yoyo运动的实时轨迹生成

基于NTG（Nonlinear Trajectory Generation）软件包提出了一种机器人yoyo运动实时最优轨迹生成的通用方法,即数值解法,该方法也可以应用于其他类似周期性动态系统的轨迹规划问题。对于这类系统的实时最优控制来说,一个最为关键的问题就是如何实现快速求解最优轨迹,以满足实时性要求。而传统的数值求解方法都很费时。通过把最优问题映射一个较低维的空间进行求解,并且利用多线程编程技术,大大减少了计算所用的时间。仿真结果显示所求得的数值解与解析解完全相同,这也验证了该方法的正确性。单循环yoyo仿真的计算时间为10 ms左右,这表明该方法完全可以应用于实时控制。     

FIR filter-based online jerk-constrained trajectory generation

In the context of human–robot manipulation interaction for service or industrial robotics, the robot controller must be able to quickly react to unpredictable events in dynamic environments. In this paper, a FIR filter-based trajectory generation methodology is presented, combining the simplicity of the analytic second-order trajectory generation, i.e. acceleration-limited trajectory, with the flexibility and computational efficiency of FIR filtering, to generate on the fly smooth jerk-constrained trajectories. The proposed methodology can generate synchronized (fixed-time) and time-optimal jerk-limited trajectories from arbitrary initial velocity and acceleration conditions within $20$ microsecond. Other jerk-constrained trajectories such as jerk-time fixed trajectories, which are particularly suitable for vibration reduction, can be easily generated. Experimental validations carried out on a seven axis Kuka LBR iiwa are presented.     

On trajectory generation for flexible robots

A trajectory based on a Gaussian velocity profile is presented as an alternative to the double square pulse acceleration profile. The new trajectory leads to the fast positioning of the tip of a flexible robot with a minimal excitation of high-frequency modes. The torques necessary to move the robot according to this trajectory show a very smooth behavior. The absence of high-frequency content, present when double square pulse accelerations are considered, eliminates the Occurrence of undesired residual vibrations produced by modeling uncemnties at high frequencies. The excellent results obtained suggest the use of this new trajectory for fast and precise positioning of flexible robots.     

An effective trajectory generation method for bipedal walking

This paper presents the virtual height inverted pendulum mode (VHIPM), which is a simple and effective trajectory generation method for the stable walking of biped robots. VHIPM, which is based on the inverted pendulum mode (IPM), can significantly reduce the zero moment point (ZMP) error by adjusting the height in the inverted pendulum. We show the relationship between VHIPM and other popular trajectory generation methods, and compare the ZMP errors in walking when trajectories are generated by various methods including VHIPM. We also investigate the sensitivity of the ZMP error in VHIPM to the step length, walking period and mass distribution of a robot. The simulation results show that VHIPM significantly reduces the ZMP errors compared to other methods under various circumstances.     

基于注意力机制的行人轨迹预测生成模型

针对长短期记忆网络（LSTM）在行人轨迹预测问题中孤立考虑单个行人,且无法进行多种可能性预测的问题,提出基于注意力机制的行人轨迹预测生成模型（AttenGAN）,来对行人交互模式进行建模和概率性地对多种合理可能性进行预测。AttenGAN包括一个生成器和一个判别器,生成器根据行人过去的轨迹概率性地对未来进行多种可能性预测,判别器用来判断一个轨迹是真实的还是由生成器伪造生成的,进而促进生成器生成符合社会规范的预测轨迹。生成器由一个编码器和一个解码器组成,在每一个时刻,编码器的LSTM综合注意力机制给出的其他行人的状态,将当前行人个体的信息编码为隐含状态。预测时,首先用编码器LSTM的隐含状态和一个高斯噪声连接来对解码器LSTM的隐含状态初始化,解码器LSTM将其解码为对未来的轨迹预测。在ETH和UCY数据集上的实验结果表明,AttenGAN模型不仅能够给出符合社会规范的多种合理的轨迹预测,并且在预测精度上相比传统的线性模型（Linear）、LSTM模型、社会长短期记忆网络模型（S-LSTM）和社会对抗网络（S-GAN）模型有所提高,尤其在行人交互密集的场景下具有较高的精度性能。对生成器多次采样得到的预测轨迹的可视化结果表明,所提模型具有综合行人交互模式,对未来进行联合性、多种可能性预测的能力。     

Optimal trajectory generation algorithm for serial and parallel manipulators

In this paper, an Optimal Trajectory Generation Algorithm (OTGA) is developed for generating minimum-time smooth motion trajectories for serial and parallel manipulators. OTGA is divided into two phases. The first phase encompasses derivation of minimum-time optimal trajectory using cubic spline due to its less vibration and overshoot characteristics. Although cubic splines are widely used in robotics, velocity and acceleration ripples in the first & last knots can worsen manipulator trajectory. The second phase includes changing cubic spline interpolation in the first and last knots of optimized trajectory with 7th order polynomial for having zero jerk at the beginning and end points of trajectory. Performing this modification eliminate undesired worsening in the trajectory and provide smoother start and stop of joint motions. Particle Swarm Optimization (PSO) is chosen as optimization algorithm because of its easy implementation and successful optimization performance. OTGA has been tested in simulation for PUMA robot and results are compared with algorithms proposed by earlier authors. In addition, a discrete-time PID control scheme for PUMA robot is designed for comparing energy consumption of OTGA with algorithms developed by previous authors. Comparison results illustrated that OTGA is the better trajectory generation algorithm than the others.     

