Control of Motion of an Actively Bending Body in Prescribed Channels with Viscous Friction

Mechanics is described and equations are given of motion of an actively bending homogeneous and continuous body of a finite thickness in channels with the viscous friction, using as an example channels in a viscous fluid. Control of motion is suggested, which ensures a maximum speed of the body in a definite channel. Using a sinusoidal channel as an example, the path is described of the repeated maximization of the speed according to the choice of the best parameters of the channel. Control is considered of a wide class other motions of the body.     

Control of Motion of a Body in Formation of a Channel in a Fluid

Mechanics of the formation of a channel by a head of a bending body is considered. Equations are derived of the motion of the body in the channel with its simultaneous formation, which contain the positive feedback. Control is described of various modes of motion and also the transition from one mode to another, including the transition to the motion on account of the feedback. The clarified interrelation of the pressure of the body, its speed, and the responses of the fluid makes it possible to describe the mechanics of the formation and deformation of the channel, which denies the possibility of motion of the body on account of the positive feedback.     

Control of motion of an actively caterpillar-bending body

Equations of kinematics and dynamics of spanworm-bending body are deduced. An integral equation of bending moment distribution that controls the motion of parts of the body by current values of three kinematic parameters is derived. As is shown, the control of motion is conducted according to programs of motor commands that specify values of parameters. Special features of control in different motion problems are described.     

Topological sensitivity derivative and finite topology modifications: application to optimization of plates in bending

The concept of topological sensitivity derivative is introduced and applied to study the problem of optimal design of structures. It is assumed, that virtual topology variation is described by topological parameters. The topological derivative provides the gradients of objective functional and constraints with respect to these parameters. This derivative enables formulation of the conditions of topology transformation. In this paper formulas for the topological sensitivity derivative for bending plates are derived. Next, the topological derivative is used in the optimization process in order to formulate conditions of finite topology modifications and in order to localize positions of the modifications. In the case of plates they are related to introduction of holes and introduction of stiffeners. The theoretical considerations are illustrated by some numerical examples.     

Influence of Reference Conditions on the Analysis of Impact-Induced Elastic Waves

Impact problems involving flexible bodies that undergo largerotations and translations were solved by using the floating frame ofreference approach. Analytically defined modes were selected to describedeformation. Different mode shapes can be used depending on the type ofattachment between the body frames of reference and the flexible bodies.Evaluating the kinematic coefficient of restitution during impactentails using the equivalent rigid body velocities of the flexiblebodies. In general, however, such velocities cannot be identified withreference velocities.When the colliding bodies can undergo large translations, freeattachments allow the use of mode shapes that possess zero totalmomentum. In this case, reference motion coincides with the equivalentrigid body motion of the flexible bodies and is not coupled to elasticmotion. When the colliding solids can rotate freely, the use of modeshapes with a zero angular momentum does not uncouple reference andelastic motion. However, if small deformation occurs during freerotation of the flexible body, the derivative of the reference angleremains roughly constant. Such a derivative can be interpreted as theequivalent angular velocity of the flexible body. When using a rigidattachment between the body frames of reference and the flexible bodies,reference motion does not coincide with the equivalent rigid bodyvelocity of the flexible bodies, which leads to non-constant referencevelocities when the bodies move freely. As a result, the equivalentrigid body velocities must be evaluated as linear combinations ofreference and elastic velocities.     

A Parallel System of the Personification Control System On the Basis of Biology Functions

1 Biology and system science of hu-man bodyLooked from the modern system science viewpoint,the human body is precisely a complex great system.The biology research has already divided into the humanbody many levels, like system(Breath, digestion, bloodcirculation, nerve, uropoiesis, reproduction, movementand so on) tissue( connective tissue, fat tissue, epitheli-um tissue, muscular tissue, the nerve and so on)Cell(Cy-tobiology, cytochemistry, cytophysiology, cytogeneticsand so on)、molecule (M…     

