Method and device for controlling first and second actuators of a motor vehicle via dynamic frequency-band allocation

Abstract

The invention relates to a method for controlling a first actuator (10) and a second actuator (11) of a motor vehicle (1), said actuators influencing a common parameter of the dynamics of the vehicle depending on an action performed on a member for controlling guidance of the vehicle. The invention also relates to a device (100) implementing such a method, and to a motor vehicle comprising such a device.

Description

DESCRIPTION TITLE: Method and device for controlling a first and a second actuator of a motor vehicle by dynamic allocation by frequency band Technical field of the invention

[0001] The present invention relates to the field of controlling actuators in motor vehicles. The invention relates in particular to a method for controlling, by a computer device on board a motor vehicle, a first actuator and a second actuator of the vehicle, said actuators influencing a common parameter of the dynamics of the vehicle as a function of an action carried out on a vehicle guidance control member. The invention also relates to a device implementing such a method. The invention applies to motor vehicles such as land motor vehicles, in particular cars. State of the prior art

[0002] It is known that, in modern motor vehicles, there is now a decoupling between the driver and the various vehicle actuators in the sense that the traditional mechanical connections between the vehicle guidance control members and the actuators have been replaced by electronic and / or computer devices and on-board signal and / or data transmission networks that ensure the routing of commands to the actuators determined according to the actions that are performed on the vehicle guidance control members. It is also known that these certain actions performed by a driver on certain vehicle guidance control members, in particular the steering wheel, involve in certain cases the simultaneous use of several actuators. Indeed, having several actuators work together to perform an action makes it possible to achieve greater efficiency and increased safety.For example, the combination of braking. differential and the steering of the front or rear wheels allows for greater efficiency in carrying out obstacle avoidance maneuvers. However, the greater the number of actuators involved, the more complex and costly the distribution of commands between the different actuators becomes in terms of computing resource requirements. Summary of the invention

[0003] The invention aims to solve this problem. In particular, the invention aims to provide a method and a device that make it possible to distribute a command between two actuators of a vehicle in a manner that is more economical in terms of the computing resources required for this. By this means, the invention aims to enable the provision of more efficient and safer motor vehicles.

[0004] To achieve these objectives, the invention relates, according to a first aspect, to a method of controlling, by a computer device on board a motor vehicle, a first actuator and a second actuator of the vehicle, said actuators influencing a common parameter of the dynamics of the vehicle as a function of an action carried out on a vehicle guidance control member, the method comprising the steps of: i) obtaining data characterizing an overall command generated as a function of said action;ii) performing a processing of the data characterizing a global command in order to obtain data characterizing a command to be carried out by the first actuator and data characterizing a command to be carried out by the second actuator, said processing being carried out by means of a first low-pass filter to obtain the data characterizing a command to be carried out by the first actuator and a second high-pass filter to obtain the data characterizing a command to be carried out by the second actuator; and iii) causing the operation of the first actuator according to the data characterizing a command to be carried out by the first actuator and the; operation of the second actuator based on data characterizing a command to be carried out by the second actuator.

[0005] Alternatively, the first filter and the second filter may have the same cutoff frequency.

[0006] According to another variant, the cut-off frequency can be determined on the basis of a modeling of the operation of the first actuator previously established by supervised learning.

[0007] According to yet another variant, said modeling can be established using a first-order invariant linear model.

[0008] According to yet another variant, said modeling can be established by discretizing said model.

[0009] According to yet another variant, said modeling can be established by minimizing a cost function in order to obtain at least one value of the gain and at least one value of a response time constant of the first actuator.

[0010] According to yet another variant, the first actuator can control the steering angle of each of the front and rear wheels of the vehicle while the second actuator can control the movement of each of the brake calipers of the vehicle.

[0011] According to a second aspect, the invention relates to a device for controlling a first actuator and a second actuator of a motor vehicle, said actuators influencing a common parameter of the dynamics of the vehicle as a function of an action carried out on a vehicle guidance control member, the device comprising at least one processing unit information, comprising at least one processor, and a data storage medium configured to implement a method as described above.

[0012] According to a third aspect, the invention relates to a computer program comprising program code instructions for executing the steps of a method as described above when said program is executed by at least one processor.

