Controlled passive dynamic running experiments with the ARL-monopod II

This paper presents the expansion and implementation of the controlled passive dynamic running (CPDR) strategy for legged robots, previously presented by the authors. The CPDR exploits the underlying passive dynamic operation of the robot's mechanical systems to reduce the energy spent for locomotion. Meanwhile, it ensures the stability of the vertical and forward motions as the robot speed varies. An "adaptive energy controller" stabilizes the hopping height accurately over a range of operating conditions. The passive dynamic derivations for the Monopod, together with the foot-placement algorithm and model-based joint controllers, are used to control the forward speed about the passive operation trajectories. New locomotion variables are used for robust synchronization between the hip-body and the leg oscillations. ARL-Monopod II achieved a speed of 1.25 m/s with specific resistance (a measure for energy cost of locomotion) of 30% of the earlier robot ARL-Monopod I, its predecessor, due to the newer hip and leg design and application of the CPDR control strategy.     

A Wheel-legged Robot with Active Waist Joint: Design,Analysis, and Experimental Results

This paper presents a wheel-legged robot that features an active waist joint. The proposed wheel-legged robot is composed of a front module, a rear module, and an active waist joint. The proposed robot can perform rectilinear motion and turning motion in both wheeled and legged modes. The active waist joint module is added to make the robot pass through the curved narrow channel. Several experiments have been done to evaluate the performance of the proposed wheel-legged robot. The maximum velocities of the proposed robot in wheeled and legged modes are 17.2 and 10.4 m/min respectively. And the average corresponding deflection rates of the proposed robot in wheeled and legged modes are 3.1 and 3.7 % respectively. The mobility efficiencies of the robot in wheeled and legged modes are up to 96.3 and 94.3 % respectively. Compared with the proposed robot in legged mode, the performance in the turning motion with the active waist joint is better when the proposed robot is in wheeled mode. Two approaches of climbing obstacles are proposed for the proposed robot in legged mode. The wheel-legged robot can climb an obstacle with maximum height of 10 cm.     

Design and Development of the Lifting and Propulsion Mechanism for a Biologically Inspired Water Runner Robot

This paper describes the design and development of a novel robot, which attempts to emulate the basilisk lizard's ability to run on the surface of water. Previous studies of the lizards themselves have characterized their means of staying afloat. The design of a biomimetic robot utilizing similar principles is discussed, modeled, and prototyped. Functionally, the robot uses a pair of identical four bar mechanisms, with a 180 ^deg phase shift to achieve locomotion on the water's surface. Simulations for determining robot lift and power requirements are presented. Through simulation and experimentation, parameters are varied with the focus being a maximization of the ratio of lift to power. Four legged robots were more easily stabilized, and had a higher lift-to-power ratio than two legged robots. Decreases in characteristic length and running speed, and increases in foot diameter and foot penetration depth all cause a higher lift to power ratio. Experimental lift approached 80 gr, and experimental performance exceeded 12 gr/W for four legged robots with circular feet. This work opens the door for legged robots to become ambulatory over both land and water, and represents a first step toward robots which run on the water instead of floating or swimming.     

Weaver: Hexapod robot for autonomous navigation on unstructured terrain

Legged robots are an efficient alternative for navigation in challenging terrain. In this paper we describe Weaver, a six‐legged robot that is designed to perform autonomous navigation in unstructured terrain. It uses stereo vision and proprioceptive sensing based terrain perception for adaptive control while using visual‐inertial odometry for autonomous waypoint‐based navigation. Terrain perception generates a minimal representation of the traversed environment in terms of roughness and step height. This reduces the complexity of the terrain model significantly, enabling the robot to feed back information about the environment into its controller. Furthermore, we combine exteroceptive and proprioceptive sensing to enhance the terrain perception capabilities, especially in situations in which the stereo camera is not able to generate an accurate representation of the environment. The adaptation approach described also exploits the unique properties of legged robots by adapting the virtual stiffness, stride frequency, and stride height. Weaver's unique leg design with five joints per leg improves locomotion on high gradient slopes, and this novel configuration is further analyzed. Using these approaches, we present an experimental evaluation of this fully self‐contained hexapod performing autonomous navigation on a multiterrain testbed and in outdoor terrain.     

