A method for adjusting a controller in a vehicle

Abstract

A method for adjusting a controller in a vehicle A method for adjusting a controller (210) in a vehicle (100), the controller (210) being configured to control a vehicle motion depending on at least a proportional gain (236) and a derivative gain (240), the method comprising: 1a) comparing (S600) a current vehicle acceleration (204) to a reference vehicle acceleration (224) to determine an acceleration error (230), and a current vehicle jerk (222) to a reference vehicle jerk (226) to determine a jerk error (232); and 10 1b) adjusting (S601) the proportional gain (236) and the derivative gain (240) depending on the acceleration error (230) and the jerk error (232) of step 1a).

Description

[0001] A METHOD FOR ADJUSTING A CONTROLLER IN A VEHICLE

[0002] The present invention relates to a method for adjusting a controller in a vehicle, a computer program product, a system, and a vehicle.

[0003] Controllers (e.g., PID (proportional-integral-derivative) or other low-level controllers) in vehicles play a critical role in managing the operation of various vehicle subsystems, such as ACC (adaptive cruise control) systems for controlling the motion of the vehicle, including, for example, acceleration and steering. These controllers may be embedded in an electronic control unit, wherein the electronic control unit is implemented to receive input data measured by sensors of the vehicle and provide output data, which may be a control action.

[0004] Known controllers may be designed to apply a control strategy, such as a closed-loop feedback control. The received input data typically comprises a desired vehicle motion, such as a desired acceleration, provided, for example, by the ACC-system of the vehicle. For instance, a front camera of the vehicle detects a braking vehicle in front. The camera will then output a corresponding desired deceleration as the desired vehicle motion as input data to the controller. The desired vehicle motion is compared to an actual vehicle motion measured using odometry sensors, for example, and also provided as input data to the controller. The actual vehicle motion may be influenced by external factors, such as a road gradient. Depending on the comparison, an error is determined, wherein the controller outputs a control signal, for example to the vehicle engine, to compensate the error.

[0005] One object of the invention is to provide an improved method for adjusting a controller in a vehicle.

[0006] According to a first aspect, there is provided a method for adjusting a controller in a vehicle. The controller is configured to control a vehicle motion depending on at least a proportional gain and a derivative gain. The method comprises: 1a) comparing a current vehicle accelera- tion to a reference vehicle acceleration to determine an acceleration error, and a current vehicle jerk to a reference vehicle jerk to determine a jerk error; and 1 b) adjusting the proportional gain and the derivative gain depending on the acceleration error and the jerk error of step 1a).

[0007] Adjusting the proportional gain and the derivative gain depending on the acceleration error and the jerk error enables improved transient control, i.e., before the controlled vehicle behaves as the reference closed-loop. In particular, the inventors realized that some errors can be tolerated for longer time compared to others. As an example, one may tolerate for longer times to have acceleration which is smaller compared to the reference (i.e. the vehicle brakes more and accelerates less) compared to the opposite cases (i.e. acceleration greater than the reference). Being more tolerant or requiring faster error convergence, is achieved, in accordance with the present approach, by changing the error rejection rate dynamically. Preferably, the error rejection rate is derived from vehicle safety requirements. A controller adjusted in this way may improve driving safety.

[0008] The controller may be a microcontroller and / or may be part of an electronic control unit (ECU) of the vehicle.

[0009] The controller may comprise a PID controller, a PD controller, or a PIDF controller, or any relevant controller structure according to the required vehicle mathematical description, wherein a PID controller is combined with a first order filter F. “P” refers to the proportional gain, “I” refers to an integral gain, and “D” refers to the derivative gain. In examples, the controller may comprise a PID controller and a further term or offset term, wherein the offset term may be an adjustable value.

[0010] The first order filter F may be implemented to smoothen an input signal and output the smoothened signal. The first order filter F is, for example, a low-pass filter or a high-pass filter. The vehicle motion may comprise an acceleration, a jerk, a velocity, an engaged gear, and / or a yaw of the vehicle.

[0011] "Comparing a current vehicle acceleration to a reference vehicle acceleration" may comprise performing a mathematical operation on the current vehicle acceleration and the reference vehicle acceleration, as well as on the current vehicle jerk and the reference vehicle jerk, respectively. For example, the mathematical operation may include addition, subtraction, multiplication, division, exponentiation, and / or root extraction.

[0012] The current vehicle acceleration may be provided by a sensor of the vehicle, in particular, an inertial measurement unit (IMU), an accelerometer, a gyroscope, awheel speed sensor, a yaw rate sensor, a global positioning system (GPS) sensor and / or a steering angle sensor. The current vehicle acceleration comprises, for example, a current acceleration of the vehicle, including a positive acceleration (accelerating), a negative acceleration (braking), and / or a current yaw (steering) of the vehicle.

[0013] The current vehicle jerk may be determined depending on the current vehicle acceleration. For example, the current vehicle jerk may be determined as the derivative of the current vehicle acceleration. Or, the current vehicle jerk is measured directly. In particular, the current vehicle jerk is determined by using a filter, for example a Kalman filter.

