Hitch Angle Research Articles

Robust Lane Keeping Control for Tractor With Multi-Unit Trailer Under Parametric Uncertainty

In this paper, a lane-keeping system is proposed for the tractor with two articulated trailers. For Tractor with Multi-Unit Trailer (T-MUT) vehicles, the motions of each unit of the vehicle are quite different from those of ordinary single-unit vehicles. Based on the dynamic model of the T-MUT vehicle, the lane-keeping control system of a T-MUT vehicle is designed with Model Predictive Control (MPC). In order to consider the uncertainty of the weight change at each trailer, a model uncertainty analysis is performed through the transfer functions for each hitch angle. For lane-keeping performance, the geometry constraints on each unit of the T-MUT vehicle are described to prevent the vehicle from lane invasion. Also, by applying the constraint tightening method to the output of the controller, a robust MPC is designed against model uncertainty, such as weight changes at each trailer. The performance of the proposed controller is validated in simulations with various curvature scenarios.

Automotive Radar-Based Hitch Angle Tracking Technique for Trailer Backup Assistant Systems

We propose a technique for trailer angle detection (TAD) for use in advanced trailer backup assistance system (TBAS) for semi-autonomous or full-autonomous backup maneuver. TBAS incorporates a combined trailer-tow-vehicle kinematic model, which is requires an estimate of the hitch angle. The proposed radar-based TAD model, for the estimate of the hitch angle, processes reflections acquired from the mmWave radars situated at the rear side of the vehicle, to detect the trailer and track its orientation in relation to the tow-vehicle. This technique is based on the tracking of individual points in the merged radars point-cloud. Each tracked point is considered as a hitch angle estimator. Using the current and past position information of a point, the model estimates the current hitch angle. To offer an accurate and reliable estimation for the hitch angle, the model fuses the estimated hitch angle by all estimators, as well as the yaw rate of the vehicle. To track each individual radar point, the model employs the extended Kalman filter, which is robust to the noisy radar measurements. In the presence of strong and persistence reflections from the trailer, the model can track the trailer successfully and return the hitch angle with a reliability measure equal to 90%.

Hybrid State Observer Design for Estimating the Hitch Angles of Tractor-Multi Unit Trailer

In this paper, a new approach of state observer is proposed for the tractor with multi unit trailers. In the case of tractor with two articulated trailers, the dynamic characteristics of the trailers are dominantly determined by the two hitch angles connecting each trailer. A novel estimation system for the hitch angle is introduced by combining the Kalman filter with the deep learning network and transfer function techniques. The Gated Recurrent Unit (GRU) network is constructed to calculate hitch angles and these values are used as the virtual measurement in the Kalman filter. The dynamic characteristics of two trailers with respect to the hitch angles are expressed as the transfer function models and these models are used to calculate the hitch angles as the virtual measurement. The virtual measurements from the two methods are integrated separately into the Kalman filter design. The estimation performance of the hitch angle with the proposed hybrid observer is validated in simulations with various curvature scenarios.

Study on path planning and tracking algorithm for autonomous parking system of semi-trailers

Semi-trailers have the advantage that the maximum load capacity is large. However, there are some problems that high driving skill is required because it is necessary to perform unique steering during turning or backward driving. This paper proposes a path planning and tracking algorithm for autonomous parking of semi-trailers. The path planner determines the parking path to the target parking position in accordance with the given parking environment including obstacles. Furthermore, the steering control system is desinged to handle the path tracking and stabilize the hitch angle. The proposed path planning method and tracking control are both unique in that it focuses on the vehicle’s terminal state at the target parking position, and finds the solution in the time-inverse order of the actual driving sequence. The parking simulations is performed and the effectiveness of the proposed method is verified.

