Turning Safety Research of Concrete Mixer Truck Based on Lab VIEW

Turning Safety Research of Concrete Mixer Truck Based on Lab VIEW

SUN Guan-long, CAO Yuan-wen, LI Bang-quan,

Department of Mechatronics & Automotive Engineering, Chongqing Jiaotong University, Chongqing 400074,China

Abstract–According to the analysis of concrete mixer trucks stability, a theoretical calculation method is come up with, which can calculate its safety speed when turning. In addition, the paper put forward building a program graph of the system that can compute real-time safe velocity and designing a corresponding front-panel diagram, based on the virtual instrument software environment of LabVIEW. And the system has safety alarm function for mixing truck driving, as well.

Keywords: safety speed; real-time; LabVIEW; virtual instrument

1. INTRODUCTION

   The increasing number of cars leads to a lot of traffic problem. Especially those accidents caused by concrete mixer truck rollover would bring huge property losses and serious security threats to life. The concrete mixer trucks are prone to roll because of its high center of gravity, poor stability, and complex road condition and so on. Among them, the high-speed turning condition is one of the most risk factors for rollover. In order to determine the concrete mixer truck's turning speed, the driver has to only depend on the familiarity with its performance. In view of this

   model is established to analyze the critical speed for rollover. As shown in figure 1, the model includes the lateral movement along the y direction, the horizontal pendulum movement around the z axis and lateral movement around the x axis.

   Figure 1. Concrete mixer truck rollover model.

   1

   The model can get the following dynamics equations, balance equation along the Y axis movement:

   situation, it is necessary to propose a virtual instrument design which can reckon the real-time safe speed. And the

   mV mh h 2F

   cos 4Fm

   4F

   (1)

   r

   f

   safe speed is also able to be displayed on the panel, giving

   balance equation around the z axis movement

   the driver a timely and scientific reference standard. If the driver didn't limit the velocity to the safe velocity, the

   I z 2aFf

   • 4bFm

   • 4cF

   (2)

   system will alarm at the same time, prompting the driver to

   slow down, so as to ensure traffic safety.

   balance equations Around the x axis movement

   I mh h V mgh k c

2. CONCRETE MIXER TRUCK ROLLOVER

   x 1

   (3)

   Among them

   MODEL

   Ff k f ; Fm km 2

   ; Fr

   k 3 ;

   The vehicle rollover refers to the driving car rotates 90

   or larger angle around its longitudinal axis, so that the body

   1 v f ; 2 v m ;

   could contact the ground[1].The fundamental reason for

   3

   v

   rollover is that the cars lateral acceleration exceeds the limit which lateral load can compensate

   Therefore, its essential to establish an appropriate rollover kinetic model [2], in order to better study the concrete mixer trucks safety speed when turning. In this paper, the simplified linear three degrees of freedom vehicle

   In the formulas: the front wheel steering angle;

   the side-slip angle of center of mass for concrete mixing transporter; yawing angular velocity;

   the body roll angle; , b , c the distance from the center of mass to the front axle, middle axle and the rear

   axle; F , F , F the cornering force of the front wheel,

3. MAIN TITLE

   1. The determination of turning radius

      f w r

      middle wheel and the rear wheel; 1 , 2 , 3 the side-slip angle of the front wheel, middle wheel and the rear wheel; k f , km , kr the cornering stiffness of the front wheel,

      The distance from the steering center to the point of the outside steering wheel contacting with the ground is called turning radius.

      In an ideal situation:

      middle wheel and the rear wheel; suspension roll angle;

      k stiffness of the

      R L

      sin

      (8)

      h the distance from center of mass for the curb weight of

      agitation tank to the ground; p the distance from roll center to the ground; I Z the yawing moment of inertia; I x the rotational inertia of the sprung mass around the x axis; K wheel tread; f , m , r influence coefficient of roll motion of the body; O1 unsprung mass centre; O2

      the projection of unsprung mass centre

      In order to better study the rollover stability of the concrete mixing transporter, the roll model ignores the deformation of tires and the variation of roll angles, but considering the changes of suspension. And LTR [3] a rollover coefficient is introduced. LTR is the ratio of load difference between left tire and right tire to total load.

