WO2009076719A1

WO2009076719A1 - Active rollover prevention system for construction and road machines

Info

Publication number: WO2009076719A1
Application number: PCT/AU2008/001861
Authority: WO
Inventors: John Ibrahim
Original assignee: CONPLANT Pty Ltd
Current assignee: CONPLANT Pty Ltd
Priority date: 2007-12-17
Filing date: 2008-12-17
Publication date: 2009-06-25
Anticipated expiration: 2010-06-17
Also published as: AU2008338251A1; WO2009076719A9; AU2008338251B2

Abstract

An active rollover prevention system for construction and road machines, the system comprising: (a) means for sensing the pitch, tilt and articulation angles of the machine; (b) means for sensing the speed of the machine; (c) means for comparing the pitch, tilt and articulation angles against pre-determined safe operating speed using an information processing unit; (d) means for reducing the speed of the machine if it exceeds the pre-determined safe operating speed for the pitch, tilt and articulation angles, (e) means for warning the driver of the machine that the machine has exceeded the pre-determined safe operating speed or angle; and (f) means for re-positioning an attachment of the machine to a safe-operating position if the machine exceeds the pre-determined safe operating speed or angle.

Description

ACTIVE ROLLOVER PREVENTION SYSTEM FOR CONSTRUCTION AND

ROAD MACHINES FIELD OF THE I NVENTION

This invention relates generally to an active rollover prevention system for construction and road machinery, and more particularly, to an active rollover prevention system for a compactor with an eccentric vibrator. BACKGROUND TO THE INVENTION

Conventional active rollover prevention systems are adapted for standard automotive vehicles with a rigid single frame, a conventional steering system and a suspension system adapted for a relatively smooth roads.

However these conventional active rollover prevention systems cannot be used on construction and road machines which generally work on rough, unstable and uncompacted soil , which causes a wide margin of error for conventional active rollover prevention systems.

Moreover, the operation of some construction and road machines can significantly interfere with the operation of conventional active rollover prevention systems. For instance, in the case of a Compactor with an eccentric vibrator, the eccentric vibrator generates a periodic hammering force which interferes with the angle and acceleration sensors used in conventional active rollover prevention systems.

Construction and road machines are prone to falling over because of their articulation and high centre of gravity, and the results are often fatal for the drivers. Thus, there is an urgent need for an active rollover prevention system for construction and road machinery. SUMMARY OF THE I NVENTION

The object of the present invention is to provide an active rollover prevention system for construction and road machinery that will prevent the machinery from falling over. According to the present invention there is provided an active rollover prevention system for construction and road machines, the system comprising:

(a) means for sensing the pitch, tilt and articulation angles of the machine;

(b) means for sensing the speed of the machine;

(c) means for comparing the pitch, tilt and articulation angles against pre-determined safe operating speed using an information processing unit;

(d) means for reducing the speed of the machine if it exceeds the predetermined safe operating speed for the pitch, tilt and articulation angles

(e) means for warning the driver of the machine that the machine has exceeded the pre-determined safe operating speed or angle; and

(f) means for re-positioning an attachment of the machine to a safe- operating position if the machine exceeds the pre-determined safe operating speed or angle.

Preferably, inclinometers are the means for sensors used for measuring the pitch and tilt angles.

More preferably, the front section of the machine and the rear section of the machine have separate inclinometers.

It is preferred that the pitch and tilt angle sensor readings are corrected for the effects of dynamic forces on those sensors prior to the readings use in the determination of the safe operating speed.

It is preferred that a positioning sensor is used to measure the articulation angle of the machine.

Preferably, speed sensors are used to measure the velocity of the machine.

More preferably, the front section of the machine and the rear section of the machine have separate speed sensors. Preferably the speed sensors readings are compared with the joystick positioning sensor of the machine prior to the readings use in the determination of the safe operating speed. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of a soil compactor, which is an example of a machine on which the present invention may be used.

Fig. 2 is a side view of the soil compactor of Fig. 1 shown pitched at an angle. Fig. 3 is a front perspective view of the soil compactor of Fig. 1 shown tilted at an angle. Fig. 4 is a top perspective view of the soil compactor of Fig. 1 shown articulated at various angles. Fig. 5 is a flow chart showing the operation of the active rollover prevention system for construction and road machinery according to the present invention. Fig. 6 is a graph showing the variation of the eccentric force (eforce) generated by the weight within the eccentric vibrator of the machine of Fig. 1 over one period of time. Fig. 7 is a graph showing the variation of neutral force applied by the surface to the machine of Fig. 1 . Fig. 8 is a graph showing the variation of the safe working tilt angle for a machine of Fig. 1 over with time. Fig. 9 is a graph showing the relationship between the radius of turning , the speed and the tilt angle of the machine of Fig. 1 working on positive camber. Fig. 10 is a graph showing the relationship between the radius of turning, the speed and the tilt angle of the machine of Fig. 1 working on negative camber. DETAILED DESCRI PTION OF THE INVENTION

The active rollover prevention system 20 of the present invention can be used on a machine 10 such as a Compactor which is shown in Fig. 1 .

