KR101776819B1 - Turnover Prediction Method of Excavator - Google Patents

Abstract

The present invention relates to a method to determine a turnover state of an excavator, capable of simply calculating a zero moment point (ZMP) as a criterion to determine a turnover risk of the excavator. According to the present invention, the method comprises: a step (S10) of measuring a repulsive force value of the excavator with respect to the ground by an attached force sensor; a step (S20) of measuring a posture value of the excavator in a state separated from the ground by an inertial sensor attached to the excavator; a step (S30) of calculating a repulsive force in a direction opposite to gravity by the repulsive force value and the posture value found by the step (S10) and the step (S20); a step (S40) of calculating the ZMP which is a point wherein a sum of moment of forces applied to the excavator; a step (S50) of determining whether or not a position of the ZMP is out of a stable region of a support polygon which is the least polygon wherein the excavator comes in contact with the ground; and a step (S60) of warning a driver of risk when the position of the ZMP is out of the safe region of the support polygon in the step (S50).

Description

[0001] Turnover Prediction Method of Excavator [

The present invention relates to a method of determining the conduction state of an excavator, and more particularly, to a method of determining a ZMP (Zero Point Moment) as a criterion for judging a risk of conduction of an excavator in operation, And a method for distinguishing an excavator conduction state.

An excavator is a heavy equipment used for digging soil on the ground. In some cases, it is used for various works.

Fig. 1 and Fig. 2 show an example of a wheel-type excavator.

As shown in Figs. 1 and 2, a general wheel-type excavator includes a lower traveling body 1, an upper swing body 12 pivotally mounted on the lower traveling body 1, A first work device (boom) 13 fixed to the upper swing body 12 so as to be rotatable within a predetermined angle range; a second work device (boom) 13 having one end rotatably fixed to the upper swing body 12, A first hydraulic cylinder (14) rotatably fixed at a predetermined position of the apparatus (13) for rotating the first working apparatus (13) within a predetermined stroke, and a second hydraulic cylinder A second working device (arm) 16 fixed to the other side so that the bucket 15 is rotatably fixed to the other side of the first working device 13, Is fixed to one end of the second working device (16), and the second working device (16) is rotated in a predetermined stroke And a second hydraulic cylinder 17 which is rotatably fixed at one end to the second working device 16 and whose other end is rotatably fixed to the bucket 15 to drive the bucket 15, And a hydraulic cylinder (18).

1 shows a state in which the center of gravity of the equipment is within the support point when the working device of the excavator is located in front of the equipment.

That is, when the position of the center of gravity G1 of the equipment becomes closer to the center 2 of the equipment itself than to the fulcrum 1 of the equipment as shown in Fig. 1, when the equipment is operated in front of or behind the equipment, It is stable and does not conduct.

Figure 2, on the other hand, shows a situation in which the center of gravity of the equipment is at risk of being turned off beyond its fulcrum when the working device of the excavator is located laterally of the equipment.

That is, even when the distance 4 from the center 2 of the equipment itself to the bucket 15 is the same as in Fig. 1, when the working device is turning in the lateral direction, the position of the center of gravity G2 of the equipment Is located outside the supporting point (1), and the risk of conduction is increased.

Various devices for preventing an excavator from being conducted during operation have been developed. For example, Korean Unexamined Patent Publication No. 10-2010-0127963 entitled " Unmanned Excavator Fall Prevention System and Method "

The above-mentioned prior art is to prevent occurrence of conduction of an unmanned excavator by recognizing the possibility of occurrence of conduction of an unmanned excavator to a user who is remotely adjusting through an input unit of the regulator, and is provided with state information including attitude information and position information And a sensor module for detecting and transmitting the sensor module.

In addition, the prior art regulator transmits a control signal according to a user's input unit operation through wireless communication with an unmanned excavator to an unmanned excavator to perform work, receives status information from an unmanned excavator in operation, The stability level value of the unmanned excavator is calculated.

When the calculated stability level value exceeds the threshold level value, the controller outputs the vibration to the input unit so that the user can feel the tactile sense, thereby alerting the user to the occurrence of the conduction of the unmanned excavator. .

Also disclosed in Korean Patent Laid-Open No. 10-2005-0101783 is "a method for preventing the hydraulic excavator with a crane function to which the conduction algorithm is applied ".