      Thus, it is not hard to draw the corresponding turning radius in the moment of the mixers turning, as long as the outside steering wheel deflection angle is known. In fact, there is a certain relationship between both sides of the steering wheel deflection angle. As shown in the figure2:

      LTR

      FZL FZR

      (4)

      FZL FZR

      Figure 2. The ideal relationship between the deflection angles of the steering wheels on both sides

      In the formula (4): FZL , FZR left side, right side of the front and rear wheel of the total vertical load.

      When LTR is equal to 0, the vertical load on both sides of tires is the same, and it shows that the mixer truck rollover will not occur at this moment; while LTR is equal to 1, the vertical load on one side of tires is zero, and it means this side of tires get off the ground, so the vehicle rollover may occur in this case. Due to the moment balance, the torque acting on O2 is balance, thus, the following

      outside steering wheel deflection angle; inside steering wheel deflection angle.

      And an angle sensor is fixed on the king pin of the mixer

      truck steering wheel on the right side, so that the value of

      can be received at any time. Now, is outside steering

      wheel deflection angle, however, when the mixer truck turns right, is inside steering wheel deflection angle. As the

      car makes a turn, the inside and outside steering wheel angle satisfies Ackerman principle, namely:

      formula (5) can be obtained.

      cot cot K

      9

      1. KF 1 KF m a h m gh h tan 0

         (5) L

      2. ZL 2 ZR 1 y 1 1

      In the formula (9): outside steering wheel

      a y is the centrifugal acceleration of circular motion.

      V 2

      deflection angle; inside steering wheel deflection

      angle; L wheelbase; K wheel tread;

      ay R

      (6)

      With the value of received by the angle sensor and the calculation of Ackerman principle, the value of is

      As LTR is equal to 1, the mixer truck rollover will occur.

      And the following equation is able to be got by formula (5) and (6).

      able to be computed, so as to calculate the corresponding turning radius.

      Due to the characteristics of steering trapezoidal

      VC

      RmgK 2Rm1 g h p

      2m1h

      tan

      (7)

      mechanism as well as the requirement of performance of vehicles, there will be a certain error between the actual angle and Ackerman angle. Moreover, different types of

      In the equation (7): m the total mass of the concrete

      mixer truck; m1 sprung mas; R turning radius of the vehicle;Vc the critical speed of rollover.

      cars are slightly different. At present, because the turning speed of the car is not high, the actual angles of inside and outside conform to this principle [4], broadly. Article 4.1.15 of China's automobile industry standard QC/T667-2010, experimental method and technical condition of concrete

      mixing transporter , specified: when concrete mixer truck drives with mixing, its maximum speed is not more than 50Km/h. So the speed is far lower than the highest speed in the turning condition and the requirements of the Ackerman theorem is apparently satisfied.

   2. The determination of preliminary angle

   The bend road refers to the center line in the state of the curve, and its size is measured by radius of the bend. Because many accidents happen on the corner, it is dangerous to get through the corner. When the car get into

   the corner for a short distance or is greater than a certain

   value, the outside steering wheel deflection angle would be calculated at . This will eliminate the error of the response lag and actuator, so that the truck mixer is able to be in a safety state in advance. And is the preliminary angle. As shown in the figure3:

4. THE ANALYSIS OF THE ENGINEERING

   EXAMPLE

   Take a real full-loaded concrete mixer truck as the analysis of example to illustrate, and some related parameters are shown in table 1:

   Total mass(kg)	m	25000
   Sprung mass(kg)	m1	22000
   Body roll angle		15
   Mass centre to the ground distance(mm)	h	1806
   Roll center to the ground distance(mm)	p	735
   Wheelbase(mm)	L	4535
   Wheel tread(mm)	K	2065

   Table 1. Partial correlation parameters of mixer truck

   Figure 3. Schematic diagram of Preliminary angle

   Based on the above theoretical analysis, the safe speed of B is less than the safe speed of A. When the concrete mixer truck drives at point A, the system begins to calculate

   For the convenience of calculation, it is assumed that the

   value of is 14 and is 10 . When the concrete mixer truck turns left, is the outside steering wheel deflection angle.

