DE102007039332A1 - Driver`s hand contact condition detecting method for use in vehicle, involves evaluating driver steering moment using condition observer, and detecting contact condition between hands and handle by hand-off detector using evaluated moment - Google Patents

Abstract

The method involves detecting steering movement of a steering handle (1) using a moment sensor (4) and an angle sensor (3), and modeling the free steering movement of the handle under observation of non-linear friction-effects based on experimental measurement data. The driver steering moment is determined as a condition using a condition observer (8) and is evaluated using the observer. The contact condition between the hands of a driver and the steering handle is detected by a hand-off detector (9) using the evaluated steering moment.

Description

The The invention relates to a method and a steering assistance system for Detecting the contact state of at least one hand of a driver on the steering handle of a vehicle.

A steering handle with the aforementioned features is known from DE 196 31 502 C1 known. As part of the introduction of modern driver assistance systems such. As braking or lane keeping assistance as well as modern security systems information is increasingly needed on the behavior of the driver in the driving situations occurring. From the generic document, it is known to attach to the steering handle a fiber optic sensor by means of which the elastic deformation of the shroud of the steering handle due to the clasping by the driver can be detected and used as a measurement signal for controlling vehicle-side functions via an on-board evaluation.

With the progressive development of vehicle dynamics control and driver assistance systems gains the detection of the contact state of hands of the driver with the steering handle increasingly important. That's the way it is, for example from the μ-split braking with the active superimposed Steering, or known from DSR (Driver Steering Recommendation), that dependent from the detected contact state between the hands of the driver and the steering handle, the controller parameters are adjusted so that the potential Vibrations of the steering handle and thereby impaired Driving behavior of the vehicle eliminated or minimized. Also in driver assistance systems with guidance assistance it is necessary to constantly monitor the contact state of the hands with the steering handle, to avoid a driving situation in which the driver during the Ride hands from the steering handle takes.

DE 10048956 discloses a steering handle with a measuring device for determining the hand rest of the vehicle driver and coupled to the measuring device evaluation circuit which controls at least one vehicle-specific device, wherein on the steering handle together with the hand rest surface of the driver and with a dielectric forming Lenkhandhabebezug a capacitor forming conductive Surface is arranged, wherein the conductive surface of the steering handle on a ??? At??? connected to a power supply? Measuring circuit is connected such that at ??? at??? the steering handle of the vehicle driver's resting hand on the basis of the capacitive coupling between the steering handle and the vehicle body caused by the vehicle driver from the output of the measuring circuit to the vehicle mass flowing measuring current recorded a measured variable and a corresponding measurement signal of the evaluation circuit.

The DE 10121693 A1 and DE 10027922 A1 disclose methods and apparatus for detecting the contact between the hands and the steering handle based on specially provided for this purpose sensors to be mounted on the steering handle.

In the US 6219603 It is disclosed that the contact between hands and steering handle is detected with an estimated steering torque of the driver calculated by a torque equation. However, this method does not take into account the strong influence of nonlinear friction effects on the steering column. As a result, this method can not clearly detect the contact state with small driver steering moments.

Of the Invention is based on the object, a method for more reliable Detecting the contact state between the hands of a driver and the To provide steering handle.

The Task is solved by the features of claim 1 and the features of the claim 7. Further advantageous embodiments are specified in the dependent claims.

It is understood that under the concept of steering handle hereinafter make all the devices, which are used for steering a vehicle.

In one embodiment of the method for detecting the contact state of at least one driver's hand on the steering handle of a vehicle, the steering movement of the steering handle is detected by means of at least one torque sensor and at least one angle sensor, the free steering movement of the steering handle taking into account non-linear friction effects based on modeled experimental measurement data, the driver steering torque determined by the state observer as a state that a Used state observer for the estimation of the driver steering torque and detected by means of the estimated driver steering torque, the contact state between the hands and the steering handle.

In a further embodiment the dynamic model is a nonlinear differential equation which describes the free steering movement of the steering handle.

A particularly advantageous embodiment is characterized by that the nonlinear dynamic model of the steering handle by numerical Treatment is transformed into a linear model.

In a further particularly advantageous embodiment, the detection of the manual on / off state by comparing the moving average of the amount of the estimated driver's steering torque in a predefined time window is carried τ with a predefined threshold value ε1, and a comparison of the moving average of the amount of the quotient | x ₂ / M _s | with a predefined threshold ε2.

