Method and device for managing the operation of a driving assistance system of a motor vehicle based on the estimated mass of the vehicle

Abstract

The invention relates to a method for managing the operation of a driving assistance system (10) of a motor vehicle (1) which controls at least one chassis actuator (20) of the vehicle. The invention also relates to a device (100) implementing such a method, as well as a motor vehicle comprising such a device. Figure for the abstract: 1

Description

Title of the invention: Method and device for managing the operation of a driving assistance system for a motor vehicle based on the estimated mass of the vehicle Technical field of the invention

[0001] The present invention relates to the field of driving assistance systems for motor vehicles. The invention relates in particular to a method for managing, by a computer device on board a motor vehicle, the operation of a driving assistance system of the vehicle which controls at least one chassis actuator of the vehicle. 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 some modern motor vehicles are equipped with a driving assistance system capable of controlling one or more chassis actuators of the vehicle, for example ESP which is capable of controlling both the operation of the braking system and the powertrain of a vehicle. Generally speaking, these systems operate using a certain number of pre-established control laws, with the aim of improving the safety and comfort of vehicles. However, some of these control laws are defined as a function of the mass of the vehicle and a value of the mass of the vehicle is thus defined at the time of design of the driving assistance system and then no longer varies. However, the mass of a vehicle is not constant because it depends in particular on the loading of the vehicle.In fact, control laws which are based on a fixed value of the mass of a vehicle, regardless of the vehicle's load, will inevitably result in the provision of unsuitable commands to the chassis actuators, and this will inevitably deteriorate vehicle safety and passenger comfort. Summary of the invention.

[0003] The invention aims to solve this problem. In particular, it aims to provide a method and a device which contribute to enabling a driving assistance system for a motor vehicle to take into account the variability of the mass of the vehicle. By this means, the invention aims to enable the provision of safer and more comfortable motor vehicles.

[0004] To achieve these objectives, the invention relates, according to a first aspect, to a method of managing, by a computer device on board a motor vehicle, the operation of a vehicle driving assistance system which

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[0009] controls at least one chassis actuator of the vehicle, the method comprising the steps of: i. obtain data characterizing at least one measurement of the steering angle of the front wheels of the vehicle, data characterizing at least one measurement of the longitudinal speed of the vehicle, data characterizing at least one measurement of the yaw rate of the vehicle and data characterizing at least one measurement of the lateral acceleration of the vehicle; ii. determining, based on the data obtained during step i), data characterizing an estimate of the yaw rate of the vehicle, data characterizing an estimate of the lateral acceleration of the vehicle, data characterizing an estimate of the mass of the vehicle and data characterizing an estimate of the variance of the error in estimating the mass of the vehicle; iii. determining data characterizing a first rate of convergence of the yaw rate measurement and the yaw rate estimation and data characterizing a second rate of convergence of the lateral acceleration measurement and the lateral acceleration estimation; iv. manage the operation of the driving assistance system based on the data characterizing an estimate of the mass of the vehicle when it is established that the estimate of the variance of the error in estimating the mass of the vehicle is less than a first pre-established threshold value, that said first convergence rate is greater than or equal to a second pre-established threshold value and that said second convergence rate is greater than or equal to the second threshold value. Alternatively, step ii) may be performed using an unscented Kalman filter. According to another variant, step i) can be carried out by interacting with the driver assistance system. According to yet another variant, the second threshold value may be equal to 90%. According to a second aspect, the invention relates to a device for managing the operation of a driving assistance system of a motor vehicle which controls at least one chassis actuator of the vehicle, the device comprising at least one information processing unit, comprising at least one processor, and a data storage medium configured to implement a method as described above. 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.

[0010] According to a fourth aspect, the invention relates to a medium usable in a computer on which a program as described above is recorded.

[0011] According to a fifth aspect, the invention relates to a motor vehicle which has a device as described above. Brief description of the figures

[0012] Other characteristics and advantages of the invention will appear on examining the detailed description below, and the appended drawings, in which:

[0013] [Fig-1] is a schematic illustration of a motor vehicle according to the invention;

[0014] [Fig.2] is a functional diagram of a device according to the invention;

[0015] [Fig.3] is a flowchart of the steps of a method according to the invention;

[0016] [Fig.4] are graphs illustrating the implementation of the method according to the invention;

[0017] [Fig.5] are graphs illustrating the implementation of the method according to the invention; And

[0018] [Fig.6] are graphs illustrating the implementation of the method according to the invention. Detailed description of the invention

[0019] [Fig.l] schematically illustrates a motor vehicle 1 according to the invention. This conventionally comprises a driving assistance system 10, which controls at least one chassis actuator 20 of the vehicle, for example a chassis actuator coupled to the braking system of the vehicle. Advantageously, the vehicle 1 according to the invention also comprises a device 100 for managing the operation of a driving assistance system of a motor vehicle which controls at least one chassis actuator of the vehicle within the meaning of the present invention, as described below, which implements a method for managing the operation of a driving assistance system of a motor vehicle which controls at least one chassis actuator of the vehicle within the meaning of the present invention, as described below.

