DE19603430A1 - Motor vehicle axle load determn. circuit - Google Patents

Abstract

The circuit contains an evaluation stage (12) which processes data received from sensors (10, 15, 16). The evaluation stage receives signals from a yaw rate sensor (10) which reproduce the pitching motion of the vehicle and derives the axle loads and/or the wheel contact forces from the sensor signals. The equation for the load on the front axle is given as the sum of the static component of the front horizontal force, the dynamic component of the front wheel contact force, twice the mass of the front suspension and twice the mass of a front wheel. The rear wheel axle load formula is equivalent.

Description

The invention relates to a circuit arrangement according to the General term according to claim 1. Knowledge of the current axis load distribution or wheel load distribution is for many applications gen in automotive engineering - z. B. for ABS, active driving Plant systems - useful. Especially with active chassis the damping factor is wheel-selectively controlled. The actual Wheel loads can be used, for example, with piezorestrictive devices Quartz sensors can be detected. Such sensors are in each case the spring dome between the spring plate and the vehicle chassis assembled. In a known anti-lock brake system sensors are used, which are used by the Achsla generate the most dependent measurement signals (DE-C 33 30 483).

The known circuit arrangements are not very reliable sig and quite complex.

The invention has for its object the effort for it average of axle loads and wheel loads in a motor vehicle reduce the testimony and the reliability of the investigation increase.

This object is achieved according to the invention by a circuit arrangement according to claim 1 solved. Appropriate further training the invention are laid down in the subclaims.

An advantage of the invention lies u. a. in that with her in addition to the axle load distribution, he also the wheel load distribution lets average, d. H. the forces with which the individual tires riot points are charged.

An embodiment of the invention is described below hand of the drawing explained. Show it:  

Figure 1 is a schematically illustrated motor vehicle when driving uphill with the movement quantities and forces occurring.

Fig. 2 shows the case of a vehicle in a horizontal position occurring defects Tenden suspension forces and axle loads, and

Fig. 3 shows a circuit arrangement according to the invention in a schematic representation, and

FIG. 4 shows a flow chart of a program executed in the circuit arrangement according to FIG. 3.

A motor vehicle 1 moves on a roadway 2 , which is inclined at an angle a relative to the horizontal plane 3. The front axle of the motor vehicle is represented by a front wheel 4 , the rear axle by a rear wheel 5 . The respective wheel suspension essentially consists of a spring 6 and a shock absorber 7 .

The vehicle 1 is in Fig. 2 on a horizontal track 8th To show the suspension forces more clearly, the vehicle is shown lifted off the axles.

At a suitable point in the motor vehicle, for example in the center of gravity S, a yaw rate sensor 10 is arranged which, for the sake of brevity, is also referred to as a yaw rate sensor 10 . Biaxial yaw rate sensors are used, for example, on a larger scale in video cameras for the purpose of image stabilization. Such a sensor 10 delivers two output signals which are fed to an evaluation circuit 12 for determining the axle load ( FIG. 3). A control computer 14 contained in this evaluation circuit 12 , designed for example as a microprocessor, uses a simple mathematical vehicle model with which the four wheel contact forces are calculated from the two sensor signals.

With the evaluation circuit 12 , in addition to the yaw rate sensor 10 , a pitching speed sensor 15 and an inclination angle sensor 16 can also be connected. The evaluation circuit 12 is connected to an ABS control unit 18 via a data line 19 and to an active chassis control unit 20 via a data line 21 . Both data lines, which can also be implemented as a bus, enable a data and control signal exchange in both directions.

Based on the apparent from FIGS . 1 and 2 Fahrzeugmo models below mechanical equations are set on. However, the formula values used in the equations are defined in list form beforehand:

