This paper introduces a method to control the vibration of mobile manipulator on the vertical direction. When the mobile manipulation moves on uneven road, the road disturbance affects the ...manipulation system. It is important to suppress the disturbance for the stability of manipulation system. The vibration damping control method of a simplified double inverted pendulum model is designed to suppress vertical disturbance. In the double inverted pendulum model, the system matrix contains parameter uncertainty due to the simplification of the model. To control this system, we use static output feedback with min-max control. By using the static output feedback with min-max control, the desired closed-loop stability can be achieved while effectively suppressing disturbance even in the presence of system uncertainty. We measure the actual road disturbance by using an accelerometer. In the simulation, we prove the measured ground disturbance is successfully suppressed by using our control method and demonstrated effectiveness of proposed control method through comparative simulations with LQR control.
Open-source designs are being increasingly used to develop robot hardware. When motor actuators were used for robot development in the past, it was difficult to find cost-effective commercial ...products. Open-source motor controllers, recently developed with the collaboration of many people, have exhibited phenomenal growth as their performance is now comparable to those of commercial products and their price is cheaper. In this study, we utilized an open-source Vedder electronic speed controller (VESC), originally developed for electric skateboards, as a general-purpose motor controller for robot control. The high-speed, high-torque, and high-output VESC was hardware-upgraded to enable more accurate current control, and advanced position and speed control algorithms were developed to produce Myongji-VESC (MJ-VESC), a general-purpose motor controller for multiaxis robot systems. To evaluate its current, speed, and position control performances, MJ-VESC was applied to an open-source planetary geared actuator that can be fabricated with a 3D printer. Based on this, we propose an open-source motor controller framework that can be universally used for multiaxis robot systems.
This paper introduces the concept of motion planning of delivery robot in an autonomous driving mode using an inverted pendulum model that can effectively control disturbance. The inverted pendulum ...model exhibits the non-minimum phase characteristic caused by the right half-plane zero. An effective method of reducing this characteristic is examined. A motion platform with 3-degree-of-freedom motion and a touch sensor are installed on a wheeled omnidirectional mobile platform. A steel ball is placed on the touch sensor and controlled to be located at the center. As the autonomous delivery robot moves, the steel ball is subjected to various disturbances and goes off the center. The influence of disturbance can be predicted by measuring the distance the steel ball moves away from the center. In this paper, linear quadratic regulator, preview control, and model predictive control are applied to the inverted pendulum model for motion planning, and thus the reduction of the non-minimum phase characteristic can be comparatively analyzed via simulation. The decrease in the disturbance is experimentally compared according to motion planning. Consequently, this paper proposes an effective motion planning method for an autonomous delivery robot with non-minimum phase characteristic.
Background
Sarcopenia has been underscored as a significant predictor of poor prognosis in cancer patients undergoing immunotherapy with programmed death-1 (PD-1) inhibitors. We aimed to investigate ...the prognostic significance of computed tomography (CT)-determined sarcopenia in patients with microsatellite-stable (MSS) gastric cancer (GC) treated with PD-1 inhibitors.
Methods
We retrospectively assessed patients with MSS GC who had been treated with PD-1 inhibitors from March 2016 to June 2019. Pre-treatment sarcopenic status was determined by analyzing L3 skeletal muscle index with abdominal CT. Progression-free survival (PFS) and overall survival (OS) were estimated using the Kaplan–Meier method, and the differences in survival probability according to sarcopenic status were compared using the log-rank test. Cox proportional hazards regression analyses were performed to identify predictors of PFS and OS.
Results
Of 149 patients with MSS GC (mean age, 57.0 ± 12.3 years; 93 men), 79 (53.0%) had sarcopenia. Patients with sarcopenia had significantly shorter PFS than patients without sarcopenia (median, 1.4 months vs. 2.6 months;
P
= 0.026). Sarcopenia was independently associated with shorter PFS (adjusted hazard ratio HR, 1.79; 95% confidence interval CI, 1.10−2.93;
P
= 0.020). Patients with sarcopenia had shorter OS than patients without sarcopenia (median, 3.6 months vs. 4.9 months;
P
= 0.052), but sarcopenia itself was not a significant prognostic factor for OS (adjusted HR, 1.01; 95% CI, 0.58−1.75;
P
= 0.974).