In the hydraulic excavator serving as a crane using a working device having a boom, a boom cylinder, an arm, an arm link, an arm cylinder, a bucket, a bucket cylinder, a bucket link and a hook device, A first step of installing a displacement sensor on each of the joint portions and sensing a turning angle and a working height of the working device by sensing the respective turning angles; A second step of detecting an actual load suspended on a hook device by sensing a pressure, a third step of deriving a ZMP by applying a working radius, a working height and an actual load value of the detected working device, A fourth step of setting a stable region of the hydraulic excavator, an effective stability region, and a conduction region; and a fifth step of displaying on the load display monitor provided in the driver's seat in accordance with the result of setting by region, In the working of the machine, both the static component and the dynamic component of the load are considered to determine the conduction state of the hydraulic excavator.

Fig. 3 shows a method of deriving ZMP (Zero Point Moment) at a point where the sum of the external force moments is zero by the conventional method, and ZMP is calculated by the following [Equation 1].

[Formula 1]

However, the above formula (1) has a disadvantage in that the ZMP is derived from the position and acceleration of each material point, and the derivation process is complicated.

As a conventional technique for preventing the excavator from turning, there is a pressure detecting means for detecting the operating pressure of the hydraulic cylinder to inform the driver of the degree of danger of the equipment, or when a pressure higher than a predetermined set pressure is generated in the hydraulic cylinder, Limiting techniques are known.

However, in the above-described conventional art, a ZMP is derived by attaching a motion sensor or a position sensor to a moving and rotating member such as a driving unit, a boom, and an arm of an excavator.

Therefore, there is a problem in that it is necessary to grasp the position of the accurate material point of each module to which the sensor is attached, and there is a problem in that it is difficult to derive a correct ZMP without considering the load applied to the bucket.

KR 10-2010-0127963 A KR 10-2005-0101783 A KR 1999-0043610 A

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of calculating a ZMP by simply and accurately calculating a ZMP as a criterion for judging the risk of the conduction of an excavator.

It is another object of the present invention to prevent the value of the material point of each module such as a driving unit, a boom module, and an arm module from being taken into account for ZMP calculation.

It is still another object of the present invention to provide a ZMP calculator capable of calculating an accurate ZMP in consideration of a load applied to a bucket during calculation of ZMP.

According to another aspect of the present invention, there is provided a method for determining whether there is a danger of being conducted during an excavator operation, the method comprising: (a) measuring a reaction force value of an excavator with respect to the ground by a force sensor attached to the excavator (B) measuring an attitude value of the excavator in a state in which the excavator is separated from the ground by an inertial sensor attached to the excavator, (c) calculating a reaction force value and an attitude value obtained by the steps (S10) and (S30) of calculating the reaction force in the opposite direction (Z-axis direction) to the gravity by using the following equations (2) and (3) A ZMP (Zero Moment Point) is calculated (step S40), and a formula (2) P _{x ( zmp )} = (P _x1 F _z1 + P _x2 F _z2 + P _x3 F _z3 + P _x4 F _z4 ) / (F _z1 + F _z2 + F _z3 + F _z4 ), [Expression 3] P _{y ( zmp )} = (P _y1 F _z1 + P _y2 F _z2 + P _y3 F _z3 + P _y4 F _z4 ) / (F _z1 + F _z2 + F _z3 + F _z4), (e) the position of the ZMP obtained in the S40 step, Step (S50), (f) to determine if the excavator is out of the stable region of minimum polygon of the support polygon (Support Polygon) in contact with the ground the S50 (S60) warning the driver when the position of the ZMP is out of the safe area of the support polygon.

The step (S10) of measuring the reaction force of the excavator is characterized by measuring the vertical reaction force from the ground by a sensor measuring the force applied to the wheel of the excavator.

Further, the excavator is a wheel type excavator, and the force sensor is an air pressure sensor.

Also, the excavator is a track type excavator, and the force sensor is a load cell.

According to the present invention, the ZMP can be calculated using the reaction force of the excavator with respect to the ground, thereby making it possible to simply derive the ZMP for determining the risk of the excavator being turned.

Further, the ZMP can be calculated without considering the position of the material point of each module such as the driving unit, the boom module, and the arm module.

Also, since the load applied to the bucket is also taken into account in calculating the ZMP, accurate ZMP can be calculated.

Also, when the ZMP exceeds the threshold value during the operation, warning of the danger of turning to the driver is warned through the alarm sound and the lightening, thereby preventing the excavator from being turned off.

1 and 2 are views showing an example of a conventional wheel type excavator.
3 is a diagram for explaining a ZMP calculation method for determining a conduction state of an excavator according to the related art;
4 is a diagram for explaining a ZMP calculation method for determining a conduction state of an excavator according to the present invention.
5 is a diagram for explaining a process of deriving a support polygon according to the present invention from a wheel-type excavator.
6 is a view showing a state in which a wheel is separated from a ground surface in a track-type excavator;
7 is a diagram for explaining a process of deriving a support polygon according to the present invention from a track-type excavator.
8 is a flowchart showing a process of determining a conduction state of an excavator according to the invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS. 4 to 8. FIG.

