Computational study on lateral and medial wear characterization in knee implants by a multibody dynamic system

Wear is one of the main mechanical factors that limits the survival of total knee replacements (TKRs) and it is known to be highly dependent on the local kinematics of the knee joint. In this study, an analytical wear model was coupled to a multibody dynamic model to obtain wear distribution at the lateral and medial contact plateaus of different TKRs. The major aim was to analyze if wear distribution on the contact plateaus can be an indicator of elevated tibiofemoral misalignment which can lead to rapid TKR failure. For the multibody dynamic simulations, commercial and prototype TKR geometries were used, coupled with an augmented Archard’s law. Squat movement was chosen due to its importance both in sports and in everyday life. As a conclusion, a new parameter, denoted as wear imbalance, is introduced, which can indicate whether a TKR, due to its geometrical features, is prone to be subjected to elevated wear and failure.

The Artificial Intelligence and Design of Multibody Systems with Predicted Dynamic Behavior

The problem of complicated dynamic system optimization is very difficult for human intellect. The design of these systems comprises typical tasks of artificial intelligence – big data analysis, decision making, etc. In this article, we applied artificial intelligence approach to optimize the properties of the multibody dynamic system. It is very important to study the whole carrying system of a high-speed railroad in its integrity because the elements of the system interact and influence each other simultaneously. The system should include the train of several cars, the track upper structure, and the bridges. It is possible to synthesize the optimal system with predicted behavior that meets various constraints on dynamic parameters and interaction between the elements of the system.

Automating the Derivation of the Equations of Motion of a Multibody Dynamic System With Uncertainty Using Polynomial Chaos Theory and Variational Work

Understanding how variation impacts a multibody dynamic (MBD) system's response is important to ensure the robustness of a system. However, how the variation propagates into the MBD system is complicated because MBD systems are typically governed by a system of large differential algebraic equations. This paper presents a novel process, variational work, along with the polynomial chaos multibody dynamics (PCMBoD) automation process for utilizing polynomial chaos theory (PCT) in the analysis of uncertainties in an MBD system. Variational work allows the complexity of the traditional PCT approach to be reduced. With variational work and the constrained Lagrangian formulation, the equations of motion of an MBD PCT system can be constructed using the PCMBoD automated process. To demonstrate the PCMBoD process, two examples, a mass-spring-damper and a two link slider–crank mechanism, are shown.

Analysis of Free Pendulum Vibration Absorber Using Flexible Multi-Body Dynamics

Structures which are commonly used in our infrastructures are becoming lighter with progress in material science. These structures due to their light weight and low stiffness have shown potential problem of wind-induced vibrations, a direct outcome of which is fatigue failure. In particular, if the structure is long and flexible, failure by fatigue will be inevitable if not designed properly. The main objective of this paper is to perform theoretical analysis for a novel free pendulum device as a passive vibration absorber. In this paper, the beam-tip mass-free pendulum structure is treated as a flexible multibody dynamic system and the ANCF formulation is used to demonstrate the coupled nonlinear dynamics of a large deflection of a beam with an appendage consisting of a mass-ball system. It is also aimed at showing the complete energy transfer between two modes occurring when the beam frequency is twice the ball frequency, which is known as autoparametric vibration absorption. Results are discussed and compared with findings of MSC ADAMS. This novel free pendulum device is practical and feasible passive vibration absorber in the mitigation of large amplitude wind-induced vibrations in traffic signal structures.

Design Optimization for Minimizing Actuation Energy of a Dynamic Tripedal Walking Robot: Revisiting the Double Pendulum

This work presents a systematic approach to the optimal co-design of a multibody dynamical system’s mechanics and control. The formulation presented is based on a simple double pendulum system, thus allowing a focused illustration of the co-design methodology. However, the ultimate goal is to apply this co-design methodology to the design of a novel Self-excited Tripedal Dynamic Experimental Robot, STriDER. One of STriDER’s design challenges is to determine its mechanical properties and control inputs that minimize the amount of externally supplied actuation energy required to take a single step. Past STriDER prototypes have successfully taken highly efficient dynamic steps, however, these former prototypes required significant manual ‘tweaking’ of its mechanical parameters to realize these steps. Additionally, STriDER’s optimal joint trajectories and actuation inputs have not been outputs of the previous design process. This work provides the first systematic process for the optimal co-design of a controlled multibody dynamic system such as STriDER.