1,721,007 research outputs found
Framework for Static and Dynamic Friction Identification for Industrial Manipulators
Full text linkEven if friction modeling and compensation is a very important issue for manipulators, quite simple models are often adopted in the industrial world to avoid too heavy solutions from the computational point of view, and because of the difficulty of finding and identifying a model applicable in any motion condition. This article proposes a general framework for friction identification for industrial manipulators with the goal of solving the previous problems through: first, a complete procedure managing all the steps from data acquisition and model identification up to the generation of the code for the implementation into the robot software architecture, second, the possibility of adopting static or dynamic models of different complexity, and third, the development of some modifications in the dynamic friction model so to achieve a reliable friction torque estimation at any velocity and acceleration regime, avoiding unfeasible peaks and overestimation. The results of experimental tests carried out for different manipulators prove the validity and generality of the proposed friction model and identification procedure
Impact Control Under Elastic/Plastic Deformations
No full textThe paper deals with the problem of controlling the impact between a mechanical system, having n degrees of freedom, and a body possibly subject to elastic/plastic. deformations. Goal of the proposed control scheme is the regulation of the impact force to a desired vaine, while imposing a prescribed configuration to the system, even in presence of possible plastic deformations of the body. The behaviour of the controlled system is analysed in the three different situations that may occur: (i) non contact between the mechanical system and the body, (ii) contact with pun; elastic impact, and (iii) contact with plastic do-formation of the; body. Simulation results, which confirm the theoretical analysis in the case of a planar 2-dof manipulator striking an external surface, are reported in the paper
Robust trajectory tracking for flexible piezoelectric structures
No full textThe robust trajectory tracking problem is stated and solved for a thin planar sandwich structure, consisting of two piezoelectric films, mounted on an elastic support. The proposed controller asymptotically stabilises the structure, and guarantees for the generalised co-ordinates, which are introduced to approximately describe the shape of the structure, an arbitrarily bounded steady-state tracking error. The considered reference trajectories are derivable functions of time, with time derivatives bounded in norm from the first up to the third order. Analytic knowledge of the dynamic model of the structure is not necessary for the design of the controller, which is robust with respect to variations of the geometrical and physical parameters of the structure, and provides the steady-state gravity force rejection
Dynamic model and control of a rolling disk
No full textAim of the paper is the control of a disk, which is rolling without slipping on an unknown curve. After the determination of the dynamic model of the rolling disk, on which an external torque is applied, a control algorithm is proposed for the regulation of the position of the disk, i.e., of its distance along the curve from the 'initial point', to a desired value. The effectiveness of the algorithm, which does not require the complete knowledge of the dynamic model of the system (i.e., of the analytic expression of the curve), is confirmed by the reported simulation results
Control of a Series of Carts Subject to Nonsmooth Unilateral Impacts
No full textThe paper deals with the control of a series of carts, free to move along parallel guides, which can be dragged by the first one (i.e., by the only actuated cart). The goal is the design of a control law that lets all the carts, which are subject to nonsmooth, unilateral impacts, asymptotically move along the guides at an assigned, common velocity. The problem is solved by a very simple control law, and the properties of the controlled system, which are analytically proven, are confirmed by some simulation results that are reported and discussed in the paper
Impact model and control of two multi-dof cooperating manipulators
No full textThe problem of modeling and controlling the impact between the end-effectors of two multi-DOF cooperating manipulators is considered in this paper, with the goal of designing a control scheme that brings the end-effectors in a steady-state contact with each other and regulates the robots to desired configurations, with an assigned contact force. The equations of motion of the robot are determined both in the contact condition and in the noncontact one. One controller is designed for each manipulator, independently of the other one, including a reduced-order observer for the estimation of the impact-induced forces; in particular, each controller requires only the position and velocity measurements of the robot on which it is implemented (no force measurement is necessary). Such a control scheme, which works correctly also when the robots do not interact (no switching condition is present), allows the global asymptotic regulation of the cooperating robot arms to the desired configuration, with the prescribed contact force, as it is analytically proven in the paper
On the Design of a Position Feedback Control Law for a Simple Mechanical System Subject to Impacts
No full textThe control of mechanical systems subject to smooth impacts is considered in this paper. As the dynamic model of the mechanical system varies in dependence on the condition of contact or non-contact, a family of dynamic compensators from position measurements is first derived, thus guaranteeing the asymptotic stability in the two different conditions. As the system can switch between the two conditions an arbitrary number of times, the stability of the overall system is not guaranteed by the stability in the two separate phases; hence, a Lyapunov approach is proposed in order to guarantee the asymptotic stability of the overall system independently of the number of transitions between the two phases. Second, it is shown how to select among the considered family of compensators the one that reduces as much as possible the effects of the impacts on the trajectory of the system, while considering a regulation problem, with zero steady-state regulation error. Both simulation and experimental results have been carried out showing the effectiveness of the proposed technique
Application of a PD controller on two mating gears with elasticity and backlash
No full textThe paper deals with the problems related to the mechanical gears, which are commonly used for manipulators and servomechanisms, when elasticity and backlash affect their connection. The dynamic model of two mating gears is determined in three different cases: in the ideal case, in which the gears are rigid and no backlash is present; when the gears are flexible, in absence of backlash; in a realistic case, in which both the elasticity of the gears and the presence of backlash are to be taken into account. The same control algorithm, a PD one, is then applied to the three different cases, under the assumption that only the position and the velocity of the driving gear are available for feedback. The properties of the solutions of the closed-loop systems thus obtained are studied and analytically proven in the paper. Some simulation results complete and confirm the analysis
Impact control of a single-link robot striking different environments: Theoretical and experimental investigation
No full textThe paper deals with the impact control of a single-link rigid robot, striking different environments, i.e., having different elastic/plastic characteristics. The control goal is bringing the link in a stable contact with different external environments, reproducing elastic, rigid, or quasi-rigid impact conditions, and guaranteeing a desired value for the steady-state position of the link, compatible with the contact. The proposed control scheme, for which neither the impact time detection, nor force measurements are required, employs a reduced-order observer for the estimation of the impact-induced forces, to be compensated by the feedback control law. It is analytically shown that the complete knowledge of the parameters of the link dynamic model is not strictly necessary for the implementation of the proposed control scheme, whose validity is proven also experimentally by means of a simple test-bed, reproducing the considered case. The results of the carried out tests are reported and discussed in the paper, and compared with those relative to the application of a simple PD control law. © 2000 EUCA
Control of a Series of Carts in the Case of Nonsmooth Unilateral Impacts
No full textThe goal of this work is the control of a series of carts, dragged by the first one (the only actuated cart) along parallel tracks. A very simple control law is proposed to let all the carts, which are subject to nonsmooth, unilateral impacts, move asymptotically at an assigned, common velocity. The properties of the controlled system are analytically proven and confirmed by simulation result
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