[0014] The reference vehicle acceleration and / or the reference vehicle jerk may be provided by a reference equation or table, wherein the reference equation or table is determined before step 1a). The reference vehicle acceleration and / or the reference vehicle jerk corresponds to a desired behavior of the vehicle acceleration, and / or the vehicle jerk. The reference vehicle acceleration and / or the reference vehicle jerk may depend on an acceleration request and / or jerk request from the vehicle's ACC system. “Adjusting” comprises, for example, performing one of the previously described mathematical operations to the proportional gain and the derivative gain, or any other controller parameters. In particular, the proportional gain and the derivative gain are adjusted by adding or subtracting, respectively, a value. The respective value may be the result from an equation.

[0015] According to a further embodiment, in step 1b), the proportional gain and the derivative gain are adjusted depending on a function of the acceleration error and the jerk error, the function being defined before step 1a).

[0016] The function, which may include computationally intensive work, is determined before the controller is deployed in the vehicle. Thus, when the controller is controlling the vehicle motion and performing the above-described method steps, only the function is executed, reducing computation time.

[0017] The function may comprise a mathematical equation or table, relating the respective acceleration error and the jerk error to an adjustment value, wherein the table may be stored on a storage device of the vehicle.

[0018] According to a further embodiment, the function defines, for a first set of values of the acceleration error and the jerk error, first adjustment values, and, for a second set of values of the acceleration error and the jerk error, second adjustment values different from the first adjustment values, and step 1b) further comprises: comparing the acceleration error and the jerk error of step 1a) to the first set of values and the second set of values, and adjusting, depending on the comparison, the proportional gain and the derivative gain using the first or second adjustment values.

[0019] This represents an efficient way of adjusting the controller. In particular, the first and second set of values may correspond to different zones within a coordinate system comprising the acceleration error and the jerk error. In particular, the first and second adjustment values respectively are a matrix, wherein the matrix is a symmetric 2x2 matrix. In particular, the first and second adjustment values respectively comprise a maximum of two values, or any other matrix size which is compatible with the number of elements that contribute to adjust gain values.

[0020] Comparing the acceleration error and the jerk error of step 1a) to the first set of values and the second set of values may comprise determining whether the acceleration error and the jerk error lie within the first or the second set of values, i.e. within corresponding zones.

[0021] According to a further embodiment, one or each value in the first set of values is smaller than one or each value in the second set of values, and one or each of the first adjustment values is smaller than one or each of the second adjustment values.

[0022] The controller behavior depends on the value of the proportional gain and the derivative gain, or any other controller parameters. Advantageously, by adjusting the proportional gain and the derivative gain with smaller or larger values, depending on the respective first or second set of values, a varying behavior of the controller is achieved.

[0023] According to a further embodiment, the first adjustment values are constant for all values within the first set of values, the number of values within the first set exceeding two, the second adjustment values are constant for all values within the second set of values, the number of values within the second set exceeding two, the function defines third adjustment values for a third set of values, wherein the third adjustment values lie in between the first and the second adjustment values and the third set of values lies in between the first and second set of values.

[0024] Since the third adjustment values lie in between the first and the second adjustment values, the described approach allows for a more flexible adjustment of the proportional gain and the derivative gain. The third adjustment values can also be said to correspond to a transition region between the first and second set of values. In particular, the third set of values may comprise the origin of the above-mentioned coordinate system. Phrased differently, the third set of values may comprise a zero value.

[0025] According to a further embodiment, the function determines the third adjustment values using many-valued logic, in particular fuzzy logic.

[0026] Advantageously, using fuzzy logic to determine the third adjustment values, a smooth transition between the first, second, and third adjustment values is enabled. Therefore, abrupt shifts of the adjustment of the proportional gain and the derivative gain are avoided.

[0027] “Many-valued logic” is a type of non-classical logic that extends beyond a binary framework. Many-valued logic allows for more than two possible truth values, and, therefore, may be useful in dealing with situations where truth is not strictly binary. Many-valued logic comprises, for example, Lukasiewicz logic, three-valued logic, or four-valued logic.

[0028] Fuzzy logic is a type of many-valued logic that allows for reasoning with uncertain or imprecise information, compared to binary logic, wherein binary logic assigns either a “true” (1) value or a “false” (0) value to a parameter. With fuzzy logic, a spectrum of truth values, ranging, for example, from 0 to 1 is introduced. A parameter may, for example, be 0.7 true and 0.3 false, representing partial membership in a set.

[0029] In particular, fuzzy logic is used to transition from the first adjustment value to the second adjustment value, and / or from the second adjustment value to the third adjustment value.

[0030] In this embodiment, there are three sets of values. However, it can be extended to any number of values as required by requirements or others.

[0031] According to a further embodiment, the function is determined using a stability criterion, in particular using a Lyapunov equation. Advantageously, using the Lyapunov equation to determine the function ensures that the function maintains a stable behavior, even during adjustment of controller parameters.

