For the problem that, under the soybean-maize strip intercropping pattern, the installation of anti-drift shields changes the mass and inertia characteristics of the boom of a shielded sprayer, making it prone to severe vibration under complex field excitations and thereby affecting application uniformity and operational safety, a semi-active boom vibration damping system based on a magnetorheological damper was designed and tested. First, an equivalent mechanical model of the boom considering added mass and stiffness variation was established, and the characteristics of excitation sources such as road spectra and start-stop impacts were clarified. Second, based on the Bouc–Wen model, the magnetorheological damper was selected and its output force boundaries were designed. The stroke was determined to be 80–110 mm, and the maximum damping forces in the compression and rebound strokes were 1.15 kN and 3.44 kN, respectively. Furthermore, a semi-active vibration damping system with an LK3U-14MT PLC as the core controller was developed. Finally, simulation analysis, free-vibration decay tests, obstacle-crossing tests, and field operation tests were conducted to verify the vibration damping performance of the developed semi-active system. The field test results showed that, at typical operating speeds of 3–5 km/h, the semi-active vibration damping system reduced the maximum vertical amplitude at the boom tip by 28.6–43.1% and the maximum inclination angle by 12.2–55.6%, effectively improving the attitude stability and roll resistance of the boom of the shielded sprayer.

Semi-active suspension systems combine low power consumption, rapid response, and fail-safe operation by reverting to passive mode after control failure, making them important for intelligent chassis and vibration-control systems. With the development of intelligent actuators, nonlinear modeling, and advanced control methods, this technology is expanding from conventional road vehicles to off-road vehicles and agricultural machinery. Compared with passenger cars, agricultural machinery faces stronger random excitation, time-varying loads, muddy environments, resource-constrained controllers, and requirements for operational accuracy. This review focuses on semi-active damping and vibration-isolation systems for off-road and agricultural applications. Mainstream actuators, control-oriented nonlinear damper models, classical, robust, and adaptive control methods, MPC, DRL, and mechanism–data fusion control are compared in terms of hardware constraints, model accuracy, real-time computation, and agricultural adaptability. Applications in seat/cab isolation, tractor and tracked chassis systems, rollover prevention, and precision implements are summarized. The review shows that semi-active suspension in agricultural machinery is evolving beyond the conventional trade-off between ride comfort and handling stability toward multi-objective coordination of safety, ground-contact stability, operational accuracy, operator protection, and energy consumption.