α slope
ϕ ′ ′ pitch acceleration
Θ _h reduced moment of inertia on the rear axle
Θ _v reduced moment of inertia on the front axle
Θ _chassis moment of inertia of the vehicle body around the y-axis
f _{zv_sus} Horizontal force at the front that acts on the spring-damper system
f _{zh_sus Rear} horizontal force that acts on the spring-damper system
fs _{zv_sus} static part of the horizontal force at the front
fd _{zv_sus} dynamic part of the horizontal force at the front
fs _{zh_sus} static part of the horizontal force behind
fd _{zh_sus} dynamic part of the horizontal force behind
m _chassis mass of the vehicle body
l wheelbase
l _h Distance from vehicle body center of gravity to rear axle
l _v Distance between the center of gravity of the vehicle body and the front axle
x ′ ′ longitudinal vehicle acceleration
α1, α2, α3 filter constants (can also depend on the horizontal force or the damping)
b2, b filter constants (can also depend on the horizontal force or the damping)
c1, c2, c3 filter constants (can also depend on the horizontal force or the damping)
d2, d filter constants (can also depend on the horizontal force or the damping)
fd _zv (n) time-discrete dynamic component of the front wheel contact force
fd _zh (n) time-discrete dynamic part of the wheel contact force at the rear

To establish a torque balance acting on the motor vehicle, reduced vehicle body moments of inertia Θ _v , Θ _h about the two axes of rotation are first calculated:

Θ _v = Θ _chassis + m _chassis * (l _v ² + h²) (Eq. 1)

Θ _h = Θ _chassis + m _chassis * (l _h ² + h²) (Eq. 2)

In these and the following equations, the front axle of the motor vehicle 1 is characterized by the subindex "v" and the rear axle of the motor vehicle by the subindex "h".

Based on the front and rear wheel contact point of motor vehicle 1 , a moment balance is now set up. The forces resulting from the torque balance for the front and rear axles can be broken down into a static and dynamic component, provided that the terrain gradient changes only slightly.

f _{zv_sus} = fs _{zv_sus} + fd _{zv_sus} (Eq. 3)

fs _{zv_sus} = m _chassis * g * cis (α) * l _h / l
fd _{zv_sus} = m _chassis * (x ″ + g * sin (α)) * h / l + Θ _h * Φ ″ / l (Eq. 4)

f _{zh_sus} = fs + fd _{zh_sus} (Eq. 5)

fs _{zh_sus} = m _chassis * g * cos (α) * l _v / l (Eq. 6)

fd _{zh_sus} = m _chassis * (x ″ + g * sin (α)) * h / l -Θ _v * Φ ″ / l (Eq. 7)

The behavior of the spring-damper system 6.7 on each axis can be described using a higher-order recursive filter. A second-order filter is used for this below. Since the springs are prestressed by a static component, only the dynamic component is filtered. The two forces fd _{zv_sus} and fs _{zh_sus} are shown here in a time-discrete manner.

fd _zv (n) = al * fd _{zv_sus} (n) = a2 * fd _{zv_sus} (n-1) + a3 * fd _{zv_sus} (n-2) -b2 * fd _zv (n-1) -b3 * fd _zv (n -2) (Eq. 8)

fd _zh (n) = cl * fd _{zh_sus} (n) + c2 * fd _{zh_sus} (n-1) + c3 * fd _{zh_sus} (n-2) -d2 * fd _zh (n-1) -d3 * fd _zh (n -2) (Eq. 9)

The following two equations give the wheel contact force for the front axle f _zv and the wheel contact force for the rear axle f _zh :

f _zv = fs _{zv_sus} + fd _zv + 2 * m _{v_sus} + 2 * m _vrad (Eq. 10)

f _zh = fs _{zh_sus} + fd _zh + 2 * m _{h_sus} + 2 * mh _hrad (Eq. 11)

The current angular velocity supplied by the yaw rate sensor 10 is scanned in the longitudinal and transverse axes of the vehicle via an analog / digital converter contained in the evaluation circuit 12 and not shown separately. If the motor vehicle 1 is provided with an inclination angle sensor 16 , the inclination angle α is transmitted therefrom to the evaluation circuit 12 , otherwise the inclination information is transmitted from another control device contained in the motor vehicle.

In the control computer 14 , the angular velocity in the vehicle longitudinal direction up to the pitch angle is integrated and the angular velocity in the vehicle transverse direction up to the roll angle. The axle load distribution can be calculated from the pitch angle, the roll angle, the terrain gradient, and the known sizes of left and right wheel base, front and rear lane and vehicle speed. A comparison of the pitch and roll angle is carried out when the terrain inclination angle and the yaw rate take the value "0". The yaw rate can also be determined approximately using the wheel speed.