电动并联六轮足机器人的运动驱动与多模态控制方法

提出一种并联六轮足移动机器人．该机器人设有多模式Stewart型腿结构,其负载能力大,集成了轮式运动和足式运动的优点,可实现足式、轮式、轮足复合式运动．首先,阐述了机器人设计思路,对电动并联六轮足机器人的硬件系统和控制系统进行设计．其次,针对足式运动模式,设计了一套完整的足式“三角”步态和稳定行走算法,该算法可降低足端与地面之间的垂直方向冲击,防止足式运动拖腿或打滑;针对轮式运动模式,设计并介绍了6轮协同控制和轮式协同转向原理;针对轮足复合式运动模式,介绍了变高度、变支撑面、变轮距、主动隔振控制原理,重点分析了主动隔振控制和变轮距控制,可实现主动隔振及姿态平稳控制,提高了机器人在崎岖颠簸地形下的轮足复合式运动的稳定性．最后,对电动并联六轮足机器人的足式、轮式、轮足复合式运动模式进行实验,实验结果验证了本文提出的并联六轮足移动机器人设计的可行性和各运动模式下驱动与控制算法的有效性．     

小型两栖仿龟机器人多模式运动研究

针对浅滩环境和水下狭窄空间的科研考察、资源勘探等任务,提出一种“腿－多矢量喷水”复合驱动的小型两栖仿龟机器人。通过研究“腿－多矢量喷水”复合式驱动系统的运动机理,设计仿生爬行步态和旋转步态。根据“腿－多矢量喷水”复合驱动机构的变结构特性,提出“H”、“工”和“X”等多模式运动。通过机器人水中运动学建模,建立基于实时动态推力矢量分配优化机制的水中3维自主运动控制方法。最后搭建机器人原型机,陆地上的多地形运动实验验证了机器人在非结构化浅滩环境中的适应能力强,水中运动控制实验验证了两栖机器人多模式运动控制的灵活性和可行性。     

Energy-preserving control of a passive one-legged running robot

Fast and energy-efficient control is an increasingly important and attractive area of research in legged locomotion. In this paper, we present a new simple controller for a planar one-legged passive running robot having a springy leg and a compliant hip joint. The most distinctive advantage of the controller over previously proposed ones is it does not require any pre-planned trajectories nor target dynamics. Instead, it utilizes exact non-linear dynamics. Our results are summarized as follows. First, we propose an energy-preserving control strategy for energy-efficient and autonomous gait generation. This strategy is successfully implemented as a new touchdown controller at the flight phase. Simulation results show that the robot can hop from a wide set of initial conditions. Moreover, the running gaits generated are found to be quasi-periodic orbits, which can be seen in Hamiltonian systems. Since the controlled running gaits exist for every admissible energy level, they have some robustness against disturbances. Next, it is shown that an adaptive control of the touchdown angle, which is similar to a delayed feedback controller for a chaotic system, can asymptotically stabilize these quasi-periodic gaits to the periodic ones of the desired period, with some limitations. In particular, for one-periodic gait, by using some additional adaptive controllers, the robot eventually hops without any control inputs. Since our energy-preserving strategy is clear and implementation of the controller is straightforward, we believe it can be easily applied to a wide class of legged mechanisms.     

A Highly-Maneuverable Demining Autonomous Robot: an Over-Actuated Design

Based on the well-known advantages of using an over-actuated mechanism for robots, this research proposes a holonomic highly-maneuverable autonomous robot design for demining service applications. The proposed approach provides an interesting compromise between the design requirements of the demining robot applications and the over-actuated autonomous robots. The robot body is mainly divided into two parts: the first part provides the robot with its required locomotion and it consists of a driving/steering subsystem with four driving wheels (4WD), four steering mechanisms (4SW), and a passive suspension subsystem. The second part is a manipulator with three degrees of freedom that is designed based on two parallelogram mechanisms. The proposed design insures many advantages over existing designs, including stability, maneuverability, autonomous navigation, and simplicity of the control effort constraints. The robot model and its corresponding stability analysis were conducted and simulated in order to evaluate the motion of the robot over different environments rough terrains and slanted surfaces. Moreover, a prototype of the proposed robot was developed and built and different types of sensors were used in order to help it take precise actuation decisions for navigation and control. The prototype was experimentally tested for different scenarios and environments in order to validate the proposed design. The testing results demonstrated decent performance of the robot in autonomous navigation and in localizing the detected objects.     

