阅读说明：本技术 用于探测位于方向盘上的手的方法 (Method for detecting a hand on a steering wheel ) 是由 E·法施扎德 A·路恩根 于 2018-05-08 设计创作，主要内容包括：本发明涉及一种用于探测机动车的驾驶员的位于方向盘(14)上的手的方法。借助于数学模型对机动车的转向系统(10)的至少一个部分建模。此外,确定转向系统的扭力杆(17)的下端部和/或上端部的转动角。借助于测量装置(18)确定作用在扭力杆(17)上的转矩,并且借助于卡尔曼滤波器估计作用在方向盘(14)上的总转矩以及方向盘(14)的转动角加速度。所估计的、作用在所述方向盘(14)上的总转矩和所估计的转动角加速度用于确定方向盘(14)的转动惯量。方向盘(14)的所确定的转动惯量和方向盘(14)的转动惯量的预先确定的额定值用于确定驾驶员的手是否位于方向盘(14)上。(The invention relates to a method for detecting a hand of a driver of a motor vehicle on a steering wheel (14). At least one part of a steering system (10) of a motor vehicle is modeled by means of a mathematical model. Furthermore, the rotation angle of the lower end and/or the upper end of a torsion bar (17) of the steering system is determined. The torque acting on the torsion bar (17) is determined by means of a measuring device (18), and the total torque acting on the steering wheel (14) and the rotational angular acceleration of the steering wheel (14) are estimated by means of a Kalman filter. The estimated total torque acting on the steering wheel (14) and the estimated rotational angular acceleration are used to determine the moment of inertia of the steering wheel (14). The determined moment of inertia of the steering wheel (14) and predetermined nominal values of the moment of inertia of the steering wheel (14) are used to determine whether a driver's hand is on the steering wheel (14).)

1. Method for detecting a hand of a driver of a motor vehicle, in particular a motor vehicle having an electromechanically assisted steering system, on a steering wheel (14), characterized in that the method comprises the following steps:

Modeling at least one part of a steering system (10) of the motor vehicle by means of a mathematical model,

Determining a rotation angle of a lower end portion and/or an upper end portion of a torsion bar (17) of the steering system (10),

Determining the torque acting on the torsion bar (17) by means of a measuring device (18),

Estimating the total torque acting on the steering wheel (14) and the rotational angular acceleration of the steering wheel (14) by means of a Kalman filter,

The estimated total torque acting on the steering wheel (14) and the estimated rotational angular acceleration are used to determine the moment of inertia of the steering wheel (14), an

The determined moment of inertia of the steering wheel (14) and a predetermined setpoint value of the moment of inertia of the steering wheel (14) are used to determine whether the driver's hands are located on the steering wheel (14).

2. Method according to claim 1, characterized in that the entire steering system (10) is modeled by means of the mathematical model.

3. Method according to claim 1, characterized in that an upper part (12) of a steering system (10) of the motor vehicle, which comprises the steering wheel (14), a steering column (16) with the torsion bar (17) and the measuring device (18), is modelled by means of the mathematical model.

4. A method according to claim 1, characterized by modelling the part of the steering device above the torsion bar (17), which part comprises the steering wheel (14), by means of the mathematical model.

5. Method according to any of the preceding claims, characterized in that an observer is designed on the basis of the mathematical model, which observer finds the required unmeasured quantities or the required quantities that cannot be measured.

6. The method according to any one of the preceding claims, characterized in that the determined moment of inertia of the steering wheel (14) and a predetermined nominal value of the moment of inertia of the steering wheel (14) are compared to determine whether the driver's hand is on the steering wheel (14).

7. The method of claim 6, wherein the moments of inertia are compared by differencing the two moments of inertia.

8. Method according to any of the preceding claims, characterized in that the state of the steering wheel (14) is modelled by means of a linear state space model.

9. A method according to any one of the preceding claims, wherein the measuring means determines the torque acting on the torsion bar (17) from the relative angle between the upper and lower ends of the torsion bar (17).

10. The method according to any one of the preceding claims, characterized in that the moment of inertia of the steering wheel (14) is determined from a differential equation describing the correlation between the moment of inertia of the steering wheel (14), the angular acceleration of the steering wheel (14) and the torque acting on the steering wheel (14).

11. Method according to one of the preceding claims, characterized in that additionally the rotation angle of the steering wheel (14) is determined, in particular measured.

12. Method according to any of the preceding claims, characterized in that the measuring device (18) measures the angle of rotation of the lower end and/or the upper end of the torsion bar (17).

