L. Lanari

L. Lanari
Sapienza University of Rome | la sapienza · Department of Computer, Automatic and Management Engineering "Antonio Ruberti"

PhD

About

84
Publications
14,325
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
1,616
Citations

Publications

Publications (84)
Article
Full-text available
Data-driven algorithms have proven to be effective for a variety of medical tasks, including disease categorization and prediction, personalized medicine design, and imaging diagnostics. Although their performance is frequently on par with that of clinicians, their widespread use is constrained by a number of obstacles, including the requirement fo...
Article
Full-text available
Tractor-trailer vehicles are affected by jackknifing, a phenomenon that consists in the divergence of the trailer hitch angle and ultimately causes the vehicle to fold up. For the case of backward motions, in which jackknifing can occur at any speed, we present a control method that drives the vehicle along generic reference Cartesian trajectories...
Article
Full-text available
We present a real time algorithm for humanoid 3D walking and/or running based on a Model Predictive Control (MPC) approach. The objective is to generate a stable gait that replicates a footstep plan as closely as possible, that is, a sequence of candidate footstep positions and orientations with associated timings. For each footstep, the plan also...
Article
Full-text available
We present a complete framework for the safe deployment of humanoid robots in environments containing humans. Proceeding from some general guidelines, we propose several safety behaviors, classified in three categories, i.e., override, temporary override, and proactive. Activation and deactivation of these behaviors is triggered by information comi...
Article
Full-text available
In order to guarantee precision and safety in robotic surgery, accurate models of the robot and proper control strategies are needed. Bayesian Neural Networks (BNN) are capable of learning complex models and provide information about the uncertainties of the learned system. Model Predictive Control (MPC) is a reliable control strategy to ensure opt...
Article
Full-text available
The feasibility region of a Model Predictive Control (MPC) algorithm is the subset of the state space in which the constrained optimization problem to be solved is feasible. In our recent Intrinsically Stable MPC (IS-MPC) method for humanoid gait generation, feasibility means being able to satisfy the dynamic balance condition, the kinematic constr...
Article
Full-text available
A linear-quadratic optimal control problem is considered for the infinite-dimensional model of a one-link flexible arm. Two boundary inputs are assumed to be available, namely the joint torque at the link base and a transverse force at the tip of the link. The problem is formulated and solved using semigroup theory and duality arguments. Simulation...
Conference Paper
Full-text available
We present an extension of our previously proposed IS-MPC method for humanoid gait generation aimed at obtaining robust performance in the presence of disturbances. The considered disturbance signals vary in a range of known amplitude around a mid-range value that can change at each sampling time, but whose current value is assumed to be available....
Conference Paper
Full-text available
It is common knowledge that tractor-trailer vehicles are affected by jackknifing, a phenomenon that consists in the divergence of the trailer hitch angle and ultimately causes the vehicle to fold up. For the case of backwards motion, in which jackknifing can also occur at low speeds, we present a control method that drives the vehicle along a refer...
Article
In this article, we present an intrinsically stable Model Predictive Control (IS-MPC) framework for humanoid gait generation that incorporates a stability constraint in the formulation. The method uses as prediction model a dynamically extended Linear Inverted Pendulum with Zero Moment Point (ZMP) velocities as control inputs, producing in real tim...
Article
Full-text available
In recent years Reinforcement Learning (RL) has achieved remarkable results. Nonetheless RL algorithms prove to be unsuccessful in robotics applications where constraints satisfaction is involved, e.g. for safety. In this work we propose a control algorithm that allows to enforce constraints over a learned control policy. Hence we combine Nonlinear...
Article
Capturability analysis of the linear inverted pendulum (LIP) model enabled walking with constrained height based on the capture point. In this paper, we generalize this analysis to the variable-height inverted pendulum (VHIP) and show how it enables 3-D walking over uneven terrains based on capture inputs. Thanks to a tailored optimization scheme,...
Preprint
Full-text available
Maintaining balance while walking is not a simple task for a humanoid robot because of its complex dynamics. The presence of a persistent disturbance makes this task even more challenging, as it can cause a loss of balance and ultimately lead the the robot to a fall. In this paper, we extend our previously proposed Intrinsically Stable MPC (IS-MPC)...
Article
Full-text available
We consider the known phenomenon of torque oscillations and motion instabilities that occur in redundant robots during the execution of sufficiently long Cartesian trajectories when the joint torque is instantaneously minimized. In the framework of on-line local redundancy resolution methods, we propose basic variations of the minimum torque scheme...
Preprint
Full-text available
We present a novel MPC framework for humanoid gait generation which incorporates an explicit stability constraint in the formulation. The proposed method uses as prediction model a dynamically extended LIP where ZMP velocities are the control inputs, producing in real time a gait (including footsteps with the associated timing) that realizes omnidi...
