of the accumulated I control amount on vehicle loss of control. An exit threshold is set for the D control loop to avoid the negative impact of a strong D control amount on the longitudinal state of the vehicle.

[0105] In summary, the present invention solves the problem that the vehicle continues to run in a non-ideal state due to excessive accumulation of FI in special circumstances, and improves the control accuracy and safety during automatic parking. The I freeze and I reset logics better solve the problem of excessive accumulation of I abnormalities and continuous side effects of FI. The D control logic can better correct the state of the out-of-control vehicle in a timely manner and converge it to a controllable state, and the side effects of the D control loop are relatively small, and the actual vehicle application effect is good.

[0106] In a second aspect, the embodiment of the present application further provides a vehicle longitudinal PID closed-loop control system during automatic parking, comprising:

[0107] The control module is used to freeze the I value when it is determined that the vehicle has a tendency to exceed the speed limit. If the real-time vehicle speed is greater than the upper speed limit after freezing for a period of time, the vehicle speed rapid control action is executed, and the above-mentioned vehicle speed rapid control action includes activating the D loop and resetting the I value. If the real-time vehicle speed is still greater than the upper speed limit after the vehicle speed rapid control action is executed for a period of time, the action is continued until the real-time vehicle speed is no greater than the upper speed limit, and then the D loop is returned to the inactive state.

[0108] The control module is also used to execute the vehicle speed rapid control action when it is determined that the vehicle has a low speed trend. If the real-time vehicle speed is less than the lower speed limit after the vehicle speed rapid control action is executed for a period of time, the action will continue to be executed until the real-time vehicle speed is not less than the lower speed limit, and then the D circuit will return to the inactive state.

[0109] In this embodiment, after determining that the vehicle is at risk of losing speed control, the control module first freezes the I value to converge the vehicle speed. If the vehicle speed still cannot converge, the D loop is activated and the I value is reset to converge the vehicle speed, thereby improving the efficiency of automatic parking by using improved PID control logic.

[0110] Among them, the functional implementation of the module in the above-mentioned vehicle longitudinal PID closed-loop control system during automatic parking corresponds to the steps in the above-mentioned vehicle longitudinal PID closed-loop control method embodiment during automatic parking, and its functions and implementation processes are no longer repeated here.

[0111] It should be noted that the serial numbers of the above-mentioned embodiments of the present application are only for description and do not represent the advantages or disadvantages of the embodiments.

[0112] The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices. The terms "first", "second" and "third" are used to distinguish different objects, etc., and do not represent a sequence, nor do they limit "first", "second" and "third" to different types.

[0113] In the description of the embodiments of the present application, "exemplary", "for example" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary", "for example" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "for example" or "for example" is intended to present related concepts in a specific way.

[0114] In the description of the embodiments of the present application, unless otherwise specified, " / " means or, for example, A / B can mean A or B. "And / or" in the text is only a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, "multiple" means two or more than two.

[0115] In some processes described in the embodiments of the present application, multiple operations or steps that appear in a specific order are included, but it should be understood that these operations or steps may not be executed in the order in which they appear in the embodiments of the present application or in parallel, and the sequence number of the operation is only used to distinguish the different operations, and the sequence number itself does not represent any execution order. In addition, these processes may include more or fewer operations, and these operations or steps may be executed in sequence or in parallel, and these operations or steps may be combined.

[0116] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, disk, CD) as described above, and includes a number of instructions for a terminal device to execute the methods described in each embodiment of the present application.

[0117] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A vehicle longitudinal PID closed-loop control method for automatic parking, characterized in that: The method comprises: When it is determined that the vehicle has a tendency to exceed the speed limit, the I value is frozen; if the real-time vehicle speed is greater than the upper speed limit after being frozen for a period of time, a rapid speed control action is performed, and the rapid speed control action includes activating the D loop and resetting the I value; if the real-time vehicle speed is still greater than the upper speed limit after the rapid speed control action is performed for a period of time, the action is continued to be performed until the real-time vehicle speed is no greater than the upper speed limit, and then the D loop is returned to the inactive state; When it is determined that the vehicle is showing a slow speed trend, a rapid speed control action is executed; if the real-time vehicle speed is less than the lower speed limit after the rapid speed control action has been executed for a period of time, the action is continued until the real-time vehicle speed is not less than the lower speed limit, and then the D circuit returns to the inactive state.

2. The vehicle longitudinal PID closed-loop control method for automatic parking as claimed in claim 1, characterized in that: When it is determined that the vehicle has a speeding trend, freezing the I value specifically includes the following steps: The D loop inactive state is used as the starting state of the state machine. If the real-time vehicle speed is within the preset vehicle speed range within the first time period, the first timing state is entered and timing is performed; After entering the first timing state, if the vehicle acceleration is less than the first acceleration lower limit, the system returns to the starting state; After entering the first timing state and the accumulated time exceeds the first time, if the real-time vehicle speed is within the preset vehicle speed range and the vehicle acceleration is greater than the first acceleration upper limit, it is determined that there is a speeding trend and the I value freezing state is entered. In the I value freezing state, the I value remains unchanged.