基于书写力与字形信息的生物特征密钥生成

基于F-Tablet手写平台提出动态手写签名密钥生成方案,采用傅里叶变换提取特征,使用多态离散化算法生成稳定密钥,实现从动态手写签名到加密密钥的安全转换,并通过实验分析密钥生成方案的认证性能和安全性能.生成的密钥破译困难,随身携带,不会丢失被盗,不会增加用户的记忆负担,可用于身份认证、文件加密以及数字版权管理等领域.     

Dummy trajectory generation scheme based on generative adversarial networks

Neural Computing and Applications - Dummy trajectory is widely used to protect the privacy of mobile users’ locations. However, two main challenges remain: (1) Map background information has...     

Smooth time-optimal tool trajectory generation for CNC manufacturing systems

An optimization approach is proposed in this paper for generating smooth and time-optimal path constrained tool trajectory for Cartesian computer numerical control (CNC) manufacturing systems. The desired smooth time-optimal trajectory generation (STOTG) problem is formulated as a general optimal control problem. And axis jerk (derivative of acceleration with respect to time) constraints are introduced into this problem to remove discontinuities of the acceleration profiles. The desired smoothness of the trajectory can be accomplished by adjusting the values of jerk constraints. A control vector parameterization (CVP) method is applied to convert the optimal control problem into a nonlinear programming (NLP) problem which can be solved conveniently and effectively. The third derivative of the path parameter with respect to time (pseudo-jerk) and jerk act as optimization variables. The pseudo-jerk is approximated as piecewise constant, thus for at least second-order continuous parametric path, the resulted optimized trajectory with respect to time is also at least second-order continuous. Sequential quadratic programming (SQP) method is used to solve the NLP problem, through which numerical solution is obtained. Non-smooth (i.e. without considering jerk constraints) time-optimal trajectory generation (non-STOTG) problem is also considered in this paper for the purpose of comparison. Solutions of time-optimal trajectory generation (TOTG) problems for two test paths are performed to verify the effectiveness of the proposed approach.     

Joint trajectory generation for redundant robots in an environment with obstacles

Collision avoidance is an absolutely essential requirement for a robot to complete a task in an environment with obstacles. For kinematically redundant robots, collision avoidance can be achieved by making full use of the redundancy. In this article, the problem of determining collision-free joint space trajectories for redundant robots in an environment with multiple obstacles is considered, and the “command generator” approach is employed to generate such trajectories. In this approach, a nondifferentiable distance objective function is defined and is guaranteed to increase wherever possible along the trajectory through a vector in N(J), the null space of Jacobian matrix J. Algorithms that implement this nondifferentiable optimization problem are fully developed. It is shown that the proposed collision-free trajectory generation scheme is efficient and practical. Extensive simulation results of a four-link robot example are presented and analyzed.     

一种实时的三维语义地图生成方法

为了提高模块化机械臂分拣作业效率,研究了一种实时三维语义地图生成方法。该方法设计了一种改进的区域增长分割算法提高了分割效率和准确性,通过基于距离阈值的特征匹配方法得到候选模型,采用随机采样一致性（RANSAC）和迭代最近点算法（ICP）生成转变假设并对候选模型进行验证,获取物体位姿信息,保存于XML地图文件中,将其与机械臂末端位姿进行推理分析,得到抓取任务轨迹。实验结果表明,该方法满足作业实时性与准确性的要求。     

Axis-coupled trajectory generation for chains of integrators through smoothing splines

Integrator based model is used to describe a wide range of systems in robotics. In this paper, we present an axis-coupled trajectory generation algorithm for chains of integrators with an arbitrary order. Special notice has been given to problems with pre-existing nominal plans, which are common in robotic applications. It also handles various type of constraints that can be satisfied on an entire time interval, including non-convex ones which can be transformed into a series of convex constraints through time segmentation. The proposed approach results in a linearly constrained quadratic programming problem, which can be solved effectively with off-the-shelf solvers. A closed-form solution is achievable with only the boundary constraints considered. Finally, the proposed method is tested in real experiments using quadrotors which represent high-order integrator systems.     

