We report on 2D collision experiments with 9 thin Delrin disks with variable axisymmetric mass distributions. The disks floated on an air table, and collided at speeds of about 0.5 to 1.0 m/s with a flat-walled stationary thick steel plate clamped to the table. The collision angle was varied. The observed normal restitution was roughly independent of angle, consistent with other studies. The fr...

The use of rigid body models during frictional contact i s often justified by proving the existence of a unique solution to the forward dynamic equations. The implicit assumption here is that the contact forces so obtained are stable. In this paper, the rigid-body assumption is relaxed and bodyto-body contacts are modeled using springs and dampers. A singular perturbation analysis reveals addit...

In this paper we continue our investigations into robotic air hockey by studying the problem of controlling the trajectory of a puck subject to intermittent impacts. Impacts are modeled using the Routh two-dimensional impact model which incorporates spin and friction. Using this model, we derive an explicit mapping between pre-impact and post-impact velocities of the puck. We will see that this...

BACKGROUND Lumbosacral orthoses (LSOs) are class I medical devices that are used in conservative and postoperative management of low back pain. The effectiveness of LSOs depends on their design aimed at enhancing trunk stiffness. Therefore, the purpose of this study was to compare two lumbar supports: extensible (made of neoprene and lycra) and non-extensible (made of polyester and nylon). ME...

The sliding interfaces found in the body— within the eyes, the digestive system, and the articulating joints, for example—are soft and permeable yet extremely robust, possessing low friction. The common elements among these systems are hydrophilic biopolymer networks that provide physical surfaces, elasticity, and fluid permeability. Stiff, impermeable probes are traditionally used to assess th...

high-precision three-axis attitude control scheme is vitally important to deal with the overactuated spacecraft, as long as the overall performance through rapid response can be in general acquired. due to the fact that the rigid-flexible spacecraft is somehow applicable, in so many academic and real environments, there is a consensus among experts of this field that the new insights in develop...

The concept of a 'deformable arm scale' (completely different from a traditional rigid arm balance) is theoretically introduced and experimentally validated. The idea is not intuitive, but is the result of nonlinear equilibrium kinematics of rods inducing configurational forces, so that deflection of the arms becomes necessary for equilibrium, which would be impossible for a rigid system. In pa...

Simulation of dynamic systems possessing unilateral frictional contacts is important to many industrial applications. While rigid body models are often employed, it is well established that friction can cause problems with the existence and uniqueness of the forward dynamics problem. In these situations, we argue that compliant contact models, while increasing the length of the state vector, su...