| Heavy duty semi-trailer has played an important role in national economy and it has great potential development. But it has some shortcuts, such as a high center of mass, long body, big volume, towed mass varying frequently and the effect at the hinge point between two rigid bodies. These weakness induces the discordance between a motor tractor and its trailer and the discordance leads to some dangerous accidents, such as rollover, swing vibration, etc. Taking the above into consideration, the safe driving of a heavy duty semi-trailer has been one of bottlenecks preventing automotive industry and transporting industry developing.Based on National Natural Science Foundation of China multi targets control of heavy duty semi-trailer dynamics stability(No.51075176), and Jilin province science development project the development and match of electrically controlled air braking system in a heavy duty semi-trailer(No.20150204066GX),this paper makes a research about the above safe problems. After searched research results in the field of heavy duty semi-trailer with loaded solid cargo, the paper built a simplified model and estimating its state parameters to improve vehicle active safety. Besides, the paper designed rollover warning algorithm and multi targets stable control strategy based on prediction model. At last, the paper used commercial vehicle Electric Brake System(EBS) Hardware-in-Loop(HIL)test platform to verify the designed control strategy.The paper mainly includes the following several parts:Firstly, according to limitations of heavy duty semi-trailer rollover warning and stable control, the paper built a three-axle five-degree-of-freedom(DOF) reference model and a three-axle 3-DOF reference model. Then by the means of double models and Double Unscented Kalman Filter(DUKF) technology, the paper estimated the main state parameters. Model input is steering wheel angle and output is vehicle speed. First, the yaw, lateral acceleration and the three axles cornering stiffness of the 3-axle 3-DOF reference model of tractor and semi-trailer were estimated. Then these estimated parameters were input into 5-DOF and 3-DOF simplified DUKF algorithm, input three axles cornering stiffness into 3-DOF model DUKF algorithm in order to estimate a series of yaw, side slip angle and 3-axle cornering stiffness. 5-DOF DUKF algorithm is used to estimate roll angular velocity, yaw, rollover angle, every suspension cornering stiffness and another series of side slip angle and yaw. Then input these above state parameters into integrated system to compute the weighted average of side slip angle and the result is the estimated output.After verifying the output results through simulated tests, the paper verified that the designed model and algorithm could satisfy roll stability warning and multi targets control and ensure the model precise, which makes a foundation for vehicle stability control research in the future.Secondly, based on 5-DOF reference model, and roll angle of tractor and semi-trailer computed by DUKF, the model being precise. the paper built rollover warning algorithm according to the Rollover Indicator(RI) of tractor and semi-trailer. Based on the roll stiffness of tractor and semi-trailer, the paper set different roll over thresholds. The time- to-rollover(TTR) was optimized by T-s Fuzzy Neural Network algorithm that can improve output accurate of warning time.The paper used dynamics warning rollover indicators from the warning algorithm to calculate dynamics warning rollover indicators at the present moment. With the help of Double Lane Change(DLC) simulated tests and Fishhook simulated tests, tractor and semi-trailer rollover warning algorithm could predict vehicle future precisely in order to make sure that rollover warning algorithm is real time.Thirdly, if rollover warning system did not function, the vehicle will drive itself into limiting conditions. That will induce vehicle shimmy, collapsing, rollover and other dangerous conditions. In order to prevent the above conditions happening, this paper proposed a heavy duty semi-trailer multi targets control strategy based on model prediction control. This algorithm controlled the yaw of tractor and semi-trailer and adopted differential braking to control. With taking the side slip angle and yaw rate of 5-DOF reference model as the expected value, it becomes possible to control the output state of 3-DOF model follows the output state of 5-DOF model with the model predictive controller. On this basis, the yaw stability control torque of tractor and semi-trailer can be obtained firstly. Subsequently, the brake wheel and brake torque and the braking pressure can be calculated by the Braking force distribution module and Brake inverse model respectively.DLC simulated tests on high and low adhesion road makes it clear that heavy duty semi-trailer is easy to rollover without control, but the stability control strategy based on predicted model could actively prevent vehicle rolling, yawing and collapsing.At last, based on the above researching route, the paper used HIL test platform in my team to do experiments. The test platform linked its two software systems through HIL development instrument, namely Lab VIEW. Lab VIEW is used to invert and transmit data. In these experiments, the paper adopted high speed, from high adhesion to low adhesion. The results indicated that semitrailer has a better path following ability, yaw stability and anti-rollover stability.In conclusion, this paper has acquired innovative achievements and they are showed as following:(1)This paper established 5-DOF and 3-DOF models of heavy duty semi-trailer and used DUKF to estimate. 3-DOF model has two rolling rigid bodies less than 5-DOF model. The estimated strategy used real steering wheel angle as input and its output is speed. The estimated cornering stiffness of three axles from 3DOF model is transmitted to DUKF. Then DUKF estimated two series of state parameters based on 5-DOF and 3-DOF model, respectively. At last, the two series of state parameters are input into integrated system to calculate weighted average of side slip angle.(2)Heavy duty semi-trailer warning algorithm is based on LTR of tractor and semi-trailer. Vehicle state parameters are from DUKF estimation, which makes model more precise. So the model could estimate vehicle state precisely in the future and ensure that rollover warning algorithm is real time.(3)In order to solve heavy duty semi-trailer rollover, shimmy and collapsing, the paper proposed heavy duty semi-trailer active control algorithm based on multi targets stability control. The algorithm could improve roll stability, yaw stability and collapsing stability of heavy duty semi-trailer. The conclusion is also verified by many experiments on commercial vehicle EBS test platform. The results on the test platform make it clear that the controller could improve path following ability, yaw stability and anti-rollover stability of semi-trailer. |
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