A Constant Stroking Load Regulator for Shock Absorption

The goal of this study is to provide shock mitigation in an active (or semi-active) shock absorption system, typically comprising of a spring, and an adjustable stroking load element, such as an adaptive energy absorber (EA) or semiactive damper element, in which the stroking load can be electronically adjusted in real-time. Typically, there is a maximum limiting stroking load that can be accommodated by a payload. Thus, a Constant Stroking Load Regulator (CSLR) is developed that accepts sensor feedback, and then selects control gains that result in the energy absorber (EA) providing the required controllable stroking load. A key benefit of this regulator is that it is capable of adapting to a varying range of payload mass, impulse types, and impulse excitation levels. The payload mass is measured and used as a control input parameter. The measured impact velocity is used to determine the impulse acceleration level by assuming an impulse profile, which tends to be application-specific. Finally, the required constant stroking load is determined using a physics-based model. The CSLR is designed to achieve a “soft landing” such the payload comes to rest when the available stroke is used completely, in order to minimize the stroking load and thereby minimize the potential for payload damage. The CSLR methodology was then experimentally validated for a representative occupant protection system consisting of a seat suspension with an adaptive stroking element, which in this case was a magnetorheological energy absorber (MREA). A MREA was used as the stroking element because its stroking load can be adjusted electronically. To validate the CSLR strategy, experimental drop tests were conducted for two different payloads. The impact velocity was 10.3 ft/s (3.15 m/s) and the acceleration profile was a 50 ms duration half-sine pulse. The constant stroking load was pre-calculated as a function of payload mass and initial velocity. During each drop test, the required stroking load was supplied to the MREA in order to achieve a “soft landing.” The CSLR was successfully demonstrated under laboratory conditions. These tests demonstrated feasibility of using the CSLR, in conjunction with a MREA as the stroking element.