Joint PD Research Articles

Trajectory optimization and stability control for a novel unmanned intelligent wheel-legged vehicles on unstructured terrains

The trend of intelligent vehicles is currently expanding, and a new class of unmanned intelligent vehicles known as wheel-legged vehicles (WLVs) is emerging. WLVs excel in transportation on unstructured terrain by offering a unique combination of the efficiency of wheels on flat ground and the versatility of legs to tackle obstacles. To enhance the locomotion performance of WLVs on unstructured terrains, this paper presents a novel framework for improving their locomotion through nonlinear programming-based (NLP) trajectory optimization and stability control. The framework optimizes the vehicle’s body and wheel positioning while incorporating terrain information and employs a linear rigid body dynamic model for efficient motion planning. The stability control framework combines feedforward control using ground reaction forces with feedback control through joint PD control and utilizes model predictive control (MPC) to adjust the wheel slip ratio to prevent slip on steep slopes. Experimental validation on the real vehicle with torque-controlled wheels demonstrated the capability of driving over a 1 m height with a 30°slope at an average speed of 0.7 m/s and a maximum speed of 1.03 m/s. Our approach also enables the WLV to overcome obstacles, such as inclines, while dynamically negotiating these challenging terrains.

Loco-Manipulation Control for Arm-Mounted Quadruped Robots: Dynamic and Kinematic Strategies

The studies on quadruped robots equipped with arms are still rare at the moment. The interaction between the arm and the quadrupedal platform needs to be handled by whole-body controllers. This paper presents an optimization-based dynamic whole-body controller to solve the problem of when the robot stands still for manipulation. In order to reduce the strong interaction when the robot is trotting, we keep using the whole-body controller to handle locomotion control and resort to joint PD controllers for the arm’s manipulation coupled with the mobile base on the kinematic level. Simulation results validate the expected locomotion and manipulation functionalities in both manipulation mode and loco-manipulation mode. The proposed control strategies are able to use the redundancy to perform multiple tasks in a dynamic system as such with 24 degrees of freedom.

The nature of modifying effect of gallium on Pd-Ga/Al2O3 catalyst for liquid-phase selective acetylene hydrogenation

The structural properties of Pd-Ga/γ-Al2O3 samples prepared from joint Pd(NO3)2 and Ga(NO3)3 solution and their catalytic properties in liquid-phase acetylene hydrogenation have been studied. Using temperature programmed reduction (TPR-H2), transmission electron microscopy (TEM), diffuse reflectance infrared Fourier transform spectroscopy of adsorbed CO (CO-DRIFTS) and X-ray photoelectron spectroscopy (XPS) it was found that an increase in the ethylene selectivity to ∼ 66–70% is explained by the modification of the electronic properties of palladium by gallium at a Ga:Pd molar ratio of 0.5 and by the formation of bimetallic Pd2Ga particles in the case of Ga:Pd = 2.

Systemic Vascular Basement Membrane Markers Linked to Synovial Vascular Remodeling Are Bio-Markers of Hemarthrosis in Patients with Hemophilia