[0013] According to a fourth aspect, the invention relates to a motor vehicle which carries a device as described above. Brief description of the figures

[0014] Other characteristics and advantages of the invention will appear on examining the detailed description below, and the appended drawings, in which:

[0015] [Fig. 1] is a schematic illustration of a motor vehicle according to the invention;

[0016] [Fig. 2] is a functional diagram of a device according to the invention;

[0017] [Fig. 3] is a flowchart of the steps of a method according to the invention;

[0018] [Fig. 4] illustrates the implementation of at least one step of the method according to the invention;

[0019] [Fig. 5] illustrates the implementation of at least one step of the method according to the invention;

[0020] [Fig. 6] illustrates the implementation of at least one step of the method according to the invention;

[0021] [Fig. 7] illustrates the implementation of at least one step of the method according to the invention;

[0022] [Fig. 8] illustrates the implementation of at least one step of the method according to the invention;

[0023] [Fig. 9] illustrates the implementation of at least one step of the method according to the invention;

[0024] [Fig. 10] illustrates the implementation of at least one step of the method according to the invention;

[0025] [Fig. 11] illustrates the implementation of at least one step of the method according to the invention; and

[0026] [Fig. 12] illustrates the implementation of at least one step of the method according to the invention. Detailed description of the invention

[0027] Figure 1 schematically illustrates a motor vehicle 1 according to the invention. This comprises a first actuator 10 and a second actuator 11 which, depending on an action performed by the driver of the vehicle on a vehicle guidance control member, for example its steering wheel, jointly influence at least one parameter of the dynamics of the vehicle, for example its yaw rate when the first actuator controls the steering angle of each of the front and rear wheels of the vehicle while the second actuator controls the movement of each of the brake calipers of the vehicle.Advantageously, the vehicle 1 according to the invention also comprises a device 100 for controlling a first actuator and a second actuator of a motor vehicle within the meaning of the present invention, as described below, which implements a method for controlling a first actuator and a second actuator of a motor vehicle within the meaning of the present invention, as described below.

[0028] When implementing the method, the device 100 according to the invention conventionally obtains an overall command to be carried out by means of the two actuators 10, 11 of the vehicle 1, an overall command which is conventionally determined by a control supply apparatus 12 which conventionally establishes commands, preferably in the form of signals, as a function of the actions carried out by the driver on the control members. guidance of the vehicle 1. Advantageously, the device 100 according to the invention then proceeds by distributing the overall command between the first and second actuators by carrying out a frequency band filtering of the overall command. Thus, the device 100 according to the invention advantageously allows the distribution of an overall command between the actuators 10, 11 of the vehicle 1 while minimizing the computing resource requirements necessary for this.

[0029] The device 100 for controlling a first actuator and a second actuator of a motor vehicle according to the invention is illustrated in Figure 2. It is basically a computer device which comprises at least one information processing unit 101, comprising one or more processors, a data storage medium 102, on which is recorded in particular a program which comprises program code instructions for executing the steps of the method according to the invention described later, and an input and output interface 103 allowing the reception and transmission of signals and / or data. In addition, the device 100 according to the invention advantageously comprises a first low-pass filter 104 and a second high-pass filter 105, which, as will be seen below, share the same cut-off frequency.Preferably, the device 100 according to the invention is hosted on an independent computer and it interacts via its input and output interface 103 and by means of a wired communication network of the vehicle (eg CAN, Ethernet) – shown in Figure 1 by the arrows – with the first actuator 10, the second actuator 11 and the control supply apparatus 12 of the vehicle 1.

[0030] According to the invention, all the elements described above contribute to enabling the implementation, on board a motor vehicle, of a method for controlling a first actuator and a second actuator of a motor vehicle, said actuators influencing a common parameter of the dynamics of the vehicle as a function of an action carried out on a vehicle guidance control member. The method according to the invention is described below in connection with Figures 3-12.

[0031] Figure 3 illustrates by means of a flowchart the steps of the method according to the invention. According to a first step 301 of the method according to the invention, the device 100 according to the invention obtains data characterizing a global command generated as a function of the action performed on a vehicle guidance control member. To do this, the device 100 according to the invention interacts with the control supply apparatus 12, which conventionally generates such data. To enable this, the control supply apparatus 12 comprises, for example, the same components as an electric power steering system, namely at least one sensor capable of measuring the torque applied by the driver to the steering wheel of the vehicle 1 and a computer which generates data characterizing a global command to be carried out by the actuators as a function of the measurement of the torque applied.

