| 1. |
- Barbosa, Fernando S., et al.
(författare)
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Integrated motion planning and control under metric interval temporal logic specifications
- 2019
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Ingår i: 2019 18th European Control Conference, ECC 2019. - : Institute of Electrical and Electronics Engineers (IEEE). - 9783907144008 ; , s. 2042-2049
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Konferensbidrag (refereegranskat)abstract
- This paper proposes an approach that combines motion planning and hybrid feedback control design in order to find and follow trajectories fulfilling a given complex mission involving time constraints. We use Metric Interval Temporal Logic (MITL) as a rich and rigorous formalism to specify such missions. The solution builds on three main steps: (i) using sampling-based motion planning methods and the untimed version of the mission specification in the form of Zone automaton, we find a sequence of waypoints in the workspace; (ii) based on the clock zones from the satisfying run on the Zone automaton, we compute time-stamps at which these waypoints should be reached; and (iii) to control the system to connect two waypoints in the desired time, we design a low-level feedback controller leveraging Time-varying Control Barrier Functions. Illustrative simulation results are included.
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| 2. |
- Barbosa, Fernando S., 1992-, et al.
(författare)
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Provably safe control of Lagrangian systems in obstacle-scattered environments
- 2020
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Ingår i: 2020 59th IEEE Conference on Decision and Control (CDC). - : Institute of Electrical and Electronics Engineers (IEEE).
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Konferensbidrag (refereegranskat)abstract
- We propose a hybrid feedback control law that guarantees both safety and asymptotic stability for a class of Lagrangian systems in environments with obstacles. Rather than performing trajectory planning and implementing a trajectory-tracking feedback control law, our approach requires a sequence of locations in the environment (a path plan) and an abstraction of the obstacle-free space. The problem of following a path plan is then interpreted as a sequence of reach-avoid problems: the system is required to consecutively reach each location of the path plan while staying within safe regions. Obstacle-free ellipsoids are used as a way of defining such safe regions, each of which encloses two consecutive locations. Feasible Control Barrier Functions (CBFs) are created directly from geometric constraints, the ellipsoids, ensuring forward-invariance, and therefore safety. Reachability to each location is guaranteed by asymptotically stabilizing Control Lyapunov Functions (CLFs). Both CBFs and CLFs are then encoded into quadratic programs (QPs) without the need of relaxation variables. Furthermore, we also propose a switching mechanism that guarantees the control law is correct and well-defined even when transitioning between QPs. Simulations show the effectiveness of the proposed approach in two complex scenarios.
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| 3. |
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Beyond loss : dementia, identity, personhood
- 2014. - 1
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Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- Focuses on what people with progressive dementias still have, largely because of their connections with others, is new and important.Collects interdisciplinary essays by internationally established scholarsProvides new ways of understanding and dealing with dementiaComing to terms with dementia is one of the great challenges of our time. This volume of new interdisciplinary essays by internationally established scholars offers new ways of understanding and dealing with it. It explores views of dementia that go beyond the idea of loss, and rather envisions it as multilayered transformation and change of personhood and identity, and as development that mostly is socially shared with others. The studies collected here identify new empirical, theoretical, and methodological areas that will be crucial to future research and clinical practice concerned with age-related dementia. Three general themes are singled out as of particular importance and interest: persons and personhood, identity and agency, and the social and the communal.Readership: Students and researchers in: nursing, medicine, psychology, social work, gerontology, bioethics, memory research; people engaged in dementia organizations, caregivers, social workers.
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| 4. |
- Groen, Solveig Skovlund, et al.