[0032] The stability criterion is used to preserve stability of the controller. “Stability” refers to the behavior of a dynamic system, for example, the vehicle, when it is subjected to external inputs or disturbances. A system is considered stable if, after a disturbance, it returns to its equilibrium state or operates within a bounded range over time.

[0033] Further stability criteria comprise, for example, the Routh-Hurwitz Criterion, Nyquist and Bode Criteria, or the Eigenvalue Analysis.

[0034] “Lyapunov equation” may refer to Lyapunov’s direct method, wherein a Lyapunov function is used to prove whether the system is stable. The Lyapunov function, in particular, decreases over time to a minimum which may be the value zero.

[0035] According to a further embodiment, the adjustment of the proportional gain and the derivative gain in step 1b) is determined as follows:

[0036]

[0037] wherein:

[0038] K is a vector representing the proportional gain and the derivative gain;

[0039] wherein eais the acceleration error and e, is the jerk error and t is the

[0040]

[0041] time;

[0042] B =, wherein B determines how the current vehicle acceleration and the current vehicle jerk are influenced by the controller requests; and

[0043] t ® matrix P is positive definite, and pi,n, Pi,i2, and Pi,22 are val

[0044]

[0045] ues which compensate the acceleration error and the jerk error;

[0046] a vector comprising the acceleration error (230) and the jerk error (232); and

[0047]

[0048] Zi refers to the ithset of values of a reference acceleration error and a reference jerk error, each set i being associated with a different matrix Pi, wherein i ranges from 1 - N, with N > 1.

[0049] Pi may be determined by solving the following equation:

[0050] AfPt+ PtA* = -Q

[0051] wherein:

[0052]

[0053] Kd* is the derivative gain;

[0054] Kp* is the proportional gain; and

[0055] Q is a positive definite symmetric matrix.

[0056] For example, N > 1, 3, 5 or 10. Thus, different zones Zi are defined, each associated with a specific matrix Pi, preferably offering safety benefits in each corresponding driving situation. Each zone includes reference acceleration errors and reference jerk errors, meaning prior to step 1a) recorded or predefined (e.g., in simulation) values.

[0057] It may be provided that in step 1b) the relationship between dK / dt and e is not calculated by the formula above, but that this relationship is derived from a table or the like. The table or similar means is created during the design and possibly simulation phase of the controller, i.e., prior to step 1a).

[0058] According to a further embodiment, the proportional gain and the derivative gain are adjusted in step 1b) such that, when the reference vehicle acceleration is negative, the current vehicle acceleration stays or becomes more negative than the reference vehicle acceleration, and when the reference vehicle acceleration is positive, the current vehicle acceleration stays or becomes less positive than the reference vehicle acceleration.

[0059] Thereby, driving safety is increased. A negative current vehicle acceleration refers to a braking / decelerating vehicle, whereas a positive current vehicle acceleration refers to an accelerating vehicle.

[0060] According to a further aspect, there is provided a computer program product comprising instruction which, when carried out by a control device of the vehicle, causes the control device to perform the method according to the first aspect.

[0061] The computer program product, such as a computer program means, may be embodied as a memory card, as a flashable memory device, as a ROM, PROM or EEPROM, as a USB stick, CD-ROM, DVD, or as a file which may be downloaded from a server in a network. For example, such a file may be provided by transferring the file comprising the computer program product from a wireless communication network.

[0062] According to a further aspect, there is provided a system, in particular an ACC system, comprising a controller in a vehicle, the controller being configured to control a vehicle motion depending on at least a proportional gain and a derivative gain; and a device including: a comparing unit for comparing a current vehicle acceleration to a reference vehicle acceleration to determine an acceleration error, and a current vehicle jerk to a reference vehicle jerk to determine a jerk error, an adjustment unit for adjusting the proportional gain and the derivative gain depending on the acceleration error and the jerk error.

[0063] The respective "unit", e.g., the comparing unit, and / or the adjustment unit, may be implemented using hardware and / or software. In a hardware implementation, the respective unit may, for example, be designed as a computer or a microprocessor. In a software implementation, the respective unit may be designed as a computer program product, as a function, as a routine, as an algorithm, as part of a program code, or as an executable object. Furthermore, each of the above-mentioned units may also be designed as part of a higher-level control system of the vehicle, such as the ECU and / or an engine control unit. According to a further embodiment, the adjustment unit is configured to adjust the proportional gain and the derivative gain depending on a function of the acceleration error and the jerk error, the function being stored on a storage unit of the device.

[0064] The adjustment unit may adjust the proportional gain and the derivative gain in a continuous way. In particular, the adjustment unit adjusts the proportional gain and the derivative gain depending on the function of the acceleration error and the jerk error as long as the acceleration error and the jerk error deviate from zero.

[0065] According to a further aspect, there is provided a vehicle comprising the system of one of the previous aspects.

[0066] In particular, the vehicle may be a motor vehicle such as an automobile, a bus, a lorry, a truck, and the like.

