Author name cluster

Matteo Laffranchi

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20 papers

1 author row

ICRA Conference 2024 Conference Paper

An adaptable ankle trajectory generation method for lower-limb exoskeletons by means of safety constraints computation and minimum jerk planning

Raffaele Giannattasio
Stefano Maludrottu
Gaia Zinni
Elena De Momi
Matteo Laffranchi
Lorenzo De Michieli

This paper presents a method to compute smooth ankle trajectories for lower limb exoskeletons with powered ankle joints. The proposed approach defines ankle trajectories using four polynomial functions, each representing one of the four primary phases of gait. These polynomials are computed according to different safety constraints. During the single support phase, ground contact constraints are enforced. In the swing phase, an optimization problem is solved to achieve minimum jerk planning while respecting a set of equality and inequality constraints designed to minimize the risk of stumbling. The used approach focuses on making the ankle joint able to smoothly adapt in real-time to different walking styles defined by user-selected gait parameters such as step length and clearance. The primary aim is to improve the user experience by producing a secure and comfortable walking pattern. To validate the effectiveness of the proposed method, the new ankle trajectories were tested on a group of healthy volunteers using the TWIN lower limb exoskeleton.

IROS Conference 2024 Conference Paper

Design Improvements to the Float Upper-Limb Exoskeleton Better Mimics the Glenohumeral Complex Kinematics

Giulia Bodo
Federico Tessari
Gianluca Capitta
Luca De Guglielmo
Stefano Buccelli
Matteo Laffranchi

The shoulder glenohumeral complex stands out as one of the most complex structures within the human body. Designing a system that can effectively interface with it poses a significant challenge for researchers. In this study, we propose a methodology based on evaluating various metrics to assess the performance of new kinematic solutions for mimicking the glenohumeral complex. The proposed method is demonstrated on an existing design (Float) of an upper-limb exoskeleton. The results show a successful expansion of the reachable workspace and enhancement of the shoulder internal-external rotation. The improvements ensure the necessary range-of-motion for the patient’s natural use of the exoskeleton. Specifically, the existing Eulerian wrist architecture is replaced with a 3-degree-of-freedom RPY wrist to better resemble the glenohumeral shoulder joint complex. This study also explores the trade-offs between these enhancements and the desired system manipulability.

ICRA Conference 2022 Conference Paper

An Over-Actuated Bionic Knee Prosthesis: Modeling, Design and Preliminary Experimental Characterization

Lorenzo Guercini
Federico Tessari
Josephus J. M. Driessen
Stefano Buccelli
Anna Pace
Samuele De Giuseppe
Simone Traverso
Lorenzo De Michieli

A pressing challenge in the design of actuated knee prostheses is the ability to address the high variation of speed and torque requirements for the different types and phases of locomotion. This manuscript presents a novel over-actuated knee prosthesis which makes use of a dual motor actuation architecture to address this issue. It utilizes a high speed/low torque motor to enable natural and highly dynamical motion, as required for swing phases of walking, which is permanently engaged. In addition to this motor, a clutchable uni-directional low dynamics high torque motor is present to assist during the execution of tasks which demand active torque. Preliminary experimental validations have been performed on a healthy subject provided with an able-bodied adapter to demonstrate natural walk patterns and power-assisted sit-to-stand activities.

IROS Conference 2021 Conference Paper

Hannes Prosthesis Control Based on Regression Machine Learning Algorithms

Dario Di Domenico
Andrea Marinelli
Nicoló Boccardo
Marianna Semprini
Lorenzo Lombardi
Michele Canepa
Samuel Stedman
Alberto Dellacasa Bellingegni