Article
Capturability analysis of the linear inverted pendulum (LIP) model enabled walking with constrained height based on the capture point. We generalize this analysis to the variable-height inverted pendulum (VHIP) and show how it enables 3D walking over uneven terrains based on capture inputs. Thanks to a tailored optimization scheme, we can compute t...
Article
Full-text available
This paper presents a Model Predictive Control (MPC) scheme capable of generating a 3D gait for a humanoid robot. The proposed method starts from an assigned sequence of footsteps and generates online the trajectory of both the Zero Moment Point and Center of Mass. Starting from the moment balance (neglecting rotations) we derive a model characteri...
Conference Paper
Full-text available
In this paper, we solve the gait planning problem by using the Flexible LIP model, which has been shown to be more realistic w.r.t. the LIP for cost-effective or compliant biped robots for gait generation. We extend a stable inversion approach to obtain bounded Center of Mass (CoM) reference trajectories and show several advantages compared to prev...
Article
Full-text available
It is in general complex to consider the complete robot dynamics when planning trajectories for bipedal locomotion. We present an approach to trajectory planning, with the classical Linear Inverted Pendulum Model (LIPM), that takes explicit consideration of the unstable dynamics. We derive a relationship between initial state and the control input...
Article
Full-text available
In this paper we propose a method to perform manual guidance with humanoid robots. Manual guidance is a general model of physical interaction: here we focus on guiding a humanoid by its hands. The proposed technique can be, however, used also for joint object transportation and other tasks implying human-humanoid physical interaction. Using a measu...
Conference Paper
This paper addresses the path following problem for an autonomous parafoil-payload system. The actuated dynamics of the system is first detailed. Local exponential stability of an input-output feedback linearizing control is proved, achieving a stable line following in the XY plane by using only lateral directional control input.
Article
Full-text available
Paragliders represent a light, low cost, space efficient means for autonomous transportation. They can be used for accurate delivering of payloads using inexpensive guidance and control modules. If equipped with proper sensor, it is possible to use paragliders for scientific observation during flight, such as chemical, thermal, meteorological, or b...
Chapter
The problem of controlling the motion of a one-link flexible robot arm is considered. A nonlinear dynamic model is derived assuming that the flexibility is represented by elastic springs along the link. Taking as output the end-effector angular position, the resulting zero-dynamics is unstable. Therefore, inversion-based controllers cannot be used...
Conference Paper
The recently introduced concept of system abstraction appears to be a promising tool for control purposes in a hierarchical framework. A challenging field of research is the so-called control implementation, i.e. how a high-level control law designed for an abstraction can be executed by the low-level original system. In this paper we extend, in a...
Conference Paper
Modeling and control of Large Scale Systems (LSS) have been deeply investigated in the last decades. Most methodologies used to study LSS, both for model reduction and control design, can be interpreted using geometric tools. In this paper we address the role of subspaces invariance in such methodologies and stress the limitations imposed by the in...
Conference Paper
The recently introduced concept of system abstraction appears to be a promising tool for control purposes in a hierarchical framework. While propagation of system's properties has been extensively studied, little investigation has been carried out on how a high-level control law is implemented on the low-level original system. In this paper we addr...
Article
Full-text available
We address the control problem for the Butterfly, an interesting example of 2-dof underactuated mechanical system. This robot consists of a butterfly- shaped rotational link on whose rim a ball rolls freely. The control objective is to stabilize the robot at a certain unstable equilibrium. To this end, exploiting the existence of heteroclinic traje...
Chapter
Accurate tracking of end-effector trajectories is one of the most demanding tasks for robot arms with flexible links. This problem is tackled here using regulation theory, considering the nonlinearities of the general dynamic model. The control design is presented in detail, including output trajectory generation, associated reference state computa...
Article
Full-text available
In this work is considered the problem of rest-to-rest motion in a desired pre-fixed time for planar flexible manipulators. We introduce a simple idea permitting the minimization of end-effector residual vibration when reaching a desired angular equilibrium position, in a pre-fixed desired travelling time. The results hold without considering inter...
Article
In this work we consider the problem of rest-to-rest motion for planar flexible multi-link manipulators. We introduce a simple idea permitting the cancellation of end-effector residual vibration when reaching a desired angular equilibrium position, in a fixed travelling time. No internal elastic damping effect is considered and the structure of the...
Article
A separation result for some kind of global stabilization via output feedback of a class of nonlinear systems, under the form of some stabilizability by state feedback on the one hand, and some unboundedness observability on the other hand is presented. They allow to design, for any domain of output initial condition, some dynamic output feedback c...