[0020] When implementing the method, the device 100 according to the invention determines an estimate of the mass of the vehicle using measurements that are accessible to the vehicle's driver assistance system, namely the steering angle of the front wheels of the vehicle, the longitudinal speed of the vehicle, its yaw rate and its lateral acceleration. These measurements made in real time are used to feed an unscented Kalman filter, which produces an estimate of the lateral acceleration of the vehicle, an estimate of its yaw rate, an estimate of its mass and an estimate of the variance of the error in estimating the mass of the vehicle. Then, after having verified the convergence between the measurements of the lateral acceleration and the yaw rate and the corresponding estimates produced by means of the filter, the device 100 manages the operation of the driving assistance system based on the estimation of the mass of the vehicle. This allows the driving assistance system 10 of the vehicle 1 according to the invention to take into account the variability of the mass of the vehicle 1, and thus offers the possibility to the driving assistance system 10 of the vehicle 1 according to the invention to provide more precise commands to the chassis actuator 20 of the vehicle 1.

[0021] The device 100 for managing the operation of a driving assistance system of a motor vehicle which controls at least one chassis actuator of the vehicle according to the invention is illustrated in [Fig.2]. It is fundamentally 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 the execution of the steps of the method according to the invention described later, and an input and output interface 103 allowing the reception and transmission of data.

[0022] 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 (e.g. CAN, Ethernet) - shown in [Fig.l] by the two-way arrows - with the driving assistance system 10 of the vehicle. Alternatively, the device 100 according to the invention is an integral part of a computer of the driving assistance system 10 of the vehicle 1.

[0023] According to the invention, all the elements described above contribute to enabling the implementation, on board a motor vehicle, of a method for managing the operation of a vehicle driving assistance system which controls at least one chassis actuator of the vehicle, as described below in connection with [Fig.3]-6.

[0024] 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 at least one measurement of the steering angle of the front wheels of the vehicle j, data characterizing at least one measurement of the longitudinal speed of the vehicle (yj, data characterizing at least one measurement of the yaw rate of the vehicle (¢), and data characterizing at least one measurement of the lateral acceleration of the vehicle (yv or a^)- Indeed, the equations of the dynamics of a vehicle show that the yaw rate, the lateral acceleration and the longitudinal speed of the vehicle depend on the mass of the vehicle (m), in particular the lateral acceleration and the yaw acceleration (¢) are such that:

[0025] y _ rv ULW11 +

[0026] #= yv , + + ■. i \ ; 7 . -

[0027] And to obtain the measurements of the aforementioned parameters, the device 100 according to the invention interacts with the driving assistance system 10, which, conventionally, is able to determine these measurements, for example by interacting with a steering angle sensor, an accelerometer and a yaw rate sensor on board the vehicle 1. In other words, the device 100 according to the invention advantageously initiates the implementation of the method according to the invention by obtaining measurements of four common parameters which are conventionally determined by the driving assistance systems of all modern vehicles.

[0028] Then, according to a second step 302 of the method according to the invention, the device 100 according to the invention determines, as a function of the data obtained during the first step, data characterizing an estimate of the yaw rate of the vehicle (^, data characterizing an estimate of the lateral acceleration of the vehicle (ày), data characterizing an estimate of the mass of the vehicle (m) and data characterizing an estimate of the variance of the error in estimating the mass of the vehicle

[0029] To determine these data, the device 100 according to the invention advantageously feeds an unscented Kalman filter, which determines the aforementioned estimates from the fundamental equations of the vehicle dynamics. This estimator is parameterized so that the two reconstructed estimated quantities and ay converge quickly towards their respective measurement V' and ay. This convergence is achieved when the mass of the vehicle estimated by means of the unscented Kalman filter converges towards the actual mass of the vehicle. This way of proceeding brings several advantages. Indeed, unlike a packet identification method, the nonlinear estimator which plays the role of recursive identification updates the estimated mass as soon as new measurements are available, and this, without it being necessary to store input / output data packets which consume memory space on a computer.Furthermore, the ease of implementation of the Unscented Kalman Filter (UKF) and its robustness allow a better approximation of nonlinearities compared to an Extended Kalman Filter (EKF), because, unlike an Extended Kalman Filter, the Unscented Kalman Filter does not use the calculation of a Jacobian matrix (a linearization of the system at an operating point) and this thus makes its implementation on real-time targets often less expensive in computational resources.

