| 1. |
- Andersson, Kennet, 1979-, et al.
(författare)
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Assessment of cerebrospinal fluid outflow conductance using an adaptive observer-experimental and clinical evaluation
- 2007
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Ingår i: Physiological Measurement. - : IOP Publishing. - 0967-3334 .- 1361-6579. ; 28:11, s. 1355-1368
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Tidskriftsartikel (refereegranskat)abstract
- Idiopathic normal pressure hydrocephalus (INPH) patients have a disturbance in the dynamics of the cerebrospinal fluid (CSF) system. The outflow conductance, C, of the CSF system has been suggested to be prognostic for positive outcome after treatment with a CSF shunt. All current methods for estimation of C have drawbacks; these include lack of information on the accuracy and relatively long investigation times. Thus, there is a need for improved methods. To accomplish this, the theoretical framework for a new adaptive observer (OBS) was developed which provides real-time estimation of C. The aim of this study was to evaluate the OBS method and to compare it with the constant pressure infusion (CPI) method. The OBS method was applied to data from infusion investigations performed with the CPI method. These consisted of repeated measurements on an experimental set-up and 30 patients with suspected INPH. There was no significant difference in C between the CPI and the OBS method for the experimental set-up. For the patients there was a significant difference, −0.84 ± 1.25 µl (s kPa)−1, mean ± SD (paired sample t-test, p < 0.05). However, such a difference is within clinically acceptable limits. This encourages further development of this new real-time approach for estimation of the outflow conductance.
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| 2. |
- Andersson, Kennet, et al.
(författare)
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Real-time estimation of cerebrospinal fluid system parameters via oscillating pressure infusion
- 2010
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Ingår i: Medical and Biological Engineering and Computing. - : Springer. - 0140-0118 .- 1741-0444. ; 48:11, s. 1123-1131
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Tidskriftsartikel (refereegranskat)abstract
- Hydrocephalus is related to a disturbed cerebrospinal fluid (CSF) system. For diagnosis, lumbar infusion test are performed to estimate outflow conductance, C (out), and pressure volume index, PVI, of the CSF system. Infusion patterns and analysis methods used in current clinical practice are not optimized. Minimizing the investigation time with sufficient accuracy is of major clinical relevance. The aim of this study was to propose and experimentally evaluate a new method, the oscillating pressure infusion (OPI). The non-linear model of the CSF system was transformed into a linear time invariant system. Using an oscillating pressure pattern and linear system identification methods, C (out) and PVI with confidence intervals, were estimated in real-time. Forty-two OPI and constant pressure infusion (CPI) investigations were performed on an experimental CSF system, designed with PVI = 25.5 ml and variable C (out). The ARX model robustly estimated C (out) (mean C (out,OPI) - C (out,CPI) = 0.08 μl/(s kPa), n = 42, P = 0.68). The Box-Jenkins model proved most reliable for PVI (23.7 ± 2.0 ml, n = 42). The OPI method, with its oscillating pressure pattern and new parameter estimation methods, efficiently estimated C (out) and PVI as well as their confidence intervals in real-time. The results from this experimental study show potential for the OPI method and supports further evaluation in a clinical setting.
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| 3. |
- Freidovich, Leonid B, et al.
(författare)
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Experimental implementation of stable oscillations of the Furuta pendulum around the upward equilibrium
- 2007
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Ingår i: IEEE/RSJ International conference on intelligent robots and systems, 2007. IROS 2007. - Piscataway, N.J : IEEE Operations Center. - 9781424409129 ; , s. 171-176
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Konferensbidrag (refereegranskat)abstract
- Recently, a new technique for generating periodic motions in mechanical systems which have less actuators than degrees of freedom has been proposed. A motivating example for studying such motions is a dynamically stabilized walking robot, where the target trajectory is periodic, and one of the joints - the ankle joint - is unactuated, or weakly actuated. In this paper, the technique is implemented on the Furuta pendulum, an experimental testbed that is simpler than a walking robot but retains many of the key challenges - it is underactuated, open-loop unstable, and practical problems such as friction and velocity estimation must be overcome. We present a detailed description of the practical implementation of the controller. The experiments show that the technique is sufficiently robust to be useful in practice.
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| 4. |
- Grussler, Christian, et al.
(författare)
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Identification of externally positive systems
- 2018
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Ingår i: 2017 IEEE 56th Annual Conference on Decision and Control, CDC 2017. - 9781509028733 ; 2018-January, s. 6549-6554
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Konferensbidrag (refereegranskat)abstract
- We consider identification of externally positive linear discrete-time systems from input/output data. The proposed method is formulated as a semidefinite program, and is guaranteed to identify models that are ellipsoidal cone-invariant and, consequently, externally positive. We demonstrate empirically that this cone-invariance approach can significantly reduce the conservatism associated with methods that enforce internal positivity as a sufficient condition for external positivity.