Introduction: Acute painful joint episodes in hemophilia are not always associated with hemarthrosis. Point-of-Care Musculoskeletal Ultrasound with Power Doppler (POC MSKUS/PD) is a fast and sensitive imaging modality to determine the presence of hemarthrosis and direct management. Systemic collagen cleavage products reflecting extracellular matrix, bone and soft tissue turnover may serve as an alternative tool for the detection of hemarthrosis. Based on previous observations of pronounced vascular remodeling within the synovial tissue during hemarthrosis in patients and hemophilic mouse models, we hypothesized that cleavage products of collagen IV, found in the basement membrane of blood vessels may differentiate between bleeding and non-bleeding states.Methods: Joint bleeding was induced in FVIII-/- mice (+/- FVIII-treatment before and shortly after injury). Synovial vascular remodeling was assessed 14 days later by MSKUS/PD and histology including αSmooth Muscle Actin (αSMA)-staining. Murine plasma samples were analyzed for C4M2 and P4NP-7S, which are type IV collagen turnover products. To determine human relevance, 31 adult patients with hemophilia (PWH), ≥ age 21, were studied prospectively for 3 years with MSKUS/PD during pain-free intervals and painful events for bleed status, vascular flow and 11 plasma markers of collagen turnover(C2M, ARGS, C3M, Pro-C3, C5M, Pro C5, C4M2, P4NP-7S, Col18N, DCN- CS, ColNeo10, NIC).Results: Type IV collagen turn-over markers were significantly elevated in plasma of FVIII-/- deficient mice 14 days after joint bleeding when compared to baseline (C4M2: 2.575 ng/mL vs. 1.94 ng/mL, p=0.029 and P4NP-7S: 80.3 ng/mL vs. 67.81 ng/mL, p= 0.0152 respectively ). This increase coincided with a significant increase in vessel number (2.3 fold, p=0.0008), vascular flow by PD (2.3 fold, p= 0.014) and αSMA staining (5.1 fold, p= 0.0007). C4M2 and P4NP7S plasma levels correlated negatively with αSMA staining, suggesting a role for αSMA in vessel stabilization (C4M2 p=0.02, Pearson r= -0.5707; P4NP-7S p= 0.0130, Pearson r= -0.6238). FVIII-treatment reduced plasma C4M2 and P4NP-7S levels to baseline (C4M2 1.98 ng/mL vs. 1.94 ng/mL, P4NP-7S 59.98 ng/mL vs. 67.81 ng/mL), but had no effect on the other vascular parameters. In patients, results from 91 visits were compiled. Twenty five were due to acute painful episodes with 16 confirmed hemarthroses. Of the 11 biomarkers evaluated, only C4M2 and P4NP-7S were transiently but significantly elevated in plasma during joint bleeding compared to pain free intervals or to non-bleeding painful episodes. Plasma C4M2 levels during acute painful bleeding episodes when compared to non-bleeding states were 41.65 vs. 29.69 ng/mL (p=0.0003), and P4NP-7S levels were 418.9 vs 278.1 ng/mL (p=0.0007), respectively. Baseline levels of C4M2 and P4NP-7S in PWH were above the lab reported normal range, indicating ongoing high vascular basement membrane turnover. Additionally, PWH who developed joint bleeding episodes had a higher level of collagen IV biomarkers at baseline when compared to PWH who did not experience joint bleeding (C4M2 33.91 vs 29.07 ng/mL, P4NP7s 320.6 vs 292.8 ng/mL), although this was not statistically significant. Hemarthrosis was accompanied by pronounced abnormal synovial microvascular flow evidenced by PD, while plasma levels of both biomarkers correlated positively with joint PD signal (C4M2, p= 0.0400, Pearson r=0.4409; P4NP7S-p=0.0141, Pearson r=0.5154).Conclusions: Our findings suggest that systemic vascular collagen turn-over products may be novel biomarker candidates to identify patients at high risk for joint bleeding and to diagnose acute hemarthrosis. Hemarthrosis in hemophilia is associated with pronounced synovial vascular remodeling. Cleavage products of type IV collagen, but not of any other collagen, were systemically elevated in PWH and distinguished bleeding from non-bleeding painful episodes. Type IV collagen is found exclusively in basement membranes and in the case of joint bleeding, the presumed source of these turnover markers is newly formed synovial blood vessels. Therefore, our findings support the concept that vascular instability during neovascularization is involved in the dynamics of hemophilic joint bleeding. These findings broaden the scope of potential diagnostic tools substantially, opening new avenues for personalized treatment of PWH. Disclosuresvon Drygalski:Bioverativ/Sanofi: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Novo Nordisk: Consultancy, Honoraria; HemaBiologics: Consultancy; Genentech: Consultancy; Biomarin: Consultancy, Honoraria; Uniqure: Consultancy, Honoraria; Shire: Consultancy, Honoraria; Hematherix: Membership on an entity's Board of Directors or advisory committees, Patents & Royalties.

