Inverse and variable structure trajectory control of a flexible robotic manipulator

This thesis introduces two schemes that control the end effector trajectory and stabilize a two-link flexible robotic arm. They are (i) The Inverse Trajectory Control scheme and (ii) The Variable Structure System (VSS) scheme; The Inverse Trajectory Control scheme develops a control law based on the inversion of an input-output map. The stable maneuver of the arm depends on the stability of the zero dynamics of the system. A linear stabilizer is designed for the final capture of the terminal state and stabilization of the elastic modes; The second scheme incorporates a Variable Structure Control law which includes robustness in its design. A discontinuous output control law is derived which accomplishes the desired trajectory tracking of the output. This control scheme involves two phases, the \u27reaching phase\u27 and the \u27sliding phase\u27; Simulation results are presented to show that large maneuvers can be performed in the presence of payload uncertainty. (Abstract shortened with permission of author.)

Acute kidney injury in patients treated with immune checkpoint inhibitors

Background: Immune checkpoint inhibitor-associated acute kidney injury (ICPi-AKI) has emerged as an important toxicity among patients with cancer. Methods: We collected data on 429 patients with ICPi-AKI and 429 control patients who received ICPis contemporaneously but who did not develop ICPi-AKI from 30 sites in 10 countries. Multivariable logistic regression was used to identify predictors of ICPi-AKI and its recovery. A multivariable Cox model was used to estimate the effect of ICPi rechallenge versus no rechallenge on survival following ICPi-AKI. Results: ICPi-AKI occurred at a median of 16 weeks (IQR 8-32) following ICPi initiation. Lower baseline estimated glomerular filtration rate, proton pump inhibitor (PPI) use, and extrarenal immune-related adverse events (irAEs) were each associated with a higher risk of ICPi-AKI. Acute tubulointerstitial nephritis was the most common lesion on kidney biopsy (125/151 biopsied patients [82.7%]). Renal recovery occurred in 276 patients (64.3%) at a median of 7 weeks (IQR 3-10) following ICPi-AKI. Treatment with corticosteroids within 14 days following ICPi-AKI diagnosis was associated with higher odds of renal recovery (adjusted OR 2.64; 95% CI 1.58 to 4.41). Among patients treated with corticosteroids, early initiation of corticosteroids (within 3 days of ICPi-AKI) was associated with a higher odds of renal recovery compared with later initiation (more than 3 days following ICPi-AKI) (adjusted OR 2.09; 95% CI 1.16 to 3.79). Of 121 patients rechallenged, 20 (16.5%) developed recurrent ICPi-AKI. There was no difference in survival among patients rechallenged versus those not rechallenged following ICPi-AKI. Conclusions: Patients who developed ICPi-AKI were more likely to have impaired renal function at baseline, use a PPI, and have extrarenal irAEs. Two-thirds of patients had renal recovery following ICPi-AKI. Treatment with corticosteroids was associated with improved renal recovery

Variable Structure Trajectory Control of an Elastic Robotic Arm

This article introduces a variable structure system scheme to control the end effector trajectory of a two-link flexible robotic arm. Because control of the actual tip position leads to unstable zero dynamics, control of points in the neighborhood of the tip is considered. An output is chosen as the sum of the joint angle and tip elastic deformation times a constant factor for each link. For the chosen output, a discontinuous output control law is derived based on the variable structure theory. The control law thus derived accomplishes the desired trajectory tracking of the output. A linear stabilizer is designed using the pole assignment technique for the final capture of the terminal state and stabilization of the elastic modes. Simulation results are presented to show that in the closed-loop system large maneuvers can be performed in the presence of payload uncertainty, thereby exhibiting the robustness of the controller

Inverse Trajectory Control and Zero Dynamics Sensitivity of an Elastic Manipulator

The question of control of the end effector trajectory and stabilization of a two-link flexible robotic arm is considered. A control law based on the inversion of an input-output map is obtained. The outputs are chosen as the sum of the joint angle and tip elastic deformation times a constant factor for each link. The stable maneuver of the arm critically depends on the stability of the zero dynamics of the system. Stability of the zero dynamics is shown to be sensitive to the choice of the constant multiplying factor, which explains the difficulty in controlling the tip position. A critical value of the constant factor for control is obtained and this corresponds to a coordinate in the neighbourhood of the actual tip position. Although the inverse controller accomplishes output control, this excites the rigid and elastic modes. A linear stabilizer is designed for final capture of the terminal state and stabilization of the elastic modes. Simulation results are presented to show that in the closed-loop system, large maneuvers can be performed in the presence of payload uncertainty

