41 research outputs found
Improving the vibration suppression capabilities of a magneto-rheological damper using hybrid active and semi-active control
This paper presents a new hybrid active & semi-active control method
for vibration suppression in flexible structures. The method uses a combination of a
semi-active device and an active control actuator situated elsewhere in the structure
to suppress vibrations. The key novelty is to use the hybrid controller to enable
the magneto-rheological damper to achieve a performance as close to a fully active
device as possible. This is achieved by ensuring that the active actuator can assist
the magneto-rheological damper in the regions where energy is required. In addition,
the hybrid active & semi-active controller is designed to minimize the switching of the
semi-active controller. The control framework used is the immersion and invariance
control technique in combination with sliding mode control. A two degree-of-freedom
system with lightly damped resonances is used as an example system. Both numerical
and experimental results are generated for this system, and then compared as part
of a validation study. The experimental system uses hardware-in-the-loop to simulate
the effect of both the degrees-of-freedom. The results show that the concept is viable
both numerically and experimentally, and improved vibration suppression results can
be obtained for the magneto-rheological damper that approach the performance of an
active device
Cathepsin A regulates chaperone-mediated autophagy through cleavage of the lysosomal receptor
Protective protein/cathepsin A (PPCA) has a serine carboxypeptidase activity of unknown physiological function. We now demonstrate that this protease activity triggers the degradation of the lysosome-associated membrane protein type 2a (lamp2a), a receptor for chaperone-mediated autophagy (CMA). Degrada tion of lamp2a is important because its level in the lysosomal membrane is a rate-limiting step of CMA. Cells defective in PPCA show reduced rates of lamp2a degradation, higher levels of lamp2a and higher rates of CMA. Restoration of PPCA protease activity increases rates of lamp2a degradation, reduces levels of lysosomal lamp2a and reduces rates of CMA. PPCA associates with lamp2a on the lysosomal membrane and cleaves lamp2a near the boundary between the luminal and transmembrane domains. In addition to the well-studied role of PPCA in targeting and protecting two lysosomal glycosidases, we have defined a role for the proteolytic activity of this multifunctional protein