一种输电线路巡检机器人控制系统的设计与实现

介绍了一种超高压输电线路巡检机器人控制系统的设计与实现方法．根据巡检作业任务的要求，采用遥控与局部自主相结合的控制模式实现巡检机器人沿线行走及跨越障碍．设计了巡检机器人有限状态机模型，实现了机器人遥控与局部自主控制的有机结合．采用基于激光传感器定位的方法实现了巡检机器人的自主越障控制．实验结果表明，该机器人可实现沿线行走及自主跨越障碍，从而验证了控制系统设计的有效性与合理性．     

Power Consumption Optimization for a Hexapod Walking Robot

Power consumption is one of the main operational restrictions on autonomous walking robots. In this paper, an energy efficiency analysis is performed for a hexapod walking robot to reduce these energy costs. To meet the power-saving demands of legged robots, the torque distribution algorithm required to minimize the system’s energy costs was established with an energy-consumption model formulated. In contrast to the force distribution method, where the objective function is related to the tip-point force components, the torque distribution scheme is based on minimization of the mechanical energy cost and heat loss power. The simulation results show that this scheme could reduce the system energy costs with use of the appropriate walking velocities and duty factors for the robot. The paper also discusses the effects of the gait patterns and the mechanical structure on the system energy costs. For this purpose, the prescribed periodic walking gait of the robot is described in terms of several parameters, including the duty factor, the stride length, the body height, and the foot trajectory lateral offset. The numerical results indicate some analogies between the characteristics of the simulated walking robot and those of animals in nature. The optimized parameters derived here are intended for robot platform development applications.     

基于Mindstorms的四轮智能机器人实时控制系统设计

传统机器人控制系统是以辅助控制机器人转向为基准进行设计的,存在转向控制效果差的问题,为实现四轮智能机器人控制系统研发,以Mindstorms平台为基础,搭建由主控模块、传感器模块、无线通信模块、运动模块以及电源模块组成的四轮智能机器人结构。在运动控制模块中选用TMC236芯片作为电机驱动芯片,通过电路为桥臂上开关管提供控制电压;在底层控制模块中,采用PID控制器控制电机期望转角与实际转角之间差值,实现机器人转向角度控制。对软件控制策略研发中,利用嵌入式操作软件系统实现车道保持控制和避障控制功能,实现机器人自主换道功能。保证机器人自主充电情况下,测试转向控制功能,由测试结果可知,基于Mindstorms系统控制效果始终维持在98%以上,实现机器人转向精准控制。     

From pixels to multi-robot decision-making: A study in uncertainty

Mobile robots must cope with uncertainty from many sources along the path from interpreting raw sensor inputs to behavior selection to execution of the resulting primitive actions. This article identifies several such sources and introduces methods for (i) reducing uncertainty and (ii) making decisions in the face of uncertainty. We present a complete vision-based robotic system that includes several algorithms for learning models that are useful and necessary for planning, and then place particular emphasis on the planning and decision-making capabilities of the robot. Specifically, we present models for autonomous color calibration, autonomous sensor and actuator modeling, and an adaptation of particle filtering for improved localization on legged robots. These contributions enable effective planning under uncertainty for robots engaged in goal-oriented behavior within a dynamic, collaborative and adversarial environment. Each of our algorithms is fully implemented and tested on a commercial off-the-shelf vision-based quadruped robot.     

旋翼飞行机器人研究进展

旋翼飞行机器人是面向空中自主作业需求,将旋翼飞行器与多自由度机械臂相结合所提出的新型机器人.该机器人作业过程中旋翼飞行器、机械臂与作业目标之间的动态相对运动以及与作业目标接触过程中未建模外力、力矩扰动使自主控制受到极大挑战.本文将针对旋翼飞行机器人的结构演变及关键技术、作业机构集成技术进行综述.从动力学建模及动力学特性分析、动态运动约束/力约束下的协调规划、非结构环境下的运动和作业控制、面向任务动态操作的环境感知、面向任务的实验系统构建与实验验证五个方面初步构建了旋翼飞行机器人自主作业理论体系.     

