WO2004069568A1

WO2004069568A1 - System for safeguarding the driving stability of an industrial truck

Info

Publication number: WO2004069568A1
Application number: PCT/DE2003/003689
Authority: WO
Inventors: Gerold Müller
Original assignee: Bosch Rexroth Ag
Priority date: 2003-02-05
Filing date: 2003-11-07
Publication date: 2004-08-19
Also published as: DE10304658A1

Abstract

The invention relates to a device for controlling the driving stability of an industrial truck (1). The invention also relates to a method for controlling an industrial truck (1), whereby the load, the inclination of a mast (14) and of a lifting assembly (10), the lifting height of the load, the tilting forces acting upon the mast (14) and the accelerations acting upon the vehicle in the longitudinal and transverse direction are detected by means of an array of sensors and are compared with predetermined threshold values. These threshold values depend on the state of travel of the vehicle and cannot be voluntarily exceeded by the driver so that the rollover stability of the vehicle normally remains in the stable range irrespective of the state of travel (cornering, straight travel, hill descent, etc.).

Description

description

SYSTEM FOR SECURING THE VEHICLE STABILITY OF A HALL-AID VEHICLE

The invention relates to a device for ensuring the driving stability of an industrial truck and a method for controlling an industrial vehicle.

A problem with forklifts is that they can tip due to their short wheelbase, the small track width and the comparatively high center of gravity, especially when the load is raised. In particular, tipping over sideways, caused for example by excessive cornering speeds or by unilaterally driving over bumps on the ground, is one of the most common causes of accidents and kills a large number of injuries and fatalities each year. Legislators and employers are trying to counteract this trend by improving the skills of operators and through additional safety systems. There are currently so-called passive systems on the market, in which seat belts, side guards, side airbags etc. prevent the driver from being thrown out of the truck and injured when it is tipped over. However, these passive systems are accepted only unwillingly by the operators, since they are very difficult to handle in practical use, for example when the operators frequently get on and off.

EP 916 527 A2 discloses an active system for tipping stabilization of industrial trucks. According to the known solution, these are designed with a rear steerable pendulum axle, which lock in critical driving conditions by means of a hydraulic locking device and thus practically to a rigid axle can be made. In the known solution, this hydraulic locking device is controlled as a function of the transported load, the signals from a speed sensor and a sensor for detecting the yaw angle and as a function of the approximate height position of the load.

A disadvantage of this solution is that the system can only be used on industrial trucks with four wheels. Furthermore, a considerable outlay in terms of device technology is required in order to integrate the hydraulic locking device for the pendulum axis. It is also considered a disadvantage that this known system intervenes very early and, in certain driving conditions, already blocks the pendulum axis or sends signals to the driver if sufficient stability is actually still present, so that the efficiency of the vehicle is reduced.

In contrast, the invention has for its object to provide a device for controlling the driving stability of an industrial truck and a method for controlling an industrial truck, in which the tipping safety can be improved with minimal device engineering effort.

This object is achieved with respect to the device for controlling driving stability by the features of patent claim 1 and with regard to the method for actuating an industrial truck by the combination of features of patent claim 8.

According to the industrial truck with a

Numerous sensors, such as an angle sensor for detecting the mast inclination, a lifting height sensor for exact detection of a fork position, and a force sensor designed to detect tipping forces acting on a mast, a load sensor to record the load of the industrial truck and acceleration sensors to record the vehicle accelerations in the longitudinal and transverse directions. Depending on the data recorded via the sensors and the known vehicle parameters (dimensions, vehicle, weight (without load), center of gravity), the actual vehicle condition is then recorded (center of gravity, accelerations) and compared with limit values specified by the control system and by the vehicle control system intervened in such a way that these limit values cannot be exceeded arbitrarily, ie by control commands from the driver. The driving according to the invention therefore presupposes that the center of gravity of the vehicle and the load height and also their state change speeds are recorded so precisely that parameters of the vehicle are limited via the vehicle control so that the latter does not get into a critical state (tipping) ,

According to the invention, depending on the driving state, limit values for the lifting height, the vehicle speed, the maximum acceleration, the maximum steering angle and the maximum inclination can be specified.