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| 5. |
- Low, Emily MP, et al.
(författare)
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A biologically inspired method for vision-based docking of wheeled mobile robots
- 2007
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Ingår i: Robotics and Autonomous Systems. - Amsterdam : Elsevier. - 0921-8890 .- 1872-793X. ; 55:10, s. 769-784
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Tidskriftsartikel (refereegranskat)abstract
- We present a new control law for the problem of docking a wheeled robot to a target at a certain location with a desired heading. Recent research into insect navigation has inspired a solution which uses only one video camera. The control law is of the "behavioral" type in that all control actions are based on immediate visual information. Docking success under certain conditions is proved mathematically and simulation studies show the control law to be robust to camera intrinsic parameter errors. Experiments were performed for verification of the control law.
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| 6. |
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| 7. |
- Manchester, Ian R, et al.
(författare)
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Interception of a moving object with a specified approach angle by a wheeled robot : theory and experiment
- 2008
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Ingår i: 47th IEEE conference on decision and control, 2008 (CDC 2008). - : Institute of Electrical and Electronics Engineers. - 9781424431243 ; , s. 490-495
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Konferensbidrag (refereegranskat)abstract
- This paper presents a vision-based wheeled-robot navigation technique, termed circular navigation guidance (CNG), for the interception of a moving target from a specific angle. The guidance law is not split into path-planning and path-following stages, but is continuously updated based on immediately available information, making it useful even against a manoeuvring target, or where only incomplete information is available to the robot. This is achieved by converting a finite-time navigation problem into one of maintaining a certain geometric condition at all times. Detailed theoretical analysis provides a closed-form solution for the shape of the path the robot takes against a moving target. Experimental results are presented which show that CNG is robust and accurate under real-world conditions against a manoeuvring target.
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| 8. |
- Manchester, Ian R, et al.
(författare)
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Method for optical-flow-based precision missile guidance
- 2008
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Ingår i: IEEE Transactions on Aerospace and Electronic Systems. - Piscataway : IEEE Press. - 0018-9251 .- 1557-9603. ; 44:3, s. 835-851
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Tidskriftsartikel (refereegranskat)abstract
- A new precision guidance law is presented for three-dimensional intercepts against a moving target In contrast to previously published guidance laws, it does not require knowledge of the range to the target. This makes it appropriate for use on platforms which have an imaging device, such as a video camera, as a primary sensor. We prove that with idealized dynamic model, the guidance law results in zero miss distance, and a formula is given for impact angle error which tends to zero as does target speed, making this method particularly suitable against slow moving targets. Computer simulations are used to test the law with a more realistic model, with a video camera and optical-flow algorithm providing target information. It is shown to perform well compared with another law from the literature, despite requiring less information.
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| 9. |
- Manchester, Ian R., et al.
(författare)
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Stable Dynamic Walking over Rough Terrain Theory and Experiment
- 2011
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Ingår i: Robotics Research. - Berlin, Heidelberg : Springer. - 9783642194566 - 9783642194573 ; , s. 123-138
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Konferensbidrag (refereegranskat)abstract
- We propose a constructive control design for stabilization of non-periodic trajectories of underactuated mechanical systems. An important example of such a system is an underactuated "dynamic walking" biped robot walking over rough terrain. The proposed technique is to compute a transverse linearization about the desired motion: a linear impulsive system which locally represents dynamics about a target trajectory. This system is then exponentially stabilized using a modified receding-horizon control design. The proposed method is experimentally verified using a compass-gait walker: a two-degree-of-freedom biped with hip actuation but pointed stilt-like feet. The technique is, however, very general and can be applied to higher degree-of-freedom robots over arbitrary terrain and other impulsive mechanical systems.
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| 10. |
- Manchester, Ian R, et al.
(författare)
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Vision-based interception of a moving target by a mobile robot
- 2007
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Ingår i: Proceedings of the 2007 IEEE conference on control applications, vols 1-3. - New York : IEEE conference proceedings. - 9781424404421 ; , s. 397-402
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Konferensbidrag (refereegranskat)abstract
- We present a robot navigation technique, termed circular navigation guidance (CNG), which solves the challenging problem of intercepting a moving target from a specific angle, using only data from a video camera. The guidance law is not split into path-planning and path-following stages, but is continuously updated based on immediately available information, making it practical even against a manoeuvring target, or where only incomplete information is available to the robot. This is achieved by converting a finite-time navigation problem into one of maintaining a certain geometric condition at all tunes. Theoretical and experimental results are presented, which support CNG as a practically useful tool for robot navigation.
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