(A) measuring a reaction force value of an excavator with respect to the ground by a force sensor attached to the excavator, (b) measuring a reaction force value of the excavator with respect to the ground by using an inertial sensor attached to the excavator, (C) calculating a reaction force in the opposite direction (Z direction) to the gravitational force based on the reaction force value and the attitude value obtained by the steps S10 and S20; (S30), (d) calculating a ZMP (Zero Moment Point) at which the sum of moments of forces acting on the excavator is zero, (e) calculating a position of the ZMP obtained in S40, (Step S50); (f) warning the driver when the position of the ZMP is out of the safe range of the support polygon in step S50 (step S50).

In step S10 of measuring the reaction force of the excavator, the vertical reaction force from the ground is measured by a sensor that measures a force acting on the wheel of the excavator.

Preferably, the force sensor is an air pressure sensor for a wheel type excavator and a load cell for a track type excavator.

Since the air pressure sensor and the load cell itself are well known in the art, a detailed description thereof will be omitted.

In the case of a wheel-type excavator, the force sensor is mounted on each wheel, as shown in FIG. 4, and the excavator is in the most stable state when the four force sensors all have the same value.

When four sensors are mounted on each wheel as shown in FIG. 4, the probability that the excavator will be turned in a direction in which the force measurement value is large is increased.

For example, when the values of the sensor 1 and the sensor 2 mounted on the front wheel are much higher than the values of the sensors 3 and 4 mounted on the rear wheel, the possibility of the excavator being conducted to the front becomes high.

In order to derive the ZMP, a force in the Z axis direction at each force sensor point is required. In the case of using the one-axis load cell as the force sensor, in order to obtain the force in the Z axis direction, Is required.

The inertial measurement unit (IMU) is a sensor for measuring an inertial force, and is composed of an acceleration sensor for measuring gravity and a gyro sensor for measuring angular acceleration.

As shown in FIG. 6, the inertial sensor measures the attitude of the wheel when the wheel of the excavator is separated from the ground.

When the excavator is separated from a part of the ground as shown in Fig. 6, the Z direction forces of the sensors 1 and 2 can be calculated as follows.

F _z1 = F ₁ COS?

F _z2 = F2 COS θ

When the reaction force value of the excavator is measured by the force sensor and the posture value of the excavator is measured by the inertial sensor, the reaction force in the opposite direction to the gravity (Z-axis direction) is calculated.

ZMP (Zero Moment Point) is the position where the pressure center occurs when the ground and the object come into contact with each other, and the point where the force moment becomes zero.

As a result, the risk of overturning increases as the ZMP approaches the boundary of the contact surface.

Conventionally, the ZMP is derived from the position value of the center of gravity and the acceleration value (see Equation 1).

Accordingly, as shown in Fig. 3, there is a problem that the position value of each sensor module is required, and the load applied to the bucket is not considered.

However, according to the present invention, since the ZMP is derived using the reaction force between the ground and the excavator, it is possible to derive the accurate ZMP by taking the load applied to the bucket into consideration without requiring the position value of each sensor module.

The X-direction coordinate of the ZMP according to the present invention is calculated by the following [Expression 2], and the Y-direction coordinate of the ZMP is calculated by the following [Expression 3].

[Equation 2] _x P _(zmp) = (P F _{x1 z1} + _z2 + P P F _{x2 x3 x4} P F _z3 + _z4 F) / (F F _z1 + _z2 + _z3 + F F _z4)

[Expression 3] P _{y (zmp)} = (F P _{y1 z1} + _z2 + P F P _{y2 y3 y4} P F F _z3 + _z4) / (F F _z1 + _z2 + _z3 + F F _z4)

In [Formula 2] and [Formula 3], P _x1 To P _x4 is the X-axis direction distance from the first to fourth sensors in the center reference coordinate, P _y1 To P _y4 is The distance in the Y axis from the first sensor to the fourth sensor in the reference coordinates, F _z1 To F _z4 means a reaction force considering the case where the excavator is separated from the ground at each point.

If, when four wheels of a wheel-type excavator is in contact with both the ground and has, since it is not necessary to take into account the force of gravity perpendicular to the direction (Z direction), the F _z1 To F _z4 will be F ₁ through F ₄ , as shown in FIG.

However, as shown in Fig. 6, a part of the wheel may be spaced apart from the ground during the operation of the excavator.

In this case, F _z1 is F ₁ cos θ, F _z2 is F 2 cos?.