Conference Paper
The problem of global tracking control with disturbance attenuation of general Euler Lagrange systems without velocity measurement is still unsolved so far. In this note, on the basis of some appropriate choice of state coordinates, a solution is proposed for a particular class of such Euler Lagrange systems. Results are illustrated on the academic...
Conference Paper
A solution to the problem of global tracking control with disturbance attenuation of robot systems described by Euler-Lagrange equations has been presented by Battilotti et al. (1997) by full state feedback. In this paper, we show how recent results of Zhang et al. (1997) can be used to solve the same problem for so-called “Euler-Lagrange systems”...
Conference Paper
Full-text available
In this note the state trajectories and the optimal control resulting from a particular singular optimal control problem are studied. It is shown that the outer solution, in a singular perturbation approach, is a solution to a particular inverse system. This analysis allows to establish interesting relations with the exact output tracking control p...
Conference Paper
For a flexible slewing link whose tip angular position is required to track a desired trajectory it is possible to put in evidence some particular state trajectories which are naturally associated to the desired output time evolution. These can therefore be seen as a desired steady state internal behavior whose knowledge may help in physical interp...
Article
In a sinusoidal time reference trajectory, choosing a sinusoid as the desired output, the couple feedforward plus internal trajectory can be found. Once the output of interest was chosen a scalar parameter is uniquely defined provided the output is a function of the generalized positions only. Therefore, a family of state trajectories associated to...
Article
Existing dynamic output feedback stabilisation techniques of non-linear systems are applicable mainly when the unmeasurable part of the state enters linearly. Our objective in this paper is to identify a class of systems, non-linear with respect to the unmeasured variables, which are globally asymptotically stabilisable via dynamic output feedback....
Article
This paper deals with the problem of robust stabilization and disturbance attenuation via measured feedback, for a class of dissipative collocated distributed systems with disturbances affecting both the input and the measured output. The proposed solution is based on a direct ℒ2-gain characterization which avoids the usual Riccati equation argumen...
Article
The disturbance attenuation problem with global internal stability is solved for both rigid and elastic joint robots in the presence of unknown constant parameters. The proposed dynamic controller combines adaptive and H∞ control techniques.
Article
In this paper, we derive in a systematic manner, and using a unified framework, some recent results on global set point control of rigid and elastic joint robots using only position measurements. The controller design procedure consists of splitting up the overall stabilization task into two independent subproblems: one, a state-feedback stabilizat...
Conference Paper
Full-text available
In this paper a tracking controller for rigid robots is presented solving a disturbance attenuation problem with global internal stability in the general case of unknown constant parameters. By using the well-known property of linearity in the parameters for the rigid robot dynamic equations, adaptive and H<sub>∞</sub> control are combined successf...
Conference Paper
Full-text available
Proves that the complete dynamic model of robots with elastic joints can always be fully transformed into a linear, controllable, and input-output decoupled system through the use of nonlinear dynamic state feedback
Conference Paper
Full-text available
This paper presents an extension to elastic joint robots of a well-known result on the quadratic optimization of motion coordination and control obtained for rigid robots. In particular the aim is to minimize, for the set-point case, those applied torques which affect only the kinetic energy, or some linear combination. This problem is also of inte...
Conference Paper
Full-text available
The disturbance attenuation problem with global internal stability is solved for elastic joint robots in the general case of unknown constant parameters. By using results on the adaptive control of elastic joint robots, one can solve the problem of disturbance attenuation directly on the perturbed system by exploiting the property of linearity in t...
Article
In this paper it is shown that a linear controller solves the global set point control problem for a flexible joint robot via link position measurements. Moreover, the controller is shown to be robust with respect to uncertainties in the gravity term.
Conference Paper
Full-text available
Proposes a possible strategy for disturbance attenuation and set-point regulation for a rigid robot using the notion of L<sub>2</sub>-gain of a system. The authors discuss the use of H<sub>∞</sub> control for trajectory tracking and show, for the particular case of rigid robots, that a PD type controller is sufficient to render the closed loop syst...
Conference Paper
In this paper we consider the output feedback stabilization problem for a rigid spacecraft, in presence of unknown disturbances, due to the gravitational gradient. We assume that only the quaternions are available for measure. The obtained dynamic controller robustly, w.r.t. the considered disturbance, asymptotically stabilizes the system from the...
Article
Full-text available
In the present paper we propose a possible strategy for set point control and disturbance attenuation for a rigid robot using the notion of L2-gain of a system. In particular we discuss the use of H∞ control for trajectory tracking and we show, for the particular case of rigid robots, that a PD controller suffices to render the closed loop system f...
