全地形移动机器人轮－地几何接触角估计

研究全地形移动机器人在不平坦地形中轮－地几何接触角的实时估计问题. 本文以带有被动柔顺机构的六轮全地形移动机器人为对象, 抛弃轮－地接触点位于车轮支撑臂延长线上这一假设, 通过定义轮－地几何接触角 δ 来反映轮－地接触点在轮缘上位置的变化和地形不平坦给机器人运动带来的影响, 将机器人看成是一个串－并联多刚体系统, 基于速度闭链理论建立考虑地形不平坦和车轮滑移的机器人运动学模型, 并针对轮－地几何接触角 δ 难以直接测量的问题, 提出一种基于模型的卡尔曼滤波实时估计方法. 利用卡尔曼滤波对机器人内部传感器的测量值进行噪声处理, 基于机器人整体运动学模型对各个轮－地几何接触角进行实时估计, 物理实验数据的处理结果验证了本文方法的有效性, 从而为机器人运动学的精确计算和高质量的导航控制奠定了基础.     

Control of an articulated wheeled mobile robot in pipes

We propose a control method in which an articulated wheeled mobile robot moves inside straight, curved and branched pipes. This control method allows the articulated wheeled mobile robot to inspect a larger area. The articulated wheeled mobile robot comprises pitch and yaw joints is and propelled by active wheels attached to the robot. Via the proposed control method, the robot takes on two different shapes; one prevents the robot from slipping inside straight pipes and the other allows movement in a pipe that curves in any direction. The robot is controlled by a simplified model for the robot's joint angles. The joint angles of the robot are obtained by fitting to a continuous curve along the pipe path. In addition, the angular velocity of the robot's active wheels is determined by a simplified model. The effectiveness of the proposed the control method was demonstrated with a physical implementation of the robot, and the robot was able to move inside straight, curved and branched pipes.     

An active sensing strategy for contact location without tactile sensors using robot geometry and kinematics

In this study, we develop new techniques to sense contact locations and control robots in contact situations in order to enable articulated robotic systems to perform manipulations and grasping actions. Active sensing approaches are investigated by utilizing robot kinematics and geometry to improve upon existing sensing methods for contact. Compliant motion control is used so that a robot can actively search for and localize the desired contact location. Robot control in a contact situation is improved by the precise estimation of the contact location. From this viewpoint, we investigate a new control strategy to accommodate the proposed sensing techniques in contact situations. The proposed estimation algorithm and the control strategy both work complementarily. Then, we verify the proposed algorithm through experiments using 7-DOF hardware and a simulation environment. The two major contributions of the proposed active sensing strategy are the estimation algorithm for contact location without any tactile sensors, and the control strategy complementing the proposed estimation algorithm.     

基于地面力学的月球车爬坡轮—地相互作用模型

月球车爬坡地面力学模型在月球车的设计、越障性能评价、控制和仿真等方面具有极其重要作用．利 用月球车轮地相互作用测试系统进行车轮爬坡性能实验,结合实验数据在传统车轮—土壤相互作用应力分布模型之 上推导出爬坡轮—地相互作用模型,同时考虑爬坡角度对浅层月壤应力分布的影响,提出了随滑转率变化的沉陷 因数经验公式,来反映月壤压实、刮带、侧向流动等引起的滑转沉陷．通过对应力分布公式进行积分转化得到集中 力／力矩计算模型,利用ADAMS 二次开发的柔性爬坡仿真环境并结合实验数据进行模型验证．在斜坡角度为16±, 载荷为100 N,当滑转率从0 增加到0.6 时,将模型的车轮斜坡法向载荷、挂钩牵引力和驱动力矩的计算值与实验数 据相对比,结果相对误差不超过10%,因而该爬坡模型可以有效地用于月球车轮地相互作用的力学计算．     