In the case of very rapid changes in the driving state, it may still be possible that the specified limit values are exceeded. In this case, the control device intervenes directly in the vehicle control and countermeasures are initiated to prevent tipping. However, this direct intervention only takes place in the critical case, usually the driving state is kept in the stable range above the limit values described above. The driving safety of the industrial truck can be further improved if the center of gravity in the transverse direction is recorded as precisely as possible. In the case of industrial trucks with a tilting device for the mast that is actuated via two tilting cylinders, it is preferred according to the invention if a force sensor is assigned to each of these tilting cylinders, so that eccentric loads are recorded and are accordingly incorporated into the control. The respective force sensor does not have to sit directly on the inclination cylinder. It can also be located on the swivel joint between the mast and the chassis or on the mast suspension on the chassis.

According to the invention, the centers of gravity in the longitudinal axis, the transverse axis and the vertical axis are determined using the formulas according to subclaim 5.

With the aid of these very precisely determined centers of gravity, the current maximum acceleration when driving straight ahead (braking, accelerating) or when cornering (acceleration in the longitudinal direction and in the transverse direction) can be specified, for example, with the formulas specified in claim 6 and measured with the accelerators. be compared.

In the event that the control unit intervenes directly in the vehicle control in the case of critical driving conditions, this can be done according to the catalog of measures shown in sub-claim 7.

Other advantageous developments of the invention are the subject of further dependent claims.

The invention is explained in more detail below with the aid of schematic drawings. Show it: Fig. 1 is a schematic representation of a counterbalance truck with shown sizes for calculating the center of gravity;

Figure 2 is a schematic diagram to explain the tilt stability in the longitudinal and transverse directions.

3 shows a schematic representation of the counterbalance truck with large ones for calculating the accelerations in the longitudinal and transverse directions and

Fig. 4 shows a stability triangle to explain the tilt stability.

1 shows a highly schematic illustration of a counterweight stacker 1 with a driver's cab 2, a chassis with a front axle 4, a steerable rear axle 6, for example a pendulum axle, and a counterweight 8 arranged in the area of the rear axle 6.

A mast 10 with a mast 14 that can be tilted about an inclination axis 12 is mounted on the front of the truck. The setting of the angle of inclination α of the mast 14 takes place via an inclination device with, for example, two inclination cylinders 16 which are articulated to the vehicle frame and to the mast 14. A fork 17 is displaceably guided on the frame-shaped mast, the lifting height hg being adjustable by means of a schematically indicated lifting cylinder 18.

In the embodiment shown, the stacker is equipped with a lifting height sensor for detecting the lifting height hg, an angle sensor for detecting the mast inclination α,

Force sensors for detecting the tilt cylinder 16 supporting forces acting on the mast 14, acceleration sensors for detecting the vehicle acceleration in the longitudinal and transverse axes, and a pressure sensor for detecting the force applied by the lifting cylinder 18, which is equivalent to the load FL acting on the fork 17. With these sensors, practically all of the variable parameters of the fork rod pier required for the control according to the invention can be recorded and the exact centers of gravity and maximum accelerations can be determined from them.

The forklift 1 also has a control unit 20 which can be integrated in the vehicle control or can be designed as an external module. The signals emitted by the aforementioned sensors are processed in the control unit and compared with limit values stored in the memory of the control unit 20 and, depending on the result of this comparison, control signals are emitted to the hydraulic circuit of the truck or to the engine management.

The effects of mast deflection, tire deflection, fork deflection, etc. were neglected in the calculations explained below. As a result, the tilting limit around the front axle 4 when the mast 14 is inclined is actually lower than the calculated value and that the effective lever arm of the load with respect to the inclination axis 12 is larger than in the ideal case shown due to the aforementioned influencing factors (mast deflection ...) is. This error increases with increasing load, lifting height and forward tilt of the mast. With the tipping stability in the transverse direction, the actual tipping stability is higher than the calculated value, because due to the influences mentioned (mast deflection ...) the center of gravity of the load is lower than calculated. However, the influences mentioned are so small that they do not significantly affect the effectiveness of the The control described below can be disregarded.