13. The method according to claim 3 in combination with any one of claims 5 to 12, characterized in that the upper part (12) of the steering system (10) is modeled in the mathematical model as a body of matter (22) with a spring (24) and/or at least one damping (26).

14. The method according to claim 3 or 4 in combination with any one of claims 5 to 12, characterized in that the modeled part of the steering system (10) is modeled in the mathematical model as a mass (22).

Technical Field

The invention relates to a method for detecting a hand on a steering wheel of a driver of a motor vehicle, in particular a motor vehicle having an electromechanically assisted steering system.

Background

In motor vehicles with electromechanical steering systems, electromechanical steering aids can act on the steering system with a torque and thus assist the driver in steering or steer the motor vehicle in a defined direction. In particular, electromechanical steering aids can also steer the vehicle in a specific direction automatically, i.e. without a corresponding steering movement of the driver, for example on the basis of data from a camera or other sensors. Automatic steering of a motor vehicle is used in particular in a control system of a motor vehicle which is at least partially autonomous.

an example of such a control system is a so-called lane keeping assist system, which assists the driver in keeping a lane. However, the driver of the motor vehicle should be able to take over the complete control of the motor vehicle at any time. The driver's hands proving on the steering wheel is a reliable indicator in this respect.

In a motor vehicle that is traveling completely autonomously, the control system should automatically control the motor vehicle as long as the driver does not want to take over the control of the motor vehicle himself. This is an explicit indication that the driver is willing to take over control of the vehicle if the driver places his hands on the steering wheel. If, on the other hand, the driver takes his hand off the steering wheel, the automatic control system should take over the control of the motor vehicle.

I.e. in both cases it is necessary to be able to detect that the driver's hands are on the steering wheel. One possibility to detect the presence of a hand on the steering wheel is an additional sensor on the steering wheel. The sensor recognizes, for example by means of a capacitive measurement, whether a hand is on the steering wheel. However, additional sensors incur additional costs.

Disclosure of Invention

The object of the present invention is therefore to provide a method for detecting a hand on a steering wheel, in which additional sensors are not necessary in relation to the torque sensors and/or rotation angle sensors present in an electromechanically assisted steering system.

according to the invention, this object is achieved by a method of the type mentioned at the outset, having the following steps:

At least one part of a steering system of a motor vehicle is modeled by means of a mathematical model,

A rotation angle of a lower end portion and/or an upper end portion of a torsion bar of a steering system is determined,

The torque acting on the torsion bar is determined by means of a measuring device,

The total torque acting on the steering wheel and the angular acceleration of the rotation of the steering wheel are estimated by means of a kalman filter,

the estimated total torque acting on the steering wheel and the estimated rotational angular acceleration are used to determine the moment of inertia of the steering wheel, an

The determined moment of inertia of the steering wheel and the predetermined nominal values of the moment of inertia of the steering wheel are used to determine whether the driver's hands are on the steering wheel.

Since the determined moment of inertia of the steering wheel differs from the predetermined setpoint value when the driver's hand is located on the steering wheel, it can be ascertained whether the driver's hand is located on the steering wheel. The method according to the invention uses only sensors already present in the steering system to detect the presence of the driver's hand on the steering wheel, in particular a torque sensor which determines at least the torque acting on the torsion bar. I.e. additional sensors are not necessary, thereby saving costs.

According to one aspect of the invention, the entire steering system is modeled by means of a mathematical model. In particular, both the upper part of the steering system of the motor vehicle (which upper part comprises the steering wheel, the steering column with the torsion bar and the measuring device) and the lower part of the steering system of the motor vehicle are modeled.

According to another aspect, an upper part of a steering system of a motor vehicle (which upper part comprises a steering wheel, a steering column with a torsion bar and a measuring device) is modeled by means of a mathematical model.

On the other hand, it is provided that the part of the steering system above the torsion bar (which part includes the steering wheel) is modeled by means of a mathematical model.

Preferably, the observer is designed on the basis of a mathematical model, which determines the required unmeasured variables or the required variables which cannot be measured. The observer is understood here to mean an observer in the sense of a control technique. With the aid of the observer, the following variables can be determined: this variable is required for determining the moment of inertia of the steering wheel, but is not measured or cannot be measured. The angle of rotation of the lower end of the torsion bar can be determined, in particular measured, by an angular position sensor of an auxiliary motor of the electromechanically assisted steering system.

