DE102004004804A1 - Motor vehicle safety control circuit has wheel speed sensors and yaw rate, pitch and steering angle sensors to supply control unit for actuation of rollover control - Google Patents

Abstract

The motor vehicle (10) safety control circuit has wheel speed sensors (12,14,16,18) generating multiple wheel velocity signals and a steering angle sensor, a yaw rate sensor, a longitudinal acceleration sensor and a pitch angle sensor. A controller generates a longitudinal vehicle velocity value in response to the sensor outputs and uses this to control the vehicle safety system such as a rollover control.

Description

The invention relates to a system that determines the operating state of a motor vehicle, in particular the along the vehicle's longitudinal direction measured instantaneous longitudinal speed of the motor vehicle at its center of gravity.

It is a well known practice that control different operating dynamics of a motor vehicle, to achieve active safety, for example by means of the so-called Gierstabilitäts- and roll stability control systems. at a newer development combines all available subsystems, to better vehicle safety and better dynamic To achieve driving behavior than ever. The effective operation of the different Control devices require a highly accurate determination of the operating states of Motor vehicles with a short response time, regardless of the road conditions and driving conditions. Such operating states of a Vehicle have the vehicle's longitudinal speed, the Vehicle lateral speed and the vehicle vertical speed, the along the body's longitudinal axis, the body's own Transverse axis or the body's own vertical axis are measured, the position of the vehicle body, the direction of movement of the vehicle etc. on. In this disclosure, the focus is on the longitudinal direction and the transverse direction of the vehicle, i.e. the current longitudinal speed of the vehicle and the instantaneous lateral speed of the vehicle at its center of gravity.

One driving on a street Vehicle could due to the combination of its longitudinal movement and its transverse movement and its angular movement different Experience accelerations. For example, a would drive in a circle Vehicle have a lateral acceleration acting on the vehicle, which proportional to the second power of vehicle speed and the inverse function of the distance between the vehicle and the current one Yaw point is, or in other words, the product of the instantaneous longitudinal speed of the vehicle and the yaw rate of the vehicle. In another example, when a vehicle is cornering, the yaw rate of the vehicle and the drifting of the vehicle into a component Acceleration along the longitudinal direction of the vehicle whose size or Amount equal to the product of the lateral speed and the yaw rate of the vehicle. If the vehicle drift angle is known is the lateral speed of the vehicle is the product of the instantaneous longitudinal speed of the vehicle and the vehicle drift angle. It should also be noted that the so-called vehicle reference speed, which is often used in anti-lock brake controls and in vehicle yaw stability controls is used, the vector sum from the aforementioned longitudinal velocity and from the aforementioned lateral speed of the vehicle.

The mounted on a vehicle Sensors usually take the resulting effects from different sources. For example sends the lateral acceleration sensor mounted on the vehicle body a signal indicating the proportion of gravity and the vehicle position, the proportion of the product of the longitudinal speed and the Yaw rate of the vehicle and the share of the lateral speed of the vehicle contains. For the purpose of extracting usable information from the assembled Sensors and correcting sensor errors is a calculation or an estimate the current longitudinal speed of the vehicle of great Interest.

There are many methods and devices for determining vehicle speed using the vehicle wheel speed sensors. The vehicle wheel speed sensors are standard sensors that are used in anti-lock brake systems (ABS). See the following US patents for details: US 6224171 . US 6223135 . US 6112146 . US 5388895 . US 5365444 . US 5364174 and US 5184876 , In many of the above patents, vehicle speed is determined as a function of the speed of a selected vehicle wheel. To do this, at least one non-slip vehicle wheel is required.

The invention is based on the object to provide a means by means of which the operating state a vehicle, in particular the instantaneous longitudinal speed of the vehicle, both in the case where there is no slip on the vehicle wheels, can also be calculated or estimated in the case where the vehicle wheels Slip occurs.

This is done with a vehicle condition calculation means solved, which has the features in claim 1 and in particular from this exists. Have preferred developments of the invention especially exist additionally from the in the dependent claims described features.

The invention will now be more preferred based on embodiments with reference to the accompanying drawing described in more detail.

1 shows a schematic plan view of a vehicle, wherein the longitudinal speed and the transverse speed of the vehicle are shown at its corners or its wheels and at its center of gravity.

2 shows a schematic view of a vehicle wheel, wherein according to 2 the vehicle _corner speed along the longitudinal direction of a vehicle wheel is equal to the sum of the contact point slip speed ν _cp and the product of the rotation rate or angular velocity on the tread of the wheel ω _whl and the vehicle wheel rolling radius r ₀ .