Determination of the center of gravity

The center of gravity rgp and the weight Gp _{z of} the empty truck 1 without mast 14 and fork 17 are assumed to be known. These sizes are calculated from:

G _FZ = m _FZ * g with:

Mpg ⁼ mass of the empty vehicle g = gravitational acceleration ^r SF = ^(χ SF 'YSF' ^Z SF) ^with xgp, ygp, zgp center of gravity coordinates.

The center of gravity and the weight of the load plus the mast 14 and fork 17 must be determined based on the variable load and is calculated according to:

^G L ^{= m} L * 9 with:

ΠIL: mass of the load + mass (fork + mast) ^r SL = ^(χ SL _^ YSL ^Z SL ^{) with}

^X _S L 'YSL' ^Z SL Center of gravity coordinates of the load (plus mast fork).

The mass of the mast is a known parameter of the truck 1, the load and fork mass can be determined from the signal of the pressure sensor in the lifting cylinder 18. In principle, this is also the mass of the fork previously known, so that the weight of the load can be calculated from the pressure signal.

The total mass of the system and the overall center of gravity are then calculated according to:

m = m z + m.L and

r _s = 1 / m * (m _FZ + r _SF + m _L * r _SL ).

Position of the center of gravity in the longitudinal direction (x-axis)

As mentioned above, the center of gravity of the load is the common center of gravity of the load ΠIL, the fork 17 and the mast 14. In the longitudinal direction (x-axis), the torque equilibrium then applies according to FIG. 1:

FGL * ^X L = ^? * iFN * ^sin ß with:

F L = weight of the load, fork and mast

XL = lever arm of the center of gravity

F ^ detected via the force sensors of the tilt cylinder 16

Force (F ^ = F ^ L + FR (R: right tilt cylinder, L: left tilt cylinder)) lpjvj: distance tilt axis 12, point of attack tilt cylinder 16 on mast 14 ß = 90 ° - α + arctan [z ^ - Ip ^ * cos ) / (XAC ⁺ ^ FN * ^s ^ - ⁿ α)] with:

^Z A _C ^: vertical distance of the vehicle-side joint from the inclination axis 12,

^X AC ^: horizontal distance between the inclination axis 12 and vehicle joint and lpN ^: Distance between the inclination axis 12 and the mast-side joint of the inclination cylinder 16 (see FIG. 1).

The x coordinate of the load center of gravity then results from:

xL = (F _N * 1 _FN * sin ß) / F _GL .

Position of the center of gravity in the transverse axis (y-axis)

The following applies to the y coordinate of the center of gravity:

YS = ( ^F NL / (L + F _R )) * a - a / 2 with:

a: Distance between the two force sensors on the tilt cylinders 16 (mounted symmetrically to the vehicle)

F ^ L: force on the left or right inclination cylinder 16.

Position of the center of gravity in the vertical axis (z-axis)

The calculation of the z-coordinate of the center of gravity is somewhat more difficult than the ones described above

Calculations. This component can only be calculated if the values are at least two different

Combined mast inclinations.

In principle:

z _LS = z _A + zg + z _SG with:

z ^: Height of the inclination axis 12 (point A) above the ground (Fig. 1). zg: hg (see Fig. 1) * cos α - tan α * (XL - hg + sin α) and

hg, hgg p. Fig. 1.

Neglecting the prescribed load influences, z ^ is known as a vehicle parameter. The

Tilt angle a of the mast 14 is detected via the angle sensor, the lifting height hg can be detected with the lifting height sensor.

The size hgg (see FIG. 1) can be determined by knowing the otherwise tangible values for two different mast inclinations. The fork height hg can be retained, but the calculation also works with different fork heights hg. The two fork positions should be marked with indices 1 and 2. Accordingly, the size hgg is calculated according to:

h-sc? = ( ^χ τ ,? ~ hffg * sin α _? ) / cos α _? - (x _Tι1 - h _π1 * sin αη) / cos αη tan α.2 - tan α ^

According to the above, the x, y and z coordinates of the overall center of gravity (vehicle + load) can be determined from the signals from the lift height sensor, the angle sensor and the force sensors of the tilting cylinder 16 and the previously known, unchangeable vehicle parameters with high accuracy and with minimal Determine effort.