3. The vehicle longitudinal PID closed-loop control method for automatic parking as claimed in claim 2, characterized in that: When it is determined that the vehicle has a speeding trend, freezing the I value specifically includes the following steps: After entering the first timing state and the accumulated time exceeds the first time, if the real-time vehicle speed is greater than the upper speed limit of the preset vehicle speed range, a vehicle speed rapid control action is executed; If the real-time vehicle speed is still greater than the upper speed limit after the vehicle speed rapid control action is executed for a period of time, the action will continue to be executed until the real-time vehicle speed is no greater than the upper speed limit, and then the D circuit will return to the inactive state.

4. The vehicle longitudinal PID closed-loop control method for automatic parking as claimed in claim 3, characterized in that: After entering the first timing state and the accumulated time exceeds the first time, it is first determined whether the real-time vehicle speed is within the preset vehicle speed range and the vehicle acceleration is greater than the first acceleration upper limit, and then it is determined whether the real-time vehicle speed is greater than the vehicle speed upper limit.

5. The vehicle longitudinal PID closed-loop control method for automatic parking as claimed in claim 1, characterized in that: After the I value is frozen for a period of time, if the real-time vehicle speed is still greater than the upper speed limit, a vehicle speed rapid control action is performed, which specifically includes the following steps: After the I value is frozen and the cumulative duration exceeds the second duration, if the real-time vehicle speed is not greater than the upper speed limit of the preset speed range, the D circuit returns to the inactive state; if the real-time vehicle speed is greater than the upper speed limit of the preset speed range, the D circuit is activated and the I circuit is reset. In the D circuit activated and I value reset state, the D circuit is activated and the I value is reset.

6. The vehicle longitudinal PID closed-loop control method for automatic parking as claimed in claim 5, characterized in that: After the I value is frozen and the accumulated duration exceeds the second duration, it is first determined whether the real-time vehicle speed is not greater than the vehicle speed upper limit, and then it is determined whether the real-time vehicle speed is greater than the vehicle speed upper limit.

7. The vehicle longitudinal PID closed-loop control method for automatic parking as claimed in claim 1, characterized in that: After the vehicle speed rapid control action is executed for a period of time, the D circuit returns to the inactive state, which specifically includes the following steps: After executing the vehicle speed rapid control action and the cumulative time exceeds the third time period, if the real-time vehicle speed is not greater than the upper speed limit of the preset speed range, the D circuit returns to the inactive state; if the real-time vehicle speed is greater than the upper speed limit of the preset speed range, the vehicle speed rapid control action continues to be executed until the real-time vehicle speed is no greater than the upper speed limit of the preset speed range, and then the D circuit returns to the inactive state.

8. The vehicle longitudinal PID closed-loop control method for automatic parking as claimed in claim 1, characterized in that: When it is determined that the vehicle has a low speed trend, the vehicle speed rapid control action is executed, which specifically includes the following steps: The D loop inactive state is used as the starting state of the state machine. If the real-time vehicle speed is less than the lower speed limit of the preset speed range and the vehicle acceleration is less than the second acceleration lower limit, it is determined that a low speed trend occurs and the second timing state is entered. After entering the second timing state, if the vehicle acceleration is greater than the second acceleration upper limit, the D circuit returns to the inactive state; After entering the second timing state and the accumulated time exceeds the fourth time, if the real-time vehicle speed is less than the lower limit of the preset vehicle speed range, the vehicle speed rapid control action is executed until the real-time vehicle speed is not less than the lower limit of the vehicle speed, and then the D circuit returns to the inactive state.

9. The vehicle longitudinal PID closed-loop control method for automatic parking as claimed in claim 1, characterized in that: The D value of the D loop is calculated using the following formula: Fd=Kd×a Wherein, Fd represents the D value of the D loop; Kd represents the differential coefficient; and a represents the vehicle acceleration.

10. A vehicle longitudinal PID closed-loop control system for automatic parking, characterized in that: The system comprises: A control module, which is used to freeze the I value when it is determined that the vehicle has a tendency to exceed the speed limit; if the real-time vehicle speed is greater than the upper speed limit after freezing for a period of time, a vehicle speed rapid control action is performed, and the vehicle speed rapid control action includes activating the D loop and resetting the I value; if the real-time vehicle speed is still greater than the upper speed limit after the vehicle speed rapid control action is performed for a period of time, the action is continued to be performed until the real-time vehicle speed is no greater than the upper speed limit, and then the D loop is returned to an inactive state; The control module is also used to execute a rapid speed control action when it is determined that the vehicle is showing a slow speed trend; if the real-time vehicle speed is less than the lower speed limit after the rapid speed control action has been executed for a period of time, the action will continue to be executed until the real-time vehicle speed is no less than the lower speed limit, and then the D circuit will return to the inactive state.

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