The invention is explained below with reference to preferred embodiments relating to a motor vehicle that is moving on a three-dimensional road surface. The vehicle is driven on a three-dimensional road surface. The transverse speed and the longitudinal speed at the center of gravity of the vehicle are calculated with V _x . and V _y , the yaw rate or yaw rate of the vehicle is denoted by ω _z , the front wheel steering angle of the vehicle is denoted by δ. Using those vehicle movement variables, the speeds of the vehicle at its four corner positions at which the wheels are attached to the vehicle can be calculated along the body-specific longitudinal direction and the body-specific transverse direction using the following rule: V lfx = V x - ω z t f ; V lfy = V y + ω z l f V rfx = V x + ω z t f , V rfy = V y + ω z l f V lrx = V x - ω z t r , V lry = V y - ω z l r , V rrx = V x + ω z t r , V rrv = V v - ω z l r (1) where t _f and t _r denote the respective half-track for the front axle and for the rear axle, respectively, and l _f and l _r denote the respective distance between the center of gravity of the vehicle and the front axle and the rear axle, respectively. V _lf , V _rf , V _lr and V _rr denote the speeds along the respective direction of travel of the vehicle _wheels (or in other words the respective longitudinal direction of the vehicle _wheel ), which are the product of the respective angular velocity of the vehicle wheel on the tread and the respective vehicle wheel rolling radius. These speeds can be related to the corner speeds of the vehicle using the following rule: V lf = V lfx cos (δ) + V lfy sin (δ) V rf = V rfx cos (δ) + V rfy sin (δ) V lr = V lrx V rr = V rrx (2)

Inserting regulation (1) in regulation (2) results in the following regulation: V lf = (V x - ω z t f ) cos (δ) + (V y + ω z l f ) sin (δ) V rf = (V x + ω z t f ) cos (δ) + (V y + ω z l f ) sin (δ) V lr = V x - ω z t r V rr = V x + ω z t r (3)

Taking into account the following regulation: V v = V x tan (β) (4) you can therefore use the rule (3) to calculate both V _x and β. Since regulation (3) has two unknowns and four constraints, there are therefore different possibilities for calculating V, and β. For the following, the average front vehicle _{corner speed is} defined with V _f-ave and the average rear vehicle _{corner speed is} defined with V _r-ave , whereby the following rule applies:

Then regulation (3) leads to the following regulation: V f-ave = V x [cos (δ) + sin (δ) tan (β)] + ω z l f sin (δ) V rave = V x (6) which can be used to calculate the vehicle drift angle according to the following regulation:

It should be noted that the vehicle drift angle β is only by means of regulation (7) can be calculated if the vehicle steering angle is not zero. If the vehicle steering angle is approximately zero, it can proposed in Ford's invention disclosure No. 2000-1776 Procedures are used.

wobei alle diese Berechnungen gleich der tatsächlichen Fahrzeug-Längsgeschwindigkeit V_x. sein sollten, wobei folgende Vorschrift gilt: Vx = Vxi, für i = 1, 2, ..., 6 (9) The six options for calculating the vehicle longitudinal _speeds from the four vehicle _{corner speeds} V _lf , V _rf , V _lr and V _rr can be summarized as follows:

all of these calculations being equal to the actual vehicle longitudinal speed V _x . should be, whereby the following regulation applies: V x = V xi , for i = 1, 2, ..., 6 (9)

It should be noted that the regulations (7) to (9) for all driving conditions and all road conditions are correct simply due to the fact are that they are based on the kinematic relationships between the motion variables based.

The question now is how to determine the four vehicle _{corner speeds} V _lf , V _rf , V _lr and V _rr . These vehicle corner speeds can be measured by mounting four speed sensors on the four vehicle wheels, which speed sensors detect the respective longitudinal speed of the vehicle wheel center along the direction of travel of the respective vehicle wheel (or in other words along the respective vehicle wheel longitudinal direction). Furthermore, the speed sensors can be exchanged for four acceleration sensors, which detect the respective linear acceleration of the vehicle wheel center along the direction of travel of the respective vehicle wheel.

Since mainly vehicles without the aforementioned speed sensors or acceleration sensors provided on the vehicle corners or the vehicle wheels are considered, the available sensors are the vehicle wheel speed sensors which are used in anti-lock brake systems (ABS). Those ABS vehicle wheel speed sensors measure the respective speed of the vehicle wheels. The vehicle wheel speed _sensor outputs are usually calibrated to provide the linear direction velocities ν _sensor-lf , ν _sensor-rf , ν _sensor-lr and ν _sensor-rr by multiplying the rotational angular velocity of the vehicle wheel by the nominal rolling radius of the vehicle wheel. See for details 2 , It should be noted that the vehicle wheels do not only perform a rotary movement but also a linear sliding movement, that is to say that the vehicle wheels furthermore have a longitudinal slip. The longitudinal slip is caused by the relative movement between the respective vehicle wheel and the road at its contact point. For the following, the longitudinal velocities of such relative movements at the contact points between the respective vehicle _wheel and road are referred to as ν _cp-lf , ν _cp-rf , ν _cp-lr and ν _cp-rr , so that the vehicle _{corner velocities} as the sum of two speeds can be expressed: V lf = ν cp-lf + ν sensor-lf , V rf = ν cp-rf + ν sensor-rf V lr = ν cp-lr + ν sensor-lr , V rr = ν cp-rr + ν sensor-rr (10)

