Anti-Rollover Control Based on Stable Zone Partition of Counterbalanced Forklift Trucks

To improve the anti-rollover capacity of a counterbalanced forklift, a two-stage rollover dynamic model is established on the basis of the forklift structure. Stable zones are divided according to the two-stage lateral load transfer rate: stable region, relatively stable region, dangerous zone and abnormal dangerous zone. An anti-rollover layered control strategy based on stable zone partition is proposed, and different anti-rollover control actuators are selected: dynamic balance weight, anti-rollover cylinder and steering cylinder. Anti-rollover controllers consist of the upper stable region identification controller, the middle-level controller based on model predictive control (MPC) and the lower layer executive controller. The upper stable region identification controller performs stable zone recognition based on the two-stage lateral load transfer rate. The middle-level MPC controller calculates the required control torque with the body’s lateral angle and yaw rate as the control objectives. The lower layer executive controller controls the balance weight, anti-rollover cylinder and the steering cylinder according to the improved chain incremental allocation method to meet the target control torque. Simulation and real vehicle tests based on MATLAB/Simulink show that the anti-rollover control based on stable zone partition can greatly reduce the risk of forklift rollover and improve the forklift safety.