The quality of life for upper limb amputees can be greatly improved by the adoption of poly-articulated myoelectric prostheses. Typically, in these applications, a pattern recognition algorithm is used to control the system by converting the recorded electromyographic activity (EMG) into complex multi-degrees of freedom (DoFs) movements. However, there is currently a trade-off between the intuitiveness of the control and the number of active DoFs. We here address this challenge by performing simultaneous multi-joint control of the Hannes system and testing several state-of-the-art classifiers to decode hand and wrist movements. The algorithms discriminated multi-DoF movements from forearm EMG signals of 10 healthy subjects reproducing hand opening-closing, wrist flexion-extension and wrist pronation-supination. We first explored the effect of the number of employed EMG electrodes on device performance through the classifiers optimization in terms of F1Score. We further improved classifiers by tuning their respective hyperparameters in terms of the Embedding Optimization Factor. Finally, three mono-lateral amputees tested the optimized algorithms to intuitively and simultaneously control the Hannes system. We found that the algorithms performances were similar to that of healthy subjects, particularly identifying the Non-Linear Regression classifier as the ideal candidate for prosthetic applications.

IROS Conference 2020 Conference Paper

Analysis, Development and Evaluation of Electro-Hydrostatic Technology for Lower Limb Prostheses Applications *

Federico Tessari
Renato Galluzzi
Andrea Tonoli
Nicola Amati
Matteo Laffranchi
Lorenzo De Michieli

This paper presents electro-hydrostatic actuation as a valid substitute of electro-mechanical devices for powered knee prostheses. The work covers the design of a test rig exploiting linear electro-hydrostatic actuation. Typical control laws for prosthesis actuators are discussed, implemented and validated experimentally. Particularly, this work focuses on position and admittance control syntheses enhanced with feed-forward friction compensation. Finally, the efficiency of the test rig is characterized experimentally and compared to that of classical electro-mechanical designs. It is demonstrated that the electro-hydrostatic prototype is able to fulfill its targets from a control perspective, while also having the potential to outperform electro-mechanical actuation in efficiency.

ICRA Conference 2020 Conference Paper

Gait patterns generation based on basis functions interpolation for the TWIN lower-limb exoskeleton *

Christian Vassallo
Samuele De Giuseppe
Chiara Piezzo
Stefano Maludrottu
Giulio Cerruti
Maria Laura D'Angelo
Emanuele Gruppioni
Claudia Marchese

Since the uprising of new biomedical orthotic devices, exoskeletons have been put in the spotlight for their possible use in rehabilitation. Even if these products might share some commonalities among them in terms of overall structure, degrees of freedom and possible actions, they quite often differ in their approach on how to generate a feasible, stable and comfortable gait trajectory pattern. This paper introduces three proposed trajectories that were generated by using a basis function interpolation method and by working closely with two major rehabilitation centers in Italy. The whole procedure has been focused on the concepts of a configurable walk for patients that suffer from spinal cord injuries. We tested the solutions on a group of healthy volunteers and on a spinal-cord injury patient with the use of the new TWIN exoskeleton developed at the Rehab Technologies Lab at the Italian Institute of Technology.

ICRA Conference 2015 Conference Paper

Damping control of variable damping compliant actuators

Navvab Kashiri
Gustavo A. Medrano-Cerda
Nikos G. Tsagarakis
Matteo Laffranchi
Darwin G. Caldwell

The development of variable impedance actuators (VIAs) has highlighted the need for proper control of passive impedance to attain suitable interaction performance. Until recently the regulation of the intrinsic impedance in VIAs is achieved in an open-loop model-based manner, mainly due to the lack of physical sensors capable of measuring impedance components such as stiffness and damping. Hence, the estimation of variable stiffness and damping has been explored, with the target to provide monitoring and feedback for potential closed loop control schemes. However, the use of the output of these estimators in the feedback control of variable impedance actuators has never been implemented/demonstrated in practice. This work contributes to the field with the development and experimental evaluation of a novel damping feedback control for a class of variable impedance compliant actuators able to realize a variable physical damping principle. The scheme is based on non-model-based damping estimation feedback to compensate model uncertainties in the action of an inner controller that uses a model-based friction estimator. Experimental results demonstrate the ability of the proposed scheme to replicate with good fidelity constant and time-varying damping levels.