Quadruped robot trotting over irregular terrain assisted by stereo-vision

Legged robots have the potential to navigate in challenging terrain, and thus to exceed the mobility of wheeled vehicles. However, their control is more difficult as legged robots need to deal with foothold computation, leg trajectories and posture control in order to achieve successful navigation. In this paper, we present a new framework for the hydraulic quadruped robot HyQ, which performs goal-oriented navigation on unknown rough terrain using inertial measurement data and stereo-vision. This work uses our previously presented reactive controller framework with balancing control and extends it with visual feedback to enable closed-loop gait adjustment. On one hand, the camera images are used to keep the robot walking towards a visual target by correcting its heading angle if the robot deviates from it. On the other hand, the stereo camera is used to estimate the size of the obstacles on the ground plane and thus the terrain roughness. The locomotion controller then adjusts the step height and the velocity according to the size of the obstacles. This results in a robust and autonomous goal-oriented navigation over difficult terrain while subject to disturbances from the ground irregularities or external forces. Indoor and outdoor experiments with our quadruped robot show the effectiveness of this framework.     

An adaptive locomotion controller for a hexapod robot: CPG,kinematics and force feedback

Insects can perform versatile locomotion behaviors such as multiple gaits, adapting to different terrains, fast escaping, etc. However, most of the existing bio-inspired legged robots do not possess such walking ability, especially when they walk on irregular terrains. To tackle this challenge, a central pattern generator （CPG）-based locomotion control methodology is proposed, integrated with a contact force feedback function. In this approach, multiple gaits are produced by the CFG module. After passing through a post-processing circuit and a delay-line, the control signal is fed into six trajectory generators to generate predefined feet trajectories for the six legs. Then, force feedback is employed to adjust these trajectories so as to adapt the robot to rough terrains. Finally the regulated trajectories are sent to inverse kinematics modules such that the position control instructions are generated to control the actuators. In both simulations and real robot experiments, we consistently show that the robot can perform sophisticated walking patterns. What is more, the robot can use the force feedback mechanism to deal with the irregularity in rough terrain. With this mechanism, the stability and adaptability of the robot are enhanced. In conclusion, the CPG-base control is an effective approach for legged robots and the force feedback approach is able to improve walking ability of the robots, especially when they walk on irregular terrains.     

一种多足步行机器人行走状态分析模型

结合步行机器人行走的动力学特性,通过对机器人的加速度传感器信息进行离散傅立叶变换,建立了行走相关特征值的概率模型.通过使用马氏距离作为判定标准,对步行机器人的行走稳定性给出定量描述.四足步行机器人平台上的实验结果表明,该模型能够实时反映机器人的行走特性,帮助机器人在行走状态受环境影响发生改变时,根据行走特征及时调整运动,保证其稳定性.     

Watch out, Tiger Woods![golf playing robot]

This article describes the development of an autonomous robotic system for playing mini-golf. The system was designed and built to serve as a demonstration of robotic application for engineering students. The system was built using a Yasakawa robot fitted with two arms. The software was developed to control the machine using the C++ language. Standard C++ libraries were used in addition to communication libraries provided by the Yasakawa Corporation. The current configuration works with Microsoft Windows NT and an Ethernet environment. This article describes the hardware and software design aspects of this machine.     

A New Mechanism for Mesoscale Legged Locomotion in Compliant Tubular Environments

We present design and experimental performance results for a novel mechanism for robotic legged locomotion at the mesoscale (from hundreds of microns to tens of centimeters). The new mechanism is compact and strikes a balance between conflicting design objectives, exhibiting high foot forces and low power consumption. It enables a small robot to traverse a compliant, slippery, tubular environment, even while climbing against gravity. This mechanism is useful for many mesoscale locomotion tasks, including endoscopic capsule robot locomotion in the gastrointestinal tract. It has enabled fabrication of the first legged endoscopic capsule robot whose mechanical components match the dimensions of commercial pill cameras (11 mm diameter by 25 mm long). A novel slot-follower mechanism driven via lead screw enables the mechanical components of the capsule robot to be as small while simultaneously generating 0.63 N average propulsive force at each leg tip. In this paper, we describe kinematic and static analyses of the lead screw and slot-follower mechanisms, optimization of design parameters, and experimental design and tuning of a gait suitable for locomotion. A series of ex vivo experiments demonstrate capsule performance and ability to traverse the intestine in a manner suitable for inspection of the colon in a time period equivalent to standard colonoscopy.