Modeling the Influences of Cyclic Top-Down and Bottom-Up Processes for Reinforcement Learning in Eye Movements

Understanding and reproducing complex human oculomotor behaviors using computational models is a challenging task. In this paper, two studies are presented, which focus on the development and evaluation of a computational model to show the influences of cyclic top-down and bottom-up processes on eye movements. To explain these processes, reinforcement learning was used to control eye movements. The first study showed that, in a picture-viewing task, different policies obtained from different picture-viewing conditions produced different types of eye movement patterns. In another visual search task, the second study illustrated that feedback information from each saccadic eye movement could be used to update the model's eye movement policy, generating different patterns in the following saccade. These two studies demonstrate the value of an integrated reinforcement learning model in explaining both top-down and bottom-up processes of eye movements within one computational model.     

Movements with Lateral Constraint

Abstract

The literature on terminal control tasks and continuous tracking tasks suggests a possible model for tasks where the subject must guide a vehicle at his own speed along a course defined by a tolerance band. The model predicts a linear relationship between the average velocity and the width of the tolerance band. Throe experiments are described which simulate vehicle guidance by pencil-and-paper experiments for courses consisting of straight lines and circles. The predictions of the model were confirmed, suggesting that a general measure for the ease of control of a vehicle (or other controlled system) is possible using this technique.     

Estimation of Human Movements via Quaternion

This paper presents the authors＇ research results about HRI （human-robot interaction）. The goal is to estimate together the arm position, the anatomical movements of the shoulder and accelerations of the arm with respect to the shoulder and visualizing this movement in a 3-D virtual model to control a Robot. The estimation algorithm makes use of a nonlinear observer and an optimization routine to fuse information from the sensor. The global asymptotic convergence of the nonlinear observer is guaranteed. Extensive tests of the presented methodology with real world data show the effectiveness of the proposed procedure.     

Geometry and Control of Human Eye Movements

In this paper, we study the human oculomotor system as a simple mechanical control system. It is a well known physiological fact that all eye movements obey Listing's law, which states that eye orientations form a subset consisting of rotation matrices for which the axes are orthogonal to the normal gaze direction. First, we discuss the geometry of this restricted configuration space (referred to as the Listing space). Then we formulate the system as a simple mechanical control system with a holonomic constraint. We propose a realistic model with musculotendon complexes and address the question of controlling the gaze. As an example, an optimal energy control problem is formulated and numerically solved     

跳水动作的视频合成与比较

如何利用计算机视频处理技术,提高体育运动员的科学训练水平,是当前信息处理技术和体育科学技术交叉研究领域的重点问题之一。借助多段运动视频的合成,对各种动作进行观察比较,找出运动员在同一动作上的差异,对于诸如跳水等多项运动而言具有重要的意义。文章根据跳水视频的特点,提出了一种基于运动目标的视频合成算法。通过对不同的方法进行比较实验,结果表明:所提出的算法能很好地完成视频比较,对背景变化具有较强的鲁棒性。另外,算法还可以扩展到多个运动目标比较等应用领域。     

头部动作识别系统的硬件设计

介绍了一种用于残疾人的智能交互系统——头部动作识别系统的主体硬件框架,包括头部运动测量单元的设计,采用了三轴陀螺仪L3G4200D和三轴加速度传感器ADXL345.机械臂的执行器驱动单元设计,该部分采用MOSFET驱动,有电流反馈.机械臂结构设计,该部分采用线性执行器电动推杆,推力1500N,速度在2mm/s至60mm/s之间可控,行程200mm,机械臂底盘支持360度全向旋转,整体水平作用距离达1.2m,垂直作用距离1.0m,腕关节支持360度旋转,夹持机构开合行程30mm,可以应对一般家庭应用.为机械臂控制算法的工作提供了硬件平台.     

