Hyster-Yale Group has launched the "Dynamic Mast Lowering" system for its J1.5-2.0 series 3-wheel electric forklifts designed for high-bay warehouses. As forklifts lift loads to heights above 10 meters, the risk of "mast oscillation" (swaying) increases. If the operator lowers the forks too fast, the load can swing violently, making it impossible to place the pallet accurately.
The Dynamic Mast Lowering system uses an "Inclinometer" on the mast carriage to detect the tilt angle. The hydraulic control valve features a "Proportional Lowering Spool" controlled by an ECU. When the operator moves the joystick to lower, the system monitors the lowering speed. If the mast carriage tilts forward rapidly (indicating a sway), the ECU instantly reduces the valve opening, restricting the flow to lower the forks at a reduced speed (e.g., 0.2 m/s) until the mast stabilizes.
The key innovation is the "Hydro-Electric Regeneration." During lowering, the potential energy of the load creates hydraulic pressure. A "Hydraulic Motor-Generator" unit is installed in the lowering line. When lowering heavy loads, this unit spins, generating electricity to recharge the battery. The resistance created by the generator also acts as a "braking force," providing smooth, controlled descent without generating heat in the hydraulic oil. Additionally, a "Speed-Dependent Damping" logic ensures that as the forks approach the ground (last 1 meter), the system applies a final "creep speed" regardless of the joystick position, ensuring the forks touch down softly without shock.