A further advantageous embodiment is characterized in that at a zero crossing of the measured torque M _s, the modified quotient | x ₂ / M ^ _s | for calculating the moving average of the quotient | x ₂ / M _s | is used.

In a further advantageous embodiment, an active detection of the hand-off state is performed when the estimated driver steering torque in a predefined time window τ is smaller than a predefined threshold value ε1 and the quotient | x ₂ / M _s |, optionally | x ₂ / M ^ _s |, greater than a predefined threshold ε2.

The object is likewise achieved by a steering assistance system which has a steering handle ( 1 ), a handlebar ( 2 ), Means for detecting and determining steering movement signals ( 3 . 4 ), Means for steering signal filtering ( 5 . 6 ), Means for the formation of mathematical derivatives ( 7 ), an observer for the driver steering torque ( 8th ) and a hand-off detector ( 9 ).

The Steering movement of a steering handle is advantageous with a non-linear considering dynamic model both the viscous and the Coulomb friction, whereby the estimation error is advantageously reduced.

It is in the inventive method a disturbance observer for the estimate used the driver's steering torque. This is a double explicit Differentiating the steering angle signal is not necessary and it takes place Advantageously, a reduction of the calculation effort for estimating the Driver steering torque.

Of Further, in the method according to the invention is not the contact state detected directly, but determines the current driver steering torque. this makes possible For certain safety-critical applications, the controller parameters not only from the contact state of hands on the steering handle but also dependent on the current driver steering torque to configure.

Often, steering angle and steering torque sensors are already present in a steering assistant system. The method according to the invention can advantageously use these sensor signals, which are not specifically intended for detecting the contact state between the hands and the steering handle, in order to detect the contact state between the hands and the steering handle. The steering handle thus remains unchanged as a conventional steering wheel and it is not necessary, as in the DE 196 31 502 C1 specified to modify the steering wheel accordingly.

One embodiment The invention is illustrated in the drawings and will be described below described in more detail.

It demonstrate

1 A schematic structure of a steering assistance system according to the invention

2 A comparison between measurement and simulation

3 and 4 The influence of the time window τ on hand-off detection

Of the Invention is based on the idea that the driver while driving constantly Makes steering corrections. Even when driving straight ahead is always still some "holding moment" when holding the steering handle available.

• • Durch das vom Fahrer auf die Lenkhandhabe ausgeübte Lenkmoment M_h.
• • Durch die Momente, die durch aktives Lenken von Aktuatoren wie EPS etc., oder durch unebenen Fahrbahn hervorgerufene Störmoment, oder als ein Gegenmoment des Lenkmomentes M_h. All diese Momente werden an dem Wirkungspunkt A, wo sich der Momentsensor befindet, als M_s zusammengefasst und lassen sich mit dem Momentsensor (4) ermitteln.
• • Durch das durch Reibung verursachte Moment M_r. Dieses Moment wirkt ständig als Widerstand gegen die Rotationsbewegung der Lenkhandhabe (1).

In the 1 is shown schematically that the rotational movement of the steering handle ( 1 ) can be caused and influenced by the following moments:

• • By the steering torque M _h exerted by the driver on the steering handle.
• • By the moments, by the active steering of actuators such as EPS, etc., or by uneven road surface caused disturbance torque, or as a counter torque of the steering torque M _h . All these moments are summarized as M _s at the point of action A where the torque sensor is located, and can be combined with the torque sensor (FIG. 4 ) determine.
• • Due to the moment caused by friction M _r . This moment constantly acts as a resistance to the rotational movement of the steering handle ( 1 ).

The rotational movement of the steering handle can be described by the following moment equation φ .. = 1 J (M s + M r + M H ) Eq. (1)

Where J is the moment of inertia of the steering handle ( 1 ) and the handlebar ( 2 ) above the moment sensors ( 4 ) and φ .. the angular acceleration of the steering handle.

In a hand-off state, in which the driver does not put his hands on the steering handle, the driver steering torque M _{h is} equal to zero and the Eq. (1) can be passed through φ .. = 1 J (M s + M r ) Eq. (2) describe. In the following, this is referred to as "free steering movement of the steering handle".