[0032] Then, according to a second step 302 of the method according to the invention, the device 100 according to the invention performs a processing of the data characterizing a global command obtained during the previous step in order to obtain data characterizing a command to be carried out by the first actuator 10 and data characterizing a command to be carried out by the second actuator 11. Advantageously, this processing is carried out by means of the first filter 104 to obtain the data characterizing a command to be carried out by the first actuator 10 and of the second filter 105 to obtain the data characterizing a command to be carried out by the second actuator 11. According to the invention, the first low-pass filter 104 and the second high-pass filter 105 have the same cut-off frequency, which is determined on the basis of a modeling of the operation of the first actuator previously established by supervised learning.This learning will be explained below, considering in particular that the first actuator controls the four steering wheels of the vehicle 1 according to the invention.

[0033] During training, the operation of the first actuator 10 is modeled from input and output signals as follows. A first-order invariant linear model is used for best approximate the operation of the first actuator 10. Such a model is illustrated in Figure 4, where Kp is the actuator gain and ^ ^ its response time constant. This model is transformed into a state representation in order to construct a modeling cost function. Thus, by denoting u, y and x, respectively the input signal, output signal and the state variable of the model, we have: ^

[0034] ^ = ^ ^^^ ^ ∗^ ^ and y=x

[0035] The resulting differential equation is therefore:

[0036] ^ ^ 1 + ^ ^ ^ ^ = ^ ^ ^ ^ ^

[0037] ^ + ^ ^̇ = ^ ^ ^ ^ ^ , or ^̇=− ^ ^ ^ + ^ ^ ^

[0038] From these equations, we can obtain the matrices of the state representation of the continuous model, namely:

[0041] Since the data used for modeling are composed of discrete data acquired at a period dt=10ms, it is then necessary to discretize the state representation. We know that the first actuator operates mainly in the base and medium frequencies. The first-order Euler discretization is therefore appropriate to transform the continuous model of the actuator into a discrete model. Thus, by grouping the model parameters in a vector ^ = [^ ^ ^ ^ ], we obtain the state representation of the discrete model:

[0043] with ^ ^ (^) = 1 + ^ ∗ ^^ ; ^ ^ (^) = ^ ∗ ^^ ^^ ^ ^ = ^

[0044] Then, we proceed by establishing a cost function to minimize to obtain the parameter vector ^ = [^ ^ ^ ^ ], namely:

[0048] The minimization of the cost function described in the above equations with the pem method (Prediction Error Method) allows to obtain the numerical values ​​of the parameter vector θ, which are indicated in the table illustrated in Figure 5. Thus, the identified model allows to model the operation of the first actuator with a coherence rate of 96%, as shown in Figure 6, in which the upper graph shows the angular query corresponding to the action performed on the vehicle guidance member and the lower graph shows, in solid line, the operation of the first actuator 10 and, in dotted line, the modeling of the operation of the actuator obtained as explained above. In addition, the frequency analysis of the actuator allows to know that the first actuator 10 is more efficient in low frequencies. The bandwidth or cutoff frequency at -3dB is 3.2Hz, as shown in Figure 7.

[0049] The bandwidth of the first actuator 10 is thus identified at 3.2 Hz and this knowledge is then used to distribute the overall command to the two actuators. Thus, the first filter 104 supplying the first actuator 10 is chosen to allow the low frequency components of the global control, and, as already mentioned above, it is therefore a low-pass filter having as its cut-off frequency the bandwidth of the first actuator 10. The remainder of the global control, that is to say the frequency components higher than the cut-off frequency of the first actuator 10 will be directed towards the second actuator 11. And to ensure the full transmission of the global control, it is therefore appropriate that the second filter 105 is a high-pass filter which has as its cut-off frequency the bandwidth of the first actuator 10.

[0050] Thus, by designating ^ ^^the cutoff frequency of the first filter 104 and by ^ ^^ the cut-off frequency of the second filter 105, the condition of integral transmission of the global control to the first actuator 10 and to the second actuator 11 is verified for ^ ^^ = ^ ^^ . The first filter 104 and the second filter 105 can be made in different ways. The table illustrated in Figure 8 shows a simple way of making them.

[0051] Note that the cutoff frequency ^ ^^ is related to the time constant ^ ^ of the first actuator by: ^

[0052] ^ ^^ = ^^^ ^

[0053] Thus, on the basis of this modeling, the characteristics of the first filter 104 and of the second filter 105 are obtained, which are used to obtain the data characterizing a command to be carried out by the first actuator 10 and the data characterizing a command to be carried out by the second actuator 11.