Conference Paper
In this paper the stabilization problem for a flexible slewing link is considered, leading to some interesting considerations about the use of positive real compensators. By modelling the structure motion as a set of first order differential equations on a proper Hilbert space, the authors study this problem in an infinite-dimensional setting by fo...
Conference Paper
A passivity and Lyapunov based approach for the control design is presented for the trajectory tracking problem of flexible joint robots. The basic structure of the proposed controller is the sum of a model-based feedforward and a model-independent feedback. Feedforward selection is analyzed and passivity theory is used to design a motor state-base...
Conference Paper
Full-text available
For the case of a controller composed of a model-dependent feedforward and a model-independent feedback for flexible joint robots, a stability analysis for different types of feedforward is presented. For feedforwards which differ in the amount of required model information and state measurements, and from the knowledge of a Lyapunov function for a...
Article
A general family of asymptotically stabilizing control laws is introduced for a class of nonlinear Hamiltonian systems. The inherent passivity property of this class of systems and the Passivity Theorem are used to show the closed loop input/output stability which is then related to the internal state space stability through an observability condit...
Conference Paper
The authors investigate the problem of how to achieve a cyclic joint behavior in redundant robots performing cyclic tasks, motivated by the fact that most singularity-free local resolution methods produce nonrepeatable joint motions. A controllability analysis of the inverse kinematic system makes it possible to recover the well-known repeatability...
Conference Paper
Full-text available
A family of asymptotically stabilizing tracking control laws was introduced by the author (1991) for a class of nonlinear Hamiltonian systems. These control laws all have the structure of a sum of a feedback design based on the passivity consideration and a feedforward obtained via a procedure that is closely related to plant inversion. In this pap...
Conference Paper
Full-text available
A general family of asymptotically stabilizing tracking control laws is introduced for a class of nonlinear Hamiltonian systems. The inherent passivity property of this class of systems ad the passivity theorem are used to show the closed-loop input/output stability which is then related to the internal state space stability through an observabilit...
Conference Paper
Full-text available
A general family of asymptotically stabilizing control laws is introduced for a class of nonlinear Hamiltonian systems. The inherent passivity property of this class of systems and the passivity theorem are used to show the closed-loop input/output stability which is then related to the internal state space stability through the stabilizability and...
Article
Full-text available
A robot trajectory planning problem is considered. Using smooth interpolating cubic splines as joint space trajectories, the path is parameterized in terms of time intervals between knots. A minimum time optimization problem is formulated under maximum torque and velocity constraints, and is solved by means of a first order derivative-type algorith...
Conference Paper
Full-text available
A lightweight robot has been built with the aim of testing advanced control algorithms and demonstrating the engineering feasibility of flexible arm control. The robot is a planar two-link manipulator, with revolute joints and a very flexible forearm. A description of this laboratory facility is given, including mechanical structure, actuators and...
Conference Paper
Full-text available
Inversion based techniques cannot be usually applied for end-effector trajectory tracking in flexible robotic structures, due to the non-minimum phase nature of the problem. However, considering finite-dimensional models, different choices of the actuation point and of the output location can lead to a minimum phase system for which inversion contr...
Chapter
Full-text available
In this paper we consider the problem of controlling via state-feedback the end-effector motion of a one-link flexible robot arm described by a nonlinear dynamic model. Due to the non-minimum phase nature of the system zero-dynamics, use of pure inversion-based techniques is unfeasible. In order to obtain stable tracking of desired tip trajectories...
Conference Paper
Full-text available
The exact eigenfunctions for the slewing link of a robot are found, taking into account a rotating inertia at the base and a payload at the tip. These derive from two equivalent formulations (pseudoclamped and pseudopinned) of the boundary value problem relative to the flexible slewing beam. The exactness of the solution makes it possible to prove...
Article
Full-text available
A robot trajectory planning problem is considered. Using interpolating cubic splines as joint space trajectories, the path is parametrized in terms of the n-1 time intervals between the η knots. A minimum time optimization problem is formulated under maximum dynamic torque and maximum velocity constraints and solved by means of a first order deriva...
Article
Full-text available
This paper describes the realization of a remote laboratory called REAL (Remote Experiments for Active Learning) Lab. Mainly designed for educational purposes, the REAL Lab allows the execution of robotic control experiments through the Internet. The client-server architecture of the telelaboratory is based on the Java technology, making the user i...

Network

Cited By