[0067] The features, embodiments, and advantages described for the method of the first aspect also apply, mutatis mutandis, to the further aspects and vice versa.

[0068] Where reference is made to a "first", "second", etc. element, set, or value, or steps 1a), 1b), etc. herein, the skilled person will understand that this merely serves the purpose of distinguishing the different elements or steps but does not imply an order, also not to the extent that the presence of a first and third set requires the presence of a second set (unless stated explicitly otherwise).

[0069] Further possible implementations or alternative solutions of the invention also encompass combinations - that are not explicitly mentioned herein - of features described above or below with regard to the embodiments. The person skilled in the art may also add individual or isolated aspects and features to the most basic form of the invention. Further embodiments, features, and advantages of the present invention will become apparent from the subsequent description and dependent claims, taken in conjunction with the accompanying drawings, in which:

[0070] Fig. 1 shows schematically a top view of a vehicle;

[0071] Fig. 2 shows schematically a detailed view of an ACC system and an ECU;

[0072] Fig. 3 shows a diagram of a reference jerk error vs. a reference acceleration error, divided in different zones;

[0073] Fig. 4 shows a diagram of acceleration vs. time, with graphs representing a reference acceleration as well as a current acceleration;

[0074] Fig. 5 shows graphs related to different control methods; and

[0075] Fig. 6 shows steps of a method according to an embodiment.

[0076] Fig. 1 shows a schematic view of an ego vehicle 100 from a bird's eye view. The ego vehicle 100 is, for example, a passenger car or lorry arranged in an environment 102. The ego vehicle 100 has a control system 104, for example, an electronic control unit (ECU), configured to control a motion of the ego vehicle 100, which is explained in more detail later on. In addition, a plurality of environmental sensor devices 106, 108 are arranged on the ego vehicle 100. These are, for example, optical sensors 106 and ultrasonic sensors 108. The optical sensors 106 comprise, for example, visual cameras, radar, and / or lidar. The optical sensors 106 may each capture an image of a respective area from the environment 102 of the ego vehicle 100 and output it as a sensor signal. The ultrasonic sensors 108 are set up to detect a distance to objects located in the environment 102 and provide an output as a sensor signal. The sensor signal is received and processed by the ECU 104 to control the motion of the ego vehicle For example, the ego vehicle 100 may have an automation level according to the SAE classification system. The SAE classification system was published in 2014 by SAE International, a standardization organization for motor vehicles, as J3016, ‘Taxonomy and Definitions for Terms Related to On-Road Motor Vehicle Automated Driving Systems’. It is based on six different levels of automation and takes into account the degree of system intervention and driver attention required. The SAE automation levels range from level 0, which corresponds to a fully manual system, through driver assistance systems at levels 1 to 2, to semi-autonomous (levels 3 and 4) and fully autonomous (level 5) systems, where a driver is no longer required. An autonomous vehicle (also known as a driverless car, self-driving car, and robotic car) is a vehicle that is able to sense the environment 102 and navigate without human input, and it corresponds to SAE automation level 5.

[0077] The ECU 104 is set up to implement automated driving features to provide an automation level as described above, wherein the automation level can be any level from level 1 to level 5. For example, the ECU 104 is configured to provide one or more of the following functions: an adaptive cruise control (ACC), lane keeping assistance (LKA), automatic emergency braking (AEB), automatic emergency steering (AES), Traffic Jam Assist (TJA), Highway Assist (HWA) and / or Traffic Jam Pilot (TJP).

[0078] Fig. 2 shows schematically a more detailed view of the vehicle 100, comprising an ACC system 200, wherein the ACC system 200 comprises the front camera 106 and the ECU 104. A vehicle drive train 202 is controlled by an (e.g. hydraulic) actuator 110, which acts on, for example, an accelerator pedal and / or a brake pedal, and thus the vehicle 100 accelerates or brakes (not shown in Fig. 2). This results in a current vehicle motion, which comprises a current vehicle acceleration 204. The ACC system 200 provides an output signal to the actuator 110, thereby controlling its action on the accelerator pedal and / or a brake pedal.

[0079] In another example not shown, the actuator 110 acts on a steering system of the vehicle 100 to set a steering angle, which generates a yaw of the vehicle 100. When the ACC system 200 is used to control the current vehicle acceleration 204, the front camera 106 is used to monitor the environment 102 the vehicle 100 by recording images of the environment 102. A determining unit 206 receives the images recorded by the front camera 106, and generates an acceleration request 208, for example, after applying an object detection algorithm to the respective image and evaluating the current driving situation based thereon. The acceleration request 208 is provided to the ECU 104. Additionally, the ECU 104 receives the current vehicle acceleration 204, which is measured by a sensor, for example an inertial measurement unit (IMU), of the vehicle 100 (not shown in Fig. 2).

[0080] The ECU 104 comprises several subsystems. A first subsystem of the ECU 104 is a controller 210 (e.g., a low-level controller such as a PDI controller, which may be implemented as a first microprocessor or software routine), a second subsystem is a device 212 (which may be implemented as a second microprocessor or software routine) comprising a reference unit 214, a comparing unit 216, and an adjustment unit 218, and a third subsystem is a Kalman filter 220 (which may be implemented as a third microprocessor or software routine).

