Fine position control of a vehicle maintenance lift system using a hydraulic unit activated by magnetorheological valves

This work presents a new concept of fine position control of vehicle lift systems used for maintenance services, to facilitate specialized tasks such as height balancing of tilted vehicles. The research goal is accomplished by utilizing a controllable hydraulic circuit associated with magnetorheological valves. After establishing the required dynamic forces and position control range of the vehicle’s lift system, a two-coil type of magnetorheological valve is designed with consideration of the field-dependent properties of the magnetorheological fluid and the magnetic flux intensity, which is analyzed using the finite element method. Magnetorheological valves are then manufactured and the pressure drops are evaluated as a function of the input current (magnetic field). A hydraulic circuit with magnetorheological valves is formulated to control the height of the lift with an accuracy of ±1 mm with a load of 2000 kg on the each lifts. It is experimentally demonstrated that ramp and sinusoidal positions (or height) are well tracked within the targeted accuracy by controlling the magnetorheological valves. In addition, it is shown that the tilted position of the loaded vehicle with an eccentric mass placed on the lift is well controlled showing the balanced height.