An Intrinsically Stable MPC Approach for Anti-Jackknifing Control of Tractor-Trailer Vehicles

Tractor-trailer vehicles are affected by jackknifing, a phenomenon that consists in the divergence of the trailer hitch angle and ultimately causes the vehicle to fold up. For the case of backward motions, in which jackknifing can occur at any speed, we present a control method that drives the vehicle along generic reference Cartesian trajectories while avoiding the divergence of the hitch angle. This is obtained thanks to a feedback control law that combines two actions: a tracking term, computed using input–output linearization, and a corrective term, generated via IS-MPC, an intrinsically stable MPC scheme which is effective for stable inversion of non-minimum phase systems. The successful performance of the proposed anti-jackknifing control is verified through simulations and experiments on a purposely built one-trailer prototype. To show the generality of the approach, we also apply and test the proposed method on a two-trailer vehicle.

On nonlinear model predictive direct yaw moment control for trailer sway mitigation

In car–trailer combinations, the hitch angle is the relative yaw angle between towing car and trailer. The literature has shown that the inclusion of the hitch angle measurement for the feedback control of trailer oscillations can bring safety benefits, compared with conventional trailer sway mitigation algorithms based on the yaw rate of the car. Given the nonlinearity of the vehicle system in the typical conditions requiring the hitch angle control function intervention, nonlinear model-based controllers could be an effective solution. This paper presents four real-time implementable nonlinear model predictive control (NMPC) formulations, using the hitch angle measurement for the torque-vectoring (TV) control of an electric front-wheel drive car towing a trailer. The simulation results show that: (i) the active safety is enhanced by the proposed NMPC TV formulations, with respect to a benchmarking NMPC TV controller only based on the control of the towing car; (ii) the NMPC formulations that directly constrain the hitch angle error, or perform continuous hitch angle tracking, outperform those that modify the reference yaw rate or yaw rate error based on the hitch angle error; and (iii) the NMPC approaches including a dynamic model of the trailer are robust with respect to variations of trailer parameters.

State Estimation and Application of the Hitch Angle of a Semitrailer Train Under Full Working Conditions Based on Multimodel Information Fusion

Considering that the traditional estimation method for the hitch angle of a semitrailer train easily fails in high-speed driving and reversing conditions, this study theoretically determines that the root cause is the nonlinear disturbance. Moreover, this study analyzes the difference in nonlinear disturbance produced by a state estimator under two conditions. The criteria for the nonlinear disturbance of the estimator are determined on the basis of the analysis. With such criteria and different types of nonlinear disturbance, an estimation strategy for multimodel information fusion under all working conditions is proposed to accurately estimate the classification of forward low-speed, high-speed, and reverse conditions. A genetic algorithm is used to optimize the proposed state estimation algorithm, which improves the accuracy at a low speed and the antinoise capability of high-speed driving and reversing. The estimation strategy for different speeds and ranges of the hitch angle is simulated and verified through the cosimulation of TruckSim and MATLAB/Simulink. Lastly, the state estimation strategy is used in the application layer to design a model predictive linear reversing controller for a semitrailer train to verify the improvement of the control effect of the estimation strategy. Simulation results show that the proposed multimodel information fusion estimation strategy can accurately estimate the hitch angle under all working conditions and greatly improve the control effect of linear reversing trajectory tracking of a semitrailer train in the application layer.

자율주행 Tractor – Trailer 의 후진 직각주차 System 을 위한 경로 및 제어 Algorithm 개발

Driving a trailer forward is not difficult. However, it is challenging to drive in reverse due to the parking characteristics as the trailer turns opposite to the steering direction of the vehicle. This paper proposes an improved method to reverse-drive a trailer into a parking space autonomously. Since the existing method used only the hitch angle to control the trailer, oscillations and unstable command values were calculated. In this paper, the trailer is autonomously parked using a simple pure pursuit tracking algorithm without requiring additional infrastructure. The proposed method enables the trailer to detect the parking location and auto-park without any input from the driver.