ICRA Conference 2014 Conference Paper

Model-free force tracking control of piezoelectric actuators: Application to variable damping actuator

Jinoh Lee
Matteo Laffranchi
Navvab Kashiri
Nikos G. Tsagarakis
Darwin G. Caldwell

On a new demand of safe human-robot interaction for robotic applications, the Compact Compliant Actuator, named CompAct TM, is recently developed with physical compliance and active variable damping. In this mechanism, a desired physical damping behavior is realized by generating a friction force which is actively controlled by piezoelectric actuators (PEAs). However, nonlinearities such as hysteresis and creep effect make difficult to precisely control the generated piezoelectric force. This paper focuses on a development of precise force tracking controller for PEAs. A time delay estimation (TDE) using a force feedback is newly proposed to compensate a hysteretic behavior of the PEA and external uncertainties without a mathematical model. Thanks to the force-based TDE, the proposed control is accurate, computationally efficient and easily implementable on the real PEA system. The proposed control scheme is experimentally verified on the CompAct TM. Root-mean-square values of the steady-state error for step commands are kept as less than error ratio of 0. 13 % and the closed-loop system bandwidth for sinusoidal commands of 20 N stroke is confirmed as about 11 Hz under 100 N payload. In addition, the stability of the proposed control is proved to be bounded-input-bounded-output (BIBO) stable.

ICRA Conference 2014 Conference Paper

Physical interaction detection and control of compliant manipulators equipped with friction clutches

Navvab Kashiri
Matteo Laffranchi
Nikos G. Tsagarakis
Alessio Margan
Darwin G. Caldwell

This work focuses on the modeling and control of robotic manipulators powered by compliant actuation systems equipped with clutches for providing friction torque on demand. A novel control scheme is proposed for modulating the clutch friction torque in this particular class of compliant actuators to make the robot operate in “Rigid mode” when it does not interact with the environment to achieve high accuracy, bandwidth and controllability; meanwhile ensuring that the robot maximum static force is constrained to a maximum threshold permitting flexible reactions in potentially risky scenarios. The robot autonomously switches to “Compliant mode” (clutches off) when it interacts with external agents to exploit the advantages of compliance during contacts. Experimental results are presented to show the effectiveness of proposed approach in improving the robot performance (tracking accuracy) while still guaranteeing an interaction-friendly behavior when contact occurs.

ICRA Conference 2014 Conference Paper

Real-time damping estimation for variable impedance actuators

Navvab Kashiri
Matteo Laffranchi
Jinoh Lee
Nikos G. Tsagarakis
Lisha Chen
Darwin G. Caldwell

Recently-developed variable damping mechanisms have been exploited as a complement to compliant actuators. While accurate knowledge and control of generated damping is essential for achieving the desired performance, no physical sensor measuring the damping exists. This work introduces a novel non-model-based approach for the estimation of time-variant damping for variable impedance actuation systems. The approach is based only on torque and position/velocity measurements; without the knowledge of system's inputs, to ensure the estimation of both intentional and unintentional changes. Hence, a recursive least square estimator, modified for achieving a proper convergence for the estimation of time-variant parameters, is exploited. Experiments on a variable physical damping actuator are also presented to validate the performance of proposed approach.

IROS Conference 2013 Conference Paper

Link position control of a compliant actuator with unknown transmission friction torque

Lisha Chen
Matteo Laffranchi
Jinoh Lee
Navvab Kashiri
Nikos G. Tsagarakis
Darwin G. Caldwell

This paper proposes a control strategy for a compliant actuator, the CompAct™ actuator, which is equipped with semi active friction dampers in its transmission system. Both the transmission flexibility and the nonlinearity of the friction based damping torque makes the control of this actuator not a trivial task. This paper studies model of the presented actuator and the control problem of accurate link position tracking based on sliding mode approach that considers the friction torque as an uncertainty. Stability analysis and simulations highlight the effectiveness of the proposed controller in compensating for the deflections and unknown friction torque of the actuator. The performance of the controller is also validated by experiment results that demonstrate the tracking performance of the CompAct™ actuator achieved by the presented control strategy.