飞艇动力学仿真

刚体假设条件下,飞艇动力学行为的核心问题之一是如何获取气动导数和推进系统螺旋桨的性能参数.针对静导数,采用分块粘结技术和O型网格,生成结构化贴体网格单元,利用SST(Shear Stress Transport)湍流模型进行CFD仿真,动导数采用半经验的方法,附加质量采用边条理论计算.螺旋桨性能参数采用结构化网格与非结构化网格相结合的方法,利用旋转机械CFD软件计算.在此基础上给出了飞艇纵向静稳定性的判别方法,建立飞艇非线性动力学方程和小扰动方程.为验证上述方程,给出了纵向阶跃响应,仿真结果表明该方法是有效的,可用于飞艇后续的飞行控制研究.     

Data‐guided Model Predictive Control Based on Smoothed Contact Dynamics

In this paper, we propose an efficient data‐guided method based on Model Predictive Control (MPC) to synthesize a full‐body motion. Guided by a reference motion, our method repeatedly plans the full‐body motion to produce an optimal control policy for predictive control while sliding the fixed‐span window along the time axis. Based on this policy, the method computes the joint torques of a character at every time step. Together with contact forces and external perturbations if there are any, the joint torques are used to update the state of the character. Without including the contact forces in the control vector, our formulation of the trajectory optimization problem enables automatic adjustment of contact timings and positions for balancing in response to environmental changes and external perturbations. For efficiency, we adopt derivative‐based trajectory optimization on top of state‐of‐the‐art smoothed contact dynamics. Use of derivatives enables our method to run much faster than the existing sampling‐based methods. In order to further accelerate the performance of MPC, we propose efficient numerical differentiation of the system dynamics of a full‐body character based on two schemes: data reuse and data interpolation. The former scheme exploits data dependency to reuse physical quantities of the system dynamics at near‐by time points. The latter scheme allows the use of derivatives at sparse sample points to interpolate those at other time points in the window. We further accelerate evaluation of the system dynamics by exploiting the sparsity of physical quantities such as Jacobian matrix resulting from the tree‐like structure of the articulated body. Through experiments, we show that the proposed method efficiently can synthesize realistic motions such as locomotion, dancing, gymnastic motions, and martial arts at interactive rates using moderate computing resources.     

Efficient simulation of the price and the sensitivities of basket options under time-changed Brownian motions

ABSTRACT

We propose a new variance reduction method for the price and the sensitivities of basket options under time-changed Brownian motion models. The new algorithm combines the pathwise derivative method with control variates, conditional Monte Carlo, and randomized quasi–Monte Carlo. Control variates are constructed by using the conditioning variables of lower bounds of basket options for the purpose of variance reduction. Conditional Monte Carlo further reduces the variance by integrating out the selected conditioning variable. The smoothing effect of conditional Monte Carlo enhances the pathwise derivative and the randomized quasi–Monte Carlo methods. Computational experiments show that the new algorithm yields significant variance reductions.     

自动折弯生产线中逆跟随折弯回正运动模型研究

在简要介绍自动折弯生产线的布局的基础上,分析了自动折弯生产线的工作过程,根据前道折弯的折弯深度和折弯速度,建立折弯辅助机器人的逆跟随折弯回正运动模型,并基于该模型提出了折弯辅助机器人逆跟随折弯回正运动轨迹规划的方法,在折弯辅助机器人跟随折弯完成后,机器人Y、Z、A轴沿着前道折弯跟随的轨迹同时做逆跟随运动,将工件回正到前道折弯时的位置,微调后进行下一道折弯工序,节省了每道工序的加工时间。最后通过实际折弯加工的测试分析,验证了该运动模型的可行性,在保证折弯精度的同时提高了自动折弯生产线的工作效率。     

Self motion determination based on actuator velocity bounds for redundant manipulators

The movement of redundant manipulator joints that does not cause any end-effector motion is referred to as its self motion. Control schemes for redundant manipulators utilize its self motion to optimize a performance criterion. Thus, commanded joint motion at each sampling step is the sum of the minimum joint motion required for the desired end-effector motion and the self motion. However, the amount of self motion is limited by the bounds on actuator velocities, which are limited by the actuator torque bounds. A scheme is presented to determine the magnitude of self motion, the direction of which is determined by a gradient projection scheme. Implementation of this scheme on a Motorola 68020 VMEbus-based controller of a seven-degree-of-freedom manipulator is described.     