[0081] The Kalman filter 220 determines, depending on the current vehicle acceleration 204 ("a"), a current vehicle jerk 222 ("j"). The current vehicle jerk 222 is the rate of change of the current vehicle acceleration 204. The current vehicle acceleration 204 and the current vehicle jerk 222 are combined to a first state vector x=[a;j] and provided as input to the device 212 and to the controller 210.

[0082] The reference unit 214 of the device 212 receives the previously mentioned acceleration request 208 from the front camera 106 and provides a reference vehicle acceleration aref224 and a reference vehicle jerk jref226, combined in a second state vector xref=[aref, jref]. The reference unit 214 takes, for generating the reference vehicle acceleration 224 and the reference vehicle jerk 226, user parameters into account, which represent a preference of a driver 228 of the vehicle 100. These user parameters may be determined, for example, by a driving mode set by the driver 228. The driving modes may be, for example, a sport mode, a comfort mode and an eco mode.

[0083] The reference unit 214 provides the second state vector to the comparing unit 216, wherein the comparing unit 216 determines an acceleration error ea230 and a jerk error e, 232. The acceleration error 230 may be determined by the function ea= a - aref, and the jerk error 232 may be determined by the function

[0084]

[0085] = j -jref. The acceleration error 230 and the jerk error 232 are provided to the adjustment unit 218.

[0086] The adjustment unit 218 comprises, e.g., a table 234 stored on a storage device (e.g., nonvolatile memory) accessed by the ECU 104. The table 234 is generated at a design stage of the vehicle 100 and comprises recorded sets of acceleration errors 230 and jerk errors 232, each set associated with a proportional gain update value and a derivative gain update value. The current acceleration error 230 and the jerk error 232 are compared to the entries (sets) within the table 234 and the assigned proportional gain update value and derivative gain update value are determined. The adjustment unit 218 may further an integral gain update value and an offset gain update value, wherein the proportional gain update value, the derivative gain update value, the integral gain update value and the offset gain update value are provided to the controller 210.

[0087] The controller 210 comprises a proportional gain 236, an integral gain 238, a derivative gain 240, and an offset gain 242, wherein depending on the acceleration request 208, the reference vehicle acceleration 224 and the reference vehicle jerk 226, and the current vehicle acceleration 204 and the current vehicle jerk 222, the controller 210 generates a control signal 244. The control signal 244 is provided to the actuator 110 to act, as previously described, on the drive train 202 of the vehicle 100. The controller 210, the reference unit 214, and the adjustment unit 218 are designed at a design stage of the vehicle 100 (i.e., prior to method step S600 in Fig. 6). To this end, for instance the following system equation is determined, describing the vehicle 100 controlled by the controller 210:

[0088]

[0089] wherein:

[0090] j is the current vehicle jerk 222;

[0091] a is the current vehicle acceleration 204;

[0092] t is the time;

[0093] f(.), g(.), and h(.) are unknown functions which represent a behavior of the vehicle 100; and

[0094] u is the control signal 244 generated by the controller 210.

[0095] When receiving the acceleration request 208, the reference unit 214 of the device 212 determines a reference vehicle acceleration 224 and a reference vehicle jerk 226 using a reference equation:

[0096]

[0097] wherein:

[0098] jref is the reference vehicle jerk 226;

[0099] aref is the reference vehicle acceleration 224;

[0100] ω and ξ are the parameters selected depending on preferences of the driver 228; and areqis the acceleration request 208 provided by the front camera 106.

[0101] The adjustment unit 218 is designed with the objective to make the current vehicle acceleration 204 and the current vehicle jerk 222 behave like the reference vehicle acceleration 224 and the reference vehicle jerk 226 and provide depending thereon, adjustment to the proportional gain 236 and the derivative gain 240. To achieve this objective, the control signal u (to the actuator 110, for example) is assumed in the previously mentioned design stage as follows:

[0102]

[0103] wherein:

[0104] f̂(.), ĝ(.) and ĥ(.) represent estimated functions for the unknown functions f(.), g(.) and h(.); and

[0105] v is a parameter to ensure that the current vehicle acceleration 204 and the current vehicle jerk 222 behave like the reference vehicle acceleration 224 and the reference vehicle jerk 226.

[0106] Now, when u is inserted in the system equation, the system equation transforms to:

[0107]

[0108] wherein

[0109]

[0110] The acceleration error 230 and the jerk error 232 are determined by the comparing unit 216. During the design stage, by following the approach of the comparing unit 216 and applying the above-described functions, the acceleration error 230 is determined by: ea= a - aref, and the jerk error 232 is determined by:

[0111]

[0112] = j -jref. Thus, an equation depending on the system equation and the reference equation is written as:

[0113]

[0114] In the next step, v is defined as

[0115]

[0116] wherein:

[0117] Koff, Kp, Kd, and represent the offset gain 242, the proportional gain 236, the derivative gain 240, and the integral gain 238.