[0054] Then, according to a third step 303 of the method according to the invention, the device 100 according to the invention causes the operation of the first actuator 10 as a function of the data characterizing a command to be carried out by the first actuator and the operation of the second actuator 11 as a function of the data characterizing a command to be carried out by the second actuator 11. In other words, a part of the global command is allocated to the first actuator 10 via the first filter 104 and the rest of the global command is allocated to the second actuator 11 via the second filter 105. This allocation by frequency band is illustrated in Figure 9, which illustrates the global command on the top graph, the part of the global command allocated to the first actuator 10 via the first filter 104 on the middle graph and the part of the global command allocated to the second actuator 11 via the second filter 105 on the bottom graph.

[0055] As we understand, the requirement ^ ^^ = ^ ^^allows full transmission of the global command, as seen in Figure 10 which illustrates this with a consistency rate of 100% between the global command, in solid line, and the sum of the output allocations of filters 104 and 105 in dotted lines.

[0056] Thus, thanks to this allocation by frequency band, it is possible to continuously converge, for example, the vehicle's yaw rate response towards the reference yaw rate. This is illustrated in Figure 11, in which we see the yaw rate reference in solid lines which is superimposed on the vehicle's response in dotted lines: the vehicle follows the target perfectly. Figure 12 illustrates the instruction of each actuator: the driver's action in terms of steering wheel angle on the top left graph, the yaw moment allocated to the first actuator 10 converted into the rear axle steering angle on the top right graph and the yaw moment allocated to the second actuator 11 of the brake calipers on the four graphs on the right.

[0057] Unlike known control devices which proceed by online optimization or which generate the instructions to the different actuators by an optimization calculation (explicit or implicit), the device 100 according to the invention proceeds by dynamic allocation by frequency band, which offers the advantage of reducing the requirements in computing resources because it does not carry out any online optimization calculation nor any constrained optimization. In addition, dynamic allocation by frequency band reduces algorithmic complexity by combining setpoint allocation and actuator dynamics in a single filter. It also solves the problem of choosing a weighting coefficient, which is often arbitrary (e.g., 50 / 50, 10 / 90, etc.). Using actuator performance gives physical meaning to the allocation, and only one tuning parameter is required: the time constant of the first actuator in the case of 2 actuators (otherwise, n-1 parameters for n actuators).

[0058] Therefore, the method and device according to the invention described above provide a solution for distributing a command between two actuators of a vehicle in a manner that is more economical in terms of the computing resources required for this. By this means, the invention enables the provision of more efficient and safer motor vehicles.

Claims

CLAIMS:

1. Method for controlling, by a computer device (100) on board a motor vehicle (1), a first actuator (10) and a second actuator (11) of the vehicle, said actuators influencing a common parameter of the dynamics of the vehicle as a function of an action carried out on a vehicle guidance control member, characterized in that the method comprises the steps of: i) obtaining data characterizing a global command generated as a function of said action;ii) performing a processing of the data characterizing a global command in order to obtain data characterizing a command to be carried out by the first actuator (10) and data characterizing a command to be carried out by the second actuator (11), said processing being carried out by means of a first low-pass filter (104) to obtain the data characterizing a command to be carried out by the first actuator and a second high-pass filter (105) to obtain the data characterizing a command to be carried out by the second actuator;iii) causing the operation of the first actuator (10) as a function of the data characterizing a command to be carried out by the first actuator and the operation of the second actuator (11) as a function of the data characterizing a command to be carried out by the second actuator.

2. Method according to claim 1, characterized in that the first filter (104) and the second filter (105) have the same cut-off frequency.

3. Method according to claim 2, characterized in that the cut-off frequency is determined on the basis of a modeling of the operation of the first actuator previously established by supervised learning.; 4. Method according to claim 3, characterized in that said modeling is established using a first-order invariant linear model.

5. Method according to claim 4, characterized in that said modeling is established by discretizing said model.

6. Method according to one of claims 3-5, characterized in that said modeling is established by minimizing a cost function in order to obtain at least one value of the gain and at least one value of a response time constant of the first actuator (10).

7. Method according to one of the preceding claims, characterized in that the first actuator controls the steering angle of each of the front and rear wheels of the vehicle while the second actuator controls the movement of each of the brake calipers of the vehicle. 8.Device (100) for controlling a first actuator (10) and a second actuator (11) of a motor vehicle (1), said actuators influencing a common parameter of the dynamics of the vehicle as a function of an action carried out on a vehicle guidance control member, characterized in that the device comprises at least one information processing unit (101), comprising at least one processor, and a data storage medium (102) configured to implement a method according to any one of the preceding claims.

9. Computer program comprising program code instructions for executing the steps of a method according to any one of claims 1 to 7 when said program is executed by at least one processor.

10. Motor vehicle (1), characterized in that it carries a device (100) according to claim 8.

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