• 1. Die nicht durch Fahrer beeinflusste „freie Lenkbewegung der Lenkhandhabe" möglichst genau mit einem nichtlinearen dynamischen Modell darzustellen.
• 2. Das aus experimentellen Messdaten ermittelte nichtlineare Lenkhandhabemodell in ein numerisch behandelbaren linearen Modell zu transformieren.
• 3. Das vom Fahrer ausgeübte Lenkmoment als eine Störgröße in dieses Modell einzubeziehen, wobei dies mit einem Zustandsbeobachter ermittelt wird.

The inventive method is preferably divided into three phases, wherein the individual phases are further divisible:

• 1. The non-driver influenced "free steering movement of the steering handle" as accurately as possible to represent a non-linear dynamic model.
• 2. To transform the non-linear steering handle model determined from experimental measurement data into a numerically treatable linear model.
• 3. To include the steering torque exerted by the driver as a disturbance variable in this model, this being determined by a condition observer.

The friction moment in Eq. (1) and Eq. (2) is modeled as follows:

verbessert die numerische Behandelbarkeit der Gl. (3). Für die weitere Beschreibung werden Gl. (2) und Gl. (3) folgendermaßen zusammengefasst:

wobei x₁ die Lenkwinkelgeschwindigkeit ist und

b = 1 / J. Die Zustandsgleichung Gl. (4) stellt die Modellstruktur der Lenkhandhabedynamik dar. Die unbekannten Parameter a, b, b_c und ν in diesem Modell werden aus experimentellen Messdaten mit Parameteridentifikationsverfahren ermittelt.Here, γ _{ν is} the coefficient of viscous friction and γ _{c is} the Coulomb friction coefficient. The Coulomb friction can be represented by sign (φ.) · Γ _c , the term used here

improves the numerical treatability of Eq. (3). For further description Eq. (2) and Eq. (3) summarized as follows:

where x _{1 is} the steering angular velocity and

b = 1 / J. The equation of state Eq. (4) represents the model structure of the steering handle dynamics. The unknown parameters a, b, b _c and ν in this model are determined from experimental measurement data with parameter identification methods.

2 shows a comparison between a measurement and a simulation result of a model identified from measurement data. It can be seen that the model represents the steering movement of the steering handle very well.

durch die aus der gemessenen ϕ berechnete ϕ . ersetzt und dies wird mit dem Koeffizienten γ_c zusammen als Mc definiert:

The steering handle model Eq. (4) describes a non-linear dynamics of the steering handle and is not suitable for the design of a linear disturbance observer. In order to treat the model as a linear model, the steering speed becomes x ₁ in the nonlinear term

by the φ calculated from the measured φ. and this is defined together with the coefficient γ _c as Mc:

Since M _{c is} no longer dependent on the model state x ₁ , this can be considered as an independent input to the model. This is how the model Eq. (4) transform as a linear model: x. 1 = a · x 1 + b · M c + b · M s Eq. (6)

Another way to decouple Mc from x ₁ is not to use x ₁ (t _k ) in the calculation of Mc (t _k ), but always to use the observer ( 8th ) to use estimated x ⁀ ₁ (t _k-1 ):

Because at the sampling point t _k the observed state at the sampling point t _{k-1 is available} for the calculation of Mc (t _k ), Mc (t _k ) can be considered as a known input signal of the model.

wobei die erweiterte Zustandsvariable x₂ das Fahrerlenkmoment darstellt. ξ beschreibt das lineare dynamische Verhalten des Fahrerlenkmomentes. Bei einem Hand-Off Zustand, wobei der Fahrer seine Hände nicht auf der Lenkhandhabe legt, ist das Fahrerlenkmoment gleich 0 und bleibt unverändert. Daher kann x₂ als eine Konstante betrachtet werden und ξ hat bei einem Hand-Off Zustand einen Wert von 0.To determine the driver steering torque, the converted linear steering handle model Eq. (6) extended by a condition to be observed:

wherein the extended state variable x _{2 represents} the driver steering torque. ξ describes the linear dynamic behavior of the driver's steering torque. In a hand-off state where the driver does not put his hands on the steering handle, the driver's steering torque is 0 and remains unchanged. Therefore, x ₂ can be considered as a constant and ξ has a value of 0 in a hand-off state.

Even in a hand-on condition where the driver has his hands on the steering handle and the driver's steering torque does not change rapidly, one can approximate this at a constant time interval and ξ can be considered 0. Thus, the extended equation of state can be represented as follows:

Based of the extended state model Eq. (9) can be a state observer designed to appreciate the driver's steering torque.