Preferably, the determined moment of inertia of the steering wheel is compared to a predetermined nominal value of the moment of inertia of the steering wheel to determine whether the driver's hands are on the steering wheel. In particular, when the rotational inertia differs by more than a predetermined value, it is recognized that the driver's hand is positioned on the steering wheel. The predetermined value may be selected such that the recognition error rate is 10% or less, preferably 5% or less, and more preferably 0%. In this way, it can be recognized with the desired accuracy whether the driver's hands are on the steering wheel.

Further preferably, the moments of inertia are compared by differencing two moments of inertia. In particular, when the difference between the rotational inertia and zero is greater than a predetermined value, it is recognized that the driver's hand is positioned on the steering wheel. The predetermined value may be selected such that the recognition error rate is 10% or less, preferably 5% or less, and more preferably 0%. In this way, it can be recognized with the desired accuracy whether the driver's hands are on the steering wheel.

According to one aspect of the invention, the state of the steering wheel is modeled by means of a linear state space model. In particular linear state space models form the basis for observer design. The observer is understood here to mean an observer in the sense of a control technique. With the aid of the observer, the following variables can be determined: this variable is required for determining the moment of inertia of the steering wheel, but is not measured or cannot be measured.

According to another aspect of the present invention, the measuring device determines the torque acting on the torsion bar from the relative angle between the upper and lower ends of the torsion bar. Since the torque acting on the torsion bar is inherently measured, in particular in an electromechanically assisted steering system, it is possible to use already existing sensors of the steering system. I.e. no additional components are required, thereby saving costs.

Preferably, the moment of inertia of the steering wheel is determined from a differential equation describing a correlation between the moment of inertia of the steering wheel, the rotational angular acceleration of the steering wheel, and the estimated total torque acting on the steering wheel. Since the kalman filter estimates all the variables necessary for this, the rotational inertia of the steering wheel can be determined particularly simply in this embodiment of the invention.

One aspect of the invention provides for additionally determining, in particular measuring, the angle of rotation of the steering wheel. In particular, the angle of rotation of the upper end of the torsion bar is determined or measured and considered to be equivalent to the angle of rotation of the steering wheel. In this embodiment of the invention, the angle of rotation of the steering wheel does not have to be first reconstructed by a kalman filter, but is directly available, in particular, as a measurement variable.

In particular, the measuring device measures the angle of rotation of the lower end and/or the upper end of the torsion bar. If the measuring device measures only one of the two rotation angles, the respective further rotation angle can be reconstructed from the measured rotation angle and the determined torque acting on the torsion bar. In particular, the rotation angle of the upper end portion of the torsion beam can be regarded as being equivalent to the rotation angle of the steering wheel. In this embodiment of the invention, no additional measuring device for measuring the angle of rotation is required, thereby resulting in a simpler construction of the steering system.

According to one embodiment of the invention, the upper part of the steering system is modeled in a mathematical model as a body of matter with springs and/or damping. By appropriate adjustment of the model parameters, in particular the spring constant and the damping coefficient, the upper part of the steering system can be modeled as practically as possible.

According to another embodiment of the invention, the modeled part of the steering system is modeled as a physical body in a mathematical model. This is advantageous especially when measuring the rotation angle of the upper end portion of the torsion beam. A simplified model of the upper steering system is sufficient for determining the torque acting on the steering wheel with sufficient accuracy. In this embodiment of the invention, the computational cost is reduced.

Drawings

Further advantages and features of the invention emerge from the description which follows and from the figures referred to. Shown in the drawings are:

fig. 1 shows a steering system of a motor vehicle in a perspective view;

Figure 2 shows a physical substitution model of the upper part of the steering system of figure 1;

figure 3 shows a simplified physical substitution model of the upper part of the steering system of figure 1; and

Fig. 4 shows a schematic representation of the steps of the method according to the invention.

Detailed Description

The steering system 10 of the motor vehicle shown in fig. 1 is designed as an electromechanically assisted steering system. The steering system 10 includes an upper portion 12 having a steering wheel 14, a steering column 16 with a torsion bar 17, and a measuring device 18, and a lower portion with an auxiliary motor 20.

If the driver loads the steering wheel 14 with a torque, the steering column 16 is thereby rotated. The measuring device 18 determines the torque acting on the torsion bar 17 from the relative angle between the upper (steering wheel side) end portion and the lower end portion of the torsion bar 17. Further, an angular position sensor of the auxiliary motor 20 determines a rotation angle of the lower end portion of the torsion bar 17.

Based on the determined torque acting on the torsion bar 17 and the rotation angle of the lower end portion of the torsion bar 17, the assist motor 20 is regulated so that the assist motor provides an appropriate assist torque to steer the vehicle.