[0118] Next, the adjustment unit 218 is designed. Therefore, an update law for Koff, Kp, Kd, and is defined to ensure stable behavior of the vehicle 100 when controlled by the controller 210, using a Lyapunov approach. First, it is assumed that there exists a perfect offset gain 242 and a perfect integral gain 240 to compensate for A. The acceleration error 230 and the jerk error 232 are therefore represented by:

[0119]

[0120] wherein

[0121] Kp* and Kd* are the proportional gain 236 and the derivative gain 240 selected for the controlled vehicle 100 to be stable, with a first rejection rate of the acceleration error 230 and the jerk error 232.

[0122] Since the so controlled vehicle 100 now represents a stable behavior due to the selected proportional gain 236 and the derivative gain 240, there exist a solution to the following Ricatti equation: Ai*TPi+ PiAi* = -Q,

[0123] wherein:

[0124] Piis a positive definite matrix for updating the proportional gain 236 and

[0125]

[0126] the derivative gain 240; and

[0127] Q is a positive definite symmetric matrix defined during the design stage of the vehicle 100. To determine the update law, the following Lyapunov equation is used:

[0128] V(e) = eTPie + (K - K*)TΓ-1(K - K*)

[0129] wherein:

[0130] f 0 is a matrix defined during the design stage of the vehicle 100;

[0131] prising the acceleration error 230 and the jerk error 232;

[0132] vector comprising the offset gain 242, the proportional gain 236,

[0133]

[0134] the derivative gain 240, and the integral gain 238; and

[0135] 8 is an additional degree of freedom.

[0136] Next, the derivative of the Lyapunov equation is determined:

[0137]

[0138] wherein:

[0139]

[0140] The update law for the proportional gain 236 and the derivative gain 240 are chosen accordingly to:

[0141]

[0142] wherein Zi refers to the ithset of values of a reference acceleration error and a reference jerk error, each set i being associated with a different matrix Pi, wherein i ranges from 1 to N with N > 1 (e.g., N > 5 or 10). More specifically, the matrix Pi is chosen depending on the current acceleration error 230 and the jerk error 232, as explained with Fig. 3. Fig. 3 shows a first coordinate system 300 having a x-axis 302 with values of the reference acceleration error, and a y-axis 304 with values of the reference jerk error. Multiple zones 306 - 322 are distributed around an origin of the coordinate system 300. The multiple zones 306 -322 are bordering on each other and are comprising, respectively, sets of values for the reference acceleration error and the reference jerk error.

[0143] If the current acceleration error 230 and the jerk error 232 have values within one of the zones (herein also called "active zone") out of the multiple zones 306 - 322 (corresponding to Zi -ZN), the matrix Pi is determined depending on the active zone. The multiple zones 306 - 322 are each associated with a different matrix Pi, thus leading to a different adjustment of the proportional gain 236 and the derivative gain 240 depending on the respective active zone.

[0144] With reference to Fig. 3 and Fig. 4, a scenario of an update of the proportional gain 236 and the derivative gain 240 is explained.

[0145] Fig. 4 shows a second coordinate system 400. The second coordinate system 400 has an x-axis 402 with values for the time t, and a y-axis 404 with values of the current vehicle acceleration 204. The current vehicle acceleration 204 is, for example, measured as previously described, by the IMU at discrete time steps, and the time steps are interpolated to receive a graph of the vehicle acceleration 406. Additionally, a reference graph 408 (dashed line) of the reference vehicle acceleration 224 is shown in the second coordinate system 400.

[0146] If an acceleration request 208 is provided at a time step t1 by the front camera 106, the reference unit 214 determines the reference vehicle acceleration 224 as an ideal acceleration the vehicle 100 shall have. As seen in Fig. 4, the current vehicle acceleration 204 (see graph 406) at the time step t1 deviates from the reference graph 408: In the shown example, the graph of the vehicle acceleration 406 is above the reference graph 408, meaning the current vehicle acceleration 204 is higher compared to the reference vehicle acceleration 224. This leads to a positive acceleration error 230 determined by the comparing unit 216, and potentially to an unsafe behavior of the vehicle 100 (vehicle speeding up more than it should). Thus, the proportional gain 236 and the derivative gain 240 are adjusted by the adjustment unit 218 depending on the update value of the active zone out of the multiple zones 306 - 322. For example, the acceleration error 230 may belong to the zone 308 (thus the active zone), wherein the matrix P3o8 is therefore chosen to update the proportional gain 236 and the derivative gain 240. The so updated controller 210 will generate the control signal 244, which compensates the acceleration error 230 fast and may lead to an undershoot, meaning that at a second time step t2, the graph of the vehicle acceleration 406 is now underneath the reference graph 408. Thus, the comparing unit 216 determines a negative acceleration error 230, which may represent to a safer behavior of the vehicle 100.

