Modular and Distributable approach towards Kinematic and Dynamic modeling of Hybrid robots

While serial robots are known for their versatility in applications, larger workspace, simpler modeling and control, they have certain disadvantages like limited precision, lower stiffness and poor dynamic  characteristics in general. A parallel robot can offer higher stiffness, speed, accuracy and payload capacity, at the downside of a reduced workspace and a more complex geometry that needs careful analysis and control. To bring the best of the two worlds, parallel submechanism modules can be connected in series to achieve a series-parallel hybrid robot with better dynamic characteristics and larger workspace. Such a design philosophy is being used in several robots at DFKI for example, Mantis, Charlie, Recupera Exoskeleton, RH5 humanoid etc. Computing the whole body kinematics and dynamics of such hybrid robotic systems is a huge challenge because of the presence of closed loops in the system. The traditional approaches in kinematic and dynamic modeling often take the numerical approaches for resolving loop closure constraints which suffer from inaccuracy and inefficiency issues. Also, they do not exploit the modularity and hierarchy in robot design. This talk presents the general idea of a modular and distributable software framework called Hybrid Robot Dynamics (HyRoDyn) which can be used to solve the geometry, kinematics and dynamics of hybrid robotic systems with the help of a software database which stores the analytical solutions to parallel kinematics in a configurable and unit testable manner. Kinematic and dynamic modeling of RH5 humanoid legs till the knee joints is demonstrated as a first proof of concept. In the long run, the aim of this software tool is to assist both designers and control engineers in developing complex robotic systems of the future. Efficient kinematic and dynamic modeling can lead to more compliant behavior, better whole body control, walking and manipulating capabilities etc. which are highly desired in the present day and future robotic applications.