Abstract
A model predictive control (MPC) approach based on direct yaw moment control (DYC) was proposed to realize the self-steering drive for a newly autonomous four-wheel independent-drive (4WID) agricultural electric vehicle. The front axle and rear axle of the vehicle chassis could rotate simultaneously around their respective center points and cut the turning radius in half at most through specific mechanical chassis structure design and four-wheel electrical drive. It had great potential to reduce wheel traffic damage to field crops if two rear electrical drive wheels can be controlled to follow wheel tracks of two front wheels during self-steering operation. Therefore, firstly, a two-degree-freedom dynamics model presenting this agricultural electric vehicle was constructed. Then, an MPC controller combined with DYC was applied to arrange torques from four wheels to match desired turning angles, direct yaw moments and travel speeds. The simulation results existed small steady error of steering angles below 0.22% as they were set at 5°, followed with yaw moment under 0.17% and velocity less than 1%. Finally, according to experiment results, the vehicle successfully made a working turning radius of 9.1 m with maximum error of 0.55% when desired steering angles were 5° at the speed of 1 m/s and a minimum turning radius of 1.51 m with maximum error of 6.6% when steering angles were 30° at the speed of 0.5 m/s. It verified that the 4WID agricultural electric vehicle could drive autonomously and steady with small self-steering angle error under the proposed control system and has a feasibility to reduce wheel traffic damage during driving and operation. Keywords: agriculture mechanization, 4WID electric vehicle, self-steering, model predictive control DOI: 10.25165/j.ijabe.20211402.5283 Citation: Liu H, Yan S C, Shen Y, Li C H, Zhang Y F, Hussain F. Model predictive control system based on direct yaw moment control for 4WID self-steering agriculture vehicle. Int J Agric & Biol Eng, 2021; 14(2): 175–181.
Highlights
In recent years, agricultural autonomous vehicle has become the focus of attention under the demand of improving the labor productivity and reducing the labor intensity in precision agriculture[1,2,3]
A novel control model was proposed based on Newtonian rigid body mechanics[26] for this kind of 4WID self-steering vehicle to work on farm and solve steering stability problems[27,28,29]
In order to evaluate the performance of the proposed self-steering model predictive control (MPC) control system, the 4WID agricultural vehicle model with MPC controller was built with Matlab Simulink
Summary
Agricultural autonomous vehicle has become the focus of attention under the demand of improving the labor productivity and reducing the labor intensity in precision agriculture[1,2,3]. Vehicle changing the speed, but rely on relatively stable working environment and vehicle center of gravity distribution On this occasion, direct yaw moment control (DYC) was proposed with good coordination between steering angle and yaw moment[7,8,9,10,11]. With rich theoretical experience and practical prospects on coordinated and optimized control, it has fully demonstrated great potential in complex motion control In this case, MPC controller can optimize torque by driving the four independent motors to keep the vehicle working safely and enhance the robustness under extreme conditions[23,24,25]. A novel control model was proposed based on Newtonian rigid body mechanics[26] for this kind of 4WID self-steering vehicle to work on farm and solve steering stability problems[27,28,29]. The control problem was expressed as a Linearly Constrained Quadratic Programming (QP) to compute the optimal and dynamically-consistent front and rear axle angles required to achieve desired paths
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