Before the calculation of the Kippstabilitat will be explained in the longitudinal and transverse direction, will first be discussed in the so-called stability triangle, which is shown in Fig. 2 for ^'a stacker 1 with load and without load. The truck 1 is shown schematically, with its front axle 4 and the steerable rear swing axle 6. In the event that the truck 1 transports a load, this weight of the load GL is in front of the front axle 4 in the direction of travel. The rear axle 6 is with the counterweight not shown. The forklift 1 with a pendulum axle 6 is in a stable state as long as the center of gravity is statically and dynamically within the dashed triangle of stability, which is characterized by the center distance of the front wheels VL, VR and the pivot point of the rear axle H. As long as the center of gravity S calculated according to the above statements is within this stability triangle V ,, VR, H, there is no danger. From the illustration in FIG. 2 it can be seen that the risk of tipping in the longitudinal direction with a load G ^ is greater than without a load. However, the tilting stability of the truck 1 carrying a load is greater than that of the unloaded truck. This can be seen from the distance between the center of gravity S and the adjacent side edge of the stability triangle.

In addition to the static conditions, such as the position of the center of gravity and the inclination of the vehicle, the risk of tipping is also largely determined by the dynamic forces. For example, braking when driving forwards and, conversely, accelerating when driving in reverse reduce the tipping stability. When cornering, the component of the centrifugal force acting in the longitudinal direction of the vehicle acts backwards in the direction of the rear axle and thus counteracts tipping over the front axle.

From the precalculated centers of gravity, the effective loads for predetermined driving conditions can then be Calculate longitudinal and transverse accelerations and use them to determine limit values.

Tilt stability in the longitudinal direction

The torque equation for the front axle 4 can be derived from the illustration according to FIG. 3. The following applies:

F _B = m * a _x = [(F _RV + F _RH ) * r + Fg * x _SB ] / z _SB with:

F _R y and F _R JJ: For braking, acceleration, forces transmitted to the front axle 4 and the rear axle 6 r: Distance of the inclination axis 16 from the ground ^X SB ' ^Z SB see FIG. 3 m: Total mass of the vehicle a _x : Acceleration in longitudinal direction.

With the help of the aforementioned equation, a permissible maximum acceleration in the longitudinal direction can then be defined, which essentially depends on the previously calculated center of gravity. A possible vehicle inclination can be determined with those acceleration sensors with which a _{x is} measured. According to the invention, the stacker 1 is then controlled in such a way that the actually measured acceleration a _{x is} smaller or at most as large as the maximum value calculated using the above equation.

Tilting stability in the transverse direction The tilting stability in the transverse direction (perpendicular to the plane of the drawing in FIG. 3) is calculated with the aid of the stability triangle according to FIG. 4.

As already mentioned in connection with Fig. 2, the parameters of the stability triangle of the truck 1, the wheelbase 1, the track width b, the angle γ between the leg HV _r (or H-Vj_) and the longitudinal axis x of the vehicle and the Position of the center of gravity S. Accordingly, the distance d of the center of gravity S from the respectively effective tilt axis - ie when driving to the left from the axis HV _r - is decisive for calculating the tilting moment in the transverse direction. This distance d is dependent on the center of gravity S and the mentioned parameters 1 and b.

The angle γ is then calculated according to:

γ = arctan [(b / 2) / 1],

the distance d is calculated according to:

d = xg * sin γ.

Neglecting the friction forces on the tires, the following applies to the moments with respect to the tilt axis HV _r :

Fg * d = F _B * zg with:

zg see Fig. 3

Fg: total weight of the vehicle including load

F _B : Acting due to the centrifugal acceleration

Force.

With F _B = m * a the centrifugal acceleration can then be calculated according to: a = (Fg * d) / (m * Zg).