(författare)
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A serological type II collagen neoepitope biomarker reflects cartilage breakdown in patients with osteoarthritis
- 2021
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Ingår i: Osteoarthritis and Cartilage Open. - : Elsevier BV. - 2665-9131. ; 3:4
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: There is an unmet medical need for biomarkers in OA which can be applied in clinical drug development trials. The present study describes the development of a specific and robust assay measuring type II collagen degradation (T2CM) and discusses its potential as a noninvasive translational biomarker. Methods: A type II collagen specific neoepitope (T2CM) was identified by mass spectrometry and monoclonal antibodies were raised towards the epitope, employed in a chemiluminescence immunoassay. T2CM was assessed in bovine cartilage explants with or without MMP-13 inhibitor, and explant supernatants were analyzed by Western blot. T2CM was measured in plasma samples from one study (n = 48 patients) where OA patients were referred to total knee replacement (TKR). Additionally, T2CM was quantified in serum from OA patients receiving salmon calcitonin treatment (sCT) (n = 50) compared to placebo (n = 57). Results: The T2CM assay was technically robust (13/4 % inter/intra-variation) and specific for the type II collagen fragment cleaved by MMP-1 and -13. The MMP-13 inhibitor reduced the T2CM release from bovine cartilage explants receiving catabolic treatment. These results were confirmed by Western blot. In human end-stage OA patients (scheduled for TKR), the T2CM levels were elevated compared to moderate OA (p<0.004). The OA patients receiving sCT had lower levels of T2CM compared to placebo group after 1, 6, and 24 months of treatment (p = 0.0285, p = 0.0484, p = 0.0035). Conclusions: To our knowledge, T2CM is the first technically robust serological biomarker assay which has shown biological relevance in ex vivo models and OA cohorts. This suggests that T2CM may have potential as a translational biomarker for cartilage degradation.
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| 5. |
- Lindemann, Kristina, et al.
(författare)
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Serum lipids and endometrial cancer risk: results from the HUNT-II study.
- 2009
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Ingår i: International journal of cancer. Journal international du cancer. - : Wiley. - 1097-0215. ; 124:12, s. 2938-41
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Tidskriftsartikel (refereegranskat)abstract
- Obesity is a major risk factor for endometrial cancer. Still, the association of obesity-related metabolic factors, such as serum lipids and lipoprotein levels, is unclear. We prospectively examined the association of serum levels of triglycerides, total cholesterol, low-density lipoprotein cholesterol, non-high-density lipoprotein (non-HDL), and HDL cholesterol with endometrial cancer risk among 31,473 women. During 9 years of follow-up, 100 cases of endometrial cancer were identified by linkage to the Cancer Registry of Norway. There was a positive association of serum triglyceride levels with endometrial cancer risk. Comparing the highest to the lowest quartile of triglycerides, the age-adjusted hazard ratio was 2.34 (95% CI: 1.04-5.28), and further adjustment for body mass index attenuated the association (hazard ratio 1.79, 95% CI: 0.79-4.05). For total serum cholesterol, low-density lipoprotein cholesterol and HDL cholesterol there were no associations with endometrial cancer risk, either without or after adjustment for body mass index. Serum triglyceride levels were positively associated with the risk of endometrial cancer, and some of the association seems to be attributable to obesity. Apart from higher estrogen levels produced in adipose tissue, mechanisms more specifically related to triglycerides may also be involved in endometrial cancer. Further prospective studies on this subject are needed to better understand the association of blood lipids with endometrial cancer risk.
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| 6. |
- Lindemann, Lars, et al.
(författare)
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Anomaly Detector Metrics for Sensor Data Attacks in Control Systems
- 2018
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Ingår i: 2018 Annual American Control Conference (ACC). - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 153-158
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Konferensbidrag (refereegranskat)abstract
- We investigate worst-case impacts of stealthy full sensor attacks against linear control systems under a general class of anomaly detectors. We show that the worst-case impact scales with a parameter that is solely determined by the number of sensors in the plant, the detector used, and its tuning. Therefore, we obtain a general metric to compare the performance of detectors of this class of detectors under the investigated sensor attack, which is independent of the plant dynamics and applies to all linear systems with the same number of sensors.
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| 7. |
- Lindemann, Lars, et al.