星球车松软星壤的轮腿式探测系统:Ⅱ-感知车轮

为增强星球车松软星壤的穿越通过能力,提出了轮壤交互接触信息的感知车轮设计。该车轮是一种星球车的前置轮腿式探测系统(WOLS)的关键部分,可实现动态轮壤交互的关键量测量(轮壤作用力/力矩、轮壤接触角和车轮沉陷量)。研究分析了轮壤力学的关键测量参量及其分组,完成了感知车轮的硬件设计和集成,提出了待测参数的在线测量模型和方法,通过标定校准和实车测试验证了该感知车轮的性能。     

A single wheel, gyroscopically stabilized robot

The authors have developed a unique, single-wheel robot that exploits gyroscopic forces for steering and stability. Experiments with two working models show promise for the concept for high-speed, rough-terrain and amphibious applications     

Reconfiguration Planning for a Robotic Vehicle with Actively Articulated Suspension in Obstacle Terrain during Straight Motion

In this paper, an actively articulated suspension (AAS) reconfiguration method is proposed for a robotic vehicle with AAS to negotiate an obstacle during straight motion. Proposed method includes AAS locomotion for the locomotion with the AAS and a calculation method that is independent to the terrain model for posture control using the AAS reconfiguration. Using simulations, it was verified that the proposed method can reconfigure the AAS for a robotic vehicle to have the desired position and posture to negotiate an obstacle. The errors of height and orientation can be reduced while wheel driving on rough terrain. Also, the robot can maintain a minimum static stability angle over 0.6?rad. When observing the obstacle negotiation procedure using the AAS reconfiguration including the proposed locomotion, it was found that the robot can conduct a high-level command successfully using the proposed method. The robot can negotiate an obstacle with a height of 71% of its usable length and can maintain the minimum static stability over 0.3?rad. Also, the robot can manage terrain uncertainty using the proposed AAS reconfiguration method.     

Design of a stable fuzzy controller for an articulated vehicle

This paper presents a backward movement control of an articulated vehicle via a model-based fuzzy control technique. A nonlinear dynamic model of the articulated vehicle is represented by a Takagi-Sugeno fuzzy model. The concept of parallel distributed compensation is employed to design a fuzzy controller from the Takagi-Sugeno fuzzy model of the articulated vehicle. Stability of the designed fuzzy control system is guaranteed via Lyapunov approach. The stability conditions are characterized in terms of linear matrix inequalities since the stability analysis is reduced to a problem of finding a common Lyapunov function for a set of Lyapunov inequalities. Simulation results and experimental results show that the designed fuzzy controller effectively achieves the backward movement control of the articulated vehicle.     

Design and field testing of a rover with an actively articulated suspension system in a Mars analog terrain

This study presents the electromechanical design, the control approach, and the results of a field test campaign with the hybrid wheeled‐leg rover SherpaTT. The rover ranges in the 150 kg class and features an actively articulated suspension system comprising four legs with actively driven and steered wheels at each leg’s end. Five active degrees of freedom are present in each of the legs, resulting in 20 active degrees of freedom for the complete locomotion system. The control approach is based on force measurements at each wheel mounting point and roll–pitch measurements of the rover’s main body, allowing active adaption to sloping terrain, active shifting of the center of gravity within the rover’s support polygon, active roll–pitch influencing, and body‐ground clearance control. Exteroceptive sensors such as camera or laser range finder are not required for ground adaption. A purely reactive approach is used, rendering a planning algorithm for stability control or force distribution unnecessary and thus simplifying the control efforts. The control approach was tested within a 4‐week field deployment in the desert of Utah. The results presented in this paper substantiate the feasibility of the chosen approach: The main power requirement for locomotion is from the drive system, active adaption only plays a minor role in power consumption. Active force distribution between the wheels is successful in different footprints and terrain types and is not influenced by controlling the body’s roll–pitch angle in parallel to the force control. Slope‐climbing capabilities of the system were successfully tested in slopes of up to 28° inclination, covered with loose soil and duricrust. The main contribution of this study is the experimental validation of the actively articulated suspension of SherpaTT in conjunction with a reactive control approach. Consequently, hardware and software design as well as experimentation are part of this study.     