The components of the centrifugal acceleration effective in the longitudinal and transverse directions can then be calculated from this centrifugal acceleration:

a _x = a * sin γ.

a _y = a * cos γ.

Depending on the total weight of the truck, the lever arm d and the center of gravity as well as the angle γ, maximum accelerations in the transverse and longitudinal direction can be specified for cornering, which the truck cannot arbitrarily exceed.

The specification of the limit values for the center of gravity and for the accelerations will generally keep the truck 1 in a driving state in which the risk of tipping is minimal. The sensor system described above enables these actual values to be recorded very quickly and precisely, so that continuous monitoring of the driving state is made possible. Despite these sophisticated sensors, there may be situations in which the truck 1 cannot be prevented from tipping over. Such situations can occur, for example, when driving over a curb. In these cases, the speed of change in the driving state is so great that it is no longer possible to intervene in time with the strategy described above in order to keep the driving state within the predetermined limit values. In these cases, the vehicle's driving condition must be actively intervened. However, such a direct intervention in the steering or in the driving speed involves certain risks connected, because this intervention can possibly prevent tipping, but the acceleration or change in the steering angle, which the driver does not want, can cause other damage. The following table summarizes some possible interventions in the critical case, ie when the strategy according to the invention is no longer sufficient to ensure the tilting stability. This table is not exhaustive and, depending on the design of the truck and the requirements of the manufacturer, it is quite possible that other strategies or at least only some of the measures summarized in the table will be taken to react in the critical case.

As can be seen from the above, certain parameters of the vehicle are limited by the strategy according to the invention for avoiding critical driving conditions so that it does not get into the critical condition at all. The sizes to be restricted are, for example, the lifting height, the vehicle speed, the maximum acceleration, the maximum steering angle, the steering speed and the mast inclination. These parameters are limited as a function of the driving state via the control unit 20, so that, for example, the load is raised or tilted further or a Increasing the driving speed is prevented by the control in order to keep the vehicle in a stable area. Depending on the application, other sizes to be restricted can be added.

Disclosed is a device for controlling the driving stability of an industrial truck and a method for controlling an industrial truck, in which the load, the inclination of a mast of a mast, the lifting height of the load, the tilting forces acting on the mast and the longitudinal and Accelerations acting on the vehicle in the transverse direction are recorded and compared with predetermined limit values. These limit values, which depend on the driving state, cannot be exceeded by the driver at will, so that the tipping stability of the vehicle generally remains in a stable range regardless of the driving state (cornering, driving straight ahead, downhill ...).

Reference character list

Counterbalanced trucks

cab

Front

rear axle

counterweight

mast

tilt axis

mast

tilt cylinder

fork

lifting cylinder

control unit

Claims

claims

1. Device for ensuring the driving stability of an industrial truck, which has a mast (14) which can be tilted by means of a tilting device (16), along which a fork (17) is guided in a height-adjustable manner, and with sensors for detecting operating parameters of the industrial truck, in particular with a load sensor to record the load transported by the industrial truck, an angle sensor to record the mast inclination, a lifting height sensor to record the fork position, a force or pressure sensor to record the tipping forces acting on the mast, and acceleration sensors to record the vehicle's accelerations in the longitudinal and transverse directions and with a control unit (20), by means of which, depending on known vehicle parameters such as dimensions, weight and center of gravity of the empty vehicle and the sizes detected by the sensors, an actual vehicle state is detected and limit values can be defined as a function of the driving state, which are active when S is active ystem can not be arbitrarily exceeded.

2. Device according to claim 1, wherein the limit values relate to the lifting height, the vehicle speed, the maximum acceleration, the maximum steering angle or the maximum mast inclination.

3. Device according to claim 1 or 2, wherein the control unit (20) intervenes directly in the vehicle control in the case of rapid, unpredictable changes in driving conditions.

4. Device according to one of the preceding claims, wherein the tilting device two inclination has cylinder (16), each of which a sensor is assigned.

