Development of high performance servo drive/anti drive mechanism for backlash removal
Keywords: 1 Degree of freedom Platform, Backlash Removal, System Modelling. Abstract: In electromechanical drives, there is always a backlash between any pair of gears. Because of this, it is almost impossible to realize a high accuracy and high performance drive. However such drives are crucial in today’s modern electromechanical systems. A high performance drive/anti-drive servo mechanism is developed to eliminate the effect of backlash. The concept utilizes redundant unidirectional drives to assure positive coupling of gear meshes at all times. Based on this concept, a methodology for enumeration of admissible redundant-drive backlash free mechanism has been established. The angular displacement is achieved as a difference of two torques. These torques can be controlled by a high performance control system. A controller model will be designed to move a single degree of freedom platform up to a desired span with a payload.
Development of a 2 degrees of freedom tracking system: design and fabrication of platform
This paper reports the design and fabrication of an innovative 2-DOF robotic platform for precision pointing and image-based tracking applications. Conventionally, such platforms have very simple structures but have various associated limitations. One such problem is the generally imbalanced structure due to the placement of the elevation actuator on moving base. This design causes a lot of problems when platform is operated at high angular velocities. This paper, however, proposes a new design that is balanced in structure and very light due to placement of both actuators in the stationary base, hence finding its applications in high speed tracking problems. This thing in return has caused coupling between the two degrees of freedom. However, it is a kinematics problem and can be resolved easily in the control algorithm.
Thermal stability of reconstituted collagen fibrils. Shrinkage characteristics upon in vitro maturation
Thermal stability measured as area shrinkage without tension during heating was determined for membranes of collagen fibrils reconstituted from solutions of highly purified rat skin collagens. Shrinkage in per cent of area at 25 degrees C and shrinkage temperature were quantitated in a standardized way and determined as a function of in vitro maturation time for 11 to 104 days after aggregation for the collagen membranes. Similar to reports on intact rat skin, shrinkage temperature remained constant and shrinkage per cent declined with a rate decreasing with time during maturation. Solubility in water at 80 degrees C for 2 hours was 95-96% and remained unchanged for the maturation time (about 2 months) studied. The decreased shrinkage reflecting a lower degree of collapse is ascribed to an increasing thermal stability of the membranes during maturation. Development of heat-stable bonds in the reconstituted collagen fibrils is taken up to be amenable to this increased stability. Similarity in changes of shrinkage characteristics during in vivo and in vitro maturation indicates that maturation changes in reconstituted collagen fibrils reflect those occurring in intact collagen during in vivo aging.