Coupling analysis of transient aerodynamic and dynamic response of articulated heavy vehicles under crosswinds

Vehicle aerodynamics and dynamics in gusty crosswind conditions are of increasing significance for the lateral stability of heavy ground vehicles, especially articulated heavy vehicles (AHVs). The unsteady aerodynamic loads acting on AHVs can greatly exceed loads of a single-vehicle unit; these may deteriorate the lateral stability and lead to a loss of handling control. In this study, the time characteristics of aerodynamic loads and dynamic response of a tractor semi-trailer were considered, based on simulating the relative motions of these two components to reproduce actual scenarios of AHVs in crosswinds. A dynamic fully coupled method was developed and adopted to realize a real-time data exchange of flow fields and multi-bodies. Two multi-body systems (for non-articulated heavy vehicles and AHVs, respectively) were created to study the influences of the relative motions on the aerodynamic performance and lateral stability of the vehicles. The Reynolds-averaged Navier–Stokes (RANS) method and renormalization group (RNG) k−ε equation were adopted to account for the turbulence. A wind tunnel experiment was conducted to validate the numerical method. The results show that AHVs are more sensitive to the crosswind, with significant differences in the magnitudes and directions of the aerodynamic forces, moments, dynamic yaw angle, and lateral displacement. Three different wind types were considered (step, linear, and sinusoidal). The step crosswind produces the largest average lateral force and yawing moment, resulting in the largest lateral displacement and yaw angle. The largest hitch angle is found for linear gusts, presenting the highest safety risks in regard to jackknifing and trailer swings.

Hitch Angle Estimation of a Towing Vehicle With Arbitrary Configuration

In this paper, ultra-sonic sensors along with kinematics and dynamics equations of a towing vehicle are used to develop three approaches for hitch angle estimation. The first approach is based on direct calculation of hitch angle using certain a priori geometric information and distance measurements of four ultra-sonic sensors. An angle estimate is generated for each of the six possible sensor-pair combinations, and these six estimates are passed through a voting algorithm to produce a single estimate. As the second and third approaches, kinematic and dynamic models of the tractor-trailer system are used to develop least-squares and Kalman filtering based recursive hitch angle estimations. A more reliable hitch angle estimation scheme is then proposed as the integration of the algorithms developed following each of the three approaches via a switching data fusion logic. It is shown that the proposed integrated hitch angle estimation scheme can be used for any ball type box trailer with a flat or symmetric V-nose frontal face without any priori information on the trailer parameters. Based on the validity of the assumptions, the proposed scheme can estimate the hitch angle in both low-speed using the kinematic model, and high-speed using the dynamic model of the tractor-trailer system. Experimental results corroborate the algorithms in estimating the hitch angle estimates in various cases conducted in this study.

Analytical Study on the Cornering Behavior of an Articulated Tracked Vehicle

Articulated tracked vehicles have been traditionally studied and appreciated for the extreme maneuverability and mobility flexibility in terms of grade and side slope capabilities. The articulation joint represents an attractive and advantageous solution, if compared to the traditional skid steering operation, by avoiding any trust adjustment between the outside and inside tracks. This paper focuses on the analysis and control of an articulated tracked vehicle characterized by two units connected through a mechanical multiaxial joint that is hydraulically actuated to allow the articulated steering operation. A realistic eight degrees of freedom mathematical model is introduced to include the main nonlinearities involved in the articulated steering behavior. A linearized vehicle model is further proposed to analytically characterize the cornering steady-state and transient behaviors for small lateral accelerations. Finally, a hitch angle controller is designed by proposing a torque-based and a speed-based Proportional Integral Derivative (PID) logics. The controller is also verified by simulating maneuvers typically adopted for handling analysis.

Linear reversing control of semi-trailer trains based on hitch angle stable and feasible domain

A linear reversing control strategy based on the stable and feasible domains of a hitch angle is proposed to address the linear reversing problem with expectation caused by unstable open-loop conditions of semi-trailer trains during reverse driving. In the reversing process, the coupling relationship amongst the location parameters, such as hitch angle, semi-trailer posture angle and axis offset, including the influence of these parameters on the reversing stability and feasibility of semi-trailer trains, is analysed. The stable and feasible domains of the hitch angle when the semi-trailer is reversed in an expected straight line are determined. Based on this, the semi-trailer linear reversing control strategy is established. The tracking control of the linear reversing path is adopted by the variable universe fuzzy control, and the co-simulation based on ADAMS and MATLAB/Simulink and the subsequent actual vehicle experiment are conducted. Simulation and experimental results show that the proposed linear reversing control strategy of the semi-trailer based on the hitch angle stable and feasible domains can accurately realise the linear reverse-path tracking of the semi-trailer train, effectively avoiding the problems of jack-knife and trailer swing during the reversing process. Thus, the difficulty of the straight reverse operation is substantially reduced.