[0147] The acceleration error may at the second time step t2 be in the zone 312 in Fig. 3 (which is then the active zone), having the matrix P312. Thus at the second time step t2, the proportional gain 236 and the derivative gain 240 are adjusted differently, compared to the first time step t1, using the adjustment unit 218. This may result at time step t2 in the controller 210 generating the control signal 244 with a slower adaption of the current vehicle acceleration 204 to the reference vehicle acceleration 224 compared to the first time step t1.

[0148] At a third time step t3, the graph of the vehicle acceleration 406 may remain underneath the reference graph 408 and the resulting acceleration error 230 is compensated by the controller 210 more slowly compared to the first time step t1 and the second time step t2. Therefore, due to the acceleration error 230 at the third time step t3, which is now, for example, in the zone 306, the matrix P3oe is used by the adjustment unit 218 to adjust the proportional gain 236 and the derivative gain 240. The controller 210 therefore generates the control signal 244 in a way, wherein the graph of the vehicle acceleration 406 remains underneath the reference graph 408 at further time steps, thus meaning the comparing unit 216 keeps determining a negative acceleration error 230. This may represent a safe behavior of the vehicle 100.

[0149] The transition between the discrete time step t1, t1, t2, and t3, from one out of the multiple zones 306 - 322 to another zone 306 - 322 is achieved by using fuzzy logic, leading to a continuous transition between individual zones, for example, from the zone 308 to the zone 312. The transit between the zones is therefore achieved by the function:

[0150]

[0151] wherein

[0152] I is the output of a weighted summation of the transition zones 306 - 322; and

[0153] Hi (e) is a membership function representing how strongly the acceleration error 230 belongs to the zones 306 - 322, (e) may have a value between 0 and 1.

[0154] For example, for an acceleration error 230 transitioning from zone 308 to zone 312, I may be determined as follows:

[0155] I = 0.3 · Z₃₀₈ + 0.7 · Z₃₁₂,

[0156] The matrix P is then determined depending on I.

[0157] In the above-described example it is described that the proportional gain 236 and the derivative gain 240 are adjusted over multiple time step t1 - t3 to control the vehicle 100 in way, wherein the vehicle 100 shall rather brake more compared to the reference graph 408. In a further example, when the reference graph 408 shows a positive acceleration, the proportional gain 236 and the derivative gain 240 may be adjusted to control the vehicle 100 in a way such that the actuator 110 acts on the drive train 202 to enhance a behavior of less accelerating compared to the reference graph 408.

[0158] Fig. 5 shows a third coordinate system 500, comprising a y-axis 502 showing the current vehicle acceleration 204 and an x-axis 504 showing the time. A first graph 506, a second graph 508, a third graph 510 and the acceleration request 208 are drawn within the third coordinate system 500. The third graph 510 represents a controller 210, being adjusted by the adjustment unit 216 in the above-described way. The first graph 506 and the second graph 508 are related to controllers 210’ and 210”, which represent an update of the proportional gain 236 and the derivative gain 240 as known in the state of the art. As shown, the graph 510 shows an improved transient behavior as it brakes faster, improving driving safety. Fig. 6 shows method step S600 and S601 of a method according to an embodiment.

[0159] The method steps S600 and S601 may be understood as instructions of a computer pro-gram, which, when carried out by, e.g. the ECU 104, causes the ECU 104 to perform the method steps S600 and S601.

[0160] In the step S600, the current vehicle acceleration 204 is compared to the reference vehicle acceleration 224 to determine an acceleration error 230, and a current vehicle jerk 222 to a reference vehicle jerk 226 to determine a jerk error 232.

[0161] In the step S601, the proportional gain 236 and the derivative gain 240 are adjusted depending on the acceleration error 230 and the jerk error 232 of step S600.

[0162] Although the present invention has been described with reference to examples of embodiments, it can be modified in many ways. List of reference signs