Conclusions
CT-determined sarcopenia is an independent prognostic factor for PFS in patients with MSS GC treated with PD-1 inhibitors.
Collaborative robots combined with mobile platforms can move freely and have a wide work area. Technological developments in AI and vision have also led to increased research on recognition of ...objects and surroundings using mobile manipulators. However, even though such trends have resulted in growing demand for research on mobile manipulators, their high prices make them difficult to purchase. We solved this problem using 3D printing. A mobile manipulator was manufactured by replacing more expensive reducers with 3D printed planetary gear and cycloid gear reducers. As well, a mecanum in-wheel motor equipped with a 3D printed cycloid reducer was developed to increase the usability of the interior space of the mobile platform. The study employed a task-space control algorithm, which controls the mobile platform and the manipulator simultaneously to ensure effective control of the mobile manipulator. Task-space motion control performance was verified through Gazebo simulation and experiment. Additionally, the repeatability of the task-space position control was measured through experiments and its performance was compared with a commercial manipulator. Finally, we have developed a mobile manipulator that can perform similar levels of work as a commercial robot at one tenth the price of a general commercial mobile manipulator.
The aim of this study was to elucidate the minimal ablative margin for percutaneous radiofrequency ablation (RFA) of hepatocellular carcinoma (HCC) (> 2 and < 5 cm) needed to prevent local tumor ...progression using CT image fusion and a 3D quantitative method.
From April 2005 to March 2007, we performed percutaneous RFA for the treatment of 382 HCCs larger than 2 cm and smaller than 5 cm. A total of 110 tumors in 103 patients (77 men and 26 women; mean age, 59.7 years) that were previously untreated and were monitored for at least 1 year were retrospectively enrolled. A 5-mm safety margin was attempted in all cases, and a CT finding of complete replacement of the index tumor by RFA zone was defined as technical success. We constructed fusion images of CT images obtained before and after RFA and performed radial multiplanar reformation with the rotation axis at the center of the tumor to analyze the ablative margin quantitatively. Risk factors for local tumor progression (the thinnest ablative margin, tumor size, and the effect of hepatic vessels) were assessed by multivariate analysis.
Patients underwent follow-up for 12.9-46.6 months (median, 28.1 months). The tumors were 2.1-4.8 cm (mean +/- SD, 2.7 +/- 0.6 cm) in diameter. The thinnest ablative margins ranged from 0 to 6 mm (1.0 +/- 1.4 mm). A 5-mm safety margin was achieved in only 2.7% (3/110) of cases. In 47.3% (52/110) of cases, vessel-induced indentation of the ablation zone contributed to the thinnest ablative margins. Local tumor progression was detected in 27.3% (30/110) of cases. Concordance between local tumor progression and the thinnest margin was observed in 83.3% (25/30) of cases. The incidence of concordant local tumor progression was 22.7% (25/110), 18.9% (10/53), 5.9% (2/34), and 0% (0/15) in tumors with the thinnest ablative margin of > or = 0, > or = 1, > or = 2, and > or = 3 mm, respectively. An insufficient ablative margin was the sole significant factor associated with local tumor progression.
When the thickness of the ablative margin is evaluated by CT image fusion, a margin of 3 mm or more appears to be associated with a lower rate of local tumor progression after percutaneous RFA of HCC.
Objective
To determine reliable MRI features of autoimmune pancreatitis (AIP) in the proximal pancreas that could allow its differentiation from pancreatic ductal adenocarcinoma (PDAC).
Methods
...Twenty-three patients with AIP and 61 patients with PDAC in the proximal pancreas underwent MRI. Two observers analyzed MRI for lesion morphology, hypointensity degree on T1-weighted images, enhancement pattern during dynamic phases, capsule-like rim, presence of cysts and duct penetrating sign, morphology of bile duct, and icicle appearance and tortuosity of the upstream pancreatic duct. Sensitivity and specificity for the diagnosis of AIP were calculated for each category or combined.