Walking and steering control for a 3D biped robot considering ground contact and stability

This paper presents a stable walking control method for a 3D bipedal robot with 14 joint actuators. The overall control law consists of a ZMP (zero moment point) controller, a swing ankle rotation controller and a partial joint angles controller. The ZMP controller guarantees that the stance foot remains in flat contact with the ground. The swing ankle rotation controller ensures a flat foot impact at the end of the swinging phase. Each of these controllers creates 2 constraints on joint accelerations. As a consequence, the partial joint angles controller is implemented to track only 10 independent outputs. These outputs are defined as a linear combination of the 14 joint angles. The most important question addressed in this paper is how this linear combination can be defined in order to ensure walking stability. The stability of the walking gait under closed loop control is evaluated with the linearization of the restricted Poincare map of the hybrid zero dynamics. As a result, the robot can achieve an asymptotically stable and periodic walking along a straight line. Finally, another feedback controller is supplemented to adjust the walking direction of the robot and some examples of the robot steered to walk along different paths with mild curvature are given.     

A novel integrated control framework of AFS,ASS, and DYC based on ideal roll angle to improve vehicle stability

The current research on vehicle stability control mainly focuses on following the ideal yaw rate and sideslip angle, without considering the potential of ideal roll angle in improving the vehicle stability. In addition, the mutation of tire-road friction coefficient promotes a great challenge to the stability control. To improve the vehicle stability, in this study, firstly, the three-dimensional stability region of “lateral speed-yaw rate-roll angle” was studied, and a method to determine the ideal roll angle was proposed. Secondly, a novel integrated control framework of AFS, ASS, and DYC based on ideal roll angle was proposed to actively control the front tire slip angles, suspension forces, and motor torques: In the upper-level controller, model predictive control and tire force distribution algorithm were used to obtain the optimal four-tire longitudinal forces, front tire lateral forces and additional roll moment under constraints; In the lower-level controller, the upper virtual target was realized by the optimal allocation algorithm of actuators and the tire slip controller. Finally, the proposed control framework was verified on the varied-µ road. The results indicated that compared with the two existing control strategies, the proposed framework can significantly improve the vehicle following performance and stability.     

星球车松软星壤的轮腿式探测系统: Ⅰ-概念设计

为提高星球车在松软星表的穿越通过能力和危险探测能力,提出了一种前置轮腿式探测系统(WOLS)概念设计,以期能够用于轮壤相互作用的接触探测。提出了面向松软星表穿越的星球车WOLS概念设计和功能需求,建立了WOLS机构的运动学和力传递分析模型,并用于指导机构尺寸参数的优化设计。最后,实车测试验证了不同工况WOLS的设计目标和功能实现。     

Hybrid Control Scheme for Robust Tracking of Two-Link Flexible Manipulator

The hybrid control scheme is proposed to stabilize the vibration of a two-link flexible manipulator while the robustness of Variable Structure Control (VSC) developed for rigid manipulators is maintained for controlling the joint angles. The VSC law alone, which is designed to accomplish only the asymptotic decoupled joint angle trajectory tracking, does not guarantee the stability of the flexible mode dynamics of the links. In order to actively suppress the flexible link vibrations, hybrid trajectories for the VSC are generated using the virtual control force concept, so that robust tracking control of the flexible-link manipulator can also be accomplished. Simulation results confirm that the proposed hybrid control scheme can achieve more robust tracking control of two-link flexible manipulator than the conventional control scheme in the presence of payload uncertainty.     

Hybrid Control Scheme for Robust Tracking of Two-Link Flexible Manipulator

A hybrid control scheme is proposed to stabilize the vibration of a two-link flexible manipulator while robustness of Variable Structure Control (VSC) developed for rigid manipulators is maintained for controlling the joint angles. The VSC law alone, which is designed to accomplish only the asymptotic decoupled joint angle trajectory tracking, does not guarantee the stability of the flexible mode dynamics of the links. In order to actively suppress the flexible link vibrations, hybrid trajectories for the VSC are generated using the virtual control force concept, so that robust tracking control of the flexible-link manipulator can also be accomplished. Simulation results confirm that the proposed hybrid control scheme can achieve more robust tracking control of two-link flexible manipulator than the conventional control scheme in the presence of payload uncertainty.     

