A multibody dynamic system is defined as a collection of solid bodies (or links) that are connected to each other by joints. In such a multibody system, some or all of the bodies can move relative to one another, but do so while maintaining the aspect ratio.
So, what does kinematics and multibody dynamics mean? Simply put, it is the analysis of what happens when a part, system, mechanism or a product are so inter-connected to each other that the working of one affects the working of other, and thus enhances or diminishes the overall quality of work. It is important to study kinematics of a complex system as a whole. For example, take the case of a car. A car consists of various moving and non-moving parts that perform as a unit. Drilling a little deeper, a car has an axle that meshes with the wheel assembly. For optimum car performance, it is necessary for these two parts to move in unison. If they do not, they can cause friction or even displacement.
Multibody dynamics analysis is a virtual simulation of this entire body of parts as it analyses the effects they have on each other when they are in motion. It helps in designing and developing a system that works smooth, synchronized and unhindered.
There are two types of multibody dynamic analyses undertaken – forward dynamics and inverse dynamics. Forward dynamics involves the analysis of how individual components of the body move by the application of external forces. Inverse dynamics involves the study of forces needed to make the system move in a specific manner.
Science behind Multibody Analysis
Theoretically, any mechanical system can be represented schematically as a multibody system. Rather than the physical aspects, it is the connectivity, location of joints and internal characteristics that are of primary importance in the analysis of such a system.
Mechanics is a science that studies relationship between motion, time, and forces. It can be divided into statics and dynamics. While statics concerns study of stationary systems, dynamics deals with systems that change their response with respect to time. Dynamics is again subdivided into two branches – kinetics and kinematics. Kinetics is the study of motion and its relationship with the forces that produce that motion and Kinematics involves the study of motion disregarding which types of force produce that motion. Kinematics therefore is the process of finding the geometry of a mechanism that yields a desired set of motion characteristics. Kinematic analysis is a tool to support the kinematic process. The individual bodies that collectively form a mechanism are said to be links. The combination of two links in contact constitutes a kinematic pair, or joint. A collection of such interconnected links is called a kinematic chain. A mechanism is formed when at least one of the links of the kinematic chain is held fixed and any of its other links can move. The fixed link is called the ground or frame. If some links undergo motion in three-dimensional space, the mechanism is called a spatial mechanism.
Use of CAD Software for Kinematics
Simple kinematic and multibody systems can be described and solved by means of mathematical equations. However, as the system grows complex, it becomes near about impossible to solve (as they become nonlinear) them using simple means. This is where engineering companies take recourse to CAD software. Very complex systems need special kinematic and multibody service providers, who are highly trained and have enough resources to interpret the mathematical results accurately.
A kinematic family is a set of kinematic structures that have similar properties, such as the same interconnection topology, the same numerical or analytical solver algorithms, etc.
The newer CAD software uses rapid geometric modelling to integrate real-time kinematics and dynamics simulation capabilities to make virtual kinematic mechanism design possible. It is thanks to the computing power of CAD software that it is feasible to employ time-tested techniques of multibody dynamics to solve complex equations of motion. Accurate modelling of a multibody system also involves other aspect of the object like vibration and noise analysis, apart from friction.
One of the most sophisticated software for multibody dynamics analysis is Altair MotionSolve™. MotionSolve® is an integrated software solution to analyze and optimize multibody systems. It is based on proven numerical methods that allow powerful modelling, visualization, analysis and optimization of the multibody system under consideration.
Kinematics and Multibody Dynamics Services
Sophisticated software like Altair MotionSolve and other software that analyses multi body dynamics comprise many modules. Not only is good software expensive, it also requires skilled personal to operate it. Since kinematics and dynamics plays a crucial role in many industry verticals, enterprises prefer to outsource this service to specialists. India especially is a favourite choice for these services.