The machine 1 0 is articulated between its rear section 12 and front section 14 which houses a drum 16 comprising a vibrator which generates a periodic hammering force to compact soil or asphalt. The drum 16 has protrusions as illustrated in Figs. 1 , 2 and 4 if compacting soil , or the drum may also be smooth as shown in Fig. 2 to compact asphalt.

The principles described in respect of the present invention may also be adapted and applied to other construction and road machines such as articulated trucks, backhoe loaders, cold planers, feller bunchers, forest machines, forwarders, hydraulic excavators, knuckle-boom loaders, material handlers, motor graders, multi terrain loaders, off-highway tractors, off-highway trucks, paving equipment, pipelayers, road reclaimers, scrapers, skid steer loaders, skidders, telehandlers, track loaders, track-type tractors, underground mining machines, wheel dozers, wheel excavators and wheel loaders.

The data which is monitored by the system 2O includes the velocity υ of the machine 10, the pitch angle tx shown in Fig. 2, the tilt angle β (also referred to as the 'oscillation' or 'roll' angle) shown in Fig. 3, and the articulation angle φ shown in Fig. 4.

Particularly in the case of Compactors which have smooth drums (such as the machine 10 shown in Fig. 3), the rollers on the rear section 12 of the machine 1 0 can spin at a higher velocity (υ_t)on a slippery section of a road, than the velocity of the rollers on the front section 14 of the machine 10 (υ₂ ) , or vice versa. The average velocity (υ_a )of U₁ and u₂ may be used in calculations.

The x-axis forces which act on the machine 10 include the radial force generated by the acceleration around the turning circle of the machine 1 0, less the neutral force in the direction vertical to the area on which the machine 1 O contacts the ground , less the sine component of the tilt angle of the force generator by the eccentric vibrator, and plus (if the machine 10 is sliding down the hill) or minus (if the machine 10 is sliding up the hill) the cosine component of the tilt angle for the static force of the friction generated between the machine 1 0 and the ground . This is shown in the equation below:

∑ F_X = M -^- — N si n β — mrω² sin(cot)si n β + f cos β

The y-axis forces which act on the machine 10 are the cosine component of the pitch angle of the force of the acceleration on the machine 10, plus the neutral force in the direction vertical to the area on which the machine 10 contacts the ground, plus the cosine component of the pitch angle of the force generator by the eccentric vibrator, and plus (if the machine 10 is sliding down the hill) or minus (if the machine 10 is sliding up the hill) the sine component of the tilt angle for the static force of the friction generated between the machine 1 0 and the ground. This is shown in the equation below:

]T) F_y = -Mg cos ex + N cos β ■+■ mrω² si n(ωt)cos β + f_μ si n β

In respect of the equation for ^ F_x and ∑ F_y :

• M = the mass of the machine 1 O (in kilograms);

• m = the mass of the weight inside of the eccentric vibrator 16;

• r = the radius of the eccentric vibrator 16;

• υ_a = the average velocity of the rear section 12 and the front section 14 of the machine 1 O;

• N = the neutral force in the direction vertical to the area on which the machine 1 0 contacts the ground ;

• R = the radius of the spiral of the machine 10 when it rolls;

• ω = the vibrator frequency of the eccentric vibrator (in radians per second);

• f_μ = static friction force of the machine 10 on the ground; • t = time (in seconds);

• p = the tilt angle of the machine 10; and

• ot = the pitch angle of the machine 1 O.

The first component of the lateral force F_x is M ^- which is the radial force on the machine 10 when turning in a circle of radius R (in metres), which is equal to the mass of the machine 1 O multiplied by its radial acceleration, and is denoted with the symbol "c" (for reasons which will become clear below) having the following equation:

The second component of the lateral force F_x on the machine 10, N si n p , is the neutral force on the ground of the machine 1 0, in a direction vertical to the ground.

The third component of the lateral force F_x , m rco² si n(cot) , is the eccentric vibrator force (denoted "eforcθ(t)"), which is equal to the mass (in kilograms) of the machine 1 0, multiplied by the radius (in metres) of the weight within the eccentric vibrator, multiplied by the square of the angular frequency (in Hertz) of the weight within the eccentric vibrator, multiplied by the sinusoidal variation of the angular frequency to (in radians per second) of the weight within eccentric vibrator, with time (in seconds).