基于遗传算法的直线光流刚体运动重建

建立一种新的基于直线光流场从单目图像序列恢复刚体运动和结构的模型,推导出直线光流场与刚体的运动参数之间的关系,用2个二阶线性微分方程表达这种关系,并提出一种求解刚体运动参数的遗传算法,只需要获得图像平面的2条直线光流即可求解刚体的旋转参数,并用合成图像测试了该算法的有效性。     

On conjugation of solutions to two integrable problems: Rolling of pointed body in the plane

In this paper, the problem of motion of heavy rigid body in the rough plane is studied. The surface of body is such that the axis of rotation has two “points,” where the plane tangent to the surface is not specified. The motion is described by two systems of equations; each of them is true for its side of the phase space. One of them is a system of equations that describes rolling of body in the plane without slippage (the body is tangent to the plane by its convex part); the second, is a system of equations that describes motion of body with the fixed point for the Lagrange case (the body is basing on the plane by the point). Questions of existence of global first integrals and potential of the cited one-dimensional system are studied.     

Extended impedance control using real and virtual sensors for redundant manipulators

Control of a redundant manipulator based on an impedance-control framework with multiple simultaneous control sources is described. Each control source provides a different behavior type. An application is decomposed into multiple simultaneous behaviors whose resultant behavior will provide the motion necessary to execute the task. The simultaneous control inputs are merged using impedance control to compute a resultant command to the manipulator. The task space of each behavior can have the dimensionality of the mechanism being controlled. Control of a seven-degree-of-freedom manipulator is described here with an available task space for each behavior of dimensionality seven.     

Inverse Kinematics and Workspace Analysis of a 3 DOF Flexible Parallel Humanoid Neck Robot

To mimic the human neck’s three degree-of-freedom (DOF) rotation motion, we present a novel bio-inspired cable driven parallel robot with a flexible spine. Although there exists many parallel robotic platform that can mimic the human neck motion, most of them have only two DOF, with the yaw motion being actuated separately. The presented flexible parallel humanoid neck robot employs a column compression spring as the main body of cervical vertebra and four cables as neck muscles to connect the base and moving platform. The pitch and roll movements of moving platform are realized by the two dimensional lateral bending motion of the flexible spring, and a bearing located at the top of the compression spring and embedded in the moving platform is used to achieve the yaw motion of the moving platform. By combing the force and torque balance equations with the lateral bending statics of the spring, inverse kinematics and optimizing the cable placements to minimize the actuating cable force are investigated. Moreover, the translational workspace corresponding to pitch and roll movements and rotational workspace corresponding to yaw movement are analyzed with positive cable tension constraint. Extensive simulations were performed and demonstrated the feasibility and effectiveness of the proposed inverse kinematics and workspace analysis of the novel 3 DOF flexible parallel humanoid neck robot.     

Simulation of unsteady compressible flow in a channel with vibrating walls - Influence of the frequency

This study deals with the numerical solution of a 2D unsteady flow of a compressible viscous fluid in a channel for low inlet airflow velocity. The unsteadiness of the flow is caused by a prescribed periodic motion of a part of the channel wall with large amplitudes, nearly closing the channel during oscillations. The channel is a simplified model of the glottal space in the human vocal tract and the flow can represent a model of airflow coming from the trachea, through the glottal region with periodically vibrating vocal folds to the human vocal tract.The flow is described by the system of Navier–Stokes equations for laminar flows. The numerical solution is implemented using the finite volume method (FVM) and the predictor–corrector MacCormack scheme with Jameson artificial viscosity using a grid of quadrilateral cells. Due to the motion of the grid, the basic system of conservation laws is considered in the Arbitrary Lagrangian–Eulerian (ALE) form.The authors present the numerical simulations of flow fields in the channel, acquired from a program developed exclusively for this purpose. The numerical results for unsteady flows in the channel are presented for inlet Mach number M_∞ = 0.012, Reynolds number Re_∞ = 4.5 × 10³ and the wall motion frequency 20 and 100 Hz.     