Model predictive-based tractor-trailer stabilisation using differential braking with experimental verification

Different types of instability modes in tractor-trailer vehicles, including jackknifing and snaking, necessitate designing a fast and effective control strategy. In this paper, a model predictive controller (MPC) is developed to prevent these instability modes in a car-trailer vehicle as a specific form of tractor-trailer vehicles equipped with differential braking. The effectiveness of the control action when the differential braking is applied only to the tractor and only to the trailer is also studied comparatively. The developed MPC controller utilises an affine tyre force model, and the control actions are limited based on the capacity of the tyres. The aim of the controller is to ensure that the tractor and the trailer follow the desired yaw rate and the desired hitch angle, respectively. The controller performance is evaluated through experimental tests and simulations. Experimental tests are conducted on an all-wheel-drive electric Chevrolet Equinox and a student-built research trailer, both equipped with an independent braking module on each wheel. In the simulations, the controller is implemented in MATLAB/Simulink, and an experimentally validated CarSim model of the tested tractor-trailer vehicle is employed. The results show that the designed MPC controller effectively prevents both instability modes; however, differential braking has much more capacity when it is applied to the tractor.

Research on Linear Reversing Control of Semi-trailer Based on Hitch Angle Stable Domain and Feasible Domain

Research on Linear Reversing Control of Semi-trailer Based on Hitch Angle Stable Domain and Feasible Domain

Development of a Unified Lane-Keeping and Collision Avoidance System for Semi-Trailer Truck

In this article, a unified lane-keeping and forward collision avoidance system is proposed for semi-trailer trucks. Kinematic and dynamic models are described for lateral motion of the semi-trailer truck. The variation of the cornering stiffness is considered because its value depends on driving conditions such as vehicle speed and vertical load. The proposed system consists of the hitch angle estimation algorithm of the semi-trailer truck and the Model Predictive Controller (MPC) for the lateral motion of the semi-trailer truck. In the hitch angle estimation, the disturbance observer is utilized to compensate the lateral uncertainties and the estimation performance is validated in simulations and experiments. In the controller design, an MPC controller is designed both for lane keeping and collision avoidance, but their constraints in lateral motion are considered separately. In constructing the objective functions, constraint smoothing is applied to improve the feasibility of the semi-trailer truck motion. A simplification method is also introduced to reduce the computational complexity of the MPC and to improve the real-time performance. The proposed system is evaluated in simulations for lane keeping and collision avoidance, respectively.

Trailer control through vehicle yaw moment control: Theoretical analysis and experimental assessment

This paper investigates a torque-vectoring formulation for the combined control of the yaw rate and hitch angle of an articulated vehicle through a direct yaw moment generated on the towing car. The formulation is based on a single-input single-output feedback control structure, in which the reference yaw rate for the car is modified when the incipient instability of the trailer is detected with a hitch angle sensor. The design of the hitch angle controller is described, including the gain scheduling as a function of vehicle speed. The controller performance is assessed by means of frequency domain and phase plane analyses, and compared with that of an industrial trailer sway mitigation algorithm. In addition, the novel control strategy is implemented in a high-fidelity articulated vehicle model for robustness assessment, and experimentally tested on an electric vehicle demonstrator with four on-board drivetrains, towing two different conventional single-axle trailers. The results show that: (i) the torque-vectoring controller based only on the yaw rate of the car is not sufficient to mitigate trailer instability in extreme conditions; and (ii) the proposed controller provides safe trailer behaviour during the comprehensive set of manoeuvres, thus justifying the additional hardware complexity associated with the hitch angle measurement.