That of the observer ( 8th ) determined driver steering torque does not reflect exactly the real driver steering torque, because the model is only an approximation of the real steering handle dynamics and the transformation of the model with Eq. (5). or Eq. (7) more or less affects the accuracy of the model. The observer himself also has his own dynamics and supplies the estimated value x ₂ for M _h with a certain time delay. In the extended steering handle model Eq. (9) the driver's steering torque is considered constant, which is generally not the case with a hand-on condition.

Therefore, in a hand-off state, it is possible that the driver steering torque estimated with the observer is not equal to zero. In order to detect the hand-off state as safely as possible, the following criterion for hand-off detection is used according to the invention:
When the moving average value of the estimated driver steering torque x ₂ in a predetermined time window τ is smaller than a predetermined positive threshold value ε1, and the moving average value of the ratio | x ₂ / M _s | is less than positive ε2, then the hand-off state is ( 11 true.

If the quotient | x ₂ / M _s | greater than ε2 and | M _s | is smaller than ε3 (zero crossing of the measured moment M _s ), then it is checked whether the quotient | x ₂ / M ^ _s | is less than ε2. Here, M _s = M _s + d M _s / dt × Δt Eq. (10). Is the condition | x ₂ / M ^ _s | <ε2, then the moving average is calculated instead of | x ₂ / M _s | according to Eq. (10) modified quotient | x ₂ / M ^ _s | used.

If the moving average value of the estimated driver steering torque x ₂ in a predetermined time window τ is less than ε1 and the moving average of the ratio | x ₂ / M _s | is greater than ε2, then an active hand-off detection is performed. Here, a predefined torque is exerted by the actuator on the steering system, so that the steering angle of the steering handle, for example, changes sinusoidally with a predefined amplitude and frequency. For this active steering movement, the hand-off detection is performed again as described above.

If the time delay the hand-off detection for the single application is not critical, the time window τ becomes a relative huge Take value. Preferably, the time window τ is between 50 [ms] and 200 [ms] to select.

3 and 4 show the influence of the time window on the detection of the hand-off state. It can be seen that with a larger time window τ, the method detects the hand-off state with higher security, but also with a greater time delay.

Claims (7)

Method for detecting the contact state of at least one hand of a driver on the steering handle of a vehicle, marked through the steps 1. the steering movement of the steering handle means at least one torque sensor and at least one angle sensor is detected, 2. the free steering movement of the steering handle below Pay attention to non-linear friction effects using experimental Measuring data is modeled, 3. the driver's steering torque means the state observer is determined as a state 4th that a state observer for the estimation the driver steering torque is used and by means of the estimated driver steering torque the contact state between the hands and the steering handle is detected. A method according to claim 1, characterized in that the dynamic model, which is the free steering movement of the steering handle describes a nonlinear differential equation. Method according to claims 1 and 2 characterized that the nonlinear dynamic model of the steering handle by numerical Treatment is transformed into a linear model. Method according to one of the preceding claims, characterized in that the detection of the hand-on / off state by a comparison of the moving average value of the estimated driver steering torque in a predefined time window τ with a predefined threshold ε1 and a comparison of the moving average value of the quotient | x ₂ / M _s | with a predefined threshold ε2. Method according to one of the preceding claims characterized in that at a zero crossing of the measured torque M _s, the modified quotient | x ₂ / M ^ _s | for calculating the moving average of the quotient | x ₂ / M _s | is used. Method according to one of the preceding claims, characterized in that the estimated driver steering torque in a predefined time window τ is smaller than a predefined threshold value ε1 and the quotient | x ₂ / M _s |, possibly | x ₂ / M ^ _s |, is greater than a predefined one Threshold ε2, an active detection of the hand-off state is performed. Steering assistance system for detecting the contact state of at least one hand of a driver on the steering handle of a vehicle, characterized in that the steering assistance system a Lenkahandhabe ( 1 ), a handlebar ( 2 ), Means for detecting and determining steering movement signals ( 3 . 4 ), Means for steering signal filtering ( 5 . 6 ), Means for the formation of mathematical derivatives ( 7 ), an observed for the Fahrlenkmoment ( 8th ) and a hand-off detector ( 9 ).