[0030] Then, according to a third step 303 of the method according to the invention, the device 100 according to the invention determines data characterizing a first rate of convergence of the measurement of the yaw rate and of the estimation of the yaw rate and data characterizing a second rate of convergence of the measurement of the acceleration lateral acceleration and the estimation of the lateral acceleration. To do this, the device 100 according to the invention calculates the difference between the measurement and the corresponding estimation, which it weights according to the difference between the value measured at an instant and the average of the measurements carried out previously. Thus, at the end of this third step of the method, the device 100 according to the invention has advantageously determined the effectiveness of the Kalman filter for estimating the yaw rate and the lateral acceleration of the vehicle. And, as already mentioned above, the convergence between the estimations of these parameters and their corresponding measurements implies the convergence of the estimation of the mass and the actual mass of the vehicle.

[0031] Finally, according to a fourth step 304 of the method according to the invention, the device 100 according to the invention manages the operation of the driving assistance system as a function of the data characterizing an estimation of the mass of the vehicle as soon as it establishes that the estimation of the variance of the error in estimating the mass of the vehicle is less than a first pre-established threshold value, that the first convergence rate is greater than or equal to a second pre-established threshold value, for example equal to 90%, and that the second convergence rate is greater than or equal to the second threshold value, for example equal to 90%. In other words, when it establishes the convergence of the estimations of the lateral acceleration and the yaw rate with the measurements of these parameters and that the variance of the error in estimating the mass is low, the device 100 according to the invention considers that the estimation of the mass of the vehicle can be used by the driving assistance system 10.It then proceeds by transmitting to the latter data characterizing a command to use the estimated mass of the vehicle, and the driving assistance system 10 executes the command upon receipt of the data.

[0032] [Fig.4] illustrates by means of graphs the temporal evolution of the measurements of the parameters which feed the unscented Kalman filter. We see, from top to bottom, the longitudinal speed of the vehicle, the steering angle of the front wheels, the yaw rate of the vehicle and the transverse acceleration of the vehicle. [Fig.5] illustrates the results of the estimator using the measurements illustrated by the graphs of [Fig.4]. We see, from top to bottom, the estimated and measured transverse acceleration, the estimated and measured yaw rate, the estimated total mass, the actual total mass of the vehicle, the gauge + / - 5% of the actual total mass of the vehicle and, at the very bottom, the estimate of the variance of the mass estimation error. This variance estimate is repeated in [Fig.6] with a threshold making it possible to know when the estimated mass is used.

[0033] Thus, thanks to the method and the device according to the invention described above, a solution is provided to enable a driving assistance system of a motor vehicle to be able to take into account the variability of the mass of the vehicle. Thanks to these means, the invention thus contributes to the provision of safer motor vehicles. and more comfortable.

Claims

1.

2.

3. Claims Method for managing, by a computer device (100) on board a motor vehicle (1), the operation of a driving assistance system (10) of the vehicle which controls at least one chassis actuator (20) of the vehicle, characterized in that the method comprises the steps of: i. obtain data characterizing at least one measurement of the steering angle of the front wheels of the vehicle, data characterizing at least one measurement of the longitudinal speed of the vehicle, data characterizing at least one measurement of the yaw rate of the vehicle and data characterizing at least one measurement of the lateral acceleration of the vehicle; ii. determining, based on the data obtained during step i), data characterizing an estimate of the yaw rate of the vehicle, data characterizing an estimate of the lateral acceleration of the vehicle, data characterizing an estimate of the mass of the vehicle and data characterizing an estimate of the variance of the error in estimating the mass of the vehicle; iii. determining data characterizing a first rate of convergence of the yaw rate measurement and the yaw rate estimation and data characterizing a second rate of convergence of the lateral acceleration measurement and the lateral acceleration estimation; iv. manage the operation of the driving assistance system based on the data characterizing an estimate of the mass of the vehicle when it is established that the estimate of the variance of the error in estimating the mass of the vehicle is less than a first pre-established threshold value, that said first convergence rate is greater than or equal to a second pre-established threshold value and that said second convergence rate is greater than or equal to the second threshold value. Method according to claim 1, characterized in that step ii) is carried out using a fragrance-free Kalman filter. Method according to one of the preceding claims, characterized in that that step i) is carried out by interacting with the driver assistance system.

4. Method according to one of the preceding claims, characterized in that the second threshold value is equal to 90%.

5. Device (100) for managing the operation of a driving assistance system (10) of a motor vehicle (1) which controls at least one chassis actuator (20) of the vehicle, 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.

6. A computer program comprising program code instructions for executing the steps of a method according to any one of claims 1 to 4 when said program is executed by at least one processor.

7. Support usable in a computer, characterized in that a program according to claim 6 is recorded therein.

8. Motor vehicle, characterized in that it incorporates a device according to claim 5.

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