15 research outputs found
Model Predictive Control Schemes for Consensus in Multi-Agent Systems with Single- and Double-Integrator Dynamics
No full textIn this paper we address the problem of driving a group of agents towards a consensus point when the agents have a discrete-time single- or double-integrator dynamics and the communication network is time-varying. We propose decentralized Model Predictive Control (MPC) schemes that take into account constraints on the agents' input and show that they guarantee consensus under mild assumptions. Since the global cost does not decrease monotonically, it cannot be used as a Lyapunov function for proving convergence to consensus. For this reason, our proofs exploit geometric properties of the optimal path followed by individual agents
Contractive distributed MPC for consensus in networks of single and double integrators
No full textIn this paper we propose an application of distributed model predictive control techniques to the problem of driving a group of autonomous agents towards a consensus point, i.e. a negotiated position in their state space. Agents are assumed to be governed by discrete-time single- or double-integrator dynamics and the communication network can be directed and time-varying. Our control protocols are called contractive due to a specific constraint imposed on the agents' state path. Consensus is formally proven, also in presence of bounds on the norm of the inputs, by means of a geometrical analysis of the optimal paths
Model Predictive Control Schemes for Consensus in Multi-agent Systems with Integrator Dynamics and Time-varying Communication
No full textIn this paper we address the problem of driving a group of agents towards
a consensus point when agents have a discrete-time integrator dynamics and
the communication graph is time-varying. We propose two decentralized Model
Predictive Control (MPC) schemes that take into account constraints on the
agents’ inputs and show that they guarantee consensus under mild assumptions.
Since the global cost does not decrease monotonically, it cannot be used as
a Lyapunov function for proving convergence to consensus. Rather, our proofs
exploit geometric properties of the optimal path followed by individual agents
A Model Predictive Control Scheme for Consensus in Multi-Agent Systems with Single-Integrator Dynamics and Input Constraints
No full textIn this paper we address the problem of driving
a group of agents towards a consensus point when agents have
a discrete-time single-integrator dynamics and the communication
graph is undirected and time-varying. We propose a
decentralized Model Predictive Control (MPC) scheme that
takes into account constraints on the agent inputs and show
that it guarantees consensus under mild assumptions. Since the
global cost does not decrease monotonically, it cannot be used as
a Lyapunov function for proving consensus. Rather, our proof
exploits geometric properties of the optimal path followed by
individual agents
Control schemes based on the wave equation for consensus in multi-agent systems with double-integrator dynamics
No full textIn this paper, we consider the problem of driving
a group of agents communicating through an undirected and
weighted network towards a consensus point. We assume that
agents obey to double-integrator dynamics and study decentralized
control schemes for consensus of the position variables. In
particular we revisit control policies proposed in (Xie and Wang, 2007) and (Ren and Atkins, 2005)
in the unified framework of Partial difference Equations over
graphs and highlight the link between the closed-loop system
dynamics and the damped wave equation describing the motion
of a free elastic beam
Neuromuscular evaluation of post-orthodontic stability: an experimental protocol
No full textTo prevent relapse after orthodontic treatment, retention is often considered indispensable. Soft tissues are thought to have a significant influence on dental movements. To quantify the influence of masticatory muscles on post-treatment relapse, and in an attempt to avoid unnecessary procedures, 2 male orthodontic patients (13 and 30 years old at debonding) were followed up. The patients completed 2 years of fixed orthodontic treatment and received no post-orthodontic retention. After 1 week and again after 6 months, alginate impressions of dental arches and a surface electromyographic (EMG) assessment of the masseter and temporalis muscles during maximum voluntary clenching were performed. The younger patient received surface EMG monitoring once a month for the first 6 months and at the 1-year follow-up appointment. Arch dimensions and the 3-dimensional inclination of the facial axis of the clinical crown (FACC) were measured using a computerized digitizer. Symmetry in muscular contraction was measured by the percentage overlapping coefficient (POC), and potential lateral displacing components were assessed by the torque coefficient (TC). At the 6-month follow-up, no clinical modifications were observed. Quantitative evaluation assessed that arch dimensions had changed slightly (up to 1 mm). While the adolescent patient had no modifications in FACC inclinations, the 30-year-old patient showed significant alterations (up to 18 degrees). In all examinations of the adolescent patient, POC was higher than 86% and TC was lower than 10%. In the adult, POC was inside the normal range, while all TCs were higher than 10.5%. The larger TC measured in the adult may explain the larger modifications in the 3-dimensional position of his dental crowns. In conclusion, a surface EMG assessment may help in the detection of patients who might need post-orthodontic retention