The variation of the eccentric vibrator force on the machine 10, eforce, (which is measured in Newtons) over 0.01 5 seconds (which is equal to one period) is shown in Fig. 6, and indicates that the eccentric vibrator generates a cyclical positive, then a negative force on the machine 1 0.

The last component of the lateral force F_x , f_μ cos p , is the static friction force of the machine 10 on the ground.

The radial force and eccentric vibrator force are used in the calculation of the neutral force from the ground to the machine 10, denoted by "ΛT, which is given by the equation: , v _ - eforce(t) + ~Jeforce(tf - (μξ + iXeforceQ:)² - c² - G²)

Where:

• μ_s= the friction coefficient of the surface that the machine 10 is running on;

• c = the radial force (in Newtons);

• G = force of gravity, 9.8 metres per square second;

The variation of the eccentric force (generated by the weight within the eccentric vibrator 16 on the machine 10) with time is shown in Fig. 6, over one period.

The system 20 of the present invention is shown in the flowchart of Fig. 2.

Before feeding data to the main program 4, the data is validated (i.e. corrected for errors) using sub-programs 1 , 2 and 3.

Referring to the sub-program 1 on Fig. 5, at least one tilt sensor (also known as an 'inclination' sensor') must be used to measure the measure the tilt angle of the machine 1O. However, the centrifugal force and the sliding effect of the machine 10 may create an error within the tilt sensor. In order to find the real value of the tilt angle of the surface on which the machine 10 is running, a correction must be applied to the initial reading from the tilt sensor (B) using the formula (within sub-program 1 ) shown below: r_υ ² + R - B^i β = β_rea_dlng ± Δβ = β_readlng ± 3 rcta H^ ^a _{R g} J

Where:

• β = the tilt angle of the ground on which the machine 10 is running;

• υ_a = the average velocity of the rear section 12 and front section 14 of the machine 1O (in metres per second); • R = radius of articulation or 'turning ci rcle' of the machine 10 (in metres);

• B = the acceleration as measured by the tilt sensor (in metres per square second ); and

• g = the rate of gravity, which is 9.8 metres per square second. The plus or minus of the Δβ depends on whether the road on which the machine 1 0 is travelling has a positive or negative camber.

Some roads are not flat, but are sloped at an ang le. If the road is sloping towards the direction in which the machine 1 0 is turning, then the road has a 'positive' camber. If the road is sloping away from the d i rection i n which the machine 1 0 is turning, then the road has a 'negative' camber.

Sensors on the machine 1 O read the ti lt angle and the articulation angle of the machine 10, and then the main program 4 (shown in Fig. 5) uses these readi ngs to determine whether the road has a positive or negative camber.

' T ' is the tilt angle that the machine 1 O can at work without rol l i ng , based on the friction force of the machi ne 1 0 on the road. If the friction force on the machine 1 0 is zero, then T is also zero. It is given by the equation:

-_rf_s 180 . C N(t) • μ. ^l

T(t) = a rcta n — -^ — ^v > ^^s — _π w π ^ N(t) + eforce(t)J

Where

• μ₅ = the static friction coefficient of the surface that the machi ne 1 0 is running on.

If the road has a positive camber, then the upper tilt angle limit P₁ at which the machine 1 0 can operate is given by:

If the road has a positive camber, then the lower tilt angle l i mit β₂ at which the machi ne 1 0 can operate is given by:

P₂ = Po ^" T If the road has a negative camber, then the upper tilt angle limit β₃at which the machine 10 can operate is given by:

P₃ = -P_o + T if the road has a negative camber, then there will be no lower tilt angle limit.

Where β₀ is the tilt angle as a result of the centrifugal force applied to the machine 10 by the sloping surface on which it is running, and is given by the equation: β_Q = ^arctan|

^R g

Where:

• o_a = the average velocity of the machine 10 (in metres per second);

• R = radius of articulation or turning circle of the machine 10 (in metres); and

• g = the rate of gravity, which is 9.8 metres per square second.

Fig. 9 shows the variation of the upper tilt angle limit P₁ as a result of the addition of tilt angle β₀ (from the centrifugal force applied to the machine 1O), and the tilt angle T (as a result of the friction force), over 0.015 seconds (i.e. one period).

The tilt angle depends on the radius of the turning circle (R) of the machine 10 in metres, the speed at which the machine 10 is travelling (υ) in metres per second, and the time (t) in seconds. That is,β(R, υ, t), which is depicted in Fig. 9, where time and the radius of the turning circle are held constant in order to depict the variation of β, in two dimensions.

Fig. 9 shows that the upper tilt angle limit β_± at which the machine 10 can operate before rolling, when travelling on a road with positive camber, decreases as the speed (υ) of the machine 10 is increases. 1 O

Likewise, Fig. 1 O shows that the upper tilt angle limit p₃ (t) at which the machine 10 can operate before rolling, when travelling on a road with negative camber, also decreases as the speed of the machine 10 increases.