If there is no longitudinal _slip on the four wheels, ν _cp-lf, ν _cp-rf , ν _cp-lr and ν _{cp-rr should} all be zero and the vehicle _{wheel speed sensors} provide the exact description of the vehicle _corner speeds. Consequently, the rules (7) to (9) can be used to determine the vehicle drift angle and the To calculate or estimate the current longitudinal speed of the vehicle.

If ν _cp-lf, ν _cp-rf , ν _cp-lr and ν _{cp-rr are} not zero, but their respective amount is a fraction of the respective amount of ν _sensor-lf , ν _sensor-rf , ν _sensor-lr and ν _sensor-rr , then the minimum of the six calculated variables can be used to describe the vehicle's longitudinal speed according to the following rule: V ^ x = min {V ^ x1 , V ^ x2 , V ^ x3 , V ^ x4 , V ^ x5 , V ^ x6 } (11).

where V ^ _x1 , V ^ _x2 , V ^ _x3 , V ^ _x4 , V ^ _x5 , V ^ _{x6 are} calculated in a similar way as in regulation (8), but with the sensor signals replacing the vehicle _{corner speeds} as in the following regulation:

Taking into account that the term sin (δ) sin (β) is negligible in contrast to the term cos (δ), V ^ _x2 , V ^ _x3 , V ^ _{x4 can} also be calculated approximately independently of the vehicle drift angle β according to the following regulation become:

In order to use the regulation (11) and the regulation (12) safely for calculating the longitudinal vehicle speed, the amount of the contact point slip speeds must be recorded quantitatively. In the following, d _f and d _r denote the contact point speed differences between the left vehicle wheel and the right vehicle wheel of the front axle and the rear axle, respectively, and m _f and m _r denote the respective mean value of the contact point speed of the left vehicle wheel and the right vehicle wheel Front axle or the rear axle, whereby the following regulation applies:

wobei m_f näherungsweise unabhängig vom Fahrzeug-Driftwinkel gemäß folgender Vorschrift berechnet werden kann:

Defined in this way, d _f , d _r , m _f and m _r can be calculated from the known signals, which have the vehicle wheel speeds, the yaw rate, the steering angle (on the vehicle wheel) and the calculated or estimated longitudinal vehicle speed, in accordance with the following regulation :

where m _{f can be} calculated approximately independently of the vehicle drift angle according to the following regulation:

Consequently, if the quantities calculated according to regulation (15) are all smaller than certain limit values, ie the conditions in the following regulation: d f ≤ γ l , m f ≤ γ 2 , d r ≤ γ 3 , m r ≤ γ 4 (17) are fulfilled for the calibration parameters γ ₁ , γ ₂ , γ ₃ , γ ₄ , the contact point slip speeds are regarded as negligible. If the conditions in regulation (17) are not met, a further analysis is necessary.

One such case where the conditions in regulation (17) are not met, but the vehicle is driven in a permanent steering condition, is the case in which the vehicle is driving a corkscrew, the vehicle making a tight curve, but with approximately constant steering input. In this case, if the vehicle's rear wheels move in the path of the vehicle, the following rule applies to the vehicle corner speeds:

Based on this condition, the longitudinal vehicle speed V _x can be calculated according to the following rule:

Taking into account that the term sin (δ) tan (β) is negligible in contrast to the term cos (δ), V ^ _{x-xs-steer can be} calculated approximately independently of the vehicle drift angle β according to the following rule:

If the conditions of regulation (17) not met are and the vehicle is not in the permanent steering state, then is to Correct the errors due to the contact point slip another Correction necessary.