Uncemented total hip arthroplasty in patients younger than 20 years
No full textBackground: Several diseases may lead to advanced hip disease and cause disabling symptoms in adolescents. In literature there is no consensus which is the optimal surgical treatment for young adults with end-stage osteoarthritis. The purpose of this study was to assess the clinical and radiological outcomes of uncemented total hip arthroplasty for the treatment of end-stage hip arthritis in patients younger than 20 years at a minimum follow-up of ten years.Methods: We have retrospectively evaluated 24 patients who were 20 years or younger and underwent uncemented total hip arthroplasty. Minimum follow-up was 10 years. Clinical outcome was measured using the Harris Hip Score, Western Ontario McMaster, and the Short-Form 36. Hip calcification was evaluated using Brooker classification, while osteolysis was examined at the final follow-up according to the subdivision of Gruen.Results: The mean preoperative Harris Hip Score was 36.94 points and improved to 92.3, and the mean preoperative WOMAC score improved from 84.72 to 28.45 The Mental Component score-SF-36 improved from a preoperative mean of 26.23 points to 58.96, while the Physical Component score-SF-36 improved from a preoperative mean of 26.38-49.95. All components were stable and osseo-integrated. Radiolucent lines were not present in any hips. We noted the presence of 4 calcifications. No patient needed implant revision. The only complication was an intraoperative femoral fracture.Conclusion: Total hip arthroplasty is a safe and reliable procedure for the treatment of end-stage arthritis in the young that provides good to excellent mid-term results. (C) 2016 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved
Pediatric flexible flatfoot: Does obesity influence the outcomes of arthroereisis?
No full textBACKGROUND Childhood obesity has emerged in the last decades as an important public health problem worldwide. Although relationships between obesity and flatfoot have been shown, no studies have investigated the influence of obesity on arthroereisis outcomes. AIM To evaluate correlations between childhood overweight/obesity and clinical and radiographic outcomes after subtalar arthroereisis with self-locking implants. METHODS This retrospective study included one hundred and sixty-nine pediatric patients (10–14 years old) who underwent subtalar arthroereisis (PEEK PitStop® device) for severe flexible flatfoot. Exclusion criteria were additional procedures, revision of previous corrective surgeries, rigid flatfoot with severe deformity, and neurological or post-traumatic flatfoot. Preoperative/postoperative European Foot and Ankle Society (EFAS) and visual analogue scale (VAS) scores were determined; radiographic assessment was conducted on weight-bearing foot X-rays: Kite angle, first metatarsal-talus angle, Meary angle, calcaneal pitch angle and lateral talo-calcaneal angle were analyzed. RESULTS EFAS and VAS scores improved post-operatively in the whole population. Only seven cases with complications were reported. Radiographic assessment revealed an improvement in all angles. Statistical analysis demonstrated that the impact of obesity was significant on arthroereisis outcomes: Relationships were reported between BMI and postoperative EFAS/VAS scores, postoperative calcaneal pitch angle, Kite angle, Meary angle and talo-first metatarsal angle. CONCLUSION Although arthroereisis represents a very effective and valid treatment for flatfoot both in normal weight and obese children, obesity significantly influences clinical and radiographic outcomes of arthroereisis, and obese children tend to perceive more pain and discomfort
Model Predictive Control Schemes for Consensus in multi-Agent Systems with Integrator Dynamics and Time-Varying Communication
No full textIn this paper we address the problem of driving a group of agents towards a consensus point when agents have a discrete-time integrator dynamics and the communication graph is time-varying. We propose two decentralized Model Predictive Control (MPC) schemes that take into account constraints on the agents’ inputs and show that they guarantee consensus under mild assumptions. Since the global cost does not decrease monotonically, it cannot be used as a Lyapunov function for proving convergence to consensus. Rather, our proofs exploit geometric properties of the optimal path followed by individual agents.SCI-STI-GFTNancy, France, 20-21 June
