It is different for the liquid tank semi-trailer to keep roll stability during turning or emergency voidance, and that may cause serious accidents. Although the scholars did lots of research about the roll stability of liquid tank semi-trailer in theory by calculating and simulation, how to make an effective early warning of rollover is still unsolved in practice. The reasons include the complex driving condition and the difficulty of the vehicle parameter obtaining. The feasible method used currently is evaluating the roll stability of a liquid tank semi-trailer by the lateral acceleration or the attitude of the vehicle. Unfortunately, the lateral acceleration is more useful for sideslip rather than rollover, and the attitude is a kind of posterior way, which means it is hard to take measures to cope with the rollover accident when the attitude exceeds the safety threshold. Considering the movement of the vehicle is totally caused by the wheel force, the rollover could also be predicted by the changing of the wheel force. Therefore, in this paper, we developed a method to analyze the roll stability by the vertical wheel force. A thorough experiment environment is established, and the effectiveness of the proposed method is verified in real driving conditions.
The liquid tank semi-trailer has become the main carrier for liquid chemical products transportation, because of the large transportation capacity and low transportation costs [
Like the ordinary heavy-duty semi-trailers, the liquid tank semi-trailer has a high center of gravity, a large load, a narrower track relative to the height of the vehicle, and a coupling effect between the tractor and the trailer [
What’s worse is that the liquid in the tank has no definite shape and is fluid during driving [
Therefore, to intervene the vehicle effectively before a rollover accident occurs, it is necessary to evaluate the roll stability of the liquid tank semi-trailer during driving by the vehicle dynamic parameters sensing. The rest of this study is organized as follows. Section 2 analyzes the dynamic model in the rollover processing and the proposed evaluation standard. Section 3 describes the design details of the vertical wheel force acquisition equipment, which is indeed a specially manufactured wheel force sensor. Section 4 introduces the test equipment for the actual vehicle experiment, including the distribution of the sensors and the protective equipment, and the experiment results of the real liquid tank semi-trailer are also shown in this section. At last, Section 5 concludes the paper.
The roll dynamics model is essential to study the vehicle roll phenomenon. Considering that the roll of the trailer part is the main form of the vehicle roll, and the rear axle of the trailer is the dangerous point of the vehicle roll instability, the rear axle of the trailer is selected to establish the roll dynamics model in this paper, as shown in
The states in
During the driving of the vehicle, even if there is a center of gravity deviation or lateral acceleration, as long as the road surface can provide sufficient support to balance the roll torque generated by the above situation, the vehicle will not roll over. A large number of simulations and experiments show that rollover accidents usually occur when the balance torque provided by the road surface is insufficient. Therefore, the rollover coefficient
Where
Because the vertical wheel forces are hard to be obtained in real time, they are often estimated by using the roll dynamics model shown in
Furthermore, Assuming
Unfortunately, for the liquid tank semi-trailer, the liquid in the tank might shake during the driving condition, which causes the position of the center of gravity of the tank to change. That means the parameter
The wheel force sensor could measure various forces between the wheel and the road and of course, it has to be installed on the wheel itself. Since the wheel is rotating during driving, there is a difference between the sensing coordinate and the calculating coordinate of the wheel force. To deal with this problem, two coordinates are defined, respectively in
In
It is worth to note that these two coordinates completely coincide at the beginning, then as the wheel rotates, the coordinate {
In the scene that this paper is concerned about, the measurement of vertical force is essential [
In order to sense both vertical and longitudinal wheel forces, a spoke elastic body is designed as in
The division of strain gauges on the strain beams is shown in
The wheel force information collected by the wheel force sensor will be wirelessly transmitted to the processing terminal on the trailer
In order to test the actual effect of the trailer rollover stability analysis method used in this paper, on the premise of ensuring the safety of personnel, a liquid tank semi-trailer is modified according to the method shown in
First of all, an anti-rollover bracket is fixed on both sides of the tank. This bracket could provide effective support when the trailer is about to roll over, thereby avoiding accidents and ensuring the safety of the driver. Then the active suspension is equipped to adjust the pressure of the hydraulic lever, so that the trailer can regain its balance when a roll is about to occur. This active suspension can reduce the risk of rolling effectively, and its control signal could also be used to verify the analysis results of rollover stability based on wheel force. At last, two sets of sensors are installed to obtain the driving information of the semi-trailer. One is the high-precision inertial measurement unit (IMU), and the other is the wheel force sensor. The IMU is put on the middle of the trailer and is used to sense the three-axis acceleration and angular velocity. The Wheel force sensors are installed on the last axle of the trailer to measure the longitudinal and vertical wheel forces on the left and right sides, since the research shows that the last axle is where the rollover often occurs.
The half-load steady state rotation test, which is widely used in the roll stability analysis, is carried out to compare the three stability criteria of wheel force, lateral acceleration, and roll angle. To ensure safety, the professional vehicle test site and experienced drivers are selected to carry out the dangerous test. The trailer trajectory of the test which consists of three intact left and right turns, is shown in the
The wheel forces and vehicle speed in the half-load steady state rotation test are shown in
The comparison of the three roll stability criteria including wheel force, lateral acceleration, and roll angle are in
The steering brake test is highly dangerous since the speed of the trailer is higher, and the brake pedal needs to be depressed while turning [
The rollover stability analysis is crucial for the liquid tank semi-trailer to guarantee the safety of the driver and the equipment. Compare with the lateral acceleration and roll angle, the rollover coefficient
This work was supported by the Suzhou Key industrial technology innovation project SYG202031.