Referring to the sub-program 2 on Fig. 5, sensors measure the articulation angle cp (refer to Fig. 3) between the rear section 12 and front section 14 of the machine 1 O.

An articulation sensor reads the angle φ of the machine 10, however in order check that the articulation sensor is reading correctly, the system 2O checks to see if the oil pressure switch is on, which indicates that the steering is in use, and thereby that the machine 10 is articulated.

Speed sensors read the velocity on rear section 12 and the front section 14 of the machine 10. Likewise the position of the joystick of the hydrostatic drive, determines the driving speed of the machine 1 O.

Firstly, sub-program 3 (on Fig. 5) compares the velocity readings from the speed sensor, with the driving speed from the joystick of the machine 1 0, to ensure that the sensors are working accurately.

Secondly, sub-program 3 compares the speed of the roller on the rear section 12 with the speed of the roller of front section 14 of the machine 1 O, and if the speed of the roller on the rear section 12 is less than one quarter of the speed of the roller of front section 14 (or vice versa), then this indicates that one of the speed sensors is not giving accurate readings.

The absolute value of the readings of the front speed sensor and the rear speed sensor, should be less than halve of the average velocity, otherwise an error 3 occurs: ^

When error 3 occurs driver of the machine 1 0 will be alerted , and velocity signals will not be sent to the main program 4. The pitch sensor will provide inaccurate read i ngs when the machine 1 0 is accelerati ng or decelerati ng , or going uphill or downhi l l . Micro-switches within the joystick of the hydrostatic d rive detect whether the machine 10 is moving forward and in reverse. The change in velocity over time wi l l determi ne whether the machine 10 is accelerati ng or decelerating .

Thirdly, sub-program 3 corrects the pitch sensor readings using the fol lowing equation:

α = "reading ± Atx = cx_readiπg ± arcta n ^a-

Where:

• o = the first differential of the average velocity (or acceleration); and

• g = the rate of gravity, which is 9.8 metres per square second .

The mai n program 4 then compares the velocity sensor readings U₁ and υ₂ to see if they are greater than the critical lateral sliding velocity υ_c at which the machine 10 is likely to rol l .

If the velocity sensor read i ngs for U₁ and υ₂ are greater than the critical lateral sliding velocity υ_c , then the data is transferred to the controller 5.

If XJ₁ and \J₂ have reached the critical velocity, then the controller 5 sends a sig nal for the machine 1 0 to be put i n drive limp mode 9 , in which the machine 10 slows to down to a crawl.

If O₁ and VJ₂ reach the danger velocity, then the control ler 5 sends:

• a warning signal 6 to the driver of the machine 10,

• a signal to the drive control unit 7 to reduce the speed of the machine 1 0,

• a signal to the attachment control unit 8 to turn the attachment off, For instance, i n the case of the compactor, the attachment is the eccentric vibrator, and in the case of a loader the attachment is the bucket. If the height of the bucket is reduced the centre of gravity of the machine 1 O is also reduced , which i n turn reduces the chance of a rol lover. If υ_x and υ₂ reach the danger velocity and the driver sharply turns the steering of the machine 1 0, then the drive limp mode 9 will automatically come into effect.

Claims

CLAIMS:

1 . An active rollover prevention system for construction and road machines, the system comprising :

(a) means for sensing the pitch, tilt and articulation angles of the machine;

(b) means for sensing the speed of the machine;

(c) means for comparing the pitch, tilt and articulation angles against predetermined safe operating speed usi ng an information processing unit;

(d) means for reducing the speed of the machine if it exceeds the predetermined safe operati ng speed for the pitch, tilt and articulation angles

(e) means for warning the driver of the machine that the machi ne has exceeded the p re-determined safe operati ng speed or angle; and

(f) means for re-positioning an attachment of the machine to a safe- operating position if the machi ne exceeds the pre-determined safe operating speed or angle.

2. A system according to clai m 1 , wherei n inclinometers are the means for sensing used for measuring the pitch and tilt angles.

3. A system according to claim 2, wherei n the front section of the machine and the rear section of the machine have separate inclinometers.

4. A system accord ing to claims 3, wherei n the pitch and tilt angle sensor readi ngs are corrected for the effects of dynamic forces on those sensors prior to the readi ngs use in the determination of the safe operati ng speed.

5. A system accord ing to claim A-, a positioning sensor is used to measure the articulation angle of the machine.

6. A system according to claim 5, wherein speed sensors are used to measure the velocity of the machine.

7. A system according to claim 6, wherein the front section of the machine and the rear section of the machine have separate speed sensors.

8. A system according to claim 7, wherein the speed sensors' readings are compared with the joystick positioning sensor of the machine prior to the readings use in the determination of the safe operating speed.