Evaluation of lumbar motion with fabric strain sensors: A pilot study

Prolonged microgravity has been shown to have a deconditioning effect on the spine, increasing the risk of back issues at distant locations such as Mars. Therefore, studying the lumbar motion of astronauts inside a spacesuit during on ground assessments could be crucial for ensuring crew safety and performance on planetary extravehicular activities. However, spacesuits present many challenges in performing kinematic evaluations with conventional motion capture systems. The purpose of this investigation is to develop a methodology for evaluating lumbar motion that can be worn inside a spacesuit. This method, based on flexible strain sensors, was tested with unsuited subjects in this pilot study. Twelve male volunteer subjects performed unloaded lumbar sagittal flexion and lateral bending motions. Lumbar kinematics were concurrently measured from 3D body scans and flexible strain sensors attached to the subjects. Mean R² values for flexion and lateral bending were 0.93 (±0.06) and 0.96 (±0.03) respectively, and mean estimated 95% error of ±5.3° and ±2.8° were determined for flexion and lateral bending, respectively. The results indicate that flexible strain sensors yield useful metrics for lumbar kinematics.Relevance to industryMeasuring biomechanics of the astronaut inside of a spacesuit is critical to improving spacesuit design and development of prophylactic countermeasures. However, the spacesuit prevents most traditional evaluation techniques. The method developed here provides a wearable solution to measure lumbar motion within the spacesuit and during field assessments in other industries.     

Human body animation: a survey

A survey of human body animation is presented dealing with its geometrical representation, motion control techniques and rendering. A classification of human body animation systems is presented according to different criteria.The human body movement notations are described and the different existing geometric models of the body and the face are analised and compared.The body and face control motion techniques are presented and discussed, as well as human body motion in its environment. Finally, the different problems of human body rendering are presented.     

An autonomous dynamic balance of an electrical bicycle in motion using variable structure under‐actuated control

Based on previous studies, two strategies, the controls of the center of gravity (CG) and the angle of steering handle, are employed to stabilize the bicycle in motion. In general, a pendulum is applied to adjust the CG of the bicycle. An additional factor is the inclination with respect to gravitational direction of the bicycle in motion (i.e., lean angle). As a whole, the system produces three outputs that will affect the dynamic balance of the electric bicycle: the angles of the pendulum, the lean, and the steering. The proposed control method used to generate the handle and pendulum torques is named variable structure under‐actuated control (VSUAC), possessing the number of control inputs smaller than the system output. The purpose of using the VSUAC is the huge uncertainties of a bicycle system, often encountered with irregularities in ground conditions and gusts of wind. Merely using the ordinary proportional‐derivative‐integral (PID) control or other linear control methods usually do not show good robust performance when the aforementioned conditions are present. Finally, the simulations of the electrical bicycle in motion using ordinary PID control, modified proportional‐derivative control (MPDC), and VSUAC are compared to judge the effectiveness and efficiency of the proposed control. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Remarks on the paper “Optimal control of a class of linear multivariable systems with integral quadratic energy constraint ”

An optimal periodic control problem for a system described by differential equations is considered. Control units are assumed to generate control actions with the square-integrable derivative. The above problem is approximated by a sequence of discretized problems containing trigonometric polynomials, which approximate the state and control variables, and the functions in the criterion and differential equations. The conditions for a sequence of optimal solutions to discretized problems, which are to be a generalized minimizing sequence for the basic problem, are given. Extensions to more general problem formulations are presented. The possibility of application is illustrated by the example of an optimal periodic control problem for a chemical reactor.