5. Device according to one of the preceding claims, wherein the control unit (20) calculates the center of gravity in the longitudinal and transverse directions (XL, yg) according to the following equations:

x _L = (F _N * 1 _FN + sin ß) / Fg _L

YS = ⁽ F _N L ⁽ L + FNR)) a - a / 2

With:

Fft _f = supporting force on the tilt cylinders lpN = distance of the axis of inclination of the mast from the articulation of the tilt cylinder (Fig. 1)

ß = 90 ° - + arctan [(z ^ - lp ^ * cos) / (xr- ₁ g + 1 _FN * sin)]

With :

^Z AC ^: Vertical distance between the tilt axis (12) and the vehicle-side articulation point of the tilt cylinder

(16)

^X A _C ^: Horizontal distance between the inclination axis (12) and the vehicle's articulation point of the inclination cylinders (16). : Angle of inclination of the mast (14); the center of gravity in the height direction (zgg) is calculated according to:

Zgg = hgg / COS C6 and: ^h SG = ^(χ LS - ^h G2 * ^sin «2 ^{) cos} « 2 ^{~ (χ} Ll ^{~ h} Gl * sin _λ ) / cos ^O ] tan α2 - tan α_ with: indices 1, 2: two different fork positions.

6. Device according to one of the preceding claims, wherein the maximum accelerations are calculated as follows:

Straight ahead: a _x = [(F _RV + F _RH ) * r + Fg * x _SB ] / (z _SB * m) with:

F _R y and Fpj _f j: acceleration forces transmitted to the vehicle (FIG. 3), r: vertical distance of the inclination axis (12) from the ground,

Fg: total weight of the vehicle (load + vehicle curb weight), ^X _S B ^: distance of the total center of gravity from the front axle, zg _B : vertical distance of the total center of gravity from the ground and m: total mass of the vehicle (including load).

Cornering:

^a x ⁼ ( ^F G + d) * sin γ / (m * zg) ay = (Fg * d) cos γ (m * zg) with

d = xg + sin γ xg = center of gravity in the longitudinal direction γ = angle between the tilt axis (H-VR, VL) and the longitudinal axis x.

7. Device according to one of the preceding claims, wherein the control unit (20) is designed such that in certain driving conditions in which the driving condition-dependent limit values are exceeded, such as intervenes in the vehicle control system to prevent tipping:

8. Method for controlling an industrial truck, which has a mast (14) which can be tilted by means of a tilting device (16), along which a fork (17) is guided in a height-adjustable manner, and with sensors for detecting operating parameters of the industrial truck, in particular with a load sensor for detection the load transported by the industrial truck, an angle sensor for detecting the mast inclination, a lifting height sensor for recording the fork position, a force or pressure sensor for recording the tilting forces acting on the mast and acceleration sensors for recording the vehicle acceleration in the longitudinal and transverse directions, and with a control device that records the following parameters and defines limit values:

a) Detecting the load, the mast inclination, the lifting height, the tipping forces acting on the mast and the acceleration in the x and y directions.

b) Calculating the center of gravity in the longitudinal and transverse directions of the vehicle as a function of the values recorded via the sensors and of known vehicle characteristics.

c) Calculation of maximum accelerations in the longitudinal and transverse directions

Straight ahead:

a _x = [(F _RV + F _RH ) * r + Fg * x _SB ] / (z _SB * m) with:

FRV and FRH: acceleration forces transmitted to the vehicle (Fig. 3), r: vertical distance of the inclination axis (12) from the ground, Fg: total weight of the vehicle (load + vehicle empty weight), xg _B : distance of the total center of gravity from the front axle, zg _B : Vertical distance of the total center of gravity from the ground and m: total mass of the vehicle (including load);

Cornering:

* x = (Fg + d) * sin γ / (m * zg) ay = (Fg * d) cos γ (m * zg) with:

d = xg + sin γ xg = center of gravity in the longitudinal direction γ = angle between the tilt axis (H-VR, VL) and the longitudinal axis (x) and

d) Adaptation of the changeable driving state parameters in such a way that the limit values calculated in (3) are not exceeded.