The program to be processed in the control computer 14 of the circuit arrangement according to the invention will now be explained with reference to the flow diagram of FIG. 4. After starting the program, the following sensor data or signals are read in in a first (program) step S1:
ϕ 'of the pitch angle sensor 15
x ′ ′ + _{G of} an acceleration sensor in the vehicle's longitudinal axis
α of the terrain incline or incline angle sensor 16

In a second step S2, the sensor data are processed as follows:
ϕ ′ ′ Calculation of the pitch angle acceleration from the derivation of the pitch angle over time
x ′ ′ Correction of the acceleration signal around the Erdanzie component by the measured slope

In a third step S3, the stati is calculated share of the axle load distribution for the front and rear axis in the reference point "upper spring, damper mounting" according to the following relationships:

fs _{zv_sus} = m _chassis * g * cos (α) * l _h / l

fs _{zh_sus} = m _chassis * g * cos (α) * l _v / l

In a fourth step S4, the dyna is calculated mix share of the axle load distribution for the front and Rear axle in the reference point "upper spring, damper attachment" according to the following relationships:

fd _{zv_sus} = -m _chassis * (x ″ + g * sin (α)) * h / l + Θ _h * Φ ″ / l

fd _{zh-_sus} = m _chassis * (x ″ + g * sin (α)) * h / l -Θ _v * Φ ″ / l

In a fifth step S5, the dyna is filtered mix axle loads of the front and rear axles according to the following Relationships:

fd _zv (n) = al * fd _{zv_sus} (n) + a2 * fd _{zv_sus} (n-1) + a3 * fd _{zv_sus} (n-2) -b2 * fd _zv (n-1) -b3 * fd _zv (n -2)

fd _zh (n) = cl * fd _{zh_sus} (n) + c2 * fd _{zh_sus} (n-1) + c3 * fd _{zv_sus} (n-2) -d2 * fd _zh (n-1) -d3 * fd _zh (n -2)

In a sixth step S6, the Wheel contact forces for the front and rear axles in the cover point "tire road" from the static part of the axle  load distribution, the filtered, dynamic part of the axis load distribution, the wheel suspension masses and the wheel masses, according to the following relationships

f _zv = fs _{zv_sus} + fd _zv + 2 * m _{v_sus} + 2 * m _{v_rad}

f _zh = fs _{zh_sus} + fd _zh + 2 * m _{h_sus} + 2 * m _{h_rad}

This is the end of a program run.

The performance of the above equations is with Computer simulations have been confirmed. Was used as a basis a motor vehicle running at a speed of 80 km / h is braked with a deceleration of about -1.2 m / s².

Claims (3)

1. Circuit arrangement for determining the axle loads in a motor vehicle ( 1 ) with data supplied by sensors ( 10 , 15 , 16 ) and with one of the sensor data processing the evaluation circuit ( 12 ), characterized in that in the evaluation circuit ( 12 ) Signals from a yaw rate sensor ( 10 ) are received, which reflect the pitching movement of the motor vehicle, and that the axle loads and / or the wheel contact forces of the motor vehicle are calculated from these sensor signals. 2. Circuit arrangement according to claim 1, characterized in that the axle loads are calculated with the following formulas for the wheel standing forces on the front axle (f _zv ) and on the rear axle (f _zh ): f _zv = fs _{zv_sus} + fd _zv + 2 * m _{v_sus} + 2 * m _vrad f _zh = fs _{zh_sus} + fd _zh + 2 * m _{h_sus} + 2 * mh _hrad ,
wherein:
fs _{zv_sus} the static component of the horizontal force at the front,
fs _{zh_sus} the static part of the horizontal force behind,
fd _zv the dynamic part of the wheel contact force at the front
fd _zh the dynamic part of the wheel contact force at the rear
m _{v_sus is} the mass of a front suspension
m _{h_sus} the mass of a rear suspension
m _{v_rad} the mass of a front wheel
mh _{h_rad} the mass of a rear wheel
are. 3. Circuit arrangement according to claim 1, characterized in net that the yaw rate sensor is designed as a two-axis sensor is, by the rotational movements by two perpendicular to each other stationary axes are detected.