Control of constrained manipulators with flexible joints

This paper presents results on control design of constrained manipulators with flexible joints. It will be assumed that such manipulators are under gravity and contact reaction effects. It is also assumed that measurable joint variables are limited to rotor angles and its velocities. A simple biased proportional and derivative feedback controller is shown to be able to drive the manipulator to a desired configuration specified in link angles with desired contact force specified in the direction normal to the constraint surface at the desired position. A sufficient condition for global stability will be established by using a Lyapunov function which is constructed taking into account the spring stiffness, gravity factors and constraint functions. An example is studied and computer simulation results are presented to show closed-loop performance. Editor: M. Corless     

关节式移动机器人在斜面上基于模糊逻辑的运动控制

本文针对关节式移动机器人在斜面上运动时稳定性和安全性的要求对其进行动力学分析 ,利用传感器融合技术对机器人进行局部定位 ,提出了它的基于模糊逻辑的控制策略 .实验证明这种方法是可行的和有效的     

线控转向系统全状态反馈控制策略的研究

为了根据车况和驾驶员喜好实现最优的操纵特性(不足转向、过度转向和中性转向),需要主动控制前轮转角.线控转向系统利用车辆全状态(横摆角速度和质心侧偏角)反馈控制策略优化驾驶员的转向输入,主动控制前轮转角来优化车辆的转向特性,高速时具有适当的不足转向特性,低速时具有适当的过度转向特性,从而在反应快速和安全性之间很好的权衡.其中通过状态观测器估计侧偏角.结果表明,在紧急操纵时可以代替驾驶员协调使车辆保持稳定,正常操纵时补偿物理参数或操纵条件的变化而保持操纵特性的一致.     

Online terrain parameter estimation for wheeled mobile robots with application to planetary rovers

Future planetary exploration missions will require wheeled mobile robots ("rovers") to traverse very rough terrain with limited human supervision. Wheel-terrain interaction plays a critical role in rough-terrain mobility. In this paper, an online estimation method that identifies key terrain parameters using on-board robot sensors is presented. These parameters can be used for traversability prediction or in a traction control algorithm to improve robot mobility and to plan safe action plans for autonomous systems. Terrain parameters are also valuable indicators of planetary surface soil composition. The algorithm relies on a simplified form of classical terramechanics equations and uses a linear-least squares method to compute terrain parameters in real time. Simulation and experimental results show that the terrain estimation algorithm can accurately and efficiently identify key terrain parameters for various soil types.     

Articulated Figure Positioning by Multiple Constraints

A problem that arises in positioning an articulated figure is the solution of 3D joint positions (kinematics) when goal positions, rather than joint angles, are given. If more than one such goal is o be achived, tge problem is often solved interactively by positioning or solving one component of the linkage, then adjusting another, then redoing the first, and so on. This iterative process us skiw abd tedious. We present a method that automatically solves multiple simultaneous joint position goals. The user interface offers a six-degree-of-freedom input device to specify joint angles and goal positions interactively. Examplesare used to demonstrate the power and efficiency of this method for keypositon animation.     

Linear Time Stable PD Controllers for Physics-based Character Animation

In physics-based character animation, Proportional-Derivative (PD) controllers are commonly used for tracking reference motions in motor control tasks. Stable PD (SPD) controllers significantly improve the numerical stability of traditional PD controllers and support large gains and large integration time steps during simulation [TLT11]. For an articulated rigid body system with n degrees of freedom, all SPD implementations to date, however, use an O(n³) dense matrix factorization based method. In this paper, we propose a linear time algorithm for SPD computation, which is based on Featherstone's forward dynamics formulation for articulated rigid body systems in generalized coordinates [Fea14]. We demonstrate the performance advantage of our algorithm by comparing with both the conventional dense matrix factorization based method and an alternative sparse matrix factorization based method. We show that the proposed algorithm provides superior stability when controlling complex models at large time steps. We further demonstrate that our algorithm can improve the learning speed and quality of a Deep Reinforcement Learning (DRL) system for physics-based character animation.