Neural Control of the Movements of a Wheelchair

This paper studies the problem of controlling the movements of a handicapped person's motorized wheelchair from a practical point of view. The control system implemented has been divided into two levels: the low level, consisting of an electronic system which directly controls the drivers of the chair's motors, with a classic PID (proportional-integral-derivative) control loop. The aim of this level is to ensure that the speeds of each one of the wheels is similar to the input speed of these control boards. The second control level (high level), implemented by means of neural techniques, ensures that the linear and angular speeds of the wheelchair are those indicated by a trajectory generator. A new recurrent model is used as the neural network, for which the stability conditions of the complete control system are obtained and various practical tests are carried out, which show the correct performance of the actual system implemented.     

基于六自由度运动测量的下颌运动虚拟再现

为了真实再现下颌的运动过程,设计了一种记录下颌骨六自由度位移的方法;该方法使用两个重叠的网格屏和两束成一定夹角的激光束,用一个CCD视频摄像机采集测量图像,通过简单的计算得到下颌骨的位置与姿态的变化过程;结合上、下牙列的三维扫描数据,可以三维图形的形式再现咬合运动;实验结果表明该文介绍的方法计算公式简单,实时性强,连续测量无误差积累,测量精度可满足口腔医学要求,可用于下颌运动过程的记录。     

一种人眼运动及表情仿真方法

真实感人脸动画是计算机图形学领域的一个研究热点,为了更逼真的仿真虚拟人眼部的表情动作,提出了一种基于机构学原理与肌肉模型的人眼运动及表情仿真方法。可将人眼眼皮的三维网格模型分为边界点和非边界点分别控制,对于边界点的运动采用机构模型实现,对于非边界点及眼部其余部分采用肌肉模型控制,仿真出不同的人眼运动及表情。同时给出了仿真运动的效果实例。采用上述方法可以得到逼真的人眼表情动作仿真动画,效果良好。     

复杂运动情况下的多目标检测与追踪

针对多运动目标视频序列中目标存在过缓运动且相互间遮挡的问题,提出一种改进的混合高斯模型(Gaussian Mixture Model,GMM)进行目标检测并结合卡尔曼滤波进行跟踪的新算法;在运动背景检测中,采用三帧差法和混合高斯模型的融合算法进行目标提取,解决了过缓运动目标检测区域不完整的问题;在运动目标跟踪中,由于Kalman滤波器采用目标检测结果进行预测,对观测噪声矩阵进行自适应更新,使得跟踪的稳定性得到加强;通过对比,验证了新算法对存在过缓以及遮挡的不规律运动情况的多目标检测识别与跟踪的实时有效性与准确性。     

Biomimetic Pinching Movements of a Musculo-Skeletal Dual-Finger Model

The present paper investigates pinching movements using an index finger and a thumb actuated by redundant nonlinear digitorum muscles mimicking the configuration of human fingers. A dual-finger model with 2-d.o.f. joints for each finger and redundant nonlinear digitorum muscles is formulated to mimic the structure of human fingers. First, the kinematics and dynamics of the overall finger–object system, as well as the nonlinear muscular dynamics, are derived in accordance with the results of physiological studies. Next, a sensory-motor control law is proposed to enable stable pinching simultaneously with orientation regulation of an object. This control law includes an internal force term generated by co-construction of the redundant muscles. It is shown that the internal force term can modulate the damping factor in the joint space by its nonlinearity. Based on this effect, it is then shown by numerical simulation that our sensory-motor control law with co-contraction of each digitorum muscle makes it possible to realize pinching movements. Therefore, the pinching movements may be realized by means of a musculo-skeletal dual-finger system with the sensory-motor control law and co-contraction of redundant digitorum muscles.     

A Model of Linear Arm Movements with Preview Constraints

This study extends Fitts's law for linear and serial arm movements to incorporate constraints on the preview (distance) for each movement. A simple first-order linear model relating mean movement time to Fitts's index of difficulty (ID) variable and a preview-constraint ID variable was found to explain 92% of the variation in movement time. The results, which were based on a sample of 12Ss, showed that the preview-constraint variable contributed more to the movement time than did Fitts's ID variable. The information rate generated was 6·2 bits/sec, which was about half that produced by similar tasks involving no preview constraints and about 60% higher than that produced by rotary arm movements with preview constraints.