5 shows a support polygon in which the excavator is a minimum polygon tangent to the ground, and shows that the ZMP value calculated by the equations [2] and [3] is located in the stable region of the support polygon have.

That is, according to the present invention, it is determined that there is no danger of conduction when the stable polygon is set in the support polygon, the ZMP is calculated by the reaction force of the excavator, and the ZMP is within the stable region of the support polygon.

In the case of a wheel-type excavator, the support polygon has a rectangular shape formed by the four ground points of the wheels.

Further, in the case of a track-type excavator, the support polygon is a rectangle formed by a portion where the two orbits abut against the ground.

7 is for explaining a method of deriving a support polygon in a track-type excavator.

The support polygon can be obtained through the inertial sensor (IMU: Inertia Measurement Unit) roll (Roll: rotation in the X axis direction), pitch (rotation in the Y axis direction), and yaw , It is possible to derive each orbit end vertically.

The support polygon becomes a threshold value of the ZMP, and as the ZMP approaches the outer side of the support polygon, the possibility that the excavator is conducted becomes high.

Fig. 5 shows that the ZMP in the support polygon is in the stable region. In this case, it can be judged that there is no danger that the excavator is conducted.

The support polygons depend on the size of the excavator, and the stable region in the support polygons can be determined by simulation.

Hereinafter, a process of determining the conduction state of the excavator according to the present invention will be described with reference to FIG.

First, the reaction force of the excavator against the ground is measured by a force sensor mounted on the excavator.

In the case of a wheel-type excavator, the force sensor may be an air pressure sensor, and in the case of a track-type excavator, the force sensor may be a load cell.

Then, the inertial sensor mounted on the excavator measures the attitude of the excavator in the state of being separated from the ground.

Then, a reaction force in the opposite direction (Z-axis direction) to gravity is calculated by the reaction force value and the posture value.

Then, ZMP (Zero Moment Point), which is the point where the sum of the moments of the forces acting on the excavator is zero, is calculated by [Equation 2] and [Equation 3].

Then, it is determined whether or not the ZMP is within the stable region of the support polygon of the excavator.

If the ZMP value deviates from the stable region of the support polygon, the driver informs the driver through a warning sound or a light.

If the ZMP value is within the stable region of the support polygon, the above process is repeated.

Although the technical idea of the present invention has been described above with reference to an excavator as an example, the present invention is not limited to the structure and operation as described above. It will be understood by those skilled in the art that many changes and modifications may be made without departing from the scope of the invention as defined in the appended claims. And all such modifications and changes as fall within the scope of the present invention are therefore to be regarded as being within the scope of the present invention.

Claims (4)

A method for determining whether there is a risk of being conducted during operation of an excavator,
(a) measuring a reaction force value of the excavator with respect to the ground by a force sensor attached to the excavator,
(b) measuring an attitude value in a state where the excavator is separated from the ground by an inertial sensor attached to the excavator,
(c) calculating (S30) a reaction force in the opposite direction (Z-axis direction) from the gravitational force by the reaction force value and the attitude value obtained in steps S10 and S20,
(d) Calculating ZMP (Zero Moment Point) at a point where the sum of the moments of the forces acting on the excavator is 0 (S40) by the following [Equation 2] and [Equation 3]
[Equation 2] P_{x ( zmp )}= (P_x1 F_z1 + P_x2 F_z2 + P_x3 F_z3 + P_x4 F_z4) / (F_z1 + F_z2 + F_z3 + F_z4)
[Equation 3] P_{y ( zmp )}= (P_y1 F_z1 + P_y2 F_z2 + P_y3 F_z3 + P_y4 F_z4) / (F_z1 + F_z2 + F_z3 + F_z4)
(Wherein P_x1 To P_x4Is the X-axis direction distance from the first to fourth sensors in the center reference coordinate, P_y1 To P_y4The The Y-axis direction distance from the first sensor to the fourth sensor in the reference coordinates, Fz_OneFz₄Means the reaction force considering the case where the excavator is separated from the ground at each point).
(e) determining (S50) whether the position of the ZMP obtained in step S40 is deviated from a stable region of a support polygon having a minimum polygon tangent to the ground,
(f) warning (S60) the driver when the position of the ZMP is out of the safe range of the support polygon in step S50. The method according to claim 1,
The step (S10) of measuring the reaction force of the excavator comprises:
And a vertical reaction force from the ground is measured by a sensor for measuring a force applied to the wheel of the excavator. 3. The method of claim 2,
Wherein the excavator is a wheel type excavator and the force sensor is an air pressure sensor. 3. The method of claim 2,
Wherein the excavator is a track type excavator and the force sensor is a load cell.

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