A Novel Method for Prediction of Mobile Robot Maneuvering Spaces

As the operational uses of mobile robots continue to expand, it becomes useful to be able to predict the admissible maneuvering space to prevent the robot from executing unsafe maneuvers. A novel method is proposed to address this need by using force-moment diagrams to characterize the robot’s maneuvering space in terms of path curvature and curvature rate. Using the proposed superposition techniques, these diagrams can then be transformed in real-time to provide a representation of the permissible maneuvering space while allowing for changes in the robot’s loading and terrain conditions. Simulation results indicate that the technique can be applied to determine the appropriate maneuvering space for a given set of loading conditions, longitudinal acceleration, and tire-ground coefficient of friction. This may lead to potential expansion in the ability to integrate predictive vehicle dynamics into autonomous controllers for mobile robots and a corresponding potential to safely increase operating speeds

A Novel Method for Prediction of Mobile Robot Maneuvering Spaces

As the operational uses of mobile robots continue to expand, it becomes useful to be able to predict the admissible maneuvering space to prevent the robot from executing unsafe maneuvers. A novel method is proposed to address this need by using force-moment diagrams to characterize the robot’s maneuvering space in terms of path curvature and curvature rate. Using the proposed superposition techniques, these diagrams can then be transformed in real-time to provide a representation of the permissible maneuvering space while allowing for changes in the robot’s loading and terrain conditions. Simulation results indicate that the technique can be applied to determine the appropriate maneuvering space for a given set of loading conditions, longitudinal acceleration, and tire-ground coefficient of friction. This may lead to potential expansion in the ability to integrate predictive vehicle dynamics into autonomous controllers for mobile robots and a corresponding potential to safely increase operating speeds

Dynamic behaviour of ball bearing applications with constrained damping layers

Rolling bearing noise has become an aspect of increasing importance for the performance of rotating machinery, like electric motors and gearboxes. Generally, two aspects are important with regard to bearing noise, i.e. the transmission characteristics and the vibration generation characteristics. A potential source of vibrations are for example manufacturing imperfections of the different bearing components. Damping of bearing vibrations is enhanced by the lubrication film between the rolling elements and the raceway of the bearing. Regarding vibrations of the total application, the reduction of vibration transmission can be increased by applying a constrained viscoelastic layer between the bearing and the housings. To design an effective damping layer a 3D nonlinear time dependent computational model is developed to simulate the dynamic behaviour of a ball bearing application. The bearing model incorporates the stiffness and damping properties of the lubricant. Flexible components including the viscoelastic layer are modelled with FEM and reduced with a Component Mode Synthesis technique. Viscoelasticity is described both in the time and frequency domain by a generalized Maxwell model. The model is validated experimentally using constrained damping layer samples. Results are shown for a typical ball bearing application, showing that a proper design and material selection of the constrained layer is important for the reduction of the overall vibrations of the application

Pose estimation of a scanning laser Doppler vibrometer with applications to the automotive industry

A scanning laser Doppler vibrometer (SLDV) is an optical instrument that can scan an area to measure the velocity field of structures. It has been widely used in the automotive industry. In some applications, the pose (position and orientation) of the SLVD are required. First, this paper describes two such applications. Then it presents a nonlinear regressive model for the pose determination of the SLDV with respect to a structural coordinate system. The model is derived from coordinate transformation and the scanner model. In it, the pose is expressed by six independent parameters: three for the translation vector and three for the rotation matrix. The six parameters are estimated by using the least-squares technique. Statistical inferences about this model are obtained by linear approximation. To determine the pose, four or more registration (reference) points are required. For each registration point, the structural coordinates and its corresponding input voltages need to be known. The model has been implemented in a laser-based data acquisition system, which has been used for modal analysis, structural dynamic modifications, and noise control. © 1998 Society of Photo-Optical Instrumentation Engineers

Using multi-axis material extrusion to improve mechanical properties through surface reinforcement

Due to the layer stacking inherent in traditional three-axis material extrusion (ME) additive manufacturing processes, a part's mechanical strength is limited in the print direction due to weaker interlayer bond strength. Often, this requires compromise in part design through either adding material in critical areas of the part, reducing end-use loads or forgoing ME as a manufacturing option. To address this limitation, the authors propose a multi-axis deposition technique that deposits material along a part's surface to improve mechanical performance. Specifically, the authors employ a custom 6 degree of freedom robotic arm ME system to create a surface reinforcing ‘skin’, similar to composite layup, in a single manufacturing process. In this paper, vertical tensile bars are fabricated through stacked XY layers, followed by depositing material directly onto the printed surface to evaluate the effect of the skinning approach on mechanical properties. Experimental results demonstrate that surface-reinforced interlayer bonds provide increased yield strength

Design and Realization of a 6 Degree of Freedom Robotic Extrusion Platform

The layer-wise deposition of Additive Manufacturing (AM) processes allows for significant freedom in the design of product geometry; however, the use of 3-axis deposition tools results in layer interfaces that reduce material properties in the build direction. Adding additional degrees-of-freedom (DOF) to the AM tool could remove this limitation by enabling out of plane material deposition. For example, multi-DOF tool paths could align material extrusion with a part's stress contours to circumvent inter-layer delamination. As a step towards this goal, the authors designed, fabricated, and tested an AM extrusion system that leverages a 6-DOF robotic arm. In this paper, the authors detail the realization of this system including the design of a high-temperature filament extruder, kinematics and tool path generation, and user interface. The performance of the system is evaluated through layered deposition of ABS thermoplastic.Mechanical Engineerin