Main Research Domains
Marco Carricato performs his scientific research mainly in the following fields:
- Cable-Driven Robots
- Robot Kinematics
- Design of Parallel Manipulators and Mechanisms
- Singular Configurations of Mechanisms
- Dynamic Analysis and Balancing of Spatial Manipulators
- Compliant Mechanisms
- Optimal selection of components in servo-controlled machinery
- Mobile collaborative robotics
A. Cable-driven robots
Cable-driven parallel robots (CDPRs) employ cables to control the pose of the end-effector. Even though CDPRs with less than 6 cables do not allow the end-effector to be fully controlled, their use is justified in several applications in which a limited dexterity is required. A major challenge in the study of underconstrained CDPRs comes from the fact that their configuration depends on both the actuator inputs and the applied external forces. As a consequence, kinematics and statics/dynamics are coupled. This research aims at providing a general methodology for kinematic, static, dynamic and stability analysis of underconstrained CDPRs. Under the PRIN project “Intelligent cable-driven robots: an adaptive approach to robot design and control”, a reconfigurable prototype has been developed that allows fully and under-constrained robots to be studied.
B. Robot kinematics
Innovation in mechanism analysis and synthesis calls for the characterization and classification of the end-effector task space. A smooth task space is a manifold of the special Euclidean group SE(3). Mechanisms often share the following property: the instantaneous twist space generated by the end-effector at a generic pose is a rigidly-displaced copy of the one generated at the home configuration, i.e. the tangent spaces at all points of the motion manifold are mutually congruent. Such a persistent manifold can be seen as the envelope of a persistent twist space rigidly moving in SE(3). This research investigates two important classes of persistent manifolds, whose concepts he introduced for the first time: persistent product-of-exponential manifolds and symmetric subspaces of SE(3). In both cases, information concerning the instantaneous motion of the mechanism are sufficient to characterize the end-effector finite motion. The study and classification of persistent manifolds of SE(3) is believed to play a crucial role in mobility analysis and mechanism synthesis.
C. Design of parallel manipulators and mechanisms
In order to overcome the typical drawbacks of closed-chain mechanisms (e.g. limited dexterity, involved kinematic relations, critical singularities) while preserving their favorable characteristics (e.g. large payload to robot weight ratio, stiffness, high dynamic performances), this research has conceived innovative families of parallel manipulators for special end-effector motions, such as translational, Schoenflies and rotational motions. In many cases, the proposed architectures exhibit decoupled output motion, i.e. each base-mounted motor directly actuates one of the output degrees of freedom, or are able to perform symmetric manipulation tasks, e.g. efficient manipulations of line-symmetric or plane-symmetric objects. Several of these mechanisms also exhibit constant and one-to-one input-output kinetostatic relations, so that the behavior in terms of force and velocity transmission is maximally regular throughout the workspace and singularities are potentially ruled out.
D. Singular configurations of mechanisms
Singularities limit or prevent the correct operation of mechanisms. The research in this area is focused on two topics. The first topic deals with the singularities of homokinetic-transmission-based spatial mechanisms. The key point consists in that input-output homokinesis does not necessarily entail uniformity in the global kinetostatic behavior: while the forces and velocities produced by the actuators may be available on the end-effector unscaled and undistorted throughout the workspace, the same may not be said for the forces and velocities transmitted within the mechanism, which may rise to unacceptable values. The second topic is aimed at providing an exhaustive taxonomy recognizing hierarchical levels in which the physical causes of different singular phenomena may be distinguished and more easily interpreted.
E. Dynamics analysis and balancing of spatial manipulators
The research in this area mainly focuses on the design of statically-balanced parallel manipulators, which requires zero external actions to be maintained at rest in any assumable configuration, as well on the elastodynamic behavior of balanced closed-loop mechanisms. The dynamic model of the Gough/Stewart Platform was also investigated, focusing on some issues, concerning the modeling of leg constraints, which were overlooked in a non-negligible part of the available literature related to the subject.
F. Compliant mechanisms
Compliant mechanisms achieve some or all of their motion and force transmission capabilities by virtue of the elastic deformation of some of their components. The research in this field is focused on identifying safe working areas, in which compliant mechanisms may operate in conditions of guaranteed stability. This problem is dealt with via Catastrophe Theory, a tool for the analysis of the topology of equilibrium configurations.
G. Optimal selection of components in servo-controlled machinery
A servo-controlled machine can perform tasks that involve coordinated or synchronized actuation of up to dozens or hundreds of servo-axes. The definition of an optimal and automatic procedure for component selection, in particular of the motor-reducer unit, is the key to an efficient design. This research focuses on two aspects: the development of an electromechanical model allowing electrical and mechanical losses to be precisely evaluated from rated data, thus requiring no experimental characterization; the implementation of an optimal selection procedure, called continuous optimization, based on the extension of a discrete commercial catalog to a continuous one, by means of data fitting on electromechanical parameters.
H. Mobile collaborative robotics
Nowadays, manufacturing systems need productivity, but also flexibility. Typically, industrial robots are used for repetitive tasks in a fixed working cell and the entire system is hardly reconfigurable. On the contrary, mobile robots equipped with lightweight robotic arms and sensors can work in an unstructured environment cooperating safely with humans and can be reprogrammed to perform different manipulation tasks, such as handling and transportation of objects and assembly operations. The research in this field focuses on solving motion planning problems for a collaborative mobile robot working in an unstructured environment.
