Development of semi-active damper for heavy off-road military vehicles

Most conventional automotive vehicle suspensions utilize passive shock absorbers to provide damping of the vehicle suspension. These shock absorbers convert mechanical energy in the suspension to heat which is then dissipated. Passive shock absorbers rely on mechanical means to control this energy dissipation and do not receive energy other than that provided by the movement of the suspension.; Semi-active dampers or shock absorbers use an actively powered valve, flow restriction, or other technology which allows the damping of the shock absorber to be changed and externally controlled. Mechanical energy is not added to the damper but the dissipation of that energy can be controlled by a powered actuator.; Semi-active damper technology allows vehicle suspension systems to be designed which can provide greater improvements in the areas of vehicle ride quality and handling and stability than can be provided by traditional passive hydraulic shock absorbers. Several different technologies have been identified or developed for use in semi-active dampers such as magnetorheological fluids and solenoid valves. The application of semi-active suspension technology to heavy off-road military vehicles has the potential to vastly improve the performance of such vehicles.; The objective of this thesis is to evaluate appropriate technologies for use in semiactive suspensions of heavy off-road military vehicles, and to examine the development and testing of new valve designs created for that purpose.; In this work a prototype solenoid valve actuated semi-active twin-tube shock absorber with a piston mounted solenoid valve is developed and tested. The damping capabilities of the prototype are measured and the semi-active piston valve is instrumented in order to measure its performance during varying forcing conditions.; A parametric mathematical model of the twin-tube shock absorber is developed which includes fluid compressibility and a poppet style foot valve. This model is numerically simulated and matched to the results of the prototype damper tests.; A second semi-active damper concept is developed which uses a piloted magnetorheological fluid actuated valve installed in the shock absorber piston. The unique magnetorheological fluid actuator is analyzed and optimized using finite element method software to simulate its magnetic field. A prototype actuator is constructed and tested to measure the generated force. The test results are compared to the predicted force obtained using the magnetic simulation.; The test results show that the solenoid valve design is able to provide greater control over damping than the MR actuator. The solenoid valve damper provides between 20 and 30 kN of damping force at 1 m/s with a solenoid providing up to 230 N of force whereas the MR actuator prototype was only able to provide up to 30 N of force in dynamic testing.