ICRA Conference 2013 Conference Paper

Optimal control for maximizing velocity of the CompAct™ compliant actuator

Lisha Chen
Manolo Garabini
Matteo Laffranchi
Navvab Kashiri
Nikos G. Tsagarakis
Antonio Bicchi
Darwin G. Caldwell

The CompAct™ actuator features a clutch mechanism placed in parallel with its passive series elastic transmission element and can therefore benefit from the advantages of both series elastic actuators (SEA) and rigid actuators. The actuator is capable of effectively managing the storage and release of the potential energy of the compliant element by the appropriate control of the clutch subsystem. Controlling the timing of the energy storage/release in the elastic element is exploited for improving motion control in this research. This paper analyses how this class of actuation systems can be used to maximize the link velocity of the joint. The dynamic model of the joint is derived and an optimal control strategy is proposed to identify optimal input reference profiles for the actuator (motor position/velocity and clutch activation timing) which permit the link velocity maximization. The effect of compliance of the joint on the performance of the system is studied and the optimal stiffness is analyzed.

IROS Conference 2012 Conference Paper

The role of physical damping in compliant actuation systems

Matteo Laffranchi
Lisha Chen
Nikos G. Tsagarakis
Darwin G. Caldwell

Recently, compliance has been considered as one of the key physical properties that a robot should incorporate to be able to physically interact with humans and uncertain environments. Apart from the improved ability of interaction, mechanical robustness and higher safety-related performances, compliance introduces underdamped oscillatory modes and reduces the mechanical natural frequency of the plant to be controlled making its control much more complex than that of conventional stiff actuators. To overcome these drawbacks, some recent works focus on the incorporation of physical damping within compliant actuators. This work presents an analysis for the quantitative evaluation of the effects of physical damping in compliant robotic joints to demonstrate the improvements (dynamic performance, stability, controllability, tracking precision and energy efficiency) which can be gained by incorporating physical damping in such flexible transmission systems. Simulation and experimental results validate that these benefits can effectively be achieved on an existing compliant actuator prototype with variable physical damping.

IROS Conference 2012 Conference Paper

Variable impedance actuators: Moving the robots of tomorrow

Bram Vanderborght
Alin Albu-Schäffer
Antonio Bicchi
Etienne Burdet
Darwin G. Caldwell
Raffaella Carloni
Manuel G. Catalano
Gowrishankar Ganesh

Most of today's robots have rigid structures and actuators requiring complex software control algorithms and sophisticated sensor systems in order to behave in a compliant and safe way adapted to contact with unknown environments and humans. By studying and constructing variable impedance actuators and their control, we contribute to the development of actuation units which can match the intrinsic safety, motion performance and energy efficiency of biological systems and in particular the human. As such, this may lead to a new generation of robots that can co-exist and co-operate with people and get closer to the human manipulation and locomotion performance than is possible with current robots.

ICRA Conference 2011 Conference Paper

A compact compliant actuator (CompAct™) with variable physical damping

Matteo Laffranchi
Nikos G. Tsagarakis
Darwin G. Caldwell

The new areas of technical exploitation of robotics systems has recently set new trends for the robotic actuation by demanding more versatile systems which can cope with unpredictable interactions within not well defined environments and work in close vicinity with the human. Following these trends, this work presents the development of a new actuation system with embodied characteristics such as passive compliance and variable physical damping. Compared to the other existing compliant linear or rotary actuators the proposed CompAct unit has the ability to regulate the oscillations induced by the introduction of the compliance by means of a variable physical damping actuator (VPDA) unit. Apart from facilitating the control the VPDA unit can assist in managing the energy transfer from/to the compliant module. The mechatronics, model and control scheme of the CompAct are analysed. The overall system is evaluated with experimental trials performed using a prototype unit. Preliminary results are presented to show that the unit and the proposed control scheme are capable of regulating the impedance components (stiffness and damping) within a wide range and with good fidelity.