An Unusual Cause of Paraparesis in a Patient on Chronic Steroid Therapy

Background/Objective: Spinal epidural lipomatosis is the excessive deposition of unencapsulated fat in the epidural space. This is a rare disorder often associated with high levels of endogenous steroids or the administration of exogenous steroids. Case Description: A 32-year-old man with congenital kyphosis treated with prednisolone daily for 5 months for interstitial lung disease developed compressive myelopathy. Findings: Magnetic resonance imaging showed congenital kyphosis along with epidural lipomatosis compressing the cord. Cessation of steroid therapy was associated with improvement in the symptoms. Conclusions: Spinal epidural lipomatosis is a rare side effect of chronic steroid therapy that may occur with relatively short-term, low-dose regimens. In patients with congenital vertebral anomalies, spinal fat deposition may worsen the neurological status in an already compromised cord. Discontinuation of steroid therapy is beneficial; some patients may require surgical intervention for decompression

Akustische Gang-und Laufanalyse für Sport- und Medizinanwendungen

Beeinträchtigungen des menschlichen Gehens können je nach Ausprägung für den Patienten eine erhebliche Beeinträchtigung im täglichen Leben darstellen. Sie können verschiedene Ursachen wie z.B. eine Sportverletzung, Krankheiten wie Diabetes, Sauerstoffunterversorgungen des Gehirns, z.B. nach einem Schlaganfall oder nach einem Badeunfall, oder andere Erkrankungen des Nervensystems haben. Das veränderte Gehen kann im Rahmen von Rehabilitationsmaßnahmen auf dem Laufband mit eingelassener Drucksensormatrix unter visueller Darstellung und Auswertung der plantaren Druckverteilung dargestellt werden. Dies macht jedoch ein persönliches Erscheinen des Patienten beim Arzt oder in der Klinik erforderlich und ist zeitlich beschränkt, da diese diagnostischen Laufbänder nur in wenigen Einrichtungen zu Verfügung stehen. Seit einiger Zeit werden vor allem für Sportler mobile Anwendungen für visuelle Darstellungen des Gangbildes z.B. auf dem Smartphone oder nachträglich auf dem Rechner angeboten (z.B. Systeme von Moticon(c) , Novel(c) oder Sensoria(c)), jedoch sind diese noch recht teuer und zum Teil anfällig gegenüber mechanischen, dauerhaften und sich wiederholenden Belastungen, was oft an der empfindlichen Kabelanbindung der Einlage liegt. Zudem sind sie in ihren Messfrequenzen (bis max. 100 Hz) oder in ihren Auflösungen (max. 8 Sensoren bei 100 Hz) stark eingeschränkt und damit für Laufanalysen mit höheren Schrittfrequenzen nicht geeignet. Im Gegensatz zur visuellen Darstellung erlaubt die Einbeziehung des menschlichen Gehörs auf Grund dessen Empfindlichkeit bei unbewusster Signalwahrnehmung ein schnelleres und intuitiveres Erlernen neuer Bewegungsabfolgen. Dies wurde bereits in Studien zur Optimierung des Bewegungsablaufs bei der deutschen Ruder-Nationalmannschaft, erfolgreich eingesetzt. Dieses akustische Bio-Feedback ist zudem für Patienten von Vorteil, da der enge Zusammenhang zwischen Akustik und Motorik unbewusste Adaptionen des Bewegungsablaufs erleichtert

Acute kidney injury in patients treated with immune checkpoint inhibitors.

Immune checkpoint inhibitor-associated acute kidney injury (ICPi-AKI) has emerged as an important toxicity among patients with cancer. We collected data on 429 patients with ICPi-AKI and 429 control patients who received ICPis contemporaneously but who did not develop ICPi-AKI from 30 sites in 10 countries. Multivariable logistic regression was used to identify predictors of ICPi-AKI and its recovery. A multivariable Cox model was used to estimate the effect of ICPi rechallenge versus no rechallenge on survival following ICPi-AKI. ICPi-AKI occurred at a median of 16 weeks (IQR 8-32) following ICPi initiation. Lower baseline estimated glomerular filtration rate, proton pump inhibitor (PPI) use, and extrarenal immune-related adverse events (irAEs) were each associated with a higher risk of ICPi-AKI. Acute tubulointerstitial nephritis was the most common lesion on kidney biopsy (125/151 biopsied patients [82.7%]). Renal recovery occurred in 276 patients (64.3%) at a median of 7 weeks (IQR 3-10) following ICPi-AKI. Treatment with corticosteroids within 14 days following ICPi-AKI diagnosis was associated with higher odds of renal recovery (adjusted OR 2.64; 95% CI 1.58 to 4.41). Among patients treated with corticosteroids, early initiation of corticosteroids (within 3 days of ICPi-AKI) was associated with a higher odds of renal recovery compared with later initiation (more than 3 days following ICPi-AKI) (adjusted OR 2.09; 95% CI 1.16 to 3.79). Of 121 patients rechallenged, 20 (16.5%) developed recurrent ICPi-AKI. There was no difference in survival among patients rechallenged versus those not rechallenged following ICPi-AKI. Patients who developed ICPi-AKI were more likely to have impaired renal function at baseline, use a PPI, and have extrarenal irAEs. Two-thirds of patients had renal recovery following ICPi-AKI. Treatment with corticosteroids was associated with improved renal recovery