Cross-Coupled Contouring Control of Multi-DOF Robotic Manipulator

Reduction of contour error is a very important issue for high precise contour tracking applications, and many control systems were proposed to deal with contour tracking problems for two/three axial translational motion systems. However, there is no research on cross-coupled contour tracking control for serial multi-DOF robot manipulators. In this paper, the contouring control of multi-DOF serial manipulators is developed for the first time and a new cross-coupled PD (CC-PD) control law is proposed, based on contour errors of the end-effector and tracking errors of the joints. It is a combination of PD control for trajectory tracking at joint level and PD control for contour tracking at the end-effector level. The contour error of the end-effector is transformed to the equivalent tracking errors of the joints using the Jacobian regulation, and the CC-PD control law is implemented in the joint level. Stability analysis of the proposed CC-PD control system is conducted using the Lyapunov method, followed by some simulation studies for linear and nonlinear contour tracking to verify the effectiveness of the proposed CC-PD control system.

1P2-B03 ヒューマノイドロボットの重心インピーダンス行列

This paper proposes a novel concept called COG impedance matrix of a humanoid robot, which provides an explicit relationship with the joint impedance or joint PD controller. Using the COG impedance matrix, we can calculate the macroscopic feedback gain which approximates the joint impedance, and compute the maximal output admissible (MOA) set for falling detection. First-lag-order COP dynamics is also proposed to compensate the nonlinearity in the whole body dynamics.

Effect of preparation conditions on the formation of the active phase of carbon fiber catalytic systems for the low-temperature oxidation of carbon monoxide

We studied the effects of the composition of impregnating solution and heat treatment conditions on the activity of catalytic systems for the low-temperature oxidation of CO obtained by the impregnation of Busofit carbon-fiber cloth with aqueous solutions of palladium, copper, and iron salts. The formation of an active phase in the synthesized catalysts at different stages of their preparation was examined with the use of differential thermal and thermogravimetric analyses, X-ray diffraction analysis, X-ray photoelectron spectroscopy, and elemental spectral analysis. The catalytic system prepared by the impregnation of electrochemically treated Busofit with the solutions of PdCl2, FeCl3, CuBr2, and Cu(NO3)2 and activated under optimum conditions ensured 100% CO conversion under a respiratory regime at both low (0.03%) and high (0.5%) carbon monoxide contents of air. It was found that the activation of a catalytic system at elevated temperatures (170–180°C) leads to the conversion of Pd(II) into Pd(I), which was predominantly localized in a near-surface layer. The promoting action of copper nitrate consists in the formation of a crystalline phase of the rhombic atacamite Cu2Cl(OH)3. The catalyst surface is finally formed under the conditions of a catalytic reaction, when a joint Pd(I)-Cu(I) active site is formed.

A1.13 Ultrasound-guided assessement of axillary lymph nodes in rheumatoid arthritis: cross-sectional and prospective clinico-pathologic significance

Background and ObjectivesJoint-draining lymph nodes (LN) and afferent lymphatics are relevant components of the induction-resolution phases of immune responses, acting through the control of cell efflux from the joint and...

3R Plane Robot Impedance Control Based on Fuzzy PD Controller

The impedance control problem of three-link plane robot is investigated. Firstly, the kinematics and dynamics model of robot is derived. Second, the impedance control model is established. Then, the fuzzy PD joint controller is formatted when the fuzzy theory is introduced into the joint PD controller of robot. The combination of controller and the impedance model is taken into the control of position and contact force of robot by taking into account the environmental constraints. Finally, higher control accuracy of fuzzy PD impedance control than traditional algorithms is proved by the simulation of PDimpedance control and fuzzy PD impedance control.