ICRA Conference 2010 Conference Paper

A variable physical damping actuator (VPDA) for compliant robotic joints

Matteo Laffranchi
Nikos G. Tsagarakis
Darwin G. Caldwell

This paper introduces the development of a semi-active friction based variable physical damping actuator (VPDA) unit. The realization of this unit aims to facilitate the control of compliant robotic joints by providing physical variable damping on demand assisting on the regulation of the oscillations induced by the introduction of compliance. The mechatronics details and the dynamic model of the damper are introduced. The proposed variable damper mechanism is evaluated on a simple 1-DOF compliant joint linked to the ground through a torsion spring. This flexible connection emulates a compliant joint, generating oscillations when the link is perturbed. Preliminary results are presented to show that the unit and the proposed control scheme are capable of replicating simulated relative damping values with good fidelity.

ICRA Conference 2009 Conference Paper

A compact soft actuator unit for small scale human friendly robots

Nikos G. Tsagarakis
Matteo Laffranchi
Bram Vanderborght
Darwin G. Caldwell

This paper presents the development of a new compact soft actuation unit intended to be used in multi degree of freedom and small scale robotic systems such as the child humanoid robot “iCub” [1]. Compared to the other existing series elastic linear or rotary implementations the proposed design shows high integration density and wider passive deflection. The miniaturization of the newly developed high performance unit was achieved with a use of a new rotary spring module based on a novel arrangement of linear springs.

IROS Conference 2009 Conference Paper

Antagonistic and series elastic actuators: a comparative analysis on the energy consumption

Matteo Laffranchi
Nikos G. Tsagarakis
Ferdinando Cannella
Darwin G. Caldwell

Recent investigations show that compliant systems can be more safe and energy-efficient than conventional stiff actuated systems. As a result, researchers are increasingly implementing compliance within actuation systems using a variety of mechanisms. In general, these actuators can be grouped in 2 main categories. The first category includes all the actuation systems with a compliant element connected in series (SEA), while the second group contains all those systems that employ two actuators placed antagonistically. In both designs the ability to regulate the stiffness is essential in order to meet safety and/or performance demands. Energy consumption is a very important aspect to be considered, especially in autonomous robots. This paper presents a theoretical study on the energy consumption of variable stiffness actuators, comparing the amount of energy required in order to perform a certain task.

IROS Conference 2009 Conference Paper

Safe human robot interaction via energy regulation control

Matteo Laffranchi
Nikos G. Tsagarakis
Darwin G. Caldwell

This paper presents an energy-based control strategy to be used in robotic systems working closely or cooperating with humans. The presented method bounds the dangerous behavior of the robot during the first instants of the impact by limiting the energy stored into the system to a maximum imposed value. Two critical physical human robot interaction (pHRI) cases are studied, these are the collision either against a free or a clamped head. Safe energy values that can be used as reference were retrieved by analysing experimental data of energy absorption to failure of cranium bones and cervical spinal cords. The energy regulation control is implemented in a series elastic actuator prototype joint. The model and the control scheme of the system are analysed. The proposed control scheme is a position-based controller that adjusts the position trajectory reference in function of the maximum energy value imposed by the user. Preliminary results are presented to show that the actuator unit and this control scheme are capable of limiting the energy to a maximum imposed value.

IROS Conference 2009 Conference Paper

The mechanical design of the new lower body for the child humanoid robot 'iCub'

Nikos G. Tsagarakis
Bram Vanderborght
Matteo Laffranchi
Darwin G. Caldwell

The “iCub” is a robotic platform that was developed within the RobotCub European project to provide the cognition research community with an open “child-like” humanoid platform for understanding and development of cognitive systems [1]. In this paper we present the mechanical realization of the new lower body developed for the “iCub” child humanoid robot in order to keep up with the latest technology and solve mechatronic problems found in the previous version. The new lower body assembly demonstrates significant improvements over the old prototype including higher modularity, full joint state sensing and improved range of motion and torque capabilities. In particular the new leg and waist mechanisms to match the size and physical abilities of a 3 year old human child are introduced.