Results
When isointensity on the portal and late phase of MRI and/or the icicle sign of pancreatic duct are applied, 100 % sensitivity for the diagnosis of AIP in the proximal pancreas was achieved. Applying both mild T1 hypointensity similar to the spleen and the icicle sign enabled 100 % specificity for the diagnosis of AIP by differentiating it from PDAC.
Conclusion
The combination of the icicle sign in the upstream pancreatic duct and mild T1 hypointensity or isointensity on portal and late phase of dynamic MRI could be reliable MR features for the diagnosis of AIP in the proximal pancreas by allowing its differentiation from PDAC.
Key Points
•
The icicle sign of the pancreatic duct is useful for diagnosing AIP.
•
Mild T1 hypointensity similar to the spleen is useful for diagnosing AIP.
•
Isointensity on portal and late phases MRI is useful for diagnosing AIP.
To determine if the combination of gadoxetic acid-enhanced magnetic resonance (MR) imaging and diffusion-weighted (DW) imaging helps to increase accuracy and sensitivity in the diagnosis of small ...hepatocellular carcinomas (HCCs) compared with those achieved by using each MR imaging technique alone.
The institutional review board approved this retrospective study and waived the requirement for informed consent. The study included 130 patients (95 men, 35 women) with 179 surgically confirmed small HCCs (≤2.0 cm) and 130 patients with cirrhosis (90 men, 40 women) without HCC who underwent gadoxetic acid-enhanced MR imaging and DW imaging at 3.0 T between May 2009 and July 2010. Three sets of images were analyzed independently by three observers to detect HCC: a gadoxetic acid set (unenhanced, early dynamic, and hepatobiliary phases), a DW imaging set, and a combined set. Data were analyzed by using alternative-free response receiver operating characteristic analysis. Diagnostic accuracy (area under the receiver operating characteristic curve A(z)), sensitivity, specificity, and positive predictive value were calculated.
The mean A(z) values for the combined set (0.952) were significantly higher than those for the gadoxetic acid set (A(z) = 0.902) or the DW imaging set alone (A(z) = 0.871) (P ≤ .008). On a per-lesion basis, observers showed higher sensitivity in their analyses of the combined set (range, 91.1%-93.3% 163-167 of 179) than in those of the gadoxetic acid set (range, 80.5%-82.1% 144-147 of 179) or the DW imaging set alone (range, 77.7%-79.9% 139-143 of 179) (P ≤ .003). Positive predictive values and specificity for all observers were equivalent for the three imaging sets.
The combination of gadoxetic acid-enhanced MR imaging and DW imaging yielded better diagnostic accuracy and sensitivity in the detection of small HCCs than each MR imaging technique alone.
The growth of the robotics industry has led to rising demand for reducers that increase torque efficiently while reducing motor speed. Among them, compound planetary reducers can be effectively used ...in robots because they can achieve high gear ratios with smaller volume. The design of conventional reducers comprises the method of setting a gear ratio to design the gear dimensions and calculating efficiency through dynamic analysis. However, this method suffers from repeated designing and analysis, which makes it very time-consuming. Therefore, this study defines the problem of reducer design as the problem of optimization by setting an objective function, constraints, and boundary conditions, and proposes to obtain the results in a short period of time using the Sequential Least Squares Programming(SLSQP) method. Using the SLSQP method, optimization results can be obtained as real numbers, making it suitable for use in compound planetary friction reducers with no constraints on the selection of gear dimension. For the design problem of the conventional compound planetary gear reducer in which the module value exists, an additional optimal design method considering the module is proposed. To compare the optimal results, we have made a 30:1 compound planetary friction reducer and a 50:1 compound planetary gear reducer using 3D printing. A gear ratio evaluation experiment was conducted to evaluate the performance of the actual manufactured prototype reducers.
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