Low-complexity linear parameter-varying modeling and control of a robotic manipulator

In this paper, a practical procedure for linear parameter-varying (LPV) modeling and identification of a robotic manipulator is presented, which leads to a successful experimental implementation of an LPV gain-scheduled controller. A nonlinear dynamic model of a two-degrees-of-freedom manipulator containing all important terms is obtained and unknown parameters which are required to construct an LPV model are identified. An important tool for obtaining a model of complexity low enough to be suitable for controller synthesis is the principle-component-analysis-based technique of parameter set mapping. Since the resulting quasi-LPV model has a large number of affine scheduling parameters and a large overbounding, parameter set mapping is used to reduce conservatism and complexity in controller design by finding tighter parameter regions with fewer scheduling parameters. A sufficient a posteriori condition is derived to assess the stability of the resulting closed-loop system. To evaluate the applicability and efficiency of the approximated model, a polytopic LPV gain-scheduled controller is synthesized and implemented experimentally on an industrial robot for a trajectory tracking task. The experimental results illustrate that the designed LPV controller outperforms an independent joint PD controller in terms of tracking performance and achieves a slightly better accuracy than a model-based inverse dynamics controller, while having a simpler structure. Moreover, it is shown that the LPV controller is more robust against dynamic parameter uncertainty.

Construction of a Gait Adaptation Model in Human Split-Belt Treadmill Walking Using a Two-Dimensional Biped Robot

A number of studies have measured kinematics, dynamics and oxygen uptake while a person walks on a treadmill. In particular, during walking on a split-belt treadmill, in which the left and right belts have different speeds, remarkable differences in kinematics are observed between normal subjects and subjects with cerebellar disease. In order to construct a gait adaptation model of such human split-belt treadmill walking, we proposed a simple control model and developed a new two-dimensional biped robot walk on a split-belt treadmill. We combined the conventional limit-cycle-based control consisting of joint PD control, cyclic motion trajectory planning and a stepping reflex with a newly proposed adjustment of P-gain at the hip joint of the stance leg. The data obtained in experiments on the robot (normal subject model and cerebellum disease subject model) have highly similar ratios and patterns to data obtained in experiments on normal subjects and subjects with cerebellar disease carried out by Bastian et al. We also showed that the P-gain at the hip joint of the stance leg was the control parameter of adaptation for symmetric gaits in split-belt walking and that P-gain adjustment corresponded to muscle stiffness adjustment by the cerebellum. Consequently, we successfully proposed a gait adaptation model for human split-belt treadmill walking, and confirmed the validity of our hypotheses and the proposed model using the biped robot.

A Fuzzy Lyapunov-Based Control Strategy for a Macro–Micro Manipulator: Experimental Results

A class of model-free fuzzy controllers based on the Lyapunov-function reasoning is presented for a Macro-Micro Manipulator (M3) system. The control strategy uses the structural properties of the system model and assumes no other a priori knowledge about the system dynamics. Although, in general, the control structure can be regarded as a fuzzy controller, it may also be interpreted as a nonlinear multi-input multi-output (MIMO) proportional-integral-differential (PID) controller. An experimental setup consisting of a three-link M3 is considered as a practical case study. The test-bed is a nonlinear nonminimum phase MIMO system with a complex model and considerable joint frictions. Experimental results are presented to illustrate the improved performance of the proposed control strategy over a joint PD controller

Tracking control of a flexible-link manipulator using neural networks: experimental results

In this paper, the problem of tip position tracking control of a flexible-link manipulator is considered. Two neural network schemes are presented. In the first scheme, the controller is composed of a stabilizing joint PD controller and a neural network tracking controller. The objective is to simultaneously achieve hub-position tracking and control of the elastic deflections at the tip. In the second scheme, tracking control of a point along the arm is considered to avoid difficulties associated with the output feedback control of a non-minimum phase flexible manipulator. A separate neural network is employed for determining an appropriate output to be used for feedback. The controller is also composed of a neural network tracking controller and a stabilizing joint PD controller. Experimental results on a single-link flexible manipulator show that the proposed networks result in significant improvements in the system response with an increase in controller dynamic range despite changes in the desired trajectory.

Adaptive robust controller design for multi-link flexible robots

Energy-based robust control strategy was proposed in [12] to improve the control performance of the traditional joint PD control by introducing additional control efforts through the evaluation of vibration related variables. Although the energy-based robust controller always guarantees closed-loop stability, it is not easy to find suitable gains of the terms for a satisfactory control performance. In this paper, adaptive energy-based robust control is presented for both closed-loop stability and automatic tuning of the gains of the additional control terms for desired performance. Simulation results are provided to show the effectiveness of the presented approach.