   L

   the safe speed of point B. At this moment,the driving speed

   Turning radius: R

   (10)

   should be less than or equal to the safe speed of A. In this

   way, as the truck really reaches the rolloverprone point B, its rate has been already in the safe speed of B, thus, concrete mixer truck rollover in dangerous turning condition can be prevented effectively.

   max

   In general, the maximum angle of automobile steering wheel is about 40 [5], so, in this paper is regarded

   Put the relevant parameters into equation (10) and figure

   out that R is 11.15m . While the concrete mixer truck turns right, is the inside steering wheel deflection angle.

   According to cot cot K , 12.6 , R is equal

   L

   to 11.79m this time. As the full-loaded truck takes a left

   as 45 . When concrete mixer truck drives in the small curves and straight line, avoiding pedestrians or other

   turn,

   VL is

   1. km

      h

      by the previous formula (7) and

      vehicles, the steering wheel deflection angle is small, usually within10 . In that condition, the speed of the mixer

      related data. And

      similarly. Thus:

      VR 27.9kmh

      can be computed

      truck is within the stipulated, however, the safe speed of the

      car which drives in the large corner is the real focus. Therefore, the starting angle is considered as10 . That is when the outside steering wheel deflection angle is bigger

      The critical speed of the rollover of left turning:

      VL 26.4kmh

      The critical speed of the rollover of right turning:

      than 10 , the safe speed is calculated. Thus, 10 is

      V 27.9km

      temporarily regarded as the basis of theoretical research in this paper, according to the experience and comprehensive factors.

      R h

      But now, there is still no specific provision about the value of the safety speed. It is suggested that VS , safe

      velocity, should be looked upon as 76 VC according to the golden section method.

      Namely: VS 76 VC

      In conclusion:

      The full-loaded trucks safe speed of left turning: VSL 20.1kmh

      The full-loaded trucks safe speed of right

      turning: VRL

      20.6kmh

      Based on the above theoretical calculation and analysis of a real concrete mixer truck, a virtual instrument is designed, under the Labview software environment. The virtual instrument can compute the real-time safe speed in the process of trucks turning. And this virtual instrument also includes design of the front panel and construction of the program diagram. The front panel comprises setting- parameter button, control button, displaying-data button and so on. The structure of program diagram needs thoughtful calculation process and logical relationship, and it verifies its correctness through the form of data stream. If a little mistake takes place in the program, the data stream would be stopped, and the whole process will not be able to run, so the data won't be displayed on the front panel.

      In the display interface of the virtual instrument, parameters can be set based on different types of concrete mixer trucks. The following diagram is the front panel of the full-loaded trucks right turning.

      Figure 4. Front-panel diagram of right turn truck with full load

      This moment, the driving speed of 20kmh is less than the safe speed of 20.6kmh , so the car is in the safety condition, and the indicator doesnt alarm, appearing as dark The following figure 5 is the corresponding program

      diagram of right turn truck with full load.

      Figure 5. Program diagram of right turn truck with full load

5. CONCLUSION

1. According to the analysis of full-loaded concrete mixer trucks roll stability, a method is summed up to calculate the safe speed in its turning condition.

2. On the basis of an engineering examples analysis in LabVIEW software development environment, the theoretical calculation of safe speed and the warning system are designed.

3. The virtual instrument can completely satisfy various computational requirements of the theoretical analysis, in accord with the results of theoretical calculation. With angle sensor, speed sensor, and weighing sensor, the instrument can intelligently display the real-time safe speed of the car in cornering, and determine whether the vehicle is in the safe speed condition. Thus, were able to ensure the concrete mixer trucks driving safety when turning through the virtual instrument.

REFERENCES

1. Yu Zhisheng, Automobile theory, China Machine Press, eijing, 2006.

2. Ni Feifei, Research of concrete mixing vehicle rollover early warning technology, Journal, Technic Forum, 2013 (9):82- 84.

3. Xu Yanhai, A study on vehicle rollover avoidance control based on active steering technique, Journal, Automotive Engineering 2005, (5): 518-521.

4. QC/T 667-2010 Automobile industry standard of the People's Republic of China, Standardization, China Planning Press, 2010.

5. Hao Rulin, Chen Xiaochun Experimental study on the matching design of steering system, Journal, Automation of Electric Power Systems, 2009, ( Z1 ): 9-10.