In a motor vehicle which is at least partially autonomous, it is necessary that the motor vehicle can detect whether the driver's hands are located on the steering wheel 14. For this purpose, in the method described below, only the following measured variables are considered: the measured variables have been measured by the measuring device 18 and the angular position sensor of the auxiliary motor 20 of the steering system 10, more precisely taking into account the angle of rotation of the lower end of the torsion bar 17 and the torque acting on the torsion bar 17.

First, the upper portion 12 of the steering system 10 is modeled according to the physical surrogate model shown in FIG. 2. In this model, the system consisting of the steering wheel 14, the steering column 16 with the torsion bar 17 and the measuring device 18 consists of a system with a moment of inertia J_SWheelHas a spring constant c_tbarAnd a spring 24 having a damping coefficient b_tbarThe material damping 26 is modeled. Here, the spring 24 and the material damping 26 model the torsion bar 17.

additionally, by having a damping coefficient b_SWheelTakes into account the torque T_DriverThe steering wheel 14 is damped due to viscous friction, in particular due to bearing friction on the steering wheel 14 (at which the driver loads the steering wheel 14). Total counter-torque T caused by Coulomb friction in the upper portion 12 of the steering system 10_frictionResisting torque T_Driver。

such an equation can be derived from the physical surrogate model: the equations form a mathematical model of the upper portion 12 of the steering system 10. This is explained in detail below.

The state of the steering wheel 14 is now modeled with a linear state space model. In this context, state is understood to mean the variables required to describe the systemthe minimum set of (c). Here, the state of the steering wheel 14 is considered. The important state variable is the angle of rotation of the steering wheel 14And rotational angular velocityI.e. in particular

The temporal dependency of the states is not explicitly shown next, but is assumed to be default. The development of the state of the steering wheel 14 over time is given by the following equation:

The equation is either a differential equation or a differential equation, depending on whether continuous or discrete evolution over time is considered. In this case, the amount of the solvent to be used,The angle of rotation of the lower end portion of the torsion beam 17, which in this embodiment is determined by an angular position sensor (i.e., known). In addition, u_dist＝T_Driver+T_frictionIs the (unknown) sum of the torque at which the driver loads the steering wheel 14 and the reaction torque due to coulomb friction.

u_distUnknown disturbances occurring in the upper part 12 of the steering system 10 that describe the state. Matrices A and B describe statesAnd depends on the parameters of the mathematical model.

As already mentioned, the measuring device 18 determines the torque acting on the torsion bar 17 from the relative angle between the upper end and the lower end of the torsion bar 17, which in turn is denoted T_tbarAnd (4) showing. Measured torque T_tbarthe state of the steering wheel 14 is related by the following equation:

Here, the matrices C and D describe the current state at the steering wheel 14Partially known and partially unknown input variablesAnd the measured torque T_tbarThe interrelationship between them. Equation ofTogether with the above equations for the development of the state of the steering wheel 14 over time, a linear state-space model for the state of the steering wheel is constructed.

The state of the steering wheel 14 and the disturbance variable u cannot be inferred directly from the measurement of the angle of rotation of the lower part of the torsion bar 17 and the torque acting on the torsion bar 17_dist. More precisely, the state of the steering wheel 14 and the disturbance variable u must be estimated_dist。

For this purpose, kalman filters are used. The kalman filter estimates the state of the steering wheel 14 and unknown input parameters based on the measured parameters and the selected mathematical model. More specifically, the Kalman filter estimates the angle of rotation of the steering wheel 14Angular velocity of rotation of steering wheel 14and disturbances T acting on the upper part 12 of the steering system 10_Driver+T_friction. Further, the rotational angular acceleration of the steering wheel 14 is estimatedIn addition, the damping coefficient b can also be known_SWheelUnder the condition of (1) passing throughIs estimated according toThe reaction torque caused by viscous friction is calculated.

above the torsion bar 17, with a combined moment of inertia J for the steering system 10_SWheelThe equation of motion contents of the section (a) is as follows:

Next, for the sake of simplicity, the portion of the steering system 10 above the torsion bar 17 is referred to as the steering wheel 14. Further, it is assumed that the rotation angle of the upper end portion of the torsion bar 17 coincides with the rotation angle of the steering wheel 14 under the framework of the model.

According to the moment of inertia J of the steering wheel 14_SWheelThe equation of motion is solved. This yields:

Thus, all the additionally required variables for calculating the moment of inertia J of the steering wheel 14 are estimated by the kalman filter_SWheelas required. More precisely, all the unmeasured variables required for calculating the moment of inertia of the steering wheel 14 and all the variables required for this that cannot be measured are estimated.