An inverse kinematics algorithm for interaction control of a flexible arm with a compliant surface

This paper deals with the problem of controlling the interaction of a multilink flexible arm in contact with a compliant surface. For a given tip position and surface stiffness, the joint and deflection variables are computed using a closed-loop inverse kinematics algorithm. This is based on a suitable Jacobian matrix which includes terms accounting for the static deflections due to gravity and contact force. The computed variables are used as the set-points for a simple joint PD control, thus achieving regulation of the tip position and contact force via a joint-space controller. The scheme is tested in a simulation case study for a planar two-link manipulator.

Constrained Joint PD+ Controller for Flexible Link Robots

A class of globally asymptotically stable regulators for a finite-dimensional model of robot arm with flexible links under gravity is presented.The control law is formed as the sum of static compensation of gravity at the desired position and constrained state feedback. Only some of generalized coordinates (joint positionsand velocities) are assumed available for measurement and saturation in amplifier characteristic curvesis taken into account.

Neural network based dynamic modeling of flexible-link manipulators with application to the SSRMS

This paper presents an approach for dynamic modeling of flexible-link manipulators using artificial neural networks. A state-space representation is considered for a neural identifier. A recurrent network configuration is obtained by a combination of feedforward network architectures with dynamical elements in the form of stable filters. To guarantee the boundedness of the states, a joint PD control is introduced in the system. The method can be considered both as an online identifier that can be used as a basis for designing neural network controllers as well as an offline learning scheme to compute deflections due to link flexibility for evaluating forward dynamics. Unlike many other methods, the proposed approach does not assume knowledge of the nonlinearities of the system nor that the nonlinear system is linear in parameters. The performance of the proposed neural identifier is evaluated by identifying the dynamics of different flexible-link manipulators. To demonstrate the effectiveness of the algorithm, simulation results for a single-link manipulator, a two-link planar manipulator, and the Space Station Remote Manipulator System (SSRMS) are presented. ©2000 John Wiley & Sons, Inc.

CONTROL OF SLEW MANEUVER OF A FLEXIBLE BEAM MOUNTED NON-RADIALLY ON A RIGID HUB: A GEOMETRICALLY EXACT MODELLING APPROACH

The positioning control using a joint torque is studied for a hub–beam system with a tip payload. In order to make the axial vibration of the beam accessible to the joint torque, the flexible beam mounted non-radially on the rigid hub is considered. Neither model truncation nor small deflection assumption is employed throughout the process of dynamic modelling and controller design. A joint PD controller with additional feedback of joint acceleration and root strain of the beam is derived using a Lyapunov-type method. Global asymptotic stability of the desired equilibrium position is proved rigorously. The geometrically exact formulation presented in this work can be viewed as a generalization of the related work based on the small deflection assumption investigated in the existing literature.

On the Stability of PD Control for a Two-Link Rigid-Flexible Manipulator

Controller design for a rigid-flexible two-link manipulator is considered. Robustness of independent joint PD control is investigated. It has been shown that the stability of independent joint PD control does not depend explicitly on the system parameters. No discretization or linearization of the equations of motion is required to assure the stability. Simulation studies also show that independent joint PD control gives reasonably good results for the flexible system, and is robust to parameter uncertainties.

Adaptive generalized model-based control of robot manipulators

An adaptive model-based control approach to the trajectory tracking of robot manipulators is proposed, which incorporates both the full-order actuator dynamics and the second-order manipulator dynamics in controller design. Flexibility of design and trade-off between tracking precision and control law complexity are provided: depending on the complexity of the manipulator and of the application, the manipulator dynamics can be ignored as a disturbance, or compensated either offline or online. The proposed controllers include, as special cases, the independent joint PD control, feedforward control and computed-torque control laws derived from the manipulator model-based control approach. Simulation results are presented for the first three joints of the PUMA 560 arm, illustrating the effectiveness of the proposed controllers.