Accelerating the Validation of Motion Control for a 4WD4WS Ground Vehicle Using a Hierarchical Controller Hardwareintheloop System xe2x88x97 Due to the actuator redundancy and complexity of the unmanned ground vehicle actuated by fourwheel drive and fourwheel steering powertrains (4WD4WS UGV), it is a significant challenge to conduct fast verification of the complex control system. This work presents a dedicated hierarchical controller hardwareintheloop system to accelerate the verification of the motion control system for a 4WD4WS UGV. The hierarchical controller, that is implemented in a combined onboardcomputer and embedded microcontroller, adopts a threelayered architecture. The upper layer uses a model predictive control algorithm (MPC) to calculate the desired heading angle and vehicle speed. The middle layer converts the control effect into the desired speeds and steering angles of four wheels. The bottom layer controls the drive motor and steering motor to track the desired speed and steering angle of each wheel. The proposed HCHIL system establishes a multibody dynamics model of the 4WD4WS UGV with high fidelity, and accelerates the validation process of the motion control performance, via which the complex control strategy can run in the actual control hardwares and be verified in a virtual model with high fidelity. The HCHIL system provides a fast and low cost method for initial testing prior to the real implementation, thereby reducing the potential failures in future real testing.

Smooth Trajectory Tracking Using Longitudinal Distance Constraint for A 4WS4WD Unmanned Ground Vehicle The modelbased trajectory tracking method of four wheel steering and four wheel drive (4WS4WD) unmanned ground vehicles (UGVs) needs to establish accurate vehicle kinematics and dynamics models, which is computationally complex thus functioning poorly in realworld scenarios. The geometrybased method, i.e., the pure pursuit method, uses the position information to regulate vehicleu0027s steering angle, which has good realtime performance in practical applications. However, the existing pure pursuit method only considers the lookahead distance constraint, ignoring the influence of the longitudinal distance which affects the smoothness of the vehicle trajectory. It may cause the vehicle to oscillate back and forth around the target trajectory. This work proposes an improved pure pursuit method with longitudinal distance constraint (LDC) to avoid the vehicle oscillation effectively. Additionally, to alleviate the cornering cutting problem, a fuzzy logic based controller is proposed to dynamically adjust the lookahead distance according to the curvature. A comparative experiment between the proposed method and the conventional pure pursuit method was conducted. Results show that the proposed method has better trajectory smoothness and tracking accuracy than the traditional pure pursuit method.