A neuro-fuzzy approach to real-time trajectory generation for robotic rehabilitation

This paper proposes a method for the design of a real-time neuro-fuzzy trajectory generator for the robotic rehabilitation of patients with upper limb dysfunction due to neurological diseases. The primary objective of the methodology is to assist therapists by allowing them to delegate repetitive therapy tasks to a mechatronic system. The trajectory generator is packaged as a platform-independent solution to facilitate the rehabilitation of patients using multiple manipulator configurations. The system utilizes a fuzzy-logic schema to introduce compliance into the human–robot interaction, and to allow the emulation of a wide variety of therapy techniques. This approach also allows for the fine-tuning of patient specific behaviour using linguistic variables. The rule base for the system is trained using a fuzzy clustering algorithm and applied to the experimental data gathered during traditional therapy sessions. The compliance rule base is combined with a hybrid neuro-fuzzy compensator to automatically tune the dynamics of the robot–patient interaction. Preliminary results indicate that the approach can accurately reproduce a prescribed patient/therapist interaction, validating the proposed approach.     

Distributed trajectory generation for cooperative multi-arm robotsvia virtual force interactions

A trajectory generation method for multi-arm robots through cooperative and competitive interactions among multiple end-effecters is proposed. The method can generate the trajectories of the multiple arms in a distributed manner based on a concept of a virtual interaction force which represents an interaction between an end-effector and an environment. It is shown that the method is effective not only for simple cooperative tasks such as positioning a common object, but also for more complicated tasks including relative motions among arms.     

Smooth quadrotor trajectory generation for tracking a moving target in cluttered environments

In this paper,we present a trajectory generation method of a quadrotor,based on the optimal smoothing B-spline,for tracking a moving target with consideration o...     

Real-time bas-relief generation from a 3D mesh

Most of the existing approaches to bas-relief generation operate in image space, which is quite time-consuming in practice. This paper presents a different bas-relief generation algorithm based on geometric compression and starting from a 3D mesh input. The feature details are first extracted from the original objects using a spatial bilateral filtering technique. Then, a view-dependent coordinate mapping method is applied to build the height domain for the current view. After fitting the compression datum plane, the algorithm uses an adaptive compression function to scale and combine the Z values of the base mesh and the fine details. This approach offers control over the level of detail, making it flexible for the adjustment of the appearance of details. For a typical input mesh with 100 k triangles, this algorithm computes a bas-relief in 0.214 s.     

基于最小边界扇形的移动对象轨迹实时化简算法

为了对全球定位系统(GPS)设备采集到的移动对象原始轨迹数据进行简化,提高轨迹数据的使用效率,降低移动终端的通信代价和计算开销,提出了一种基于最小边界扇形(MBS)的移动对象轨迹实时化简算法。该算法不同于用一条折线来近似原始轨迹的方法,它利用扇形预测范围来估计、简化原始轨迹,在角度和距离两个层面上对简化误差进行控制。提出了新的误差度量方法--基于等极径的误差度量方法,并讨论了GPS定位误差对简化算法的影响。实验结果表明,所提算法的简化轨迹高效、稳定,所得到的简化轨迹与原始轨迹之间误差较小(不超过误差阈值的20%),对GPS定位误差有较好的容错能力。     

Dynamic modeling and CPG-based trajectory generation for a masticatory rehab robot

Human mastication is a complex and rhythmic biomechanical process which is regulated by a brain stem central pattern generator (CPG). Masticatory patterns, frequency and amplitude of mastication are different from person to person and significantly depend on food properties. The central nervous system controls the activity of muscles to produce smooth transitions between different movements. Therefore, to rehab human mandibular system, there is a real need to use the concept of CPG for development of a new methodology in jaw exercises and to help jaw movements recovery. This paper proposes a novel method for real-time trajectory generation of a mastication rehab robot. The proposed method combines several methods and concepts including kinematics, dynamics, trajectory generation and CPG. The purpose of this article is to provide a methodology to enable physiotherapists to perform the human jaw rehabilitation. In this paper, the robotic setup includes two Gough–Stewart platforms. The first platform is used as the rehab robot, while the second one is used to model the human jaw system. Once the modeling is completed, the second robot will be replaced by an actual patient for the selected physiotherapy. Gibbs–Appell’s formulation is used to obtain the dynamics equations of the rehab robot. Then, a method based on the Fourier series is employed to tune parameters of the CPG. It is shown that changes in leg lengths, due to the online changes of the mastication parameters, occur in a smooth and continuous manner. The key feature of the proposed method, when applied to human mastication, is its ability to adapt to the environment and change the chewing pattern in real-time parameters, such as amplitudes as well as jaw movements velocity during mastication.     

Minimum-time trajectory generation for constrained linear systems using flatness and B-splines

In this article, we discuss minimum-time trajectory generation for input-and-state constrained continuous-time LTI systems in the light of the notion of flatness and B-splines parametrisation. Flat systems have the useful property that the input and the state trajectories can be completely characterised by the (so-called) flat output. We propose a splines parametrisation for the flat output, and the corresponding parametrisations for the performance output, the states and the inputs. Using this parametrisation the problem of minimum-time constrained trajectory planning is cast into a feasibility-search problem in the splines control-point space, in which the constraint region is characterised by a polytope. A close approximation of the minimum-time trajectory is obtained by systematically searching the end-time that makes the constraint polytope to be minimally feasible.