[0163] 100 vehicle

[0164] 102 environment

[0165] 104 electronic control unit

[0166] 106 optical sensor

[0167] 108 ultrasonic sensor

[0168] 110 actuator

[0169] 200 ACC system

[0170] 202 drive train

[0171] 204 current vehicle acceleration 206 determining unit

[0172] 208 acceleration request

[0173] 210 controller

[0174] 210’ controller

[0175] 210” controller

[0176] 212 device

[0177] 214 reference unit

[0178] 216 comparing unit

[0179] 218 adjustment unit

[0180] 220 Kalman filter

[0181] 222 current vehicle jerk

[0182] 224 reference vehicle acceleration 226 reference vehicle jerk

[0183] 228 driver

[0184] 230 acceleration error

[0185] 232 jerk error

[0186] 234 table

[0187] 236 proportional gain

[0188] 238 integral gain 240 derivative gain

[0189] 242 offset gain

[0190] 244 control signal

[0191] 300 first coordinate system

[0192] 302 x axis

[0193] 304 y axis

[0194] 306 zone

[0195] 308 zone

[0196] 310 zone

[0197] 312 zone

[0198] 314 zone

[0199] 316 zone

[0200] 318 zone

[0201] 320 zone

[0202] 322 zone

[0203] 400 second coordinate system

[0204] 402 x axis

[0205] 404 y axis

[0206] 406 graph of the vehicle acceleration 408 reference graph

[0207] 500 third coordinate system

[0208] 502 y axis

[0209] 504 x axis

[0210] 506 first graph

[0211] 508 second graph

[0212] 510 third graph

[0213] S600 method step

[0214] S601 method step

[0215] t1 first time step t2 second time step t3 third time step

Claims

1. PATENT CLAIMS1. A method for adjusting a controller (210) in a vehicle (100), the controller (210) being configured to control a vehicle motion depending on at least a proportional gain (236) and a derivative gain (240), the method comprising:3.la) comparing (S600) a current vehicle acceleration (204) to a reference vehicle acceleration (224) to determine an acceleration error (230), and a current vehicle jerk (222) to a reference vehicle jerk (226) to determine a jerk error (232); and4.lb) adjusting (S601) the proportional gain (236) and the derivative gain (240) depending on the acceleration error (230) and the jerk error (232) of step 1a).

2. The method of claim 1, wherein, in step 1b), the proportional gain (236) and the derivative gain (240) are adjusted depending on a function of the acceleration error (230) and the jerk error (232), the function being defined before step 1a).

3. The method of claim 2, wherein:7.the function defines, for a first set of values (308) of the acceleration error (230) and the jerk error (232), first adjustment values, and, for a second set of values (312) of the acceleration error (230) and the jerk error (232), second adjustment values different from the first adjustment values, and8.step 1b) further comprises:9.comparing the acceleration error (230) and the jerk error (232) of step 1a) to the first set of values (308) and the second set of values (312), and10.adjusting, depending on the comparison, the proportional gain (236) and the derivative gain (240) using the first or second adjustment values.

4. The method of claim 3, wherein one or each value in the first set of values (308) is smaller than one or each value in the second set of values (312), and one or each of the first adjustment values is smaller than one or each of the second adjustment values.

5. The method of claim 3 or 4, wherein:12.the first adjustment values are constant for all values within the first set of values (308), the number of values within the first set (308) exceeding two,13.the second adjustment values are constant for all values within the second set of values (312), the number of values within the second set (312) exceeding two,14.the function defines third adjustment values for a third set of values (306), wherein the third adjustment values lie in between the first and the second adjustment values and the third set of values (306) lies in between the first and second set of values.

6. The method of claim 5, wherein the function determines the third adjustment values using many-valued logic, in particular fuzzy logic.

7. The method of the claims 2 to 6, wherein the function is determined using a stability criterion, in particular using a Lyapunov equation.

8. The method of one of the preceding claims, wherein the adjustment of the proportional gain (236) and the derivative gain (240) in step 1b) is determined as follows:

21. 23.wherein:24.K is a vector representing the proportional gain (236) and the derivative gain (240);27.wherein eais the acceleration error (230) and e, is the jerk error (232)28. 30.and t is the time;31.B =, wherein B determines how the current vehicle acceleration (204) and the current vehicle jerk (222) influence the vehicle motion;32. t ® matrix Pi is positive definite, and pi,n, Pi 2, and Pi,22 are33. 35.values which compensate the acceleration error (230) and the jerk error (232);36.a vector comprising the acceleration error (230) and the jerk error (232); and37.

38. Zi refers to the ithset of values of a reference acceleration error and a reference jerk error, each set I being associated with a different matrix Pi, wherein i ranges from 1 - N, with N > 1.

9. The method of one of the preceding claims, wherein, in step 1b), the proportional gain (236) and the derivative gain (240) are adjusted such that,40.when the reference vehicle acceleration (224) is negative, the current vehicle acceleration (204) stays or becomes more negative than the reference vehicle acceleration (224), and41.when the reference vehicle acceleration (224) is positive, the current vehicle acceleration (204) stays or becomes less positive than the reference vehicle acceleration (224).

10. A computer program product, comprising instructions which, when carried out by a control device (104) of the vehicle (100), causes the control device (104) to perform the method of one of claims 1 to 9.

11. A system (200), in particular an ACC system, comprising44.a controller (210) in a vehicle (100), the controller (210) being configured to control a vehicle motion depending on at least a proportional gain (236) and a derivative gain (240); and45.a device (212) including:46.a comparing unit (216) for comparing a current vehicle acceleration (204) to a reference vehicle acceleration (224) to determine an acceleration error (230), and a current vehicle jerk (222) to a reference vehicle jerk (226) to determine a jerk error (232),47.an adjustment unit (218) for adjusting the proportional gain (236) and the derivative gain (240) depending on the acceleration error (230) and the jerk error (232).

12. The system (200) of claim 11, wherein the adjustment unit (218) is configured to adjust the proportional gain (236) and the derivative gain (240) depending on a function of the acceleration error (230) and the jerk error (232), the function being stored on a storage unit (234) of the device (212).

13. A vehicle (1001 ) comprising the system (200) of claim 11 or 12.

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