In the embodiment discussed here, the torque T acting on the torsion bar 17 is measured by the measuring device 18_tbar. Alternatively, however, the torque acting on the torsion bar 17 may be estimated by a kalman filter.

Now, the calculated moment of inertia J of the steering wheel 14 is given_SWheelpredetermined setpoint value J of the moment of inertia of steering wheel 14_SWheel，nomin particular by differencing two moments of inertia.

when the driver's hands (or one hand) are on the steering wheel 14, the moment of inertia of the steering wheel 14 is different from a predetermined nominal value of the moment of inertia. Accordingly, when the inertia moment of the steering wheel 14 differs from the target value by more than a predetermined deviation value, it is recognized that both hands are positioned on the steering wheel 14.

The deviation values can be selected such that a positive recognition error rate (recognized that both hands are on the steering wheel 14, although this is wrong) and/or a negative recognition error rate (unrecognized that both hands are on the steering wheel 14, although both hands are on the steering wheel) is respectively below 10%, preferably below 5%, particularly preferably 0%.

In other words, the method described above is based on an observer in the sense of a control technique, as shown in fig. 4. The actual system comprising the steering wheel 14, the steering column 16 with the torsion bar 17 and the measuring device 18 is simulated by a mathematical model as explained above. The mathematical model serves as a basis for the design of the viewer. The observer ("upper observer" in fig. 4) is composed of known input variables and measured variables u_comtrolOr y_measestimating unknown state variables and input parameters as explained aboveThus, parameter J_SWheelAnd a measurement parameter T_tbarAre calculated together ("parameter calculation" in fig. 4) and compared with the rated value ("comparison with rated value" in fig. 4).

Alternatively, the rotation angle of the steering wheel 14 may be determined as follows. The angle of rotation of the upper end of the torsion bar 17 can be reconstructed from the angle of rotation of the lower end of the torsion bar 17 determined by the angular position sensor and the measured torque acting on the torsion bar 17 by solving an equation based on the angle of rotation of the upper end of the torsion bar 17

Wherein the content of the first and second substances,Are the upper and lower ends of the torsion bar 17Difference in rotation angle of the segments. Within the framework of the model used, it may be provided that the angle of rotation of the upper end of the torsion bar 17 is equal to the angle of rotation of the steering wheel 14. The angle of rotation of the steering wheel 14 is then available for further calculations and does not have to be estimated by a kalman filter.

If the measuring device 18 of the steering system 10 is designed such that it can measure the angle of rotation of the lower end and/or the upper end of the torsion bar 17 in addition to the torque acting on the torsion bar 17, a number of simplifications with respect to the method described above result.

If the measuring device 18 measures the rotation angle of the lower end portion of the torsion bar 17, the rotation angle may be used directly as explained above for the kalman filter or for determining the rotation angle of the upper end portion of the torsion bar. That is, it is not particularly necessary that the rotation angle of the lower end portion of the torsion bar be determined from the signal of the angular position sensor of the auxiliary motor 20.

If the measuring device 18 measures the angle of rotation of the upper end of the torsion bar 17 (and thus of the steering wheel 14), this angle of rotation can be used directly as a measured variable for further calculations. That is, the angle of rotation of the steering wheel 14 need not be first estimated by the kalman filter, among other things.

Similarly, if the measuring device measures the rotation angles of the upper end portion and the lower end portion of the torsion beam 17, the two rotation angles can be directly used for further calculation.

next, the following is taken as a starting point: the measuring device 18 is configured such that it measures at least the rotation angle of the upper end portion of the torsion beam 17 or the rotation angle of the upper end portion of the torsion beam 17, which can be determined by the rotation angle of the lower end portion of the torsion beam.

The upper part 12 of the steering system 10 can then be modeled by means of a simplified physical surrogate model shown in fig. 3. In contrast to the physical replacement model shown in fig. 2, the spring 24 and the material damper 26 are omitted here. This makes it possible to simplify the determination of the torque acting on the steering wheel 14 by means of a kalman filter.

As explained above, the angle of rotation of the steering wheel 14 can be used as a measurement variableFor use and not necessarily first estimated by a kalman filter. In this case, the measured variable is then the angle of rotation of the steering wheel 14, i.e. the angle of rotationthe known input variable being the torque acting on the torsion bar, i.e. u_control＝T_tbar. The moment of inertia of the steering wheel 14 can then be determined and compared to a setpoint value in a similar manner to that described above.

With regard to the remaining features of the method and further steps and advantages, reference is made to the above explanations.