Abstract: High-load disturbances on implements during rotary tillage can cause significant wheel slip and impaired speed control. These issues adversely affect, and can severely compromise, the longitudinal stability of distributed electric-drive horticultural facility mobile platforms. To address these issues, a cascaded control method based on integral robust vehicle speed control and sliding-mode slip rate control is proposed. Its effectiveness is validated through simulations and vehicle experiments. First, considering tire-soil interaction and the resistance characteristics of rotary tillage, a dynamic model of the coupled system between the distributed electric-drive horticultural platform and the rotary tiller is established. The model explicitly incorporates wheel rotational dynamics and external disturbance torques induced by soil adhesion and variable tillage resistance. Moreover, the nonlinear relationship between longitudinal tire force and slip ratio is described to accurately characterize traction generation under deformable soil conditions, thereby forming a comprehensive coupled modeling framework. This modeling approach provides a theoretical basis for coordinated slip regulation and speed stabilization under high-load operating environments. Subsequently, an outer-loop vehicle speed controller is designed, incorporating integral robust control to eliminate steady-state errors caused by modeling inaccuracies and operational disturbances, thereby ensuring speed stability. The integral term compensates for persistent disturbance-induced bias, while the robust component enhances the controller’s tolerance to parametric uncertainties and unmodeled dynamics. By combining integral action with robustness enhancement, the outer-loop controller maintains accurate speed tracking even when sudden load fluctuations occur. Furthermore, an inner-loop slip rate controller is developed using sliding-mode control, with the optimal slip rate obtained from the inverse tire model serving as the reference input to achieve rapid convergence and precise slip rate tracking. Sliding-mode control is selected due to its inherent robustness against matched disturbances and modeling uncertainties, enabling fast dynamic response and strong anti-interference capability. The reference optimal slip rate corresponds to the traction peak region of the tire–soil interaction curve, thereby maximizing traction efficiency while preventing excessive slip. The platform’s longitudinal stability under high-disturbance conditions is improved through the coordination of outer and inner loops which forms an integrated control strategy for anti-slip driving and speed regulation. Through this cascaded structure, the inner loop rapidly suppresses slip ratio deviations, while the outer loop guarantees global speed regulation performance, forming a hierarchical traction control architecture suitable for distributed electric-drive systems. Simulation results indicate that under sudden muddy conditions, the cascaded control method achieved an average speed error of 0.10 km/h, representing reductions of 16.6% and 67.7% compared to switching control and speed control, respectively. The corresponding speed recovery time was 0.11 seconds, reduced by 35.2% and 68.6%, respectively. Under variable tillage depth simulation conditions, the cascaded control method yielded an average speed error of 0.072 km/h, representing reductions of 40.0% and 52.0% compared with switching control and speed control, respectively. Additionally, the average slip rate was 0.12, reduced by 7.6% and 58.6%, respectively. Experimental results indicate that under acceleration conditions, the cascaded control method achieved an average speed error of 0.44 km/h, representing reductions of 4.3% and 8.3% compared to switching control and speed control. The average slip ratio was 0.15, reduced by 11.7% and 16.6%, respectively. Under deep tillage conditions, the cascaded control method yielded an average speed error of 0.20 km/h, representing reductions of 20.0% and 37.5% compared to switching control and speed control. The average slip ratio was 0.13, reduced by 23.5% and 31.6%, respectively. Therefore, the proposed cascaded controller can effectively suppress the slip ratio during rotary tillage operations, thereby enhancing vehicle speed control performance and operational stability.