The relatively large error rates generated were predominantly overshoot errors. The highest error rates occurred for the more difficult tasks as reflected by large ID values. Both movement times, error rates and parameter estimates showed large variations between individual Ss. The mean movement times across Ss were considerably higher than predetermined motion-time systems predictions.     

Error Analysis of Camera Movements in Stereo Vehicle Tracking Systems

In an outdoor navigational environment, cameras of an autonomous vehicle or robot are subjected to uncontrollable movements relative to the vehicle or robot body. In this paper, the effect of such camera movements in stereo vision-based vehicle tracking systems is analyzed. In other words, it is shown how the computation of the range and heading angle of a lead vehicle is affected as a result of camera movements. The parameter space of the stereo system is divided into a controllable subspace consisting of the baseline and an uncontrollable subspace consisting of relative camera movements and the coordinates of a tracked point on the lead vehicle. The optimal baseline value with respect to the uncontrollable subspace is found by employing the mini-max and minimum mean-squared error estimators. The mini-max estimator is used to obtain the worst case performance while the minimum mean-squared estimator is used to obtain the average performance. Based on this analysis, it is shown how an optimal imaging geometry for a stereo vision-based vehicle tracking system can be designed in order to have the least amount of range and heading angle errors.     

Insights from Dividing 3D Goal-Directed Movements into Meaningful Phases

Existing measures for evaluating user performance on interaction tasks in virtual environments don't often provide sufficient information for improving these interactions. A new method for analyzing 3D goal-directed movements divides them into meaningful phases. The authors applied this method to experimental data collected for a 3D task resembling a standardized 2D multidirectional pointing task (ISO 9241-9). The results and analysis demonstrate that the method provides a more detailed insight into 3D goal-directed movements. This analysis can help researchers better identify input devices' and interaction techniques' strengths and weaknesses. This article is part of a special issue on 3D user interfaces.     

Head Movements for Depth Perception: Praying Mantis versus Pigeon

Inspired by the abilities of both the praying mantis and the pigeon to judge distance by use of motion-based visually mediated odometry, we create miniature models for depth estimation that are similar to the head movements of these animals. We develop mathematical models of the praying mantis and pigeon visual behavior and describe our implementations and experimental environment. We investigate structure from motion problems when images are taken from a camera whose focal point is translating according to each of the biological models. This motion in the first case is reminiscent of a praying mantis peering its head left and right, apparently to obtain depth perception, hence the moniker mantis head camera. In the second case this motion is reminiscent of a pigeon bobbing its head back and forth, also apparently to obtain depth perception, hence the moniker pigeon head camera. We present the performance of the mantis head camera and pigeon head camera models and provide experimental results and error analysis of the algorithms. We provide the comparison of the definitiveness of the results obtained by both models. The precision of our mathematical model and its implementation is consistent with the experimental facts obtained from various biological experiments.     

Estimation of Alonso's Theory of Movements by Means of Instrumental Variables

Alonso's Theory of Movements is a widely applicable Spatial Interaction Model, describing an equilibrium of inflows and outflows. Based on a survey of estimation attempts in the past, we conclude that econometric estimation of the so-called systemic parameters is somewhat problematic. In this paper we describe a new estimation method, using instrumental variables which are derived from the model. The distance deterrence parameter and the unobserved balancing factors can be estimated first, with known methods. The remaining parameters can be estimated in an iterative regression procedure, using instruments for the balancing factors. These instruments are derived as the predicted values of the balancing factors, based on the last obtained parameter estimates.     

轮-叶复合式推进装置运动仿真分析

研究水陆两用车辆的推进装置推动力的有效性设计,可通过模仿双嵴冠蜥在水上行走时腿部的运动姿态,设计了一种新型轮-叶复合式推进装置。为获得推进装置在一个运动周期内的推进力、升力和流场变化情况,采用VOF模型和动网格方法对在不同浸水深度、夹角条件下的水动力性能进行动力学仿真。结果表明,装置能够提供有效的推进力和升力,在零浸水深度处推进力和升力均可得最大值;改变叶片夹角时,推进力和升力有较大变化,且在一个周期内,推进装置产生的推进力和升力呈现交替性波动。