(författare)
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Barrier Function-based Collaborative Control ofMultiple Robots under Signal Temporal Logic Tasks
- 2020
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Ingår i: IEEE Transactions on Control of Network Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 2325-5870. ; 7:4, s. 1916-1928
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Tidskriftsartikel (refereegranskat)abstract
- Motivated by the recent interest in cyber-physicaland autonomous robotic systems, we study the problem ofdynamically coupled multi-agent systems under a set of signaltemporal logic tasks. In particular, the satisfaction of each ofthese signal temporal logic tasks depends on the behavior of adistinct set of agents. Instead of abstracting the agent dynamicsand the temporal logic tasks into a discrete domain and solvingthe problem therein or using optimization-based methods, wederive collaborative feedback control laws. These control laws arebased on a decentralized control barrier function condition thatresults in discontinuous control laws, as opposed to a centralizedcondition resembling the single-agent case. The benefits of ourapproach are inherent robustness properties typically present infeedback control as well as satisfaction guarantees for continuous-time multi-agent systems. More specifically, time-varying controlbarrier functions are used that account for the semantics of thesignal temporal logic tasks at hand. For a certain fragment ofsignal temporal logic tasks, we further propose a systematic wayto construct such control barrier functions. Finally, we showthe efficacy and robustness of our framework in an experimentincluding a group of three omnidirectional robots
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| 8. |
- Lindemann, Lars, et al.
(författare)
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Control Barrier Functions for Multi-Agent Systems under Conflicting Local Signal Temporal Logic Tasks
- 2019
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Ingår i: IEEE Control Systems Letters. - : IEEE Institute of Electrical and Electronics Engineers Inc.. - 2475-1456. ; 3:3, s. 757-762
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Tidskriftsartikel (refereegranskat)abstract
- Motivated by the recent interest in cyber-physical and interconnected autonomous systems, we study the problem of dynamically coupled multi-agent systems under conflicting local signal temporal logic (STL) tasks. Each agent is assigned a local STL task regardless of the tasks that the other agents are assigned to. Such a task may be dependent, i.e., the satisfaction of the task may depend on the behavior of more than one agent, so that the satisfaction of the conjunction of all local tasks may be conflicting. We propose a hybrid feedback control strategy using time-varying control barrier functions. Our control strategy finds least violating solutions in the aforementioned conflicting situations based on a suitable robustness notion and by initiating collaboration among agents.
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| 9. |
- Lindemann, Lars, et al.
(författare)
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Control Barrier Functions for Multi-Agent Systemsunder Conflicting Local Signal Temporal LogicTasks
- 2019
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Ingår i: IEEE LCSS Letters. - 2475-1456.
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Tidskriftsartikel (refereegranskat)abstract
- Abstract—Motivated by the recent interest in cyber-physicaland interconnected autonomous systems, we study the problemof dynamically coupled multi-agent systems under conflictinglocal signal temporal logic tasks. Each agent is assigned a localsignal temporal logic task regardless of the tasks that the otheragents are assigned to. Such a task may be dependent, i.e., thesatisfaction of the task may depend on the behavior of more thanone agent, so that the satisfaction of the conjunction of all localtasks may be conflicting. We propose a hybrid feedback controlstrategy using time-varying control barrier functions. Our controlstrategy finds least violating solutions in the aforementionedconflicting situations based on a suitable robustness notion andby initiating collaboration among agents.
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| 10. |
- Lindemann, Lars, et al.
(författare)
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Control Barrier Functions for Nonholonomic Systems under Risk Signal Temporal Logic Specifications
- 2020
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Ingår i: Proceedings of the IEEE Conference on Decision and Control. - : Institute of Electrical and Electronics Engineers Inc.. ; , s. 1422-1428
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Konferensbidrag (refereegranskat)abstract
- Temporal logics provide a formalism for expressing complex system specifications. A large body of literature has addressed the verification and the control synthesis problem for deterministic systems under such specifications. For stochastic systems or systems operating in unknown environments, however, only the probability of satisfying a specification has been considered so far, neglecting the risk of not satisfying the specification. Towards addressing this shortcoming, we consider, for the first time, risk metrics, such as (but not limited to) the Conditional Value-at-Risk, and propose risk signal temporal logic. Specifically, we compose risk metrics with stochastic predicates to consider the risk of violating certain spatial specifications. As a particular instance of such stochasticity, we consider control systems in unknown environments and present a determinization of the risk signal temporal logic specification to transform the stochastic control problem into a deterministic one. For unicycle-like dynamics, we then extend our previous work on deterministic time-varying control barrier functions.
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