The implementation of the correction using the information about the vehicle longitudinal acceleration and the vehicle pitch is now considered. The instantaneous longitudinal velocity V _{x of} the vehicle is described as the sum of two parts: (1) the part of turning the four vehicle wheels as calculated in regulation (11) or regulation (20), (2) the part of longitudinal sliding due to the vehicle wheel slip. The part based on the turning of the four vehicle _wheels is called V _x-noslip , which speed is either V ^ _x or V _x-xs-steer , and the part based on the vehicle _{wheel slip} is called V _x-slip , the following Regulation applies: V x = V x-noslip + V x-slip (21)

The longitudinal acceleration sensor signal can be divided into three parts according to the following regulation: a x-sensor = V x - V x tan (β) ω z-sensor - gθ y (22)

V _x-slip can therefore meet the following requirement: V x-slip - V x-slip tan (β) ω z-sens or = f (t) (23), where: f (t) = a x-sensor - gθ y - V x-noslip + V x-noslip tan (β) ω z-sensor (24)

The analytical solution for V _x-slip can be obtained according to the following regulation:

A digital, iterative model can be derived from the regulation (25) for calculating V _x-slip as in accordance with the following regulation: Γ (k + 1) = Γ (k) + tan (β (k + 1)) ω z-sensor (k + 1) ΔT Π (k +1) = Π (k) + f (k + 1) e Γ (k + 1) ΔT V x-slip (k + 1) = Π (k + 1) e -Γ (k + 1) (26)

This results in the following regulation: V x (k) = V x-nonslip (k) + V x-slip (k) (27)

Bibliography:

• [1] US 6224171 , "Method for correcting a vehicle reference speed," (WABCO, 2001).
• [2] US 6223135 B1 , "Method and device for determining a variable describing the speed of a vehicle," (BOSCH, 2001).
• [3] US 6112146 , "Method and device for determining a variable describing the speed of a vehicle," (BOSCH, 2000).
• [4] US 5388895 , "Method and system for detecting and correcting vehicle speed reference signals in anti-lock brak systems," (KELSEY-HAYES, 1995)
• [5] US 5365444 , "Method of estimating vehicle velocity and method of and system for controlling brakes," (HONDA, 1994)
• [6] US 5364174 , "Antilocking system," (BOSCH, 1994)
• [7] US 5184876 , "Antilocking system," (BOSCH, 1993)
• [8] Invention Disclosure No. 200-1776 by Ford, "Vehicle side slip angle estimation using dynamic blending and considering vehicle attitude information, "(Jianbo Lu and Todd Brown, 2000)

Claims (8)

Vehicle condition calculation means, comprising: - Medium to determine the corner speed of the vehicle, - Medium for determining the vehicle drift angle, and - Medium to determine the longitudinal vehicle speed. Vehicle condition calculation means according to claim 1, being used as a means for determining the vehicle corner speed Speed sensors are used, which are close to the vehicle wheel axes of rotation are mounted and the speeds along the vehicle wheel direction of travel measure up. Vehicle condition calculation means according to claim 1, being used as a means for determining the vehicle corner speed Acceleration sensors are used, which are close to the vehicle wheel axes of rotation are mounted and along the accelerations of the vehicle wheels measure the vehicle wheel travel directions, integrating those Accelerations of the vehicle wheels Calculations for provides the vehicle corner speeds. Vehicle condition calculation means, in particular according to claim 1, in which vehicle wheel speed sensors are used as means for determining the vehicle corner speed and which further comprises: - a means for calculating the vehicle drift, - a means for calculating the vehicle longitudinal speed in the event of a low vehicle wheel slip , - a means for calculating the vehicle longitudinal speed in the case of a continuous steering condition, and - a means for calculating the vehicle longitudinal speed, the information about the vehicle pitch position used to calculate the corrected term, which compensates for the vehicle wheel slip. Vehicle condition calculation means according to claim 4, wherein the means for calculating the vehicle drift is as follows Sensor signals used: - the four vehicle wheel speed sensor signals, - the yaw rate sensor signal, and - the Vehicle wheel steering angle. Vehicle condition calculation means according to claim 4, being the for in the case of a low vehicle wheel slip means provided for Calculate the vehicle's longitudinal speed having: - on Means for quantifying the slip of the vehicle wheels, - a means to calculate six variables representing the vehicle's longitudinal speed describes using one or two vehicle wheel speed sensor signals together with the yaw rate sensor signal and the vehicle wheel steering angle, and - a means to use the lowest value of the above six variables, the vehicle's longitudinal speed to calculate. Vehicle condition calculation means according to claim 4, the means for calculating the vehicle longitudinal speed, which regarding of the vehicle wheel slip is compensated, the longitudinal acceleration sensor signal, the yaw rate sensor signal and that by means of a vehicle pitch rate sensor obtained information regarding the vehicle pitch. Vehicle condition calculation means, in particular according to claim 1, the means for calculating the instantaneous longitudinal speed of the vehicle uses all sensor signals available in a vehicle stability control system, that features: - four Vehicle wheel speed sensors, - a steering angle sensor, - one Longitudinal acceleration sensor, - one Yaw rate sensor, - one from a vehicle stability control system, such as a roll stability control system Vehicle pitch angle, and One from a vehicle stability control system, such as a yaw stability control system Vehicle drift angle.