Path tracking and stabilization for a reversing general 2-trailer configuration using a cascaded control approach

Abstract

In this paper a cascaded approach for stabilizationand path tracking of a general 2-trailer vehicle configurationwith an off-axle hitching is presented. A low level LinearQuadratic controller is used for stabilization of the internalangles while a pure pursuit path tracking controller is used ona higher level to handle the path tracking. Piecewise linearityis the only requirement on the control reference which makesthe design of reference paths very general. A Graphical UserInterface is designed to make it easy for a user to design controlreferences for complex manoeuvres given some representationof the surroundings. The approach is demonstrated with challengingpath following scenarios both in simulation and on asmall scale test platform.iQMati

Motion planning for a reversing general 2-trailer configuration using Closed-Loop RRT

“…Using the results from [3] where an LQ-controller is used to stabilize the internal angles of the system and a pure pursuit path tracking controller is used for path tracking the input to the pure-pursuit controller is sampled with an CL-RRT algorithm to produce feasible paths that include both the kinematics of the model and the dynamics of the controller. However, with this approach optimality and completeness guarantees cannot be formally guaranteed [19] and instead convincing practical results from simulations and some experiments on a small scale platform are provided which demonstrate the applicability of the algorithm even without these formal guarantees.…”

“…To be able to simulate the system without entering a jack-knife state when reversing the cascaded control approach presented in [3] is used. For the low level stabilization of β 2 and β 3 an LQ-controller with gain scheduling is used and as a higher level path tracker a pure pursuit control law is employed.…”

“…The full details of the linearization steps and control design is found in [3] but for clarity the main steps are presented here. By considering the subsystem (4)- (5) and defining β β β = [β 3 , β 2 ] T , this system can be linearized around circular equilibrium points giving the linearised model β β β =Ā(β β β −β e β e β e ) +B(α − α e )…”

“…For a thorough analysis of the tracking performance on the small scale test platform the reader is referred to [3] and Fig. 10: One instance of the driver test scenario.…”

“…1 and a closed loop stabilised model of the general 2-trailer configuration is used for tree extensions. A cascaded control scheme using a Linear Quadratic (LQ) controller, based on the work in [2], is used to stabilize the vehicle configuration around an equilibrium point and then a pure-pursuit path tracking controller is used to make the vehicle configuration follow a piecewise linear reference path as in [3].…”