Anti-jackknife reverse tracking control of articulated vehicles in the presence of actuator saturation

ABSTRACTIt is well known that backward motion control of an articulated vehicle is difficult because it is an open loop unstable system and such motion is also dangerous due to ‘jackknifing’. In this paper, an anti-jackknife reverse tracking control strategy for autonomous articulated vehicles is proposed based on the combined longitudinal and lateral control scheme. In the proposed lateral-longitudinal control scheme, the major task is to control the reverse heading of the trailer by automatic steering strategies that observe both the anti-jackknife condition and input limitations. The main contribution of this paper is the development of globally asymptotic anti-jackknife stabilising and tracking controls of heading angles with both state and input constraints considered a priori. The proposed control inherently has an anti-windup mechanism that prevents the hitch angle from going beyond any specified critical value to avoid jackknifing, during which time, the steering angle remains at its limit. Stability of the controller is theoretically proven via the Lyapunov argument. Effectiveness of the proposed approach is demonstrated by CarSim and Simulink joint simulations.

Fuzzy Logic Based Control of the Lateral Stability of Tractor Semitrailer Vehicle

A novel control scheme is proposed to improve the yaw stability of a tractor semitrailer vehicle in critical situations. The control scheme is a two-layer structure consisting of an upper yaw moment controller and a lower brake force distributor. The tractor and the trailer are, respectively, stabilized by two independent fuzzy logic based yaw moment controllers. The controllers for the tractor and the trailer are, respectively, designed to track the reference yaw rate of the tractor and the hitch angle between the tractor and the trailer while considering the variation of the hitch angular rate at the same time. The corrective yaw moments determined by the corresponding upper fuzzy yaw moment controllers are realized by active wheel braking. The performance of the proposed control scheme is evaluated by simulations on a nonlinear vehicle model. The results demonstrate that the proposed control scheme is robust and effective in stabilizing the severe instabilities such as jackknife and trailer oscillation in the chosen simulation scenarios. It is believed that this control scheme is robust to the variation of road adhesion conditions.

The critical hitch angle for jackknife avoidance during slow backing up of vehicle–trailer systems

We set out to answer the question: At what hitch angle does it become impossible for a vehicle and trailer to continue to backing up without getting into a jackknife? Jackknifing during backing up of trailers occurs when the hitch angle increases to a point such that the vehicle and trailer fold together about the hitch point like a jackknife. If the backward motion is continued, the jackknife effect progressively worsens, until the vehicle and trailer are in physical contact with each other. Jackknifing can result in traffic disruptions and wasted time, and can potentially cause damage or personal injury. Our goal is to analytically determine the ‘critical hitch angle’ (θcr), the hitch angle threshold beyond which a continued reverse motion causes an inescapable jackknifing. In this paper, we provide a formal definition of θcr for slow backing up of vehicle–trailer systems on a level solid surface, beyond which the vehicle must stop backing up and revert to forward motion in order to escape from jackknifing. The critical hitch angle is sub-categorised into Absolute (θcr, a) and Directional (θcr, d) critical hitch angles depending on the operating constraints and vehicle steering objectives. One solution for θcr is posed as a numerical solution to the steady-state conditions of the dynamic equations. The effects of such hitch angle limitations are demonstrated through simulation. Also, a warning system making use of the θcr is proposed. Such warning systems can assist drivers in avoiding jackknifing while backing up a vehicle–trailer system.

Driver Assistance System for Passive Multi-Trailer Vehicles with Haptic Steering Limitations on the Leading Unit

Driving vehicles with one or more passive trailers has difficulties in both forward and backward motion due to inter-unit collisions, jackknife, and lack of visibility. Consequently, advanced driver assistance systems (ADAS) for multi-trailer combinations can be beneficial to accident avoidance as well as to driver comfort. The ADAS proposed in this paper aims to prevent unsafe steering commands by means of a haptic handwheel. Furthermore, when driving in reverse, the steering-wheel and pedals can be used as if the vehicle was driven from the back of the last trailer with visual aid from a rear-view camera. This solution, which can be implemented in drive-by-wire vehicles with hitch angle sensors, profits from two methods previously developed by the authors: safe steering by applying a curvature limitation to the leading unit, and a virtual tractor concept for backward motion that includes the complex case of set-point propagation through on-axle hitches. The paper addresses system requirements and provides implementation details to tele-operate two different off- and on-axle combinations of a tracked mobile robot pulling and pushing two dissimilar trailers.